Analysis of three LOCAs for the European HCPB test blanket system

Three LOCA sequences have been analysed in the frame of the safety assessment of the European helium cooled pebble bed (HCPB) test blanket module (TBM) system. These three sequences have been selected as representative of accidents judged to cover all scenarios envisaged in the design basis involving the TBMs. The three groups of accidents investigated with their parametric variations have as initiating event a loss of coolant accident at different location: in-vessel, in-box, and ex-vessel. In general the reduced inventory of activation products and Tritium associated with the TBM System makes the impact of this test system almost negligible to the overall safety risk of ITER. Nevertheless, the possibility to jeopardise the ITER safety concept has been analysed especially in connection to particular sequences that imply the pressurisation of the vacuum vessel due to the He coolant blow-down, the hydrogen and/or heat production from Be-steam or Be-air reaction and the necessity to assure the heat removal in the short and long period.