Prior for Structural Materials

D Neudecker,St Gundacker,Th Srdinko,V Wildpaner,H Leeb

doi:10.1051/epjconf/20122700010

D Neudecker, St Gundacker + Show 3 more

Open Access

https://doi.org/10.1051/epjconf/20122700010

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Abstract

The construction of a library containing prior cross sections and related covariance matrices for nine frequently measured reaction channels of 276 structural materials from 1 to 150 MeV is presented. This library provides a starting point for future evaluations and reduces them to the analysis of experimental data. The prior cross sections were calculated using the nuclear reaction programs of TALYS1.0 and TALYS1.2 with the implemented global and local neutron and proton optical potential parameter sets. The prior covariance matrices contain contributions stemming from parameter uncertainties and model deficiencies. The associated procedures are discussed and an example evaluation with these prior cross sections and covariance matrices is shown for one specific isotope. These developments are of great importance with regard to the reliability of evaluations strongly based on model calculations. This is particularly true for the extension of the energy range as requested by the development of novel nuclear technologies.

Highlights

Current efforts in nuclear data evaluation are triggered by the development of novel nuclear technologies and safety requirements
We present a library with prior sets for 276 isotopes relevant for structural materials
Summary and Outlook place while at 20 MeV the experimental information ends. These kinks occur both in the global TALYS1.0 prior and in the evaluation starting from the prior of [10], the kink at 12 MeV is less pronounced with the prior of [10]

Summary

Introduction

Current efforts in nuclear data evaluation are triggered by the development of novel nuclear technologies and safety requirements. A reliable uncertainty estimate of nuclear calculations must account at least for the limited knowledge of model parameters as well as for the deficiencies of the model The former depends strongly on the admissible bounds of model parameters, which should be chosen reasonably, best on the basis of physics and mathematics constraints. The cross sections and associated covariance matrices generated by nuclear models represent the prior knowledge for the evaluation procedure. The employed models implemented in TALYS are not adequate for the other mass-values Only those isotopes were calculated for which at least three experimental data sets are available in EXFOR [6] for five channels of Table 1. The prior cross sections and covariance matrices are given in ENDF-6 format in order to comply with the standard format of nuclear data evaluation. A general description of the generation procedure and details for the specific isotope are given in MF=1 files

Theoretical Cross Sections σth

Parameter Uncertainty Covariance Matrices A0PU

Model Defect Covariance Matrices A0MD

Findings

The Complete Prior