High Availability Remote Maintenance Approach for the European DEMO Breeder Blanket options

An advanced blanket maintenance concept for DEMO was developed which implies vertical multimodule blanket segments (MMS) and a small number of vertical remote handling ports. As a common feature the MMS blanket consist of in regard to electromagnetic loads and thermal stresses reasonable small blanket modules which are mounted onto a vertical back-plate that contains the coolant channels and in case of liquid metal blankets also the breeder manifolds. For all considered blanket concepts (HCPB, HCLL and DCLL) a common remote handling strategy was developed which – similar to the ITER divertor cassette maintenance – is based on the consecutive exchange of a limited number of assembled functional units. In addition to vertical insertion tools located inside the transfer casks, remote transport machines are involved that are inserted into the divertor region after the removal of the divertor cassettes to transport the MMS in toroidal direction. The transport machines are equipped with sliding carriage systems for the movement of the inboard and outboard MMS in transverse radial/poloidal direction. In the final position the MMS are either bolted onto a permanent self-supporting closed ring shield structure or are mounted onto a frame which allows for relative thermal expansion of the MMS and the vacuum vessel. While the first option seems to be possible for the HCPB and HCLL concept the later could allow for integration of a new DCLL MMS blanket option.