Investigation of the thermodynamic conditions in an underground nuclear power plant after core melt, in combination with a risk-oriented evaluation

Based on the present state-of-the-art on the project ''Core Melt'', funded by the Federal Ministry of Research and Technology (BMFT), the thermodynamic conditions occurring in the safety containment (and/or) outer annulus of undergroud NPPs have been evaluated for selected release categories. In order to evaluate the pressure- and temperature history as well as the leakages, a coupled two-room-model was constructed. The most serious consequences following an accident in an underground nuclear power plant must be expected for the failure of containment isolation valve, as corresponding to release category 2 of the German Risk Study (DRS) which differs only slightly from the accident scenario gained by above-ground siting of nuclear power plants. (orig.)