NON LINEAR THERMAL TRANSIENT ANALYSIS OF A DIVERTOR PLATE FOR ITER

The ITER divertor plate option considered consists of an armour of graphite tiles, each one crossed by two tubes of the water cooling system; the study takes into account many different thicknesses, three materials for the graphite and two for the tubes. The investigation is related to conditions with plasma burning continuation or with plasma shut down; the undercooling transients involve LOCA's in one single tube or in both tubes, in order to evaluate the efficiency for safety of a design with two independent cooling circuits. The results show that for cases with plasma burning continuation, a double cooling system could be relevant for safety only if Pyrolitic Graphite (PG) armour and Mo-Re tubes are considered; for cases with plasma shut down also the SEP-Carb with Mo-Re tubes solution could be effective, but the results are strongly dependent on the plasma shut down transient. This key point, not known at present, must be assessed before to go on with the analyses.