最新刊期
卷 0 ， 期 0 ， 2020
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Shielding design of free electron laser’s main wall based on the line-source sampling physical model 封面论文
摘要：Background: Dalian Coherent Light Source (DCLS) which is under construction is the first fourth-generation light source in China, and the only free electron laser with adjustable ultraviolet waves in the world. Purpose and Methods: By adopting the FLUKA code, a cylinder-tunnel geometric model and a line-source sampling physical model are constructed to calculate the thickness of shielding walls in the section of injector. The difference is discussed by comprehensive comparison of calculation results based on FLUKA and SHIELD11. Results: The results based on the FLUKA coincide with that based on SHILED11. The dose out of shielding walls is mainly comprised by the dose of neutron, and the dose of Giant-Resonance accounts for more than 95% of neutron dose. Conclusion: Line-source sampling physical model constructed based on Monte Carlo method can be used in shielding design of electron accelerator’s main walls.Cited- 18
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发布时间：2021-03-03 - 摘要：Background: Incineration is an attractive method of energy production and waste reduction for the treatment of municipal solid waste (MSW). However, the secondary pollutants followed such as fly ash (FA), bottom ash (BA) from the waste incineration are always a concern. Yet few articles provide detailed information about the physical and chemical characteristics of trace elements in ash at the molecular level. Purpose: The elemental concentrations and microstructure characteristics of ash were investigated to understand the distribution and migration of the elements in MSW incineration process. Methods: The study of the characteristics of FA and BA from Shanghai MSW incineration plant was based on the concentrations of elements, water-soluble salts, microstructure, section-distribution of the elements in single particle, isotope ratio and chemical species of Pb, which were studied respectively by using synchrotron radiation X-ray fluorescence (SR-XRF), Ion Chromatography (IC), Scanning electron microscopy (SEM), X-ray energy dispersive microanalysis (EDX), Synchrotron radiation micro-beam X-ray fluorescence (μ-XRF), Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and X-ray absorption near-edge structure (XANES) spectra. Results: Mass concentrations of most metal elements in FA were higher than those in BA, especially Pb and Cd, which had been obviously enriched. FA particles were of relatively smaller size and rougher surface than those of BA, which brought easier adsorption of heavy metals in FA. The large enrichment factors of Pb, Cd, Cu and Zn indicated these elements were in extreme pollution state. Water-soluble salts in FA and BA mainly existed as chloride and sulfate of Ca, Na and K. The ion concentrations in FA were generally higher than those in BA. Results of μ-XRF suggested that Pb, Zn, Cu, Cr, Fe and Mn had nonuniform distributions and highly localized to some small regions in FA and BA. Isotope ratio of Pb in FA and BA was similar. Chemical species of Pb were also similar and existed mainly as PbCl2, PbS and PbO. Conclusion: The distribution and migration of the elements in MSW incineration process were related to elements characteristics and incineration environment. As hazardous wastes, FA from MSW must conduct a stabilizing treatment before landfill and BA should require pretreatments before utilization. Abstract
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发布时间：2021-03-03 - 摘要：Background: The compensated neutron logging technology is widely used in oil exploration and development. The neutron detector commonly used in this technology is the helium-3 proportional counter. Due to the decreasing in supply of the helium-3 gas, the price of the helium-3 proportional counter rises quickly. Purpose: The aim is to develop a new type of neutron detector to replace the helium-3 tubes in the compensated neutron logging technology. Methods: A new thermal neutron detector coated with a layer of thermal neutron convertor in the inner glass of the Multi-gap Resistive Plate Chamber (MRPC) was developed. Under the conventional and underbalanced conditions, Monte Carlo method was used to simulate the response of the boron-coated MRPC thermal neutron detector and helium-3 proportional counter employed in compensated neutron logging technology. Results: It is shown that the SS/LS increases with the rise of porosity using either the boron-coated MRPC thermal neutron detector or the helium-3 proportional counter, and the results of these two detectors are basically identical. Conclusion: It indicates that the boron-coated MRPC thermal neutron detector can be used for compensated neutron logging. Abstract
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发布时间：2021-03-03 - 摘要：Background: In the adoption of Prompt Gamma-ray Neutron Activation Analysis (PGNAA) technique, the composition of samples is always assumed to be uniform, while it is nonuniform in fact, which would affect the analysis result. Purpose: The influence of the sample’s uniformity to PGNAA has been discussed. Methods: Samples of the same composition and average density, but different uniformity have been simulated with Monte Carlo method. And the preliminary analysis has been discussed in the aspects of self-absorption and the neutron field distribution of the samples. Results: The results show that the change of sample uniformity has a certain effect on the gamma-rays spectrum. The difference of the element characteristic peak counting rate, which is caused by the change of samples’ uniformity, is even higher than 20% for some elements. Conclusion: In the PGNAA technique, the uniformity of samples has to be considered to ensure the element analysis accuracy. Abstract
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发布时间：2021-03-03 - 摘要：Background: The investigation of the material damage state is very important for industrial application. Most mechanical damage starts with a change in the microstructure of the material. Positron annihilation techniques are very sensitive probes for detecting defects and damage on an atomic scale in materials, which are of great concern in the engineering applications. Additionally they are apparatus of non-destruction, high-sensitivity and easy-use. Purpose: Our goal is to develop a system to exploit new non-destructive testing (NDT) methods using positron annihilation spectroscopy, a powerful tool to detect vacancy-type defects and their chemical environment. Methods: A positron NDT system was designed and constructed by modifying the "sandwich structure" of sample-source-sample in conventional Doppler broadening and positron lifetime spectrometers. Doppler broadening and positron lifetime spectra of a single sample can be measured and analyzed by subtracting the contribution of a reference sample. Results: The feasibility and reliability of positron NDT system have been tested by analyzing nondestructively deformation and damage caused by mechanical treatment or by irradiation of metal alloys. This system can be used for detecting defects and damage in thick or large-size samples, as well as for measuring the two-dimension distribution of defects in portable, sensitive, fast way. Conclusion: Positron NDT measurement shows changes in real atomic-scale defects prior to changes in the mechanical properties, which are detectable by other methods of NDT, such as ultrasonic testing and eddy current testing. This system can be developed for use in both the laboratory and field in the future. Abstract
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发布时间：2021-03-03 - 摘要：Background: Although the measurement of neutron dose equivalent was initiated several decades ago, the accuracy of the measurement is not high enough due to the dosimeter’s sensitivity and fluence response. Purpose: The aim of this work is to accurately scale the performance parameters and insure the design accuracy of neutron dose equivalent instrument. Methods: MCNP5 was used for simulation analysis of the impact of air, walls, and paraffin in the laboratory respectively on the barrels of neutron counting before experiment. Results: The experimental results show that under ideal conditions, the neutron counting rate decreased with the increase of distance between the source and probe. The air impact on neutron count was up at first and then became weakened, but tended to be strengthened again finally. The neutron scattering rate was less than 10%. And the shorter the distance was, the weaker became air scattering neutrons impact on probe counting. When the probe and the source distance reached 260 cm, the influence of the paraffin barrels was the weakest, which was 1%. The influence of the wall on the neutron count increased with the source-probe distance. When the probe and the source distance was 360 cm, the neutron scattering from the wall was 2 times of that from the source. When the source and the probe distance was 175 cm, all of influences to the neutron scattering reached the minimum, and the measurement data tended to be the most accurate. Conclusion: Through the comparison between experimental and theoretical data, the error of the count rate is less than 30% when the source and the probe distance is between 125–300 cm, confirming with the requirements of the neutron dose measurement technology, which verifies the accuracy of the neutron dose equivalent instrument design. Abstract关键词：Performance parameter;MCNP5;Scattering neutrons;Dose equivalent
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发布时间：2021-03-03 - 摘要：Background: In order to accurately measure the neutron spectrum using time-of-flight method, a nanosecond pulse neutron generator is introduced from Efremov Institute of Electric Physics, Russia. Purpose: The nanosecond pulse ion beam current is generated by a bunching system. Some key equipments (nanosecond pulse signal source, high frequency bunching power supply, adjustment system of the negative feedback, etc.) are developed by ourselves for the localization of the components. Methods: The problem of high bunching power supply voltage is solved with bidirectional scanning technology. The negative feedback technology makes the nanosecond pulse bunching system of long-term stability. In order to measure the nanosecond pulse beam, a fast pulse Faraday cup measurement device is developed. Results: The Full Width at Half Maximum (FWHM) of the neutron generator ion beam pulse is 1.5 ns, and the pulse repetition frequency-range is 1 kHz?4 MHz, beam spot diameter is about 10 mm. Conclusion: Because the Electron Cyclotron Resonance (ECR) ion source is used in neutron generator, it has a number of advantages, such as small emittance, small energy divergency, no filament and long-time continuous working stability, which is a good experimental device for neutron physical research. Abstract关键词：Bunching system;Ion beam;Nanosecond pulse;Neutron generator
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发布时间：2021-03-03 - 摘要：Background: This research is to take energy spectrum of α particle into consideration in the measurement of radon. Purpose: We aim to find the influence factors of screening particle energy during the process of detector design. Methods: Based on the electrostatic collection radon measurement method, in order to study the influence factors of the measurement such as aluminum foil and air layer, the reasonable radiation source and geometric model are abstracted and calculated with Geant4 software. Results: The best ranges of aluminum foil thickness and air layer thickness are obtained by analyzing their relationship with α energy, the Full Width at Half Maximum (FWHM), the energy resolution, the distance of peaks and the peaks screening power. Conclusion: With the results adopted above, the energy spectrum device is fabricated. Based on the α energy spectrum sampled in a radon chamber, the validity of this design has been proved. It provides a set of reliable data for the design of radon measuring device with electrostatic collection method.Cited
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发布时间：2021-03-03 - 摘要：Background: Poly (vinyl formal) (PVF) filter material has broad application in the field of precision filtration due to its unique properties, such as fine pore, high filtration precision, large flux and no fiber loss. Purpose: The goal of this work is to prepare modified PVF filter material by γ-radiation technology. Methods: Modified polyvinyl formal filter materials were prepared by γ-radiation technology with polyvinyl alcohol (PVA-1799) and formaldehyde as raw materials, and pentaerythritol triacrylate (PETA) as modifier. The compared properties of cell structure, mechanical properties, dimensional stability, water absorption, water resistance and oil resistance were tested and characterized. Results: The results showed that the material pore size was less than 300 μm, the tensile strength reached 3.01 MPa, and the tear strength was 13.23 MPa, which had good stability and better mechanical properties as well as oil resistance and water resistance abilities. Conclusion: γ-radiation technology can simplify the production process of PVF filter materials, reduce inorganic acid and formaldehyde dosage, and thus is beneficial for environment protection. Abstract
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发布时间：2021-03-03 - 摘要：Background: Normal green channel vehicle inspection methods have many flaws, such as low efficiency and long time expense. The accuracy depends on the experience of inspector and it can not meet the online inspection. Purpose: The aim is to develop a new method which can help the inspector to promote the vehicle inspection speed and accuracy. Methods: Using real time image processing and control system, a new imaging system was developed. Results: The actual test shows that the inspection time can be reduced to less than one minute and the inspectors can also be reduced to one or two persons. Also the inspection accuracy is greatly improved. Conclusion: The imaging system achieves good effect through actual tests. Abstract关键词：Low radiation;Vehicle inspection;Radiation imaging;Image processing;Green channel
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发布时间：2021-03-03 - 摘要：Background: A data acquisition system for online pulsed gamma dose measurement device is designed and developed, and its performance is tested. Purpose: The data acquisition system output electric charges and input energies have a good linear relationship in both the continued and pulsed input. Methods: Experiments have been done respectively on the TDL and “Chen Guang” accelerator. Results: The results show that the relative deviations are less than 5%. Conclusion: This data acquisition system is a new approach for online measurement of single pulsed gamma radiation dose. Abstract关键词：Single pulsed gamma radiation;Data acquisition system;Output electric charge;Si-PIN detector
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发布时间：2021-03-03 - 摘要：Background: The damage equivalence coefficient is the key factor to appraise the difference of radiation damage between different neutron spectra. Purpose: This research is to obtain the equivalence coefficient of radiation damage between two different neutron spectra. Methods: The silicon bipolar transistors (3DG121C) with good similarity of parameters have been employed as the displacement damage monitors based on the liner relationship between the reciprocal of direct current gain and the neutron flux. Results: The radiation damages of two sets of selected 3DG121C transists placed at the two special sites on CFBR-II have been obtained by the in-situ on-line measuring of the change of gain with the accumulation of neutron flux, and the equivalence coefficient were deduced. Conclusion: The results show that the damage constants at different sites on CFBR-II are of great similarity. Abstract关键词：Radiant effect;Damage constant;Equivalence coefficient;Silicon bipolar transistors;Fast neutral critical assembly
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发布时间：2021-03-03 - 摘要：Background: Filter membrane is an important part of the balloon emanometer. The membrane of high filtration efficiency but little self-absorption can not only improve the sampling rate, but also reduce the measurement error effectively. Purpose: The experiment aims to compare the performance of three different filter membrane materials. Methods: Based on the radon and its progeny collecting physical processes on the membrane, we deduced the collection of radon in filters and its decay variation with time. Through the experiment, the filtration efficiency and self-absorption factor of the three different membranes have been tested. Results: When the thickness is almost the same, the filtration efficiency of Polytetrafluoroethylene (PTFE) filter and nylon filter is higher than that of commonly used glass fiber filter and its self-absorption is better than that of glass fiber membrane. The air resistance of PTFE filter is the best. It can effectively improve the performance by increasing thickness of the glass fiber filter membrane. Conclusion: This is not only a good reference for the selection of filter membrane in radon measurement with balloon method, but also applicable to radon-measuring devices with other methods. Abstract关键词：Self-absorption;Filtration efficiency;Balloon radon method;Filter membrane
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发布时间：2021-03-03 - 摘要：Background: It’s difficult to evaluate the radon prevention effect because of the short operating time of measuring instrument under the circumstances of high humidity in underground construction. Purpose: A new rapid method to evaluate the radon prevention efficiency of underground construction was introduced. Methods: The radon concentrations before and after shielding operation were determined, and according to the regularity of radon decay, the shielding rate can be calculated. Results: The results showed that radon shielding rate in underground construction remains generally stable with variation of time, and the actual relatively standard deviation was 3.95%. So the rapid determination and evaluation of radon preventing effect under special conditions in underground construction can be realized by taking shielding rate in a short time for the final shielding rate. Compared with those by the local static method in ground lab, the results were similar. Conclusion: This paper provided a prompt, accurate and practicable way for the evaluation of radon prevention in underground construction, having a certain reference value. Abstract关键词：Underground construction;Radon preventing effect;Evaluation method
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发布时间：2021-03-03 - 摘要：Background: Working under extreme conditions, nuclear fuel rods, the key component of nuclear plants and reactors, are easy to be broken. In order to be safe in operation, lots of testing methods on the fuel rods have to be carried out from fabrication to operation. Purpose: Neutron radiography is a unique non-destructive testing technique which can be used to test samples with radioactivity. As the essential equipment, the nuclear fuel rod transport container has to shield the radioactivity of fuel rod and control its movement during testing and transporting. Methods: The shielding simulation of the transport container was performed using the MCNP4C code, which is a general purpose Monte Carlo code for calculating the time dependent multi-group energy transport equation for neutrons, photons and electrons in three dimensional geometries. Results: The material and dimension of the transport container used for neutron radiography testing fuel rods at Chinese Advanced Research Reactor (CARR) were optimally designed by MCNP, and the mechanical devices used to control fuel rods’ movement were also described. Conclusion: The 2-m long fuel rod can be tested at CARR’s neutron radiography facility (under construction) with this transport container. Abstract关键词：Non-destructive testing;Neutron radiography;Nuclear fuel rod;Transport container
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发布时间：2021-03-03 - 摘要：Background: Recently, the molten salt reactor (MSR), a generation IV fission reactor candidate, has drawn much attention because of its intrinsic safety. However, the harsh service environment of the MSR, especially the corrosion environment, raises many challenges in terms of applying structural materials, such as intergranular cracking and embrittlement. MAX phases materials are promising structural materials that can be used in MSRs. However, the corrosion behaviour of these materials in molten LiF-NaF-KF (FLiNaK) is yet to be evaluated. Purpose: The present work is a preliminary investigation of the corrosion behaviour of MAX phase materials in molten fluoride salts and aims to understand the corrosion mechanism of MAX phases to enable their application in next generation MSR. Methods: We choose two common MAX phases: Ti3SiC2 and Ti3AlC2 as experiment subject. The corrosion tests were performed at 850 oC for 144 h in airtight graphite crucibles under an argon cover gas. Results & Conclusion: The corrosion of these two MAX phases in molten FLiNaK salt mainly showed as the corrosion of element A and then left us mostly cubic TiCx. The difference was that Ti3AlC2 lost Al entirely, however, the loss of Si in Ti3SiC2 occurred only 150 μm depth below the surface. The weight loss data showed that Ti3SiC2 had a much better corrosion resistance than Ti3AlC2. Abstract关键词：MAX phases;Molten salts;Corrosion
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发布时间：2021-03-03 - 摘要：Background: Many new concepts of nuclear energy systems with complicated geometric structures and diverse energy spectra have been put forward to meet the future demand of nuclear energy market. The traditional deterministic neutronics analysis method has been challenged in two aspects: one is the ability of generic geometry processing; the other is the multi-spectrum applicability of the multi-group cross section libraries. The Monte Carlo (MC) method predominates the suitability of geometry and spectrum, but faces the problems of long computation time and slow convergence. Purpose: This work aims to find a novel scheme to take the advantages of both methods drawn from the deterministic core analysis method and MC method. Methods: A new two-step core analysis scheme is proposed to combine the geometry modeling capability and continuous energy cross section libraries of MC method, as well as the higher computational efficiency of deterministic method. First of all, the MC simulations are performed for assembly, and the assembly homogenized multi-group cross sections are tallied at the same time. Then, the core diffusion calculations can be done with these multi-group cross sections. Results: The new scheme can achieve high efficiency while maintain acceptable precision. Conclusion: The new scheme can be used as an effective tool for the design and analysis of innovative nuclear energy systems, which has been verified by numeric tests. Abstract关键词：Monte Carlo homogenization;Multi-group Monte Carlo transport;Diffusion calculation;Basis of verification
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发布时间：2021-03-03 - 摘要：Background: In order to explore the sequence of neutrino mass and carry out other advanced scientific researches, Jiangmen underground neutrino observatory is proposed and the project is in the process of site searching. Purpose: This paper mainly introduces the way of position measurement between Jiangmen experimental station and reactor cores of Yangjiang nuclear power plant and Taishan nuclear power plant. Methods: The control network is established and measured by GPS, LGO and the self-developed software is used for data processing and fitting translation. Results: Through the actual measurement, the accuracy of the final coordinate is ±70mm, which meets the tolerance requirement. Conclusion: According to the feedback from the designer, the scheme of the position measurement is reasonable and feasible. Abstract关键词：Jiangmen neutrino experiment;Nuclear reactor;GPS control net;Distance;Precision
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