Activation analysis for the Ignitor tokamak

Abstract

The purpose of the Ignitor experiment is to produce DT plasma regimes where ignition can take place. From the neutronics point of view, after a first period of machine set up and tuning in aneutronic operation, a second phase of 2.5 MeV neutron production with pure deuterium plasmas at increasing density is anticipated. After that, a transition phase to increasing percentage of tritium will be followed by several years of operations with 50% of tritium leading to short but intense 14-MeV neutron emission. To deal with the concerns due to the strong neutron emission, a detailed description of the actual Ignitor machine is implemented in the MCNP-4B Monte Carlo code to calculate the neutron fluxes in all machine components, taking in account the streaming through the ports. These fluxes are then used as input for the FISPACT-97 code for the analysis of the activation at the end of life and at intermediate times for safety assessment purposes. The resulting dose rate outside the device is also studied. The results point out that remote handling is needed for repair/maintenance of inner components following the DD operations, and that the access in the hall near the device could be restricted from the beginning of DT operations. The requirements on additional shield are discussed.