CHANGES IN MECHANICAL-PROPERTIES OF IRRADIATED ZIRCALOY-2 FUEL CLADDING DUE TO SHORT-TERM ANNEALING

Zirconium-lined fuel cladding tubes irradiated to 2.7x10(25) n/m(2) (E >1 MeV) in a BWR, which had experienced recrystallized annealing in th e final process in their manufacture, were heat treated at 500-700 deg rees C for 5-600 s to simulate short term dry-out. Tensile tests, hard ness measurements, fatigue tests and X-ray analyses were made on those specimens. The irradiation hardening in hardness at room temperature and ultimate tensile strength at 343 degrees C recovered to approximat ely 80% of that after heat treatment at 600-700 degrees C for less tha n 15 s. Fatigue life and half value width of X-ray analysis recovered to these of unirradiated cladding tube after annealing for 15 s at 600 degrees C. These recovery rates were faster than those on cold worked and stress relieved zirconium alloys. An equation to predict the rema ining fraction of hardening was proposed by using the regression analy sis on tensile strength and hardness values.