The Only Option Remaining: On-Site Storage
Today, the only available solution for utilities is to store SNF on-site in water pools or in long-term above-ground storage casks. The volume of the water pools within each reactor limits the number of fuel assemblies it can hold at one time. Conceptually, the number of dry casks that can be used to store SNF is unlimited.
The water-pool storage option involves storing SNF assemblies under at least 20 feet of water to provide shielding from the radiation and removal of decay heat (Figure 6). About one-fourth to one-third of the total fuel load is removed from the reactor, typically every 18 months, and replaced with fresh SNF. You may recall that early in the development of commercial nuclear reactors, the government was expecting to construct a nuclear fuel reprocessing plant and the pools were sized to hold and cool SNF until it could be transported to the reprocessing facility. On April 7, 1977, President Jimmy Carter banned the reprocessing of commercial reactor fuel in the U.S. Since then, many of the nuclear plant spent fuel pools have either reached or are nearing capacity (Figure 7).
6. Pool party. Storing spent fuel assemblies underwater in a storage pool. Source: DOE
7. Limited nuclear fuel pool capacity. This chart shows the cumulative number of filled pools at nuclear power plants. All operating nuclear power reactors are storing used fuel under NRC licenses in spent fuel pools. Some operating reactors are using dry cask storage. Source: NRC
Current regulations permit re-racking of the storage pool grid and fuel rod consolidation, subject to NRC review and approval, to increase the amount of SNF that can be stored in a pool. However, both of these methods are constrained by the size of the pool.
In the early 1980s, utilities began looking at using dry casks to increase on-site storage capacity. The process of loading a cask, consisting of a steel cylinder designed to hold typically two dozen SNF assemblies, takes place underwater in the storage pool. Once the assemblies have cooled for given period of time, they are transferred underwater from the storage racks to the submerged cask. Next, the cask is removed from the storage pool, where excess water is removed. Then it is backfilled with an inert gas to enhance decay-heat transfer capabilities, welded or bolted closed, inserted into a concrete overstructure (depending on design), and stored vertically on a concrete pad. The cask itself provides the necessary radiation shielding. Other above-ground designs seal the SNF inside a steel cylinder, which is then inserted either vertically into a concrete silo or horizontally into a concrete vault. The concrete provides the radiation shielding (Figure 8).
8. On-site storage. Spent nuclear fuel storage canisters are designed to be placed either vertically in aboveground concrete or steel structures, or stored horizontally in aboveground concrete vaults. Courtesy: NRC
The NRC approves dry-storage systems by evaluating each design for resistance to accident conditions such as floods, earthquakes, tornado missiles, and temperature extremes. Some cask designs can be used for both storage and transportation. The dry-storage casks are located in an independent spent fuel storage installation (ISFSI). Such storage may be either at the reactor site or elsewhere (see "How to Solve the Used Nuclear Fuel Storage Problem," POWER, April 2008).
Site-Specific and General Licenses
The NRC authorizes storage of SNF at an ISFSI under two licensing options: site-specific licensing and general licensing. Under a site-specific license, an applicant submits a license application to the NRC, and a technical review is performed on the safety aspects of the proposed ISFSI. If the application is approved, the NRC issues a license that is valid for 20 years. The license contains technical requirements and operating conditions (including fuel specifications, cask leak testing, surveillance, and other requirements) for the ISFSI and specifies what the licensee is authorized to store at the site.
A general license authorizes a nuclear plant licensee to store SNF in NRC-approved casks at a site that is licensed to operate a power reactor under 10 CFR Part 50. Licensees are required to demonstrate that their site is adequate for storing SNF in dry casks. The licensee must also make any necessary changes to its security program, emergency plan, quality assurance program, training program, and radiation protection program to incorporate the ISFSI at its location. In addition, these evaluations must show that the cask’s technical specifications covered in the Certificate of Compliance (CoC) can be met, including analysis of earthquake intensity and tornado missiles (objects accelerated by very high winds). The NRC issues a CoC to the vendor following a technical review and approval of a dry storage system’s design in accordance with 10 CFR 72. The certificate expires 20 years from the date of issuance and can be renewed in additional 20-year increments.
The first U.S. commercial ISFSI was licensed by the NRC in 1986 at the Surry Nuclear Plant in Virginia. Since then, dry cask storage has become common among licensees needing additional SNF storage capacity. According to the NRC, SNF is currently in dry storage at 40 general license ISFSIs and 15 site-specific license ISFSIs. For example, Southern Nuclear’s Hatch and Farley nuclear plants safely store spent fuel in above-ground dry storage casks (Figure 9).
9. Workable solution. Southern Nuclear’s dry-cask storage system at Hatch Nuclear Plant. Courtesy: Southern Nuclear
Southern Nuclear is the operator of the Vogtle nuclear plant (see "Plant Vogtle Leads the Next Nuclear Generation," POWER, November 2009). At Vogtle, all all of the used fuel for both units is stored safely under water in two storage pools located in the protected area of the plant. There is still storage capacity available in the existing pools to last for years. Therefore, by combing the existing capability of the storage pools and dry-storage facilities when the spent fuel pool does reach capacity, all of Southern Nuclear’s sites have the capability to safely store spent fuel on-site for the duration of each plant’s operating license.
Hard Lesson Learned
It remains unclear if a logical and politically acceptable path toward developing a national, long-term storage facility for SNF and HLW is possible. It is our opinion that there is not. The DOE and its predecessor agency has tried and failed multiple times, over several decades. State veto power over siting a storage facility makes approval of a facility essentially a national referendum on nuclear power, given that a veto must be overridden by the Senate and the House. Also, the extremely long period of time required to develop any storage facility would certainly span presidential administrations of both political parties, making any project like Yucca Mountain susceptible to closure when the political winds change. Why would we expect a different result at a new site a decade hence?
History can be a stern teacher, and we should learn this important lesson. There is no long-term, politically expedient road to a Yucca Mountain – type facility anywhere in the U.S. We expect the blue ribbon commission to spend the next two years or more studying the problem only to come to the same conclusion.
As a nation, we would be better served if Congress would amend the NWPA and NWPAA to delete the statutory responsibility of the DOE to store SNF, refund the NWF contributions, and quickly settle the 60-plus lawsuits pending to cover all current and future nuclear plant SNF storage costs. The elegant solution is nuclear fuel reprocessing, perhaps primed by reprogramming NWF money into building such a facility. But we’ll hold that discussion for another day.
—James M. Hylko (jhylko1@msn.com) is a POWER contributing editor. Dr. Robert Peltier, PE is editor-in-chief.
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Comments (7)
You take a pessimistic conclusion that the only available "solution" is continued on-site storage. You believe it is not possible to find a site for a repository that can gain national, state and local acceptance. Well, Sweden and Finland were able to do that, and Canada (after a false start) seems to be following a similar path with assurance to potential host locations that if they don't support it the facility will not be built there. It may take some time, but I believe it is worth another try at finding a repository that can meet safety requirements can be found if we use better siting criteria, an open process of communications and with incentives.
Your forecast that the "candidate locations" considered by the Blue Ribbon Commission will be leaked and the Secretary of Energy will delay the final report seems unlikely. Secretary Chu has made it clear that the Commission is not a "siting board." The big question it will grapple with is likely to be whether to head in the direction of reprocessing or not. Even if they support it (a) it will take decades to be operational and (b) we still need a repository (let's not forget the defense waste and the residue after reprocessing.)
Also, spending money does not guarantee success. Consider all the money spent on cancer research and cancer remains a leading cause of death.
Of course my other reaction was that reprocessing attempts to solve the wrong problem. The main obstacle to previous attempts at a waste repository seems to have been lack of apparent regional fairness. A group of six or more regional repositories would be much more likely to be perceived as fair. The past failure could be attributed to the unsuccessful attempt to save money by building only one.
Either way, hopefully secretary Chu will do the visionary thing, and boost research and development of Gen IV reactors (such as IFR and LFTR) that can completely burn the long-lived waste components (once they’ve been recovered in a reprocessing facility). As an added bonus, these reactors have such low demands of uranium or thorium ore, humanity can be assured of a supply that is sustainable indefinitely and with no possibility of monopoly supplier cartels.
I don't think that that word means what you think it does. Next time, use "by far", or perhaps "the most expensive failure by a few orders of magnitude", if you feel the need to speak in math.
Of course my other reaction was that reprocessing attempts to solve the wrong problem. The main obstacle to previous attempts at a waste repository seems to have been lack of apparent regional fairness. A group of six or more regional repositories would be much more likely to be perceived as fair. The past failure could be attributed to the unsuccessful attempt to save money by building only one.
Either way, hopefully secretary Chu will do the visionary thing, and boost research and development of Gen IV reactors (such as IFR and LFTR) that can completely burn the long-lived waste components (once they’ve been recovered in a reprocessing facility). As an added bonus, these reactors have such low demands of uranium or thorium ore, humanity can be assured of a supply that is sustainable indefinitely and with no possibility of monopoly supplier cartels.