Assessment of first wall lifetime in D-3He and D-T reactors with impact on reactor availability

The neutron yield in a D-{sup 3}He reactor is much lower than that in a D-T reactor of equivalent power. Therefore, the rate of neutron damage and gas production in the first wall of D-{sup 3}He reactors is lower by more than an order of magnitude. Whereas different structural materials proposed for use in commercial fusion reactors will last the reactor lifetime of 30 full power years in a D-{sup 3}He reactor, frequent replacement of the first wall and blanket will be required during the lifetime of a D-T power reactor. The blanket modules may require 30 replacements depending on the material used and the maximum allowable damage level. The down time required for replacement of the first wall and blanket in a D-T reactor will impact the reactor availability and consequently the cost of electricity. It appears that a D-{sup 3}He reactor should have a 10% advantage in availability over a D-T reactor.