Armour materials for the ITER plasma facing components

The selection of the armour materials for the Plasma Facing Components (PFC s) of the international Thermonuclear Experimental Reactor (ITER) is a trad e-off between multiple requirements derived from the unique features of a b urning fusion plasma environment. The factors that affect the selection com e primarily from the requirements of plasma performance (e.g., minimise imp urity contamination in the cofined plasma), engineering integrity, componen t lifetime (e.g., withstand thermal stresses, acceptable erosion, etc.) and safety (minimise tritium and radioactive dust inventories). The current se lection in ITER is to use beryllium on the first-wall, upper baffle and on the port limiter surfaces, carbon fibre composites near the strike points o f the divertor vertical target and tungsten elsewhere in the divertor and l ower baffle modules. This paper provides the background for this selection vis-a-vis the operati ng parameters expected during normal and off-normal conditions. The reasons for the selection of the specific grades of armour materials are also desc ribed. The effects of the neutron irradiation on the properties of Be, W an d carbon fibre composites at the expected ITER conditions are briefly revie wed. Critical issues are discussed together with the necessary future R&D.