Status of the DEMO blanket attachment system and remaining challenges

Abstract

The DEMO blanket attachment concept is challenging due to several factors: the harsh radiation environment, the thermal expansion, the electro-magnetic loads, the remote maintenance feasibility, and the accurate control of the alignment of the breeding blanket first wall during operation. There are two inboard and three outboard blanket segments per vacuum vessel sector to be installed and extracted by remotely controlled tools through a single upper vertical port. The design of the fixations of the blanket segments to the VV complies with the strategy to avoid the need for front side access for engagement and release. The attachment system has been designed for the numerous critical load cases, including normal operation, dwell between pulses, plasma disruptions, fast discharge of the magnet coils, and accidental conditions such as loss of blanket coolant. At the same time the attachments must guarantee the stresses in the blanket segments not to exceed limits.This paper introduces the attachment concept and describes the finite element model that has been built to assess the blanket attachment system. The model represents one sector of the DEMO machine. The results focus on the reaction forces transmitted at individual attachment locations to define these interfaces and guide the design of the individual supports.