CONCEPTUAL PLANT LAYOUT OF THE CANADIAN GENERATION IV SUPERCRITICAL WATER-COOLED REACTOR

Canada is developing a 1200 MWe supercritical water-cooled reactor (SCWR), which has evolved from the well-established pressure-tube type CANDU (R)(1) reactor. This SCWR reactor concept, which is often referred to as the Canadian SCWR, uses supercritical water as a coolant, has a low-pressure heavy water moderator, and a direct cycle for power production. The reactor concept incorporates advanced safety features, such as passive emergency core cooling, long-term decay heat rejection to the environment, and fuel melt prevention via passive moderator cooling. To support these features, major systems and major components are identified and laid out inside the reactor buildings. The Canadian SCWR uses 2 nested reactor buildings for 2 separate functions: (i) a leak-tight containment building to house all safety-related systems and (ii) a shield building to protect critical components against external threats, such as airplane crashes, missile attacks, tornados, and flooding. Two redundant and independent passive safety systems are employed for a significant safety improvement over existing nuclear power plants. In passive safety systems, to provide sufficient driving force for naturally circulated coolant as well as to provide gravity head for a gravity-driven core flooding function, the Canadian SCWR reactor relies on elevation differences between the reactor core and the safety system components. These elevation differences, the required cooling pool volumes, and the optimum layout of safety-related piping are major factors influencing the containment design. As a defence-in-depth, the containment building and safety systems provide successive barriers to the unplanned release of radioactive materials, while providing a path for heat flow to the ultimate heat sink, the atmosphere. Access to the reactor core for refuelling is from the top of the reactor, with water used as shielding during the refuelling operations. The accessibility to the reactor and protection of the environment are additional factors influencing the plant design. This paper describes the physical implementation of the major systems of the Canadian SCWR within the reactor buildings and the position of major plant services relative to the reactor buildings.