Abstract
Recent measurements of reactor-produced antineutrino fluxes and energy spectra are inconsistent with models based on measured thermal fission beta spectra. In this paper, we examine the dependence of antineutrino production on fission neutron energy. In particular, the variation of fission product yields with neutron energy has been considered as a possible source of the discrepancies between antineutrino observations and models. In simulations of low-enriched and highly-enriched reactor core designs, we find a substantial fraction of fissions (from 5% to more than 40%) are caused by nonthermal neutrons. Using tabulated evaluations of nuclear fission and decay, we estimate the variation in antineutrino emission by the prominent fission parents U235, Pu239, and Pu241 versus neutron energy. The differences in fission neutron energy are found to produce less than 1% variation in detected antineutrino rate per fission of U235, Pu239, and Pu241. Corresponding variations in the antineutrino spectrum are found to be less than 10% below 7 MeV antineutrino energy, smaller than current model uncertainties. We conclude that insufficient modeling of fission neutron energy is unlikely to be the cause of the various reactor anomalies. Our results also suggest that comparisons of antineutrino measurements at low-enriched and highly-enriched reactors can safely neglect the differences in the distributions of their fission neutron energies.
| Original language | English |
|---|---|
| Article number | 074022 |
| Journal | Physical Review D |
| Volume | 97 |
| Issue number | 7 |
| DOIs | |
| State | Published - Apr 1 2018 |
| Externally published | Yes |
Funding
We thank A. Hayes and A. Sonzogni for providing nuclear structure and fission yield data files used in this work. The work of the IIT group was funded by DOE Office of Science, under DOE OHEP DE-SC0008347, as well as by the IIT College of Science. The research of the Georgia Tech group was performed under appointment to the Nuclear Nonproliferation International Safeguards Fellowship Program sponsored by the Nation Nuclear Security Administrations Office of International Nuclear Safeguards (NA-241). Work at Lawrence Berkeley National Laboratory was supported under DOE OHEP DE-AC02-05CH11231. We thank A. Hayes and A. Sonzogni for providing nuclear structure and fission yield data files used in this work. The work of the IIT group was funded by DOE Office of Science, under DOE OHEP DE-SC0008347, as well as by the IIT College of Science. The research of the Georgia Tech group was performed under appointment to the Nuclear Nonproliferation International Safeguards Fellowship Program sponsored by the Nation Nuclear Security Administration’s Office of International Nuclear Safeguards (NA-241). Work at Lawrence Berkeley National Laboratory was supported under DOE OHEP DE-AC02-05CH11231.
| Funders | Funder number |
|---|---|
| DOE Office of Science | DOE OHEP DE-SC0008347 |
| IIT College of Science | |
| Nation Nuclear Security Administration’s Office of International Nuclear Safeguards | OHEP DE-AC02-05CH11231, NA-241 |
| U.S. Department of Energy | |
| Lawrence Berkeley National Laboratory |