The influence of key operation parameters and material properties on the quantification of tritium inventory and permeation in the plasma facing components of ITER

Abstract

This paper identifies the relevant uncertainty parameters affecting the tritium inventory and permeation estimates for three candidate ITER plasma facing materials (i.e., Be, presently the only material under consideration for the first wall and start-up limiter; Be and W for the baffle; and Be, W, and CFC for the divertor). An analysis was conducted to quantify the changes of the tritium inventory and permeation resulting from the varying parameters with the highest uncertainty. It includes the effects of plasma physics parameters (i.e., heat and particle fluxes, net-erosin rate), material properties (i.e., diffusion coefficient, rate of surface recombination and the possible presence of surface oxide layers), nuclear radiation (i.e., density of n- induced traps), design and operational lifetime (i.e., type and thickness of plasma facing components materials and replacement schedule for the sacrificial components exposed to high particle and heat fluxes). Based on the results, the implications on the design are discussed and priorities are determined for the R&D needed to reduce the uncertainties.