Experimental validation of calculations of decay heat induced by 14 MeV neutron activation of ITER materials

In a D-T fusion tokamak, neutron activation of structural material will res ult in a source of heat from radioactive decay after shutdown of the plasma . Although relatively small, in certain postulated loss-of-cooling accident s this decay heat could drive a temperature transient of modest proportions . In safety studies of the International Thermonuclear Experimental Reactor (ITER), such accident scenarios are analysed for their possible consequenc es, requiring an accurate knowledge of the level and time-dependence of the decay heat in components in which it is significant. This is calculated by activation modelling using computer codes with libraries of nuclear data. This paper describes an international benchmark activity to validate severa l of these codes and data, using the results of direct measurements of deca y heat in ITER-relevant materials after exposure to a flux of 14 MeV neutro ns. The results show consistency between the codes and, when using data fro m the recently-compiled FENDL/A-2 activation data library, good agreement w ith the experiments over the time-scales of interest in ITER safety studies . (C) 1999 Elsevier Science S.A. All rights reserved.