最新刊期
卷 40 ， 期 5 ， 2017
- 摘要：BackgroundCompared with common 2D calorimeters, 3D imaging calorimeters have higher geometric acceptance and better background rejection performance for space particle physics experiments but they also have a large number of readout channels with more complicated electronics. The advantages of small size, low power consumption, low heat and high integration makes the image intensified charge-coupled device (ICCD) preferable to some traditional photoelectric devices like photomultiplier tube (PMT). PurposeThis study aims to investigate the feasibility of ICCD readout for a 3D imaging calorimeter. MethodsA 3D imaging calorimeter prototype with 250 channels and readout for an ICCD has been designed. Laser diodes were used as light sources to measure the linearity, light intensity resolution and crosstalk performance of the ICCD. The 10-GeV electron beam of the Super Proton Synchrotron at the European Organization for Nuclear Research (CERN-SPS) was employed to measure the response of the calorimeter and reconstruct the calorimetry. ResultsExperimental result of 10-GeV electron beam test shows the energy of incident particle can be reconstructed from ICCD image correctly. ConclusionThe performance of ICCD with appropriate readout electronics can meet the requirements for a 3D imaging calorimeter.关键词：Light facula;Linearity;Crosstalk;Beam test;Energy reconstruction
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发布时间：2021-05-19 - 摘要：BackgroundThe environments for monitoring artificial radioactive aerosol are often complex, as sometimes it could even be in underground caverns, tunnels or underground nuclear facilities, of which the concentration of both radon and its radioactive products would be up to 103-104 Bq·m-3. However, under high radon condition, the tailing phenomenon of radon and thorium peaks could interfere with radioactive counts and the artificial aerosol counts, thus affecting the detection limit of radioactive aerosol. PurposeThis study aims to design a special normal-pressured artificial aerosol monitoring equipment, which can operate well under the high radon environment. MethodsDual-channel synchro measurement was employed to combine high accuracy of the vacuum channel and the fast response of the normal pressure channel. ResultsImplemented aerosol monitoring system can respond rapidly to plutonium and uranium aerosol in atmospheric environment, and in the case of artificial radionuclide leakage, the fastest measurement results can be obtained in 30 min. In general, the theoretical detection limit can reach 10-4-10-3 Bq·m-3, and the verifiable detection limit of uranium and plutonium are 0.1 Bq·m-3 and 0.02 Bq·m-3, respectively. ConclusionThis design can be applied to a variety of high radon environments which require unmanned monitoring for artificial nuclear.关键词：High radon environment;Artificial radioactive aerosol;Theoretical detection limit;Vacuum aerosol measurement
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发布时间：2021-05-19
NUCLEAR ELECTRONICS AND INSTRUMENTATION
- 摘要：BackgroundThe jet device composed of jet pump and primary pump has the advantages of simple structure and high reliability, and it is suitable for the special environment, such as radioactive, flammable and explosive. It is helpful to improve the inherent safety of the reactor by introducing the jet device as primary pump for Marine Reactor X (MRX). The sudden increase of the coolant flow rate of the reactor leads to the change of the core temperature during start-up period, which affects the safety of the core operation. Purpose:This study aims to obtain the jet device transient feature during start-up period of primary pump in the MRX which introducing the jet device as primary pump. MethodsThe primary loop circuit system is modeled with a 3-dimensional (3D) Computational Fluid Dynamics (CFD) code FLUENT, and transient characteristics at 10% full power (FP), 17.5% FP and 25% FP core power conditions were analyzed during the stage of primary pump startup. ResultsThe analysis results show that the jet device can effectively improve the natural circulation ability of the primary loop circuit system, reform the initial flow rate and slow down the trend of coolant temperature change during start-up period of primary pump, so it can improve the safety of the transition. On the other hand, there are some unfavorable factors of reactor safety during start-up period of primary pump, such as the temperature of the primary circuit fluctuates (the greater the core power, the greater the fluctuation range) and the high flow rate of jet pump. ConclusionThe design of jet device is feasible to improve the safety of MRX, but the real use also needs some adjustment.关键词：Jet device;Start-up period of primary pump;CFD;3D flow field
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发布时间：2021-05-19 - 摘要：BackgroudThe reactor coolant system (RCS) pipelines creep is an important phenomenon during severe accident analysis of pressurized water reactor (PWR) plants. PurposeThis study aims to develop a severe accident analysis model focus on the RCS pipeline creep analysis for small PWR plant. MethodThe severe accident analysis model is developed by using the SCDAP/RELAP5 code, the creep prediction formulas of RCS main coolant pipeline (SA321) and natural circulation steam generator tubes (00Cr25Ni35AlTi) materials are fitted by the experiment data, and the corresponding functions are added to the creep prediction subroutines of the SCDAP/RELAP5 code, which are finally verified by a simulation of supposed severe accident by SCDAP/RELAP5 code. ResultsThe upgraded SCDAP/RELAP5 code is finally available for the RCS pipelines creep analysis of the small PWR under severe accident condition. ConclusionThis provides a basic reference for the next quantify creep character analysis of the small PWR during the severe accident processes.关键词：PWR;Severe accident;Creep prediction;SCDAP/RELAP5 code
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发布时间：2021-05-19 - 摘要：BackgroundNuclear graphite is a key material in Molten Salt Reactor (MSR). And fracture property is one of the most important parameters of the nuclear graphite. Purpose:This study aims at the failure stress of the graphite and to develop a numerical model to simulate the experiment. MethodsThe four-point bending test was employed to find the failure stress of the dog bone graphite. And a numerical model has been developed for simulation by using the extended finite element method (XFEM). ResultsThe failure stress of NG-CT-10 dog bone nuclear graphite has been investigated through the four-point bending test, and the experiment results are in accord with the numerical simulation results. ConclusionThe numerical model in XFEM can accurately simulate the fracture process of the nuclear graphite, and the fracture criterion can be determined accordingly for nuclear graphite.关键词：Nuclear graphite;Failure stress;XFEM;Numerical simulation
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发布时间：2021-05-19 - 摘要：BackgroundThe operational transient of a nuclear power plant mainly refers to transients or events that occur frequently or periodically during commissioning or power operation. The transient process involves the response of primary loop, secondary loop and the control system. Usually, particular software is used for transient analysis. Purpose:This study aims to develop the program for analysis of normal transient and overpressure (PANTO) software that fulfils the requirements of operational transient analysis. MethodsBased on the mature and reliable system analysis model and special component model, object-oriented C++ language and java language were applied to design the modular software with completely independent intellectual property rights for PANTO. Through the unit testing, integration testing and system testing, all detected code defects were eliminated. Validation calculations were carried out for the 10% load step increase and complete load ejection at full power transient test which performed in the Qinshan Phase Ⅱ nuclear power plant. ResultsThe results show that the PANTO can simulate the key parameters variation in the transients, and the calculation accuracy can meet the requirements of the engineering application. ConclusionThe PANTO is applicable for operational transient analysis of PWR nuclear power plant.关键词：Operational transient;Software development;PANTO
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发布时间：2021-05-19 - 摘要：BackgroundDissimilar metal welded joints (DMWJ) were indicated to be vulnerable components in the primary system, and an accurate structural integrity assessment for such DMWJ is needed. Three-material DMWJ structures without buttering layer are also applied in recent years. Purpose & MethodsIn order to understand the effects of crack locations and crack sizes on failure assessment diagrams (FAD), FADs of two types of dissimilar metal welded structures (four-material structure with buttering layer and three-material structure without buttering layer) for joining safe end to pipe-nozzle of nuclear pressure vessel were constructed by finite element numerical analysis. ResultsLimit loads of the two welded structures are basically the same, and the crack locations almost have no effects on the limit loads. With moving crack location from pipe nozzle to 316L safe end pipe and increasing crack depth, the failure assessment curves (FACs) shift downward and the safety margin of the cracked structure decreases. ConclusionsBecause the FADs and limit loads of the cracks with the same location and size in the two welded structures are basically the same, their properties against fracture failure and structural strength are almost the same. It is feasible to connect pipe-nozzle with safe end using simplified manufacture process without buttering layer for the consideration of cost saving.关键词：FAD;DMWJ;Nuclear pressure vessel;Safe end;Crack
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发布时间：2021-05-19 - 摘要：BackgroundThe maneuverability of nuclear-powered ships requires the sharp step change of the output power of the marine reactor, which causes fluctuation of fuel cladding temperature and coolant pressure. Since the enormous fluctuation leads to fatigue damage of cladding, it is important to analyze the fatigue lifetime of the fuel claddings in marine reactor. Purpose:The purpose is to analyze the effects of cladding temperature, coolant pressure, internal pressure of fuel rod and irradiation on the fatigue lifetime. MethodsBy using ANSYS, the thermalmechanical behaviors of fuel rods in transient operation condition were simulated. The fatigue lifetime of cladding under different conditions was investigated, based on the design curves of the fatigue lifetime for zircaloy cladding. ResultsThe results indicate that the fatigue lifetime of the fuel cladding in marine reactor will reduce much in transient operation condition and irradiation can reduce fatigue lifetime of fuel cladding. The change of cladding temperature has little effect on the fatigue lifetime of cladding, compared with the change of coolant pressure. ConclusionThe fatigue damage in the fuel cladding in marine reactor is very serious. Suitable measures are suggested to take in order to reduce the fatigue damage of the cladding, under the premise of ensuring the maneuverability of ships.关键词：Marine reactor;Fuel cladding;Fatigue lifetime
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发布时间：2021-05-19
NUCLEAR ENERGY SCIENCE AND ENGINEERING
- 摘要：BackgroundMuon tomography based on multiple Coulomb scattering (MCS) has been widely used in structural detection of nuclear objects. However, for some particular objects, the tomographic method would be thwarted by failing to imaging them. PurposeIn view of the technical difficulties in structural detection of those objects, a novel method named "Forward Comparison Method (FCM)" was proposed. MethodsBoth the deformation and its scale were identified effectively by directly evaluating the evolution of muon scattering properties with respect to the object. This method, instead of the traditional inverse one, showed a methodological superiority in detection of nuclear objects with prior knowledge of the original structure. ResultsPreliminary results based on a computational simulation demonstrated that FCM could be used to identify the horizontal slit in a uranium slab and evaluate its width on the magnitude of sub-millimeters, on condition that the muon flux was reasonable. ConclusionThe FCM method can be effectively applied in structural detection of particular nuclear objects of hollow structure on a satisfactory timescale.关键词：Muon;High-Z material;MCS;Non-parametric test;Receiver operating characteristic analysis
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发布时间：2021-05-19 - 摘要：BackgroundThe drift tube linac (DTL) is the main part of China Spallation Neutron Source (CSNS), which can provide 15-mA peak current beam with energy gain from 3 MeV to 80 MeV. And then the beam will be injected into the rapid cycling synchrotron (RCS) for further accelerating. PurposeThe manufacturing and fabrication of DTL cavity and drift tubes is very complicated, which requires high processing precision and installation accuracy. In this paper, the pre-alignment of DTL was introduced. MethodsWe overcame a lot of difficulties in this process, including the fiducialization, installation and alignment. By distributing the error properly and following the regular pre-alignment process, this work was finally finished on time. ResultsThe pre-alignment accuracy was better than the requirement tolerance which is 0.05 mm in three directions. ConclusionThe results show that the pre-alignment is successful. This job can provide some experiences to other alignment measurement with the same process.关键词：CSNS;Drift tube;Pre-alignment;Laser tracker
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发布时间：2021-05-19
LOW ENERGY ACCELERATOR, RAY AND APPLICATIONS
- 摘要：BackgroundIn an electron energy-loss spectroscopy (EELS) experiment, the electron emitted by the electron gun collides with atoms and molecules, and the momentum and energy of the scattered electron are analyzed by EELS, then the information of electronic structure and collision dynamics of the target can be deduced. PurposeA well designed intermediate-high energy electron gun with small beam size and divergence angle is needed to satisfy the requirement of EELS. MethodsTo obtain the optimal beam condition, the electron optics software SIMION was utilized to simulate the space size and divergence angle of the electron beam at target position, the electron gun has a simple structure, i.e., consisting of thermionic cathode, grid electrode, anode electrode, focus electrode and deflection plates. The tuning range of electron energy is wide (1-3 keV) and easy to operate. ResultsThe beam size of 0.95 mm, divergence angel of 0.93°, and beam current of 6.27 μA of the constructed electron gun was obtained at 27 mm from the exit of electron gun at a beam energy of 1.5 keV. ConclusionAn electron gun which satisfies the requirements of EELS has been developed.关键词：Electron gun;Thermionic cathode;Electron optics;Divergence angle;Beam current;Electron energy-loss spectrometer
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发布时间：2021-05-19 - 摘要：BackgroundSurface enhanced Raman scattering (SERS) has become an important molecular detection technology in the field of spectral analysis and biosensing during the last several decades.SERS substrates are usually fabricated by electron beam lithography (EBL), focus ion beam lithography (FIB), nanoimprint lithography (NIL), scanning probe lithography (SPL) and laser interference lithography (LIL).However, it is still a challenge to fabricate arrays with large area, small period and high output. PurposeThis study aims to rapidly fabricate a SERS substrate with large area and sub 100-nm pitch. MethodsThe SERS substrates were prepared by using X-ray interference lithography (XIL), then scanning electron microscope (SEM), atomic force microscope (AFM) and Raman spectrum were employed to examine their characteristics. ResultsThe detective limitation of SERS substrate can be as low to 10-9 mol·L-1.The relative standard deviations are achieved to be less than 10%. ConclusionThe SERS substrate with the advantages of sensitivity and reproductive provides a promising approach for future SERS applications.关键词：X-ray interference lithography;Metallic nano array;Surface enhanced Raman scattering
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发布时间：2021-05-19
SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS
- 摘要：BackgroundEfficient translocation of nucleic acid drugs into nucleus is a key factor in gene therapy. Therefore, real-time observation of the distribution of deoxyribonucleic acid (DNA) in the nucleus is very important to understand the effect of gene therapy. Beforehand, choosing a safe and efficient carrier for translocating DNA into nucleus is critical. PurposeThis work establishes composite structure of nucleus localization signal (NLS) and DNA tetrahedron, which improving the uptake efficiency of DNA tetrahedron into nucleus. MethodsCovalently connection NLS and DNA tetrahedron with "click" chemistry solved the problems of poor stability after simple mixing. And we further studied the connecting efficiency of different length and isoelectric point NLS with ssDNA. ResultsCompared with classical NLS12, NLS29 (of which isoelectric point is 4.84) had a low nonspecific binding. The binding efficiency of NLS29 was improved to 72.3% from 37.3%. After purification, both NLS12-DNA and NLS29-DNA could target to cell nucleus, thus verifying that they all possessed good activity. ConclusionThis research improved nonspecific binding between positively charged NLS and negatively charged DNA, which laid a foundation for clinical gene therapy.关键词：Cell nucleus;NLS;DNA tetrahedron;"Click" chemistry
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发布时间：2021-05-19 - 摘要：BackgroundDecommissioning nuclear facilities with less cost is a key part of nuclear reactor development, which mainly depends on the dismantling route based on the distribution of radiation field. Purpose:This study attempts to reconstruct the radiation field of decommissioning nuclear facilities and find out the optimal dismantling route. MethodsThe method of point-kernel integration is adopted to reconstruct the three-dimensional radiation field of multi-source terms during the decommissioning of nuclear facilities and the results are compared with the Monte Carlo program. A functional software is designed and developed with functions of radiation field reconstruction and removal route optimization during the nuclear facility decommissioning process. The problem of optimizing dismantling route is abstracted to a mathematical model of the Traveling Salesman Problem (TSP), and the Dose Matrix under different routes are constructed. According to ALARA (As Low As Reasonably Achievable) principle of the radiation protection, the methodology is optimized by genetic algorithm. ResultsThe reconstructed radiation field is in good agreement with the result calculated by the Monte Carlo program. Upon the instance of decommissioning multi-source terms' removal, the optimal route and three-dimensional visualization are calculated and obtained, and the optimal results are discussed. ConclusionThe method of point-kernel integration and the TSP mathematical model can be used during nuclear decommissioning.关键词：Nuclear decommissioning;Radiation field reconstruction;Dismantling route optimization;Functional software
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发布时间：2021-05-19
NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH
- 摘要：BackgroundA recent estimate indicates that the land-based uranium sources are only able to last for about a century. Consequently, it is imperative to exploit new uranium resources with an economically feasible method. The uranium dissolved in seawater is about 4.5×109 t, much larger than the terrestrial sources, even though its concentration in seawater is low (about 3.3 μg·L-1). Hence, it is essential to develop techniques for mining uranium from seawater in order to satisfy the demand for uranium for nuclear power plants in the future. PurposeThe aim of this work is grafting of poly (amidoxime) (PAO) and poly (acrylic acid) (PAA) onto polypropylene (PP) fibers to prepare the PP-g-P (AO-co-AA) fibrous adsorbents for recovery of uranium from seawater. MethodsThe PP-g-P (AO-co-AA) fibrous adsorbents were synthesized by electron beam pre-irradiation induced graft polymerization of AN and AA, followed by amidoximation. The surface morphology, chemical structure and thermal performance of the pristine and modified PP fibers were analyzed by attenuated total reflection Fourier transform infrared (ATR-FTIR), scanning electron microscope (SEM) and thermogravimetric analysis (TGA), respectively. The adsorption capacities of uranium and other metal ions by PP-g-P (AO-co-AA) fibrous adsorbents were evaluated after 68 d of immersion in natural seawater. Results and ConclusionThe uranium adsorption capacity of PP-g-P (AO-co-AA) fibers reached 0.81 mg·g-1 after 68 d of contact with natural seawater, and the uranium adsorption capacity did not show positive correlation with the degree of grafting and AO density of PP-g-P (AO-co-AA) fibers.关键词：Polypropylene fibers;Amidoxime group;Acrylic acid;Uranyl ions;Extraction of uranium from seawater
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发布时间：2021-05-19
NUCLEAR CHEMISTRY, RADIOCHEMISTRY, RADIOPHARMACEUTICALS AND NUCLEAR MEDICINE
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