Prompt fission γ -ray data from spontaneous fission and the mechanism of fission-fragment de-excitation

• Main Authors: Oberstedt, Stephan, Dragic, Aleksandar, Gatera, Angelique, Göök, Alf, Hambsch, Franz-Josef, Oberstedt, Andreas
• Format: Conference Proceeding
• Language: English
• Subjects: Curium isotopes; Emission analysis; Energy measurement; Excitation; Fragmentation; Heat generation; Mass distribution; Neutron emission; Neutrons; Nuclear fission; Nuclear reactions; Photons; Plutonium
• ISSN: 2100-014X; 2101-6275; 2100-014X
• DOI: 10.1051/epjconf/201714604060

The investigation of prompt γ-ray emission in nuclear fission has a great relevance for the assessment of prompt heat generation in a reactor core and for the better understanding of the de-excitation mechanism of fission fragments. Some years ago experimental data was scarce and available only from a few fission reactions, 233,235U(nth, f), 239Pu(nth, f), and 252Cf(sf). Initiated by a high priority data request published by the OECD/NEA a dedicated prompt fission γ-ray measurement program is being conducted at the Joint Research Centre Geel. In recent years we obtained new and accurate prompt fission γ-ray spectrum (PFGS) characteristics (average number of photons per fission, average total energy per fission and mean photon energy) from 252Cf(sf), 235U(nth, f) and 239,241Pu(nth, f) within 2% of uncertainty. In order to understand the dependence of prompt fission γ-ray emission on the compound nuclear mass and excitation energy, we started a first measurement campaign on spontaneously fissioning plutonium and curium isotopes. Results on PFGS characteristics from 240,242Pu(sf) show a dependence on the fragment mass distribution rather than on the average prompt neutron multiplicity, pointing to a more complex competition between prompt fission γ-ray and neutron emission.