Used nuclear fuel is equally safe in pools or in dry storage located at nuclear energy facilities. The U.S. Nuclear Regulatory Commission has reiterated the safety and security of used nuclear fuel management in post-Fukushima. Used nuclear fuel is well-protected from potential natural events and terrorist attacks by a combination of sturdy design and construction, multiple safety systems, ongoing surveillance and inspection, and state-of-the-art security measures.
Used fuel pools are large, robust structures, some 40-feet deep, with reinforced concrete walls several feet thick and steel liners. Water offers superb shielding for radiation, and every fuel pool offers 25 to 30 feet of water shielding and fuel cooling. The volume of water in the pools is so large that any evaporative process associated with a loss of a cooling system would provide time for operators to establish backup water supply. All used fuel pools are designed to seismic standards consistent with other important safety-related structures on plant sites.
After removal from the nuclear reactor, used nuclear fuel requires cooling in water from 37 to 107 days (depending on plant design) to prevent it from generating enough heat to start burning. After that time, it can be sufficiently cooled in air, a used-fuel fire is not a credible risk, and the pool water's primary use is to shield radiation.
After the 9/11 attacks on the World Trade Center and the Pentagon, the NRC issued orders to all nuclear plant operators requiring several measures aimed at mitigating the effects of a large fire, explosion or accident that damages the ability to cool the used fuel pool. These orders were meant to address the aftermath of a terrorist attack or plane crash; however, they would also effectively mitigate the effects of natural phenomena, such as tornadoes, earthquakes or tsunamis.
Augmenting already redundant safety systems to ensure cooling of fuel assemblies in pools, industry has added backup cooling water spray systems and placed portable water supply equipment at locations near the pools so that it can be available quickly in the event of an emergency. As part of their post-Fukushima safety enhancements, facilities also are adding instrumentation with improved capabilities to monitor levels in used fuel pools in the face of extreme events.
Dry storage containers are robust concrete and steel structures with no moving parts. Multiple barriers provide defense-in-depth protection. More than 100 tons of concrete and steel forms a precisely engineered structure to protect every 10 tons of used fuel. Over the past 30 years the nuclear industry has safely loaded more than 1,700 dry storage systems. All these systems are in service today, and there has been zero release of their radioactive contents. To gain license renewals, facilities must put in place stringent aging management programs to assure that the containers are adequately maintained and inspected.
Process for Determining NRC “Waste Confidence”
Waste confidence is a regulatory, generic determination that used nuclear fuel can be stored at nuclear power plant sites—safely and without significant environmental impact—in the period between reactor license expiration and ultimate disposal. The determination eliminates uncertainty with regard to the management of used nuclear fuel once a power plant ceases operations. By making this determination generically in a public rulemaking process, the NRC addresses it from a safety and environmental standpoint for all of its applicable regulatory proceedings without having to address it repeatedly in every individual nuclear plant licensing proceeding.
Timeline of Waste Confidence Decisions:
In 1979, the U.S. District Court for the D.C. Circuit ruled that, under the National Environmental Protection Act, the environmental impact resulting from indefinite storage of used nuclear fuel at a plant site following licensed operation would have to be considered as part of an individual licensing proceeding unless the NRC could determine in a formal proceeding, such as a rulemaking, that it has confidence that used nuclear fuel will be removed from a reactor site following shutdown.
When the Nuclear Regulatory Commission last updated its waste confidence rule in 2010, it expressed confidence that used nuclear fuel can be safely stored for at least 60 years beyond the licensed life of any reactor, without significant environmental impacts, and that sufficient repository capacity will be available “when necessary.”
The U.S. Court of Appeals for the D.C. Circuit ruled in June 2012 that it would vacate and remand the NRC’s 2010 waste confidence decision. The court found that the analysis supporting two of the waste confidence findings (repository availability and safe temporary on-site storage for plant license period plus 60 years) was insufficient under the National Environmental Policy Act.
The NRC on Sept. 15 published for public comment a proposed rule and associated environmental impact statement on extended storage of used nuclear fuel at nuclear energy facilities. This action came in response to the 2012 appellate court ruling. The NRC is following its normal rulemaking process to amend the waste confidence rule. This includes developing a proposed rule and supporting analyses. The generic environmental impact statement is part of the analysis that will support the revised temporary storage rule.
At the end of the public comment period, the NRC staff will consider public comments and develop a final temporary storage rule and generic environmental impact statement (GEIS). Like the proposed rule and draft GEIS, these documents will be provided to the five-member commission for review and approval prior to issuance.