The CANDU-6 nuclear reactor is a 600-MW(elec-tric) channel reactor in which natural uranium fuel is located in channels and surrounded by three separate water systems containing a total of ∼900 000 kg of water. Its four steam generators contain an additional 129000 kg of water. A recent study of a dominant core melt category indicates that this abundance of water effectively retards the melt progression and mitigates accident consequences. The inventory of all three water systems plus that of the steam generators must boil off before the core’s calandria vessel is breached. The steam produced from this boiloff vents to the containment atmosphere where it enhances passive heat removal on surfaces, promotes rapid aerosol settling by condensation on airborne particles, and reduces the concentration and flammability of the hydrogen generated. Breach of the calandria vessel allows molten core to enter a thick-walled concrete calandria vault. The resulting core/concrete reaction penetrates the calandria vault floor ∼2½ days after the beginning of the accident. Core debris, well diluted by decomposition products, then falls into an estimated 2 000 000 kg of water in the reactor basement. This water quenches and disperses the debris and essentially terminates the event sequence. Continuing decay heat is dissipated by minor steaming and by heat transfer through the basement floor and walls into the surrounding bedrock.