Open Problems for Neutron Emission in Fission

Abstract The Prompt Fission Neutron Spectra (PFNS) in particular for 235 U(n th ,f) were investigated in numerous experimental and theoretical works. However we cannot answer on many questions: what is the spectrum shape, why different shape was estimated on the basis of microscopic and macroscopic (Mic-Mac problem) experiments, what the mechanism of neutron emission is in fission. This report summarizes recent achievements, and highlights open problems, which should be solved.