Parametric Analysis of Fuel Cooling in LOCA with ECCS Impairments in CANDU Reactors

摘要

The occurrence of a LOCA in a CANDU reactor is not expected to result in wide-spread fuel failures in the core. However, if an instantaneous guillotine break of a large diameter pipe is postulated in certain locations of the heat transport system, low channel flow in one core pass and the associated power pulse result in the prediction of a transient increase in fuel temperatures. Under these conditions some limited fuel sheath failures cannot be precluded, resulting in the release of the "free" inventory of fission products from the failed fuel. Even for this idealized event, fuel cooling during blowdown of the heat transport system is effective to both limit and reduce the fuel temperatures during the early stages of the accident. This idealized event bounds the consequences of all LOCAs but does not represent flow conditions following a physically realistic pipe rupture event (e.g. leak before break).