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15 September 2021, Volume 44 Issue 9 Previous Issue   
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SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS
Ambient pressure X-ray absorption spectroscopy at ME2-BL02B of SSRF and its application in catalysis
Wei WANG,Xiaobao LI,Zheng PENG,Nian ZHANG,Hui ZHANG,Zhi LIU
Nuclear Techniques. 2021, 44 (9):  90101-090101.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090101
Abstract ( 31 )   HTML ( 0 )   PDF(pc) (1787KB) ( 74 )   Save
Background

The traditional soft X-ray absorption spectroscopy (XAS) method can only work under ultra-high vacuum conditions and cannot be used to detect changes in the electronic structure of samples under real conditions. However, the in-situ soft X-ray absorption spectroscopy method developed in the past decade is mainly based on the fluorescence yield mode. The lack of surface sensitive electron yield mode XAS, especially the Auger electron yield mode, hinders effective detection of chemical information and electronic structure changes on the surface.

Purpose

This study aims to investigate the near-ambient pressure X-ray absorption spectroscopy method and the chemical information of the sample surface in the real state.

Methods

By constructing the communication between electron energy spectrometer and the monochromator, the near-atmospheric soft X-ray absorption spectroscopy setup and method were developed at the ME2-BL02B terminal station of Shanghai Synchrotron Radiation Facility (SSRF) different modes of X-ray absorption spectrum under in-situ conditions could be measured in this terminal station, including total electron yield, partial electron yield, and Auger electron yield mode. With the help of in-situ method, the dynamic surface changes of materials at different depths could be described, and platinum-titanium dioxide catalyst for CO oxidation was selected as an example.

Results

The in-situ ambient pressure X-ray absorption spectroscopy of the electron yield mode recently developed at the ME2-BL02B terminal of SSRF is successfully applied to investigating the catalyst surface under real conditions, and experimental results show the superiority of the surface-sensitive XAS method.

Conclusions

The ambient pressure X-ray absorption spectroscopy method of this study can be used to approximate the chemical information changes of samples in real environments, thereby providing powerful tools for users in the fields of catalysis, environment and energy.

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Screening of safe dietary restriction therapy based on synchronous X-ray fluorescence microscopy
Rui SUN,Qinglong YAN,Jichao ZHANG,Qi ZHANG,Yu ZHANG,Ying ZHU
Nuclear Techniques. 2021, 44 (9):  90102-090102.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090102
Abstract ( 20 )   HTML ( 2 )   PDF(pc) (1348KB) ( 19 )   Save
Background

Dietary restriction therapy is one of the new methods of tumor treatment following surgery, radiotherapy and chemotherapy, and it plays an important role in the treatment of various tumors. However, there are no studies on the safety of this therapy.

Purpose

This study aims to evaluate the effect of dietary restriction therapy on the body and to screen a safe dietary restriction therapy.

Method

First of all, twenty mice were used for 45 days of food intake testing after 1 week of adaptive feeding. Secondly, sixty mice were randomly divided into 4 groups, one was taken Ad-libitum fed (AL) and 3 groups were treated by three dietary restrictions, i.e., 50% daily dietary restriction (DR), alternate-day fasting (ADF), alternate-day 50% dietary restriction (ADR). Daily food intake of normal mice was checked and the effects of three dietary restrictions on weight and survival time were evaluated. The liver and kidney function was tested on the collected serums of these mice to screen out the optimal dietary restriction scheme. Then, synchrotron-based hard X-ray fluorescence microscopy was used to test the biodistribution of several trace elements in liver and kidney for the safety evaluation of the optimal dietary restriction scheme. Haematoxylin and eosin (H&E) staining was employed to test whether the organs and tissues had lesions.

Results

Experimental results show that the average daily food intake of the mice is 0.2 g per gram of body weight. The body weight of the mice treated with 50% daily dietary restriction decreases linearly, and the survival time is significantly shortened; alternate-day fasting results in significant weight loss, shortened survival time and abnormal liver and kidney function whilst alternate-day 50% dietary restriction has no significant changes in body weight, survival time, liver and kidney function, and the biodistribution of trace elements in liver and kidney, and the pathology of major organs.

Conclusion

A safe dietary restriction scheme developed in this study will provide theoretical and experimental basis for the adjuvant treatment of malignant tumors with dietary restriction therapy.

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Precise measurement and application of synchrotron tune at storage ring
Yimei ZHOU,Xingyi XU,Yongbin LENG
Nuclear Techniques. 2021, 44 (9):  90103-090103.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090103
Abstract ( 17 )   HTML ( 1 )   PDF(pc) (1170KB) ( 7 )   Save
Background

The precise measurement of the synchrotron tune is of great significance for the study of beam longitudinal dynamics and the improvement of beam stability. In 2020, a bunch-by-bunch 3D position diagnosis system to measure the transverse position and longitudinal phase was built at Shanghai Synchrotron Radiation Facility (SSRF), it can also be used to monitor synchrotron tunes in real time. Compared with the traditional measurement method, the advantage of this method is that it does not need to modulate the RF cavity pressure.

Purpose

This study aims to achieve high-precision measurement of synchrotron tune in the normal operating mode without disturbing the user's experiments.

Methods

The phase oscillation of the refilled charge during the injection transient was extracted to effectively remove the interference of the RF system and the crosstalk between bunches. Correlation coefficient was used to obtain the bunch phase refilled with charge. Then, multiple longitudinal parameters, including the synchrotron tune, were fitted by mathematical model.

Results

The measurement results show that the synchrotron tune of SSRF is 0.007 3, and the fitting accuracy is 95%. The momentum compaction factor of storage ring directly calculated by the formula is 4×10-4.

Conclusions

The bunch-by-bunch 3D position diagnosis system and refilled charge extraction algorithm provide a favorable tool for realizing high-precision measurement of synchrotron tune.

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ACCELERATOR, RAY TECHNOLOGY AND APPLICATIONS
Data processing error accumulation of accelerator alignment control network
Xiaolong WANG,Ling KANG,Lan DONG,Bo LI,Lingling MEN,Tao LUO,Tong WANG,Jing LIANG,Zhenqiang HE,Zhiyong KE,Na MA,Shang LU,Yuanying HAN,Luping YAN,Luyan ZHANG,Xiaoyang LIU,Haoyue YAN,Chunhua LI,Lei WU,Jianxin SHEN,Xiaohui ZHANG
Nuclear Techniques. 2021, 44 (9):  90201-090201.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090201
Abstract ( 15 )   HTML ( 0 )   PDF(pc) (1253KB) ( 28 )   Save
Background

Compared with 2D+1D adjustment, three dimensional adjustment has a more rigorous theoretical basis. However, when the unconstrained three dimensional adjustment is applied to the observation values processing of the accelerator alignment control network, serious error accumulation will occur and resulting in obvious distortion of the results.

Purpose

This study aims to expound the ways and characteristics of three dimensional adjustment error accumulation for accelerator alignment control network.

Methods

Firstly, based on the layout of accelerator alignment control network and the moving station measurement method of laser tracker, the three dimensional adjustment mathematical model was analyzed, and the least-squares collocation theory was used to clearly explain the error propagation. Secondly, the characters of laser tracker measurement accuracy, station positioning and orientation accuracy and single station measurement error propagation were studied by analyzing the laser tracker 3D coordinate measurement model, measurement point error model and simulation measurement experiments. Finally, adjustment calculation of the linac control network was verified by simulation measurement, and two error accumulation suppression methods were tested.

Results

The source and propagation mode of error accumulation are explained theoretically, and verified by simulation calculation, so are the serious error accumulation of elevation and lateral errors in three dimensional adjustment of control network in accelerator.

Conclusions

Providing high-precision point coordinate constraint for three dimensional adjustment can effectively suppress error accumulation, and providing high-precision orientation constraint for station coordinate system can also achieve the effect of suppressing error accumulation.

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Crosstalk correction for determination of gross alpha and beta radioactivities in drinking water using a low background scintillation counter
Pin OU,Xueting ZHENG,Minyu TAN,Lifang HUANG,Yucheng LI
Nuclear Techniques. 2021, 44 (9):  90202-090202.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090202
Abstract ( 30 )   HTML ( 5 )   PDF(pc) (585KB) ( 46 )   Save
Background

There is α-β crosstalk in determination of gross α and β radioactivities in drinking water using a low background scintillation counter, which may lead to erroneous measurement results.

Purpose

This study aims to reduce the α-β crosstalk in the determination of gross α and β radioactivities on a low background scintillation counter.

Methods

First of all, α-β crosstalk correction factors for α (241Am) and β (90Sr-90Y) planar sources were determined on a typical scintillator with low background α/β measuring instrument--BH1227, to ascertain the particles or rays causing the α-β crosstalk. Then, α-β crosstalk correction factors for α and β standard sources with different areas and thicknesses were measured by the BH1227 to explore the relationship between the crosstalk correction factors and the areas and thicknesses of α and β standard sources. The gross α and β radioactivities of drinking water samples with different α or β radioactivity levels were measured and corrected by the BH1227, and the crosstalk correction factors obtained from the α and β standard sources, respectively. Finally, comparisons of the gross α and β radioactivities without and with the crosstalk corrections in drinking water samples were performed to verify the crosstalk correction.

Results

It is shown that, while pulses arising from alpha particles can get into β channel, the opposite is not typically done. With the increasing of thicknesses of the α standard sources, the α-to-β crosstalk correction factors increase first and then tend to be stable, but have no relation with their areas. The β-to-α crosstalk correction factor for the β standard sources is zero. The correction with the α-to-β crosstalk correction factors obtained from α standard sources, which have the same thickness and area as sample sources, minimizes the α-to-β crosstalk in gross β radioactivity measurement for drinking water samples. The determination of gross α radioactivity in the drinking water samples is not affected by the β-to-α crosstalk.

Conclusions

The pulses caused by β particles or X-γ rays, which can get into α channel lead to erroneous counting, can be effectively rejected by a reasonable increase of α threshold. The α-to-β crosstalk can be effectively reduce with properly adjusting the upper and lower thresholds of β channel to make the α-to-β crosstalk factor as small as possible and performing the α-to-β crosstalk correction on the β count.

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NUCLEAR ELECTRONICS AND INSTRUMENTATION
Development of high energy and high flux argon ion gun
Meiqiang ZHU,Xiaoqian SHI,Wa TANG,Weijie DENG,Fangzhun GUO
Nuclear Techniques. 2021, 44 (9):  90401-090401.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090401
Abstract ( 42 )   HTML ( 3 )   PDF(pc) (1432KB) ( 110 )   Save
Background

Large size aspherical mirrors have been widely used in space communication systems because of their high angular resolution and energy harvesting ability.

Purpose

This study aims to develop a high energy and high flux argon (Ar) ion gun for the rapid polishing of modified silicon layer on the surface of large size SiC aspherical mirror.

Methods

First of all, Ar ionization was realized by filament and anode grid. Ar+ energy was determined by anode voltage whilst the extractor and electrostatic lenses were employed to achieve Ar+ emission and focusing. The high transmittance of argon ions was realized by adjusting the voltage between the filament and the anode grid to maximize the ionization rate, and adjusting the size and relative position of the electrostatic focusing lens. The materials in the Ar ion gun were selected not only suitable for ultra-high vacuum, but also preventing from vacuum discharge. Then, the parameters of the main components of argon ion gun were determined by theoretical calculation and simulation of the trajectory of argon ion beam. Finally, preliminary experimental tests were carried out to verify its performance.

Results

The test results show that the Ar+ energy and beam flux can reach 20 keV and 50 μA, respectively, at 30 mm working distance and Ar partial pressure of 1.2×10-2 Pa. The beam size can be continuously adjusted from 19 mm to 24 mm.

Conclusions

This developed argon ion gun with small size, high energy and high flux, can be installed on a vacuum multi-dimensional displacement table for a wide range of movement to achieve high vacuum surface polishing of large aperture optical elements.

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Study on self-absorption corrections of γ spectrum for volume samples
Lei ZHANG
Nuclear Techniques. 2021, 44 (9):  90402-090402.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090402
Abstract ( 30 )   HTML ( 1 )   PDF(pc) (674KB) ( 36 )   Save
Background

In radiation environmental quality measurement or emergency measurement, most samples have different media composition, and the laboratory standard sources are limited.

Purpose

This study aims to improve the analysis accuracy of different samples by self-absorption correction of the samples.

Methods

Four different self-absorption correction methods, were used to test and analyze soil samples containing different nuclides to calculate the self-absorption correction of volume samples. The geometric dimension of samples was the same as the standard solid point source ?75 mm×70 mm. The point detector correction method, the mean effective length correction method and the vertical incident correction method were employed to simplify the detector, the sample box and the incident angle, respectively, whilst the Monte Carlo correction method was closest to the actual situation of the γ-ray near-incidence detector in the sample.

Results

The Monte Carlo correction method has the least deviation for low energy nuclides which is within ±8% between the correction results and true values, better than that of mean effective length method. The point detector correction method, the vertical incidence correction method, and the mean effective length correction method have small deviation for middle and high energy nuclides, but the deviations of these three methods for low-energy nuclides are large.

Conclusions

The Monte Carlo self-absorption correction method can be used as an accurate correction for the self-absorption of low-energy nuclides. If the composition of the medium in the sample is unknown, the mean effective length method can be used to calibrate the self-absorption of the measured nuclides in the middle and high energy parts. The vertical incidence method and point detector method are also suitable for self-absorption correction of the middle and high energy parts. The relative deviation between the correction results and true values is within ±8% in the low-energy part, which is better than the mean effective length method.

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Time constant of double exponential signal for X-ray energy spectrum detector
Longjun CHENG,Bohua YIN,Botong SUN,Guanglu XU,Wenbo WANG,Li HAN
Nuclear Techniques. 2021, 44 (9):  90403-090403.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090403
Abstract ( 23 )   HTML ( 2 )   PDF(pc) (1013KB) ( 59 )   Save
Background

In the X-ray energy spectrum measurement system, the time constant is an important factor affecting trapezoidal pulse shaping. Accurate measurement of the time constant of double exponential pulse signals is beneficial to obtaining a better trapezoidal pulse shaping.

Purpose

This study aims to propose a fast fitting double exponential pulse algorithm for measuring the time constant in trapezoidal pulse shaping.

Methods

First of all, the linear regression method based on the least square method was adopted to convert nonlinear fitting linear fitting. Then, functional expression of double exponential pulse signal was fitted by fast trapezoidal pulse shaping, and the feasibility of time constant measurement in trapezoidal forming by fast fitting double exponential algorithm was verified by MATLAB programming simulation. Finally, the practicability of the algorithm was evaluated by experimental pulse data of 55Fe radiation source received by X-ray silicon draft detector (SDD). Goodness-of-fit R2 of this algorithm was compared with that of cftool toolbox of MATLAB on both the simulation data and experimental data.

Results

The goodness of fit R2 of proposed algorithm exceeds 0.95 for both the simulated signal with 5% standard deviation noise and the shaped pulse signal of experiments. When the goodness of fit exceeds 0.95, the running speed of this algorithm is 2 orders of magnitude faster than that in cftool toolbox of MATLAB.

Conclusions

The algorithm of this paper possesses high fitting degree, fast calculation time, hence suitable for real-time measurement of time constant of double exponential pulse signal in embedded system.

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NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH
Radiation and shielding design on the simplified experimental muon source at CSNS
Gang ZHANG,Hantao JING,Donghui ZHU,Luping ZHOU,Yukai CHEN,Qili MU,Qingbiao WU
Nuclear Techniques. 2021, 44 (9):  90501-090501.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090501
Abstract ( 14 )   HTML ( 0 )   PDF(pc) (2591KB) ( 33 )   Save
Background

China Spallation Neutron Source (CSNS) based on the spallation reaction is a large multidisciplinary research facility, which has been constructed and commissioned since August 2018. Experimental Muon Source (EMuS) is one of the important research platforms for the future construction of CSNS. The proton beam energy is 1.6 GeV and the power on the carbon target is 20 kW.

Purpose

This study aim to design radiation and shielding system for EMuS that satisfies the requirements of radiation safety.

Methods

The Monte Carlo simulator of FLUKA was used to calculate and analyze the prompt radiation and residual radiation. According to the dose limit, the shielding optimization design was carried out, and abandoned proton beam flux was estimated. Finally, computational results of FLUKA were analyzed, and compared with that of the Moyer mode semi-empirical formula.

Results

The simulation results show that the exterior residual radiations of shielding for the high radiation area such as target area, collimation area, dump and muon transport line are very low whilst the inside components such as carbon target, magnets, and vacuum pipes of high-energy proton transport line are critically activated and have high residual radiation. The abandoned proton beam after carbon target is of 1012 cm-2?s-1.

Conclusions

The optimal shielding design meets the requirements of prompt radiation protection for EMuS of CSNS, but the strategy of remote operations and strict control of maintenance time need to consider for the future maintenance and upgrade. Abandoned proton beam can be efficiently utilized to build a proton irradiation platform and a neutron irradiation platform with carefully studying of the background of those irradiation points.

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Decontamination characteristics of the low temperature detergent for simulated U(VI) pollution
Yu XIE,Xiaoyan LIN,Xunhai PAN,Xinrui XU,Hailing XI
Nuclear Techniques. 2021, 44 (9):  90502-090502.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090502
Abstract ( 17 )   HTML ( 1 )   PDF(pc) (1646KB) ( 22 )   Save
Background

The research of low temperature detergent is of great significance for the operating and decommissioning of nuclear facilities at low temperature environment.

Purpose

This study aims to explore the fluid characteristics and decontamination characteristics of polyvinyl butyral detergent at low temperature.

Methods

The low temperature detergent was prepared by using polyvinyl butyral as solute, ethanol and ethyl acetate as solvent and citric acid as decontamination additives. The viscosity, fluidity, sprayability and wettability of the detergent on the surface of different materials were measured in experiment. Four simulated U(VI) contaminated plate samples were prepared by the dyeing of the uranyl nitrate solution on the base of glass, stainless steel, ceramic tile and alkyd paint, respectively. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the decontamination films on the surface of these four samples, and study the decontamination mechanism. Finally, the decontamination characteristics of the detergent for the simulated U(VI) pollution on surface of different materials were studied at low temperature, and the effects of temperature, detergent dosage and surface roughness on decontamination rate were discussed.

Results

Experimental results show that the decontamination rates of the detergent for the simulated U(VI) pollution on the surface of glass, stainless steel, ceramic tile and alkyd paint board are above 97.3%, 93.6%, 95.5% and 88.9%, respectively, in the temperature range of -15~10 ℃, that the temperature and the detergent dosage have little effect on the decontamination rate and that the decontamination film formed by the detergent have good strippability.

Conclusions

The detergent has a good application potential at the decontamination of radioactive pollution in low temperature environment.

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Research on terrain correction method of airborne γ spectrometry
Qiushi LIU,Qingxian ZHANG,Hai YANG,Shengqing XIONG,Liangquan GE,Hongfei XIAO,Maolin XIONG,Yaohui MI,Jian ZHANG,Rui CHEN
Nuclear Techniques. 2021, 44 (9):  90503-090503.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090503
Abstract ( 43 )   HTML ( 4 )   PDF(pc) (1426KB) ( 107 )   Save
Background

Airborne gamma spectrometer is a method to measure ground gamma nuclide activity (specific activity) by installing gamma spectrometer on aircraft. The accuracy of results is affected by flight altitude and terrain fluctuation. At present, altitude correction has been applied to the quantitative analysis of airborne gamma spectrometer, but the correction effect of altitude correction on areas with large terrain fluctuation is not desirable.

Purpose

This study aims to propose a 3D terrain correction method based on discrete integral.

Methods

First of all, the basic characteristics of digital elevation model (DEM) and radiation field distribution were analyzed. Then, the effective detection area of airborne gamma spectrometer was divided into micro grid surface elements, and the contribution of micro elements to the counting rate of full energy peak of the airborne gamma spectrum was calculated. The terrain correction coefficient by discrete integral was realized by the terrain correction of airborne gamma spectrum measurement results, and the accuracy of airborne gamma spectrum measurement results was simultaneously improved. Finally, verification of this method was performed on the measured airborne gamma-ray spectrum data processing.

Results

Verification results show that the influence of terrain on gamma spectrum data is corrected effectively by the proposed method.

Conclusions

The 3D terrain correction method based on discrete integral can improve the consistency between airborne gamma spectrum measurement results and ground measurement results, and has the advantages of fast mesh division, altitude and terrain correction simultaneous.

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NUCLEAR ENERGY SCIENCE AND ENGINEERING
A CIPS risk evaluation methodology applicable for PWR
Shuqi MENG,Yisong HU,Changying LI,Tianming RUAN,Jiapeng LIAO
Nuclear Techniques. 2021, 44 (9):  90601-090601.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090601
Abstract ( 39 )   HTML ( 0 )   PDF(pc) (775KB) ( 38 )   Save
Background

During pressurized water reactor (PWR) power operation period, corrosion products tend to deposit in the fuel boiling zone and form chalk rivers unidentified deposit (CRUD). At a certain level of CRUD, boron acid will precipitate and depress local nuclear power, causing CRUD induced power shift (CIPS) incident, however, the operation data of reactors that have undergone CIPS indicate that CRUD thickness is not the only factor affecting CIPS.

Purpose

This study aims to evaluate the CIPS risk of PWR more scientifically by establishing an evaluation methodology that comprehensively considers CRUD characteristics and thermal-hydraulic condition.

Methods

Based on the internal mass transfer mechanism of the porous media, a model which could simulate boron deposition process inside CRUD was established by combining the consideration of CRUD morphology. According to the simulated results, the deep causes of CIPS in Callaway and Ulchin power plants were revealed.

Results

Evaluation results show that the most important factor of CIPS in Callaway power plant is CRUD thickness which is different from the contribution of CRUD porosity to Ulchin's CIPS.

Conclusions

The CIPS risk evaluation method of this study provides theoretical evidence and supporting data for more scientific CIPS analysis.

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Power flatten of small transportable nuclear reactor core based on co-evolution algorithm
Cheng HOU,Zheng SUN,Shouzhi ZHAO,Tengfei WU,Rongjun YU
Nuclear Techniques. 2021, 44 (9):  90602-090602.  DOI: 10.11889/j.0253-3219.2021.hjs.44.090602
Abstract ( 26 )   HTML ( 1 )   PDF(pc) (1890KB) ( 11 )   Save
Background

The small transportable nuclear power system designed with the solid block heat pipe stack as the core has the advantages of good environmental adaptability, system safety and reliability, deployment flexibility, and resistance to external events. In order to control the sharp rise in reactivity under the water flooding accidents, a spectral shift absorber Gd2O3 is added to its core fuel. During the process of power flatten by adjusting fuel enrichment and Gd2O3 mass fraction at different locations in the core, it is necessary to ensure that the core solution meets a series of objectives such as refueling cycle and critical safety in both the conditions of normal operation and the accident. It makes the power flattening problem of small transportable nuclear reactor with high dimensional decision variables, multiple objectives and constraints, and multiple operating conditions.

Purpose

This study aims to develop a core power flattening algorithm for small transportable nuclear power supply to reduce the computational cost.

Methods

Based on a co-evolutionary algorithm framework and the laws of physics, a power flattening algorithm was developed to reduce the dimensionality through clustering algorithms. Convergence acceleration was achieved through the collaboration between sub-populations. The agent model based on Gaussian process regression (GPR) was used to predict and screen a large number of core schemes, so as to effectively reduce computational costs.

Results

Computation results show that the power peak factor of the initial scheme is decreased from original 1.30 to 1.14 after the core optimization.

Conclusions

Compared with the traditional differential evolutionary algorithms and differential evolution algorithms embedded with clustering, the co-evolutionary based power flattening algorithm has significant advantages in terms of optimization quality and efficiency. The use of the clustering method and the surrogate model in the framework of co-evolutionary algorithms can effectively deal with the optimization of the complex reactor core.

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Application of super-resolution optical microscopy in biology
MAO Xiuhai, DU Jiancong, HUANG Qing, FAN Chunhai, DENG Suhui
Nuclear Techniques    2013, 36 (6): 60502-060502.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.060502
Abstract483)      PDF(pc) (6093KB)(6585)       Save

Background: A noninvasive, real-time far-field optical microscopy is needed to study the dynamic function inside cells and proteins. However, the resolution limit of traditional optical microscope is about 200 nm due to the diffraction limit of light. So, it’s hard to directly observe the subcellular structures. Over the past several years of microscopy development, the diffraction limit of fluorescence microscopy has been overcome and its resolution limit is about tens of nanometers. Methods: To overcome the diffraction limit of light, many super-resolution fluoresce microcopies, including stimulated emission of depletion microscopy (STED), photoactivation localization microscopy (PALM) and stochastic optical reconstruction microscopy (STORM), have been developed. Conclusions: These methods have been applied in cell biology, microbiology and neurobiology, and the technology of super-resolution provides a new insight into the life science.

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Cited: Baidu(3)
Research status of energy dispersive X-ray fluorescence spectrometer
ZHAO Fengkui, WANG Aimin
Nuclear Techniques    2013, 36 (10): 100402-100402.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.100402
Abstract212)      PDF(pc) (1792KB)(5158)       Save

Background: Energy dispersive X-ray fluorescence spectrometer has been improved rapidly in these years. Purpose: Research status of energy dispersive X-ray fluorescence spectrometers is reviewed, covering the main components in the spectrometer and spectra processing algorithms. Methods: On the component aspect, the working principles and performances of high-voltage generator, X-ray excitation sources, especially X-ray tubes and detector are compared. On the spectra processing aspect, results of different algorithms in spectrum de-noising, background subtraction, decomposition of the peaks and calculating the intensity of the fluorescence are analyzed separately. Results: On the component aspect, the effects to sensitivity and resolution of the spectrometer being caused by the high-voltage of the voltage generator, intensity of X-ray and resolution of the detector are concluded. On the spectra processing aspect, feasibilities of various algorithms are suggested. The advantages of wavelet transform, artificial neural network and partial least-squares method are discussed. Conclusion: Present difficulties in further improving of the spectrometer performance are analyzed. The prospect and the necessity of further research of EDXRF have been suggested.

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Cited: Baidu(1)
Calibration method and experiment based on I/Q demodulation principle
ZHANG Zhigang, ZHAO Yubin, XU Kai, ZHENG Xiang, LI Zheng, ZHAO Shenjie, CHANG Qiang, HOU Hongtao, MA Zhenyu, LUO Chen, MAO Dongqing, SHI Jing, WANG Yan, LIU Jianfei
Nuclear Techniques    2015, 38 (3): 30102-030102.   DOI: 10.11889/j.0253-3219.2015.hjs.38.030102
Abstract482)      PDF(pc) (1625KB)(3903)       Save
Background: In-phase/Quadrature (I/Q) demodulation technology is widely used in radio frequency signal phase control system. As the intrinsic errors in hardware, such as the imbalances of gain and phase in 90° hybrid and 0° hybrid, direct current (DC) offsets and phase errors from length difference of circuits, the output signal is an ellipse and the output phase is nonlinear to the input radio frequency (RF) signal. The detection of phase precision is influenced. Purpose: This study aims to reduce the effects of errors existed in the I/Q demodulators. Methods: A calibration method for I/Q demodulation technique is proposed and applied to research and development of I/Q integrate circuits, which is based on the surface mounted devices (SMD) chip. Results: Experimental tests showed that the phase error was less than ±0.15°, the amplitude stability was less than ±1%, and the channel delay was less than 10 ns. Conclusion: This calibration method, together with the designed circuit board for the RF signal front end preprocessing can reduce the effects of intrinsic errors efficiently. It has been being used in upgrading of beam trip diagnostic system in the storage ring of Shanghai Synchrotron Radiation Facility (SSRF).
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Cited: Baidu(2)
Decay time characteristics of plastic scintillator
HUANG Zhanchang, YANG Jianlun
Nuclear Techniques    2015, 38 (6): 60203-060203.   DOI: 10.11889/j.0253-3219.2015.hjs.38.060203
Abstract573)      PDF(pc) (677KB)(3579)       Save
Background: The plastic scintillator is mostly used for the inertia confinement fusion determination systems. It is necessary to know the scintillator decay time. Purpose: The aim is to measure the decay time of the plastic scintillator and analyze the applicability of single photon method. Method: The plastic scintillator is excited by 137Cs, and the decay time of the plastic scintillator is measured by single photon method. The ST401 and EJ232 plastic scintillators are measured by this device. The theory of single photon method is analyzed via statistics and the measurement process is simulated by Monte Carlo method. Results: The results are 2.9 ns with 50 ns for ST401 and 1.6 ns with 30 ns for EJ232 via double exponential fitting. The device has a dynamic range of over 104 and an intrinsic time resolution under 0.8 ns. The experiment result agrees to the simulated one. Conclusion: The comparison between the experiment result and the simulation result indicates that with the mean counts of stop detector no more than 0.1, the result measured by single photon method can be approximated to the decay time of plastic scintillator.
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Thermophysical properties of liquid lead-bismuth eutectic
SU Ziwei, ZHOU Tao, LIU Mengying, ZOU Wenzhong
Nuclear Techniques    2013, 36 (9): 90205-090205.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.090205
Abstract470)      PDF(pc) (1946KB)(3501)       Save

Background: Liquid lead-bismuth eutectic (LBE) is important spallation target materials and candidate coolant materials in accelerator driven subcritical (ADS)system. Purpose: Its thermodynamic physical properties are keys to understand the basic problems in ADS R&D. Methods: By the calculation of scientific laws as well as fitting other scholars’ experimental results, we tried to obtain the above thermodynamics physical properties. Results: By the calculation, we got formula about characteristic temperatures, density, specific heat, viscosity and thermal conductivity of liquid lead-bismuth alloy. And by fitting other scholars’ experimental results, we got the fitting formula. Conclusions: Finally, by the contrast analysis, we found that the fitting formula and calculation formula agree well, and fitting formula more approaches the experimental value with a high accuracy whose differential deviation is not over 1%.

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Cited: Baidu(9)
Synchrotron μ-XRF and XAFS in element distribution and speciation of air, soil and biological samples
YUAN Jing, LUO Liqiang
Nuclear Techniques    2014, 37 (08): 80101-080101.   DOI: 10.11889/j.0253-3219.2014.hjs.37.080101
Abstract409)      PDF(pc) (1225KB)(3117)       Save
Background: Synchrotron radiation micro probe analysis technique has been improved rapidly in recent years. Accurate qualitative or quantitative information on the interest element in environmental and biological samples such as atmospheric particles, soil, plant and earthworm plays a crucial role in the understanding of the effect of these elements in the samples. However, determination of these samples with complex matrices is a difficulty in multiple disciplines. With the rapid development of this area, the synchrotron-based techniques have been introduced to this area and have been widely used in analyzing various complex samples due to its superiority in fast and non-destructive determination. Purpose: In this review, the synchrotron source and its advantages in investigation on elemental analysis of the complex natural samples are introduced. Then, the applications of Synchrotron micro-X-ray fluorescence (μ-SXRF) and Synchrotron X-ray absorption fine spectroscopy (XAFS) in atmospheric particles, soil, plant and earthworm are reviewed, covering the distribution and the speciation of elements in these samples. Methods: μ-SXRF permits in situ mapping of biologically important elements of the sample even at sub-micrometer scale so that the spatially resolved element distribution maps can be obtained. XAFS allows determination of the speciation of high heterogeneity samples by providing the element oxidation state and local coordination environment. Results and Conclusion: μ-SXRF and XAFS have been widely used in element distribution and speciation of nature samples, especially for micro scale samples or micro area of samples such as atmospheric particles, soil, plant and earthworm. It is relevant to study thoroughly the presence, source, mobilization and fate of the elements using the information. Some challenges and future perspectives of the research and the tendency of development of synchrotron radiation technology have also been suggested.
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Cited: Baidu(1)
Application progress of solid 29Si, 27Al NMR in the research of cement-based materials
FENG Chunhua, WANG Xijian, LI Dongxu
Nuclear Techniques    2014, 37 (01): 10502-010502.   DOI: 10.11889/j.0253-3219.2014.hjs.37.010502
Abstract364)      PDF(pc) (273KB)(2973)       Save

Background: The solid-state Nuclear Magnetic Resonance (NMR) is an effective method for the research of cement-based materials. Now it focuses on using solid 29Si and 27Al NMR to research the hydration structure of the cement-based materials in cement chemistry. Purpose: A theoretical guidance is proposed for solid 29Si and 27Al NMR technology used in cement chemistry research. Methods: We reviewed the application of solid 29Si and 27Al NMR in the cement-based materials and analyzed the problem among the researches. Results: This paper introduced an fundamental, relevant-conditions and basic parameters of NMR, and studied the technical parameters of solid 29Si and 27Al NMR together with the relationship among the hydration structure of cement-based material. Moreover, this paper reviewed the related domestic and overseas achievements in the research of hydration structure of the cement-based materials using solid 29Si and 27Al NMR. Conclusion: There were some problems in the research on cement-based materials by technology of solid 29Si and 27Al NMR. NMR will promote the Hydration theory of cement-based material greatly.

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Cited: Baidu(2)
Design of high voltage power supply of miniature X-ray tube based on resonant Royer
LIU Xiyao, ZENG Guoqiang, TAN Chengjun, LUO Qun, GONG Chunhui, HUANG Rui
Nuclear Techniques    2013, 36 (8): 80403-080403.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.080403
Abstract513)      PDF(pc) (1714KB)(2951)       Save

Background: In recent years, X rays are widely used in various fields. With the rapid development of national economy, the demand of high quality, high reliability, and high stability miniature X-ray tube has grown rapidly. As an important core component of miniature X-ray tube, high voltage power supply has attracted wide attention. Purpose: To match miniature, the high voltage power supply should be small, lightweight, good quality, etc. Based on the basic performance requirements of existing micro-X-ray tube high voltage power supply, this paper designs an output from 0 to ?30 kV adjustable miniature X-ray tube voltage DC power supply. Compared to half-bridge and full-bridge switching-mode power supply, its driving circuit is simple. With working on the linear condition, it has no switching noise. Methods: The main circuit makes use of DC power supply to provide the energy. The resonant Royer circuit supplies sine wave which drives to the high frequency transformer’s primary winding with resultant sine-like high voltage appearing across the secondary winding. Then, the voltage doubling rectifying circuit would achieve further boost. In the regulator circuit, a feedback control resonant transistor base current is adopted. In order to insulate air, a silicone rubber is used for high pressure part packaging, and the output voltage is measured by the dividing voltage below ?5 kV. Results: The stability of circuit is better than 0.2%/6 h and the percent of the output ripple voltage is less than 0.3%. Keeping the output voltage constant, the output current can reach 57 ?A by changing the size of load resistor. This high voltage power supply based on resonant Royer can meet the requirement of miniature X-ray tube. Conclusions: The circuit can satisfy low noise, low ripple, low power and high voltage regulator power supply design. However, its efficiency is not high enough because of the linear condition. In the next design, to further reduce power consumption, we could improve the efficiency by controlling the current of resonant circuit.

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Cited: Baidu(3)
Pulse shape discrimination and energy calibration of EJ301 liquid scintillation detector
CHANG Le, LIU Yingdu, DU Long, WANG Yuting, CAO Xiguang, ZHANG Guoqiang, WANG Hongwei, MA Chunwang, ZHANG Song, ZHONG Chen, LI Chen
Nuclear Techniques    2015, 38 (2): 20501-020501.   DOI: 10.11889/j.0253-3219.2015.hjs.38.020501
Abstract1144)      PDF(pc) (1146KB)(2921)       Save
Background: EJ301 liquid scintillation detector has good time characteristics, pulse shape discrimination ability and the neutron detection efficiency. Purpose: This study aims to achieve the energy calibration, the pulse shape discrimination (PSD) ability etc. of EJ301 organic liquid scintillation detector. Methods: The waveform digital sampler DT5720 and digital pulse processing-pulse shape discrimination (DPP-PSD) control software were employed to simplify the data acquisition system. The pulse shape discrimination parameters such as the widths of long and short gates could be set up by software. The Compton peaks of 241Am (0.0595MeV), 137Cs-60Co (0.662 MeV, 1.171MeV, 0.662 MeV) and 40K (1.461 MeV) sources were used to obtain experimental data for pulse shape discrimination and the energy calibration of EJ301. Results: Experimental results show EJ301 detector has high efficiency, strong neutron/gamma-PSD ability. Conclusion: DT5720 and DPP-PSD control software have powerful function and are easy to use for both the PSD and energy calibration of EJ301. EJ301 organic liquid scintillation detector can be used for neutron measurement, and is suitable for measuring fast neutron energy spectrum and time of flight.
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Cited: Baidu(9)
Research on 1.6-GeV proton translation process using Geant4
YAO Zhiming, SONG Guzhou, HEI Dongwei, MA Jiming, ZHOU Ming, DUAN Baojun, SONG Yan, HAN Changcai
Nuclear Techniques    2014, 37 (03): 30205-030205.   DOI: 10.11889/j.0253-3219.2014.hjs.37.030205
Abstract548)      PDF(pc) (732KB)(2891)       Save

Backgroud: Chinese Spallation Neutron Source under construction consists of a proton accelerator which can speed up protons to 1.6 GeV. High-energy proton beams are used for radiography due to their high penetrability. Purpose: In order to understand how protons interact with materials when transmitting an object, the transport process of 1.6-GeV protons in different materials is simulated by Geant4. Methods: Energy loss, multiple coulomb scattering, inelastic and elastic collisions with nucleus are simulated independently by setting the physics process in Geant4. Beryllium, copper and tungsten are chosen as low-Z, middle-Z and high-Z material respectively. With respect to the effect of thickness, Tungsten of 5 g?cm?2, 10 g?cm?2 and 15 g?cm?2 is chosen as the material. Results: Number, energy and direction of motion are changed after protons penetrate an object. Changes are related to the composition and thickness of materials. Conclusion: The simulation results imply that transmission, energy-loss and distribution of scattering angle can reflect the thickness (in g?cm?2) and material composition of an object.

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Measurement and study of the photocathode quantum efficiency of photoelectric conversion device
XIA Jingkai, QIAN Sen, WANG Wenwen, NING Zhe, CHENG Yaping, WANG Yifang, JIANG Xiaoshan, WANG Zheng, LI Xiaonan, QI Ming, HENG Yuekun, LIU Shulin
Nuclear Techniques    2014, 37 (09): 90401-090401.   DOI: 10.11889/j.0253-3219.2014.hjs.37.090401
Abstract610)      PDF(pc) (784KB)(2884)       Save
Background: Photoelectric devices such as photomultiplier tubes (PMTs), photo diodes (PDs) and solar cells are widely used in many applications, so reliable evaluation on the performances of such devices is quite necessary, especially for the accurate measurements and calibrations on the photocathode quantum efficiency (QE). Purpose: We aim to build up a cathode performance evaluation system and study the properties of different types of cathodes. Methods: Two different methods named as the relative measurement and the direct measurements were employed to measure the QE values of cathodes. In addition, a 2D platform was built to achieve convenient and accurate processes for the plane type photocathode position uniformity test. Results: With the evaluation system, the cathode properties of dozens of photoelectric devices were tested. The measured QE results, either from the relative or the direct measurement, are consistent with the data provided by the manufacturers or a third party. Conclusion: Our cathode evaluation system is reliable and could be used to study the detailed photocathode properties such as QE, spectral response and position uniformity.
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Cited: Baidu(1)
A method of communication between EPICS IOC and EtherCAT devices
HE Yongcheng, WANG Chunhong, WU Xuan
Nuclear Techniques    2014, 37 (11): 110102-110102.   DOI: 10.11889/j.0253-3219.2014.hjs.37.110102
Abstract732)      PDF(pc) (913KB)(2878)       Save
Background: EtherCAT (Ethernet Control Automation Technology) is a kind of real-time Ethernet fieldbus protocol for industrial automation. The control system of many large-scale scientific facilities such as Beijing electron-positron collider (BEPCII), Chinese spallation neutron source (CSNS) was designed based on EPICS (Experimental Physics and Industrial Control System). Purpose: The aim is to implement EtherCAT as a real-time high speed control system solution for the EPICS based control system. Methods: The communication between EPICS IOC (Input/Output Controller) and EtherCAT devices was realized by using the OPC (Object Linking and Embedding for Process Control) Gateway driver. A real-time temperature monitoring appliance was taken as testing example. Results: The test results show that the communication between EPICS IOC and EtherCAT devices using the OPC Gateway driver is efficiently implemented. Conclusion: EtherCAT devices can be applied to communicate with the EPICS IOC to achieve real-time high-speed control by using the OPC Gateway driver.
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Cited: Baidu(2)
Physics design of a compact medical cyclotron
HE Xiaozhong, YANG Guojun, LONG Jidong, PANG Jian, ZHANG Kaizhi, SHI Jinshui
Nuclear Techniques    2014, 37 (01): 10201-010201.   DOI: 10.11889/j.0253-3219.2014.hjs.37.010201
Abstract530)      PDF(pc) (1105KB)(2775)       Save

Background: A compact cyclotron with energy of 11 MeV and current of 50 ?A is under construction in Institute of Fluid Physics of China Academy of Engineering Physics. The compact cyclotron is developed for medical isotope production. Purpose: To minimize the cost and to shorten the time of the development of the compact cyclotron, a lot of efforts were dedicated to the physics design of the compact cyclotron. Methods: Physics design of the main magnet was performed using TOSCA software, and start-to-end beam dynamics design was performed using home-made software CYCDYN. Results: Physics design of the compact cyclotron was given in details. Design methods and results of the main subsystems (including ion source, radial sector focusing magnet, RF cavity, central region and extraction system) were also given in this paper. Conclusion: Now commissioning of this cyclotron has been finished, and the goal for extracting proton beams of 11 MeV and 50 uA on average has been achieved. Physics design of the cyclotron has been validated by the commissioning results.

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Cited: Baidu(3)
Preparation of FLiNaK molten salt
ZONG Guoqiang, CHEN Bo, ZHANG Long, SUN Jiahong, DONG Qun’an, CHEN Wei, XIAO Jichang
Nuclear Techniques    2014, 37 (05): 50604-050604.   DOI: 10.11889/j.0253-3219.2014.hjs.37.050604
Abstract852)      PDF(pc) (716KB)(2732)       Save

Background: Possessing a series of advantages, such as low neutron absorption cross section, much lower vapor pressure and good heat transfer performance fluoride molten salts are widely used in the high-temperature hydrogen, solar storage, nuclear fuel and other energy fields. Among them, ternary mixture of LiF-NaF-KF (FLiNaK) is one of the most common candidate molten salt systems. Purpose: We aim to examine the effect of temperature, time, crucible material and fluoride reagents on the quality of the molten salt, and preliminarily master key process parameters for preparation of FLiNaK molten salt. Methods: The formation of FLiNaK molten salt was studied by a vacuum melting platform. The optional preparation conditions were obtained through the screening of melting temperature, timing, crucible material and fluorination reagent. Results: In the presence of NH4HF2, the oxygen content in FLiNaK salt could be controlled below 2×10?4. Metal ion impurities in molten salt, according to the general requirements of the quality standard for molten salt reactor, of which Be, Cu, Fe, Zr and Cd contents are less than 5×10?6. And impurities of sulfate and phosphate anions are less than 1×10?4 and 3×10?5, respectively. Conclusion: Using the present preparation method, the corrosion of furnace was greatly reduced. It was an efficient, low-cost, and safe process for the preparation of FLiNaK molten salt.

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Cited: Baidu(9)
Monte Carlo calculation of dose point kernel and absorbed dose distribution for electrons and photons
CHEN Shaowen, HUANG Long, WU Muying, TANG Qiang, LIU Xiaowei, ZHANG Chunxiang
Nuclear Techniques    2013, 36 (7): 70205-070205.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.070205
Abstract437)      PDF(pc) (1953KB)(2686)       Save

Background: The dose point kernel and the absorbed fraction are essential in the absorbed dose calculation for radionuclide therapy. Purpose: To calculate the scaled dose point kernels for 1MeV monoenergetic electrons and 32P, 90Y , 131I radionuclides, the absorbed fractions for 0.2 MeV and 4 MeV monoenergetic electrons and 32P, 90Y radionuclides which uniformly distributed in water spheres of various mass ranging from 10?2 to 103 g, and the radial distributions of absorbed dose rates for 32P, 131I, 90Y nuclides and 15 keV, 30 keV, 100 keV photons which uniformly distributed in a water (tumor) spherical shell (0.22?r?0.66cm) with an activity of 1MBq/cm3. Methods: EGSnrc Monte Carlo programs were used for simulation. Results: The calculation results were compared with those of other works. Conclusions: The results could give some help to absorbed dose calculations for radionuclide therapy.

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Cited: Baidu(1)
GEANT4 simulation and imaging reconstruction by backprojection algorithm for Compton camera
DING Changji, MAO Benjiang, YUAN Yonggang, JIANG Zhigang, YANG Chaowen
Nuclear Techniques    2015, 38 (11): 110402-110402.   DOI: 10.11889/j.0253-3219.2015.hjs.38.110402
Abstract978)      PDF(pc) (2109KB)(2654)       Save
Background: Due to its imaging principle advantages and the development of detectors, nuclear electronics, Compton camera has once again put forward. Purpose: This study aims to build a Compton camera via Monte Carlo simulation and test its backprojection algorithm. Methods: By using Monte Carlo simulation software GEANT4, a Compton camera with stripes structure is designed and data for reconstruction image of source is read out. Backprojection imaging reconstruction algorithm is studied for getting the reconstruction of source. Results: Using backprojection algorithm and simulated Compton camera, when the distance between source and the scattering detector is 40 mm, the spatial resolution is FWHM=8.0 mm, angular resolution is 3° and γ photon imaging efficiency is 0.38%, which are better than most of the pinhole and coded aperture γ camera imaging. Conclusion: Because of the existence of large amount of data, Compton camera needs long calculation time for measuring data. The next step is improving simulated Compton camera to study its performance parameters, while the maximum likelihood algorithm could improve the spatial resolution of Compton camera.
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Cited: Baidu(1)
Design of nuclear imaging system based on MURA coded aperture collimator
CHEN Lihong, LI Yongping, ZHAO Cuilan, YUAN Chao
Nuclear Techniques    2013, 36 (8): 80402-080402.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.080402
Abstract492)      PDF(pc) (1691KB)(2609)       Save

Background: Location nuclear imaging systems have been used in many fields, such as astronomical observation, radioactive source monitoring, nuclear development, biomedicine, etc. Purpose: It puts forward much higher requirements of monitoring and control of safety of nuclear facilities and radioactive sources. In this paper, a new portable nuclear imaging system is designed, which can be used in far field imaging. Methods: It uses high resolution detector which consists of LaBr3 crystal and H8500 position sensitive photomultiplier to meet the design requirements of high resolution. In order to acquire the higher radiation collection efficiency, we choose modified uniformly redundant arrays (MURA) as system collimator. It uses the maximum likelihood-expectation maximization (MLEM) algorithms in reconstruction procedure. Results: The test results show that the imaging system can image the far field radioactive source clearly. The field-of-view of our system can achieve the design goal: ±10°?±20°, and its resolution can be variable among 0.923°?2.038°. Conclusions: It can meet the design requirements of resolution and FOV very well. This radiation imaging system can achieve miniaturization and portability radiation imaging robot which is suited for the long-range control.

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Cited: Baidu(2)
Detection efficiency simulation and measurement of 6LiI/natLiI scintillation detector
DU Long, CHANG Le, WANG Yuting, ZHANG Song, CAO Xiguang, WANG Hongwei, ZHANG Guoqiang, ZHONG Chen, LI Chen
Nuclear Techniques    2014, 37 (04): 40201-040201.   DOI: 10.11889/j.0253-3219.2014.hjs.37.040201
Abstract519)      PDF(pc) (658KB)(2578)       Save

Background: Being of very high detection efficiency and small size, Lithium iodide (LiI) scintillator detector is used extensively in neutron measurement and environmental monitoring. Purpose: Using thermal reactor, neutron detectors will be tested and calibrated. And a new neutron detector device will be designed and studied. Methods: The relationship between the size and detection efficiency of the thermal neutron detector 6LiI/natLiI was studied using Monte Carlo code GEANT4 and MCNP5 package, and the thermal neutron efficiency of detector was calibrated by reactor neutrons. Results: The theoretical simulation shows that the thermal neutron detection efficiency of detector of 10-mm thickness is relatively high, the enriched 6LiI is up to 98% and the nature natLiI 65%. The thermal neutron efficiency of detector is calibrated by reactor thermal neutrons. Considering the neutron scattering by the lead brick, high density polythene and environment neutron contribution, the detection efficiency of 6LiI detector is about 90% and natLiI detector 70%. Conclusion: The detector efficiency can reach the efficiency value of theoretical calculations.

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Cited: Baidu(9)
P3HT/PCBM polymer thin films studied by synchrotron-based grazing incidence X-ray diffraction
YANG Yingguo, ZHENGGUAN Haojie, JI Gengwu, FENG Shanglei, LI Xiaolong, GAO Xingyu
Nuclear Techniques    2014, 37 (02): 20101-020101.   DOI: 10.11889/j.0253-3219.2014.hjs.37.020101
Abstract595)      PDF(pc) (1612KB)(2554)       Save

Background: The microstructures of P3HT (poly(3-hexyl-thiophene)) in P3HT/PCBM ([6,6]-phenyl C61-butyric acid methyl ester) thin films play a key role in governing the performance of organic solar cells (OSCs) based on these films. Purpose: We aim to study the self-organization of P3HT in the P3HT/PCBM thin films annealed at different temperatures. Methods: Using different incidence angles, information about the microstructures of P3HT at different depths in these films was obtained by synchrotron based grazing incidence X-ray diffraction (GIXRD). Results: It is shown that the crystalline structure of P3HT has been substantially improved by thermal annealing. One dimensional GIXRD clearly indicates that P3HT edge-on structures in the inner layers have been improved with their number increased in comparison with those at the surface and the interface layers. In addition, thermal annealing also helps the formation of P3HT face-on structures in the films, as evidenced by 2 dimensional GIXRD. Conclusion: The improved structures in these films lead to more charge transport channels formed to improve the carrier mobility, which in turn helps the improvement of OSCs. Thus, the present GIXRD results will improve the understanding of annealing effects at different depths of the P3HT/PCBM thin films for enhanced OSCs devices.

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MCNP coupled with post-processing software application development
HE Zehong, YE Minyou, WANG Zhongwei, MAO Shifeng, XU Kun
Nuclear Techniques    2015, 38 (6): 60601-060601.   DOI: 10.11889/j.0253-3219.2015.hjs.38.060601
Abstract841)      PDF(pc) (911KB)(2480)       Save
Background: Neutron flux and thermal distributed computing are vital parts of the process of nuclear fusion reactor design, its representative calculation software MCNP is based on the Monte Carlo method. However, the output of MCNP is a text file, thus the results are not conveniently and visually represented by manual analysis, and cannot be directly imported into post-processing software such as Ensight, Paraview and ANSYS for processing. Purpose: In order to enhance the efficiency of data analysis of MCNP output, a coupling program between the MCNP and post-processing software is proposed and implemented in this paper. Methods: The Microsoft Visual Studio 2010 (VS2010) is taken as a development platform, the coupling program is developed using C/C++ programming language to perform numerical/logic operations and various kinds of data format conversion required by post-processing software such as Ensight, Paraview and ANSYS, etc. Results: The coupling program was tested via “while-box” method, logical operations of MCNP calculation results, and data format conversion of MCNP data file processed by this program are satisfied for the requirement of the post-processing software for visual analysis. Conclusion: It provides effective support tools that bridge the connection between MCNP and the post-processing software for practical engineering design.
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Real-time signal transmission performance tests with optical fiber based on Aurora protocol
LU Ruiqi, ZENG Jianping, ZHAO Yubin, REN Hailong
Nuclear Techniques    2015, 38 (3): 30404-030404.   DOI: 10.11889/j.0253-3219.2015.hjs.38.030404
Abstract495)      PDF(pc) (569KB)(2477)       Save
Background: General Purpose Powder Diffractometer (GPPD) is one of Chinese Spallation Neutron Source (CSNS) diffractometers, which adopts Symptom Scale of Neurotransmitter Deficiency (SSND) detecting the position and the flight time of neutron when it hits, and the electronics system processes the detected neutron information. The shooting time T0, as a time reference point of the electronics system, is a real time signal. Traditional cable transmission meets the real-time signal transmission requirements, however, laying work will be rather complex and bring great difficulties to project since numerous of cable was needed. Purpose: The electronics control circuits is needed to transfer the received signal T0 to the lower electronics in real time with low propagation delay and low jitter via optical fiber, and the the propagation delay is less than 1 μs which including the 15-m optical fiber delay, the jitter is less than 0.1 μs. Methods: This paper describes a transferring scheme based on Spartan6 XC6SLX75T FPGA using Aurora protocol via optical fiber. The testing program is based on ISE Design Suite14.4 FPGA development platform, adopting high-precision oscilloscopes to the measure and calculate the transmission delay and jitter of different rise time signal T0 repeatly. Results: Repeated measurements show that the maximum propagation delay is less than 600ns and that the maximum jitter is less than 4 ns, in addition, the stability of jitter stability is good, and it meets the system requirements. Conclusion: It is feasible to use Aurora protocol via optical fiber to transfer real-time signal T0. Signal rise time has a certain influence on the delay and jitter, longer signal rise time corresponds longer delay and greater the jitter, so to shorten rise time of signal can reduce the transmission delay and jitter.
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Calculation and analysis of radioactive source term in PWR assemblies
CHEN Haiying, QIAO Yahua, WANG Shaowei, CHEN Yan, LAN Bing, ZHANG Chunming
Nuclear Techniques    2014, 37 (04): 40601-040601.   DOI: 10.11889/j.0253-3219.2014.hjs.37.040601
Abstract541)      PDF(pc) (473KB)(2473)       Save

Background: When fission occurs in fuel of reactor core, it produces a large amount of radioactive materials, which may cause harm to the environment and human health. Purpose: The radioactive materials in fuel could provide input data for shielding design of reactor coolant radioactive source term, analysis of accident source term and radioactive consequence assessment. Methods: The calculation of radioactive source in fuel was studied for pressurized water reactor, the calculation methods and models were established using ORIGEN-S, and the difference of nuclides radioactivity under different burnup was also studied. The effect of different versions of ENDF/B cross-section database on the calculation results was analyzed, so as to provide a basis for the calculation of radioactive source in fuel. Results: The results showed that the method established by ORIGEN-ARP was more suitable for calculating radioactive source term in fuel assemblies and the different versions of ENDF/B database had a great impact on radioactivity calculation. Conclusion: Based on the ENDF/B-VII database, using ORIGEN-ARP to calculate radioactive source term in fuel assemblies could not only improve efficiency, but also improve the calculation accuracy.

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Cited: Baidu(1)
Research of accelerator-based neutron source for boron neutron capture therapy
LI Changkai, MA Yingjie, TANG Xiaobin, XIE Qin, GENG Changran, CHEN Da
Nuclear Techniques    2013, 36 (9): 90203-090203.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.090203
Abstract481)      PDF(pc) (2256KB)(2444)       Save

Background: 7Li(p,n) reaction of high neutron yield and low threshold energy has become one of the most important neutron generating reactions for Accelerator-based Boron Neutron Capture Therapy(BNCT). Purpose: Focuses on neutron yield and spectrum characteristics of this kind of neutron generating reaction which serves as an accelerator-based neutron source and moderates the high energy neutron beams to meet BNCT requirements. Methods: The yield and energy spectrum of neutrons generated by accelerator-based 7Li(p,n) reaction with incident proton energy from 1.9 MeV to 3.0 MeV are researched using the Monte Carlo code-MCNPX2.5.0. And the energy and angular distribution of differential neutron yield by 2.5-MeV incident proton are also given in this part. In the following part, the character of epithermal neutron beam generated by 2.5-MeV incident protons is moderated by a new-designed moderator. Results: Energy spectra of neutrons generated by accelerator-based 7Li(p,n) reaction with incident proton energy from 1.9 MeV to 3.0 MeV are got through the simulation and calculation. The best moderator thickness is got through comparison. Conclusions: Neutron beam produced by accelerator-based 7Li(p,n) reaction, with the bombarding beam of 10 mA and the energy of 2.5 MeV, can meet the requirement of BNCT well after being moderated.

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Software management in EPICS environment
LEI Lei, HAN Lifeng, XU Haixia, LI Yongping
Nuclear Techniques    2015, 38 (6): 60501-060501.   DOI: 10.11889/j.0253-3219.2015.hjs.38.060501
Abstract523)      PDF(pc) (579KB)(2387)       Save
Background: Compared with commercial SCADA (Supervisory Control and Data Acquisition) software, EPICS (Experimental Physics and Industrial Control System) control system has no uniform way for software management at present. Developers in different projects deploy and invoke EPICS software modules in different ways. However, it is particularly important to manage the software modules scientifically and normatively for projects like thermonuclear fusion reactor, proton therapy and Thorium Molten Salt Reactor (TMSR), which helps to improve the reliability, maintainability and usability of system. Purpose: We aim to deploy EPICS software modules automatically and call them normatively. Methods: We implement the directory management using Linux Filesystem Hierarchy Standard (FHS), deploy software modules with Red Hat Package Manager (RPM) and shell scripts and manage all software modules with Linux service. Results: The scheme runs very well and reduces manual operation greatly. Conclusion: The results indicate that this scheme can address some issues in the usage of EPICS, which may help to build a unified, fully automated software platform for TMSR I&C system.
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CFD simulation analysis and validation for CPR1000 pressurized water reactor
ZHANG Mingqian, RAN Xiaobing, LIU Yanwu, YU Xiaolei, ZHU Mingli
Nuclear Techniques    2013, 36 (10): 100601-100601.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.100601
Abstract252)      PDF(pc) (5349KB)(2358)       Save

Background: With the rapid growth in the non-nuclear area for industrial use of Computational fluid dynamics (CFD) which has been accompanied by dramatically enhanced computing power, the application of CFD methods to problems relating to Nuclear Reactor Safety (NRS) is rapidly accelerating. Existing research data have shown that CFD methods could predict accurately the pressure field and the flow repartition in reactor lower plenum. But simulations for the full domain of the reactor have not been reported so far. Purpose: The aim is to determine the capabilities of the codes to model accurately the physical phenomena which occur in the full reactor vessel. Methods: The flow field of the CPR1000 reactor which is associated with a typical pressurized water reactor (PWR) is simulated by using ANSYS CFX. The pressure loss in reactor pressure vessel, the hydraulic loads of guide tubes and support columns, and the bypass flow of head dome were obtained by calculations for the full domain of the reactor. The results were validated by comparing with the determined reference value of the operating nuclear plant (LingAo nuclear plant), and the transient simulation was conducted in order to better understand the flow in reactor pressure vessel. Results: It was shown that the predicted pressure loss with CFD code was slightly different with the determined value (10% relative deviation for the total pressure loss), the hydraulic loads were less than the determined value with maximum relative deviation 50%, and bypass flow of head dome was approximately the same with determined value. Conclusion: This analysis practice predicts accurately the physical phenomena which occur in the full reactor vessel, and can be taken as a guidance for the nuclear plant design development and improve our understanding of reactor flow phenomena.

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Cited: Baidu(1)
Optimizing design for the maze exit of a 10-MeV electron irradiation accelerator
DUAN Zongjin, CHEN Yukai, REN Guangyi, HE Lijuan, LI Yuxiong, CHEN Zhi
Nuclear Techniques    2013, 36 (11): 110203-110203.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.110203
Abstract271)      PDF(pc) (3938KB)(2310)       Save

Background: Irradiation accelerator is being used more and more widely, but the optimizing of radiation shielding is always a problem to be solved. Purpose: To make the dose rates of the maze exit lower and the cost to achieve it less, it is of great significance to design a shielding which is cheap and effective. Methods: The radiation dose rates at different maze exits of a 10-MeV industrial electron linear accelerator were compared by formula and Monte Carlo (Fluka) method. A real-time measurement system composed of Mini Digital Data Logging (Mini-DDL) and Gamma detectors was also used. Results: With one corner added to the exit, another scattering would be generated. The dose rate of exit before changing was 3?4?Gy?h?1 while it was 200nGy?h?1 after that. Conclusion: The radiation dose rate at the exit will be reduced by one order of magnitude because of another scattering generated by the added turn to the maze exit. All of these do not increase any additional cost and conform to the ALARA (as low as reasonably achievable) principle. It provides a good reference for the future design of shielding for industrial electron linear accelerator.

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Cited: Baidu(4)
Research on the key technology of high-power solid-state pulse modulator
LI Feng, CHEN Zhihao, WU Yonghua
Nuclear Techniques    2013, 36 (7): 70104-070104.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.070104
Abstract470)      PDF(pc) (1674KB)(2295)       Save

Background: For construction of free-electron laser (FEL) apparatus, we designed a high-power solid-state modulator system based on the module of insulated gate bipolar transistor (IGBT) switch. Purpose: To meet the higher performance requirements of linear accelerator microwave power source for the FEL. Methods: The module circuit of the high-power modulator is introduced, as well as the critical auxiliary circuit including protection circuit of IGBT, damping circuit, demagnetization circuit and compensating circuits. Results: The whole modulator system is simulated by using software and the module differences that may occurred. The modulator with inductive adder topology can generate a 130 kV, 100A and 13MW pulse power. Conclusions: The results show that the inductive adder pulse modulator technology is feasible.

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Measurement of γ absorption dose rate through measuring the full energy peak of γ spectrum
HE Jun, YANG Chaowen
Nuclear Techniques    2014, 37 (07): 70403-070403.   DOI: 10.11889/j.0253-3219.2014.hjs.37.070403
Abstract616)      PDF(pc) (704KB)(2286)       Save
Background: At present most radiation dose meters have the serious problem of energy response, and they just use the count rate plus relative correction method to measure the dose rate. This method has large error, and cannot distinguish the type of radionuclide, also cannot obtain the contribution of each radionuclide to the dose rate. Purpose: The research of new method is to measure the dose rate and improve the accuracy of measurement. Methods: The method of γ dose rate measurement through measuring full energy peak of γ spectrum was put forward, the angular response function of parallel γ ray injected into detector was defined. The average angular response over full space in the energy range from 0.02 MeV to 3 MeV was calculated by Monte Carlo simulation for ?50mm×50mm NaI(Tl) detector. Measurement tests have been done using standard radioactive sources of 137Cs, 60Co, 152Eu, 133Ba and in reference radioactive field of 137Cs, 60Co, 226Ra, 241Am in a national lab. Results: The test errors are smaller than 2% compared with the theoretical value for standard sources, and smaller than 3% compared with the value of PTW 10 L spherical chamber for reference radiation field. Conclusion: The results show that the method is suitable for the dose rate measurement for a wide range of energy without experimental calibration, can calculate the dose rate of different energy ray, and at the same time identify the radioactive nuclides in the radiation source.
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Cited: Baidu(1)
A numerical method for extracting dual-energy value of X-ray transmission image based on MCNP
XIANG An, CHEN Ruitao
Nuclear Techniques    2014, 37 (07): 70203-070203.   DOI: 10.11889/j.0253-3219.2014.hjs.37.070203
Abstract363)      PDF(pc) (1384KB)(2286)       Save
Background: Traditional dual-energy X-ray inspection technology serves to classify different materials based on the proper value related with effective atomic number. Purpose: This paper aims to solve the problem of the relevance between the proper value and material’s thickness (thickness effect), which reduces the reliability of dual-energy inspection technology. Methods: A numerical method which combines Simpson formula and sequential quadratic programming (SQP) method is proposed to eliminate the thickness effect of dual-energy values. The process of X-ray inspection is simulated by Monte Carlo method based on MCNP. Probability-classification method is used to evaluate the effectiveness of diminishing error probability of material-classification, and classification boundaries of different materials. A practical X-ray inspection machine is used to verify this method. Results: The experimental results indicate that not only the thickness effect is diminished obviously by this method, but also the classification boundaries are effectively achieved. Conclusion: The dual-energy value of X-ray transmission image can be extracted by our proposed method with effectiveness and practical applicability.
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Turbulent heat transfer of liquid metal inside the sub-channels of reactor core
GE Zhihao, PENG Yongsheng, LYU Yijun, DENG Weiping, ZHAO Pinghui
Nuclear Techniques    2015, 38 (9): 90603-090603.   DOI: 10.11889/j.0253-3219.2015.hjs.38.090603
Abstract509)      PDF(pc) (1254KB)(2250)       Save
Background: Liquid metal has been proposed as the coolant of the fourth generation nuclear reactor and the accelerator driven sub-critical system. Due to its low molecular Prandtl number (Pr), liquid metal differs from other coolants like water or gas in heat transfer. Purpose: This study aims to investigate the character of heat transfer of liquid metal inside the reactor core. Methods: Speziale-Sarkar-Gatski (SSG) Reynolds stress model was applied to the Computational Fluid Dynamics (CFD) prediction of liquid metal flow and heat transfer inside the sub-channels of the reactor core. Effect of different dimensionless parameters, e.g. Reynolds number (Re), Pr, Grashof number (Gr) and pitch-to-diameter ratio (P/D) on the turbulent heat transfer calculated results was investigated. Results: The dimensionless convective heat transfer coefficient (Nu), predicted by the CFD method, agrees well with the experimental data and the empirical relations. Conclusion: Based on the analysis of various dimensionless parameters, it is found that the heat exchange performs better in triangular fuel assembly sub-channels than that in square sub-channels, under the same condition of P/D and Re. The inhomogeneous circumferential distributions of temperature and heat transfer can be effectively improved by increasing Re and P/D or choosing coolants with large Pr. When Re is larger than 10000, the buoyancy effect on liquid metal heat transfer could be ignored.
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High temperature gas-cooled pebble bed reactor steady state thermal-hydraulics analyses based on CFD method
SONG Shixiong, WEI Quan, CAI Xiangzhou, GUO Wei
Nuclear Techniques    2013, 36 (12): 120601-120601.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.120601
Abstract636)      PDF(pc) (4976KB)(2222)       Save

Background: Based on general purpose CFD code Fluent, the PBMR-400 full load nominal condition thermal-hydraulics performance was studied by applying local thermal non-equilibrium porous media model. Purpose: In thermal hydraulics study of the gas cooled pebble bed reactor, the core of the reactor can be treated as macroscopic porous media with strong inner heat source, and the original Fluent code can not handle it properly. Methods: By introducing a UDS in the calculation domain of the reactor core and subjoining a new resistance term, we develop a non-equilibrium porous media model which can give an accurate description of the core of the pebble bed. The mesh of CFD code is finer than that of the traditional pebble bed reactor thermal hydraulics analysis code such as THERMIX and TINTE, thus more information about coolant velocity fields, temperature field and solid phase temperature field can be acquired. Results: The nominal condition calculation results of the CFD code are compared to those of the well-established thermal-hydraulic code THERMIX and TINTE, and show a good consistency. Conclusion: The extended local thermal non-equilibrium model can be used to analyse thermal-hydraulics of high temperature pebble bed type reactor.

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Cited: Baidu(1)
Method of digital Dither adding for digital multi-channel pulse amplitude analyzer
CHEN Xiaomeng, ZHANG Yuzhong, AI Xianyun, LIANG Weiping, XIAO Wuyun
Nuclear Techniques    2015, 38 (5): 50401-050401.   DOI: 10.11889/j.0253-3219.2015.hjs.38.050401
Abstract492)      PDF(pc) (2008KB)(2199)       Save
Background: The key technology of digital multi-channel pulse amplitude analyzer (DMCA) has been surmounted in China, however, with the increasing of the translation gain increases of DMCA, one of the difficulties is how to make the nonlinear performance index of the system reach the standard. Technology of Dither has been used to realize “Bit Gain” in overseas research while it is still a deficiency in DMCA study in China. Purpose: This study aims to study the application of Dither technology in DMCA and discuss relevant digital Dither technology for DMCA. Method: Based on DMCA architecture characteristics, Dither signal is produced and removed in field programmable gate array (FPGA) by linear feedback shift register (LFSR), and is added to DMCA by the circuit of base line. Energy resolution and differential nonlinearity (DNL) of DMCA system has been measured to study the effect of Dither on DMCA. The mechanism of how the Dither affects DMCA has been analyzed. Results: Experimental tests showed that DNL of DMCA is improved by adding Dither while keep the same the energy resolution, verifying the applicability of this method. Conclusion: The technology method of digital Dither adding for DMCA is of practical significance to the further research to improve the precision of DMCA.
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Cited: Baidu(9)
PWR core transient temperature numerical simulation based on porous media model
CHEN Sen, LIU Yu, TIAN Maolin, TIAN Wenxi, QIU Suizheng, SU Guanghui
Nuclear Techniques    2015, 38 (9): 90601-090601.   DOI: 10.11889/j.0253-3219.2015.hjs.38.090601
Abstract436)      PDF(pc) (1552KB)(2189)       Save

Background: The coolant flow and heat transfer in the reactor are significant to the safety of pressure water reactor (PWR). Purpose: This study aims to obtain the coolant flow and heat transfer characteristics in the reactor core. Methods: The complete model of pressure vessel is built by Pro/E, and the thermal hydraulic characteristics of the core are simulated with commercial software CFX by using the porous medium model in the core. Results: The simulation results show that the application of porous media model can display the core coolant temperature distribution effectively and correctly, and the asymmetric operation conditions can cause asymmetric on reactor core. The transient accident calculation results show that the highest temperature of the coolant appears in the upper of the core. Conclusion: The porous media model can be used in the reactor core and it has a certain reference value for the thermal-hydraulic safety of pressurized water reactor.

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Micro SR-XRF analysis on underglaze copper red porcelain of Ming dynasty
GUAN Li, ZHU Jian, FAN Changsheng, YANG Yimin, CHEN Dongliang, XU Wei, ZHANG Jing, WANG Lihua
Nuclear Techniques    2013, 36 (7): 70103-070103.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.070103
Abstract352)      PDF(pc) (1341KB)(2181)       Save

Background: The firing techniques of producing underglaze copper red porcelain emerged in the Yuan dynasty and reached its maturity during the Ming and Qing Dynasties in Jingdezhen city. The technique of producing underglaze red porcelain was sensitive to the firing temperature and atmosphere, so it was very hard to produce and also difficult to display red color under the surface successfully. Purpose & Methods: The micro SR-XRF technique was employed to analysis a piece of sherd of underglaze copper red porcelain of early Ming dynasty. The Chemical compositions of glaze and color areas were presented, and the elemental contents in different color areas were obtained by using line-scanning techniques. Results: Some elements such as As and Pb were contained in raw materials, and the content of Cu had obviously increased with the color changing from gray to red. The results indicated that the nature mineral possibly used as the pigment for underglazed copper red porcelain coloration, and the color appearance also depends on the amount of copper in the pigments contained. Conclusions: This paper presents the advantage of the synchrotron radiation XRF technology and contributes to the science evidences for the Chinese ancient porcelain handcraft research.

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Comparative analysis and measurement of focus spot for X-ray source
SUN Chaoming, TANG Guangping, LI Qiang, WANG Zengyong
Nuclear Techniques    2015, 38 (11): 110202-110202.   DOI: 10.11889/j.0253-3219.2015.hjs.38.110202
Abstract565)      PDF(pc) (5036KB)(2175)       Save
Background: Image quality in radiographic testing is often conditioned by the size and distribution of X-ray source. However, determination of focal spot is not performed effectively in practice, thus it is difficult to accurately control the image quality in the testing. Purpose: This study aims to obtain a quick and efficient test method to evaluate the focal spot for X-ray source. Methods: Test tools such as pinhole plate, star test pattern and duplex wire image quality indicator (IQI) were used to measure the focal spot of a portable X-ray source separately. Several measurements were carried out and compared in details. Results: Results of star test pattern and duplex wire IQI were coincident, but different from the results of pinhole imaging method obviously. Conclusion: Nominal focal spot size of an X-ray source may be considerably different from that in practice use, so it is necessary to timely evaluate characteristics of the focal spot. The duplex wire IQI can usually replace star test pattern to measure un-sharpness in radiographic testing images and to evaluate focal spot size.
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SPECT/CT fusion imaging for differential diagnosis of bone solitary metastases in patients with lung cancer
CHANG Cheng,XIE Wenhui,LEI Bei,LIU Ciyi,FENG Jian
Nuclear Techniques    2013, 36 (9): 90301-090301.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.090301
Abstract279)      PDF(pc) (1882KB)(2163)       Save

Background: Making an accurate diagnosis of bone metastasis earlier is very important for lung cancer clinical stage and making treatment plans. SPECT/CT fusion imaging provides more information than SPECT in diagnosing bone metastases from benign lesions of the solitary abnormal radioactive nuclide distribution in patients with lung cancer. Purpose: We want to investigate the value of SPECT/CT fusion imaging in identifying solitary bone metastases in patients with lung cancer. Methods: 196 patients with lung cancer, whose bone scintigraphy demonstrated solitary abnormal radioactive nuclide distribution, were selected. SPECT/CT was employed for those lesions. SPECT and SPECT/CT bone images were analyzed by two seasoned nuclear medicine physicians separately. Each lesion was diagnosed with metastasis and benign lesion. The diagnosed results were compared with the final diagnosis. Results: 196 patients with lung cancer had 196 lesions, 112 bone metastatic lesions were proved to be bone metastatic criterion, 89 metastatic lesions were found by SPECT, and 106 metastatic lesions were found by SPECT/CT. The sensitivity, specificity and accuracy of SPECT/CT and SPECT in the diagnosis of bone metastasis were 94.6%(106/112), 92.9%(78/84), 93.9%(184/196); 79.5%(89/112), 78.6%(78/84) and 79.1%(155/196), respectively. The sensitivity, specificity and accuracy of SPECT/CT were higher than those of SPECT (χ2=11.25, P<0.05; χ2=7.00, P<0.05; χ2=18.35, P<0.05). Conclusions: SPECT/CT fusion imaging provided more information than SPECT imaging in distinguishing metastases from benign lesions of the solitary abnormal radioactive nuclide distribution in patients with lung cancer and improved the accuracy of the diagnosis of solitary bone metastasis of lung cancer.

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Cited: Baidu(2)
Influencing factors of dose equivalence for X and γ rays with different energy based on Monte Carlo
GUO Huiping, LYU Wenhui, LYU Ning, WEI Zhihao
Nuclear Techniques    2014, 37 (01): 10203-010203.   DOI: 10.11889/j.0253-3219.2014.hjs.37.010203
Abstract341)      PDF(pc) (1144KB)(2153)       Save

Background: The accuracy of dosimeter measurement of X and γ rays needs to be resolved. Purpose: The aim is to study the correction term of the equivalent process of low-energy X-ray and the natural radioactive source. Methods: Instead of the standard sources, X-ray machine was adopted on the dose instrument calibration. The influence factors of the equivalence between low-energy X-ray and high-energy X or γ rays were simulated using Monte Carlo (MCNP) software. Results: The influences of distance, space scattering, response of detector on dose equivalence were obtained. The simulation results were also analyzed. Conclusion: The method can be used in dose equivalent correction for low-energy X-ray, high-energy X or γ rays, which is significant for the widespread use of X rays.

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Three-dimensional visualization of fibrochondrocytes in rabbit patella-patellar tendon junction using synchrotron radiation-based X-ray phase contrast tomography
CHEN Huabin, HU Jianzhong, ZHOU Jingyong, ZHENG Cheng, WANG Zhanwen, CHEN Can, CAO Yong, YIN Xianzhen, LYU Hongbin
Nuclear Techniques    2015, 38 (11): 110101-110101.   DOI: 10.11889/j.0253-3219.2015.hjs.38.110101
Abstract376)      PDF(pc) (3229KB)(2121)       Save

Background: Synchrotron radiation-based X-ray phase-contrast computed tomography (SR-XPCT) is an advanced tool for nondestructive analysis of three dimensional inner microstructure of samples, and plays an important part in the researches such as spinal cord microvasculature and lung bronchium. Purpose: This study was to investigate the three-dimensional morphology of fibrochondrocytes in rabbit patella-patellar tendon junction (PPTJ) using SR-XPCT, and develop an advanced imaging method. Methods: Three PPTJs were harvested from healthy mature female New Zealand rabbits. The specimens were scanned by SR-XPCT at BL13W1 of Shanghai Synchrotron Radiation Facility (SSRF) in China. The tomographic image was captured by Charge Coupled Device (CCD) detector with a 0.65-μm resolution. The three-dimensional visualization images of PPTJ were reconstructed by VG Studio Max. After that, the specimens were embedded by paraffin for Safranin O/Fast-green staining. Results: High-resolution three-dimensional visualization images of PPTJ and the parameters of the chondrocytes in fibrocartilage zone were successfully obtained via the SR-XPCT. With spherical and ellipsoidal morphologic features and its configuration characteristics in three dimension, the fibrochondrocytes revealed by SR-XPCT were consistent with the results of traditional histological staining. The parameters of chondrocytes showed that the mean diameter of chondrocyte was (10.139±1.265) μm, the mean volume was (291.187±87.283) μm3 and 75.4% of the chondrocytes’ volume ranged from 200 μm3 to 400 μm3, the mean sphericity degree was 0.711±0.079, and 84.9% of chondrocytes’ sphericity degree ranged from 0.605 to 0.805. Conclusion: The three-dimensional microstructure of the PPTJ was intuitively, accurately and undistortedly realized by the SR-XPCT, which may act as a novel instrument to access the three-dimensional microstructure changes during the PPTJ healing process.

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Design of digital nuclear signal processing system for CdZnTe detector
ZENG Guoqiang, WEI Shilong, XIA Yuan, LI Qiang, XU Yadong, GE Liangquan, JIE Wanqi
Nuclear Techniques    2015, 38 (11): 110401-110401.   DOI: 10.11889/j.0253-3219.2015.hjs.38.110401
Abstract619)      PDF(pc) (1940KB)(2087)       Save
Background: CdZnTe (CZT) detector has excellent detection efficiency and resolution toward gamma ray at room temperature. It is a beneficial supplement to HPGe and scintillator detectors. Digital multi-channel analyzer (DMCA) plays significant role for high resolution spectrometer of CZT. Purpose: This study aims to overcome the effect of “hole tailing” for CZT detector by implementing digital nuclear signal processing system. Methods: A low noise charge sensitive amplifier is designed by considering optimal matching of detector and digital multi-channel analyzer. High speed analog-digital converter transforms the analog signal to discrete digital sequence signal. Digitized signals are processed by Field Programmable Gate Array (FPGA) chip in the DMCA. In this FPGA chip, fast-slow dual channel trapezoidal shaper and digital rise time discriminator are designed to overcome the problem of charge trapping of CZT detector. Digital rise time discriminator could eliminate the effect of “hole tailing” and improve the energy resolution of CZT detector. Results: For the 4mm×4mm×2.5mm capture plus structure of CZT detectors offered by Northwestern Polytechnical University, the best resolution is up to 3.6% for 241Am source, and up to 0.96% for 137Cs source. Conclusion: The optimal matching of each unit circuit in the whole digital nuclear signal processing system could improve the energy resolution for CZT detecting system. Digital multi-channel analyzer with rising time discriminator has significant advantage for CZT detecting system.
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Cited: Baidu(3)
Radio-synthesis and application research advance of amino acid molecular tracers labeling with 18F and 11C for tumor PET imaging
HE Shanzhen, WANG Shuxia, WANG Peng, LI Shilei, TANG Ganghua
Nuclear Techniques    2014, 37 (08): 80302-080302.   DOI: 10.11889/j.0253-3219.2014.hjs.37.080302
Abstract374)      PDF(pc) (905KB)(2079)       Save
Background: Positron emission tomography (PET) is in rapidly developing as a powerful imaging technique for diagnosis, efficacy evaluation and prognosis of tumor. In contrast to 18F-FDG, the amino acid tracers were helpful additional tools for differentiating tumor tissue and inflammation, edematous, necrotic and fibrotic tissue because of their low uptake in those tissues, so that amino acid tracers appear to be more specific than the widely used 18F-FDG. As a result, a number of attempts have been undertaken for radio-synthesis of amino acid with short half-life nuclide 18F and 11C. Purpose: The aim is to review and discuss the present knowledge on synthesis methods and preliminary clinic application of labeling amino acid. Methods: The advances on the synthesis methods and preliminary clinic application of labeling amino acid in recent years were introduced and discussed. Results: In recent years, many new 18F or 11C-labeled amino acids have been developed and their preliminary clinic applications were studied. Conclusion: The review provides an overview of this class of radiolabeled amino acids and highlights the current synthesis status and the key preliminary clinic applications.
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Radioactive product analysis of a small molten-salt reactor in primary loop
Weilong ZHOU,Rui YAN,Bo ZHOU
Nuclear Techniques    2021, 44 (7): 76-82.   DOI: 10.11889/j.0253-3219.2021.hjs.44.070601
Abstract708)   HTML60)    PDF(pc) (1198KB)(300)       Save
Background

Based on the research of molten salt reactor (MSR), a conceptual design of small MSR core with thermal power of 100 MWt is proposed to meet the power supply demand of small area. By adjusting the initial fuel load of the reactor core, the reactor can operate at full power for 1 250 days without refueling, and then batch process fuel at the end of its life.

Purpose

This study aims to analyze the yield and source of radionuclides in the main loop during such a small MSR operation by providing the constitutions, main components, and parameters according to the burnup characteristics and fuel salt characteristics of the long refueling cycle.

Methods

The calculation software KENOVI for three-dimensional Monte Carlo transportation program and burnup analysis module Origen-S were employed to analyze the fuel consumption analysis module, the storage of radioactive products in the main loop and the neutron energy spectrum and other neutron parameters.

Results

The computation results show that the radioactivity at the end-of-life this small MSR is about 7.36×1018 Bq, and the radioactivity of fission products in the end-of-life primary loop is about 5.89×1018 Bq, of which the inert gases, iodine isotopes and the volatile fission metal account for 7.35×1017 Bq, 9.56×1017 Bq, 8.17×1017 Bq respectively. The total radioactivity of actinide nuclides is about 1.47×1018 Bq, of which the 239Np accounts for 98%.

Conclusions

This study provides reference for radiation protection design and fuel reprocessing scheme of molten salt reactor.

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Review of nuclear technology in the application of COVID-19 epidemic prevention and control
Zhe WANG, Fanyu LIN, Xian SUN, Gaoyang YE, Yuexiang LU
Nuclear Techniques    2020, 43 (12): 120001-120001.   DOI: 10.11889/j.0253-3219.2020.hjs.43.120001
Abstract209)   HTML19)    PDF(pc) (1884KB)(166)       Save

In the early stage of the outbreak of COVD-19 in Wuhan city at the end of 2019, the demand for medical protective equipment increased rapidly. Many problems emerged, such as poor quality and short supply of protective masks, shortage of medical supplies caused by long sterilization cycles, difficult treatment of the medical waste and wastewater of which might cause the secondary infection. Herein, three specific applications of nuclear technology were summarized to fight against the COVID-19. The first one is the nuclear pore membrane (NPM) produced by nuclear technology. It can be used to fabricate face masks with high filtration efficiency and good reusability after simple processing. Hence the problems of poor reusability and poor filtration effects of common disposable masks can be solved by using NPM technology. The second application is the radiation sterilization technology in the process of producing medical supplies such as masks and protective clothing. The long cycle of common sterilization technology makes the demand exceed supply whereas the radiation sterilization technology can greatly shorten the production cycle and increase output, which could alleviate the shortage of medical supplies in anti-epidemic process. The third application is the use of γ-ray, X-ray or high-energy electron to sterilize medical wastewater and garbage, among which massive of surviving coronavirus are still infectious. It can treat large-volume of wastewater rapidly with a broad vision of application. Due to these unique advantages, nuclear technology has been playing an important role in this epidemic prevention and control, it possesses broader development prospects in the future.

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FPGA remote firmware update method based on SiTCP communication protocol with rollback function
Zhang CHEN, Zheng WANG, Jun HU
Nuclear Techniques    2020, 43 (11): 110401-110401.   DOI: 10.11889/j.0253-3219.2020.hjs.43.110401
Abstract195)   HTML33)    PDF(pc) (796KB)(124)       Save
Background

Field programmable gate array (FPGA) is widely used in many places, including readout system of large-scale high-energy physics experiments. This kind of experiments usually has large electronic systems with thousands of channels implemented together with FPGAs. Furthermore, these detectors and electronics are often located in special environments such as radiation field, under water or underground, hence the traditional single FPGA update method with joint test action group (JTAG) cable becomes unsuitable or inapplicable.

Purpose

This study aims to realize FPGA remote firmware update without additional Ethernet chips or network protocol, and ensure the security mechanism of the process and multi-FPGA updating extendibility in the future.

Methods

A new approach using silicon transmission control protocol (SiTCP) technique was proposed. The update firmware in the UDP packages was sent under the SiTCP protocol by MATLAB in host computer to FPGA, and the process of Flash memory programming to update firmware was dominated by FPGA, placing the role of PHY and MAC chips. The secure rollback function was implemented in the modified structure of FPGA firmware with separate update data area and original data area.

Results

UDP broadcasting has the ability to multi-FPGA updating, remote firmware update is achieved and tested the secure rollback mechanism well.

Conclusions

This method is suitable for remote operation with advantages such as no need for additional Ethernet chips, built-in safety function to fall back to a known situation, and extendibility of multi-FPGA updating.

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The elements and specification of 18F-FDG PET-CT and PET-MR tumor imaging report in Shanghai
Nuclear Techniques    2021, 44 (1): 10001-010001.   DOI: 10.11889/j.0253-3219.2021.hjs.44.010001
Abstract148)   HTML29)    PDF(pc) (880KB)(545)       Save
Positron emission tomography (PET) is an imaging device that can reflect biochemical metabolism in
vivo. When combined PET with X-ray computed tomography (CT) or magnetic resonance (MR), the biochemical
metabolic characteristics and pathological structure of tissues are all well represented. Compared with PET-CT, PETMR
has higher resolution for soft tissues, and shows the shape, boundary and surrounding conditions of the lesions
more clearly. More importantly, PET and MR scan synchronously, hence the scanning time is reduced, and the
radiation of CT is avoided. However, it is difficult to popularize the application of PET-MR due to its high inspection
cost. Moreover, the high magnetic field environment of MR limits its application in patients with implanted medical
devices, such as cardiac pacemaker, cochlear implant and insulin pump.
For non-nuclear medicine doctors, the examination report is the most intuitive basis for diagnosis and treatment
of patients. Therefore, it is necessary to describe the morphology of suspicious tumor and the its 18F-FDG uptake
value in the report. In order to standardize the 18F-FDG PET-CT and PET-MR tumor imaging reports, nuclear
medicine experts in Shanghai compiled the elements and specification of 18F-FDG PET-CT tumor imaging report and
18F-FDG PET-MR tumor imaging report, and presented in this paper as two complete specification reports
independengly. More details for each report template and sample download link address are provided for reference.
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Improvement and performance analysis of cusp-like pulse shaping algorithm
Xinyang FAN, Min WANG, Xu HONG, Tibo YANG, Guanghui LIAO, Zhouxuan OUYANG
Nuclear Techniques    2021, 44 (1): 10402-010402.   DOI: 10.11889/j.0253-3219.2021.hjs.44.010402
Abstract145)   HTML8)    PDF(pc) (3123KB)(70)       Save
Background

Digital shaping algorithms are widely applied to improving the energy resolution of digital nuclear instruments.

Purpose

This work aims to improve and analyze the performance of cusp-like shaping algorithm for digital nuclear signal with emphasis on the influence of shaping parameters on the shape of the shaped pulse.

Methods

Based on the peak pulse forming algorithm, flat-top parameter was introduced into cusp-like pulse shaping algorithm. The fast silicon drift detector (FAST-SDD) detector produced by Amptek company was employed to measure the pulse signal obtained from manganese sample, the effect of shaping parameters on the shape of the output signal and the separation of pile-up pulses were investigated by the cusp-like pulse shaping method, and compared with the common trapezoidal pulse shaping methods. In addition, Cusp-like shaping and trapezoidal pulse shaping were used for the sampled nuclear pulse signals, and then amplitude discrimination was performed to obtain energy spectrum information. Finally, the influences of the two methods on the counting rate and energy resolution of the same time were studied.

Results

The results show that the cusp-like pulse shaping has a fast falling edge and a narrow pulse width, makes it easier to separate the pile-up pulses than triangle pulse shaping.

Conclusions

Under the same peak time, trapezoidal pulse shaping has more advantages in energy resolution than cusp-like shaping, while cusp-like pulse shaping shows better performance in count rate.

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Simulation of energy deposition of β particles in betavoltaic battery transducer materials
Mingxu ZHANG,Lixin QIN,Man ZHAO,Jiangtao ZHAO
Nuclear Techniques    2021, 44 (2): 20202-020202.   DOI: 10.11889/j.0253-3219.2021.hjs.44.020202
Abstract144)   HTML7)    PDF(pc) (1264KB)(82)       Save
Background

The energy deposition behavior of β particles in transducer material is an important issue in the simulation of a betavoltaic battery, which is usually performed by Monte Carlo software Casino and MCNP (Monte Carlo N Particle Transport Code). However, it is difficult to simulate the continuous energy spectrum of β particles by Casino software. The commercial software MCNP is subject to many restrictions on its copyright, it is very necessary to study the energy deposition of β particles in transducer materials based on the universal open-source Monte Carlo program Geant4 (GEometry ANd Tracking, version 4).

Purpose

This study aims to develop a model based on Geant4 to study the energy deposition of β particles in betavoltaic battery transducer materials.

Methods

Based on the framework of Geant4 software, a general simulation model of energy deposition behavior was developed. The continuous β spectrum, the self-absorption of radioactive source, and the backscattering of β particles on the source-transducer interface were taken into account completely in this model for the Monte-Carlo simulation study, and the computation results were compared with that of Casino software.

Results

Simulation comparison results show that this simulation model can accurately simulate the energy deposition behavior of β particles in the transducer materials of betavoltaic battery.

Conclusions

Simulation model proposed in this study can be used to study the energy deposition of β particles in the transducer materials with advantages of convenient application, open software and easy extension to other source-transducer combinations.

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Research and application of neutron resonance in medium-heavy nuclei
Xianguo TUO, Fule LIU, Qibiao WANG, Chao DENG, Rui SHI, Keliang MU, Jiang NIU
Nuclear Techniques    2020, 43 (10): 100201-100201.   DOI: 10.11889/j.0253-3219.2020.hjs.43.100201
Abstract140)   HTML3)    PDF(pc) (2206KB)(77)       Save
Background

Neutrons play an important role in nuclear detection applications, and make up for the shortcomings of X-ray detection insensitivity to the atomic number. In a specific energy range, the cross section of neutron reaction varies drastically with the neutron energy, and resonance occurs. The resonance spectrum of nuclides is unique, and qualitative and quantitative analysis of nuclides can be carried out based on this. Among them, the resonance energy range of medium-heavy nuclei is in the eV~keV energy range, which is an important part of neutron resonance analysis.

Purpose

Due to the lack of conclusive articles on neutron resonance in medium-heavy nuclei, this paper summarizes the current research on neutron resonance.

Methods

By querying a large number of journal papers and books related to neutron resonance, the theory and application of neutron resonance of medium and heavy nuclear are summarized.

Results & Conclusions

At present, there have been many research results, and they have been widely used in temperature measurement, imaging, non-destructive analysis, nuclear data measurement, and other aspects. In this regard, by reviewing the literature and books on neutron resonance, the research status of neutron resonance at domestic and overseas are summarized and analyzed, and its development tendency is forecast.

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Study on spectrum stabilization technique for a portable LaBr3(Ce) gamma spectrometer
Chen CHEN,Huan WU
Nuclear Techniques    2021, 44 (4): 40401-040401.   DOI: 10.11889/j.0253-3219.2021.hjs.44.040401
Abstract138)   HTML16)    PDF(pc) (1577KB)(93)       Save
Background

As one of the most important issues in the field of gamma spectrum analysis, the main function of spectrum stabilization is to suppress the "spectral line drift" caused by environmental changes. Portable LaBr3(Ce) gamma spectrometer is mainly used to analyze and process the gamma spectra of radionuclides and obtain qualitative and quantitative information about radionuclides. It often works in the field complex environment where the spectrum drift is inevitable, hence must have the function of spectrum stabilization.

Purpose

This study aims to improve the performance of spectrum stabilization technique for a portable LaBr3(Ce) gamma spectrometer.

Methods

The intrinsic characteristic peak of LaBr3(Ce) detector and the peak of 40K in the natural background were made of as the reference peaks. Then, the concept of "spectrum similarity" was defined to calculate the similarity between the measured spectrum and the standard background spectrum. Finally, a new spectrum stabilization method using standard reference peak and "spectrum similarity" was proposed to measure and correct the deviation. Experiments were carried out verify the performance of this new method.

Results

Experimental results show that the technology can effectively stabilize spectrum in the temperature range of -30 ℃ to 50 ℃ without calibration of the relationship curve between the reference peak and the temperature, and the peak drift of the reference peak is stable within ±1 channel even if the temperature changes more than 50 ℃?h-1.

Conclusions

This technology effectively improves the application range of portable LaBr3(Ce) spectrometers.

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Automatic calibration system of small angle X-ray scattering experiment station at SSRF
Chunxia HONG, Ping ZHOU, Wenqiang HUA, Chunming YANG, Fenggang BIAN
Nuclear Techniques    2021, 44 (1): 10102-010102.   DOI: 10.11889/j.0253-3219.2021.hjs.44.010102
Abstract136)   HTML6)    PDF(pc) (1458KB)(95)       Save
[Background]

The quality of the experimental data is closely related to the optimal optical conditions of the end-station in the small-angle X-ray scattering (SAXS) beamline (lower scattering background, accurate beam intensity before and after the sample, etc.). At present, the optical conditions of the end-station are manually optimized in SAXS beamline (BL16B1) of shanghai synchrotron radiation facility (SSRF), which can not utilize the user's time effectively.

Purpose

This study aims to design and implement an automatic calibration procedure with Python on the platform of EPICS (experimental physics and industrial control system) and CSS (control system studio).

Methods

Firstly, the direct beam was searched and targeted using slit blades scanning, and then beam center was automatically optimized according to the single-objective and multi-objective optimization methods of genetic algorithm, the calibration is not completed until an optimal scattering background image is obtained.

Results

The results show that the automatic beamline calibration system can complete the motors optimization of slits and beamstop in 30 min, much faster than manual operation.

Conclusions

Proposed automatic calibration system simplifies the optical path optimization of experimental station and improves the automation of the SAXS beamline station at SSRF.

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Study on the particle size distribution of high temperature FLiBe molten salt
Lizhi LIU, Haiying FU, Zhongying LIU, Jifei MA, Lin DU, Xiaoxing TANG, Yuan QIAN, Jian YAO, Yulan LI
Nuclear Techniques    2020, 43 (10): 100605-100605.   DOI: 10.11889/j.0253-3219.2020.hjs.43.100605
Abstract129)   HTML1)    PDF(pc) (1069KB)(57)       Save
Background

Beryllium bearing molten salt has strong chemical toxicity, hence needs to be accurately monitored and effectively removed at high temperature.

Purpose

This study aims at the characteristics of particle size distribution of high temperature FLiBe molten salt.

Methods

Based on the experimental device of low pressure distillation of molten salt and Dekati low pressure impact sampler (DLPI), an experimental device for measuring the particle size of high temperature molten salt particles was set up, and the particle size distribution of FLiBe molten salt under different experimental conditions was studied. The effect of gas purging and different sampling time on the particle size distribution of molten salt particles under high temperature were investigated, and scanning electron microscope (SEM) was employed to examine the experimental measurement results.

Results & Conclusions

The experimental results show that the particle size of the molten salt particles is concentrated above 2.5 μm at room temperature, while at high temperature, it is concentrated at 0.26~2.5 μm. The sampling time has no obvious influence on the particle size distribution of molten salt particles; although the final concentration of molten salt particles is changed by gas purging, it does not significantly affect the particle size distribution. The SEM results of the collected samples verify the accuracy of the particle size scale of the experimental device, and it is observed by SEM that the molten salt particles are in the shape of regular spherical rather than crystalline, which may be caused by the collision and deposition of molten salt particles.

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Neutronic performances of small modular thorium-based molten salt reactor starting with TRUs
Chunyan ZOU,Chenggang YU,Guifeng ZHU,Wei GUO,Xiangzhou CAI,Jingen CHEN,Yang ZOU
Nuclear Techniques    2020, 43 (12): 120601-120601.   DOI: 10.11889/j.0253-3219.2020.hjs.43.120601
Abstract127)   HTML9)    PDF(pc) (4253KB)(59)       Save
Background

Transuranic isotopes (TRUs) in the spent fuel of pressurized water reactor (PWR) contain more than 50% of fissile fuels and can be used as a starting fissile fuel for thorium fuel cycle.

Purpose

This study aims to analyze the neutronic performances of a small modular thorium-based molten salt reactor (SM-TMSR) core with TRUs as fissile fuel and Th as fertile fuel.

Methods

Considering the batch reprocessing period and the limit value of the inherent safety, proper scenarios for thorium utilization in the SM-TMSR initiated by TRUs were proposed for the evaluation of the neutronic characteristics. Reactor analysis software SCALE6.1 was employed to analyze the influences of two important parameters (fuel volume fraction and initial heavy metal mole fraction) on the characteristics of neutron spectrum, 233U production, graphite life, temperature coefficient, TRUs consumption, etc.

Results & Conclusions

The calculation results show that TRUs are an ideal fuel for starting Th-U fuel cycle of the SM-TMSR. Considering the constraints of the graphite's five-year life and the intrinsic safety (-5~-8 pcm?K-1), the core with 6% heavy metal mole fraction and 25% fuel volume fraction can obtain a preferable fuel utilization efficiency. With the thermal power of 150 MW for 5-year full-power operation, the uranium production is about 16.0 kg?a-1 and the transmutation rate of TRUs can achieve about 36.1 kg?a-1, which can effectively reduce the spent fuel containing TRUs.

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Analysis of Th-U and U-Pu fuel cycle in a 2 500 MWth molten chloride salt fast reactor
Xiaoxiao LI, Chenggang YU, Yuwen MA, Xiangzhou CAI, Jingen CHEN, Xingwei CHEN
Nuclear Techniques    2020, 43 (11): 110601-110601.   DOI: 10.11889/j.0253-3219.2020.hjs.43.110601
Abstract125)   HTML2)    PDF(pc) (1492KB)(54)       Save
Background

The molten chloride salt fast reactor (MCFR) has advantages of high solubility of nuclear fuel and fast neutron spectrum, which makes it possible to achieve high breeding and transmutation efficiency.

Purpose

This study aims to investigate the neutronics characteristics of Th-U fuel cycle and U-Pu fuel cycle in a 2 500 MWth MCFR, including the critical characteristic, burnup evolution, and breeding and transmutation performance.

Methods

The 233U and 239Pu were used as ignition fuels of Th-U fuel cycle (U3+Th) and U-Pu fuel cycle (Pu9+DU) respectively, and their fertile materials were 232Th and depleted uranium (DU), correspondingly. The analysis of the transition modes TRU+Th and TRU+DU with TRU as ignition fuel are also introduced.

Results

Considering the neutron absorption rate of actinides, neutrons produced per fission (ν) and the conversion ratio (CR), nuclear fuel cycle mode of U3+Th needs a variable feed of fissile fuel to maintain the critical operation of the core, whereas Pu9+DU, TRU+DU and TRU+Th can be operated for a long time without on-line refueling, that is 46 a, 50 a and 29 a, respectively.

Conclusions

TRU+Th fuel cycle mode is promising to MCFR due to its high self-sustaining breeding and high effective transmutation.

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Design and numerical simulation of Stirling heater for molten salt space reactor
Heng ZHAO, Yang ZOU, Ye DAI, Hongjie XU, Jie ZHANG, Fan HE
Nuclear Techniques    2020, 43 (10): 100601-100601.   DOI: 10.11889/j.0253-3219.2020.hjs.43.100601
Abstract123)   HTML5)    PDF(pc) (2218KB)(68)       Save
Background

Stirling heater is used for heat capture in the molten salt space reactor power generating system, and its heat transfer performance has a great influence on the output power and efficiency of the space reactor energy conversion system.

Purpose

This study aims to improve the heat transfer performance of the heater by numerical simulation of designed fins in molten salt channel and porous Stirling internal thermal receiver.

Methods

The computational fluid dynamics program Fluent was employed to design and optimize the structure of the heater. Thermal-hydraulic characteristics of different fins and molten salt channel types, such as flow field, pressure field and heat flux distribution were simulated and compared.

Results

Adding fins in the molten salt channel can improve the heat transfer performance of the Stirling heater, and with the increase of fin height and the decrease of fin spacing, the heat transfer performance further improves. Compared with radial inlet and tangential inlet, the double-radial inlet and outlet channels have more uniform heat flux distribution and better heat transfer performance.

Conclusions

The results of this study provide useful references for the design of the Stirling heater in molten salt space reactor.

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Simulation study on the performance of micro X-ray tube with diamond optical window
Yiqiang XING,Jiankun ZHAO,Weicheng LI,Yibao LIU,Wei LIU,Shuang JIANG
Nuclear Techniques    2021, 44 (4): 40201-040201.   DOI: 10.11889/j.0253-3219.2021.hjs.44.040201
Abstract123)   HTML8)    PDF(pc) (1382KB)(62)       Save
Background

As a hot material, diamond has been widely used in various civil and military equipment with high hardness (Mohs hardness is 10), compressive strength (greater than 1.2 GPa), excellent thermal (thermal conductivity at room temperature is 20~22 W·cm-1·K-1, thermal expansion coefficient at room temperature is only (1.1~1.3)×10-6 K-1), optical (higher transparency to X-rays) and electrical properties. Traditional optical window material beryllium is harmful to the human body and industrial hazards, its hardness, thermal conductivity and the thermal expansion coefficient are much lower than that of diamond.

Purpose

This study aims to explore the performance of micro X-ray tube with diamond optical window by simulation, obtain the best thickness of diamond for X-ray tube optical window and its shielding effect against low, medium and high energy X-ray.

Methods

The Monte Carlo method was used to calculate the effective transmission ratio, peak back ratio and transmission ratio of characteristic X rays with diamond optical window in high energy region. The X-ray tube with 50 kV tube voltage and 1.0 mA tube current was taken as an example to determine the optimal thickness of diamond.

Results

Simulation results show that the Kα characteristic X-ray effective transmittance and peak to total X-ray ratio of the silver target increase continuously with the increase of the diamond window thickness, and the optimum diamond thickness is 2.0 mm. Under the optimal thickness of 2.0 mm, the effective transmittance is 154.5%, high-energy X-ray transmittance is 74.5%, and the characteristic X-ray peak back ratio is 27.9%.

Conclusions

Diamond can be used as a substitute for beryllium optical windows and has good application prospect.

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Development and verification of fuel management code for liquid-fueled molten salt reactor based on deterministic code system
Kaicheng YU,Maosong CHENG,Zhimin DAI
Nuclear Techniques    2021, 44 (4): 40603-040603.   DOI: 10.11889/j.0253-3219.2021.hjs.44.040603
Abstract122)   HTML8)    PDF(pc) (1451KB)(45)       Save
Background

Molten salt reactor (MSR), a candidate of the Generation IV reactors, has the advantages of inherent safety and good neutron economy. The circulation flow of fuel, on-line refueling and reprocessing are the three features of liquid fuel in MSR. Due to the features of liquid fuel, the fuel management regulations for conventional reactors that use solid fuels are not applicable to liquid-fueled MSR.

Purpose

This study aims to develope a new fuel management code named ThorNEMFM to analyze liquid fuel management of MSR.

Methods

First of all, the self-developed deterministic code ThorCORE3D was coupled with the cross section processing module and a burnup calculation module. Then a fuel management analysis program ThorNEMFM was developed for liquid fuel molten salt reactor to realize on-line feeding and fission product processing. Finally, the ThorNEMFM was verified on molten salt reactor experiment (MSRE), molten salt breeder reactor (MSBR) and molten salt fast reactor (MSFR).

Results

The results of benchmarks for MSRE, MSBR and MSFR indicate that ThorNEMFM has a high accuracy with benchmarks in comparison with the reference.

Conclusions

ThorNEMFM is suitable for calculation and analysis of fuel management of MSR.

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A comparative study on the focus size of different target materials of micro target X-ray source
Zhuo ZUO, Xing HE, Song ZHANG, Yucheng YAN, Jun QIN
Nuclear Techniques    2020, 43 (10): 100401-100401.   DOI: 10.11889/j.0253-3219.2020.hjs.43.100401
Abstract120)   HTML5)    PDF(pc) (1070KB)(57)       Save
Background

Micro target X-ray source has attracted much attention in X-ray microscopy imaging. The focus spot size of X-ray directly affects the spatial resolution of sample.

Purpose

This study aims to investigate the influence of target materials and target microstructures on the emission spot of X-ray tube by simulation. The influence of different target materials on the focus size of X-ray tube is also discussed.

Methods

Monte Carlo simulation code MCNP5 was employed to calculate the focus size with five different target materials, i.e., Mn, Mo, Silver, Rt, Wu and three different target microstructures, i.e., hemisphere, cone and cylinder. The full width at half maximum (FWHM) of the light intensity distribution line was used as the standard to measure the spot size.

Results

The results show that the minimum focus size can be achieved by micro cone structure target at the incident electron energy of 100 keV. Moreover, different target materials have obvious influence on the focus size behind the target. The focus size decreases with the increase of the atomic number of the target material at the beginning, but expands to a certain extent with the further increase of the atomic number, showing a suppression trend. The influence of different target microstructures on the focus size is obviously related to the target type. The difference of focus size between cylinder and cone is up to 30 μm. Compared with the cylindrical tungsten target, the spot size decreases by 17.93% by using micro cone target structure and the silver target.

Conclusions

Compared with the traditional transmission X-ray tube, the micro target X-ray tube is easy to implement because it does not need strong electron focusing equipment. The methodology and the Monte Carlo simulation results are valuable for guiding the design and optimization of micro target X-ray tube source.

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Irradiation demagnetization of permanent magnets in insertion device for high-energy synchrotron radiation light source
Pingcheng LIU, Qiongyao LIU, Zhongjian MA, Huijie ZHANG, Mingyang YAN, Qingbin WANG
Nuclear Techniques    2020, 43 (10): 100101-100101.   DOI: 10.11889/j.0253-3219.2020.hjs.43.100101
Abstract119)   HTML11)    PDF(pc) (1227KB)(48)       Save
Background

In synchrotron radiation facilities, the insertion devices are installed on the storage ring to produce high brightness, high coherence, and adjustable polarization synchrotron radiation, which are composed of periodic permanent magnet arrays. The permanent magnets are continuously exposed to beam loss electrons due to the Touschek effect. As a result, the permanent magnets can be more or less damaged and deteriorates the magnetic field of insertion devices. Radiation-induced demagnetization of permanent magnets in the insertion device is one of the critical issues for synchrotron radiation facilities.

Purpose

This study aims to simulate the irradiation field and radiation damage of the Nd2Fe14B permanent magnet insertion devices during the routine operation of the high energy photon source (HEPS).

Methods

First of all, Monte Carlo code FLUKA was utilized to calculate the relationship between the absorbed dose and demagnetization of Nd2Fe14B magnet array based on the Spring-8 experiment. Then the different electronic sampling modes were set to calculate the irradiation field in the insertion device according to the actual beam loss conditions at HEPS. Finally, the demagnetization and countermeasures were analyzed according to the spatial distribution of absorbed dose.

Results

When HEPS works in top-up mode, the irradiation of the magnetic pole in the upstream end of the insertion device is more severe. Most of the absorbed dose (about 99.7%) is contributed by photon, electron and positron. According to the beam loss parameters by physical calculation, the expected life of the insertion device is 2.1 to 4.6 years.

Conclusions

Placing local shielding layer and increasing the gap are the effective measures to protect the insertion devices, hence slow down radiation demagnetization of permanent magnet.

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Research on application of time-varying tune calculation algorithms on SSRF
Xing YANG,Longwei LAI,Fangzhou CHEN
Nuclear Techniques    2020, 43 (12): 120101-120101.   DOI: 10.11889/j.0253-3219.2020.hjs.43.120101
Abstract117)   HTML6)    PDF(pc) (2671KB)(53)       Save
Background

Tune is one of the most important characteristic parameters of storage ring, it seldom changes over time, hence can be obtained by a simple harmonic analysis on the beam position data. In some particular process, tune will change with time.

Purpose

This study aims to explore and optimize the time-varying tune calculation algorithms for the tune drift caused by the nonlinear effect of Lattice during the decay of the residual transverse oscillation damping, after the injection of the storage ring.

Methods

First of all, the applicability of the wavelet algorithm and numerical analysis of fundamental frequencies (NAFF) algorithm for time-varying tune calculation was analyzed, and their performances were on above physical process of nonlinear effect of the storage ring were compared. Then the better Morlet wavelet algorithm was employed to quantitatively analyze the drift of tune during the injection of the Shanghai Synchrotron Radiation Facility (SSRF) storage ring and evaluate the nonlinear intensity changes of the SSRF during different operating period.

Results

Algorithm comparison results show that both algorithms can realize the dynamic analysis of time-varying tune, but the wavelet method shows better performance. Evaluation results of nonlinear strength change of SSRF storage ring show that when the data analysis window is selected as 6 000 cycles, a track offset change 0.3 mm, and tune change as small as 0.000 1 can be detected. During the period of storage ring injection, the tune changes obviously.

Conclusions

By applying the morlet wavelet algorithm, the complete trajectory of the tune drift can be tracked.

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Research and applications of bunch purity monitor at SSRF
Bo GAO,Longwei LAI,Xiaoqing LIU,Shanshan CAO,Yongbin LENG
Nuclear Techniques    2021, 44 (3): 30101-030101.   DOI: 10.11889/j.0253-3219.2021.hjs.44.030101
Abstract116)   HTML16)    PDF(pc) (1562KB)(89)       Save
Background

The phase-II beam line project is currently under construction at Shanghai synchrotron radiation facility (SSRF), and one of its important goals is to have the ability of pumping experiments with high time resolution. High time resolution experiments require the purity of the probe bunch to reach the order of 10-5. However, the traditional bunch-by-bunch charge measurement based on the beam position monitor has a resolution of only 10-4.

Purpose

This study aims to propose and implement a bunch purity measurement system for high time resolution at SSRF.

Methods

Based on the time-correlated single-photon counting technology, a bunch purity monitor was developed and installed on the diagnostic beam line of SSRF. An evaluation experiment was designed to verify its performance and optimize this bunch purity measurement system.

Results

The experimental results show that the resolution of the new bunch purity monitor can reach to 10-7 in a few minutes.

Conclusion

The new bunch purity measurement system is applicable to measuring the longitudinal distribution of electron bunches,and studying the effect of filling patterns on purity.

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Optimization of critical extrapolation for the restart of China advanced research reactor
Huaichang RAN,Jianxiao ZHEN,Jianlong LI,Yanyan GE,Yulin WANG
Nuclear Techniques    2020, 43 (12): 120602-120602.   DOI: 10.11889/j.0253-3219.2020.hjs.43.120602
Abstract115)   HTML2)    PDF(pc) (836KB)(51)       Save
Background

Critical extrapolation is necessary during the restart of China advanced research reactor (CARR) after a long shutdown period. The photoneutron in the heavy water tank is not only the neutron source during the reactor restart, but also the background of the detector. During the extrapolation process, the background neutron makes the extrapolation curve "convex", and the extrapolated critical rod position is overtakes the actual critical rod position, so the extrapolation process is dangerous.

Purpose

This study aims to optimize critical extrapolation by making use of neutron background value of detector.

Methods

Based on the control rod grid worth curve in CARR and extrapolation formula, the background value was obtained by fitting method to improve the extrapolation process. The critical extrapolation formula of control rod was derived, and the background value was obtained by fitting with the measured neutron numbers corresponding to different rod positions in the experiment. Then, the background value was applied to the correction of extrapolated critical rod position value.

Results

The extrapolation results show obvious improvement, and the modified extrapolated rod position basically satisfies the linear relationship between the experimental rod position and the reciprocal of detection neutron count.

Conclusions

The data fitting method can get the background value of the detector, which can significantly improve the extrapolation process.

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Study on the activity estimation method of shielded multi-energy gamma-ray sources
Maolin XIONG, Qingxian ZHANG, Jian ZHANG, Jin YANG, Liangquan GE, Kun SUN
Nuclear Techniques    2020, 43 (11): 110203-110203.   DOI: 10.11889/j.0253-3219.2020.hjs.43.110203
Abstract113)   HTML6)    PDF(pc) (1961KB)(99)       Save
Background

During the radioactive source inspection or the orphan source disposal, it is essential to estimate the activity of the radioactive source quickly and effectively. However, this may be difficult, especially when the source is under shield with unknown shield thickness.

Purpose

This study aims to establish an activity estimation method of shielded multi-energy gamma-ray sources.

Methods

First of all, based on the relationship between the material attenuation coefficient and energy of the gamma-ray source, a method for the activity estimation of shielded multi-energy gamma-ray source was established. Then, influences of the position bias between the radioactive source and the detector, the characteristic energy selection, and the effect of statistical fluctuations were investigated by experiments. Finally, the optimal characteristic energy of common multi-energy gamma-ray sources and the maximum measurable shield thickness of the radioactive sources with different activities were analyzed.

Results

The experimental results show that the relative errors between the estimated thickness and the real thickness is less than 4%, and the relative errors between the estimated activity and the real activity is less than 5%.

Conclusions

The method proposed in the paper can be applied to the radioactive source inspection or the orphan source disposal.

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Design and implementation of gigabit ethernet transmission system based on Zynq-7000
Zhenlei YANG,Chengmin LIU,Xianguo QING,Hongliang ZHU,Chao BAO,Tianzhi JIANG,Heng YU,Jin LI,Tingfang LUO,Hang YUAN,Wei SHAN
Nuclear Techniques    2021, 44 (2): 20401-020401.   DOI: 10.11889/j.0253-3219.2021.hjs.44.020401
Abstract113)   HTML5)    PDF(pc) (1748KB)(171)       Save
Background

With the increasing complexity, integration level and data volume of nuclear instrumentation and control system, conventional data buses, such as peripheral component interconnect (PCI) or controller area network (CAN), are difficult to meet the needs of rapid data transmission.

Purpose

This study aims to design and implement a Gigabit Ethernet transmission system based on the Xilinx's Zynq-7000 system on chip (SoC) and user datagram protocol (UDP).

Methods

First of all, the system architecture of UDP Gigabit Ethernet transmission system for nuclear instrumentation and control system was introduced in detail. Then the ModelSim toolkit was employed to verify designed system functions by simulation. Finally, the Gigabit Ethernet transmission system was implemented using ZC706 development board, and tested by experiment.

Results

Experimental results show that the data transmission speed can reach 870 Mbps.

Conclusions

The Gigabit Ethernet transmission system can meet the actual transmission requirements of most nuclear instruments and control system.

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Study on key parameters design of small helium xenon cooled reactor
Wenzhen HU, Jian DENG, Xiaojing LIU, Zhongchun LI, Bing XUE
Nuclear Techniques    2021, 44 (1): 10601-010601.   DOI: 10.11889/j.0253-3219.2021.hjs.44.010601
Abstract112)   HTML3)    PDF(pc) (1326KB)(71)       Save
Background

The fast breeder reactor using helium-xenon mixture gas as coolant combined with Brayton thermoelectric conversion system is the development trend of space nuclear power in the future. In order to improve the system efficiency and reduce the system mass, many scholars have carried out research on the design of reactor parameters, but few of them involved helium xenon cooled reactors.

Purpose

This study aims to design key parameters of small helium xenon cooled reactor.

Methods

The single channel model, primary surface regenerator and other component models were built by using FORTRAN 95 language programming, and the thermal system program was established afterward. The basic parameters of submerged subcritical reactor were used to verify the program, and the range of key parameters was determined by sensitivity analysis of a single parameter.

Results

The results show that the regenerator has the greatest influence on the system efficiency and mass, and the pressure ratio of the compressor over 1.52 has less influence on the system mass.

Conclusions

This study provides a reference for the design of small helium xenon cooled reactor.

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The detection of synchronous radiation beam position based on position-sensitive semiconductor optoelectronic devices
Nan MENG,Jianrong ZENG,Zhongliang LI,Fenggang BIAN
Nuclear Techniques    2020, 43 (12): 120102-120102.   DOI: 10.11889/j.0253-3219.2020.hjs.43.120102
Abstract112)   HTML7)    PDF(pc) (2132KB)(58)       Save
Background

In the synchrotron radiation experiment, the position of the beam and the stability of the flux seriously affect the result of experiment. Quantitative evaluation of beam stability is one of key problems in the experiment. It is essential to develop the accurate beam position measurement solution that meets the experimental requirements of the X-ray beams.

Purpose

This study aims to detect beam position for synchrotron radiation X-ray experiments by using position sensitive semiconductor detector (PSD) miniature detector.

Methods

Pin-cushion PSD produced by Hamamatsu company of Japan was adopted for experimental test, and a rectangular beam spot of 5.9 mm×2.0 mm was taken for measurement on BL09B1 beamline of SSRF. When the X-ray beam come into the detector's sensitive region, a current was generated due to photoelectric effect collected by the four electrodes. The location of the incident X-ray beam was determined according to the value of the current given by the galvanometer. In addition, the change of the beam flux was monitored through the total current simultaneously.

Results

Experiment data show that PSD-based miniature detector can meet the needs of synchrotron radiation experiment. For a rectangular spot with a size of 5.9 mm×2.0 mm, the minimum resolution in X and Y direction are 1.5 μm and 1.4 μm, respectively. The signal/noise ratio of PSD detector for beam flux monitoring is more than 4.3×106.

Conclusions

The PSD-based miniature detector can effectively meet the monitoring requirements of spot position, spot size and luminous flux.

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Application of multi-path laser in magnet pre-collimation unit of high energy photon radiation source
Zebin ZHANG, Lingling MEN, Hongbing XIN, Lan DONG, Shang LU, Jing LIANG, Bo LI, Xiaolong WANG, Tao LUO, Tong WANG, Na MA, Zhenqiang HE, Zhiyong KE, Yuanying HAN, Luping YAN
Nuclear Techniques    2021, 44 (1): 10101-010101.   DOI: 10.11889/j.0253-3219.2021.hjs.44.010101
Abstract109)   HTML13)    PDF(pc) (1310KB)(61)       Save
[Background]

The main body of the high energy photon source (HEPS) storage ring contains 288 pre-collimating units. Due to the smaller size of the magnets in the cells, the positioning accuracy of magnets is required to be 3~5 times higher than that in previous projects.

Purpose

This study aims to improve the accuracy of magnet pre-collimation and explore the high measurement accuracy and positioning accuracy of the unit magnet in the pre-collimation experiment.

Methods

The influence of multi-path laser layout schemes on the accuracy of magnetic pre-collimation was firstly simulated by combining the multichannel laser interferometry system with the magnet pre-collimation technology. Then, the simulation software MATLAB was used to optimize the layout scheme of "three high and one low" with the minimum standard deviation of the measured target point as the objective. Finally, four Leica AT960 laser trackers were employed for experimental verification of the measurement accuracy.

Results

The results show that the standard deviation of the measured target point is less than 10 μm in the space range of 12.1 m×5.97 m×3 m, and the measurement accuracy is significantly improved compared with that of a single laser tracker.

Conclusions

The designed project meets the experimental working conditions and design requirements, it lays a foundation for subsequent beam center calibration and magnet calibration.

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Development of a fixed inert gas monitoring device
Changli HU, Wenjia GAI, Cai REN, Juzhi WANG, Hao JIANG, Xinfeng WAN, Chuanbo DAI, Dongqin WANG, Guangzhi SUN
Nuclear Techniques    2020, 43 (10): 100402-100402.   DOI: 10.11889/j.0253-3219.2020.hjs.43.100402
Abstract108)   HTML5)    PDF(pc) (1215KB)(55)       Save
Background

After the Fukushima nuclear accident, China's nuclear power authorities have put forward new requirements for the safety management of nuclear facilities in operation. A variety of radioactive inert gases are produced in nuclear power plant (NPP) accidents.

Purpose

The aims of this study is to develope a special inert gas monitoring device for NPP.

Methods

With the combination of flow gas differential detection component and local processing/display unit, a fixed inert gas monitoring device was developed by integrating the relevant detection device, filter device, gas sensing instrument (flowmeter, pressure gauge), sampling pipeline, valve (stop valve and regulating valve), sampling joint and various components together on this fixed equipment platform. The sensitivity of the detector was predicted by using simulation software MCNP to ensure the satisfaction of requirements.

Results

The fixed inert gas monitoring device developed in this study not only preserves all functionalities, optimizes the measurement index, but also reduces the volume and weight. Compared with the similar equipment, the integrated layout is convenient for maintenance and management with better performance index, smaller volume and lighter weight.

Conclusions

This device canbe employed to monitor the activity concentration of radioactive inert gas in the environment more quickly and accurately, find the leakage of radioactive gas in the nuclear power plant in time, and ensure the safe operation of the nuclear power plant and the radiation safety of the field personnel.

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Preparation of sodium alginate-based super absorbent polymer by radiation grafting and crosslinking
Feng YE,Yu GU,Fei HAN,Xiao XU,Chen HUANG,Lin MA,Renhao DING,Hongjuan MA,Jingye LI
Nuclear Techniques    2020, 43 (12): 120301-120301.   DOI: 10.11889/j.0253-3219.2020.hjs.43.120301
Abstract107)   HTML14)    PDF(pc) (1499KB)(214)       Save
Background

Super absorbent polymer (SAP) is a new type of polymer material. SAP is rich in hydrophilic groups, hence can absorb at least one hundred times of its own volume and swell while keeping the water from losing for a certain period of time.

Purpose

This study aims to synthesize a new SAP for soil and forestry water conservation.

Methods

In this paper, sodium alginate (SA) was used as the raw material, acrylic acid (AA) was used as the monomer, and N,N-methylene bisacrylamide (MBA) was used as the crosslinking agent. SA-g-AA SAP with three-dimensional network structure was prepared by co-radiation grafting. The chemical structures and surface morphologies of the SA-g-AA SAP were characterized by fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis and scanning electron microscope (SEM).

Results

The results showed that when the temperature was 65 ℃, the absorbed dose was 5 kGy, the mass ratio of AA to SA was 5:1, the amount of the crosslinking agent MBA was 1.25 wt%, and the AA neutralization degree was 75%, the maximum water absorption ratio of the SA-g-AA SAP reached 579.8 g?g-1. After the water absorption reused for 7 times, its water absorption ratio maintained 92.5% of the initial value. It showed that the SA-g-AA SAP had good reusability of water absorption performance; after reaching the saturated water absorption ratio, water-retaining property could be retained for up to 15 days, which showed it had good water retention performance.

Conclusions

This SAP material shows potential application in water retention and desertification control.

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Simulation analysis and verification of energy response of space neutron detector
Xuan WEN,Heng AN,Shengsheng YANG,Yi WANG,Siyuan CHANG,Xin GAO,Jun WANG,Chenguang ZHANG,Zhanzu FENG
Nuclear Techniques    2020, 43 (12): 120401-120401.   DOI: 10.11889/j.0253-3219.2020.hjs.43.120401
Abstract107)   HTML4)    PDF(pc) (1816KB)(72)       Save
Background

Space neutrons can cause damage to the electronic systems of orbiting spacecraft and may pose a serious threat to the lives of astronauts on mission.

Purpose

This study aims to accurately analyze the characteristics of the space neutron environment to ensure the reasonable design of spacecraft's anti-radiation reinforcement and the safety of astronauts.

Methods

Monte Carlo method based Fluka software was employed to simulate, analyze and design a composite structure neutron detector based on plastic scintillator. Simulation analysis from the aspects of probe size, structure position, detection efficiency, anti-coincidence structure, etc., was performed to determine the 0.5 mm, 3 mm gradient composite structure of the detector by using 14~25 MeV single energy neutrons for experimental verification.

Results

The simulation and experimental results show that the designed detector can be used for space station cabin neutron environment and near-Earth space neutron detection.

Conclusions

This study provides theoretical and technical support for subsequent engineering load design.

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Nuclear Techniques    2021, 44 (6): 60701-060701.   DOI: 10.11889/j.0253-3219.2021.hjs.44.050402
Abstract107)   HTML10)    PDF(pc) (275KB)(75)       Save
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Design and test of a C band local oscillator and clock device in LLRF
Chengcheng XIAO, Zhe YIN, Junqiang ZHANG, Qiang GU
Nuclear Techniques    2021, 44 (1): 10201-010201.   DOI: 10.11889/j.0253-3219.2021.hjs.44.010201
Abstract106)   HTML6)    PDF(pc) (1784KB)(72)       Save
Background

The linear accelerator of Shanghai soft X-ray free-electron laser facility (SXFEL) operates at 5 712 MHz frequency. In the low level radio frequency (LLRF) system, C band microwave signals were down converted from the 5 686.556 MHz local oscillator (LO) signal to 26.444 MHz intermediate (IM) signal, and then quadruple frequency sampled by the 105.778 MHz clock signal. The stability of LO signal and clock signal can make great influence on the performance of the LLRF system.

Purpose

This study aims to design and manufacture a local oscillator and clock device for satisfying the theoretical design requirements of the LLRF in SXFEL.

Method

The LO signal and clock signal were designed to be auto-correlated with the master oscillator signal. All the functional discrete device modules were installed in a shielded aluminum alloy shell, and were matched and interconnected by RF connectors after debugging and testing separately. The phase jitter integral of clock signal and LO signal, as well as the possible temperature sensitive nonlinear modules, i.e., temperature control of frequency divider and frequency multiplier, in clock Lo equipment were experimentally tested.

Results

The experimental results show that the additional phase jitter integral of LO signal is 21.43 fs, better than the requirement of 40 fs.

Conclusions

The performance of this manufactured LO and clock device can meet the theoretical requirement of the SXFEL.

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Application research of γ energy spectrum analysis based on improved grey wolf algorithm
Wei LIU,Jiankun ZHAO,Yibao LIU,Weicheng LI,Yiqiang XING
Nuclear Techniques    2021, 44 (4): 40204-040204.   DOI: 10.11889/j.0253-3219.2021.hjs.44.040204
Abstract106)   HTML4)    PDF(pc) (2018KB)(62)       Save
Background

Traditional γ energy spectrum analysis methods have the disadvantages of long time, many steps and low accuracy.

Purpose

This study aims to propose an improved gray wolf algorithm based on qualitative analysis to obtain nuclide information faster and more accurately.

Methods

The convergence factor based on the inverted S-curve was adopted in the improved gray wolf algorithm to maintain the balance between the global search and the local search of the algorithm, and solve the problem of local optimum that the original gray wolf algorithm fallen into easily. A dimension-by-dimension update strategy was introduced to improve the accuracy and efficiency of optimization. Finally, this improved gray wolf algorithm was applied to experimental test on the gamma spectra of "Soil standard source" and "Marin cup standard source".

Results

Experimental results show that the improved gray wolf algorithm has a better analysis effect on multi-nuclides mixed gamma spectra. The analysis speed is 59% faster than the original gray wolf algorithm.The analytical error of all nuclides in the soil standard source can be controlled within ±10%. The average absolute error of 8 nuclides is within 4%. Except for 226Ra and 235U in the Marin Cup standard source, the errors of other nuclides are less than 10%. The average absolute error of the 8 nuclides is within 7%.

Conclusions

The improved gray wolf algorithm provides a new method for rapid analysis of nuclides.

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Improvement of subtraction method of gas background in β-γ coincidence spectra analysis
Xinjun ZHANG, Shilian WANG, Huaimao JIA, Qi LI, Jianfang SHI, Yuanqing FAN, Yungang ZHAO
Nuclear Techniques    2020, 43 (11): 110202-110202.   DOI: 10.11889/j.0253-3219.2020.hjs.43.110202
Abstract104)   HTML7)    PDF(pc) (1620KB)(64)       Save
Background

The β-γ coincidence technique is a key method to measure the radioactivity of radioxenon isotopes for comprehensive nuclear-test-ban treaty (CTBT) radionuclide verification. The β-γ coincidence spectrum is usually analyzed by the net count calculation method (NCC) which systematically subtracts gas background from sample spectra regardless of memory effect of the previous sample. Negative net gas background counts are very frequently observed in β-γ coincidence data from International Monitoring System (IMS) radionuclide stations. Gas background subtraction in such cases can potentially lead to overestimated of the activity concentration and even false positives.

Purpose

This study aims to solve the problem of gas background subtraction in NCC.

Methods

First of all, the judgment condition of gas background subtraction was proposed to avoid negative net gas background counts. Then the memory effect of the previous sample was eliminated by modifying the processing flow in NCC algorithm for analyzing β-γ coincidence spectrum. Finally, historical β-γ coincidence data from IMS radionuclide stations were taken for verification of modified NCC and comparison with original NCC.

Results

Comparing the analysis results of original NCC and modified NCC, the false identification number of 131Xem, 133Xem, 133Xe and 135Xe is reduced by 63%, 68%, 72% and 26%, respectively.

Conclusions

The modified NCC algorithm can decrease the positive fault of identification of xenon isotopes and improve the accuracy of calculation of their radioactivity concentration.

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MCNP simulation for gamma-ray buildup factors of shielding material
Tibo YANG,Min WANG,Xinyang FAN,Guanghui LIAO,Guangming DAI
Nuclear Techniques    2021, 44 (3): 30503-030503.   DOI: 10.11889/j.0253-3219.2021.hjs.44.030503
Abstract103)   HTML4)    PDF(pc) (1101KB)(75)       Save
Background

In the shielding design of γ-ray, it is very important to select the appropriate buildup factor for the shielding effect. As far as the current data are concerned, when designing the shielding material, the effect of bremsstrahlung is considered for the single-layer materials, but not for composite materials.

Purpose

This study aims to improve the accuracy of the shielding thickness calculation with the consideration of γ-ray buildup factors by simulation.

Methods

The Monte Carlo method was used to simulate the buildup factors in different γ-ray energies and different shielding material thickness. Buildup factors of single-layer materials and multilayer composite materials were calculated with the consideration of bremsstrahlung and compared with those without bremsstrahlung.

Results

Simulation results show that the contribution of bremsstrahlung to the buildup factor is lower at low energies and thin shielding thicknesses for single-layer materials and composite materials, but it is more obvious at high energies and high shielding thicknesses. The buildup factors show a decreasing trend with the increase of γ-ray energy, and show an increasing trend with the increase of shielding thickness.

Conclusions

This study provides a reference and calculation method for the buildup factor for shielding design of high-energy γ-ray in actual situations.

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Numerical simulation of the effect of ripple and neoclassical tearing mode on tokamak particle transport
Jin LIU,Jiaying CHEN,Yueyue CHANG,Yan ZHAN,Limin YU
Nuclear Techniques    2021, 44 (2): 20201-020201.   DOI: 10.11889/j.0253-3219.2021.hjs.44.020201
Abstract103)   HTML13)    PDF(pc) (2686KB)(96)       Save
Background

Tokamak is a possible implementation of controlled nuclear fusion whilst the particle transportation plays an important role in maintaining the progress of nuclear fusion reactions.

Purpose

This study aims to investigate the effects of ripple field and neoclassical tearing mode (NTM) on the migration of deuterium ions in Tokamak by numerical simulation. and provide a reference for the confinement of high energy particles.

Methods

The guiding center orbit code ORBIT was employed for numerical simulation. Effects of NTM and ripple field on particles with different positions, pitch angles and energies, were studied in details.

Results & Conclusions

Simulation results show that the particle loss rate is high under the condition of high magnetic surface and low pitch angle. NTM mainly causes the loss of passing particles, while the loss of trapped particles is mainly caused by ripple field. When both perturbations are considered, the loss of particles is approximately the sum of losses by two perturbations acting alone. Ripple field will significantly increase toroidal angular momentum diffusion of trapped particles without affecting the passing particles, whilst NTM mainly influences toroidal angular momentum diffusion of passing particles. The particle loss situation basically keeps the original characteristics regardless of NTM frequency varition, while the momentum diffusion condition of particle loss changes with the increase of NTM frequency.

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Study on thorium utilization and conversion in 2 MW liquid molten salt reactor
Peng CHEN, Bo ZHOU, Rui YAN, Yang ZOU
Nuclear Techniques    2020, 43 (10): 100602-100602.   DOI: 10.11889/j.0253-3219.2020.hjs.43.100602
Abstract96)   HTML9)    PDF(pc) (1889KB)(45)       Save
Background

Thorium-uranium fuel cycle has the advantages of making use of abundant thorium resources, producing less nuclear waste and low toxicity, as well as nuclear non-proliferation. Molten salt reactor is an ideal type of nuclear energy utilization of thorium resources. The amount of thorium added in the core fuel can affect the thorium-uranium conversion performance in the molten salt reactor.

Purpose

This study aims to understand the effect of thorium addition on the conversion performance of thorium and uranium in molten salt reactor.

Methods

Based on MCNP (Monte Carlo N Particle Transport Code) program, the core physical model was established. The neutron physical characteristics and thorium-uranium conversion characteristics of 2 MW (thermal power) liquid fuel experimental reactor under different thorium additions running at full power for 300 days were analyzed by using MOBAT (burnup code coupled with MCNP and ORIGEN2 using BATch language) burnup program. Analysis objectives included the energy spectrum changes at the beginning and the end of burnup, Xe equilibrium, as well as the consumption ratio and transfer characteristics, and the evolution of important nuclides in thorium uranium chain.

Results

The results show that the consumption rate of thorium decreases with the increase of added amount. CR raises with the increase of Thorium addition, but the growth rate decrease gradually. The rate at which 233Th concentration reaches the maximum value is linearly related to the thorium mass, and the 233Pa has the same evolution trend as the 233Th. The higher the thorium content in the fuel, the higher the concentration of 233U, and the accumulation of 233U increases with the running time. Based on the radiochemical detection limit, 80 kg thorium can meet the minimum detection value after 4 days.

Conclusions

Based on the data of thorium-uranium conversion, the amount of uranium fuel needed to maintain the back-up reactivity, the limit of radiochemical detection and other factors, the experimental reactor can carry out the utilization of thorium in the order of tens to hundreds of kilograms and the verification experiment of Thorium-Uranium cycle, with the priority of about 80 kg. In addition, the more thorium was added, the more Uranium needed to be added. The increase of 135I concentration will increase the equilibrium concentration of Xe. The more thorium is added, the harder the neutron spectrum and the higher the 233U output will be, which means that it is easier to achieve transformation or proliferation under the fast neutron spectrum.

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Design of beam homogenization for ground simulation of space electron environment
Changqiang WANG,Yihuai XIANG,Jinhai LI,Jinghe YANG
Nuclear Techniques    2020, 43 (12): 120201-120201.   DOI: 10.11889/j.0253-3219.2020.hjs.43.120201
Abstract96)   HTML4)    PDF(pc) (2352KB)(55)       Save
Background

The effect of high-energy electrons bombardment on the integrated circuit (IC) for aerospace can be studied by the simulated space electron environment device on the ground. In the device, the high-energy electrons are provided by the electron linear accelerator, and the output beam spot is only on the order of millimeters while the experiment requires a large-area uniform electron irradiation area.

Purpose

This study aims to process the beam transmission line to meet irradiation area and uniformity requirements of short beam transmission line and large irradiation area.

Methods

Two-dimensional homogenized beam expansion scheme was designed with the combination of beam expansion and scanning. According to the beam parameters output by the linear accelerator, the solenoid, α-magnet, scanning magnet, quadrupole magnets, focus sextuple magnet and other beam transmission line elements were taken into consideration simultaneously. By adjusting the element parameters through the electron beam tracking code, the electron beam with different energies of 0.5 MeV, 2.5 MeV and 5 MeV were matched with the required irradiation area and uniformity on the irradiation plane.

Results

Simulation results show that the beam uniformities in different irradiation areas for 0.5 MeV, 2.5 MeV and 5 MeV beamline are better than 90%.

Conclusions

The beam homogenization design proposed in this study for ground simulation of space electron environment meets the requirement of effect of high-energy electrons bombardment in extraterrestrial space.

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Simulation study of secondary neutron reflection distribution in proton therapy room
Xiang LI,Yunan GAO,Han GAO,Congchong YAN,Wei TANG,Liang SUN
Nuclear Techniques    2021, 44 (2): 20203-020203.   DOI: 10.11889/j.0253-3219.2021.hjs.44.020203
Abstract96)   HTML5)    PDF(pc) (1175KB)(45)       Save
Background

The protection of secondary neutrons in the complex secondary radiation of the 100~250 MeV proton therapy room has always been the focus of shielding design. Currently, iron plates embedded in concrete are often used to reduce neutron transmission, but this will cause significant neutron reflection (toward the patient). And neutrons have a high radiation weighting factor which may cause harmful effects on patients.

Purpose

The study aims to investigate the reflection distribution of secondary neutrons in the proton therapy room and its impact on patients.

Methods

First of all, a simple model of the proton therapy room was established, and Monte Carlo program FLUKA was used to calculate the effects of the secondary neutron reflection from different directions and at different embedding positions of the iron shield in the 245 MeV proton therapy room. Then, under the three irradiation modes of AP (Antero-posterior), PA (Posterior-anterior) and LAT (Lateral), the effective dose of the patient was calculated according to the energy of the reflected neutrons reaching the position of the patient whilst the neutron external radiation dose conversion coefficient given in report of ICPR (International Commission on Radiological Protection) Publication 116 was used.

Results

The simulation results show that the main shielding wall contributes more than 95% to the reflection distribution of the secondary neutrons in the treatment room. The radiation dose level outside the treatment room is the lowest when the embedded depth of the iron plate in the wall is 0 (the iron plate is exposed in the room), but highest effective dose rates caused by reflected neutrons are 1.99 μSv?s-1, 1.37 μSv?s-1 and 1.00 μSv?s-1, respectively, under the three irradiation modes of AP, PA and LAT. With the increase of embedding depth of iron plate, the effective dose rate of reflected neutron decreased gradually, but the decreasing trend becomes slower and slower.

Conclusions

The structure of the main shielding wall of the treatment room and the embedded position of the iron plate have a significant impact on the reflected secondary neutron energy spectrum and the patient's radiation health. This feature needs to be considered in the shielding design of the proton therapy room.

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Development and application of control limits of derived air concentration for tritium
Youpeng WU,Weiwei WEN,Jinxing CHENG,Qingbo WANG,Ai YU,Xin GAO,Zhiqiang GENG
Nuclear Techniques    2021, 44 (2): 20602-020602.   DOI: 10.11889/j.0253-3219.2021.hjs.44.020602
Abstract96)   HTML4)    PDF(pc) (939KB)(85)       Save
Background

Tritium is one of the radionuclides released during the operation of nuclear facilities. The radiation hazard of tritium to human body is internal exposure, which is not only related to the activity of tritium, but also closely related to the chemical form and intake route of tritium. In view of the current standards involving tritium, there is an inconsistency in the control limit of tritiated water (HTO), as well as elemental tritium (HT).

Purpose

This study aims to derive and standardize the concentration limits of HTO and HT, as well as the discharge activity concentration limits of HTO.

Methods

The development of tritium concentration control limits and the basis for the formulation of relevant standards were analyzed. According to the current radiation protection standards of China, combined with the latest biodosimetry parameters of tritium in publications of International Atomic Energy Agency (IAEA) and International Commission on Radiological Protection (ICRP), the control limits of derived air concentration (DAC) and water activity concentration for tritium were recalculated. When calculating the recommended limit of air concentration derived from HTO, the skin absorption was converted into the inhalation, and the complete skin absorption was set to half of the inhalation.

Results

Since the dose conversion coefficient used in the current standard is close to that in the new international publications, the recommended limits of HTO are slightly smaller than that specified in the standard, and the corresponding values are basically in the same order of magnitude.

Conclusions

The derived results can provide reference for the standard formulation of radiation protection management. The applicable objects of control limits are also clearly exhibited and distinguished. These objects are only available for people, not for facilities or equipment.

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Role of Ptnc-FeOxmetal-oxide interface in enhancing the catalytic activity for CO oxidation
Chengyong LIU, Li HUANG, Xueyang SONG, Wenxue HE, Siyu WANG, Zhixin LONG, Zhihu SUN, Shiqiang WEI
Nuclear Techniques    2021, 44 (1): 10103-010103.   DOI: 10.11889/j.0253-3219.2021.hjs.44.010103
Abstract96)   HTML12)    PDF(pc) (2177KB)(58)       Save
Background

Metal-oxide interface plays critical roles in promoting the catalytic activities of metal catalysts in a vast diversity of reactions. Maximizing this interfacial interaction so as to optimize the catalytic performance is an active subject of research that is worthy of intensive exploration.

Purpose

This study aims to develop new Pt-group catalysts that are highly active towards cryogenic CO catalytic oxidation, and explore effective strategies to engineer metal-oxide (hydroxide) interfaces to weaken the adsorption of CO and to enhance the adsorption/activation of O2.

Methods

Supported ultrasmall Pt nanoclusters (Ptnc-FeOx/SiO2) of (1.4±0.2) nm were synthesized using deposition-precipitation with urea (DPU). The catalytic performance towards CO oxidation was examined by using a fixed-bed U-shape flow quartz reactor. Extended X-ray absorption fine structure (EXAFS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and energy-dispersive X-ray spectroscopy (EDX) techniques were combined to study the Ptnc-FeOx interfacial interaction.

Results

The Ptnc-FeOx/SiO2 catalyst shows superior catalytic performance than Pt/SiO2 towards the CO oxidation reaction. Kinetics tests show that both the apparent activation energy and turnover frequency of Ptnc-FeOx/SiO2 are greatly enhanced as compared with Pt/SiO2 (19 kJ·mol-1 vs. 64 kJ·mol-1; 0.044 s-1 vs. 0.002 s-1 at 37 °C).

Conclusion

The charge transfer from Fe to Pt results in the downshifted d-band center of Pt and reduces the CO adsorption strength, and hence, playing important roles in promoting the catalytic activity of Pt catalysts.

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The transient analysis of molten salt reactor reactivity insertion based on RELAP5/FLUENT coupled program
Fan HE,Xiangzhou CAI,Wei GUO,Long HE,Lei CUI
Nuclear Techniques    2021, 44 (3): 30601-030601.   DOI: 10.11889/j.0253-3219.2021.hjs.44.030601
Abstract96)   HTML8)    PDF(pc) (2044KB)(69)       Save
Background

Molten salt reactor (MSR) is an ideal advanced reactor with good neutron economy, inherent safety and online refuelling.

Purpose

This study aims to evaluate the transient behavior of reactive insertion transients of MSR.

Methods

Based on the RELAP5/FLUENT coupling program and the establishment of the primary circuit model, the graphite-moderated channel type molten salt reactor was studied, and transient analysis was conducted when the reactor core was inserted with 0.000 1, 0.000 2, and 0.000 5 reactivities.

Results

The results show that under the concerned reactivity insertion, the maximum temperature of the reactor core and the outlet temperature of the salt are both lower than the safety allowable limit due to the negative temperature reactivity of the reactor core.

Conclusions

This study verifies the good response ability of MSR to reactivity insertion events.

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