Design of the secondary circuit for the WCLL BB option of the EU DEMO power plant based on the new Energy Map

Abstract

EU-DEMO will be a DEMOnstration Fusion power plant that is being designed to demonstrate the production of electricity from nuclear fusion at the level of a few hundred MW. The Primary Heat Transfer System (PHTS) transfers heat from the reactor to the Power Conversion System (PCS, the secondary circuit), responsible for converting the thermal power into electricity. According to the recent DEMO Energy Map data, In-Vessel components such as Breeding Blanket (BB), Divertor (DIV), Limiters, Vacuum Vessel and Auxiliaries feature uncertainties in generated thermal power. Some of them serve PCS as heat sources, namely: BB and DIV. Two reference concepts of the BB have been selected as a result of the DEMO pre-conceptual studies: the Helium Cooled Pebble Bed and the Water Cooled Lithium-Lead (WCLL). Because of the mentioned uncertainties regarding the distribution of energy released from fusion among the different reactor heat sources, several possible operational scenarios are considered. One of the challenges faced by the DEMO plant designers is the pulsed operation of the tokamak: plasma burn pulses (2 h) will be separated by dwell phases (10 min). To compensate drastic power reduction of the reactor heat sources during dwell, an Energy Storage System (ESS) of different sizes is included in considered DEMO plant configurations.Our work is focused on the design and analysis of the DEMO PCS circuit for the option WCLL BB with the small ESS. We create the GateCycle model of the “maximum of maximum” PCS cycle, in which the plant components are sized to incorporate the maximum power of all the reactor heat sources. Operation of the PCS circuit during the pulse (in the “Design” mode) and during dwell (in the “Off-design” mode with the fixed design of all the circuit components) is simulated, to verify the system performance and the potential feasibility of the considered PCS concept.