235U(n, F), 233U(n, F) and 239Pu(n, F) Prompt Fission Neutron Spectra

New prompt fission neutron spectra (PFNS) matrices for the n+235U, n+233U and n+239Pu systems are prepared. Present and previous PFNS shapes are drastically different from each other, the former being consistent with measured data base. A combined generalized least-squares fit of nth+235U, nth+233U, nth+239Pu and 252Cf(sf) measured data base is accomplished. The solution of the longstanding problem of inconsistency of 235U integral data testing and differential prompt fission neutron spectra data (PFNS) is proposed. Similar problems for the n+233U and n+239Pu are envisaged, revealing arbitrary tweaking of relevant neutron cross sections. Fast 235U integral critical assemblies like Godiva or Flattop benchmarks are reproduced with the same accuracy as with the PFNS of the major data libraries. That reveals a rather delicate compensation effect, tracking the success of the distorted PFNS of the major data libraries to the excessive number of neutrons at energies of 1-3 MeV. Thermal assembly benchmarking reveals positive biases in keff, which might be attributed to the influence of a soft energy tail of the present PFNS. For some of Valduc's LCT benchmarks biases in keff are less than 20 pcm. Fast 239Pu integral critical experiments like Jezebel reveal the influence of overestimated inelastic scattering for 239Pu, arbitrarily introduced previously to diminish the influence on the keff of the distortion of the PFNS.

MASLOV V. M.;  TETEREVA N. A.;  PRONYAEV V. G;  KAGALENKO A.B.;  ZOLOTAREV K. I.;  CAPOTE R.;  GRANIER T.;  MORILLON B.;  HAMBSCH Franz-Josef;  SUBLET J.Ch.; 

2011-08-25

KOREAN PHYSICAL SOC

JRC58943

0374-4884,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC58943,   

10.3938/jkps.59.1337,