EFFECT OF ALPHA-INCIDENT-ANGLE AND POLOIDAL-ANGLE DISTRIBUTIONS ON BLISTER-INDUCED 1ST-WALL EROSION

The incident velocity distribution of high-energy alpha particles bombarding the first wall of an axisymmetric tokamak is evaluated as a function of poloidal angle (γ). The resulting helium concentration profile as a function of the poloidal angle and the implant depth is calculated for a typical Experimental Power Reactor (EPR) design. The critical helium concentration for blistering is first exceeded at θ ~55°. Peak concentrations are reduced somewhat through continuous D-T sputtering which, dependent on θ, reduces the blister skin thicknesses. The blistering-induced impurity level is found to increase drastically (≲ < 50%), relative to sputtering-induced impurities, at periodic intervals corresponding to ~4000 hours operation when each generation of blister begins to exfoliate. © 1979.