EPJ Nuclear Sci. Technol. 4, 35 (2018)
https://doi.org/10.1051/epjn/2018011

Regular Article

Cross-observables and cross-isotopes correlations in nuclear data from integral constraints

¹ CEA, DAM, DIF, 91297 Arpajon, France
² Laboratory for Reactor Physics Systems Behaviour, Paul Scherrer Institut, Villigen, Switzerland

^* e-mail: eric.bauge@cea.fr

Received: 31 October 2017
Received in final form: 16 January 2018
Accepted: 4 May 2018
Published online: 14 November 2018

Abstract

Most recent evaluated nuclear data files exhibit excellent integral performance, as shown by the very good agreement between experimental and calculated k_eff values over a wide range of benchmark integral experiments. However, the propagation of the uncertainties associated with those nuclear data to integral observables, generally produces calculated distribution which are much (3–5 times) wider than the experimental uncertainties. Reducing the variances of the evaluated data to achieve consistency at the integral level would lead to unreasonably narrow variances in the light of differential experimental data. One way of solving that paradox could be to allow, for different observables like fission cross-sections (σ_f), the prompt fission neutron spectra (χ), and the average multiplicity of fission neutrons (${\displaystyle \bar{\nu }}$) to be correlated in a Bayesian-like, Total Monte-Carlo approach, under constraints from integral experiments from the ICSBEP (International International Criticality Safety Benchmark Evaluation Project) benchmark compilation. Future developments will be highlighted and restrictions imposed by the current formatting of nuclear data will be discussed.