An Assessment of the Base Blanket for Iter

Ideally, the ITER base blanket would provide the necessary tritium for the reactor to be self-sufficient during operation, while having minimal impact on the overall reactor cost, reliability and safety. A solid breeder blanket has been developed in the CDA phase in an attempt to achieve such objectives. The reference solid breeder base blanket configurations at the end of the CDA phase has many attractive features such as a tritium breeding ratio (TBR) of 0.8-0.9 and a reasonably low tritium inventory . However, some concerns regarding the risk, cost and benefit of the base blanket have been raised. These include uncertainties associated with the solid breeder thermal conwol and the potentially high cost of the amount of Be used to achieve high TBR and to provide the necessary thermal barrier between the high temperature solid breeder and low temperature coolant. This work addresses these concerns. The basis for the selection of a breeding blanket is first discussed in light of the incremental risk, cost and benefits relative to a non-breeding blanket. Key issues associated with the CDA breeding blanket configurations are then analyzed. Finally, alternative schemes that could enhance the attractiveness and flexibility of a breeding blanket are explored. Considerations in ITER Blanket Selection A blanket will be required for ITER. It will need to perform heat removal functions as well as neutron capture functions. The question is whether it will also perform tritium breeding functions. Selection of an ITER breeding blanket over a non-breeding blanket has to be based on considerations of incremental risks, costs and benefits. Major issues in this area are associated with reliability and safety. A breeding blanket will require additional regions for the breeder and multiplier as well as a purge system, which would result in more complex design and assembly requirements. However, it is not clear that a breeding blanket would have a significantly lower reliability than a non-breeding blanket. For instance, Figures 1 and 2 show examples of a breeding blanket configuration designed as part of the CDA effort [ 11, and of a non-breeding blanket configuration from a pre-design study for NET [2]. Both of these configurations use a layered design. From these example configurations, there seems to be a comparable number of welds and joints in contact with the coolant in the higher fluence regions. Furthermore, failure that would require reactor shutdown and component replacement and, thus, which could have a major impact on the overall reactor availability are mostly concemed with: coolant channel rupture or Figure 1. Cross-sectional view of a multi-layered ceramic breeder blanket design configuration developed during the ITER CDA phase