RAMI analyses for the primary heat transfer systems of breeding blankets and the related balance of plant of DEMO reactor

Two models are currently taken as reference for the breeding blanket (BB) of DEMO, the Helium Cooled Pebble Bed (HCPB) and the Water Cooled Lithium Lead (WCLL). For both the models two Balance of Plant (BOP) configurations are currently investigated. They are all based on four independent primary heat transfer systems (PHTSs). The largest PHTS is devoted to remove the BB thermal power, two PHTSs for the divertor (DIV) and one for the vacuum vessel (VV) heat removals. Both DIV loops and VV loop transfer their thermal power directly to the power conversion system (PCS). The two BOP configurations are investigated to cope with the pulsed operation of the reactor. The first configuration consists of an “indirect coupling” of the BB PHTS to the PCS by an Intermediate Heat Transfer System placed in between them. The second configuration consists in a “direct-coupling” of the BB PHTS to the PCS. Reliability, availability, maintainability and inspectability (RAMI) analyses for the four PHTS and PCS configurations are presented in this paper. The Failure Mode, Effect Analysis (FMEA) and the Reliability Block Diagram (RBD) methodologies have been used to perform the studies. As main result can be highlighted that even the low reliability of the systems to operate without failure and the large number of requests of corrective maintenance, all the systems are in compliance with an operational availability target of 30 %.