Comparisons Between ELOCA Code Calculations and CANDU Fuel Behaviour Under LOCA Conditions

Abstract

Six CANDU^* type fuel elements (Zircaloy-sheathed, UO₂ fuel) have been subjected in three in-reactor experiments to transient conditions similar to a large break loss-of-coolant accident (LOCA) in a CANDU reactor to maximum sheath temperatures of about 1273 K. Two of these experiments involved single fuel elements and were conducted at Chalk River Nuclear Laboratories in the X-2 loop of the NRX reactor. The remaining four elements experienced a single transient in the Power Burst Facility at Idaho National Engineering Laboratory.

Comparisons are presented between data from these three experiments and calculations by ELOCA, a computer code for fuel performance during transient conditions. Several parameters were considered, including fuel sheath strain, internal element gas pressure, the mechanisms and timing of fuel element failure, fuel centreline temperature, sheath microstructure, and thicknesses of zirconia and oxygen-stabilized alpha-Zr layers on the sheaths. ELOCA calculations are shown to be in good agreement with the data.

Some of the work described here was jointly funded by Atomic Energy of Canada Limited and Ontario Hydro, a Canadian utility, through the co-operative research and development program, CANDEV.