Prompt fission neutron spectra of n+^(235)U above the(n,nf) fission threshold  

作　　者：舒能川 贾敏 陈永静 刘挺进 

机构地区：[1]Key Laboratory of Science and Technology on Nuclear Data, China Institute of Atomic Energy [2]Department of Mathematics and Information Science, North China University of Water Resources and Electric Power

出　　处：《Chinese Physics C》2015年第5期16-19,共4页中国物理C（英文版）

基　　金：Supported by National Natural Science Foundation of China(11205246,91126010,U1230127,91226102);AEA CRP(15905);Defense Industrial Technology Development Program(B0120110034)

摘　　要：Calculations of prompt fission neutron spectra （PFNS） from the ^235U（n, f） reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of （n,xnf） pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of （n,xnf） fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the （n,nf） or （n,2nf） reactions influences the PFNS shape, and the neutron spectra of the （n,xnf） fission-channel are soft compared with the neutron spectra of the （n,f） fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case.Calculations of prompt fission neutron spectra （PFNS） from the ^235U（n, f） reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of （n,xnf） pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of （n,xnf） fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the （n,nf） or （n,2nf） reactions influences the PFNS shape, and the neutron spectra of the （n,xnf） fission-channel are soft compared with the neutron spectra of the （n,f） fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case.

关 键 词：^235U（n f） neutron-induced fission prompt fission neutron spectrum 

分 类 号：O571.5[理学—粒子物理与原子核物理]