Prompt fissionγ-ray characteristics from neutron-induced fission on 239 Pu and the time-dependence of prompt-γray emission

• Published in: EPJ Web of conferences Vol. 169; p. 3
• Main Authors: Gatera, Angélique, Göök, Alf, Hambsch, Franz-Josef, Moens, André, Oberstedt, Andreas, Oberstedt, Stephan, Sibbens, Goedele, Vanleeuw, David, Vidali, Marzio
• Format: Journal Article
• Language: English
• Published: 2018
• ISSN: 2100-014X; 2100-014X
• DOI: 10.1051/epjconf/201816900003

Recent years have seen an increased interest in prompt fission γ-ray (PFG) measurements motivated by a high priority request of the OECD/NEA for high precision data, mainly for the nuclear fuel isotopes
235
U and
239
Pu. Our group has conducted a PFG measurement campaign using state-of-the-art lanthanum halide detectors for all the main actinides to a precision better than 3%. The experiments were performed in a coincidence setup between a fission trigger and γ-ray detectors. The time-of-flight technique was used to discriminate photons, traveling at the speed of light, and prompt fission neutrons. For a full rejection of all neutrons below 20 MeV, the PFG time window should not be wider than a few nanoseconds. This window includes most PFG, provided that no isomeric states were populated during the de-excitation process. When isomeric states are populated, PFGs can still be emitted up to 1 yus after the instant of fission or later. To study these γ-rays, the detector response to neutrons had to be determined and a correction had to be applied to the γ-ray spectra.
The latest results for PFG characteristics from the reaction
239
Pu(n
th
,f) will be presented, together with an analysis of PFGs emitted up to 200 ns after fission in the spontaneous fission of
252
Cf as well as for thermal-neutron induced fission on
235
U and
239
Pu. The results are compared with calculations in the framework of the Hauser-Feshbach Monte Carlo code CGMF and FIFRELIN.