Post-Defect Deterioration of CANDU Fuel: What Have We Learned?

Abstract

Post-defect deterioration is an important consideration for CANDU users who need to decide when to remove fuel defects from the core. Previous work on this subject showed that defective fuel is sufficiently stable while operating within the high power envelopes of current CANDUs and will not pose risk to refuelling operations. For defective elements operating below about 1000 kw/m2, secondary hydride damage of the Zircaloy cladding occurs at burnups above 40 MWh/kgU. At higher heat fluxes, hydriding can be present at lower burnups. The primary hole size also influences deterioration rates; fuel elements with small holes hydride earlier than ones with large holes.