Analysis of the secondary circuit of the DEMO fusion power plant using GateCycle

Conceptual activities on the DEMO fusion power plant design are progressing in Europe under the lead of the EUROfusion Consortium. According to the current EU DEMO plant design, the Primary Heat Transfer System (PHTS) transfers heat from the nuclear heat sources, i.e. breeding blanket, divertor and (optionally) vacuum vessel, to the Power Conversion System (PCS) responsible for generating electric energy. To mitigate issues related to the pulsed DEMO operation, adding the Energy Storage System (ESS) filled with molten salt, between the PHTS and PCS, has been proposed. One of the four candidate options for the realization of the blanket and the related PHTS is the Water-Cooled Lithium-Lead Breeding Blanket (WCLL). In the present work a detailed GateCycle model of the DEMO PCS, for the option WCLL, with the ESS was created and its operation at the nominal conditions (plasma burn) and at the reduced heating power (dwell period) was studied. It was demonstrated, that during the dwell period the amount of heat provided from the ESS to the considered cycle can be safely reduced down to 50% of its nominal value. This is an important information for the ESS designers which should help in its proper sizing.