The energy dependence of fission-fragment characteristics for neutron-induced fission on Pu-239
This report is in response to a nuclear data request on the OECD-NEA high priority request list for new measurements of prompt neutron multiplicities from 239Pu(n,f) in the incident neutron energy range from thermal to 5 eV. There exists experimental evidence for strong fluctuations of the average neutron multiplicity from resonance to resonance in 239Pu(n,f). These fluctuations have been shown to impact nuclear reactor benchmarks by reducing the criticality. One explanation for the fluctuating neutron multiplicity may be the competition between direct fission and the (n,γf) process. However, there is also evidence for fluctuations of the fission fragment mass yields from resonance to resonance. The mass yield fluctuations may also contribute to fluctuations of the neutron multiplicity averaged over all fission fragment masses. In order to model the contribution to the neutron multiplicity fluctuations by the fission fragment mass yield fluctuations new data on the correlations between fission fragment properties and neutron multiplicities are in need.
In this report we present an experiment carried out to determine prompt neutron multiplicity correlations with fission fragment masses and total kinetic energies. The experiment has been carried out at the GELINA facility at JRC-Geel. Correlations between average neutron multiplicities and fission fragment properties have been measured with improved resolution in both mass and TKE, compared to data from the literature. Results show that the dependence of average neutron multiplicity per fission and fission fragment mass split is weak.
GÖÖK Alf;
OBERSTEDT Stephan;
2018-12-06
Publications Office of the European Union
JRC113720
978-92-79-98076-3 (online),
1831-9424 (online),
EUR 29472 EN,
OP KJ-NA-29472-EN-N (online),
https://publications.jrc.ec.europa.eu/repository/handle/JRC113720,
10.2760/517998 (online),
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