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15 October 2020, Volume 43 Issue 10 Previous Issue   
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SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS
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
Abstract ( 18 )   HTML ( 4 )   PDF(pc) (1227KB) ( 11 )   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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ACCELERATOR, RAY TECHNOLOGY AND APPLICATIONS
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
Abstract ( 26 )   HTML ( 1 )   PDF(pc) (2206KB) ( 28 )   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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Research on two-measurement position helical gamma scanning technology
Xinhai TANG, Weiguo GU, Hui YANG, Dezhong WANG
Nuclear Techniques. 2020, 43 (10):  100202-100202.  DOI: 10.11889/j.0253-3219.2020.hjs.43.100202
Abstract ( 11 )   HTML ( 1 )   PDF(pc) (1339KB) ( 6 )   Save
Background

Helical gamma scanning (HGS) is one of non-destructive assay (NDA) for the measurement of radioactive waste drum. However, the accuracy of HGS in measuring the heterogeneous radioactive waste is poor.

Purpose

This study aims to evaluate the performance of two-measurement position helical gamma scanning (THGS) for a 400-liter high density waste drum.

Methods

On the basis of HGS, THGS adds eccentric helical scanning measurement. The equivalent radius of the radioactive source in the waste drum was determined by the ratio of the counting rate of the two positions. Finally, the activity of the radioactive source was reconstructed. The reconstruction process of three radionuclides in 400-liter waste drum was simulated by numerical calculation method to verify the accuracy of THGS.

Results

For a single line source in high density 400-liter waste drum, the maximum reconstruction error of HGS is more than 400%, while that of THGS is less than 50%. When two detectors are used, the measurement time of THGS is the same as that of HGS.

Conclusions

THGS is suitable for measuring 400 L-waste drum whose density is high.

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NUCLEAR ELECTRONICS AND INSTRUMENTATION
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
Abstract ( 24 )   HTML ( 1 )   PDF(pc) (1070KB) ( 8 )   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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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
Abstract ( 20 )   HTML ( 1 )   PDF(pc) (1215KB) ( 16 )   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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NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH
Detection technology and design analysis of LET spectrum of space radiation particles
Heng AN, Xuan WEN, Detian LI, Yi LI Cunhui WANG, Shengsheng YANG, Xiaogang WANG Jun QIN, Chenguang ZHANG, Zhou CAO
Nuclear Techniques. 2020, 43 (10):  100501-100501.  DOI: 10.11889/j.0253-3219.2020.hjs.43.100501
Abstract ( 12 )   HTML ( 1 )   PDF(pc) (2049KB) ( 4 )   Save
Background

Accurate detection of the linear energy transfer (LET) spectrum of space radiation particles plays an important role in long-term space missions, such as the moon landing plan and the space station operation.

Purpose

This study aims to obtain effective parameters such as dose equivalent through real-time monitoring of the LET spectrum of space radiation particles, providing powerful data input for the safety of astronauts in manned space missions and the accurate prediction of space weather changes.

Methods

Based on the LET spectrum of heavy ions in semiconductor materials and the simulation analysis data, detection technology and design analysis of LET spectrum of space radiation particles were carried out. A multi-stack telescope structure detector based on silicon micro strip semiconductor with multi-layer stack was designed to detect the LET spectrum in the range of 0.01~100 MeV·cm2·mg-1.

Results & Conclusions

This design of LET spectrum detector can provide technical reference for the design and development of particle detection load in the follow-up space station and moon landing mission, and can also provide necessary data input for the safety early warning of spacecraft in orbit.

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Simulation analysis of hydrogen isotope separation in graphene solid polymer electrolyte electrolysis
Fei WEI, Fangdong TANG, Jiayu LIU, Zhiwei XIN, Youshi ZENG, Xinxin CHU, Wei LIU
Nuclear Techniques. 2020, 43 (10):  100502-100502.  DOI: 10.11889/j.0253-3219.2020.hjs.43.100502
Abstract ( 8 )   HTML ( 0 )   PDF(pc) (2149KB) ( 5 )   Save
Background

As a new type of high-selective permeable membrane material, graphene is expected to improve the separation effect of solid polymer electrolyte electrolysis (SPE) on hydrogen isotopes.

Purpose

In this study, graphene was combined with the proton exchange membrane in SPE electrolysis to explore the effect of its separation performance for hydrogen isotopes.

Methods

Based on the B3LYP/6-31G (d) theory, quantum chemistry calculation software Gaussian 09 was used to calculate the penetration barrier of the graphene model to protons. At the same time, the effect of zero-point vibrational energy was taken into account to obtain the separation coefficient of graphene for hydrogen isotope ions.

Results

The computation results of the separation coefficients of H+/D+ and H+/T+ are 12.4 and 37.5, respectively, at room temperature (293 K). The research resultants indicate that the optimized model structure and the presence of different types of defects reduce the penetration barrier of protons, the existence of Stone-Wales defect does improve the separation performance.

Conclusions

Graphene can be used to effectively improve the separation coefficient of hydrogen isotopes in SPE electrolysis, which is expected to promote the establishment of truly efficient hydrogen isotope separation technology.

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NUCLEAR ENERGY SCIENCE AND ENGINEERING
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
Abstract ( 24 )   HTML ( 3 )   PDF(pc) (2218KB) ( 31 )   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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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
Abstract ( 25 )   HTML ( 4 )   PDF(pc) (1889KB) ( 8 )   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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Electromagnetic-structure coupling analysis of EDPP for CFETR under multiple electromagnetic conditions
Kun PEI, Ming WANG, Mingxuan LU, Kun LU
Nuclear Techniques. 2020, 43 (10):  100603-100603.  DOI: 10.11889/j.0253-3219.2020.hjs.43.100603
Abstract ( 11 )   HTML ( 0 )   PDF(pc) (1484KB) ( 2 )   Save
Background

China fusion engineering test reactor (CFETR), a fully superconducting tokamak device designed and developed in China, aims to solve the physical and engineering problems between international thermonuclear experimental reactor (ITER) and the DEMO. The diagnostic port plug is a key part of the CFETR device and its internal diagnostic system can realize the monitoring and feedback control of the device's operating parameters. As the diagnosis port plug is close to the plasma area, the huge electromagnetic (EM) load induced on this component during the plasma disruption will affect the stability of the device structure.

Purpose

This study aims to analyze the EM load on equatorial diagnostic port plug (EDPP) under different EM conditions.

Methods

First of all, the conceptual design of EDPP was completed according to the requirements of CFETR diagnostic system. Then, the EM loads of 10 MA plasma under linear and exponential conditions were evaluated using the commercial finite element analysis software ANSYS. Finally, the effects of the integrated and distributed scheme designs on the EM load distribution of the EDPP were discussed.

Results & Conclusions

The results show that the maximum stress generated on the EDPP with an integrated or distributed design are both less than 10 MPa, which meets the design requirements. In addition, the maximum EM load on the EDPP shows that the plasma linear disruption is greater than the exponential disruption.

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Analysis of breeding performance for thorium-based gas-cooled fast reactor started by 233U and 239Pu
Dong HAN, Chunyan ZOU, Xiangzhou CAI, Jingen CHEN
Nuclear Techniques. 2020, 43 (10):  100604-100604.  DOI: 10.11889/j.0253-3219.2020.hjs.43.100604
Abstract ( 17 )   HTML ( 1 )   PDF(pc) (1203KB) ( 10 )   Save
Background

As one of the reactor types selected by the fourth generation nuclear energy system international forum, gas-cooled fast reactor has the advantages of high temperature gas cooled reactor and fast reactor, with high breeding rate and short fuel-doubling time.

Purpose

This study aims to analyse the neutronic characteristics of different fissile nuclides in operation using the TRITON module in SCALE6.1.

Methods

Firstly, the changes of breeding rate and fissionable nuclides with burnup were analyzed. The breeding performance of fissionable nuclides was weighted according to the characteristics of gas-cooled fast reactor. Then, the difference of doubling time between two different evaluation methods of breeding rate and weighted breeding gain were compared. Finally, the doubling time was optimized by using an equivalent start-up method.

Results & Conclusions

The results show that the analysis of the doubling time of different fissionable nuclides using weighted breeding gain and equivalent elimination mass difference can describe the breeding characteristics of fast reactors more accurately, providing a reference for the refueling scheme of thorium-based gas-cooled fast reactor.

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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
Abstract ( 16 )   HTML ( 1 )   PDF(pc) (1069KB) ( 16 )   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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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
Abstract414)      PDF(pc) (6093KB)(6165)       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
Abstract204)      PDF(pc) (1792KB)(4803)       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
Abstract406)      PDF(pc) (1625KB)(3492)       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)
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
Abstract438)      PDF(pc) (1946KB)(3250)       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)
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
Abstract473)      PDF(pc) (677KB)(3001)       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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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
Abstract351)      PDF(pc) (1225KB)(2947)       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)
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
Abstract497)      PDF(pc) (1714KB)(2756)       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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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
Abstract1035)      PDF(pc) (1146KB)(2748)       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(8)
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
Abstract658)      PDF(pc) (913KB)(2678)       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
Abstract432)      PDF(pc) (1105KB)(2642)       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)
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
Abstract412)      PDF(pc) (1953KB)(2475)       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
Abstract891)      PDF(pc) (2109KB)(2428)       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
Abstract418)      PDF(pc) (1691KB)(2415)       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)
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
Abstract491)      PDF(pc) (473KB)(2406)       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)
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
Abstract543)      PDF(pc) (1612KB)(2401)       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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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
Abstract465)      PDF(pc) (569KB)(2376)       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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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
Abstract457)      PDF(pc) (732KB)(2368)       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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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
Abstract289)      PDF(pc) (273KB)(2362)       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)
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
Abstract524)      PDF(pc) (784KB)(2341)       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)
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
Abstract430)      PDF(pc) (2256KB)(2297)       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
Abstract456)      PDF(pc) (579KB)(2250)       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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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
Abstract440)      PDF(pc) (1674KB)(2245)       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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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
Abstract310)      PDF(pc) (1384KB)(2221)       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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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
Abstract459)      PDF(pc) (658KB)(2218)       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(8)
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
Abstract240)      PDF(pc) (5349KB)(2201)       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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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
Abstract546)      PDF(pc) (704KB)(2188)       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)
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
Abstract749)      PDF(pc) (911KB)(2162)       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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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
Abstract247)      PDF(pc) (3938KB)(2149)       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)
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
Abstract799)      PDF(pc) (716KB)(2130)       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)
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
Abstract618)      PDF(pc) (4976KB)(2097)       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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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
Abstract356)      PDF(pc) (1552KB)(2096)       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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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
Abstract338)      PDF(pc) (3229KB)(2073)       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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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
Abstract418)      PDF(pc) (2008KB)(2069)       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(8)
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
Abstract433)      PDF(pc) (5036KB)(2063)       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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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
Abstract457)      PDF(pc) (1254KB)(2025)       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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Impact of dust storm on chemical species of S, Cl and Ca in Shanghai atmosphere particles
LONG Shilei, LIU Ke, ZENG Jianrong, CAO Lingling, BAO Liangman, LIN Jun, LI Yan, MA Chenyan
Nuclear Techniques    2013, 36 (10): 100101-100101.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.100101
Abstract218)      PDF(pc) (2372KB)(2018)       Save

Background: Dust storm originated from the northwest region of China brought dust particles for Shanghai every spring, which resulted in serious particulate pollution. However, the studies of the impact of dust storm on the Shanghai atmospheric aerosols were limited to the concentrations of ions and elements. It is considered that the chemical species of atmospheric aerosols were much more necessary for the evaluation of the impact of dust storm on the particulate pollution in Shanghai. Purpose: Based on the elements concentration variations, backward trajectories of air masses and chlorine, calcium, sulfur species in aerosols during the dust event, the impact of dust storm on the chemical species of aerosols in Shanghai was studied. Methods: Elements concentrations of the samples were analyzed by X-ray fluorescence (XRF) based on synchrotron radiation. To identify the potential importance of different source regions on aerosol composition during dust events, the air mass trajectories were calculated by using the model HYSPLIT version 4 developed by NOAA/ARL. Chemical species of S, Cl, Ca were analyzed by synchrotron radiation X-ray absorption near edge structure (XANES). Sulfur K-edge XANES is capable of distinguishing various sulfate species in a non-destructive way and we used linear combination fitting procedure to quantify the concentrations of sulfate species in PM. Results: Elements concentration variations during the dust storm period showed that crust elements (Si, Al, Ca, K, Mg, Fe, Ti) in particles increased substantially during dust storm. However, pollution elements (S, Zn, Pb, Cu, V, Cr, As) from local region decreased by the clean effect of dust storm. Combined XANES of S, Cl, Ca in particulate samples with backward trajectories, the possible sources and reasons of their chemical species were studied. During dust storm, sulfur mainly existed as CaSO4?2H2O, Cl existed as organic chloride and Cl?, Ca existed as CaCO3. In the samples of other days, sulfur was mainly existed as (NH4)2SO4, Cl existed as organic chloride and Ca existed as Gypsum. The source of Cl? was sea salts which brought by dust storm along the way. Gypsum (CaSO4?2H2O) was formed in the reactions of CaCO3 and SO42? during the transportation. Conclusion: It is shown that synchrotron radiation XANES is a powerful tool to identify chlorine, calcium and especially sulfur species in aerosol samples. Dust storm not only transported amount of crust particles but also brought particles along the way to atmosphere environment in Shanghai. During the transportation, dust particles could chemically react with the pollution particles of the local region.

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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
Abstract342)      PDF(pc) (905KB)(2007)       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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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
Abstract301)      PDF(pc) (1144KB)(1994)       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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Synthesis of Dumbbell-like Au nanostructure and its light-absorbance study  
SHEN Jianlei, XU Yan, LI Kun, SONG Shiping, FAN Chunhai
Nuclear Techniques    2013, 36 (6): 60501-060501.   DOI: DOI: 10.11889/j.0253-3219.2013.hjs.36.060501
Abstract248)      PDF(pc) (9293KB)(1987)       Save

Background: By changing the size or the morphology of Au nanostructures, they can absorb different wavelength light due to the localized surface plasmon resonance (LSPR). Because Au nanorods show good ability to transform light into heat (photothermal effect), they have been wildly used to deliver the drugs and release them controllably. However, when applying such nanostructures for in vivo treatments, Au nanorods must have long aspect ratio which often make it hard to prepare heterogeneous nanostructures. Purpose: A new method to synthesize Au nanostructures with uniform size and to achieve long wavelength light absorbance is needed. This work attempts to synthesize such Au nanostructures by using bio-nano techniques. Methods: New nanostructures are prepared by growing Au nanoparticles on the surface of Au nanorods modified with DNA molecules. Results: Dumbbell-like Au nanostructures were prepared firstly. Its maximum absorbance locates at near ultraviolet region, which means that it can be used as a potential tool for the deep-skin photothermal treatment. Moreover, other two kinds of nanostructures, i.e. Au nanorods with Au splinter at two ends and sea urchin-like nanostructures, are also studied. Conclusions: We successfully fabricated novel Au nanostructures which can be used for drug delivery, surface-enhanced Raman spectroscopy and catalysis.

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Preparation of AFG90-H epoxy resin-based temperature-resistant neutron shielding composite
JIANG Yifeng, LUAN Weiling, ZHANG Xiaoni, HAN Yanlong, SUN Ke
Nuclear Techniques    2015, 38 (12): 120202-120202.   DOI: 10.11889/j.0253-3219.2015.hjs.38.120202
Abstract408)      PDF(pc) (782KB)(1948)       Save
Background: The corrosive, highly radioactive and humid-hot environment in nuclear power plant requires an overall performance for neutron shielding material. Purpose: This study aims to develop a new type of AFG90-H epoxy resin-based neutron shielding composite which would tolerate high temperature in a complex environment. Methods: The preparation of the composite materials is doped functional particles into the epoxy resin matrix, and the composite was tested for its radiation resistance, high temperature mechanical properties, neutron shielding and corrosion resistance. Results: In the 42-kGy radiation environment, with the glass transition temperature reaching 262 oC, the bending strength of the composite declined by only 1.63%, which showed better neutron shielding performance than common materials such as high density polyethylene (HDPE), paraffin and 6002 epoxy resin (EP). By adding the B4C particles, the neutron shielding performance and temperature mechanical properties of the composite were improved greatly, and the corrosion resistance performance did not degrade. Conclusion: Due to its excellent performance in temperature, corrosion and radiation resistance, as well as its low density, this composite could be used as the neutron shielding layer for mobile detection equipment.
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Electron ion collider in China
Xu CAO, Lei CHANG, Ningbo CHANG, Xurong CHEN, Zhuojun CHEN, Zhufang CUI, Lingyun DAI, Weitian DENG, Minghui DING, Chang GONG, Longcheng GUI, Fengkun GUO, Chengdong HAN, Jun HE, Hongxia HUANG, Yin HUANG, Kaptari L P, Demin LI, Hengne LI, Minxiang LI, Xueqian LI, Yutie LIANG, Zuotang LIANG, Guoming LIU, Jie LIU, Liuming LIU, Xiang LIU, Xiaofeng LUO, Zhun LYU, Boqiang MA, Fu MA, Jianping MA, Yugang MA, Lijun MAO, Mezrag C, Jialun PING, Sixue QIN, Hang REN, Roberts C D, Guodong SHEN, Chao SHI, Qintao SONG, Hao SUN, Enke WANG, Fan WANG, Qian WANG, Rong WANG, Ruiru WANG, Taofeng WANG, Wei WANG, Xiaoyu WANG, Xiaoyun WANG, Jiajun WU, Xinggang WU, Bowen XIAO, Guoqing XIAO, Jujun XIE, Yaping XIE, Hongxi XING, Hushan XU, Nu XU, Shusheng XU, Wenbiao YAN, Wencheng YAN, Xinhu YAN, Jiancheng YANG, Yi-Bo YANG, Zhi YANG, Deliang YAO, Peilin YIN, Wenlong ZHAN, Jianhui ZHANG, Jinlong ZHANG, Pengming ZHANG, Chao-Hsi CHANG, Zhenyu ZHANG, Hongwei ZHAO, Kuang-Ta CHAO, Qiang ZHAO, Yuxiang ZHAO, Zhengguo ZHAO, Liang ZHENG, Jian ZHOU, Xiang ZHOU, Xiaorong ZHOU, Bingsong ZOU, Liping ZOU
Nuclear Techniques    2020, 43 (2): 20001-020001.   DOI: 10.11889/j.0253-3219.2020.hjs.43.020001
Abstract1345)   HTML93)    PDF(pc) (5822KB)(879)       Save

Lepton scattering is an established ideal tool for studying inner structure of microscopic particles such as nucleons as well as nuclei. As a future high energy nuclear physics project, an Electron-ion collider in China (EicC) has been proposed. It will be constructed based on an upgraded heavy-ion accelerator, High intensity heavy-ion accelerator facility (HIAF) which is currently under construction, together with an additional electron ring. The proposed collider will provide highly polarized electrons (with the polarization ~80%), protons and Helium-3 (both with the polarization ~70%), as well as unpolarized ion beams from carbon to uranium with viable center of mass energy from 15 GeV to 20 GeV and the luminosity of (2~4)×1033 cm-2?s-1. The main foci of the EicC will be the precision measurements of proton structure in the sea quark region, including 3D tomography of nucleon; the partonic structure of nuclei and the parton interaction with the nuclear environment, in particular, the short range correlation of nucleons and the cold nuclear matter effects; the exotic hadronic states, especially those with heavy flavor quark contents. In addition, issues fundamental to understanding the origin of mass could be addressed by measurements of heavy quarkonia near-threshold production at the EicC. In order to achieve the above-mentioned physics goals, a hermetical detector system will be constructed with the cutting-edge technology. During preparation of the document, we have received valuable inputs and help from experts across the globe. The EicC physics program complements the ongoing scientific programs at the Jefferson Laboratory and the future EIC project in the United States. The success of this project will also advance both nuclear and hadron physics as well as accelerator and detector technology in China.

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Study on polarized γ beam properties of a new LCS light source based on SXFEL
Junwen WANG, Gongtao FAN, Hongwei WANG, Yugang MA, Guilin ZHANG, Longxiang LIU, Yue ZHANG, Xinrong HU, Xinxiang LI, Zirui HAO
Nuclear Techniques    2019, 42 (12): 120201-120201.   DOI: 10.11889/j.0253-3219.2019.hjs.42.120201
Abstract178)   HTML4)    PDF(pc) (979KB)(41)       Save
Background

Back Compton scattering (BCS) as a photon acceleration mechanism, has gained more attention and application in recent years.

Purpose

This study aims to investiage the polarized gamma beam characteristics of laser Compton scattering (LCS) gamma source based on the soft X-ray free electron laser (SXFEL).

Methods

The numerical simulation method was employed to study the beam properties of LCS source based on SXFEL. Characteristics of its energy, flux, polarization and quasi single energy were analysed in details.

Results

The results show that the LCS gamma source has the advantages of high energy, high flux, high polarization and monoenergetic beam. The gamma ray energy can be changed continuously between 1 MeV and 80 MeV by adjusting the electron energy and the laser wavelength. With a collimator gamma energy resolution will reach ≤4%. Most importantly, the gamma rays are nearly 100% polarized and the polarized gamma beam spot is affected by the laser polarization properties.

Conclusions

The calculation shows that the LCS gamma source at SXFEL will be a high quality gamma facility with high energy resolution and high degree of polarization.

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Preliminary design of modularized lead cooled small reactor
Huiwen XIAO, Xiang LI, Guoming LIU, Youqi ZHENG
Nuclear Techniques    2020, 43 (8): 80001-080001.   DOI: 10.11889/j.0253-3219.2020.hjs.43.080001
Abstract157)   HTML5)    PDF(pc) (2356KB)(54)       Save
Background

As the coolant of the reactor, lead and lead-based alloy has excellent thermal properties. Developing lead cooled reactor attracts has been practicing with major investment in many countries, such as European union countries, Russia, Korea, Japan, China and so on.

Purpose

This study aims at the preliminary design of modularized lead cooled small reactor.

Methods

First of all, the neutron transport, depletion, reaction coefficient and kinetic parameters were calculated by using SARAX, a fast reactor neutronics calculation software developed by Xi’an Jiaotong University. High enrichment fuel was adopt for compact light-weight, and two different enrichment fuel was chosen to flat the power distribution. Two group control rods and one group of emergency shutdown rods were placed in the core to satisfy the requirement of reactivity and emergency shutdown. The B4C with good absorbing capacity in fast and thermal energy region was used as the neutron absorb material of control rods while tungsten with high density and excellent neutron absorb capacity was mixed with B4C as the neutron absorber material of the emergency shutdown rods. Then neutronics parameters of reactor core were calculated from the beginning of full power operation to the whole life cycle.

Results

The calculation results show that the 6EFPY life length of this design is achieved, mass of actinide elements decreases and mass of 239Pu was increases apparently. Important reactivity feedback coefficients, such as coolant density coefficient, coolant void value and expansion coefficient are negative, and the value of control rods and safety rods are enough to shutdown reactor in the whole life cycle. Highest clad temperature and fuel center temperature, line power density are within allowed limits.

Conclusions

The main neutronics parameters in the whole life cycle of this preliminary design meet the safety requirements.

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A survey of heatpipe space nuclear reactor power supply
Ao WANG, Fengyang SHEN, Gu HU, Jian AN Weijian GUO
Nuclear Techniques    2020, 43 (6): 60002-060002.   DOI: 10.11889/j.0253-3219.2020.hjs.43.060002
Abstract139)   HTML8)    PDF(pc) (790KB)(92)       Save
Background

With the in-depth exploration of space, the power supply requirements for energy supply are gradually increasing. Space nuclear reactor power supply stands out in the deep space exploration mission due to its advantages of passivity, long life and high reliability, hence heat pipe nuclear reactor has become the focus of research in the field of space nuclear reactor.

Purpose

This study aims to evaluate the progress and technology of heat pipe space nuclear reactor used as power supply.

Method

First of all, the conceptual design of heatpipe reactor in the early stage and its application in Kilopower was summarized. Then the details of heatpipe power system (HPS), the heatpipe-operated mars exploration reactor (HOMER), safe affordable fission engine (SAFE) and Kilopower were investigated with emphasis on the structure design, fuel selection, heatpipe arrangement and power design of each reactor.

Results

This survey provides ideas and references for future research and design of heatpipe space nuclear reactor power system.

Conclusions

The design of heatpipe reactor is highly flexible and innovative. The use of different alkali metal heat pipes and thermoelectric conversion methods has a direct impact on the system power and the quality of the entire system. The combination of heat pipe and various thermoelectric conversion methods can be attempted.

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Intelligent commissioning system based on EPICS and differential evolution algorithm for synchrotron radiation beamline
Yingzhi SHI, Mei GAO, Wenhong JIA, Guangzhi YIN, Xingyu GAO, Yonghua DU, Lifang ZHENG
Nuclear Techniques    2020, 43 (5): 50101-050101.   DOI: 10.11889/j.0253-3219.2020.hjs.43.050101
Abstract119)   HTML9)    PDF(pc) (1311KB)(175)       Save
Background

In synchrotron radiation facilities, it is important to keep beamlines operating in optimal conditions. The debugging process is normally very time consuming due to the irregular light source beam point, and it is not easy to get global optimum.

Purpose

This study aims to develop an intelligent debugging system based on Experimental Physics and Industrial Control System (EPICS) and differential evolution algorithm for synchrotron radiation beamline commissioning.

Methods

First of all, based on the differential evolution algorithm, intelligent optimization model of beamline was established. Then the automatic optimization of beam adjusting process was implemented by using LabVIEW program and communication with the EPICS-based control system was achieved by CaLab interface module. Functions of the user interface, motion control, algorithm implementation and evolution processing were integrated in the LabVIEW program. Finally, this intelligent commissioning system was tested at the X-ray diffractive (XRD) beamline of SSRF (Shanghai Synchrotron Radiation Facility) for optimization of the beam flux at sample position by adjusting the beamline optical components.

Results & Conclusions

Online tests results show that this intelligent commissioning system converges to the optimal solution quickly, and the convergence time is about 30 min, more than one order of magnitude higher than manual optimization efficiency.

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Simulation study on scattering interference in 60Co dual-projection radiation imaging system based on Monte Carlo method
Minzi NI, Zhentao WANG, Peng CONG, Litao LI
Nuclear Techniques    2020, 43 (4): 40202-040202.   DOI: 10.11889/j.0253-3219.2020.hjs.43.040202
Abstract95)   HTML10)    PDF(pc) (1056KB)(53)       Save
Background

In 60Co dual projection radiation imaging system, the radiation sources are arranged at the bottom and side while their corresponding ionization chamber detectors are set respectively in the gantry. With the synchronous movement of the sources and the gantry, the system can obtain both side-view and upward-view images of the objects simultaneously. However, due to the presence of scatter, the imaging of the two projection planes will interfere with each other.

Purpose

This study aims to reduce the effect of scattering between two projection planes and improve the imaging quality of the system by using Monte Carlo method.

Methods

Firstly, a simulation model based on Monte Carlo method was established, and its reliability was verified by comparing the simulation data with the experimental data of the scattering distribution at no-load. Secondly, the scattering effects of different projection plane spacings, different shielding materials (tungsten, lead, steel, and aluminum) around the detector with different installation positions, and thickness of the shielding layer on the scatter were calculated based on the model built. Finally, shielding correction effect of 2.5 cm thick lead layer was evaluated.

Results

Simulation results show that when the projection plane spacing is 40 cm and 80 cm, the scattering can be reduced to less than 55% and 40% of that of the 10 cm plane spacing respectively. When projection plane spacing is 40 cm, a lead shield placed between the gantry support and the side-view ionization chambers can achieve best shielding effect at the same thickness compared with steel and aluminum. When the thickness of the lead is 2.5 cm, scattering will be further reduced by 80%.

Conclusions

This study provides a reference and guidance for the hardware improvement and upgrade of the dual-projection system for scattering correction.

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Conceptual design of Mars molten salt reactor
Shihe YU, Qiang SUN, Heng ZHAO, Rui YAN, Yang ZOU, Bing LAN
Nuclear Techniques    2020, 43 (5): 50603-050603.   DOI: 10.11889/j.0253-3219.2020.hjs.43.050603
Abstract92)   HTML7)    PDF(pc) (689KB)(79)       Save
Background

Mars exploration has recently become a mainstream trend in space research. The establishment of a Mars base is an inevitable choice for human to study and develop Mars. Compared with the solar energy storage system, the nuclear reactor as a Mars base energy system has significant advantages in terms of system mass, operational flexibility, and environmental robustness.

Purpose

This study aims to propose core design scheme of Mars molten salt reactor (M2SR-1) and calculation model in aspects of reactor physics, critical safety and thermal.

Methods

The Monte Carlo N Particle Transport Code (MCNP) and Oak Ridge Isotope Generation and Depletion Code (ORIGEN) were employed to establish core physical calculation model. Calculation and analysis were performed in aspects of physical, safety, thermal and so on.

Results

Computational results reveal that the scheme of M2SR-1 meets the requirement of 8-year-life under full power operation. Under different hypothesis falling environments, the effective multiplication factor of nuclear reactor is less than 0.98, satisfying the criticality safety requirements.

Conclusion

This study provides basic theoretical reference for the design of planet surface molten salt reactor.

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Reconstruction of point spread function of incoherent light by redundant information extraction and its application in synchrotron radiation imaging system
Huijuan XIA, Yanqing WU, Lei ZHANG, Yuanhe SUN, Renzhong TAI
Nuclear Techniques    2020, 43 (1): 10101-010101.   DOI: 10.11889/j.0253-3219.2020.hjs.43.010101
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Background

The point spread function (PSF) of X-ray indirect imaging system is difficult to measure accurately through experiments, and the theoretical construction process is complex, hence it is difficult to meet the actual situation, resulting in poor image quality.

Purpose

This study aims to obtain the PSF of X-ray indirect imaging system by reconstructing PSF with redundant information to obtain a more accurate PSF under incoherent illumination.

Methods

First of all, theoretical analysis was performed for the measuring problem of incoherent optical PSF. Since the optical transfer function (OTF) was the fourier transform of PSF, and coherent transfer function (CTF) was closely related to OTF, nonlocality of incoherent optical information distribution was used to reconstruct the central region of the PSF. Then, the redundent information in a 2D grating scintillation imaging system was extracted to reconstruct the PSF by converting incoherent diffraction field to coherent diffraction field. Finally, experimental data obtained from BL13W beamline station of Shanghai synchrotron radiation facility (SSRF) were employed to evaluate PSF and image restoration results of scintillator imaging system.

Results

Experimental results of synchrotron radiation imaging show that this method can recover the image more accurately than other PSF measurement methods.

Conclusion

The PSF reconstructed by redundant information method can not only restore the image accurately, but also avoid a lot of complex problems.

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Design of novel lead-free flexible composites for radiation protection and simulation of protective effect
Siqi YAN, Peng CHENG, Guangyi YU, Hanzhou LIU, Churan FEI, Xiaoping OUYANG
Nuclear Techniques    2020, 43 (5): 50201-050201.   DOI: 10.11889/j.0253-3219.2020.hjs.43.050201
Abstract85)   HTML3)    PDF(pc) (783KB)(57)       Save
Background

The number of radioactive practitioners has increased rapidly due to the wide application of X-ray, resulting in widespread attention to radiation protection. Lead is commonly used as a shielding material, but is extremely toxic and harmful to human health. The lead-based protective clothing on the market is too heavy and uncomfortable to wear.

Purpose

This study aims to design flexible composites of lead-free for shielding X-ray of different energy ranges and evaluating its shielding effect.

Methods

The X-ray mass attenuation coefficients of high atomic number materials were calculated according to National Institute of Standards and Technology (NIST) method. Hence, the ideal functional fillers were selected as shielding materials instead of lead. The MCNP5 code was employed to evaluate protective performance of lead-free flexible composites consisting of various doped metal elements with high atomic number.

Results

Simulation results show that Bi doping is an ideal substitute for Pb doping, and Bi2O3 can be used as the first-rate functional filler in lead-free flexible composites. Shielding performance of the composite doped with Bi2O3 and Gd2O3 is obviously improved during the energy of 54~66 keV whilst the composites doped with Bi2O3 and W functional fillers achieve the best X-ray attenuation at around 70 keV of X-ray.

Conclusions

A variety of bismuth-based flexible composites have been designed to replace lead-based materials. Bi2O3 is the optimal filling material for X-ray scattering energy less than 54 keV, incorporation of two functional materials, Bi2O3 and Gd2O3, can effectively improve the absorption effect of the composites for X-ray scattering energy in range of 54~66 keV. In the energy range of 66~100 keV, incorporation of two functional materials, Bi2O3 and W, is the optimal filling method whilst it is best to fill Bi2O3 alone to shield X-ray scattering energy greater than 100 keV.

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Evaluation of super homogenization method for pin-by-pin core calculation
Bin ZHANG, Yunzhao LI, Hongchun WU
Nuclear Techniques    2020, 43 (6): 60001-060001.   DOI: 10.11889/j.0253-3219.2020.hjs.43.060001
Abstract81)   HTML7)    PDF(pc) (1169KB)(30)       Save
Background

The new generation of pin-by-pin calculation method has gradually become the state-of-the-art approaches along with the improvement of computer technology and the development of core design.The difference between the pin-by-pin calculation and the traditional two-step scheme leads to the homogenization technique difficult to implement.

Purpose

This study aims to evaluate super homogenization techniques for pin-by-pin core calculationwith emphasis on equivalent homogenization constants.

Methods

Super homogenization method was used as one of the main homogenization techniques of pin-by-pin calculation. For fuel assembly, the traditional super homogenization method was employed to generate the group constants. For reflector assembly with neutron leakage, the super homogenization method related to space leakage was applied to the generation of equivalent homogenization constant including super homogenization factor.

Results

Based on the three-dimensional C5G7 benchmark, the application performance of the super homogenization method in pin-by-pin calculation is evaluated. The eigen-value relative error of pin-by-pin calculation is -0.001 6, assembly-power and pin-power relative errors are less than 5.5%.

Conclusions

Numerical results showed that the pin-by-pin calculations have the higher accuracy than the assembly-homogenized results.

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Preparation of amidoxime-based ultra-high molecular weight polyethylene fiber for removing uranium from fluorine-containing wastewater
Xinxin FENG, Long QIU, Mingxing ZHANG, Maojiang ZHANG, Yulong HE, Rong LI, Guozhong WU
Nuclear Techniques    2020, 43 (2): 20301-020301.   DOI: 10.11889/j.0253-3219.2020.hjs.43.020301
Abstract78)   HTML10)    PDF(pc) (2475KB)(42)       Save
Background

During the uranium enrichment process, the generated wastewater containing fluoride and uranyl ions, has potential threat to aquatic ecosystem and human health. Thus, the uranium concentration in the wastewater and its secondary sources must be reduced to an acceptable value before being discharged into the environment.

Purpose

This study aims to graft acrylonitrile (AN) and methacrylic acid (MAA) onto ultra-high molecular weight polyethylene (UHMWPE) fiber to synthesize amidoxime (AO)-based sorbent for removing uranium (U(VI)) from simulated wastewater containing fluoride ions.

Methods

The AO-based sorbent was prepared by radiation grafting of AN and MAA onto UHMWPE fiber, followed by amidoximation. The chemical structures and surface morphologies of the pristine and modified UHMWPE fiber were characterized by Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The uranium adsorption performance of the sorbent was investigated by batch adsorption in simulated wastewater.

Results and Conclusions

1) The uranium sorption kinetics and isotherm of AO-based UHMWPE fiber were in congruence with the pseudo-second-order model and the Langmuir model, respectively. 2) The maximum U(VI) adsorption capacity in simulated wastewater (U(VI): 40 mg?L-1; sodium fluoride (NaF): 10 g?L-1; sorbent dosage: 0.2 g?L-1; time: 21 d) was 151.98 mg?g-1, which is basically consistent with the theoretical saturated adsorption capacity (153.85 mg?g-1). 3) The removal ratio of U(VI) in simulated wastewater reached 99.93% by increasing sorbent dosage (1.5 g?L-1), and the residual uranium (28 μg?L-1) can meet the national discharge standard (< 50 μg?L-1).

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Detector design and performance test for coded camera of large area and high sensitivity
Yan LI, Qiang WANG, Xianchao HUANG, Lei SHUAI, Daquan CAO, Yiwen ZHANG, Yao YANG, Xuanhou HU, Xiuzuo LIANG, Jun WU, Guoqiang ZENG, Zhiming ZHANG
Nuclear Techniques    2020, 43 (5): 50402-050402.   DOI: 10.11889/j.0253-3219.2020.hjs.43.050402
Abstract73)   HTML10)    PDF(pc) (1410KB)(46)       Save
Background

The traditional gamma camera cannot locate the contaminated area of nuclear accident, and cannot obtain the information of the contaminated area and degree in real time.

Purpose

This study aims to develop a coded aperture gamma camera detector system with large area and high sensitivity.

Methods

A detector module of large area CsI (Tl) crystal array coupled with photomultiplier tube array was proposed. It consisted of 121 CsI (Tl) crystals at the size of 15 mm×15 mm×15 mm, and 2×2 array composed of 4 detector modules was taken as γ camera detector. Multi-channel readout electronics composed of amplification, filter shaping and single-to-differential conversion circuit was independently designed for readout processing of detector signals. Finally, the performance of this detector system was evaluated by experimental tests.

Results

The results indicate that the detector module can achieve the position resolution, and its average energy resolution is 9.4% under the excitation of 662 keV γ-ray.

Conclusions

The detector system can satisfied the design requirements of coded aperture γ camera of high sensitivity in terms of position resolution, energy resolution, uniformity of peak position and detection efficiency.

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Study of the measurement of the thickness of diffusion aluminizing layer based on X-ray fluorescence
Jichao LIU, Cheng WANG, Pengli DAI
Nuclear Techniques    2020, 43 (2): 20201-020201.   DOI: 10.11889/j.0253-3219.2020.hjs.43.020201
Abstract71)   HTML7)    PDF(pc) (1028KB)(42)       Save
Background

Aluminizing is often used as a protective coating for aero-engine turbine blades, but the current nondestructive testing equipment can not achieve accurate measurement of the coating thickness. The uniformity of aluminizing thickness has a great impact on the performance of turbine blades and the safety and stability of engine.

Purpose

This study aims to develope a nondestructive measurement method for the thickness of diffusion aluminized layer based on X-ray fluorescence absorption.

Methods

First of all, according to the theoretical calculation formula of X-ray fluorescence absorption, the linear relationship between the logarithm of the fluorescence intensity ratio (lnR) and the thickness of the fluorescence penetrating material (x) was obtained. Then a unitary linear regression model related to the main elements of K403 alloy and a multiple regression model based on the forward selection variable method were established. Finally, the comparative study of the prediction results of the two models was carried out.

Results

The experimental results show that the multi regression calculation model is relatively stable in comparison with the unitary regression calculation model, and the average relative error of measurement results under different thicknesses is only 3.2%.

Conclusions

The proposed method provides a convenient and feasible guiding idea for solving the problem of measuring the thickness of diffusion permeable layer.

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VaspCZ: an efficient VASP computation assistant program
Zhengde ZHANG, Menglu TAN, Cuilan REN, Ping HUAI
Nuclear Techniques    2020, 43 (3): 30501-030501.   DOI: 10.11889/j.0253-3219.2020.hjs.43.030501
Abstract71)   HTML5)    PDF(pc) (1377KB)(48)       Save
Background

With the improvement of computing power and the rise of high-throughput computing, researchers usually need to perform a large number of repeated instructions to submit scientific tasks and further check their computational results during material theoretical calculations. Generally, these instructions are simple, cumbersome and time consuming.

Purpose

This study aims to improve the efficiency of scientific calculations by using VASP code.

Methods

The material theory calculation assistant program, VaspCZ, developed by using Python languages, is summarized to form a general github open source project, which provides detailed user documents, examples and application programming interfaces (API).

Results

VaspCZ, an efficient VASP computation assistant program includes two parts: the software part and API part. The software part provides the command line user interface, which enabled the researchers to complete the VASP calculations with the basic Linux command. The API part provides the bottom layer library to realize the custom calculation (such as high-throughput calculation, writing advanced application, etc.) for the researchers with python experiences.

Conclusions

It is proved by practice that the efficiency of theoretical calculation of materials using VASP can be significantly improved by aid of this assistant program.

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Study on the breeding characteristics study of chlorine and fluorine salt fast reactor
Xuemei ZHOU, Dongguo LI, Liaoyuan HE, Guimin LIU
Nuclear Techniques    2020, 43 (4): 40001-040001.   DOI: 10.11889/j.0253-3219.2020.hjs.43.040001
Abstract68)   HTML9)    PDF(pc) (2087KB)(36)       Save

[Background and

Purpose

The molten salt fast reactor is one of the advanced nuclear energy systems which has attracted much attention because of its outstanding advantages in fuel proliferation, nuclear waste transmutation and inherent safety. Liquid fluorine salt or chlorine salt is usually used as fuel carrier salt and coolant in molten salt fast reactor, which has high breeding properties.

Methods

Based on the dual-fluid molten salt reactor core structure, a comprehensive simulation program SCALE (Standardized Computer Analyses for Licensing Evaluation) were adopted to simulate and calculate the U-Pu fuel breeding ratio of two kinds of fluorine-salt fast reactors and one chlorine-salt fast reactor under the same metal solubility.

Results

The breeding ratios of different breeding and reflecting layers were simulated, and the changes of neutron energy spectra in fission and breeding zones were analyzed. The breeding ratio of chlorine salt fast reactor increases with the increase of the thickness of the breeding layer and the reflector layer, but the growth rate decreases. When the thickness of the breeding layer of the fast reactor is small, the variation of the breeding layer has little effect on the breeding ratio. When the thickness increases to 60 cm, the variation of the breeding layer thickness has almost no effect on the breeding ratio. The variation of reflector size has no effect on the breeding ratio. The critical state of the reactor core and the neutron energy spectrum in the fission region are not affected by the thickness of the breeder layer and the reflector layer.

Conclusions

At the same temperature and molar ratio, chlorine fast reactor has higher U-Pu fuel breeding ratio than fluorine fast reactor. This provides a theoretical basis for basic salt selection and size design for molten salt fast reactor diffusion.

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Design and verification of small intelligent programmable SiPM power supply
Huiliang HOU, Yuefeng HUANG, Maosong CHENG, Zhimin DAI
Nuclear Techniques    2020, 43 (6): 60402-060402.   DOI: 10.11889/j.0253-3219.2020.hjs.43.060402
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Background

As a new solid-state photosensor, silicon photomultiplier (SiPM) has high gain (106), low power consumption (supply current is several μA), small size (several square milimeters), low operating voltage (less than 100 V) and other advantages. Compared with traditional photomultiplier tube, SiPM does not affected by magnetic fields. However, there is a disadvantage that the gain of SiPM is greatly affected by temperature, the gain will decrease by about 5×105 for every 10 °C rise in temperature, which will have a greater impact on energy spectrum measurement and radiation imaging applications.

Purpose

This study aims to design and develop a small programmable SiPM power supply for temperature independent gain.

Methods

First of all, a high-voltage power supply module was designed for SiPM, making use of the gain regulation by voltage. Temperature sensor, DC-DC power chip, etc., were integrated into an ARM-based micro control unit (MCU) module for automatic SiPM power supply. Then the effect of voltage compensation to gain in the temperature range of 5 ℃ to 40 ℃ was verified by using digital multi-channel analyzer with comparison of the channels of full energy peak on the energy spectrum of 241Am source.

Results

The channel of full energy peak which indicates the gain of the SiPM is stable by using the voltage compensation (gain drift correction), and the maximum drift of the SiPM gain from 5 ℃ to 40 ℃ decreases from 87.3% before compensation to 2.76%.

Conclusions

Gain drift correction achieved by a small intelligent programmable SiPM power supply broadens the scope of SiPM application.

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Development of a 4π phoswich detector for measuring radioactive inert gases
Dongdong ZHOU, Simei YOU, Jie XIN, Cuiping YANG, Wanxin WEN, Yue YANG, Baoguo ZHANG, Rensheng WANG, Ming ZHANG
Nuclear Techniques    2020, 43 (5): 50401-050401.   DOI: 10.11889/j.0253-3219.2020.hjs.43.050401
Abstract67)   HTML11)    PDF(pc) (989KB)(56)       Save
Background

The radiation field of the radioactive inert gas generated in a nuclear power station is mainly β-γ mixed field. The phoswich detector has good ability to discriminate β and γ rays.

Purpose

This study aims to develop a set of 4π phoswich detector to accurately measure the energy spectrum of the mixed field and distinguish β-γ rays.

Methods

The phoswich detector mainly consisted of a hollow cylindrical plastic scintillator EJ-200 with layer thickness of 1 mm and a cesium iodide scintillator CsI (Tl) with side wall thickness of 20 mm overlay on the outer layer of EJ200. The two photomultiplier tubes (PMT) were placed at both end surfaces of the cylinder respectively, and coupled by using silicone oil. The DT5790 dual digital pulse shape analyzer of CAEN company and the digital pulse processing-pulse shape discrimination (DPP-PSD) were used to obtain the detector output signals, and results were processed by ROOT and MATLAB software. Finally the detector was calibrated by use 133Ba and 137Cs radiation sources.

Results & Conclusions

The β-γ signal discrimination is realized by mathematical methods in back end computer software, indicating that the detector is capable of measuring radioactive inert gas.

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Study of the detection unit of the calorimeter for the next generation Compton telescope
Wufeng LIU, Xiangman LIU, Shuwen TANG, Zhiyu SUN, Yuhong YU, Wei WANG, Ruofu CHEN, Fang FANG, Junling CHEN, Duo YAN, Yongjie ZHANG, Shitao WANG, Xueheng ZHANG, Ke YUE, Jianwei LU, Bingqian ZHOU, Yixuan ZHAO
Nuclear Techniques    2020, 43 (1): 10203-010203.   DOI: 10.11889/j.0253-3219.2020.hjs.43.010203
Abstract64)   HTML8)    PDF(pc) (1561KB)(59)       Save
Background

Compared with other energy regions, little research of gamma-ray astronomy in the MeV energy region has been carried out, hence insufficient exploration of astrophysical information is available in the MeV energy region.

Purpose

This study aims to investigate the gamma-ray astronomy of MeV energy region so as to provide reference for the design of the next generation Compton telescope calorimeter.

Methods

A dual-ended readout gamma-ray detector was designed as the elementary detection unit of a calorimeter. The detector was made of a long CsI(Tl) bar with the size of 10 mm×10 mm×80 mm and wrapped by the ESR film. The photodiode (PD), the avalanche photodiode (APD) and the silicon photomultiplier tube (SiPM) were used respectively as photoelectric converters for the detector, and they were tested by using 137Cs source at different positions on the detector.

Results

The results show that the total energy and interaction position of the incident gamma-ray can be determined by reading the signal amplitudes at two ends of the three photoelectric converters. The energy resolution for 662 keV gamma-ray is 5.9% (full width at half maxima, FWHM) and the position resolution is about 5.7 mm (FWHM), which is the best performance obtained in the case of SiPM readout.

Conclusions

The detection unit designed in this paper can meet the performance requirements of the calorimeter of the next generation Compton telescope.

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3D imaging of rat brain neural network using synchrotron radiation
Shuntong KANG, Tong WU, Zhuohui CHEN, Mengqi ZHANG
Nuclear Techniques    2020, 43 (7): 70101-070101.   DOI: 10.11889/j.0253-3219.2020.hjs.43.070101
Abstract63)   HTML10)    PDF(pc) (1359KB)(25)       Save
Background

Synchrotron radiation technology has a wide application prospect. X-ray absorption contrast imaging can not only obtain the three-dimensional (3D) morphological structure of neurons, but also improve the effective spatial resolution of detection, which meets the requirements of micro-neural network imaging research. It is feasible and effective to construct high-resolution 3D visualization network of brain neural network when combined with Golgi-Cox staining.

Purpose

This study aims to explore the application of synchrotron radiation absorption contrast imaging technology in the observation of 3D imaging of Golgi-Cox-stained mouse brain micro-neural network.

Methods

Twelve normal C57 mice were randomly divided into two groups, A and B, and perfused with brain tissue. Group A was treated without staining. The brains of group B were stained with Golgi-Cox and dehydrated in gradient ethanol. Specimens were scanned for absorption contrast imaging at X-ray imaging and biomedical application beam line station (BL13W1) in Shanghai Synchrotron Radiation Facility (SSRF), and data processing was performed by using software such as Amira.

Results

The imaging results show that both the cerebellar neural network structure and single neuron morphology in mouse are accurately presented. X-ray absorption contrast imaging technology, as an advanced three-dimensional rendering method of microscopic neural network, provides a new three-dimensional visualization method for morphological research of mouse brain neurons.

Conclusions

Synchrotron radiation can achieve high-precision 3D neuroimaging, which overcomes the disadvantages of traditional staining 2D histology, such as the damage of sections to specimens. This method combined with Golgi-Cox staining, can be used for the construction of regional neural networks and non-destructive research on the integrity of the brain.

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Evaluation study on comprehensive efficiency of physical protection system based on neural network
Gou ZHAO, Hanlin XIONG, Guodong WU, Yukun MA, Fanfu KONG
Nuclear Techniques    2020, 43 (2): 20602-020602.   DOI: 10.11889/j.0253-3219.2020.hjs.43.020602
Abstract62)   HTML5)    PDF(pc) (957KB)(32)       Save
Background

At present, most of the physical protection systems of nuclear facilities at home and abroad use the path analysis method to evaluate the effectiveness. The performance of the system is evaluated by calculating the cut off probability, hence the evaluation index is single and cannot reflect factors such as the system reliability, the command strategy, the information security design and other factors.

Purpose

This study aims to analyze the comprehensive effectiveness of the physical protection system by using neural network method.

Methods

The comprehensive effectiveness evaluation index system of the physical protection system was established by using the analytic hierarchy process (AHP), and the comprehensive effectiveness evaluation model of the physical protection system for nuclear facilities was established by using the composite ability of the nonlinearity of the BP (back propagation) neural network. The comprehensive effectiveness of the physical protection system for the marine nuclear power platform was evaluated.

Results & Conclusions

The evaluation results show that the BP neural network evaluation model converges fast, avoids the shortcomings of the majority of sample concentration effects in the AHP evaluation process, and has better adaptability and stability. It provides a kind of field for physical protection effectiveness evaluation.

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Progress of single event effects and hardening technology of CMOS image sensors
Yulong CAI, Yudong LI, Lin WEN, Qi GUO
Nuclear Techniques    2020, 43 (1): 10502-010502.   DOI: 10.11889/j.0253-3219.2020.hjs.43.010502
Abstract60)   HTML3)    PDF(pc) (1051KB)(53)       Save
Background

CMOS imager sensors (CISs) used in the space radiation environments are susceptible to single event effects (SEEs), which can cause images corruption and even CIS function failure.

Purpose

This study aims to evaluate the progress of SEEs and hardening technology of CIS.

Methods

In this paper, the SEEs on the CIS are reviewed by summarizing the investigation from different particles such as heavy ions, protons, electrons and neutrons, and from different types of SEEs: including single event transient (SET), single event upset (SEU), single event functional interrupt (SEFI) and single event latch-up (SEL). Progresses of SEEs hardening technology on CIS are briefly investigated.

Results & Conclusions

This paper analyzes the SEEs and problems to be solved urgently on hardening technology on the CIS technology, which provides theoretical reference for further researches in the future.

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Th-U and U-Pu cycling performances of molten chloride salt fast reactor under LEU start-up mode
Liaoyuan HE, Shaopeng XIA, Rui YAN, Yang ZOU, Guimin LIU
Nuclear Techniques    2020, 43 (1): 10604-010604.   DOI: 10.11889/j.0253-3219.2020.hjs.43.010604
Abstract59)   HTML5)    PDF(pc) (1945KB)(34)       Save
Background

Compared with molten fluoride salt fast reactor, molten chloride fast reactor (MCFR) has higher solubility of heavy metals, harder neutron energy spectrum, and better breeding performance, hence an ideal type of reactor for realizing closed fuel cycle.

Purpose

This study aims to analyze and compare Th-U and U-Pu cycle performances of MCFR.

Methods

Based on the 2 500 MW molten chloride salt fast reactor, the TMCBurnup and MESA codes were used to analyze the transition and equilibrium states of Th-U and U-Pu cycles with Low Enriched Uranium (LEU) as the starting fuel. Two different transition modes were analyzed from the perspectives of nuclide evolution, proliferation, safety and radioactivity.

Results

The results show that U-Pu cycle has better breeding performance than Th-U cycle. In breeding and burning (B&B) mode, the breeding ratios of the U-Pu and Th-U cycle are 1.56 and 1.24, respectively. The corresponding doubling time (DT) of the U-Pu and Th-U cycle is 13.5 years and 16.5 years, while in pre-breeding and burning (PB&B) mode, the replacement ratios are 1.58 and 1.08, and the doubling time is 12.8 years and 13 years, respectively. However, Th-U cycle has better safety performance, lower transuranic nuclides (TRU) accumulation and lower radiotoxicity.

Conclusions

Both Th-U and U-Pu cycle have good breeding performance in MCFR, and they can keep safety under all cycle modes. However, the U-Pu cycle has better breeding performance and the Th-U cycle has lower radiotoxicity and TRU accumulation, which reduces the difficulty of post-processing.

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Simultaneous quick measurements of combined synchrotron EDXAFS and EDXRD
LIU Zhijie,LUO Zhenlin
Nuclear Techniques    2019, 42 (12): 8-12.   DOI: 10.11889/j.0253-3219.2019.hjs.42.120102
Abstract58)   HTML6)    PDF(pc) (701KB)(57)       Save
Background

X-ray absorption fine structure (XAFS) and X-ray diffraction (XRD) are the commonly used techniques to determine the short-range and long-range order of atomic arrangement in materials.

Purpose

This study aims to perform XAFS and XRD measurements quickly and simultaneously for in situ kinetic structural investigation.

Methods

A method of combining synchrotron energy-dispersive X-ray absorption fine structure (EDXAFS) and energy-dispersive X-ray diffraction (EDXRD) was proposed. The white light of synchrotron radiation was used that could theoretically provide microsecond scale representation speed and time resolution.

Results & Conclusions

With a potential temporal resolution of micron seconds, this strategy provides a possibility for quick and simultaneous characterization of short- and long-range structural information of materials that sheds light on in-situ real-time investigation of structural evolution in materials in real conditions.

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Research on beam-base alignment for 120 MeV electron linear accelerator
Bin SUN, Yu WANG, Dongwei HEI, Binkang LI, Xinjian TAN, Xiufeng WENG, Jun LIU, Xiaodong ZHANG, Zhuming FU
Nuclear Techniques    2020, 43 (6): 60202-060202.   DOI: 10.11889/j.0253-3219.2020.hjs.43.060202
Abstract55)   HTML1)    PDF(pc) (1273KB)(31)       Save
Background

120 MeV electron linear accelerator has high requirement for beam emittance, and the traditional optical collimation cannot meet the requirement.

Purpose

This study aims to use beam-based alignment (BBA) method to achieve higher precision collimation and obtain better beam quality.

Methods

According to the configuration of 120 MeV electron linear accelerator, all of beam position monitor (BPM) measurement data of the corresponding position under different energy were collected, then, the dispersion-free steering (DFS) algorithm was used to simulate the correction of accelerator matching transmission section in different beam jitter conditions.

Results

The simulation results indicate that the algorithm can minimize the transverse offset of quadrupole to 50 μm.

Conclusions

The DFS algorithm can reduce the trajectory distortion in the low beam jitter accelerator.

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Development of a successive yield measurement system for airborne radioiodine generation using NaI(Tl) spectrometer
Jiayu XIN Zhiwei LI Xiaoshuang HE Linfeng TANG Fangdong ZHAO Chao LIU
Nuclear Techniques    2019, 42 (12): 120401-120500.   DOI: 10.11889/j.0253-3219.2019.hjs.42.120401
Abstract54)   HTML9)    PDF(pc) (648KB)(33)       Save
Background

Environment airborne radioiodine monitoring is important for the operation of nuclear power plants and public nuclear safety. The airborne radioiodine generation technique is essential for airborne radioiodine research, including its measurement technology and behavior characteristics. Although many airborne radioiodine generation techniques have been developed, little attention has been paid to higher performance generation techniques and detailed understanding of the generation process.

Purpose

This study aims to develop a successive airborne radioiodine generation measurement system.

Methods

Two series-connected collection containers, two NaI(Tl) spectrometers, and one computer with self-developed software, were employed for the composition of this successive yield measurement system. In the process of airborne radioiodine generation, the series-connected collection containers were connected with the generation container for continuous airborne radioiodine collection whilst the NaI(Tl) spectrometers monitored radioiodine in the collection containers and generation container in real time. Meanwhile, the measured spectrum was sent to the computer and analyzed by self-developed software. Hence the change of yield with time during the generation of the airborne radioiodine could be reflected by the software. The major influences in the measurement were also discussed theoretically and experimentally, including interference of measurements between radioiodine in different containers and inconsistencies between radioiodine collection containers. Finally, the uncertainty analysis of this measurement result under typical working conditions was performed.

Results

This measurement system was applicable to various airborne radioiodine generation techniques including inorganic iodine, organic iodine and aerosol iodine. The measurement period was adjustable. Considering the measurement frequency and uncertainty, the recommended measurement period was 20 s. Under typical working conditions, the expanded uncertainty of the measured yield was 2.5% (k=2) while yield was 90%.

Conclusions

This successive yield measurement system could be used to observe the detailed process of airborne radioiodine generation, and provide a powerful tool for the optimization of airborne radioiodine generation techniques.

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Dynamic magnetic measurements of a Kicker magnet for a proton therapy facility
Guanqun HAN Wenjie QIN Bin LIU Xu CHEN Qushan LI
Nuclear Techniques    2020, 43 (1): 10201-010201.   DOI: 10.11889/j.0253-3219.2020.hjs.43.010201
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Background

A proton therapy facility based on superconducting cyclotron is under development in Huazhong University of Science and Technology Proton Therapy Facility (HUST-PTF). In HUST-PTF system, a kicker magnet upstream of the degrader is used to realize the fast switch on/off for the spot scanning process and the treatment safety.

Purpose

This study aims to measure the integral field and the dynamic performance of the kicker magnet and implement a magnetic measurement system based on induction method.

Methods

First of all, two different schemes (long coil and PCB coil) were adopted in the magnetic measurement system to obtain the induced voltage. Then, the induction voltage signals acquired by induction coils were integrated by analog or digital integrators. Experimental data analysis was performed to evaluate these two schemes, and final solution for magnetic measurement system was determined.

Results

Experimental results show that PCB coils with high geometric accuracy and RC integrators, less sensitive to zero drift, hence are adopted as the final solution of the measurement system. The overall error of the magnetic measurement system is less than 0.1%. The experimental results show that response time is less than 100 μs, the integral field greater than 0.025 2 T·m, integral field uniformity is better than 1%, and maximum standard deviation of uniformity is 0.006%.

Conclusions

The kicker magnet and its measurement system meet the design specifications.

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Analysis of Th-U breeding in molten salt fast reactor
Dongguo LI, Guimin LIU
Nuclear Techniques    2020, 43 (5): 50604-050604.   DOI: 10.11889/j.0253-3219.2020.hjs.43.050604
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Background

Because of its superior performance, molten salt reactor has been selected as one of the candidates for the fourth-generation reactors, and has become the focus of international attention.

Purpose

In the molten salt fast neutron reactor, we try to find the most suitable molten salt fuel scheme to achieve the purpose of high proliferation of fissile nuclides.

Methods

Based on the two-fluid cooling cycle scheme, independent cooling cycles of fission molten salt fuel and breeding molten salt, a comprehensive simulation program SCALE (Standardized Computer Analyses for Licensing Evaluation) was employed to achieve high breeding ratio (BR) in the molten salt fast reactor by utilizing the high solubility characteristics of thorium and uranium heavy metal salts in fluorinated or chlorinated molten salts at high temperatures. Three feasible molten salt fuel schemes (LiF+ThF4+UF4, NaF+ThF4+UF4, and NaCl+ThCl3+UCl3) were compared by calculating the neutron energy spectrum and the reactivity temperature coefficient. Influence factors of BR, such as the sizes of fission zone, breeding zone and ZrC reflective layer, the isotopic abundance of 6Li and 35Cl in the molten salt, molten salt density error on the calculation accuracy, and the evolution of fissile nuclides with reactor operating time, were computationally analyzed.

Results

The breeding ratio (BR) of reactor reaches about 1.2 in all three molten salt fuel schemes when the diameter and height of the fission zone are both 260 cm.

Conclusions

With optimization of the reactor geometry, and the composition and isotopic abundance of the molten salt fuel, a high breeding ratio of the reactor is achievable for the thorium-uranium fuel cycle of molten salt fast reactor.

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Synchrotron radiation photoemission spectroscopy study on the phenomenon of alloying during stanene growth
Lei ZHAO, Chen LIU, Xiaoning WANG, Gholam Turghunjan, Jinmei LI, Jiali ZHAO, Yuxuan GUO, Haijie QIAN, Ibrahim Kurash, Jiaou WANG
Nuclear Techniques    2020, 43 (7): 70102-070102.   DOI: 10.11889/j.0253-3219.2020.hjs.43.070102
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Study on performance of Yttrium doped BaF2 scintillation detector
Hongfeng WANG, Fuyan LIU, Yingjie WANG, Junfeng CHEN, Peng KUANG, Peng ZHANG, Runsheng YU, Xingzhong CAO, Yuxiao LI, Baoyi WANG
Nuclear Techniques    2020, 43 (3): 30401-030401.   DOI: 10.11889/j.0253-3219.2020.hjs.43.030401
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Background

BaF2 scintillation detector is commonly used in low intensity γ-ray detection experiments, and it is easy to pileup during high intensity γ-ray detection.

Purpose

This study aims to investigate the performance of Yttrium doped BaF2 (Yttrium doped with 1 at%, atomic percentage) scintillation detector with main concern of pileup and time resolution for high intensity γ-ray detection.

Methods

The energy resolution and time properties of Yttrium doped BaF2 (Yttrium doped with 1 at%) scintillation detector were experimentally tested by using 0.511 MeV γ-ray generated after positron annihilation from 22Na source. As a comparison, the normal BaF2 detector was also tested.

Results

The experimental results show that the ratio of fast and slow components of Yttrium doped BaF2 crystal (1:1.1) is much higher than that of BaF2 crystal (1:5), but the energy resolution of Yttrium doped BaF2 detector (38%) is worse than that of BaF2 detector (19%). For high intensity γ-ray detection, the Yttrium doped BaF2 detector have better time resolution than the BaF2 detector.

Conclusions

The decrease of the slow component in Yttrium doped BaF2 crystal can shorten the time width of the detector output signal, hence reduce the signals' pileup and improve the time resolution of the detector in high count rate environment.

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Fast confirmation of the incident electron energy by simulation for medical linac
Junjie HAN, Yongdong ZHUANG, Xiaowei LIU
Nuclear Techniques    2020, 43 (1): 10202-010202.   DOI: 10.11889/j.0253-3219.2020.hjs.43.010202
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Background

Monte Carlo method provides a powerful tool for the simulation of particle transport in radiotherapy, hence can be used for determination of the target energy of the incident electron in medical linac simulation.

Purpose

This study aims to find a way that can confirm the incident electron energy accurately and quickly, and save time for Monte Carlo linac simulation.

Methods

First of all, Monte Carlo program package EGSnrc/BEAMnrc was employed to build up the beam models of Varian 600C, Trilogy and Edge FFF (Flattening Filter Free) model with the same nominal energy of simulation of 6 MV. Then, the dose distributions in different fields (3 cm×3 cm, 10 cm×10 cm, 40 cm×40 cm) using different incident electron energies in water phantom were calculated. Finally simulation results were compared and analyzed to find out a way to ensure the incident electron energy accurately and quickly.

Results

When the incident electron energy varies from 5.5 MeV to 6.5 MeV, percentage depth dose (PDD) is insensitive to the incident electron energy; the off axis ratio (OAR) profiles of 3 cm×3 cm and 10 cm×10 cm are insensitive to the incident electron energies, the OAR profiles of different incident electron energies are almost the same. The OAR profile of 40 cm×40 cm is very sensitive to the incident electron energy. Detailed results at 5 cm underwater show that when the incident electron energy increases by every 0.1 MeV, the average of OAR between the off axis distance from 14.5 cm to 19 cm decreases: 0.82% for Varian 600C 6 MV, 0.98% for Trilogy 6 MV, 0.47% for Edge 6 MV FFF, respectively. Combining the measured OAR profiles of large field (40 cm×40 cm) with the linear relationship between average OAR and the incident electron energy, the incident electron energy can be determined quickly. Compared with the measured values, the PDD and OAR using the fitting energy as input in water phantom, profiles differences are both within 1%.

Conclusions

This proposed method provides a way to ensure the incident electron energy accurately and quickly for medical linac.

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Design of moderator for boron neutron capture therapy based on D-D neutron source
Yi GONG, Xingcai GUAN, Qiang WANG Tieshan WANG
Nuclear Techniques    2020, 43 (9): 90303-090303.   DOI: 10.11889/j.0253-3219.2020.hjs.43.090303
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Background

Boron neutron capture therapy (BNCT) is a promising targeted cancer radiotherapy. The neutron source is pivotal to BNCT. The epithermal neutron flux is one of crucial characteristics for the BNCT neutron source. Therefore, in order to evaluate the quality of the BNCT neutron source, neutron flux detectors have been developed to measure the epithermal neutron flux accurately in our previous work.

Purpose

This study aims to design a moderator for the D-D neutron source for evaluating the performances of the developed BNCT neutron flux detectors.

Methods

The MCNP5 (Monte Carlo N Particle Transport Code, version 5) was employed for the BNCT moderator design based on the D-D neutron source. First of all, the neutron spectrum of a D-D neutron source passing through a single-layer moderating material with different thickness was simulated. Then combined calculation was carried out for three moderator layers configured by different materials with various thickness.

Results

A suitable configuration of the BNCT moderator based on the D-D neutron source is obtained, that is, the combination of 5 cm thick polyethylene (PE) layer + 24 cm thick titanium trifluoride (TiF3) layer + 22 cm thick magnesium fluoride (MgF2) layer is adapted as the moderator material, 20 cm thick nickel (Ni) layer is employed as the reflector and 0.03 cm thick cadmium (Cd) sheet is used as the thermal neutron filter.

Conclusions

The moderated neutron beam can be used to evaluate the performances of the developed BNCT neutron flux detectors.

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Preliminary study on the fast solution strategy of hexagonal nodal neutron transport calculation program
Wenyong XIA, Tengfei ZHANG, Xiaojing LIU, Jinbiao XIONG, Xiang CHAI
Nuclear Techniques    2020, 43 (2): 20603-020603.   DOI: 10.11889/j.0253-3219.2020.hjs.43.020603
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Background

Computational time and calculation accuracy are key features of the application of neutron transfer method.

Purpose

This paper aims to reduce the computational time on the premise of ensuring the accuracy of calculation.

Methods

Based on a neutron transport calculation program for hexagonal nodal, a fast solution method was proposed to solve the 1/6 core is solved with 60° periodic symmetric boundary conditions, and calculated in parallel. The natural decoupling between the response matrices corresponding to different energy groups and nodes, and the parallelism between non-overlapping spatial regions was taken into account to solve the response matrix equation. Based on message passing interface (MPI), parallel program of the response matrix construction was developed to solve the matrix equation. Calibration calculation for the TAKEDA4 benchmark was carried out by parallel computing.

Results

The computational results show that the 60° periodic symmetric boundary condition and the parallel computing function can greatly improve the computational efficiency while ensuring the same calculation accuracy, and verify the correctness of the fast solution strategy. Compared with the full core serial calculation, the total calculation time overhead of the 1/6 core under 9 processors can be reduced by 26, 25, and 22 times under P1, P3, and P5, respectively.

Conclusions

A quick solution for hexagonal nodes is initially achieved.

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Multi-physics field coupling analysis of radio frequency quadrupole cavity
Bo ZHAO, Bin ZHANG, Shuping CHEN, Fengfeng WANG, Tieming ZHU, Xiaofeng JIN
Nuclear Techniques    2020, 43 (3): 30202-030202.   DOI: 10.11889/j.0253-3219.2020.hjs.43.030202
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Background

Radio frequency quadrupole (RFQ) field accelerator causes temperature rise and thermal deformation during high power operation. Among many multi-physical analysis methods for RFQ cavity, these models are limited to 2D RFQ section or 3D RFQ local structures whilst the fluid flow motion was ignored.

Purpose

This study aims to propose a noval three-dimensional multi physical field numerical method for coupling analysis of RFQ cavity.

Methods

Combined with computational fluid dynamics (CFD) and heat flow coupling, electromagnetic, fluid, thermal, structure were integrated into electromagnetic multi physical field coupling analysis. A 81.25 MHz RFQ cavity was taken as sample for verification and the heat transfer effects of three (Standard, RNG, Realizable)k-ε turbulence models under the same experimental conditions were analyzed.

Results & Conclusions

The results show that the CFD numerical simulation method can better simulate the steady-state heat transfer of RFQ accelerator. The feasibility and reliability of the method were verified by comparison with the experimental results. The variation of cavity temperature, structure and frequency under different parameters were analyzed using a suitable turbulence model. Hence this study provides an effective numerical simulation platform for the structural optimization and performance improvement of the accelerators in future.

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A random signal emulator for silicon drift detector based FPGA
Nian YU, Yupeng XU, Jia HUO, Yong CHEN, Weiwei CUI, Wei LI, Ziliang ZHANG, Dawei HAN, Yusa WANG, Can CHEN, Yuxuan ZHU, Xiaofan ZHAO
Nuclear Techniques    2020, 43 (8): 80402-080402.   DOI: 10.11889/j.0253-3219.2020.hjs.43.080402
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Background

The enhanced X-ray Timing and Polarimetry mission (eXTP) is a space science mission designed to study fundamental physics under extreme conditions of density, gravity and magnetism. The spectroscopic focusing array (SFA) is one of eXTP's four payloads, and its main function is to achieve spectrum and timing measurements with high dynamic range and high signal-to-noise ratio (SNR). The SFA uses multi-pixel silicon drift detector (SDD) as the focal plane detector.

Purpose

This study aims to design an SDD signal emulator for the performance test of SFA readout electronics.

Methods

The field programmable gate array (FPGA) was used as the core device of this emulator, making use of its abundant programmable logic resources to generate multiple groups of oscillatory loops. First of all, the configurable logic blocks inside the FPGA were designed as multiple oscillating rings, and its outputs were XOR-ed as true random numbers generator (TRNG). By Bernoulli trials, the uniform random numbers were converted into exponential pulse sequence. Then, the NIST (National Institute of Standards and Technology) suite was employed to test the quality of the TRNG output. Finally, the time interval distribution and counting rate characteristic of output pulses for the emulator were tested.

Results

The sequence of true random numbers of 1 000 Mbits have passed the NIST randomness test. The time interval of the output pulses for the emulator follows the exponential distribution. The dynamic range of counting rate is 1.6 ks-1 to 813.8 ks-1. The voltage range of the output pulse is 2.5 mV to 50 mV, and the minimum time interval is 9.6 ns. The signal emulator can work steadily for a long time.

Conclusions

The SDD signal emulator proposed in this paper can meet the requirements of performance tests for the SFA readout electronics.

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A comparative study of PET-MRI brain quantitative accuracy: the effect of MRI based segmentation and PET based segmentation on SUVR calculation
Zaisheng LI, Shuangshuang SONG, Tianyi ZENG, Jie LU, Lingzhi HU, Qun CHEN
Nuclear Techniques    2020, 43 (5): 50301-050301.   DOI: 10.11889/j.0253-3219.2020.hjs.43.050301
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Background

In clinical application and scientific research of positron emission tomography (PET), the standard uptake value (SUV) is commonly used for disease assessment. In order to reduce the deviations of SUV among clinical PET images, standard uptake value ratio (SUVR) based on a specific reference region is substituted for SUV. Accurate SUVR is hardly achieved directly from PET images due to the difficulty of accurately segmenting reference regions from PET images with low resolution and high noise. The integrated positron emission tomography-magnetic resonance imaging (PET-MRI) can simultaneously acquire MRI images and PET images, hence the combination of MRI image and PET image is expected to improve the accuracy of SUVR.

Purpose

This paper study aims to investigate the effect of MRI segmentation and PET segmentation on SURV calculation to improve the PET-MRI brain quantitative accuracy.

Methods

First of all, integrated PET-MRI was used to acquire MRI and PET images of 12-age-controlled healthy volunteers simultaneously. Then the MRI images and PET images were segmented into reference regions by the atlas-based method. Based on reference regions derived from MRI and PET respectively, the SUVRs of left / right cerebrum, cerebral cortex, cerebral white matter, frontal lobe, parietal lobe, temporal lobe and occipital lobe were calculated. For each group of SUVRs, the coefficient of variation (CV) of SUVRs was calculated to measure consistency level. Finally, quantitative analysis was performed to evaluate which segmentation method offered better SUVR consistency among volunteers.

Results

CV of SUVRs based on cerebellar gray matter from MRI images and PET images were 0.020/0.021, 0.023/0.026, 0.031/0.028, 0.028/0.031, 0.033/0.036, 0.022/0.024, 0.044/0.045 and 0.052/0.055, 0.054/0.055, 0.058/0.063, 0.053/0.058, 0.063/0.065, 0.048/0.050, 0.059/0.065 respectively. When the cerebellum was chosen as reference region, MRI results and PET results were 0.017/0.019, 0.021/0.025, 0.029/0.025, 0.026/0.030, 0.032/0.036, 0.020/0.022, 0.044/0.045 and 0.046/0.050,0.049/0.051, 0.052/0.057, 0.048/0.054, 0.059/0.061, 0.044/0.045, 0.056/0.062 respectively.

Conclusions

Compared with SUVRs based on reference region segmented from PET images, SUVRs based on reference region segmented from MRI images have better consistency with smaller coefficient of variation.

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Development of a cold cathode X-ray tube based on the Super-aligned arrays of carbon nanotubes
Lihua TANG, Guoguang ZHANG, Duanliang ZHOU, Peng LIU, Kaili JIANG
Nuclear Techniques    2020, 43 (4): 40401-040401.   DOI: 10.11889/j.0253-3219.2020.hjs.43.040401
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Background

The cold cathode X-ray tube is a key component of static CT system. Since the discovery of super-aligned arrays of carbon nanotubes, their applications in X-ray tubes have been gradually developed.

Purpose

This study aims to design and implement a cold cathode X-ray tube based on super-aligned arrays of carbon nanotubes.

Methods

The cold cathode X-ray tube was developed by designing a new X-ray tube structure and adopting a new X-ray tube preparation process. The acetylene was taken as carbon source gas, the super-aligned arrays of carbon nanotubes were prepared by using the chemical vapor deposition method. Then the cold cathode X-ray tube based on the technology of super aligned carbon nanotubes was developed by taking the nanotubes as electron source, and the performance of the developed X-ray tube was tested. Both the I-V characteristic curve and the X-ray focus size were obtained.

Results

Results shown on the I-V characteristic curve indicates the maximum emission current of this developed cold cathode X-ray tube is 5.0 mA when the gate voltage is 2 373 V. The focus size determined by the pinhole imaging is 0.6 mm×1.6 mm. When the anode high voltage is below 130 kV, the X-ray tube works stably.

Conclusions

This study lays a foundation for the development of pulsed X-ray source and static CT security system.

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Proposal for X-ray vortices production based on nonlinear laser Compton scattering
Heping GENG, Hailong WU, Jianhui CHEN, Zhentang ZHAO
Nuclear Techniques    2020, 43 (7): 70201-070201.   DOI: 10.11889/j.0253-3219.2020.hjs.43.070201
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Background

An optical vortex is an electromagnetic wave with a phase that varies azimuthally along the direction of propagation. The generation and application research of X-ray vortices are becoming more and more popular in recent years.

Purpose

This study aims to propose a generation scheme of a compact and inexpensive X-ray vortices source based on nonlinear laser Compton scattering (LCS).

Methods

Laser Compton scattering (LCS) was caused by high power circularly polarized light and relativistic electron beam. This LCS provided a practical method for generating tunable, near-monochromatic, well-collimated X-rays in a compact, relatively inexpensive source.

Results

Photons with energy of 1 keV is produced by head on nonlinear LCS interaction of 6.5 MeV electron beam and 800 nm Ti: Sapphire laser beam.

Conclusions

Compared with synchrotron, X-ray vortices source based on nonlinear LCS is a compact and inexpensive source. It provides a practical method for the laboratory to research the generation and application of X-ray vortices.

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Study on the sustainability of thorium uranium fuel in Molten Salt Reactor under on-line plutonium loading model
Changqing YU, Guifeng ZHU, Shaopeng XIA, Yang ZOU, Xiaohan YU
Nuclear Techniques    2020, 43 (3): 30601-030601.   DOI: 10.11889/j.0253-3219.2020.hjs.43.030601
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Background

Thorium-uranium sustainability of molten salt reactor usually relies heavily on online reprocessing technology, which is still immature at the present.

Purpose

The study aims to use reactor-grade plutonium online to achieve233U self-sustaining and burn reactor-grade plutonium based on the FLiBe carrier salt and Th/233U starter reactor.

Methods

Based on Scale6.1, the program of molten salt reactor feeding and reprocessing sequence (MSR-RRS) was developed. The database ENDF /B-VII Library of group 238 was adopted for simulation.Single cell models were used to analyze the performance of233U self-sustaining and plutonium utilization at different molten salt volume fraction (VF) and neutron loss ratio.

Results & Conclusions

It is found that233U self-sustaining could be achieved in a large range from 10%VF to 85%VF, and233U have the best breeding ability at about 43%VF, of which the utilization of plutonium is worst. When the VF becomes smaller or larger, the utilization of plutonium always becomes smaller. It is more beneficial to burn plutonium in the low VF region. When VF is 10%~15%, the burning ratio of plutonium is the highest, corresponding to 75%. In addition, the neutron loss ratio is positively proportional to the burnup of plutonium, and has little influence on the self-sustaining performance of233U.

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Simulation experiment study on release of fission gas at fuel cladding failure
Leihao DONG Bing LI Chenyue YIN Junlian WANG Dezhong LI
Nuclear Techniques    2019, 42 (12): 120601-120601.   DOI: 10.11889/j.0253-3219.2019.hjs.42.120601
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Background

When fuel rod cladding failure occurs, the defect needs to be determined and information needs to be provided for system response in time. Escape rate of fission gas is adopted to reflect the defect size. However, there is hardly researches on mechanisms of gas release.

Purpose

This paper studies the effect of unsteady process, the pressure and temperature of the coolant on the instantaneous escape rate of the rod cladding breach by experimental simulation.

Methods

First of all, the experimental apparatus was designed on the base of geometric similarity, flow similarity and flashing similarity. Then, influence of coolant pressure and temperature in a subchannel was investigated by using computational fluid dynamics (CFD) methods. Effect of flashing on unsteady process and escape rate in short-term were analysed.

Results

The results indicate that unsteady process has no distinct effect on release of gas at defect size of 0.5 mm. Long-term escape rate remains steady during experiments and release process can be described by first-order kinetics. At the same coolant pressure, long-term escape rate increases when coolant temperature changes from 90 ℃ to 110 ℃. At the same coolant temperature, long-term escape rate decreases when coolant pressure changes from 0.3 MPa to 0.5 MPa.

Conclusions

A negative correlation is found between long-term escape rate and subcooled temperature, which indicates that liquid layer formed on the defect has impact on fission gas release.

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The effect of scram rod drop time on the consequences of molten salt reactor reactivity insertion transient
Kai WANG, Xiaowei JIAO, Qun YANG, Yanhua WANG Chaoqun WU, Zhaozhong HE
Nuclear Techniques    2020, 43 (9): 90606-090606.   DOI: 10.11889/j.0253-3219.2020.hjs.43.090606
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Background

The scram rod drop time is an important parameter for reactor safety analysis, which is of great significance to the safety of molten salt reactor (MSR). The process and the consequences of the design basis events of the MSR will be significantly influenced by the dropping time of scram rod.

Purpose

This study aims to analyse the effect of the scram rod drop time on the consequences of MSR reactivity insertion transient.

Methods

First of all, the RELAP-MS based RELAP5-TMSR (reactor excursion and leak analysis program-thorium molten salt reactor) code was employed to establish the safety analysis model for the transient simulation of TMSR-LF. Then, the sensitivity of control rod withdrawal speed to transient consequences was analyzed, next, reactivity introduction event caused by the withdrawal of a control rod at full power was taken into account to analyse the vartions of power, temperatures of fuel salt and structure materials. Influence of scram rod dropping time in emergency shutdown on transient consequences of reactivity introduction in MSR was analyzed.

Results

Even if the scram rod drop time reaches as long as 10 min, the maximum temperature of Harrington alloy is 708.2 °C, and the maximum temperature of fuel salt is 709.2 °C, which is below the safety limit.

Conclusions

The molten salt reactor has good safety characteristics, low requirements for scram rod drop time, and the ability to deal with reactivity insertion event.

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