EXAMINATION OF IRRADIATED EBWR CORE-1 FUEL ELEMENTS

Abstract

Two fuel elements were removed from the Experimental Boiling Water Reactor and examined in a hot cell. The elements had maximum burn-ups of 0.11 and 0.39 at.%. Both were disassembled and sampled for the evaluation of the effects of in-pile operation and radiation damage to the fuel. The fuel elements were in gcod condition with no ruptured.cladding, core-clad nonbonds, or excessive fuel-plate swelling or warpage. Thin samples cut from the fuel plates in element ET-51 warped and cracked, suggesting a relieving of locked-in stresses and indicating that after 0.39 at.% burn-up the fuel cores were hard, brittle, and highly stressed. The rate of fuel-plate volume increase owing to the burn-up of uranium was 6 to 7% DELTA V per at.% burn-up. Hydrogen was picked up by the fuel plates under reactor operating conditions with the probable forraation of isolated areas of small announts of zirconiura hydride. Annealing studies on sections of fuel plate at 500 and 550 deg C indicated bulk volume increases of 1 to 2% and 5 to 10%, respectively, after 500 hr. A 600 deg C anneal resulted in a bulk volume increase of 17% after 45 hr. (auth)