Methods and approaches to provide feedback from nuclear and covariance data adjustment for improvement of nuclear data files

Palmiotti, G.*; Salvatores, M.*; Yokoyama, Kenji   ; Ishikawa, Makoto

For providing useful and physical feedback to nuclear data evaluators from cross section adjustment results, it is necessary to assess the reliability of the adjustment results. In addition, useless and unphysical systematic effects may occur in the cross section adjustments. In order to avoid the compensation effects and to point out systematic effects, several criteria with associated parameters/indices are recommended to be used. This document summarizes the methodology with the definitions of the parameters/indices. On the other hand, covariance data play an important role in the cross section adjustment. As one of contributions to the nuclear data evaluators, several comments or recommendations on the covariance data are described. To make the comments concrete and useful, the covariance data of the latest evaluated nuclear data libraries, JENDL-4.0 and ENDF/B-VII.1 are treated. The surveyed nuclides are five isotopes that are most important for fast reactor application. The two latest evaluated nuclear-data libraries supply excellent covariance data from the viewpoints of both quality and quantity. However, it is also true that the evaluation of the covariance data has not yet been matured or converged on the satisfactory level in their applications, therefore, the close communication on the evaluation of the covariance data is indispensable between the nuclear-data evaluators and users.