Lifetime and thermal-structural performance of various first wall concepts and implications of creep-fatigue for design and licensing

Performance and lifetime estimation calculations of two fusion power plant first wall concepts in DEMO-relevant conditions are presented and conclusions are drawn. The limitations that arise from fatigue, thermal and irradiation creep phenomena, and the implications for successful design, licensing and power plant operation, are discussed. Calculation results show that the zero-fatigue lifetime (creep damage only) is 2.52 years for the helium and 2.82 years for the water cooled concepts respectively for a wall load of 2.4 MW m−2, with the bulk of damage occuring during the power-on period. At higher temperatures, the structure becomes more susceptible to fatigue and even a small number of large duration events are capable of reducing lifetime significantly; in the helium cooled design lifetime reduces from 2.52 years (zero-fatigue) to ∼1.45 years. In general, all of the damage mechanisms examined exhibit a dampened behaviour with decreasing temperature. Lifetime improvement is possible if the time to failure at the full power-on stress level can be extended.