Neutronic design optimization of ITER TBM port#2 bio-shield plug

Abstract

Indian Lead Lithium Ceramic Breeder (LLCB) Test Blanket Module (TBM) will be tested in one-half of the equatorial port #02 of ITER. The TBM systems demand the opening through bulk bio-shield boundary for installation & removal of TBMs from the port. In order to serve the requirement of TBM system, a Bio-Shield Plug (BSP) is placed at biological shielding location of the equatorial port. The neutronic design of BSP is important because it serves the purpose of biological shield boundary of ITER port and has to limit the ITER occupational radiation exposure behind the bio-shield up to 10 μSv/hr 1 day after shutdown. The BSP has to be removed and reinstalled during the removal and installation of TBM Sets from the port. The design of BSP should be compatible with TBM set installation & removal plans. It should also allow the TBMs coolant and instruments pipes to pass through. The shielding capability of BSP has to be adequate enough to limit the exposure. The engineering constraints like the feasibility of BSP removal/reinstallation & passage for pipes affect the shielding capability of BSP. The scope of this paper is to investigate the limitation of existing BSP and assess the better options for shielding capability improvement. The shielding capability of advanced shielding materials like B4C and Ferro-boron for BSP application is also assessed. The neutronic analyses have been performed using the MCNP radiation transport code and FENDL-2.1 nuclear cross section data library. The Activation code FISPACT-2007 has been employed to estimate the contact dose rates. The outcome suggests that B4C and Ferro-boron would be better candidate materials for the bio-shield plug of TBM port.