U.S. Commercial Spent Fuel Storage Facilities: Public Health and Environmental Considerations

Abstract

U. S. commercial reactor plants are installing spent fuel storage facilities formally called Independent Spent Fuel Storage Installations (ISFSI) to provide needed storage space for spent nuclear fuel assemblies. Although this might be a primary objective for the utility that owns the plant, the U.S. Nuclear Regulatory Commission (U.S. NRC) has other priorities as addressed by ISFSI regulations in Title 10 of the Code of Federal Regulations, Part 72. These regulations establish a number of criteria that ensure that above all, the storage of spent nuclear fuel does not adversely affect the health and safety of the public or the environment. There are 3 primary ISFSI design activities that ensure the health and safety of the public and protection of the environment: site selection, storage system selection, and storage facility design. The regulatory requirements that address ISFSI site selection are found in 10 CFR 72, Subpart E, “Siting Evaluation Factors.” This section requires that potential ISFSI sites be assessed for impacts such as site characteristics that may affect safety or the environment, external natural and man-induced events, radiological and other environmental conditions, floodplains and natural phenomena, man-made facilities and activities that could endanger the ISFSI, and construction, operation, and decommission activities. All of these potential impacts must be carefully evaluated. First, the ISFSI capacity requirements should be determined. Potential sites should then be evaluated for siting impacts to ensure the site has adequate space, it can be licensed, it will minimize radiological doses to the general public and on-site workers, and construction, operation, and decommissioning won’t have a major effect on the environment or nearby population. The regulatory requirements that address storage system selection are found in 10 CFR 72, Subpart F, “General Design Criteria.” This section requires that the storage system be designed to withstand environmental conditions, natural phenomena, fires and explosions and that it includes confinement barriers, retrievability measures, and criticality safety. In order to be licensed by the U. S. NRC, all spent fuel storage systems must be evaluated to show how they meet these requirements. U.S. NRC approval of the system ensures that the requirements have been met and therefore ensure the health and safety of the public and environment are protected. The regulatory requirements that address the ISFSI design are also found in 10 CFR 72, Subpart F as well as 10 CFR 72, Subpart H, “Physical Protection.” Like the storage systems, the ISFSI site must be designed to withstand environmental conditions, natural phenomena, fires, and explosions. But the design must also include security provisions. Security features protect the spent fuel from attack or sabotage and therefore protect the health and safety of the public and the environment. The primary potential impact of spent fuel storage is radiation dose. The key regulatory requirement that addresses radiation dose is found in 10 CFR 72.104. This section requires that the dose to any individual member of the public not exceed 0.25 mSv (25 mrem) to the whole body, 0.75 mSv (75 mrem) to the thyroid, and 0.25 mSv (25 mrem) to any other organ, from exposure to direct radiation from the ISFSI, radioactive liquid or gaseous effluents, and radiation from other nearby nuclear facilities. Design features of the storage system and ISFSI include shielding by the cask enclosure, distance, berms as required, etc. to attenuate direct radiation, and confinement provisions to prevent radiological effluent leakage. The ISFSI must be located such that the cumulative doses from the ISFSI and reactor plant do not exceed regulatory requirements. Thus it can be seen that ISFSI site selection, storage system selection, and storage facility design all work together to ensure the health and safety of the public and environment are protected. Comments regarding the contents of this paper may be submitted to the author, Donald W. Lewis, Shaw Environmental & Infrastructure, 9201 E. Dry Creek Road, Centennial, Colorado, 80112, U.S.A.