Neutron irradiation effects on tungsten materials

To understand the irradiation response of tungsten in the ITER and a DEMO-like reactor, irradiation effects on microstructure development, hardening and electrical resistivity of pure W and W-Re-Os alloys are studied using fission reactor irradiation up to about 1-1.5 dpa in the temperature range from 400 to 800 °C. Microstructural development and hardening behavior are summarized here based on the irradiation data. Voids are the major damage structure in pure W, but Re addition clearly suppressed void formation. Irradiation hardening was also suppressed in lower Re content alloys. The hardening was caused by irradiation-induced precipitation of WRe (σ-phase) and WRe3 (χ-phase), and the hardening behavior strongly depended on the neutron spectrum of the irradiation field. On the basis of these results, a damage structure development prediction map in fusion devices is suggested.