11. MECHANICAL STRENGTH OF THICK Be

JET under a contract with the European Home Team and in co-operation with industry, is carrying out a programme to support development of beryllium (Be) divertor components for ITER. The basis for this programme is the existing experience on the brazing of thin (1.5 to 3") Be cladding to CuCrZr hypervapotrons using a silver based alloy (Incusil 'ABA), which demonstrated critical heat fluxes of up to 18 MW/m2, and good low power high cycle performance. This paper reports on the mechanical strength of thick (5, 7.5 and 10") Be/CuCrZr braze samples showing the feasibility of brazing thick clads. Also reported are the results of testing of lOmm thick tiles brazed to a hypervapotron. These tests resulted in melting of the tile surface at power levels of 20MW/m2 without complete delamination of the joint. The results of these tests have allowed the European Home Team and European ITER JCT to benchmark their one and two dimensional models. Another important aspect of the JET investigations is the development of a silver free braze which is being developed in collaboration with industry and producing interesting results with shear strengths almost comparable with Incusil ('ABA') with failure occurring in the braze/CuCrZr interface.