Development of the EU water-cooled Pb-17Li blanket

Abstract

The reference concept of the EU water-cooled Pb-17Li DEMO blanket is essentially formed by a directly-cooled steel box having the function of Pb-17Li container and by a double-wall U-tube bundle, immersed in the liquid metal, in which the pressurised water-coolant flows. The structural material is martensitic steel. All blanket performances satisfy DEMO requirements, such as tritium breeding self-sufficiency, capability of the box-structures to withstand water-coolant pressure under faulted conditions, limitation of the Pb-17Li/steel interface temperature to 480°C, power conversion efficiency of about 35%, and acceptable increase of temperature in case of out-of-vessel LOCA. A preliminary design of the test module and of the associated circuit components to be tested in ITER has been performed taking into account ITER specifications for test ports and ITER pulsed working conditions. Test-module DEMO-relevance has been one of the leading criteria for the module design. Preliminary module manufacturing sequences have been defined. The paper recalls the associated R and D activities which have to be finalised prior to the ITER testing and mainly involve tritium permeation barrier development, tritium extraction from Pb-17Li, advanced manufacturing techniques, definition of water/Pb-17Li interaction counter-measures, and Li-concentration control techniques.