Combination of a self-cooled liquid metal breeder blanket with a gas turbine power conversion system

Abstract

Self-cooled liquid metal breeder blankets have a high potential to meet the overall goal of fusion research to develop an economically and environmentally attractive energy source. They offer the possibility to design mechanically simple blanket segments, employ a high-temperature, low-pressure coolant, allow for a high power density, and as consequences of these, achieve high efficiency and availability with relatively low cost. A major concern with self-cooled blankets is the high chemical reactivity of lithium with water. A secondary heat transport loop is usually required between the primary lithium loop and the steam/water loop of the Rankine cycle in the power conversion. The potential for liquid metal–water reactions is eliminated if the Rankine cycle is replaced by a Brayton cycle, employing a closed cycle helium gas turbine. This paper describes a system combining a self-cooled blanket with a closed cycle helium gas turbine in order to combine the advantages of self-cooled blankets with the ones of high temperature gas-cooled concepts. Scoping calculations assuming a maximum lithium temperature of 670°C and a maximum helium pressure of 18MPa have shown that the gas turbine cycle results in about the same overall thermal efficiency as an advanced Rankine cycle (46%).