PPCS thermal analysis of bounding accident scenarios using improved computational modelling

Within the framework of the European Power Plant Conceptual Study (PPCS), evaluation of activation inventories and temperature excursions in structures following hypothetical worst-case accident scenarios was performed for the four plant models considered. An improved, three-dimensional computational tool was developed and extensively used to assist in the safety and environmental assessment of the PPCS power plant models. The tool allows for neutron transport, transmutation and thermal analyses to be automated and coupled to the same tokamak geometry. Convenient Monte Carlo and finite elements models of the plants can be easily developed, optimising time and computer resources and removing previous one-dimensional conservatism. The main features of this modelling tool, which for the first time includes an approximation of the divertor, are described here. Results from the bounding accident analyses of the four initial PPCS plant models are reported, including neutron spectra, activation inventories and temperature excursions up to 100 days after the initiation of the accident, at various radial and poloidal locations within the components. They confirm that not even in the bounding scenario significant structural degradation would be expected.