Producing Evaluation-quality 239Pu Average Prompt Fission Neutron Multiplicities using a Correlated Fission Model

Neudecker, Denise; Lovell, Amy Elizabeth; Talou, Patrick

doi:10.1051/epjconf/202328404017

Producing Evaluation-quality ²³⁹Pu Average Prompt Fission Neutron Multiplicities using a Correlated Fission Model

Journal Article · Fri May 26 00:00:00 EDT 2023 · EPJ Web of Conferences (Online)

DOI:https://doi.org/10.1051/epjconf/202328404017· OSTI ID:1990115

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Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

An evaluation of the average prompt fission neutron multiplicity, $$\bar{ν}_p$$, of ²³⁹Pu(n,f) is shown. This evaluation includes (a) the correlated fission model CGMF, and (b) a detailed analysis of past and recently published experimental data. Using CGMF-calculated $$\bar{ν}_p$$ as prior enables to link, through the use of evaluated model input parameters, $$\bar{ν}_p$$ to other fission observables such as the prompt fission neutron spectrum (PFNS), preneutron emission fission yields as a function of mass, and the average total kinetic energy of the fragments. These evaluated parameters produce realistic predictions of many fission observables, while the evaluated $$\bar{ν}_p$$ agrees well (χ² ≈ 1) with data. Moreover, with the new evaluated $$\bar{ν}_p$$, the effective neutron multiplication factor of fast Pu ICSBEP critical assemblies are predicted with a mean bias of 58 pcm compared to 18 pcm with ENDF/B-VIII.0, when paired with a new ²³⁹Pu PFNS and fission cross section. Due to these encouraging validation results, the evaluated $$\bar{ν}_p$$ is currently part of a release candidate for the ²³⁹Pu ENDF/B-VIII.1 file. Hence, a correlated fission model was used for the first time for evaluating $$\bar{ν}_p$$ that is of evaluation quality. This is an important step towards consistent evaluations of prompt fission observables.

Research Organization:: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA)

Grant/Contract Number:: 89233218CNA000001

OSTI ID:: 1990115

Report Number(s):: LA-UR--22-27724

Journal Information:: EPJ Web of Conferences (Online), Journal Name: EPJ Web of Conferences (Online) Vol. 284; ISSN 2100-014X

Publisher:: EDP SciencesCopyright Statement

Country of Publication:: United States

Language:: English

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