The DEMO Helium Cooled Lithium Lead 'advanced-plus' Breeding Blanket: Design improvement and FEM studies

In the framework of the European 'HORIZON 2020' research program, the EUROfusion Consortium develops a design of a fusion demonstrator (DEMO). CEA-Saclay, with the support of Wigner-CR and IPP-CR, is in charge of one of the four Breeding Blanket (BB) concepts investigated in Europe for DEMO: the Helium Cooled Lithium Lead (HCLL) BB. The BB directly surrounding the plasma is a major component ensuring tritium self-sufficiency, shielding against neutrons from D-T plasmas and heat extraction for electricity conversion. In this article, the equatorial outboard module of the HCLL reference DEMO BB ('advanced-plus' BB) concept is studied regarding thermal and mechanical behavior during normal and accidental conditions that led to modify the design and enhance the performances. A numerical approach based on the Finite Element Method (FEM) is followed. The methodology established, the assumptions done as well as the results obtained in each case are reported and critically analysed, scrutinizing some open issues on this 'advanced-plus' reference concept. (authors)