Calculation And Simulation On The Post-fission Physical Quantities For Fast Neutron-induced ²³⁹Pu Fission Based On Potential-driving Model

At present,higher-precision and higher-neutron-energy fission nuclear data of fast neutron-induced ²³⁹Pu?n,f?reaction is required for the study of new-generation nuclear systems and military industry.Due to various reasons,the experimental work of fast neutron-induced²³⁹Pu?n,f?reaction was less carried out.Besides,only several neutron-energy-point fission data is given in the evaluated nuclear database.In addition,because of the complexity of fission process,all the present developed theory models describing fission process have certain limitation and it is found that there is still a significant difference between the calculated results of post-fission physical quantities based on these theory models and the existing experimental data.Given the current demand and the research situation,the calculation and simulation on the post-fission physical quantities for fast neutron-induced ²³⁹Pu?n,f?reaction were carried out in this thesis-work based on the developed Potential-driving model describing heavy-nuclide fission,combined with Geant4 code.The main research contents and study results are as follows:The driving-potential distribution for ²³⁹Pu?n,f?reaction was calculated based on the Potential-driving model.The calculated results were compared with that based on the dinuclear?DNS?theoretical model,which shows a good consistency.Then,the primary-fragment mass distribution for several neutron-energy-point fast neutron-induced ²³⁹Pu?n,f?reactions was calculated based on the Potential-driving model.The calculated results were compared with the existing experimental data,which is also in good agreement.It is indicated that the developed Potential-driving model can well describe the pre-neutron-emission fission physical process for fast neutron-induced ²³⁹Pu?n,f?reaction and lay a foundation for simulation study of the post-neutron-emission fission physical process for fast neutron-induced ²³⁹Pu?n,f?reaction.The developed Potential-driving model was implanted into Geant4 code.And the Geant4code was optimized by constructing the excitation function of primary-fragment total kinetic energy to the incident neutron energy for less than 60 MeV neutron-induced ²³⁹Pu?n,f?reaction according to the Potential-driving model.The neutron cross section data for transuranic nuclei in ENDF library was added to section database of Geant4 and the calculation constraints of Geant4source code were also modified.The simulation of post-neutron-emission related fission nuclear data for 14 MeV fast neutron-induced ²³⁹Pu?n,f?reaction was carried out based on the Potential-driving model,combined with Geant4 code.The mass and charge distribution of independent yield and cumulative yield,fragment kinetic energy distribution,fission neutron spectrum,and average fission-neutron count for 14 MeV fast neutron-induced ²³⁹Pu?n,f?reaction were given.The simulated results were compared with the experimental data,the evaluated data in ENDF/B-VII.1 library and the simulated results based on G4ParaFissionModel model built in Geant4.It is found that the simulated results based on the Potential-driving model are well consistent with the experimental data and the evaluated data in ENDF/B-VII.1 library,and the consistency is better than the simulated results based on G4ParaFissionModel model.In addition,the average total kinetic energy of post-neutron-emission fission fragment for less than 60 MeV neutron-induced ²³⁹Pu?n,f?reaction as a function of the incident neutron energy was also showed.The simulated results were compared with the newly reported experimental data and the simulated results based on G4ParaFissionModel model built in Geant4.The consistency between the simulated results based on the Potential-driving model and the newly reported experimental data is also better than the simulated results based on G4ParaFissionModel model.The reliability and applicability of the Potential-driving model to describing the post-neutron-emission fission physical process for fast neutron-induced ²³⁹Pu?n,f?reaction further got examined and verified by the two parts of work.In the final part of this paper,the simulation-prediction of post-neutron-emission related fission nuclear data for less than 60 MeV fast neutron-induced ²³⁹Pu?n,f?reaction was carried out based on the Potential-driving model,combined with Geant4 code.The mass and charge distribution of independent yield,fragment kinetic energy distribution,fission neutron spectrum,and average fission-neutron count for different-energy fast neutron-induced ²³⁹Pu?n,f?reaction were presented.And the regularity was summarized and discussed.