A stress test on ²³⁵U(n, f) in adjustment with HCI and HMI benchmarks

Abstract

Abstract. To understand how compensation errors occur in a nuclear data adjustment mostly devoted to U-Pu fuelled fast critical experiments and with only limited information on U-235 data, a stress test on 235 U(n,f) was suggested, using critical benchmarks sensitive to 235 U(n,f) in 1∼ 10 keV region. The adjustment benchmark exercise with 20 integral data suggested by the NEA WPEC/SG33 was used as the reference, where practically only one experiment did give information on U-235 data. The k ef f of HCI4.1 and HCI6.2 experimental benchmarks were used as the 21st and 22nd integral data separately to perform stress tests. The adjusted integral values and cross sections based on 20, 21 and 22 integral data using the same nuclear data and covariance data sets were compared. The results confirm that compensation errors can be created by missing essential constraints.

Method and approaches to provide feedback from nuclear and covariance data adjustment for improvement of nuclear data files: Major findings of the NEA WPEC Subgroup 39

“…• How to make adjustment more reliable and avoid compensation effects. Stress tests and innovative adjustment methods/strategies were developed [4,5,6,7].…”

Production and use of nuclear parameter covariance data: an overview of challenging cross cutting scientific issues

“…Stress tests performed within the group (see e.g. [10]), did once more point out to potential inconsistencies, if the integral data base was not carefully investigated and documented, in particular in terms of uncertainties, potential systematic errors and correlations.…”