最新刊期
卷 41 ， 期 5 ， 2018
- 摘要：BackgroundThe 252Cf brachytherapy is mainly used for cervical cancer endovascular radiotherapy. PurposeRadiation therapy will inevitably cause radiation damage to nearby organs. Therefore, it is necessary to evaluate the radiation damage of cervical cancer patients during radiotherapy. MethodsThis article is based on the radiation therapy of 252Cf cervical cancer in a hospital, and theoretical calculations and practical tests of dose field distribution in air and water by 252Cf, and compared with the tolerance limits of uterus, rectum, bladder, ovary and other organs. ResultsBy comparison, it is concluded that in the process of cervical cancer treatment, organs such as the rectum, bladder and ovary are also affected by large radiation in addition to damage caused by high doses of irradiation. ConclusionIn order to reduce the radiation damage of cervical cancer patients, the optimal irradiation time under different source activity was calculated.关键词：252Cf;Cervical cancer;Radiation dose field;Organ radiation assessment
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发布时间：2021-05-19 - 摘要：BackgroundThe rapid measurement of the location of beam spot and its characteristics is a key issue in the commissioning and quality control of proton pencil beam scanning system. PurposeThis article introduces the IBA commercial Lynx-2D in the spot scanning system of the first domestic proton therapy facility. In the spot scanning system commissioning, Lynx-2D is mainly used to measure the beam spot. MethodsThe analysis tools based on MATLAB is developed because the beam position can not be obtained by Lynx-2D software through the measurement data, the beam spot location is identified in the image with the Grayscale gravity center method and the Gaussian fitting method. ResultsThe two methods are satisfied with the measurement. ConclusionThe measurement efficiency can be improved with these two methods to find the beam position, and it is convenient to handle the data with the software developed by ourselves.关键词：Proton therapy;Pencil beam scanning;Lynx-2D;Measuring analysis
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发布时间：2021-05-19
LOW ENERGY ACCELERATOR, RAY AND APPLICATIONS
- 摘要：BackgroundThe baseline drift of detector output could result in spectrum drift and energy resolution loss of the multi-channel spectrometer. Though baseline estimation approaches can obtain the baseline of nuclear signals, they are not able to reduce the effect of baseline drift on the front-end circuit. PurposeThis study aims to design and implement a multi-channel spectrometer with auto-baseline restoration functionality. MethodsFirst of all, the baseline of detector's output is estimated by using minimum average method and implemented in the field-programmable gate array (FPGA). Then the estimation value is sent to micro-controller unit (MCU) for regulation condition judgment, and to digital-to-analog converter (DAC) for necessary baseline adjustment. Finally, the baseline of detector output is restored in the front-end circuit. A multi-channel spectrometer is designed based on LaBr3(Ce) detector and this auto-baseline restoration functionality. ResultsThe experimental results imply that the designed multi-channel spectrometer can realize baseline restoration automatically. ConclusionUnder the situation of high radioactivity, the baseline drift of detector output can be solved by this multi-channel spectrometer, and the energy resolution of the system can remain stable.关键词：Baseline restoration;Multi-channel spectrometer;Spectrum drift;Energy resolution
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发布时间：2021-05-19 - 摘要：BackgroundIn the gamma energy spectrum measurement system, estimation and deduction of the baseline has been an important part of pulse amplitude measurement processing. With the digitalization of gamma energy spectrometer, the baseline estimation and deduction method also need to make corresponding improvement. PurposeSome relatively complex algorithms which with digital sampling of original pulses only can be realized on a computer, but not suitable for the digital systems which based on field programmable gate array (FPGA). Some algorithms which could be executed on FPGA didn't fully consider the influence of the normal pulse signal, which have poor real-time performance and accuracy. To solve this problem, paper puts forward a kind of new algorithm which could estimate and deduct the pulse baseline. The most important is that it can implement on FPGA. MethodsThis method is called moving average filter after excluding abnormal signal (MAEA). That is based on the original pulse signal, which obtained by analog-to-digital (A/D) sampling, pulses are viewed as abnormal signals, superimposed on the direct-current (DC) baseline, which need to be deducted. Then DC baseline is obtained by the moving average filtering method. While the pulse DC baseline is deducted by FPGA, the complexity of the instrument for subsequent processing will be lower. ResultsAfter experimental verification, this method has some characteristics:simple algorithm, well accuracy and high sensitivity. It not only could inhibit the signal's influence on the baseline such as low frequency interference and temperature drift, but also could track the change of the baseline real time and accurately and suppress spectral drift to a certain extent. ConclusionThis method not only can be used for digital gamma energy spectrum measurement system, also can be used applied to other types, such as X-ray digital spectrometer.关键词：Pulse baseline estimate and deduct;FPGA;Moving average filter
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发布时间：2021-05-19 - 摘要：BackgroundTraditional nuclear electronics readout system, like "FPGA+ARM" combination, can not meet requirements of physical experiments in light if the physical size and power consumption. ZYNQ is a new all programmable SoC (System On Chip) architecture of field-programmable gate array (FPGA) with dual-core high performance ARM Cortex-A9 processors from Xilinx. PurposeThis study aims to develop a ZYNQ based readout module called ZYNQBee, which has lower profile, lower power and higher bandwidth performance between ARM and FPGA. MethodsThe ZYNQ XC7Z010 is employed as the kernel chip to build the ZYNQBee system by overcoming difficulties of hardware and software design including DDR3 (Double Data Rate 3) SDRAM (Synchronous Dynamic Random Access Memory) layout, interface of Gigabit Ethernet, transplant of Embedded Linux and so on. ResultsZYNQBee has been used as nuclear electronics readout module of the high pure Germanium (HPGe) detector system in CDEX (China Dark matter EXperiment), and it is tested to have more than 700 Mb·s-1 Ethernet throughput on average. ConclusionZYNQBee performs better than traditional designs, provides more powerful design flexibilities and functionalities.关键词：ZYNQ XC7Z010;Gigabit ethernet;Embedded LINUX;ZYNQBee;CDEX
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发布时间：2021-05-19
NUCLEAR ELECTRONICS AND INSTRUMENTATION
- 摘要：BackgroundMore than 80% of the protein in the protein database is solved by X-ray diffraction. The most commonly used wavelength is 0.0972 nm. Studies have shown that short-wavelength X-rays can reduce the radiation damage of crystals and improve the quality of X-ray diffraction data. PurposeIn order to collect X-ray diffraction data from protein crystals with shorter wavelength at beamline BL17U in Shanghai Synchrotron Radiation Facility (SSRF), our first priority is to extend its energy range to 25 keV using compound refractive lens (CRL). MethodsThe flux rate and flux density of the CRL focused photon with different curvature radius of a single structure are calculated by introducing the acceptance rate R. The close contact type CRL and the interphase type CRL are also calculated. ResultsFocusing on the factors such as the focusing effect and the layout of the experimental station, we propose the best solution for focusing short-wavelength X-rays in BL17U. Using 31 lenses with a radius of 50 μm can obtain 3.2018×1014 s-1·mm-2 at 25 keV theoretically. ConclusionThrough these theoretical calculation, we can prepare for collect protein crystal data using short X-ray wavelengths in BL17U.关键词：Compound refractive lens;Synchrotron radiation;Photon flux density;Shorter wavelength X-ray
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发布时间：2021-05-19 - 摘要：BackgroundUltrafine particles (UFPs) may provide various micro-locations of heterogeneous chemical reactions of trace of gaseous substances in atmospheric environment. Iron-containing UFPs are the main components of atmospheric aerosol. PurposeThis study aims to investigate heterogeneous reactions of SO2 on Fe3O4 UFPs. MethodsS K-edge of products was investigated by synchrotron radiation X-ray absorption near edge structure (XANES). ResultsThe results indicated that SO2 could be rapidly oxidized to form sulfate on the surface of Fe3O4. Formation of sulfate can be promoted under the UV and O3 conditions. ConclusionThe formation of adsorbed sulfate likely involves the formation of pre-absorbed sulfite (SO32-) and subsequent oxidation.关键词：SO2;Ultrafine Fe3O4 particle;Heterogeneous reaction;XANES
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发布时间：2021-05-19 - 摘要：BackgroundThe quality of the organolead halide layers in perovskite solar cells (PSCs) largely determines the performances of their device such as power conversion efficiency (PCE). Among a variety of preparation methods developed, one step solution spin coating is currently the most popular but a simple and effective preparation technique to fabricate high quality perovskite thin films. PurposeThe quality of the perovskite films depends strongly on the detailed preparation procedures. This paper aims to study the influence of solvent engineering during the preparation of the perovskite thin films especially on their crystallinity and thermal degradation. MethodsThere were four different perovskite films prepared in this study:one without any solvent engineering, one with dimethyl sulphoxide (DMSO) added in the precursor solution, one with antisolvent treatment by using ether, and one with both DMSO added and antisolvent treatment. The morphology and crystallinity of the thin films were studied by scanning electron microscopy (SEM) and synchrotron-based grazing incidence X-ray diffraction (GIXRD), respectively. The PSC performances were characterized by current density-voltage test. Moreover, the evolutions of crystallinity of the fabricated perovskite films during an in-situ heating experiment were monitored by GIXRD in air to study their crystallization and degradation. ResultsDMSO has little effects on the surface morphology and device performance, but postpones the perovskite crystallization process. The antisolvent promotes forming uniform dense films leading to high performance PSC and improves thermal structural stability. ConclusionIn one step spin coating, high quality thin films can be obtained quickly and effectively by an antisolvent treatment.关键词：Perovskite solar cells;Solvent engineering;Synchrotron-based GIXRD;In-situ
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发布时间：2021-05-19
SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS
- 摘要：BackgroundKinetics parameters play an important role on reactor safety analysis and dynamic behavior. Thorium-based molten salt experiment reactor with solid fuel (TMSR-SF1) is a new kind of reactor. Using Monte Carlo code to calculate kinetics parameters is in favor of its nuclear safety license. PurposeThis study aims at realizing the direct statistical calculation of kinetics parameters in Monte Carlo code, and applying this method to obtain the effective delayed neutron fraction and effective neutron generation time of TMSR-SF1. MethodsWe implant the direct statistical method into MCNP (Monte Carlo N Particle Transport Code) code by tallying the fission neutron type and fly time, and verify its accuracy with multiple ICSBEP (International Criticality Safety Benchmark Evaluation Project) benchmark. ResultsThe benchmark kinetics parameters calculated by direct statistical method are consistent with experiment measured value (±5% deviation). The effective delayed neutron fraction and effective neutron generation time of TMSR-SF1 we obtained, are close to that of conjugate flux method based on MCNP code. ConclusionIt is reliable to use direct statistical method to calculate kinetics parameters of TMSR-SF1.关键词：Monte Carlo;Kinetics parameter;Effective delayed neutron fraction;Effective neutron generation time;TMSR-SF1
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发布时间：2021-05-19 - 摘要：BackgroundThe molten-salt-air heat exchanger is an important part of thorium molten salt reactor (TMSR) integrated simulation platform based on strategic priority research program of Chinese Academy of Sciences, and the flow-induced vibration problem of heat transfer tube in this heat exchanger is critical. Furthermore, the analysis of fluid-structure interaction is currently few and unreliable. PurposeThis study aims at the flow-induced vibration response characteristics of U-type heat pipe in shell and tube heat exchangers. MethodsNumerical simulation was operated based on two-way fluid-structure interaction, and the calculated results are compared with experimental data to judge the feasibility of this method. Results and ConclusionThe relationship between acceleration values are consistent, the error between experimental data and calculated results is in the range of about -12% to 15%, shows that flow-induced vibration analysis of single-tube based on two-way fluid-structure interaction method is feasible. Numerical simulation has also indicated that in the initial period of 0.06 s air flow and displacement of heat transfer tube tend to be stable, the U-type tube has periodic variation characteristics of expand-rebound. Finally, the reciprocating motion of tube tends to be a shape of number "8".关键词：Shell-and-tube heat exchanger;U-type tube;Flow-induced vibration;Two-way fluid-structure interaction
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发布时间：2021-05-19 -
The temperature distribution of molten salt reactor under the outer salt layer blocked situation 封面论文
摘要：BackgroundFor the graphite-moderated channel type molten salt reactor, the outer salt layer is typically adopted to cool the graphite moderator and the reactor vessel. Since the outer salt layer is adjacent to the alloy, the safety of the structure material is directly influenced by the cooling effect of the outer salt layer. PurposeThis study aims at researching the influence of the outer salt layer under blocked situation on the temperature distribution of reflector and alloy for a conceptual designed 2 MW experimental molten salt reactor. MethodsFirst of all, a three-dimensional thermal-hydraulic model is built to analyze the temperature distribution of the solid region using the three-dimensional heat conduction model. The solid region includes the graphite moderator, fuel assemblies and reactor vessel. Then the fuel salt in the channel is simulated with the one-dimensional single-phase flow model. The outer salt layer is simulated with either one-dimensional single-phase flow model or three-dimensional laminar flow model, which depends on the blocked situation. Finally, the temperature field and mass flow distribution of the 2MW experimental molten salt reactor is calculated with the thermal-hydraulic model, when the total mass flow in the outer salt layer reduces and the outer salt layer contains local blocked region. ResultsThe simulation results show that the cooling effect of the outer salt layer is seriously influenced by the total mass flow in the outer salt layer. The results also reveal that the local blocking, a solid region with a diameter of 4 cm (close to the radius of down salt channel) exists in the outer salt layer, in the outer salt layer does not change the temperature field of the reactor obviously. ConclusionBase on the results, when the total mass flow in the outer salt layer is reduced to 0.365% of the rated mass flow, the maximum temperature of reactor vessel is close to 730 degree celsius, which is near the safety limit of alloy. And if the local blocking situation happens, the maximum temperature of the blocked region reaches 621.74 degree celsius, which is below the safety limit of alloy.关键词：Molten salt reactor;Thermal-hydraulics;Outer salt layer;Blockage- 332
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发布时间：2021-05-19 - 摘要：BackgroundThe cover gas purge system failure incident is one of the typical incidents of 2 MW liquid-fueled thorium molten salt experimental reactor-liquid fueled (TMSR-LF1), which could result in radiation releasing. PurposeThis paper attempts to analyze the habitability for operations in the powerhouse under the cover gas removal system failure incidental condition, and provide data for nuclear emergency for TMSR-LF1. MethodsBased on source items and emission pattern, we did conservative evaluations of atmospheric dispersion factors of powerhouse boundaries by using ARCON96 and 24 h individual effective dose for occupational workers locate at powerhouse boundaries. ResultsFor this incident, the highest 24 h individual cumulative dose is 3.04 mSv and it appears on the powerhouse boundary nearest to the reactor core. ConclusionCompared the results with the national standards, it is not up to site-area emergency action level so that the reactor would enter in alert emergency classification.关键词：TMSR-LF1;The cover gas purge system failure;Effective dose;Emergency action level
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发布时间：2021-05-19
NUCLEAR ENERGY SCIENCE AND ENGINEERING
- 摘要：BackgroundSegmented gamma scanning (SGS) and tomographic gamma scanning (TGS) are the normal standard non-destructive assay (NDA) techniques for low intermediate waste drum detection. PurposeThis study aims to evaluate the performance of semi-tomographic gamma scanning (STGS) for waste drum of nuclear power plant (NPP). MethodsThe principles of SGS and TGS are synthesized in the STGS method and the implementation of its algorithm, each segment of the waste drum is divided into annual voxels and tomography is used in the radiation reconstruction. The accuracy of STGS is verified by MCNP calculation for the 400L standard waste drums which contains three types of nuclides. The cases of point source and uniform materials are employed for comparison. ResultsThe experimental results show that the reconstruction error and statistical bias for STGS can be controlled lower than 50% and is always half or less of SGS while maximum error of SGS is over 100%. The detection time of STGS is obviously shorter than TGS. ConclusionSTGS can keep the balance between accuracy and detection time, it is an effective method for non-destructive assay of 400L radioactive waste drums with high density.关键词：STGS;NDA;Radioactive waste
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发布时间：2021-05-19 - 摘要：BackgroundNowadays, there are big amount of irradiated nuclear graphite waiting to be decomissioned worldwide. Due to their high content in nuclear graphite, tritium and 14C are the two main radionuclides that should be specially treated before final disposal. The optimal desorption temperature for 14C was reported to be 700℃. PurposeAs tritium is the isotope of hydrogen with similar physical and chemical properties, in order to investigate the desorption process for tritium in nuclear graphite, this study investigates the absorption of hydrogen at 350℃ and desorption of hydrogen from 400℃ to 700℃ in three types of nuclear graphite. MethodsSamples of three types of nuclear graphite were subjected to flowing hydrogen at 350℃ for hydrogen absorption, then the absorbed hydrogen was desorbed by thermal treatment from 400℃ to 700℃. The hydrogen concentration of the outlet gas was measured by gas chromotagraph. ResultsAccording to our experiments, three types of nuclear graphite have different amount of absorption, but the following desorption experiments showed similar trend with some differences on the amount of desorption varied with time. The amount of absorption of the domestic nuclear graphite NG-CT-10, Japanese nuclear graphite IG-110 and Germen nuclear graphite NBG-18 were measured to be 6.7×10-3 mL·g-1, 9.3×10-3 mL·g-1 and 9.12×10-3 mL·g-1, respectively, and the amount of hydrogen that is chemically absorbed in graphite were 3.2×10-3 mL·g-1, 3.0×10-3 mL·g-1 and 0.92×10-3 mL·g-1 respectively. The difference in the amount of absorption could be due to the difference in the physical properties and synthetic process. Moreover, the absorbed hydrogen start to desorb effectively after the temperature was raised to 700℃. For the three types of nuclear graphite investigated in our research, the amount of desorption at 700℃ was different:7% of hydrogen was desorbed in NG-CT-10 graphite, 13.5% for IG-110 and 70% for NBG-18 nuclear graphite. ConclusionBased on our findings, the amount of stability absorbed hydrogen in domestic nuclear graphite NG-CT-10 was the highest, hence amount of tritium absorbed could also be the highest in NG-CT-10 nuclear graphite. According to the model of hydrogen absorption in nuclear graphite proposed by Atsumi, the hydrogen desorbed at 700℃ were the hydrogen absorbed at the edge surface of graphite crystallites. To fully desorb tritium and 14C effectively at 700℃, the carrier gas during desorption should be varied.关键词：Decontamination of nuclear graphite;Absorption;Desorption;Hydrogen;Tritium
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发布时间：2021-05-19
NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH
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