Abstract
Induced radioactivities and decay heat are of significant importance in the nuclear design of a near-term D-T fusion device from the view point of the safety consideration. In the framework of the JAERI/USDOE collaborative program on fusion neutronics, extensive experimental efforts have been devoted to verify the validity of the calculation code systems THIDA-2, REACT-2 and DKR-ICF. In the previous study, it was clearly pointed out that there were large discrepancies for several important materials between the experiment and the calculation in terms of gamma-ray emission rates. This paper investigated the major sources of these large discrepancies. In addition to the previous ones, the analysis was carried out by THIDA-2 using an updated cross-section library. As a result, the following was pointed out: (1) The calculation of THIDA with the new activation cross-section library gave better agreement with experiment, especially for MnCu, W, Mo and V. As far as the higher neutron energy range above 1.0 MeV is concerned, all calculation code systems offer reasonable prediction accuracy. (2) For MnCu, W and Ta, uncertainty in the neutron spectrum was the main source for the large discrepancies because low-energy neutrons were very sensitive to the capture reaction products of Cu-64, W-187 and Ta-182.