The Computer Simulation Study About New Measurement Technology For U-Pu Content

In this thesis, for analyzing U-Pu content in the spent fuel from reactor, a non-destructive measurement method is proposed. This method also will give support for Accelerator driven subcritical system (ADS).In this method, the U-Pu conten in spent fuel will be obtained by measuring the low-energy neutron-induced prompt neutron and delayed neutron emission. The GEANT4is used to validate this method. We have modified the original GEANT4for simulations with low energy neutron. The main modifications involved are including interaction processes and the corresponding reaction cross sections for low energy neutrons, i.e., neutron-induced fission and neutron capture process. The elastic and inelastic scattering are neglected since their cross-sections are extremely small.The content of U-Pu in the spent fuel is simuated with1-eV neutrons. The prompt neutron counts differential spectrum as well as the delayed neutron counts differential and integral spectrum are obtained. This provides the time information for measuring the delayed neutron emission and deciding the tim width of neutron pulse. The incident energy of the neutrons are also varied from0.8to1.0eV. By comparing the results from simuations and the preset U-Pu content, almost no difference is found. The factors that influence the accuracy of this method are estimated. The efficiency of the neutron detector for fission neutron is also obtained by simulation.Our simulations provide knowledges to improve the design for future experiments.