Degraded Cooling in a CANDU Reactor

Loss-of-coolant accident (LOCA) analysis for a Canada Deuterium Uranium (CANDU) reactor considers a wide range of postulated break sizes and locations in the heat transport piping. Coincident failure of the emergency coolant injection system to operate on demand must also be considered. The unique features of the CANDU core and heat transport system, and how these features affect the response of the system to a LOCA, are described. The possible range of behavior of the fuel and fuel channels following a LOCA is discussed in terms of the maximum fuel temperatures that could occur and also in terms of the potential for breaching the core pressure boundary (in the case of CANDU, this boundary comprises a large number of horizontal pressure tubes, each containing horizontal fuel bundles). It is concluded that fuel temperatures remain well below the UO₂ melting temperatures and that the integrity of the pressure tubes is maintained for all postulated LOCAs.