Analyses of temperature transients in ITER design concepts following hypothetical loss of cooling accidents

Bounding calculations of thermal transients following a hypothetical (Category V) loss of coolant accident in two international thermonuclear experimental reactor (ITER) design options, EU-I and ITER-fusion energy advanced tokamak (FEAT), have been carried out for a variety of assumptions concerning heat-transfer to and heat rejection from, the cryostat. It is shown that, even when unrealistically conservative assumptions are made in illustrative calculations, the temperatures do not approach melting point for any part of the plant structure. In all cases, maximum temperatures are reached within 1 year. It is also concluded that for the baseline scenario for ITER-FEAT in which helium gas is assumed to be present in the cryostat, convectively transferring heat between components, the outboard first-wall temperature never exceeds 530°C. A significant improvement could still be made if the surface emissivity of the thermal shields could be increased by some means during the post-accident period.