ST-E1 dual-cooled and self-cooled blanket concepts

We analyse liquid-metal (LM) blanket designs for the Tokamak Energy (TE) ST-E1 spherical tokamak power plant, with the aim of improving thermal efficiency and reducing pumping losses relative to the TE base design—a He-cooled Li blanket. Specifically, we consider two promising alternative LM blanket concepts. First, we examine the feasibility of a dual-cooled Li blanket, in which surface heat is removed by He flowing through channels in the first wall, while volumetric heat is removed by flowing Li, which also serves as the tritium breeder. The blanket is subdivided into several flow channels, and an efficient flow arrangement is proposed to achieve a nearly uniform outlet temperature. The analysis indicates that the total magnetohydrodynamic (MHD) pressure drop associated with this configuration is approximately 0.2–0.5 MPa, depending on the internal flow arrangement. Second, we investigate a self-cooled Li blanket, in which both surface and volumetric heat are removed solely by the Li flow. In this concept, Li is first pumped through a thin, high-velocity slot adjacent to the first wall to remove surface heat, and is then redirected to flow slowly through the poloidal channels in the main breeding zone. We show that the additional MHD pressure drop associated with the slotted-channel flow in the first wall is small, on the order of 0.1 MPa. The overall MHD pressure drop remains well below the upper design limit of 2 MPa, primarily because, in ST-E1, the blanket is located exclusively in the outboard region, where the magnetic field is relatively weak (approximately 3 T).