EPJ A Highlight - From experiment to evaluation, the case of n+238U


Evaluated nuclear data represent the bridge between experimental and theoretical achievements and final user applications. The complex evolution from experimental data towards final data libraries forms the cornerstone of any evaluation process. Since more than 90% of the fuel in most nuclear power reactors consists of 238U, the respective neutron induced cross sections are of primary importance towards accurate neutron transport calculations. Despite this significance, the relevant experimental data for the 238U(n,γ) capture reaction have only recently provided for a consistent description of the resonance region. In this work, the 238U(n,γ) average cross sections were evaluated in the energy region 5-150 keV, based on recommendations by the IAEA Neutron Standards projects and experimental data not included in previous evaluations.

A least squares analysis was applied using exclusively microscopic data. This resulted in average cross sections with uncertainties of less than 1%, fulfilling the requirements on the High Priority Request List maintained by the OECD-NEA. The parameterisation in terms of average resonance parameters maintained consistency with results of optical model and statistical calculations. The final deliverable is an evaluated data file for 238U, which was validated by independent experimental data.

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