最新刊期
卷 38 ， 期 9 ， 2015
- 摘要：Background: Diffraction enhanced imaging (DEI) is a powerful phase contrast imaging technique. Purpose: This study aims to investigate the noise properties of a new simple cosine fitting radiography for DEI based on the angular signal response imaging prototype. Methods: The rocking curve can be treated as a angular signal response and a simple multi-information retrieval algorithm based on the cosine function fitting. A comprehensive analysis of noise properties in DEI, based on a noise model including the fluctuation of the photon source, and a bias of the analyzer crystal are also given. The validations have been performed with Monte Carlo simulations based on the Geant4 toolkit combined with the refractive process of X-ray and synchrotron radiation experimental data. Results: The cosine fitting radiography (CFR) has been verified by Monte Carlo simulations and experimental data which are in good agreement with each other. The noise penalty is drastically reduced with high photon flux, high visibility and high angular precision. Conclusions: Based on the angular signal response function prototype, we analyze and calculate the noise properties of DEI. In addition, the analytical method can build a strong connection between DEI and grating-based phase contrast imaging (GDPCI) and widely suitable for all kinds of measurement noises in angular signal response imaging prototype. The analysis is useful to understand the noise characteristics of DEI images and improve the signal-noise-ratio of the extracted information for biomedical imaging and material science. Abstract关键词：Diffraction enhanced imaging;Noise analysis;Cosine fitting radiography;Monte Carlo simulations
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发布时间：2021-03-03 - 摘要：Background: X-ray machine is the most-extensively-used X-ray source in industrial CT, due to its anode effect and the restrictions of its own structure, the radiation intensity distribution is not uniform. Purpose: The aim is to research and measure the radiation intensity distribution of X-ray machine as a vital part of imaging correction and the foundation for the precise application of X-ray machine. Methods: The CsI(Tl) scintillation and photodiode detector is used to measure the radiation intensity distribution of the MXR225/22 X-ray machine (made by Swiss COMET Inc.) along with various angles on different axis. At the same time, the radiation intensity distribution is simulated by Monte Carlo method. Results: The “broadening effect” is observed, and the boundary radiation intensity distribution broadening phenomena can be explained thereby. The radiation intensity distributions of the large and small focal are compared, and the reason for the difference in the cathode ends is analyzed. And the 2D radiation intensity distribution of X-ray machine is given. Conclusion: The results showed that in the 20° opening angle range (?10°?+10°), the radiation intensity distributes uniformly, the larger opening angle, the worse distribution uniformity. The radiation distribution extension occurs at the boundary of cathode side. Abstract关键词：Intensity distribution;X-ray machine;Industrial CT;Anode effect
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发布时间：2021-03-03 - 摘要：Background: The Accelerator Driven Subcritical System (ADS) uses a proton beam incident on a target to produce neutrons used in a nuclear reactor to process spent fuel in two ways: to accelerate its decomposition into non-radioactive waste, and to increase the rate at which it is recycled into nuclear fuel. Two cryomodules, each consisting of 7 superconducting spoke cavities, 7 superconducting magnets and 7 beam position monitors, are used to accelerate the proton beams from 3.2MeV to 10MeV. The superconducting magnet contains a solenoid for beam focusing and two correctors for orbit correction, it is a key component for ADS injection. Purpose: This study aims at a short superconducting magnet design to meet the required integral field strength and to reduce the leakage field at the nearby superconducting spoke cavities. The design current for the solenoid is 210 A. Methods: The main solenoid and two bucking solenoids plus the iron yoke were used to meet the leakage field requirements which is less than 1 G at a distance of 270 mm from the solenoid center. In order to shorten the magnet length to 170mm, special design methods were taken for the magnet cryostat by removing two conflicts flanges and replacing them with the direct Al ring seal methods. A kind of conducted the current leads similar as that of Large Hadron Collider (LHC) corrector magnets was applied to the 2.1-K, 3 100-Pa cryogenic system. The small store energy magnet led to the introduction of active quench detected system, which is much more reliable. Two short magnets and two spoke cavities were installed inside a test cryomodule to test the online operation properties of the SC magnet and the SC spoke cavity. Results: A quench performance in the vertical test shows that the operating current of the solenoid magnet can reach above 300 A after natural quenching on three occasions during current ramping (260A, 268A and 308A). Online operating test shows that two magnets can work at 4.2K and 2.1K, respectively. The quench protection system worked well when two quenches occurred as the liquid helium level decreased. Conclusion: The online operation for the two magnets confirms the physical and the mechanical design, the reliability of the quench detection technique. Abstract关键词：Bucking solenoid;Quench detection;Vertical test;Persistent current effect
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发布时间：2021-03-03 - 摘要：Background: 90Zr is a decay product of 90Sr, which may induce structural changes of radioactive waster forms. Purpose: In order to study the influence of decay product on the stability of perovskite-type SrTiO3 used for immobilizing 90Zr, C4H6O4Sr?0.5H2O, TiO2 and ZrOCl2?8H2O are used as the starting materials. Methods: The Zr-doped SrTiO3 synthesized can be generally represented as SrZrxTi1?xO3 (0≤x<1) with the high temperature solid reaction. The phases, structure and microcosmic shape of synthetic condensates were characterized by the X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Fourier Transform Infrared (FT-IR), and long-term chemical stability was studied at constant temperature of 90 oC. Results: The results indicate that the second phase of compounds is observed when the value of x is more than 0.5. The leaching rate of Sr2+ and Zr4+ in waste forms increase with the immersion time, while the highest leaching ratios for 42 d are no more than 0.0065 ?g?mL?1 and 0.01?g?mL?1, respectively. The crystalline phase and morphology of solidified SrZrxTi1?xO3 waste form are influenced by electron beam irradiation. Conclusion: This study results may provide technical support for long-time immobilization of the 90Sr. Abstract关键词：Perovskite-type;Waster forms;Leaching behavior;Radiation
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发布时间：2021-03-03 - 摘要：Background: According to the national standard of “Analytical Determination of Radium-226 in Water (GB/T 11212-1989)”, emanation-scintillation is widely used to monitor the content of 226Ra in water. Purpose: This study aims to optimize the analysis and mensuration conditions of emanation-scintillation method recommended in GB/T 11212-1989. Methods: The related parameters for mensuration of 226Ra, such as recovery rate, measuring moment and measuring instrument were investigated to identify the optimal working state by a series of experimental tests. Results: If the percent recovery indicated pretreatment loss was introduced, the mensuration result would be more accurate. The optimal measuring moment was 3?4 h after the complete collection of the Radon from the samples. The traditional FD-125 radon-thorium analyzer can be replaced by the portable AB-5R radon monitor which will be more convenient and flexible while keep the same performance. Conclusion: The relevant recommendations provide alternative solution for field measurement of 226Ra in water, and a design reference for the developing and updating of the GB/T 11212-1989 standard in future.Cited关键词：226Ra;Emanation-scintillation;Recovery;Measuring moment;Radon monitor
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发布时间：2021-03-03 - 摘要：Background: As a unique non-destructive testing technique, fast neutron radiography has been widely concerned in recent years. However, the fast neutron imaging detector with higher resolution and higher detection efficiency still needs to be researched. Purpose: A new fast neutron imaging detector consisting of a polyethylene (PE) converter and a microchannel plate (MCP), is proposed for 14.5-MeV fast neutron radiography. Simulation studies are conducted for the design aim. Methods: The yields and energy spectra of the recoil proton produced by 14.5-MeV fast neutron on the PE converter are simulated using Geant4 code. The yields and the energy spectra of the recoil proton under the different PE converter thicknesses are presented in order to determine the converter efficiency and the reasonable thickness of the PE converter. Less than 14.5 MeV, fast neutron incident, the electronic gain process in MCP is simulated using Geant4 code. In order to analyze spatial resolution, the electron beam spot images are recorded after MCP. Results: The simulation results show that the thickness of PE converter should be selected in the range of 2.5 mm, and the converter efficiency is about 0.37%. The electron images show that the electron beam spot diameter is slightly bigger than MCP aperture. Conclusion: It can be predicted that the spatial resolution of the detector is close to MCP aperture. Abstract关键词：Fast neutron radiography;Polyethylene converter;MCP;Electron gain;Spatial resolution
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发布时间：2021-03-03 - 摘要：Background: The Kilometer-square Array (KM2A) is one of main detector arrays in the Large High Altitude Air Shower Observatory (LHAASO). Thousands of detectors and front-end readout electronics spread over one square kilometers. In such a large-scale, dispersed high energy physics experiment, a flexible, efficient and reliable system for remote update of FPGAs (Field Programmable Gate Array) becomes significant. Purpose: This study aims to introduce a scheme to update FPGAs of the front-end readout electronics and reload firmware online without extra circuits while ensuring its reliability. Methods: The remote update based on MultiBoot and reload logic based on Internet Content Adaptation Protocol (ICAP) make it possible to update the firmware of all the FPGAs simultaneously. Results: The scheme proposed in this paper has successfully applied to the detector arrays in Yangbajing, Tibet. Its flexibility, convenience and reliability has been proved by the stable operation since October 2014. Conclusion: Remote update scheme based on MultiBoot makes it possible to update FPGAs without any extra circuits, thus literally reduces the cost of electronic systems while guaranteeing the reliability. Abstract关键词：KM2A;Remote update;MultiBoot;ICAP
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发布时间：2021-03-03 - 摘要：Background: The transient neutron radiation damage effect was an important parameter for evaluating radioresistance of electron device. Purpose: The aim is to obtain the response to transient irradiation of bipolar transistors under pulse neutron radiation. Methods: In this paper, the silicon bipolar transistors (3DK9D) with good similarity of parameters have been employed as the displacement damage monitors based on the liner relationship between the reciprocal of gain and the neutron flux. Response characteristic of pulse neutron radiation for this transistor was obtained by on-line measuring the variation of zero-frequency gain the along with accumulation of the neutron flux. Results: The transient neutron radiation damage effect on transistors was the combined action of ionizing damage and displacement damage. Conclusion: The results shown that the transient irradiation effect of transistors was more remarkable than steady irradiation with the same accumulative neutron flux. Abstract关键词：Bipolar transistor;Transient radiation effect;Pulse neutron irradiation;Direct current gain;Neutron flux
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发布时间：2021-03-03 - 摘要：Background: The architecture of the control system for the solid fuel molten-salt reactor (TMSR-SF) is based on the ABB’s 800XA series programmable logic controller (PLC) hardware. The 800XA series PLC is widely used in the power industry due to its unique reliable design, but there is a lack of step motor controller which is the key component for control rod drive mechanism (CRDM). Purpose: This study aims to configurate a ABB AC500 step motor controller CD552 into the 800XA series PLCs to realize stepper motor driven pulse output and position detector inputs decoding. This is a key module for reactor Rod Control and Position Indicator (RCPI) system. Methods: The Proifbus-DP interface of the 800XA series PLCs is adopted to connect the step motor controller CD522 via its CDI 542 module. The plug and play (P&P) functionality of CD552 is achieved and optimized to work coherently based on Proifbus-DP. During the configuration of the controller, by a flexible input and output registers assignment, it not only achieves custom controller function, but also simplifies the subsequent library programming. Results: Two main functions of RCPI were implemented with a very low failure rate at the level of 8×10?6 by analyzing of the reliability of the hardware’s configuration based on CD522. Conclusion: Such kind of hardware configuration and software optimization can meet various performance parameters of the RCPI system, such as travel stroke, speed control required accuracy and position detection precision, etc. Abstract关键词：TMSR;CD522;RCPI;Reliability analysis;Profibus-DP
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发布时间：2021-03-03 - 摘要：Background: Radiation therapy (RT) is a major part of the treatment of cancer and other tumor diseases by using penetrability radiation, such as X-ray, ?-ray. RT works by directly damaging the deoxyribonucleic acid (DNA) of tumor cells or indirectly creating charged particles (free radicals) within the cells, which can in turn damage DNA. As RT focused at the tumor tissue and provided a much larger absorbed dose than that in the surrounding healthy tissue, its side effect is much lighter than chemotherapy. Purpose: To destroy the whole of disease cells with minimal damage to the surrounding normal cells, which is the ultimate goal of RT, target-RT modalities have been developed. Methods: Owing to its excellent optical properties, Gold nanoparticle has drawn much attention. It has been proved that Gold nanoparticle is a good radiosensitizer of transferring keV energy radiation to micrometer-range photo-/Auger electrons. Recent development of nanotechnology has provided great opportunities for developing new RT modalities to enhance RT therapeutic efficacy by using gold nanoparticles. Results: A lot of multi-function nanoparticle systems have been designed to enhance RT therapeutic efficiency. Conclusion: Gold nanoparticles assisted target-RT has achieved greater therapeutic efficiency with less side effects and longer live time.Cited关键词：Radiation therapy;Gold nanoparticles;Tumor tissue
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发布时间：2021-03-03 - 摘要：Background: The multi-leaf collimator (MLC) is one of key components of modern medical accelerators for Intra-operative Radiation Therapy (IORT). The stability and accuracy of MLC’s control system will insure patients’ life security during radiation therapy. Comparing with the world’s top level, domestic MLC technologies falls behind not only in stability but also in accuracy. Purpose: This study aims to design a MLC control system satisfying the requirements of developing the first domestic IORT accelerator and closing the gap with the world advanced level. Methods: The MLC control system was reconfigurated by the System-on-a-Programmable-Chip (SOPC) technique based on the traditional MLC control system. By adding new function model, preventing Electromagnetic Interference (EMI) and other ways, the newly developed MLC control system can fulfill IORT accelerator’s function and mechanical installation requirements. Results and Conclusion: The test results show that the control system possess properties of full functionalities, redundant position feedback, conformity to national standards of medical instruments and insuring the R&D of IORT accelerator. Abstract关键词：MLC;Accelerator;FPGA;LabVIEW
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发布时间：2021-03-03 - 摘要：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.Cited关键词：Pressurized water reactor;Reactor core;Porous media;Transient conditions
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发布时间：2021-03-03 - 摘要：Background: In engineering application of steam generator (SG) for nuclear power plant (NPP), two limitations are imposed on the design of water tanks. One is that the water collected in the water tank cannot spill over to avoid the entrainment of water from the water tank. The other is that the size of the devices used in the SG is limited by the safety consideration and costs. Purpose: This study aims at the drainage performance of drain device in steam generator of CAP1400 to provide reliable data for the design of a drain device. Methods: The drainage performance of drain device in steam generator of CAP1400 was simulated through an experimental method with water and air under ambient temperature and pressure. A video camera is used to record liquid level at certain water flow rates range of 13.8?138.1 m3?h?1, and the recorded video images are processed by MATLAB program. Results: The experimental results show that the maximum water depth level in drain tank linearly increases with the water flow rate while the number of water entrance holes has no obvious effect on the drainage performance of drain device and the value of bottom surface slope angle has a little influence on it. Conclusion: Using a slope bottom plate can help draining water to some extent and the number of orifices has little effect on the liquid level of drain water tank. Abstract关键词：Steam generator;Drain tank;Liquid depth;MATLAB digital image processing
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发布时间：2021-03-03 - 摘要：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. Abstract关键词：Liquid metal;Speziale-Sarkar-Gatski (SSG);Sub-channels;Turbulent heat transfer
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发布时间：2021-03-03 - 摘要：Background: New material for the reactor shielding structure is one type of cast-steel impurity doping actinide elements have been adopted. The design parameters of the shielding performance testing device for the various parts of reactor can be obtained by Monte Carlo method. Purpose: This study aims to test the shielding performance of the shielding material of reactor. Methods: First of all, the testing device model was built based on a 252Cf neutron source. Three kinds of models (the thicknesses of the moderation layer, the protective layers of the neutron and gamma ray) are calculated respectively using the MCNP program for the shielding performance testing device. The GEANT4 program was used for the key moderation layer to verify the results obtained by the MCNP program. Results: Through the analysis of simulation results, we obtained optimal shielding materials and the thicknesses of material layer: moderator layer material is paraffin wax, which having a thickness of 8 cm, neutron shielding material is polyethylene, which having a thickness of 38 cm, and γ protective layer material is iron, which having a thickness of 11 cm. Conclusion: Simulation results show that the proposed shielding performance testing device can meet the requirements of neutron moderator, neutron protection and photon protection. Abstract关键词：252Cf neutron source;Shielding performance testing device;MCNP;Moderator material
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发布时间：2021-03-03 - 摘要：Background: Probabilistic safety analysis (PSA) methodology is widely used to assess the risk of nuclear power plant (NPP). Based on the results of level 1 PSA, the vulnerability of In-containment Refueling Water Storage Tank (IRWST) sub-system makes the initiating event Safety Injection Line Break (SI-LB) contributing significantly to core damage frequency (CDF). Purpose: This study aims to find the vulnerability of IRWST design by PSA assessment, and provide design improvement suggestion to reduce the risk of NPP. Methods: PSA methodology is used to evaluate the design improvement of IRWST, which is implemented by adding a third strainer (strainer C), and the three strainers are connected to each other. Fault trees of IRWST are rebuilt, and related event trees and level 1 PSA model are recalculated. Results: Quantitative result shows that the contribution of SI-LB initiating event to CDF is reduced by 53.5% and the total CDF is reduced by 21.5%. Conclusion: Design improvement of IRWST sub-system greatly reduced the core damage risk. Abstract关键词：PSA;IRWST sub-system;CDF
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发布时间：2021-03-03
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