Improved structural strength and lifetime of monoblock divertor targets by using doped tungsten alloys under cyclic high heat flux loading

The divertor is one of the most important components of a fusion reactor, which performs the function of the removal of waste material from fusion plasma. Because the divertor is subjected to cyclic high heat flux loading up to about 20MWm(-2) induced by the plasma, the plasma facing material of the divertor should exhibit good thermo-mechanical properties. In this work, the possibility of improving the structural strength and the lifetime of fusion reactor divertors by using K-doped W and K-doped W-3% Re as plasma facing material instead of ordinary pure W was evaluated by thermo-mechanical finite element analysis (FEA). These materials have been developed for divertor applications in Japan and show higher recrystallization temperature and strength than pure W. The results of the present study indicated that K-doped W and K-doped W-3% Re render lower applied strain to the divertor and longer fatigue life of the plasma facing material. The evaluation results regarding the macro-crack formation life based on the FEA analyses indicated the possibility of an extension of the fatigue life by using K-doped W and K-doped W-3% Re.