Process for identifying accident scenarios for licensing of CANDU 3

Nuclear regulatory and design organizations throughout the world have a tradition of looking at the response of nuclear power plants to a set of design-basis accidents. Ensuring that doses to members of the public and the operating staff are limited for these events has been one important way of making sure that the public is protected. Other safety initiatives include accident prevention and mitigation by quality design, fabrication and construction, inspection, maintenance and testing of components, careful site selection, design of an appropriate operator interface, and operator training. Pickering generating station A is Ontario Hydro's oldest operating nuclear station. Its four 508-MW(electric) (net) CANDU units were placed in service in the early 1970s. Because of its vintage, Pickering A does not necessarily conform to all current safety design practices and requirements, such as in the extent of separation between process, mitigating, and support systems. This, in turn, raises the possibility of regulatory demand for safety upgrades. Furthermore, the operational surveillance programs in place in Pickering A are not as well supported by system reliability models as the newer stations. A risk assessment study was, therefore, carried out to provide a basis for plant backfit decisions and operational reliability models. Amore » key objective was to appropriately characterize potential intersystem dependencies.« less