Re-evaluating the prompt fission neutron spectrum of spontaneously fissioning 252Cf

Neudecker, Denise; Kelly, Keegan John; Carlson, Allan D.; Pritychenko, Boris; Brown, David A.; Grosskopf, Michael John; Van der Wiel, Scott Alan; Haight, Robert Cameron; Capote, R.; Massey, T. N.; Trkov, A.; Walton, Noah Anthony Wy

doi:10.1051/epjn/2025061

Re-evaluating the prompt fission neutron spectrum of spontaneously fissioning ²⁵²Cf

Journal Article · Wed Nov 05 04:00:00 EST 2025 · EPJ Nuclear Sciences and Technologies

DOI:https://doi.org/10.1051/epjn/2025061· OSTI ID:3003174

^[1]; ^[1]; Carlson, Allan D. ^[2]; ^[3]; ^[3]; ^[1]; ^[1]; Haight, Robert Cameron ^[1]; Capote, R. ^[4]; ^[5]; ^[6]; ^[7]

Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)
Brookhaven National Laboratory (BNL), Upton, NY (United States)
International Atomic Energy Agency (IAEA), Vienna (Austria)
Ohio Univ., Athens, OH (United States)
Jozef Stefan Inst. (IJS), Ljubljana (Slovenia)
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Univ. of Tennessee, Knoxville, TN (United States)

The prompt fission neutron spectrum (PFNS) of spontaneously fissioning ²⁵²Cf is a Neutron Data Standards observable. Nearly all fission spectra of actinides were measured relative to it, using efficiencies derived from it, or analyzed with simulations validated by it. The current Standards evaluation was published by W. Mannhart in 1987. It could not be updated because the evaluation input, experimental mean values and covariances, were lost. First, we attempt to reproduce it. However, Mannhart’s evaluation can only be reproduced within its one-σ uncertainties as some of its aspects (e.g., experimental covariances, rejected data points) remain unknown. Therefore, a new evaluation is presented: We revisit all existing experimental ²⁵²Cf(sf) PFNS data, including those published after the release of the current Standards evaluation, and re-estimate associated covariances. The newly evaluated ²⁵²Cf(sf) PFNS differs distinctly from Mannhart’s below 300 keV and extends it to lower and higher outgoing neutron energies (500 eV–25 MeV). The new evaluated uncertainties are larger from 3–9 MeV and smaller otherwise. Spectrum averaged cross sections of importance to the International Reactor Dosimetry and Fusion File community calculated with the new spectrum are close to those calculated with Mannhart’s evaluation and agree with experimental values well within their uncertainties.

View Accepted Manuscript (DOE)

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

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Nuclear Physics (NP)

Grant/Contract Number:: 89233218CNA000001; NA0003996; AC02-98CH10886

OSTI ID:: 3003174

Alternate ID(s):: OSTI ID: 3004709

Report Number(s):: LA-UR--24-24178; 10.1051/epjn/2025061; 2491-9292

Journal Information:: EPJ Nuclear Sciences and Technologies, Journal Name: EPJ Nuclear Sciences and Technologies Vol. 11; ISSN 2491-9292

Publisher:: EDP SciencesCopyright Statement

Country of Publication:: United States

Language:: English

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