蒙特卡罗方法(MC)是模拟核探测问题的理想方法,用中子照射客体,中子诱发产生非弹γ和俘获γ,通过特征γ射线能谱和时间谱分析,确定客体核素组成和重量百分比.本文基于非弹γ和俘获γ时间门测量技术,给出了脉冲源发射下探测器响应计数公...蒙特卡罗方法(MC)是模拟核探测问题的理想方法,用中子照射客体,中子诱发产生非弹γ和俘获γ,通过特征γ射线能谱和时间谱分析,确定客体核素组成和重量百分比.本文基于非弹γ和俘获γ时间门测量技术,给出了脉冲源发射下探测器响应计数公式.在中子与核作用产生次级光子方面,采用期望值估计(expect value estimator,EVE)产光.为了避免大量小权光子模拟带来的计算存储量增加,设计了EVE产光与直接估计(direct estimator,DE)产光耦合.仅增加少量计算时间,便实现了特征γ射线解谱.数值模拟在自主MC软件JMCT上开展,计算结果初步验证了方法的正确有效性.展开更多
JMCT is a large-scale,high-fidelity,three-dimensional general neutron–photon–electron–proton transport Monte Carlo software system.It was developed based on the combinatorial geometry parallel infrastructure JCOGIN...JMCT is a large-scale,high-fidelity,three-dimensional general neutron–photon–electron–proton transport Monte Carlo software system.It was developed based on the combinatorial geometry parallel infrastructure JCOGIN and the adaptive structured mesh infrastructure JASMIN.JMCT is equipped with CAD modeling and visualizes the image output.It supports the geometry of the body and the structured/unstructured mesh.JMCT has most functions,variance reduction techniques,and tallies of the traditional Monte Carlo particle transport codes.Two energy models,multi-group and continuous,are provided.In recent years,some new functions and algorithms have been developed,such as Doppler broadening on-thefly(OTF),uniform tally density(UTD),consistent adjoint driven importance sampling(CADIS),fast criticality search of boron concentration(FCSBC)domain decomposition(DD),adaptive control rod moving(ACRM),and random geometry(RG)etc.The JMCT is also coupled with the discrete ordinate SNcode JSNT to generate source-biasing factors and weight-window parameters.At present,the number of geometric bodies,materials,tallies,depletion zones,and parallel processors are sufficiently large to simulate extremely complicated device problems.JMCT can be used to simulate reactor physics,criticality safety analysis,radiation shielding,detector response,nuclear well logging,and dosimetry calculations etc.In particular,JMCT can be coupled with depletion and thermal-hydraulics for the simulation of reactor nuclear-hot feedback effects.This paper describes the progress in advanced modeling,high-performance numerical simulation of particle transport,multiphysics coupled calculations,and large-scale parallel computing.展开更多
A cascadic multigrid method is proposed for eigenvalue problems based on the multilevel correction scheme. With this new scheme, an eigenvalue problem on the finest space can be solved by linear smoothing steps on a s...A cascadic multigrid method is proposed for eigenvalue problems based on the multilevel correction scheme. With this new scheme, an eigenvalue problem on the finest space can be solved by linear smoothing steps on a series of multilevel finite element spaces and nonlinear correcting steps on special coarsest spaces. Once the sequence of finite element spaces and the number of smoothing steps are appropriately chosen, the optimal convergence rate with the optimal computational work can be obtained. Some numerical experiments are presented to validate our theoretical analysis.展开更多
Presents a study that examined the application of an overlapping domain decomposition method to the solution of time-dependent convection-diffusion problems. Background on the Schwartz alternating procedure; Applicati...Presents a study that examined the application of an overlapping domain decomposition method to the solution of time-dependent convection-diffusion problems. Background on the Schwartz alternating procedure; Application of two kinds of Schwartz alternating procedure to solve the numerical approximation problem; Numerical results.展开更多
文摘蒙特卡罗方法(MC)是模拟核探测问题的理想方法,用中子照射客体,中子诱发产生非弹γ和俘获γ,通过特征γ射线能谱和时间谱分析,确定客体核素组成和重量百分比.本文基于非弹γ和俘获γ时间门测量技术,给出了脉冲源发射下探测器响应计数公式.在中子与核作用产生次级光子方面,采用期望值估计(expect value estimator,EVE)产光.为了避免大量小权光子模拟带来的计算存储量增加,设计了EVE产光与直接估计(direct estimator,DE)产光耦合.仅增加少量计算时间,便实现了特征γ射线解谱.数值模拟在自主MC软件JMCT上开展,计算结果初步验证了方法的正确有效性.
基金supported by the National Natural Science Foundation of China (Nos. 11805017 and 12001050)
文摘JMCT is a large-scale,high-fidelity,three-dimensional general neutron–photon–electron–proton transport Monte Carlo software system.It was developed based on the combinatorial geometry parallel infrastructure JCOGIN and the adaptive structured mesh infrastructure JASMIN.JMCT is equipped with CAD modeling and visualizes the image output.It supports the geometry of the body and the structured/unstructured mesh.JMCT has most functions,variance reduction techniques,and tallies of the traditional Monte Carlo particle transport codes.Two energy models,multi-group and continuous,are provided.In recent years,some new functions and algorithms have been developed,such as Doppler broadening on-thefly(OTF),uniform tally density(UTD),consistent adjoint driven importance sampling(CADIS),fast criticality search of boron concentration(FCSBC)domain decomposition(DD),adaptive control rod moving(ACRM),and random geometry(RG)etc.The JMCT is also coupled with the discrete ordinate SNcode JSNT to generate source-biasing factors and weight-window parameters.At present,the number of geometric bodies,materials,tallies,depletion zones,and parallel processors are sufficiently large to simulate extremely complicated device problems.JMCT can be used to simulate reactor physics,criticality safety analysis,radiation shielding,detector response,nuclear well logging,and dosimetry calculations etc.In particular,JMCT can be coupled with depletion and thermal-hydraulics for the simulation of reactor nuclear-hot feedback effects.This paper describes the progress in advanced modeling,high-performance numerical simulation of particle transport,multiphysics coupled calculations,and large-scale parallel computing.
基金Acknowledgments. This work is supported in part by the National Natural Science Foundation of China （NSFC 91330202, 11371026, 11001259, 11031006, 2011CB309703） and the National Center for Mathematics and Interdisciplinary Science, CAS.
文摘A cascadic multigrid method is proposed for eigenvalue problems based on the multilevel correction scheme. With this new scheme, an eigenvalue problem on the finest space can be solved by linear smoothing steps on a series of multilevel finite element spaces and nonlinear correcting steps on special coarsest spaces. Once the sequence of finite element spaces and the number of smoothing steps are appropriately chosen, the optimal convergence rate with the optimal computational work can be obtained. Some numerical experiments are presented to validate our theoretical analysis.
基金Project supported by the Natural Science Foundation of China Grant No. 19771050, No. 10171052 by the Foundation of National Key Laboratory of Computational Physics.
文摘Presents a study that examined the application of an overlapping domain decomposition method to the solution of time-dependent convection-diffusion problems. Background on the Schwartz alternating procedure; Application of two kinds of Schwartz alternating procedure to solve the numerical approximation problem; Numerical results.
