A water cooled BOT blanket for the NET-ITER reactor

The predesign of a poloidally water-cooled γ-LiAlO₂ blanket with breeder out-of-tube (BOT) has been put forward with the goals of reaching good shielding and TBR (tritium breeding ratio) capabilities, having mechanical simplicity, and using known technologies. Initially, a shielding blanket with reduced thickness (Lower Performance Option, LPO) for the NET-1 (Next European Torus-1) reactor was developed. The concept was then adapted to an enhanced reactor relevance for the ITER (International Thermonuclear Experimental Reactor) in a solution where beryllium multiplier was added and the available thickness increased (higher performance option, HPO). For both versions, an estimation of TBR and of shielding effectiveness is given. The thermal and mechanical analyses of the cooling system and the supporting structure are presented together with considerations on safety. In particular, the focus was on searching for a reliable way of realizing a thermal barrier between water (10 bar, 60-110°C) and breeder (450-800°C) and on designing a safe double-pipe cooling system which incorporates the above-mentioned gap. The chosen solution has stagnant helium acting as a thermal insulator and as a water-leakage monitor. Two different ways of inserting beryllium in the enhanced solution are briefly discussed