At present when notable progress in plasma physics has been obtained, pract
ical energy utilization from fusion reactors is determined by the state of
material science problems. The last includes not only the routine problems
of nuclear engineering but also a number of entirely new problems connected
with extreme conditions of materials operation - irradiation environment,
hydrogenation, thermocycling, etc. Limited data suggest that the combined e
ffect of these factors is more severe than any one of them alone. To study
the possible significance of in-service synergistic phenomena, we studied h
ydrogen-irradiated steel interaction during alternating hydrogenation and h
eat treatment (annealing). These studies suggest the existence of residual
(unrecovered by annealing) degradation effects caused by hydrogen-irradiate
d steel interaction during alternating hydrogenation and annealing. We prop
ose that this phenomenon must be taken into account when in-service propert
ies of the candidate structural materials are analyzed. (C) 2000 Elsevier S
cience B.V. All rights reserved.