What is Used Nuclear Fuel?
Used nuclear fuel refers to uranium fuel rods that have been removed from a reactor because they are no longer able to efficiently sustain a nuclear reaction. It's helpful to think of the used fuel like a battery that's been run down and needs to be replaced.
Used nuclear fuel is composed of a combination of uranium, plutonium and other radioactive elements like neptunium, americium and curium that are known collectively as minor actinides.
Storage of Spent Nuclear Fuel
Periodically, about one-third of the nuclear fuel in an operating reactor needs to be replaced with fresh fuel. Spent nuclear fuel refers to fuel elements that have been used at commercial nuclear reactors, that are no longer capable of sustaining a nuclear reaction economically, and have been removed from the reactor. It is often also referred to as used nuclear fuel. Spent fuel continues to generate heat because of radioactive decay of the elements inside the fuel. The products left over from the fuel's time in the reactor are still radioactive and emit heat as they decay into more stable elements. Although the heat production drops rapidly at first, heat is still generated many years after shutdown. Therefore, the NRC sets requirements on the handling and storage of this fuel to ensure protection of the public and the environment
The Nuclear Regulatory Commission’s requirements for both wet and dry storage can be found in Title 10 of the Code of Federal Regulations, including the general design criteria in Appendix A to Part 50 and the spent-fuel storage requirements in Part 72. The staff uses these regulations to determine if the fuel will remain safe under anticipated operating and accident conditions. There are requirements on radiation shielding, heat removal, and criticality. In addition, the staff reviews fuel storage designs for protection against: natural phenomena, such as seismic events, tornados, and flooding; dynamic effects, such as flying debris or drops from fuel handling equipment and drops of fuel storage and handling equipment; and hazards to the storage site from nearby activities
Nuclear Regulatory Commission inspectors are responsible for verifying that spent fuel pools and related operations are consistent with a plant's license.
If the spent nuclear fuel is stored in water, the spent fuel pools are designed to seismic standards consistent with other important safety-related structures on the site. The pool and its supporting systems are located within structures that protect against natural phenomena and flying debris. The pools' thick walls and floors provide structural integrity and further protection of the fuel from natural phenomena and debris. In addition, the deep water above the stored fuel (typically more than 20 feet above the top of the spent fuel rods) would absorb the energy of debris that could fall into the pool. Finally, the racks that support the fuel are designed to keep the fuel in its designed configuration after a seismic event.
Dry cask storage allows spent fuel that has already been cooled in the spent fuel pool for several years to be surrounded by inert gas inside a container called a cask. The casks are typically steel cylinders that are either welded or bolted closed. The steel cylinder provides containment of the spent fuel. Each cylinder is surrounded by additional steel, concrete, or other material to provide radiation shielding to workers and members of the public.
An independent spent fuel storage installation is a facility that is designed and constructed for the interim dry storage of spent nuclear fuel. These facilities are licensed separately from a nuclear power plant and are considered independent even though they may be located on the site of another NRC-licensed facility.
The fuel is cooled by natural airflow around the cask. Fuel is often moved to dry cask storage after several years in spent fuel pools, so the heat given off by the fuel has significantly decreased.
The Nuclear Regulatory Commission authorizes storage of spent nuclear fuel at an independent spent fuel storage installation in two ways: site-specific or general license. For site-specific applications, the Nuclear Regulatory Commission reviews the safety, environmental, physical security and financial aspects of the licensee and proposed independent spent fuel storage installation and, if it can operate safely, the Commission issues a license. This license contains requirements on topics such as leak testing and monitoring and specifies the quantity and type of material the licensee is authorized to store at the site. A general license authorizes storage of spent fuel in casks previously approved by the Nuclear Regulatory Commission at a site already licensed to possess fuel to operate a nuclear power plant. Licensees must show that it is safe to store spent fuel in dry casks at their site, including analysis of earthquake intensity and tornado missiles. Licensees also review their programs (such as security or emergency planning) and make any changes needed to incorporate an independent spent fuel storage installation at their site. Of the currently licensed independent spent fuel storage installations, 48 are operating under general licenses and 15 have specific licenses.
The Nuclear Regulatory Commission is responsible for inspection of dry cask storage. All casks also undergo a safety review before they are certified for use by the Nuclear Regulatory Commission. Before casks are loaded, inspectors with specific knowledge of independent spent fuel storage installation operations assess the adequacy of a dry run of the operations by the licensee; they then observe all initial cask loadings. The on-site resident inspectors or region-based inspectors may observe later cask loadings, and the regional offices also perform periodic inspections of routine independent spent fuel storage installation operations.
Under the Atomic Energy Act of 1954, NRC can relinquish authority for regulation of radioactive materials to the States upon request by them and a demonstration that the State has a regulatory program that is adequate and compatible with NRC's. NRC exercised this option for low-level radioactive waste disposal facilities. NRC Agreement States license all operating low-level radioactive waste disposal facilities in the United States, currently three facilities. Licensees may apply to an Agreement State for periodic renewal of a license.
Safeguards-by-Design: Guidance for Independent Spent Fuel Dry Storage Installations (ISFSIs)
This document is part of a series of guidance documents developed by the National Nuclear Security Administration’s Next Generation Safeguards Initiative to assist facility designers and operators in implementing international Safeguards-by-Design (SBD). SBD has two main objectives:
(1) to avoid costly and time-consuming redesign work or retrofits of new nuclear fuel cycle facilities and
(2) to make the implementation of international safeguards more effective and efficient at such facilities.
In the long term, the attainment of these goals would save industry and the International Atomic Energy Agency (IAEA) time, money, and resources ― i.e. a mutually beneficial endeavor.
The purpose of the IAEA safeguards system is to provide credible assurance to the international community that nuclear material and other specified items are not diverted from peaceful nuclear uses.1 The safeguards system consists of the IAEA’s statutory authority to establish safeguards, the safeguards rights and obligations in safeguards agreements and additional protocols, and technical measures implemented pursuant to those agreements. Of foremost importance as a basis for IAEA safeguards is the international safeguards agreement between a country and the IAEA, concluded pursuant to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT).
General License Considerations for Spent Fuel Storage in an Independent Spent Fuel Storage Installation at a Reactor Site
The licensing process and concept of operation for independent spent fuel storage installations (ISFSIs) in the United States have evolved over time. Early considerations were based upon the safe storage of spent fuel in an existing reactor's spent fuel pool. In 1980, 10 CFR Part 72 was initially developed with the idea of a wet storage environment for spent fuel (e.g., GE-Morris facility). As dry cask storage technology evolved, consideration expanded to include storage of spent fuel in casks on a storage pad on a reactor site. This would continue to allow spent fuel to be discharged from the spent fuel pool to enhance operational flexibility by ensuring the spent fuel pool could handle a full core discharge during an outage. The Nuclear Waste Policy Act mandated that the use of dry cask storage technologies be permitted under a general license; therefore, in 1990, 10 CFR Part 72 was modified to incorporate these provisions. The attributes of general licensing for an independent spent fuel storage installation are as follows: