Fission mode fluctuations in the resonances of 235U(n,f)

Event-by-event evaluation of the prompt fission neutron spectrum from239Pu(n,f)

“…This feature is consistent with measurements made with 235 U and 238 U targets over similar ranges of incident neutron energy, 0.5 ≤ E n ≤ 6 MeV [19] and 1.2 ≤ E n ≤ 5.8 MeV [62], respectively. In both cases, the average TKE changes less than 1 MeV over the entire energy range.…”

“…the probability of a given mass partition before neutron evaporation has begun. While no such data are yet available for Pu, there exist more detailed data for 235 U(n, f ) that give the fragment yields as functions of both mass and total kinetic energy, Y (A f , TKE) for E n ≤ 6 MeV [19]. Guided by the energy dependence of these data, together with other available data on the product yields from 235 U(n, f ) [20] and 239 Pu(n, f ) [21] we derive an approximate energy dependence of the fragment yields for 239 Pu(n, f ) up to E n = 20 MeV.…”

“…We fix the energy dependence of σ i from the 235 U(n, f ) fragment yields as a function of mass and total kinetic energy of Ref. [19]. To adjust our results for 235 U(n, f ) to Pu, we assume that general energy dependence of the parameters is the same even though the values at E n = 0 are different.…”

Fission cross-sections, prompt fission neutron and γ-ray emission in request for nuclear applications

“…The TKE shows a strongly fluctuating behaviour as a function of the incident neutron energy, confirming the results of Ref. [9].…”

“…To improve nuclear modelling and similarly the evaluation of nuclear data the knowledge about fluctuations in the prompt neutron multiplicity as a function of incident neutron energy is requested for the major actinides 235 U and 239 Pu [2,3]. Fluctuations in fission fragment mass and total kinetic energy (TKE) for both isotopes have been observed in resonance-neutron induced fission [9,10]. Independently, the fluctuation in the number of emitted neutrons has been observed, too [11].…”