Assessment of critical heat flux margins on tungsten monoblocks of the ITER divertor vertical targets

Recent Critical Heat Flux (CHF) experimental results in the range of 40 MW/m(2) obtained on small scale tungsten (W) monoblock mock-ups with reduced minimum W thickness above the coolant tube compared to the nominal 6 mm planned for ITER are presented. The CHF margin during ITER operations is further assessed, taking into account design and manufacturing aspects, demonstrating that an absorbed top surface heat flux of 20 MW/m(2) should not be exceeded during ITER operations if the factor 1.4 margin to CHF, which must be respected for ITER monoblocks, is to be preserved.