Research On Real Time Cross Sections Generation In Monte Carlo Neutron Transport With Wide Energy Region

During the temperatures changes in reactor core,the nuclide cross section in reactor can vary with temperature,which eventually causes the changes of reactivity.In order to simulate the interaction between incident neutron and various materials at different temperatures on the nose,it is necessary to generate all the relevant reaction temperature-dependent cross section.Traditionally,the real time cross section generation method is used to avoid storing huge data but contains servere problems of low efficiency and adaptability for narrow energy region.After full investigation on the status of real time cross section generation during Monte Carlo(MC)neutron transport simulation and the features of resolved resonance region,thermal region and unresolved resonance region,this paper focused on the research on multi-temperature cross sections generation in real time during in MC neutron transport based on Super Monte Carlo Program for Nuclear and Radiation Simulation(SuperMC),developed by Institute of Nuclear Energy Safety Technology,Chinese Academy of Sciences · FDS Team.The main contents and innovations in this study are summarized as follows:(1)Real time multi-temperature cross sections generation method based on double-exponential(DE)formula and Gauss-Hermite(GH)quadrature for resolved resonance region.After analyzing the feature of resolved resonance region.DE-GH method was proposed for broadening cross section.The cross section efficiency is improved by selecting different steps in DE formula and orders in GH quadrature in the premise of guarantee calculation accuracy.The cross section generation tests show the efficiency of cross section generation,compared with analytic method,is improved by a factor of 12.The benchmark of Jezebel and Godiva from ICSBEP show the effectiveness of the method.(2)Real time cross section generation method based on Neville interpolation for thermal region.According the features of thermal scattering cross section and scattering angular distribution at different temperature intervals,the Neville interpolation based real time thermal data generation method is proposed to generate cross section and any other thermal data.The International Nuclear Data Committee S(?,?)standard benchmark and other tests shows that the efficiency of thermal data generation can be improved by a factor of 10 in the premise of guarantee calculation.(3)Real time cross section generation method based on piecewised interpolation for unresolved resonance region.According to the features of probability table at different temperature intervals,the piecewised interpolation is proposed to generate unresolved resonance cross section.The international fast reactor model benchmark show the deviation is less than 20 pcm compared to reference value,which prove the accuracy of the method.In order to prove the correctness and validity of multi-temperature cross sections generation based on wide energy region of incident neutron,the proposed method was applied in critical safety benchmark tests,the benchmark of Doppler coefficient of reactivity and BN-600 benchmark tests.By comparing to the cross section generated by pre-processing or reference value,it revealed that the proposed method in MC neutron transport can generate neutron cross section and precisely at the desired temperature with consistent efficiency of traditional method.It showed the capability for application in reactor multi-physical coupling simulation.