Ricerc@Sapienza

The Breeding Blanket (BB) is one of the key components of the European Union Demonstration (EU-DEMO) fusion reactor. It accomplishes several functions, such as cooling device, tritium breeder (ensuring the reactor self-sufficiency) and neutron shield. Different BB concepts were selected to be investigated in the DEMO R&D strategy. Among them, there is the Water-Cooled Lithium-Lead (WCLL), that is the option of interest for the work planned in the current proposal. The WCLL blanket design relies on lithium-lead as breeder and neutron multiplier, pressurized water as coolant and EUROFER as structural material. It is divided in two main subsystems: the breeder zone (BZ) and the first wall (FW). Each one is provided with an independent cooling system, consisting of FW channels and Double-Wall Tubes (DWT), respectively. The two cooling circuits are strongly coupled within the Breeding Cell (BRC), that is the BB elementary unit. The power sources are the heat flux incident on the FW component and the nuclear heating, mostly produced by interactions between liquid breeder and plasma neutrons. The resulting BRC thermal field is quite complex. The aim of the proposed simulation activity is developing a detailed model of the WCLL-BB elementary cell by using RELAP5/Mod3.3 thermal-hydraulic (TH) system code. Calculations involving the BRC were already performed with more refined codes (CFD) to predict with a high level of detail its TH behavior during DEMO normal operations. The idea is to tune the RELAP5 model by using the outcomes of these simulations and then study the phenomena occurring in the elementary cell during accidental conditions. The advantages of this approach is saving computational time and the possibility to simulate two-phase flow (not easily modelled by CFD codes in transient condition). In this way, it is possible to evaluate if, in abnormal conditions, thermal crisis occurs within FW channels or DWTs, compromising the elementary cell structural integrity.