"Looking at time behaviour of neutrons in a reactor on time scales of both ~sec and ~days/months Start with fission process e.g. 235U + n -> 236U ->fission Usually divide into 2 Fission Fragments 10%-20% of fission emit a scission neutron (i.e. at time of scission)" I've heard about prompt neutrons and delay neutrons, but what is scission neutrons? By means of scission I think it's prompt neutrons, but I don't think the yield of prompt neutrons is that low. Does any one know any thing about scission neutrons?