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 p lant first wall concepts in DEMO-relevant conditions are presented and conclusions are drawn. The limitations that arise from fatigue, therm al and irradiation creep phenomena, and the implications for successfu l design, licensing and power plant operation, are discussed. Calculat ion 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 concept s respectively for a wall load of 2.4 MW m(-2), with the bulk of damag e occuring during the power-on period. At higher temperatures, the str ucture 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-fat igue) to similar to 1.45 years. In general, all of the damage mechanis ms examined exhibit a dampened behaviour with decreasing temperature. Lifetime improvement is possible if the time to failure at the full po wer-on stress level can be extended. (C) 1998 Elsevier Science S.A. Al l rights reserved.