Improved computational modelling of temperature transients during bounding accidents in fusion power plant advanced conceptual designs

The European Power Plant Conceptual Study (PPCS) aims to provide insight on physics and technology issues of commercial fusion power through the conceptual design and performance analysis of several power plants. Part of the safety assessment of these involves the estimation of temperature excursions in structures following worst-case accident scenarios, which usually assume total loss of coolant/flow for a prolonged time and activation decay as the only heat source during the transient. Results should ensure that the integrity of structures is not challenged, and assist in the estimation of any potential for releases and doses to public. Within the PPCS framework an improved, three-dimensional, finite element (FE) based methodology and computational tool have been developed and used to conduct the thermal analyses for the different plant models. It is now possible to couple the neutron transport, activation and thermal analysis calculations to the same 3D geometry, and to generate convenient FE plant models optimising time and computer resources and removing 1D conservatism. The main features of this tool and models, which for the first time include a representation of the divertor, are described here. Results from analysis of the two advanced PPCS plant designs are presented: they show that no significant structural degradation is expected, even in the bounding scenario.