Integrated positron emission tomography (PET) / magnetic resonance imaging (MRI) is a multimodal imaging system which can acquire PET and MRI images simultaneously. Due to the unique advantages in reflecting the anatomical structure and physiological function, PET/MRI has been widely commonly used in diagnosis of many brain diseases. Brain segmentation is of great significance to the quantitative study of brain images and the common method used in clinical diagnosis is atlas-based brain segmentation, which can be applied to both MRI images and PET images. Brain segmentation based on atlas for integrated PET/MRI image system only needs one modelity as the segmentation results can be mapped to another modelity.

This study aims to determine which modality should be used for atlas-based segmentation for high definition (HD) integrated PET/MRI image.

Comparative experiments with two image groups were designed and performed. In the first group, 150 PET images were registered to PET brain template to obtain brain segmentation. In the second group, 150 MRI images were registered to MRI brain template to obtain brain segmentation. Six regions were selected to calculate the dice value. Comparing the segmentation results of the two sets of images with their results based on first, the modality with a higher average dice value would be more suitable for atlas-based brain segmentation.

In PET group, the dice values of six regions were 0.62, 0.55, 0.63, 0.62, 0.71 and 0.69, respectively. In MRI group, the dice values of six regions were 0.68, 0.64, 0.79, 0.81, 0.77 and 0.79. The error coming from registering PET images to PET brain template was larger than that of registering MRI images to MRI brain template.

PET-based segmentation accuracy is lower than MRI-based segmentation precision, hence the MRI image is more suitable for atlas-based brain segmentation.

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.

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.

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.

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.

Traditional charge-sensitive preamplifiers use high-resistance resistors as low-frequency feedback circuit. The thermal noise introduced by high-resistance resistors is the main source of preamplifier noise.

This study aims to design and develop a novel charge-sensitive preamplifier by using N-channel junction field effect transistor and RC (Resistor-Capacitance) low-pass network instead of traditional high resistance feedback resistor.

A junction field-effect transistor and an integrated operational amplifier were used to form an amplifying circuit with advantages of high input impedance and large open-loop gain. A high-pass loop was formed by a small capacitance capacitor to provide a high-frequency feedback loop for the circuit and integrates nuclear pulse current at the same time. The RC low-pass network constituted a DC (direct current) feedback loop to provide a stable DC operating point for the circuit, and a voltage divider for the N-channel junction field effect transistor operating in a forward bias state to realize a feedback capacitor for continuous discharge of its charge.

The charge-sensitive preamplifier was connected with BPX66 Si-PIN detector and the ²⁴¹Am source was measured at room temperature. The energy resolution of 3.03%@59.5 keV was achieved.

Compared with the traditional resistive capacitance feedback charge-sensitive amplifier, this circuit can effectively over-come the noise introduced by the large-resistance feedback resistor, especially for semiconductor detectors such as Si-PIN.

China Academy of Engineering Physics THz Free electron laser (CAEP THz FEL), referred to as CTFEL, is the first scientific facility in China that can provide users with high power and wide-spectrum terahertz waves. As an accelerator-based radiation source, magnet is one of the most important components for the transportation, measurement and manipulation of electron bunch.

This study aims at the design and measurement of magnets to satisfy that requirements of CTFEL.

According to the specifications of CTFEL magnets, the magnet system was designed to consist three solenoids, three 45° dipoles, one 90° dipole, six circular quadrupoles and six square quadrupoles. The problems of design and their solution schemes were described. The magnetic field distribution, integral field distribution, transverse field distribution and magnetic axis were measured.

The test results show that all magnets satisfied the specification requirements. At present, all magnets have been completely installed and commissioned to ensure the laser operation of the CTFEL facility.

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.

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.

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.

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%.

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

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.

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

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.

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

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.

There is a strong coupling between the neutronics and thermal-hydraulics in the non-moderated can-type core of molten salt fast reactor (MSFR).

This work aims to develop and verify coupled code for steady-state neutronics and thermal-hydraulics for the MSFR.

The coupling code was developed using python programming language to exchange the power distribution, fuel salt temperature and density distributions between OpenMC (Monte Carlo particle transport simulation code) and OpenFOAM (computational fluid dynamics software). Based on the coupling code, a benchmark model of MSFR was established, and the effects of the number of neutonics region division and the different initial conditions on the k _eff, fuel salt velocity and temperature distributions were studied. Finally, the simulation results were compared with the reference results of MSFR.

The three-dimensional power distribution, neutron flux distribution, fuel salt velocity field and temperature field distributions can be obtained by using this coupled code. The benchmark of MSFR shows that different initial conditions have no effect on k _eff, and an alternative number and scheme of neutronics region division are recommended. The simulation results keep a good agreement with the reference results of MSFR.

This coupled code can provide reliable results for the steady-state neutronics and thermal-hydraulics coupling of MSFR.

A double multilayer monochromator (DMM) is required in the time-resolved ultra small angle X-ray scattering (USAXS) beamline during Shanghai Synchrotron Radiation Facility (SSRF) phase II construction.

This study aims at the structure design of DMM for the USAXS beamline of SSRF to satisfy the requirements.

Based on condition of indirectly cooled by liquid nitrogen, thermal slope error of the multilayer was analyzed and detailed mechanical design of the DMM was introduced. Based on the analysis of the errors caused by the multilayer crystal optics attitude adjustment and the planar four-bar motion mechanism, a Sinbar mechanism based on Pivot and bearing rotating was designed for the DMM. [Results &

Basical analysis and calculation results show the design scheme can meet the requirements of monochromator stability and ultra-high angle resolution. At present, the monochromator is manufacturing and its performance will be tested and reported in the future.

The current beam lines structure design cannot satisfy the requirement of the first combined beamline station with soft and hard X-rays in Shanghai synchrotron radiation facility (SSRF).

This study aims to design the super-small angle Canted front-end at SSRF to support a wide-energy-range experimental platform with multiple methods for energy material research.

Two undulators, elliptical polarization undulator (EPU) and in vacuum undulator (IVU), were employed in the wide-range energy material beamline (E-Line) that contains soft and hard X-rays located in the straight line with a Canted angle of 2 mrad. The separated plane mirror, SM1, was designed to be located at the front-end. After SM1, the soft line was deflected 2.4°, allowing two dedicated beam lines to be set.

The two beam lines share the front-end components, and can independently operate the components of the front-end. The front-end of E-Line adopt a new structure and layout different from the standard ones that can handle the heat load up to 7.81 kW. Compared with the key equipment of other common insert device front-end with only one through-light aperture, the one of this front-end was designed with two through-light apertures.

The installation of E-Line front-end has been accomplished, and the structure and layout fully satisfy the technical requirements of the beamline.

The temperature of the bolt connecting structure is around 650 ℃ in the scram system of the thorium molten salt reactor-liquid fuel 1 (TMSR-LF1) and the connecting components include three kinds of material, which have different coefficients of thermal expansion. Thermal expansion during the heating process, from room temperature to 650 ℃, and creep in the long lifetime of reactor will affect the bolt pretension, which may touch the safety of the scram system.

This study aims to analyse the stress relaxation of the bolting structure, and assess structural safety for the scram system of TMSR-LF1.

The ANSYS program was employed for the mechanical analysis of the bolt connecting model. The stress analysis and creep stress-relaxation analysis of the structure under the combined action of bolting preload and thermal expansion were performed.

The high temperature creep of bolted structural materials and the variation of stress relaxation caused by the creep and its influence on the pre-tightening force of bolted connection structures are obtained for the whole lifetime of the reactor. And the evaluation of the bolt is completed under.

According to American society of mechanical engineers (ASME) standard in coordinate with ASME-III-5-HBB rules for bolt mechanical analysis and safety evaluation, the connecting bolt structure designed for TMSR-LF1 is demonstrated safe and reliable in the whole lifetime.

In medical diagnostic radiology, detailed knowledge of X-ray spectra is required for evaluating the image quality and patients’ or staff’s radiation dose.

This study aims to simulate medical diagnostic X-ray spectra by using Monte Carlo method.

First of all, a simplified X-ray machine head geometry model was constructed in MCNP (A general Monte Carlo N-Particle transport code) software. Then, the X-ray spectra and surface source data files in the output window were calculated under tube voltage ranging from 50 kV_P to 150 kV_P, filter ranging from 0.5 mm (Al) to 5 mm (Al) and anode angles ranging from 6° to 14°.

Database of medical diagnostic X-ray spectra and surface sources in the output window are obtained by various machine X-ray head parameters. The calculated spectra are comparable to those of other X-ray spectra software.

X-ray source and its spectra can be correctly simulated by electronically hitting the target through Monte Carlo simulation, providing a basis for future applications.

The particle accelerator has a short downtime and requires high relative accuracy between magnets.

This study aims to improve the smoothing analysis efficiency of beam orbit by using moving least squares method.

Firstly, the original smoothed data was preprocessed to make the ring magnet data linearly distributed. Secondly, the fitting area was meshed, the grid points were extracted and the appropriate basis function and weight function were selected. Then, three indicators of the smooth analysis were given and the whole calculation process was designed. Finally, the smoothing effects of the averaging method, the least squares fitting and iteration method and the method of this paper were compared and analyzed by simulation data.

The experimental results show that the fitting curve obtained by the method of this paper is the smoothest and the magnet adjustment times are the least under the same conditions.

To a certain extent, the adjustment time is saved and the adjustment efficiency is improved.

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.

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.

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.

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

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

There are two methods to test the single photoelectron spectra (SPE) performance of the photomultiplier tubes (PMT) and Silicon Photomultiplie (SiPMT) with either the charge-to-digital-converter (QDC) module or flash amplitude-to-digital-converter (FADC) module.

This study aims to investigate the difference of data acquisition between FADC and QDC for single photoelectron spectra (SPE) of photoelectric detector.

Single photoelectron spectra (SPE) of 20-inch PMTs of the same model, as well as SiPMT of same mode, were measured under the same testing conditions using FADC module and QDC module. Gain, signal events, detection efficiency, the ratio of peak to valley and energy resolution were compared in details.

Both QDC and FADC can be used as data acquisition tools for PMT SPE test, but each has its own advantages and disadvantages.

According to the system’s specific demand for photoelectric detector, either of the two modules could be chosen.

Eccentricity in the manufacture and assembly of nuclear fuel assemblies will affect the annular channel.

This study aims to investigate the characteristics of the single-phase flow in narrow annular channels.

Computational fluid dynamics (CFD) simulation on single-phase flow friction characteristic in straight annuli channel with different width (h=0.775~1.742 mm, 0.69<r _i/r _o<0.86) in ranges of laminar flow (300<Re<1 800) and fully developed turbulent flow (10⁴<Re<10⁵) were carried out by commercial code FLUENT. The influence of different eccentricity (e=0.01~0.5) was also considered.

The results show that for laminar flow the simulated friction factors are completely agreed with that of the analytic solution. When the Reynolds number is in the range of 10⁴~5×10⁴, the Blausius correlation achieves more exact results with CFD; and while the Reynolds number is in the range of 5×10⁴~10⁵, the McAdams correlation gets more consistent results with CFD.

Based on the above conclusions, proposed correlation f=0.257 5Re ^-0.23 can well predict in the whole Reynolds number in the range of 10⁴~10⁵. Furthermore, the friction factor is a function of eccentricity, a relatively weak function of width, and independent of the Reynolds number.

A real-time, high position resolved in-vivo dose measurement of critical health tissues and tumors is one of the most direct quality assurance (QA) tools in the radiotherapy. Plastic scintillator fiber dosimeters (PSFDs) have great advantages in dose verification due to its small size, good radiation resistance and good tissue equivalence.

This study aims to develop a plastic scintillation fiber dosimeter （PSFD） based on silicon photomultiplier (SiPM)， and investigate its performance in clinical applications.

With a stable LED pulse optical source, the leakage current of SiPM was measured by the picoammeter. Time stability and repeatability of the dosimeter, temperature response and the influence of the transmission fiber curvature on the SiPM leakage current were systematically studied. The dynamic range of the dosimeter was measured by using a small animal radiotherapy machine and LED pulse optical source.

The results show that the leakage current changes <1% when the dosimeter works continuously for 8 h at constant temperature of 20 ℃, and the leakage current changes <0.5% during 32 h of intermittent operation. When the temperature change is less than 0.5 ℃, or the transmission fiber radius of curvature is greater than 11 cm, the output current change is less than 1%. The linear dynamic range of the dosimeter measurement is 100~9 000 cGy?min^-1.

The developed dosimeter basically meets the accuracy requirements of the clinical dose verification.

Slow positron annihilation lifetime spectrum measurement is an important analytical method for high sensitivity and non-destructive detection of material micro-defects. Pulsed positron system is the core component of this technology.

This study aims to obtain periodic positron pulses with high time resolution for lifetime measurement and to provide a signal marking the time of positron generation.

In this paper, the Parmela program was applied to simulate and calculate the effect of different beam parameters on positrons bunching based on the “Prebuncher-Chopper” pulsed system. Effect of different beam parameters on 150 ps (half-width) bunching was simulated and compared with calculation results of “Prebuncher-Chopper” bunching system.

The results show that increasing beam energy, reducing beam energy spread and reducing beam spot size are beneficial to improve pulse efficiency. Moreover, when the positron beam energy is greater than 500 eV, the energy spread is less than 5 eV and the beam spot is less than 12 mm, the positron utilization ratio is more than 20% and the bunching efficiency is more than 85% using “Prebuncher-Chopper” pulsed system.

In contrast to the “Chopper-Prebuncher” system, “Prebuncher-Chopper” pulsed system can provide a higher positron utilization rate under the same beam parameters. Meanwhile, the time resolution (≤150 ps) and the bunching efficiency (≤85%) meet the measurement requirement.

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.

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.

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.

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.

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

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.

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

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.

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.

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.

Carbon stripping foil as a stripper is one of the important components of medical heavy ion accelerator. It is essential to develop the carbon stripping foil that meets the requirements of medical heavy ion accelerators.

This study aims to develop U-shaped carbon foil for medical heavy ion accelerator.

AC carbon arc discharge method was employed to develop the carbon stripping foil, and its properties were measured by the methods of scanning electron microscopy (SEM) and Raman characterization. The “U-shaped” target frame was used to ensure that target frame did not affect the normal operation of ions in the injected ring. The edge of target frame was designed to be as narrow as 2 mm wide, and the effective area of the carbon stripping foil was 1 600 mm² (40 mm × 40 mm).

The thickness of the carbon stripping foil is 15 μg·cm^-2, and the thickness uniformity is 97.65%. The SEM test results show that the surface of the carbon stripping film is smooth and the internal structure is compact. The Raman test results show that the G peak near 1 580 cm^-1 is stronger than the D peak located near 1 300 cm^-1, indicating the degree of graphitization of the film is higher, and the 2D peak near 2 700 cm^-1 is weak, indicating that the number of graphite molecules is higher.

The carbon stripping foil developed in this study has a certain mechanical toughness thereby completing the automatic mold changing process of the carbon stripping foil.

The high-fidelity nuclear reactor model requires a large amount of computing resources and a high-performance computing platform. High-performance computing platforms are cumbersome to operate and are not conducive to designers, while the cloud platform has the characteristics of super large scale and easy to use, hence has good application value for neutronics calculation.

This study aims to establish a neutron computing cloud platform for users.

Combined with cloud computing technology, a neutron computing cloud platform based on Software as a Service (SaaS) mode was designed and implemented. Neutronics computing functions and related databases were set up to run in the cloud to provide SaaS mode computing services for end users.

Users can use computing resources anytime and anywhere through the browsers to effectively improve the efficiency of neutronics calculation.

The cloud platform proposed in this paper can be used for general nuclear design computation.

Microchannel plate (MCP) is an electron multiplier device with an ultra-fast time response, which can be directly used for the detection of charged particles. The gain of MCP has a large influence on the properties of the neutron detector.

This study aims to investigate the gain of the MCP through theoretical simulation and experimental test.

First of all,a sub-ns time-response neutron detector based on recoiled proton and MCP was developed for experimental test.The Monte Carlo method was used to simulate the number of secondary electrons generated by a single electron multiplying on a single microchannel, and the electron gain of a single-chip MCP at different voltages was calculated. Then, the gain characteristics of two MCPs were studied by alpha particle experiments.

The calculation results show that the theoretical gain of a single-chip MCP is consistent with the MCP factory inspection report. The experimental results show that when the supply voltage of each MCP is 800 V, the gain of double MCP is about 9.0×10⁶.

The method clarified in the paper is reliable and feasible, and provides a new technical approach for the study of MCP gain. It also provides a theoretical basis for studying the performance of MCP neutron detectors.

The simulation calculation of shielding performance of radiation protection materials at home and abroad is usually limited to one simulation of the Monte Carlo method, while the fine-grained calculation of gamma ray shielding of secondary products is less.

This study aims to analyze shielding performance and activation products of boron-containing stainless steel materials.

Monte Carlo particle transport program combined with fuel consumption calculation and analysis program (MCNP5/ORIGEN2.1) was employed to calculate and analyze the shielding properties and activation products of stainless steel materials for radiation protection. Combined with the specific requirements of radiation shielding design, evaluation method of neutron/gamma integrated shielding performance was proposed. Based on the simplified model of three-layer shielding structure of single-layer external irradiation of nuclear reactor, the shielding effect of neutron in the neutron/γ mixed radiation field, photon, (n, γ) reaction photons and secondary activation product photons inside the material were simulated by boron stainless steel and ordinary stainless steel, and the overall shielding performance of the protective material was evaluated.

The actual average photon transmittance of boron stainless steel is slightly lower than that of ordinary stainless steel, both of them have the same gamma-ray shielding performance, but boron stainless steel has advantages over ordinary stainless steel in weight reduction.

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.

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

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.

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%.

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

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.

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.

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.

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.

High temperature molten salt pump, the design temperature can go up to 700 °C, is one of the key equipment in the primary loop in the simulator of Thorium-based Molten Salt Reactor with Solid Fuel (TMSR-SF0). The structural integrity of the pump is crucial to the safe operation of the reactor.

This study aims to reduce the load-controlled stress level of the molten salt pump tank of TMSR-SF0 to meet the evaluation requirements of American Society of Mechanical Engineers (ASME) BPV code.

Three different schemes of the reinforcing rib for the bottom flat head including triangular shape, #-shape, and dual-#-shape were proposed and analyzed to optimize the initial tank design. The influence of the reinforcing rib spacing on the stress of pump tank in the dual-# scheme had been studied, and the optimal combination of parameters was found. According to the results of above analyses, the final tank design scheme was obtained, and then evaluated in accordance with ASME BPV code section III, Division 5.

The results show that all of the three schemes can significantly reduce the stress level of the pump tank, dual-#-shape scheme was the best, and then followed by the #-shape scheme and triangular shape scheme.

The final reinforcing rib design scheme for the bottom flat head of the pump tank is a dual-# scheme, which can reduce its stress from 413.4 MPa to 65.4 MPa, with a drop of 84.2%, and meet the stress assessment limit of ASME standard.

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.

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

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.

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%.

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

Circular electron positron collider (CEPC) is a high-energy accelerator, some beam produced by CEPC but not injected to energy intensifier need to be absorbed properly to keep the safety of the machine and the environment.

This study aims to design the beam dump, and give a process of design for the beam dumps used in high-energy accelerators.

The Monte-Carlo program FLUKA was employed for the preliminary design scheme of CEPC linac beam dump. As the basis of absorber design, different calculating methods of beam range was proposed and checked with Empirical formula.

The relationship between material selection of shield and overall shielding thickness is revealed. The introduction of variance reduction technique improves the accuracy of calculation results.

The empirical formula to estimate the stop range of electron is basically correct and same with the Monte-Carlo simulation. And the design itself is helpful to CEPC Project.

It is very important to locate ruptured fuel assemblies rapidly and accurately not only for emergency core refueling, but also for shortening critical path of overhaul.

This study aims at location of fuel assemblies failure using the activity ratio of ¹³⁴Cs and ¹³⁷Cs.

The relationship between the ratio of ¹³⁴Cs to ¹³⁷Cs activity and fuel consumption in the fuel assembly was theoretically calculated, and the theoretical model was modified by ORIGEN software.

It is found that the activity ratio of ¹³⁴Cs to ¹³⁷Cs increases with the increase of the burn-up, and decreases with the increase of fuel assembly enrichment. With the improved ¹³⁴Cs to ¹³⁷Cs activity ratio and burnup model, the burnup of damaged fuel assemblies at different enrichment levels in pressurized water reactor (PWR) nuclear power plants can be determined, and then the damaged fuel assemblies can be quickly located.

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.

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.

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.

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.

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

Material level detection is a very important issue for the automatic control of thermal power. How to monitor the material and powder level has become an urgent problem for the thermal power plant.

This study aims to find out the best detection angle and switching point to provide theoretical guidance for instrument development and sensitivity improvement.

First of all, Monte Carlo simulation was applied to the optimum design of the best detection angle for non-radioactive nuclear ash hopper level meter in the range of 0°~90°. Then the angle between the ash bucket wall and the horizontal plane for the optimum detection angle was determinated. Finally, a complete model of dust hopper and passive nuclear level gauge for electrostatic precipitator (ESP) was established, and the high and low switch points material level were by "second derivative method".

When the angle between the probe and the horizontal line reaches 30°, the maximum energy flux is detected while the angle between the ash bucket wall and the horizontal plane is 61.224°. The absorption dose rate curve of material level meter with different fly ash height at 30° detection angle is obtained.

This study provides theoretical guidance for the development of non-radioactive nuclear ash hopper level meter instrument and improvement of sensitivity in thermal power plants.

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.

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

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.

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.

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.

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.

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.

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.

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.

Silicon photomultiplier (SiPM) also named multi-pixel photon counter (MPPC) has excellent performance, but it is difficult to carry out large scale testing due to the limitations of the power supply board.

This study aims to test the performance of the self-developed voltage-adjustable, batch-programmable SiPM low-voltage power supply module.

The performance of the new type of SiPM power driver board developed by our laboratory was tested and analyzed by the method of comparative test with commercial power supply. [Results &

The performances of proposed power module are comparable to that of the commercial module, and satisfy the reqiurments of SiPM batch test.

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.

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

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.

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.

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.

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

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.

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.

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.

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.

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.

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).

The radiation effects of semiconductor devices include single event upset effect, total ionizing dose effect and dose rate effect. The total ionizing dose effect on electronic systems becomes a priority for the improvement of reliability of radiation-tolerance robots.

This study aims to measure the irradiation damage dose of STM32 microcontroller unit fabricated by 180 nm complementary metal oxide semiconductor(CMOS) technology with on-line and off-line experimental testing approaches.

A test system which consisted of minimum circuits, dosimeter, communication circuit and host computer was developed. On-line and off-line irradiation experiments were performed on 89 samples using ⁶⁰Co source with different dose rates. Among these samples, 14 samples were on-line irradiated under 63.3 Gy(Si)?h^-1 and 101.2 Gy(Si)?h^-1 dose rates whilst 75 samples were off-line irradiated under dose rates range of 227.2 Gy(Si)?h^-1 to 855.0 Gy(Si)?h^-1.

The irradiation damage dose are (235.4±16.4) Gy(Si) and (197.4±13.0) Gy(Si), respectively, corresponding to the on-line testing with 63.3 Gy(Si)?h^-1 and 101.2 Gy(Si)?h^-1 dose rates. The irradiation damage dose of off-line testing is between 391.5 Gy(Si) and 497.6 Gy(Si).

On chip flash memory is the first damaged hardware unit in STM32 microprocessor, and the tolerant dose limit of off-line test is significantly higher than that of on-line test.

Lithium is an important component of coolant in liquid molten salt reactor (MSR). The neutron absorption cross section of the isotope ⁶Li is much larger than that of ⁷Li. Hence, the content of ⁶Li in the coolant has an important influence on the Th-U conversion performance for MSR.

This paper aims to provide an appropriate reference for the choice of ⁷Li enrichment in the engineering design of molten salt reactor by studying the influence of ⁷Li enrichment in FLi/FLiBe on Th-U conversion performance for molten salt fast reactor (MSFR).

With the help of molten salt reactor reprocessing sequence (MSR-RS), neutron spectrum, ²³³U inventory, conversion ratio and ²³³U net production, evolution of Li and tritium production with ⁷Li enrichment from 99.5% to 99.995% were explored on MSFR with FLi and FLiBe, respectively.

The computation results show that MSFR with FLi has a better Th-U conversion performance than that with FLiBe, and the influence of ⁷Li enrichment on Th-U conversion performance becomes wake when ⁷Li enrichment is higher than 99.9%. Compared with the 99.995% ⁷Li enrichment, the Th-U conversion ratio of 99.9% ⁷Li enrichment decreases by about 1.6% and the tritium production increases by about 8%.

Considering the cost of enriching ⁷Li and the Th-U conversion performance, a 99.9% ⁷Li enrichment is recommended for MSFR with both FLi and FLiBe.