Change from storing ten year cooled used nuclear fuel to six year cooled used fuel

CANDU reactors use non-enriched uranium in fuel bundles. After the fuel has been used in the reactor the used fuel gives off significant heat and radiation. These highly radioactive bundles are stored in a pool that provides cooling and shielding while the radioactivity decays, reducing the radioactivity and heat that the used fuel emits. Used fuel that has been cooled for minimum 10 years has then been transferred into Dry Storage Containers (DSCs) for dry storage. The DSC is a rectangular-section container made of a double carbon-steel shell filled with reinforced high density concrete which provides the necessary radiation shielding, heat removal path, and containment of radioactive materials. Analyses performed on the DSC design ensure the integrity and stability of the DSC for all design load cases. OPG presently plans to shut down the Pickering Nuclear Generating station in 2025. Defueling the reactors will require additional space in the pool for discharged used fuel. At that time there will not be enough 10 year old fuel for removal to create the needed space. OPG proposes to load fuel that has been stored for minimum 6 years. This paper presents the technical evaluations of loading minimum 6 years old fuel in a DSC. The analyses have been performed to assess the outcome of the DSC design requirements and ensure the DSC primary functions are met. (author)