The system of point kinetics equations describes the time behaviour of a nuclear reactor, assuming that, during the transient, the spatial form of the flux of neutrons varies very little. This system has been largely ...The system of point kinetics equations describes the time behaviour of a nuclear reactor, assuming that, during the transient, the spatial form of the flux of neutrons varies very little. This system has been largely used in the analysis of transients, where the numerical solutions of the equations are limited by the stiffness problem that results from the different time scales of the instantaneous and delayed neutrons. Its derivation can be done directly from the neutron transport equation, from the neutron diffusion equation or through a heuristics procedure. All of them lead to the same functional form of the system of differential equations for point kinetics, but with different coefficients. However, the solution of the neutron transport equation is of little practical use as it requires the change of the existent core design systems, as used to calculate the design of the cores of nuclear reactors for different operating cycles. Several approximations can be made for the said derivation. One of them consists of disregarding the time derivative for neutron density in comparison with the remaining terms of the equation resulting from the P1 approximation of the transport equation. In this paper, we consider that the time derivative for neutron current density is not negligible in the P1 equation. Thus being, we obtained a new system of equations of point kinetics that we named as modified. The innovation of the method presented in the manuscript consists in adopting arising from the P1 equations, without neglecting the derivative of the current neutrons, to derive the modified point kinetics equations instead of adopting the Fick’s law which results in the classic point kinetics equations. The results of the comparison between the point kinetics equations, modified and classical, indicate that the time derivative for the neutron current density should not be disregarded in several of transient analysis situations.展开更多
针对用于高通量中子源的射频四极场(Radio Frequency Quadrupole,RFQ)加速器中交流电流互感器(Alternating Current Current Transformer,ACCT)的脉冲束流测量误差问题,本文提出基于波形解析的标定与校正方法。本文通过分析高脉冲占空...针对用于高通量中子源的射频四极场(Radio Frequency Quadrupole,RFQ)加速器中交流电流互感器(Alternating Current Current Transformer,ACCT)的脉冲束流测量误差问题,本文提出基于波形解析的标定与校正方法。本文通过分析高脉冲占空比工况下ACCT输出信号的基线漂移和脉冲衰减特性,设计了一套集成实时基线跟踪、漂移补偿和脉冲校正的电子学系统。该方法通过动态标定基线漂移量,构建了基于采样点极值的基线计算模型;针对脉冲束流设计线性插值补偿算法,可有效恢复幅度衰减。在西安交通大学加速器中子源装置的2.6 MeV/35 m A质子束流实验中进行验证,结果表明:经校正后2.4 ms脉宽束流的测量误差从4.9%降低至0.2%,使宽脉冲束流测量精度提升显著。该方法为高占空比加速器束诊系统提供了有效的在线校正解决方案。展开更多
本文设计一款基于国产芯片RS8491的堆外中子电流测量系统。该系统由跨阻放大器、量程切换电路、无效位电路、校验位电路以及信号处理模块组成。该系统能够实现补偿电离室的电流测量,具有自动量程切换功能,能够输出电流测试结果和倍增时...本文设计一款基于国产芯片RS8491的堆外中子电流测量系统。该系统由跨阻放大器、量程切换电路、无效位电路、校验位电路以及信号处理模块组成。该系统能够实现补偿电离室的电流测量,具有自动量程切换功能,能够输出电流测试结果和倍增时间信号。通过测试验证,该系统能够达到100f A分辨率,1 p A精准度,全量程精度、线性度和稳定性等指标均满足核电堆外中子电流测量的要求。展开更多
Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equati...Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equation. The bi-material reflector consists of binary combinations of water, graphite, lead, and polyethylene. An experimental measurement of thermal neutron albedo has also been conducted for mono-material and bi-material reflectors by using a^(241) Am–Be(5.2 Ci) neutron source and a BF3 detector. The maximum value of thermal neutron albedo was obtained for a polyethylene–water combination(0.95 ± 0.02).展开更多
柔性直流输电技术是大规模新能源外送的重要载体,未来我国大量的沙漠、戈壁、荒漠大规模新能源基地海拔偏高,甚至超过4000 m,宇宙射线大气中子通量大,严重威胁柔性直流换流阀(voltage sourced converter-high voltage direct current,VS...柔性直流输电技术是大规模新能源外送的重要载体,未来我国大量的沙漠、戈壁、荒漠大规模新能源基地海拔偏高,甚至超过4000 m,宇宙射线大气中子通量大,严重威胁柔性直流换流阀(voltage sourced converter-high voltage direct current,VSC-HVDC)功率器件的安全可靠运行。但是,目前我国柔性直流工程中换流阀尚无2000 m以上高海拔地区应用案例,国内外也缺乏大气中子辐照功率器件的失效率数据,大气中子对功率器件的影响规律不明,难以支撑工程应用。该文首次针对柔性直流使用的4.5 kV等级主流功率器件,提出绝缘栅双极型晶体管(insulated gate bipolar transistor,IGBT)、旁路转折晶闸管等功率器件高海拔大气中子辐照效应的等效加速试验方法,并开展试验,结合试验结果分析了器件工作电压、工作温度、中子通量对器件失效率的影响规律,得出高海拔地区IGBT和旁路转折晶闸管的大气中子辐照失效率,为高海拔VSC-HVDC的安全设计提供指导。展开更多
Neutron radiation experiments of optocouplers at back-streaming white neutrons(back-n)in China Spallation Neutron Source(CSNS)are presented.The displacement damages induced by neutron radiation are analyzed.The perfor...Neutron radiation experiments of optocouplers at back-streaming white neutrons(back-n)in China Spallation Neutron Source(CSNS)are presented.The displacement damages induced by neutron radiation are analyzed.The performance degradations of two types of optocouplers are compared.The degradations of current transfer ratio(CTR)are analyzed,and the mechanisms induced by radiation are also demonstrated.With the increase of the accumulated fluence,the CTR is degrading linearly with neutron fluence.The radiation hardening of optocouplers can be improved when the forward current is increased.Other parameters related to CTR degradation of optocouplers are also analyzed.展开更多
The pulsed working characteristics of the neutron tube ion source were studied experimentally. The principle and method of selecting the gas pressure and anode voltage were determined.
We show how the Koide relationships and associated triplet mass matrices can be generalized to derive the observed sum of the free neutron and proton rest masses in terms of the up and down current quark masses and th...We show how the Koide relationships and associated triplet mass matrices can be generalized to derive the observed sum of the free neutron and proton rest masses in terms of the up and down current quark masses and the Fermi vev to six parts in 10,000. This sum can then be solved for the separate neutron and proton masses using the neutron minus proton mass difference derived by the author in a recent, separate paper. The oppositely-signed charges of the up and down quarks are responsible for the appearance of a complex phase exp(iδ) and real rotation angle θ which leads on an independent basis to mass and mixing matrices similar to that of Cabibbo, Kobayashi and Maskawa (CKM). These can then be used to specify the neutron and proton mass relationships to unlimited accuracy using θ as a nucleon fitting angle deduced from empirical data. This fitting angle is then shown to be related to an invariant of the CKM mixing angles within experimental errors. Also developed is a master mass and mixing matrix which may help to interconnect all baryon and quark masses and mixing angles. The Koide generalizations developed here enable these neutron and proton mass relationships to be given a Lagrangian formulation based on neutron and proton field strength tensors that contain vacuum-amplified and current quark wavefunctions and masses. In the course of development, we also uncover new Koide relationships for the neutrinos, the up quarks, and the down quarks.展开更多
文摘The system of point kinetics equations describes the time behaviour of a nuclear reactor, assuming that, during the transient, the spatial form of the flux of neutrons varies very little. This system has been largely used in the analysis of transients, where the numerical solutions of the equations are limited by the stiffness problem that results from the different time scales of the instantaneous and delayed neutrons. Its derivation can be done directly from the neutron transport equation, from the neutron diffusion equation or through a heuristics procedure. All of them lead to the same functional form of the system of differential equations for point kinetics, but with different coefficients. However, the solution of the neutron transport equation is of little practical use as it requires the change of the existent core design systems, as used to calculate the design of the cores of nuclear reactors for different operating cycles. Several approximations can be made for the said derivation. One of them consists of disregarding the time derivative for neutron density in comparison with the remaining terms of the equation resulting from the P1 approximation of the transport equation. In this paper, we consider that the time derivative for neutron current density is not negligible in the P1 equation. Thus being, we obtained a new system of equations of point kinetics that we named as modified. The innovation of the method presented in the manuscript consists in adopting arising from the P1 equations, without neglecting the derivative of the current neutrons, to derive the modified point kinetics equations instead of adopting the Fick’s law which results in the classic point kinetics equations. The results of the comparison between the point kinetics equations, modified and classical, indicate that the time derivative for the neutron current density should not be disregarded in several of transient analysis situations.
文摘针对用于高通量中子源的射频四极场(Radio Frequency Quadrupole,RFQ)加速器中交流电流互感器(Alternating Current Current Transformer,ACCT)的脉冲束流测量误差问题,本文提出基于波形解析的标定与校正方法。本文通过分析高脉冲占空比工况下ACCT输出信号的基线漂移和脉冲衰减特性,设计了一套集成实时基线跟踪、漂移补偿和脉冲校正的电子学系统。该方法通过动态标定基线漂移量,构建了基于采样点极值的基线计算模型;针对脉冲束流设计线性插值补偿算法,可有效恢复幅度衰减。在西安交通大学加速器中子源装置的2.6 MeV/35 m A质子束流实验中进行验证,结果表明:经校正后2.4 ms脉宽束流的测量误差从4.9%降低至0.2%,使宽脉冲束流测量精度提升显著。该方法为高占空比加速器束诊系统提供了有效的在线校正解决方案。
文摘本文设计一款基于国产芯片RS8491的堆外中子电流测量系统。该系统由跨阻放大器、量程切换电路、无效位电路、校验位电路以及信号处理模块组成。该系统能够实现补偿电离室的电流测量,具有自动量程切换功能,能够输出电流测试结果和倍增时间信号。通过测试验证,该系统能够达到100f A分辨率,1 p A精准度,全量程精度、线性度和稳定性等指标均满足核电堆外中子电流测量的要求。
文摘Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equation. The bi-material reflector consists of binary combinations of water, graphite, lead, and polyethylene. An experimental measurement of thermal neutron albedo has also been conducted for mono-material and bi-material reflectors by using a^(241) Am–Be(5.2 Ci) neutron source and a BF3 detector. The maximum value of thermal neutron albedo was obtained for a polyethylene–water combination(0.95 ± 0.02).
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11875223,11805155,and 11690043)the Chinese Academy of Sciences Strategic Pilot Science and Technology Project(Grant No.XDA15015000)+1 种基金the Innovation Foundation of Radiation Application,China(Grant No.KFZC2018040201)the Foundation of State Key Laboratory of China(Grant Nos.SKLIPR1803 and 1903Z)
文摘Neutron radiation experiments of optocouplers at back-streaming white neutrons(back-n)in China Spallation Neutron Source(CSNS)are presented.The displacement damages induced by neutron radiation are analyzed.The performance degradations of two types of optocouplers are compared.The degradations of current transfer ratio(CTR)are analyzed,and the mechanisms induced by radiation are also demonstrated.With the increase of the accumulated fluence,the CTR is degrading linearly with neutron fluence.The radiation hardening of optocouplers can be improved when the forward current is increased.Other parameters related to CTR degradation of optocouplers are also analyzed.
文摘The pulsed working characteristics of the neutron tube ion source were studied experimentally. The principle and method of selecting the gas pressure and anode voltage were determined.
文摘We show how the Koide relationships and associated triplet mass matrices can be generalized to derive the observed sum of the free neutron and proton rest masses in terms of the up and down current quark masses and the Fermi vev to six parts in 10,000. This sum can then be solved for the separate neutron and proton masses using the neutron minus proton mass difference derived by the author in a recent, separate paper. The oppositely-signed charges of the up and down quarks are responsible for the appearance of a complex phase exp(iδ) and real rotation angle θ which leads on an independent basis to mass and mixing matrices similar to that of Cabibbo, Kobayashi and Maskawa (CKM). These can then be used to specify the neutron and proton mass relationships to unlimited accuracy using θ as a nucleon fitting angle deduced from empirical data. This fitting angle is then shown to be related to an invariant of the CKM mixing angles within experimental errors. Also developed is a master mass and mixing matrix which may help to interconnect all baryon and quark masses and mixing angles. The Koide generalizations developed here enable these neutron and proton mass relationships to be given a Lagrangian formulation based on neutron and proton field strength tensors that contain vacuum-amplified and current quark wavefunctions and masses. In the course of development, we also uncover new Koide relationships for the neutrinos, the up quarks, and the down quarks.
