Recent developments in neutron dosimetry and radiation damage calculations for fusion materials studies

Abstract

This paper is intended as an overview of activities designed to characterize neutron irradiation facilities in terms of neutron flux and energy spectrum and to use these data to calculate atomic displacements, gas production, and transmutation during fusion materials irradiations. A new computerized data file, DOSFILE, has been developed to record dosimetry and damage data from a wide variety of materials test facilities. At present data are included from 20 different irradiations at fast and mixed-spectrum reactors, T(d,n) 14 MeV neutron sources, Be(d,n) broadspectrum sources, and spallation neutron sources. Each file entry includes activation data, adjusted neutron flux and spectral data, and calculated atomic displacements and gas production. Such data will be used by materials experimenters to determine the exposure of their samples during specific irradiations. This data base will play an important role in correlating property changes between different facilities and, eventually, in predicting materials performance in fusion reactors. All known uncertainties and covariances are listed for each data record and explicit references are given to nuclear decay data and cross sections. The computer code package SPECTER has also been revised and updated to permit rapid calculation of displacements, gas production, and total dose for any given neutron spectrum. Recent improvements include new calculations with ENDF/B-V neutron cross sections, inclusion of (n,γ) and β-decay processes, inclusion of kerma cross sections for total dose, and the ENDF/B-V gas-production file. Users need only provide a neutron spectrum, with uncertainties if known, and the code will calculate spectral-averaged values of the above quantities as well as recoil atom distributions. Both the DOSFILE and SPECTER computer codes are readily accessible to the fusion community via the National Magnetic Fusion Energy Computer at Lawrence Livermore Laboratory.