Underground siting of CANDU power stations

Abstract

Ontario Hydro is currently investigating the feasibility of constructing an underground CANDU nuclear power station. Two underground concepts are being examined: deep rock burial with reactor units located in deep hard rock caverns and cut-and-cover burial in which the station is constructed in an open excavation and subsequently covered with backfill. The investigation is developing conceptual station designs for both underground concepts and is examining potential Ontario sites, safety and operational considerations, construction methods and schedules, and stations capital costs. This paper focuses on the deep rock excavation concept and presents the major interim findings of the Ontario Hydro study. A description of southern Ontario rock formations, in terms of their capability of supporting large underground caverns, is presented. In addition, recent results of a test hole drilling program are described. The paper summarizes the in situ and laboratory measurements and draws inferences regarding the underground station design. A preliminary assessment of the potential safety advantages of underground siting (extra containment barrier, reduced seismic motion) is presented and construction and operational considerations are reviewed. Finally, the areas of major cost disadvantage with respect to surface stations are identified and approximate overall station cost penalties are discussed. Ontario Hydro is Canada's largest public power utility with a total installed generating capacity of just over 22,000 MWe, of which roughly 25% is provided by CANDU reactors - a unique Canadian design which uses natural uranium as fuel and heavy water as moderator and coolant in the reactor. | Ontario Hydro is currently investigating the feasibility of constructing an underground CANDU nuclear power station. Two underground concepts are being examined: deep rock burial with reactor units located in deep hard rock caverns, and cut-and-cover burial in which the station is constructed in an open excavation and subsequently covered with backfill. The investigation is developing conceptual station designs for both underground concepts and is examining potential Ontario sites, safety and operational considerations, construction methods and schedules, and stations capital costs. This paper focuses on the deep rock excavation concept and presents the major interim findings of the Ontario Hydro study.