Tritium self-sufficiency time and inventory evolution for solid-type breeding blanket materials for DEMO

Abstract

One of the primary functions of a fusion blanket is to generate enough tritium to make a fusion power plant (FPP) self-sufficient. To ensure that there is satisfactory tritium production in a real plant the tritium breeding ratio (TBR) in the blanket must be greater than 1+M, where M is the breeding margin. For solid-type blanket designs, the initial TBR must be significantly higher than 1+M, since the blanket TBR will be reduced over time as the lithium fuel is consumed. The rate of TBR reduction will impact on the overall blanket self-sufficiency time, the time in which the net tritium inventory of the system is positive.DEMO relevant blanket materials, Li4SiO4 and Li2TiO3, are investigated by computational simulation using radiation transport tools coupled with time-dependent inventory calculations. The results include tritium inventory assessments and depletion of breeding materials over time, which enable self-sufficiency times and maximum surplus tritium inventories to be evaluated, which are essential quantities to determine to allow one to design a credible FPP using solid-type breeding material concepts. The blanket concepts investigated show self-sufficiency times of several years in some cases and maximum surplus inventories of up to a few tens of kg.