Nuclear heat analysis for the ITER Vacuum Vessel regular sector

Abstract The assessment of nuclear loads to the ITER Vacuum Vessel is critical in ensuring the safe and reliable operation of the machine. Radiation transport simulations were performed to compute energy deposition rates and other nuclear responses in the Vacuum Vessel due to plasma neutrons by means of MCNP6.1. Weight windows generated by ADVANTG code were used in order to accelerate convergence of nuclear heat response tallies at the required locations, to optimize computer resources and to achieve meaningful statistical errors within a reasonable timescale. The basis of the modelling was the most detailed and up-to-date ITER reference neutronics model of regular sector, so-called “C-model”, provided with specific VV regular sector components, such as the Triangular Support. Best estimates of integral heating were obtained, and corrections were applied to account for systematic errors of modelling and random uncertainties. Consideration of other contributions to the integral heat was also made, leading to an upper bound estimate of integral heating of 20.9 MW ± 2.3 MW. A complete and detailed set of 3D nuclear heat deposition maps were also produced to be used as input to subsequent thermal-hydraulics and thermal-mechanics analyses.