COMPETITION OF BULK TRAPPING AND SURFACE EROSION IN THE KINETICS OF TRITIUM INVENTORY AND PERMEATION IN PLASMA PROTECTION METALS

A simplified transient model is presented to describe the migration of implanted tritium in the presence of trap sites across the bulk of me tallic substrates whose thickness is decreasing with time due to erosi on. The subject is relevant for quantifying the tritium inventory in - and permeation through - plasma facing armours in the next generation of D-T fuelled tokamak devices (i.e., the International Thermonuclear Experimental Reactor). This paper describes the equations of the phys ical model and the main assumptions used to simplify the complex analy sis, and surveys the influence of several parameters such as the impla ntation flux, the erosion rate, the armour temperature, the armour thi ckness, the density and trapping energy of neutron-induced traps, etc. , which are all expected to play a key role in the phenomena investiga ted. The examples presented to show the applicability of the model inc lude the results of a study performed for beryllium armours exposed to heat and particle loads similar to those expected on the ITER diverto r plasma facing components and comparison is made with cases where ero sion does not play any role.