Revision of the EU helium cooled pebble bed blanket for DEMO

The helium cooled pebble bed (HCPB) blanket has been a European DEMO reference concept for nearly a decade. While the recent European power plant conceptual study (PPCS) confirmed that the HCPB built from the reduced-activation ferritic-martensitic steel Eurofer is an acceptable choice of a blanket relying only on limited technological extrapolation, it became clear that the HCPB needs a major review to adapt it to the PPCS plant lay-out: (i) the selection of an ITER-like modular blanket segmentation requires significant changes to the sector ("banana") segmentation of the previous DEMO regarding blanket box pressurization and front side access; (ii) the drive to higher blanket efficiency requires a review of the thermal lay-out; (iii) further integration of all in-vessel components within a reactor concept, using modern CAD tools, is needed for the technological credibility of the plant. In addition, the review was an opportunity to (iv) simplify the blanket by introducing modularity for the breeding zone; and, (v) introduce results from recent breeding blanket R&D. This paper presents the revised design and discusses design choices for the First Wall, the blanket box stiffened by a grid of plates, the back plate and for a modular HCPB breeding insert; at this stage of work the issue of reactor integration is neglected. Furthermore, analysis results are presented (j) on the neutronic behaviour of the blanket concept, using the plant lay-out of the PPCS; (jj) on the thermal-hydraulic lay-out; (jjj) on the structural-mechanical behaviour of the blanket under pressurization. The new design is an important prerequisite for defining DEMO relevant test blanket modules for ITER, and for future studies on DEMO and power reactors.