Thermal-hydraulic and structural design of the TITAN-I reversed-field-pinch fusion power core

Abstract

Thermal-hydraulic and structural design of the first wall, blanket, and shield of the deuterium-tritium fueled TITAN-I reversed-field-pinch (RFP) fusion reactor is presented. Taking advantage of the characteristic low toroidal magnetic field of an RFP reactor, liquid lithium is used as the primary coolant to remove the thermal energy at an elevated temperature, thereby realizing a high power conversion efficiency of 44%. The use of liquid lithium has also led to a self-cooled design of the fusion power core in which the primary coolant is also the tritium breeder. The structural material is the vanadium alloy, V3Ti1Si. Tubular coolant channels are used in the first wall/blanket and rectangular channels in the hot shield. These are laid along the much larger poloidal field to minimize magnetohydrodynamic (MHD) pressure drop. Although the neutron wall loading of 18.1 MW/m2 is high, resulting in a radiation heat flux on the first wall of 4.6 MW/m2, three aspects of the design have made the removal of the reactor power at high temperature possible. These are: (1) the use of small-diameter circular tubes as coolant channels in the first wall, (2) the use of high-velocity MHD turbulent flow in the first-wall coolant tubes, and (3) thermal separation of the first-wall and blanket/shield coolant circuits, thereby allowing different exit temperatures. The thermal-hydraulic design was optimized by a design code developed for this purpose. Detailed structural design was performed by the finite element code ANSYS. The coolant inlet temperature is 320°C, and the coolant exit temperatures for the first-wall and blanket/shield coolant circuits are 442°C and 700°C, respectively. Lithium flow velocity in the first-wall coolant tubes is 21.6 m/s, and is ≤ 50 cm/s in the blanket/shield coolant channels. The total pressure drop in the first-wall coolant circuit is 10 MPa and in the blanket coolant circuit it is 3 MPa. The pumping power for coolant circulation is less than 5% of the net electric output. The material stresses are well within the design limits. The TITAN-I design suggests the feasibility and advantage of liquid-metal cooling of high wall loading RFP fusion reactors.