Thermal-hydraulic and structural design for the lithium-cooled TITAN-I reversed-feeld-pinch reactor

Abstract

A thermal-hydraulic and structural design of the first wall and blanket for the 18 MW/m 2 neutron wall-loading TITAN reversed-field-pinch fusion reactor is presented. The primary coolant is liquid lithium and the structural material is the vanadium alloy, V-3Ti-1Si. Various design limits, which take the operational environment into consideration, for this vanadium alloy for the first wall and blanket are discussed. The first wall is made of small-diameter tubes. The blanket coolant channels are a combination of tubular, square, and rectangular channels. The first-wall and blanket coolant circuits are separate, allowing different coolant exit temperatures. The coolant channels are aligned with the larger poloidal magnetic field to reduce magnetohydrodynamic (MHD) pressure drops. At the design heat flux of 4.6 MW/m 2 on the first wall, MHD turbulent-flow heat transfer is used. Both the separation of the coolant circuits and the use of MHD turbulent-flow heat transfer substantially increase the heat flux limit on the first wall. These are favorable for high-power-density fusion reactors. The inlet temperature of lithium is 320 °C and the exit temperatures are 440 °C and 700 °C for the first wall and blanket, respectively. The pressure drop in the first wall circuit is 10 MPa and is less than 3 MPa for the blanket circuit. The pumping power is less than 5% of electric output. The maximum structure temperature is less than 750 °C and the material stresses are shown to be within the allowable limits. One-dimensional thermal and stress analyses are adequate for the thermal-hydraulic and structural design for TITAN-I. This is verified by two-dimensional, finite element analysis. The use of liquid lithium as the coolant and vanadium alloy as the structural material enables the removal of the reactor thermal energy at high temperature, which has resulted in a gross thermal efficiency of 44%.