Kun ZhuangYing-Zhen WangLi-Na DengYong-Zhan Wang...
123-137页
查看更多>>摘要：Small modular reactors have received widespread attention owing to their inherent safety,low investment,and flexibility.Small pressurized water reactors(SPWRs)have become important candidates for SMRs owing to their high technological maturity.Since the Fukushima accident,research on accident-tolerant fuels(ATFs),which are more resistant to serious accidents than conventional fuels,has gradually increased.This study analyzes the neutronics and thermal hydraulics of an SPWR(ACPR50S)for different ATFs,BeO+UO2-SiC,BeO+UO2-FeCrAl,U3Si2-SiC,and U3Si2-FeCrAl,based on a PWR fuel management code,the Bamboo-C deterministic code.In the steady state,the burnup calculations,reactivity coefficients,power and temperature distributions,and control rod reactivity worth were studied.The transients of the control rod ejection accident for the two control rods with the maximum and minimum reactivity worth were analyzed.The results showed that 5％B-10 enrichment in the wet annular burnable absorbers assembly can effectively reduce the initial reactiv-ity and end-of-life reactivity penalty.The BeO+UO2-SiC core exhibited superior neutronic characteristics in terms of burnup and negative temperature reactivity compared with the other three cases owing to the strong moderation ability of BeO+UO2 and low neutron absorption of SiC.However,the U3Si2 core had a marginally better power-flattening effect than BeO+UO2,and the differential worth of each control rod group was similar between different ATFs.During the transient of a control rod ejection,the changes in the fuel temperature,coolant temperature,and coolant density were similar.The maximum difference was less than 10 ℃ for the fuel temperature and 2 ℃ for the coolant temperature.
查看更多>>摘要：This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insula-tion in nuclear power plants(NPPs).The PP-based blend,comprising isotactic PP and propylene-based elastomer(PBE)at concentrations ranging from 0 to 50 wt％,underwent a melt blending process and subsequent cobalt-60 gamma-ray irradiation with doses ranging from 0 to 250 kGy.Electrical conductivity,trap distribution,and alternating(AC)breakdown strength were chosen to assess the insulation performance.These results indicate that the addition of PBE significantly improves the electrical properties of PP under irradiation.For PP,the electrical conductivity increased with irradiation,whereas the trap depth and breakdown strength decreased sharply.Conversely,for the blend,these changes initially exhibit opposite trends.When the irradiation was increased to 250 kGy,the AC breakdown strength of the blend improved by more than 21％compared to that of PP.The physical and chemical structures of the samples were investigated to explore the improvement mechanisms.The results offer insights into the design of new cable-insulation materials suitable for NPPs.
查看更多>>摘要：Gallium nitride(GaN)-based devices have significant potential for space applications.However,the mechanisms of radia-tion damage to the device,particularly from strong ionizing radiation,remains unknown.This study investigates the effects of radiation on p-gate AlGaN/GaN high-electron-mobility transistors(HEMTs).Under a high voltage,the HEMT leakage current increased sharply and was accompanied by a rapid increase in power density that caused"thermal burnout"of the devices.In addition,a burnout signature appeared on the surface of the burned devices,proving that a single-event burnout effect occurred.Additionally,degradation,including an increase in the on-resistance and a decrease in the breakdown volt-age,was observed in devices irradiated with high-energy heavy ions and without bias.The latent tracks induced by heavy ions penetrated the heterojunction interface and extended into the GaN layer.Moreover,a new type of N2 bubble defect was discovered inside the tracks using Fresnel analysis.The accumulation of N2 bubbles in the heterojunction and buffer layers is more likely to cause leakage and failure.This study indicates that electrical stress accelerates the failure rate and that improving heat dissipation is an effective reinforcement method for GaN-based devices.
查看更多>>摘要：By combining experimental α-decay energies and half-lives,the α-particle preformation factor for nuclei around neutron magic numbers N of 126,152,and 162 were extracted using the two-potential approach.The nuclei around the shell clo-sure were more tightly bound than adjacent nuclei.Additionally,based on the WS4 mass model(Wang et al.,Phys.Lett.B 734,215(2014)),we extended the two-potential approach to predict the α-decay half-lives of nuclei around N values of 178 and 184 with Z of 119 and 120.We believe that our findings will serve as guidelines for future experimental studies.
查看更多>>摘要：β-ray-induced X-ray spectroscopy(BIXS)is a promising method for tritium detection in solid materials because of its unique advantages,such as large detection depth,nondestructive testing capabilities,and low requirements for sample preparation.However,high-accuracy reconstruction of the tritium depth profile remains a significant challenge for this technique.In this study,a novel reconstruction method based on a backpropagation(BP)neural network algorithm that demonstrates high accuracy,broad applicability,and robust noise resistance is proposed.The average reconstruction error calculated using the BP network(8.0％)was much lower than that obtained using traditional numerical methods(26.5％).In addition,the BP method can accurately reconstruct BIX spectra of samples with an unknown range of tritium and exhibits wide applicabil-ity to spectra with various tritium distributions.Furthermore,the BP network demonstrates superior accuracy and stability compared to numerical methods when reconstructing the spectra,with a relative uncertainty ranging from 0 to 10％.This study highlights the advantages of BP networks in accurately reconstructing the tritium depth profile from BIXS and promotes their further application in tritium detection.
查看更多>>摘要：Shielding materials are critical for downhole pulsed neutron tool design because they directly influence the accuracy of for-mation measurements.A well-designed shield configuration ensures that the response of the tool is maximally representative of the formation without being affected by the tool and borehole environment.This study investigated the effects of boron-containing materials on neutron and gamma detectors based on a newly designed logging-while-drilling tool that is currently undergoing manufacturing.As the boron content increased,the ability to absorb thermal neutrons increased significantly.Through simulation,it was proven that boron carbide(B4C)can be used as an effective boron shielding material for thermal neutrons,and is therefore employed in this work.To shield against thermal neutrons migrating from the mud pipes,the optimal shielding thicknesses for the near-and far-neutron detectors were determined to be 5 and 4 mm.At a porosity of 25 p.u.,near-neutron sensitivity exhibited a 5.6％increase.Furthermore,to shield the capture gamma generated by thermal neutrons once they enter the tool from the mud pipe and formation,internal and external shields for the gamma detector were evaluated.The results show that the internal shield requires a boron content of 75％,whereas the external shield has a thickness of 14.2 mm thickness and a boron content of 25％to minimize the tool effect.
查看更多>>摘要：Schottky mass spectrometry utilizing heavy-ion storage rings is a powerful technique for the precise mass and decay half-life measurements of highly charged ions.Owing to the nondestructive ion detection features of Schottky noise detectors,the number of stored ions in the ring is determined by the peak area in the measured revolution frequency spectrum.Because of their intrinsic amplitude-frequency characteristic(AFC),Schottky detector systems exhibit varying sensitivities at different frequencies.Using low-energy electron-cooled stored ions,a new method is developed to calibrate the AFC curve of the Schottky detector system of the Experimental Cooler Storage Ring(CSRe)storage ring located in Lanzhou,China.Using the amplitude-calibrated frequency spectrum,a notable refinement was observed in the precision of both the peak position and peak area.As a result,the storage lifetimes of the electron-cooled fully ionized 56Fe26+ions were determined with high precision at beam energies of 13.7 and 116.4 MeV/u,despite of frequency drifts during the experiment.When electron cooling was turned off,the effective vacuum condition experienced by the 116.4 MeV/u 56Fe26+ions was determined using amplitude-calibrated spectra,revealing a value of 2 × 10-10 mbar,which is consistent with vacuum gauge readings along the CSRe ring.The method reported herein will be adapted for the next-generation storage ring of the HIAF facility under construction in Huizhou,China.It can also be adapted to other storage ring facilities worldwide to improve precision and enhance lifetime measurements using many ions in the ring.
查看更多>>摘要：Higher-order modes of the neutron diffusion/transport equation can be used to study the temporal behavior of nuclear reactors and can be applied in modal analysis,transient analysis,and online monitoring of the reactor core.Both the deterministic method and the Monte Carlo(MC)method can be used to solve the higher-order modes.However,MC method,compared to the deterministic method,faces challenges in terms of computational efficiency and α mode calculation stability,whereas the deterministic method encounters issues arising from homogenization-related geometric and energy spectra adaptation.Based on the higher-order mode diffusion calculation code HARMONY,we developed a new higher-order mode calculation code,HARMONY2.0,which retains the functionality of computing λ and α higher-order modes from HARMONYl.0,but enhances the ability to treat complex geometries and arbitrary energy spectra using the MC-deterministic hybrid two-step strategy.In HARMONY2.0,the mesh homogenized multigroup constants were obtained using OpenMC in the first step,and higher-order modes were then calculated with the mesh homogenized core diffusion model using the implicitly restarted Arnoldi method(IRAM),which was also adopted in the HARMONY1.0 code.In addition,to improve the calculation effi-ciency,particularly in large higher-order modes,event-driven parallelization/domain decomposition methods are embedded in the HARMONY2.0 code to accelerate the inner iteration of λ/α mode using OpenMP.Furthermore,the higher-order modes of complex geometric models,such as Hoogenboom and ATR reactors for λ mode and the MUSE-4 experiment facility for the prompt α mode,were computed using diffusion theory.
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