Current Status of Study for Severe Accidents in the SFPs of CANDU Plants

SFP (Spent Fuel Pool) accidents that result in fuel degradation and, consequently radioactive release are highly unlikely. The SFP accident progression is slower in comparison to that of reactor core accidents, typically lasting days before any significant consequences occur. This slow progression enables operators to intervene and arrest the accident in its early stages, before beginning of fuel degradation and radioactive release. In CANDU SFPs, thermo-hydraulic phenomena are expected to be significantly different from those in PWR SFPs, due to the open rack structure with horizontally aligned fuel elements. The purpose of the paper is to discuss the current status of study for severe accidents in the SFPs of CANDU plants. Unlike LWR SFP, the CANDU SFP is significantly different from the reactor core in terms of the conditions and the fuel configuration. The former is open racks type, while the latter is horizontal pressure tubes type. This difference made it difficult that CANDU SFP accident would be analyzed by the existing severe accident codes. That is why there are not many accident analyses available for CANDU SFPs and why it is hard to find new findings for CANDU SFP accident as yet. Therefore, it is recommended that a severe-accident analysis tool for CANDU SFPs be developed.