Maintenance and radiation protection issues of the CREST reactor

A maintenance approach of the Compact Reversed Shear Tokamak (CREST) for high availability is proposed. Full sector removal through horizontal ports for easy maintenance is adopted in order to increase availability. Cask type sector removal machines are used to transfer the blanket/divertor sectors. Achievable availability is estimated with a maintenance period and its interval. The proposed maintenance approach allows, at least, the similar availability to that of the present nuclear plants. The estimated availability is acceptable from an economical viewpoint. Safety concerns related to the super-heated direct steam cycle are also examined. One of the unique concerns is due to nitrogen-16 production in the coolant. The super-heated steam must flow through the turbines within several 10 s after leaving the blanket. The requirements for shielding on the heat transfer systems are declared. Another concern is the confinement and recovery of tritium in the coolant, because a high temperature blanket may have a large tritium permeation rate. Water detritiation system proposed here would be able to control the tritium concentration in the coolant within an allowable range.