Nuclear Analysis for the Upper Ports in the NB Cell in ITER

In International Thermonuclear Experimental Reactor (ITER), 14 upper ports (UPs) are allocated for diagnostic systems mounted into the port plug. The upper port plug (UPP) consists of the port plug (PP) structure, diagnostic shield module (DSM), and diagnostic first wall (DFW). One of the main functions of the UPP is to provide the neutron shielding to reduce the radiation level in port interspace and the nuclear loads on the superconducting coils. In this work, the nuclear analysis of the UPs #4-#7 that are located in the neutral beam cell is presented. Two configurations have been analyzed with Monte Carlo N-Particle (MCNP) code: the generic UPP design of full shielding (22 tons) and a light version (18 tons) with reduced shielding. The UPP MCNP models have been developed on the basis of latest design files and integrated in a 120 degrees neutral beam injection (NBI) sector extracted from Elite. Calculations have been performed to evaluate the neutron flux at the port interspace, the nuclear heating of the PP and toroidal field (TF)/poloidal field (PF) coils (TFC/PFC), the neutron flux, and damage for the electrical feedthrough installed on the closure plate with D1SUNED v3.1.4 code. The impact of crosstalk with NBI and neighboring ports has been assessed for neutron flux and shutdown dose rate (SDDR) at 12 days after shutdown. The results of this analysis showed that the impact of the additional shielding of the 22 tons model compared to the 18 tons model is small and limited in space: the fluxes and damage at the electrical feedthrough are about 40%-50% smaller with additional shielding. Analyses enhanced a large radiation crosstalk with NBI ports and a large streaming through the gaps of UPPs.