Design and Analysis of the Secondary Circuit of the DEMO Fusion Power Plant for the HCPB BB Option without the Energy Storage System and with the Auxiliary Boiler

The EU DEMO (European DEMOnstration Fusion Power Plant) is being designed to produce fusion electricity at a level of several hundred MW, by about 2060. The Primary Heat Transfer System (PHTS) transfers heat from the fusion reactor heat sources, to the Power Conversion System (PCS) responsible for the generation of electricity. Four cooling concepts for the DEMO Breeding Blanket (BB) and the related PHTS are considered. In some variants the Intermediate Heat Transfer System (IHTS) including the Energy Storage System (ESS) has been added between the PHTS and PCS, in order to mitigate transient effects resulting from the pulsed plasma operation, butother options with a direct coupling of the PHTS with the PCS are also being investigated. In the present work a detailed GateCycle model of the steam/water PCS, for the option Helium Cooled Pebble Bed BB without theIHTS/ESS and with an auxiliary boiler is created and its operation at the nominal conditions (plasma pulse) andat thermal power reduced down to ~50 % of the nominal value (dwell period) is studied. The proposed model of the PCS cycle is used to demonstrate potential possibility of stable operation of a EU DEMO plant without the IHTS/ESS during both pulse and dwell phases. It was shown, that the proposed PCS circuit can operate with the gross electrical power of 1120 MW and 547 MW during the pulse and dwell phase, respectively.