Dry storage systems evaluation at Ontario Hydro

Ontario Hydro will need additional storage facilities in the early 1990's. After cooling the irradiated fuel in station waterpools, it may be advantageous to use dry storage facilities instead of more waterpools. To evaluate the potential technical and cost benefits of dry storage facilities, the conceptual development of concrete canister and dry vault systems is being undertaken. In addressing the dry storage systems, a generic approach has been followed. Two alternative dry vault designs were proposed. In one design, the storage tubes are rectangular in shape to accommodate existing rectangular waterpool fuel racks, while the other has cylindrical tubes and uses high storage density cylindrical containers. The latter could potentially also be used in the fuel transportation and disposal phases, thereby reducing fuel handling. The results indicate that the dry vault design using the existing waterpool racks (trays and modules) is preferable for the storage phase alone. Ontario Hydro is also undertaking a development program to assess the feasibility of an integrated concrete cask system to meet the requirements of storage, transportation and disposal of fuel. Progress to date has concentrated in the development of high compressive strength (≅ MPa) and low pH (≅10) cement pastes and concrete mixes. Also, half scale model tests are being tested to evaluate their impact and fire resistance during transportation accidents and their thermal behaviour during storage and disposal