THERMOCYCLIC RECOVERY AND DAMAGE ACCUMULATION OF IRRADIATED AUSTENITIC STRUCTURAL-MATERIALS

Thermocyclic behaviour of austenitic materials: 16%Cr-11%Ni, 16%Cr-15% Ni, 20%Cr-45%Ni has been investigated after being irradiated in WWR an d BOR-60 reactors at a temperature of about 300 degrees C up to fluenc es of approximately 10(25) and 10(26) n/m(2). Strength and strain char acteristics of irradiated materials are recovered during thermocycling (50-300 degrees C) and reached initial unirradiated values. Simultane ously to the recovery processes an intensive accumulation of thermocyc lic damage takes place with early material fracture. Thermal fatigue f ailure has shown an intergranular mode. It is assumed that two opposit e processes take place during thermocycling: recovery in grain volume and the accumulation of damage along grain boundaries, which do not co mpensate each other.