Neutron Activation in First-Wall Materials for Advanced-Fuel Fusion Reactors

Three types of fusion reactors, based on DT, DD and DHe fuel cycles, are compared from the first wall neutron-induced radioactivity point of view. Some of the definitions of low-activity, based on hands-on recycling, remote recycling, "U.S." shallow land burial and deep geological confinement waste management criteria, are discussed. A three-classes rank of low-activity is proposed. The analysis of the induced radioactivity in first-wall steels shows that the long-term activity remains at high levels in DD and DHe cases too. DD and DT first-wall steels can be classified in none of the above-mentioned low-activity classes. Neutron induced radioactivity in some of the main constituting elements for the first-wall varies, when turning from DT to DD or DHe irradiation conditions. This depends on the different ways by which the long-lived radioactive nuclides are produced. Materials selection and low-activation alloys development, in order to minimize activity, will be necessary also for the first walls of fusion reactors based on advanced fuel cycle