Modelling hydrogen transport in ITER divertor
Résumé
Hydrogen isotopes transport in tokamaks is a crucial issue for several reasons, especially in the divertor exposed to the highest heat and particles fluxes. First, the total inventory of radioactive material trapped in the reactor must be limited to a certain amount (in ITER, the limit of tritium in the vacuum vessel is 1 kg). Secondly, outgassing of hydrogen from the monoblocks composing the divertor and from the tokamak first wall can reduce the plasma performances. Finally, the lifespan of plasma facing components can be reduced due to hydrogen-induced
damage.
A new method coupling 2D Finite Element monoblock simulations of H transport [3] to plasma codes such as SOLPS [4] is presented. This work investigates the influence of the divertor neutral pressure on the full divertor hydrogenic inventory. It is shown that the peak heat flux (and therefore the peak temperature) decreases with the neutral pressure. The H inventory is maximum in the strike points neighbourhood and a local minimum is observed at the strike points.
Even considering very conservative assumptions (eg. s of continuous exposure), the total divertor inventory of hydrogen isotopes is around 14 g which is much lower than the ITER safety limit. Moreover, this divertor inventory only varies slightly with the divertor neutral pressure (from 12 g to 14 g)