New approaches to provide feedback from nuclear and covariance data adjustment for effective improvement of evaluated nuclear data files

Abstract

Abstract.A critical examination of the role of uncertainty assessment, target accuracies, role of integral experiment for validation and, consequently, of data adjustments methods is underway since several years at OECD-NEA, the objective being to provide criteria and practical approaches to use effectively the results of sensitivity analyses and cross section adjustments for feedback to evaluators and experimentalists in order to improve without ambiguities the knowledge of neutron cross sections, uncertainties, and correlations to be used in a wide range of applications and to meet new requirements and constraints for innovative reactor and fuel cycle system design. An approach will be described that expands as much as possible the use in the adjustment procedure of selected integral experiments that provide information on "elementary" phenomena, on separated individual physics effects related to specific isotopes or on specific energy ranges. An application to a large experimental data base has been performed and the results are discussed in the perspective of new evaluation projects like the CIELO initiative.

Examples of Use of SINBAD Database for Nuclear Data and Code Validation

“…Furthermore, the ASPIS-Iron88 iron benchmark (see Fig. 1) study was also used in the scope of the WPEC WG39 [5,6] including complete sensitivity and uncertainty analysis combined with data adjustment. [7], JEFF-3.3T2, and two recent CIELO evaluations "ib04s" and "ib88" [8]) were used in the MCNP-6 simulation of the benchmark.…”

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

“…Even to obtain a special purposed library, input information has to be carefully prepared. New approaches have been proposed to avoid as much as possible compensations and some discussion will be made in a companion paper at this Conference [6].…”

Cross section covariances: a user perspective

“…An initial large set of 158 experiments was used [13]. This set includes not only criticality and reaction rate (spectral indices) measurements but also sample irradiations, reactivity measurements and neutron propagation experiments.…”

“…Ref. [13]). The discrepancies between calculations and experiments are particularly remarkable for the K eff of the ZPR9-34 and ZPR3-54 for both sets CIELO and CIELO-2.…”