Scoping Nuclear Analyses of Shielding Options and Shutdown Dose Rate Contributions in ITER TBSs

One of the advances in the test blanket module program within the ITER project in the last few years concerned the evolution of the pipe forest (PF) and bioshield plug (BP) designs. In support of the design phase, nuclear analyses to assess several responses in the fusion neutronics environment inside the port interspace (PI) with the existence of the evolved PF and BP are deemed essential. Nuclear analyses were commenced using the new PF and BP with developing the neutronics models and performing preliminary assessment of the radiation fields and shutdown dose rate (SDDR) in the PI. In this paper, the results of a full suite of nuclear analyses are discussed, which covers more configurations and radiation sources, in two plasma operational modes: on and off. For the plasma-on mode, different shielding options were examined. The results show a clear benefit of combining the installation of shielding panels on the PF enclosure with those in the BP “dogleg,” through which the pipes penetrate to the port cell area. For the plasma-off mode, the SDDR was assessed from different sources: activated components and residual LiPb layers in pipes after drainage. As maintenance operations are foreseen during the lifetime of the facility, the SDDR was also assessed for access conditions, open BP doors, and transport conditions, with PF extracted in the gallery.