Bulk tungsten in the JET divertor: Potential influence of the exhaustion of ductility and grain growth on the lifetime

Thermal fatigue for impact factors of 11-24 MW m−2 s0.5 is investigated with a Manson-Coffin model; tungsten properties come from production samples. Recrystallization is studied in metallographic cuts of tungsten lamellae identical to those installed in the torus which were exposed in the MARION facility to JET relevant heat fluxes for >300 pulses (Pdep ⩽ 9 MW/m2, angle of attack 6°). The calculations suggest that the number of high temperature cycles should be limited with appropriate budgeting, especially if the grain growth degrades material properties. Values for JET range from 150 to thousands of pulses depending on the temperatures reached.