The fast neutron induced fission cross section of 240,242Pu

Based on a sensitivity study performed by the Nuclear Energy Agency (NEA) for the next generation of nuclear power plants (GEN-IV), a list of high priorities of the most important isotopes and their relevant quantities was prepared. Within the high priority list it is requested to improve the uncertainty of the neutron-induced fission cross section of 242Pu from the current 20% to 5%, and that of 240Pu to an uncertainty within 1-3%, compared to the present 5%. In this paper the results from recent 240,242Pu(n,f) cross-section measurements will be presented. The major difference to other literature studies of these fission cross sections are the fact that three different reference targets have been used, namely 235,238U and 237Np. In addition the spontaneous fission half-lives of 240,242Pu have been re-measured with unprecedented statistical accuracy. For 240Pu(n,f) our results reproduce the fission threshold very well but in the plateau region the difference to the evaluations is about 5 %. For 242Pu(n,f) our results show a deviation already in the threshold region where the present data tend to a less steep rise of the fission cross section. Furthermore the resonance like structure around 1.1 MeV seen in the evaluations is not present in our data. In addition, in the plateau region up to about 2.5 MeV our data are 7-9% lower than the evaluations.JRC.G.2-Standards for Nuclear Safety, Security and Safeguar