Background

In the United States, the national inventory of commercial spent nuclear  fuel amounts to nearly 70,000 metric tons, which is stored at 75 sites in  33 states (see fig. 1).
Fuel for commercial nuclear power reactors is typically made from low- enriched uranium fashioned into thumbnail-size ceramic pellets of  uranium dioxide. These pellets are fitted into 12- to 15-foot hollow rods,  referred to as cladding, made of a zirconium alloy. The rods are then  bound together into a larger assembly. A typical reactor holds about 100  metric tons of fuel when operating—generally from 200 to 800 fuel  assemblies. The uranium in the assemblies undergoes fission—a process  of splitting atoms into fragments and neutrons that then bombard other  atoms—resulting in a sustainable chain reaction that creates an  enormous amount of heat and radioactivity. The heat is used to generate  steam for a turbine, which generates electricity. The fragments created  when fission splits atoms, or when bombarding neutrons bond with  atoms, include hundreds of radioisotopes, or radioactive substances,  such as krypton-90, cesium-137, and strontium-90. Furthermore, the  neutron bombardment of uranium can also create heavier radioisotopes,  such as plutonium-239. The radioisotopes produced in a reactor can  remain hazardous from a few days to many thousands of years; these  radioisotopes remain in the fuel assemblies and as components of the  resulting spent fuel.
Each fuel assembly is typically used in the reactor for 4 to 6 years, after  which most of the fuel it contains is spent, and the uranium dioxide is no  longer cost-efficient at producing energy. Reactor operators typically  discharge about one-third of the fuel assemblies every 18 months to 2  years and place this spent fuel in a pool to cool. Water circulates in the  pool to remove the enormous heat generated from the radioactive decay  of some of the radioisotopes. As long as circulating water continues to  remove this heat, pool water temperature is maintained well below  boiling, typically below 120 degrees Fahrenheit. If exposed to air,  however, recently discharged spent fuel could rise in temperature by  hundreds or thousands degrees Fahrenheit. A pool is needed to ensure  that heat generated from the decay of radioisotopes, particularly  immediately after discharge from a reactor, does not damage fuel rods  and release radioactive material. Figure 2 shows a fuel pellet for a  commercial nuclear reactor and a fuel rod in an assembly.
The pools of water are typically about 40 feet deep, with at least 20 feet of  water covering the spent fuel, and the water is cooled and circulated to  keep the assemblies from overheating. These pools are constructed  according to NRC’s requirements, typically 4- to 6-feet thick with steel- reinforced concrete and a steel liner. The pools must be located inside  what is known as the vital area of a nuclear power reactor, protected by  armed guards, physical barriers, and limited access. Within the vital area,  pools may be in one of two locations, depending on the type of reactor. In  a pressurized water reactor, spent fuel is stored in a pool at or below  ground level, but in a typical boiling water reactor, spent fuel is stored in  a pool well above ground level, near the reactor vessel, as high as three  stories above ground. Figure 3 shows the location of a spent fuel pool  for a boiling water reactor, and figure 4 shows a typical spent fuel pool.
As part of the construction permit and operating license application process  for nuclear reactors, NRC requires companies licensed to operate these  reactors to assess natural hazards, such as earthquakes, floods,  hurricanes, and tidal waves that their reactors might face. Reactor  operators must also show that their proposed pool designs would survive  the most severe natural hazards, or combinations of less severe hazards,  expected for that particular area.NRC has required reactor operators to reevaluate their original design  criteria against more recent seismic information that has been developed  since many of the nuclear power plants were first licensed. According to  NRC documents, NRC developed its requirements with a concept of  “defense-in-depth,” which is a way of designing and operating nuclear   Since the Fukushima Daiichi disaster,  power reactors that focuses on creating multiple independent and  redundant layers of defense to compensate for potential human and  mechanical failures so that no single layer, no matter how robust, is  exclusively relied upon.
All radioactive substances—referred to as radioisotopes—are unstable and  spontaneously transform themselves into more stable isotopes by capturing or emitting  atomic particles or by fission. The time it takes a radioisotope to decay into more stable  substances is measured by a half-life. A half-life is the length of time it takes for one-half  of a particular radioisotope to decay into a new isotope. After two half-lives, one-quarter of  the original radioisotope will be left, but three-quarters will have changed to the new  isotope. After 10 half-lives, only 1/1,000 of the original radioisotope is left. nuclear emergency.years and will take over 300 years to decay to negligible amounts.  Cesium-137 contributes to the decay heat in a spent fuel pool and is a  significant land contaminant if released.  ) In contrast, cesium-137 has a half-life of 30.2  Typically, according to NRC officials, spent fuel must remain in a pool for at  least 5 years to decay enough to remain within the heat limits of currently  licensed dry cask storage systems. Spent fuel cools very rapidly for the first  5 years, after which the rate of cooling slows significantly. Spent fuel can  be sufficiently cool to load into dry casks earlier than 5 years, but doing so  is generally not practical. Some casks may not accommodate a full load of  spent fuel because of the greater heat load. That is, the total decay heat in  these casks needs to be limited to prevent the fuel cladding from becoming  brittle and failing, which could affect the alternatives available to manage  spent fuel in the future, such as retrieval. In recent years, reactor operators  have moved to a slightly more enriched fuel, which can burn longer in the  reactor. Referred to as high-burn-up fuel, this spent fuel may be hotter and  more radioactive coming out of a reactor than conventional fuel and may  have to remain in a pool for as long as 7 years to cool sufficiently.
In the original designs submitted for spent fuel pools, fuel assemblies  were packed in relatively low densities, but operators have replaced these  low-density racks with higher-density racks to store more spent fuel.  According to NRC officials, NRC accepts high-density storage of spent  fuel if certain conditions are met, such as adequate cooling, the  maintenance of structural integrity, and the prevention of a critical chain  reaction. Neutron-absorbing materials can be used to keep closely  packed assemblies from starting a chain reaction.in the 1980s, NRC conducted several safety studies on the impact of  increasing the density of spent fuel in pools and determined that the risk  of a potential release from overheating or igniting, or even of a critical  chain reaction from the dense geometric configuration, was small,  particularly if certain steps were taken to reduce the risk. Even with re-  As pools began to fill  racking to a dense configuration, however, spent nuclear fuel pools are  reaching their capacities and may contain several thousand assemblies  each.
As reactor operators have run out of space in their spent fuel pools, more  operators have turned to dry cask storage systems. These systems consist  of a steel canister protected by an outer cask made of steel or steel and  concrete to provide shielding from the heat and radiation of spent fuel. In  one typical process of transferring spent fuel to dry storage, reactor  operators place a steel canister inside a larger steel transfer cask and  lower both into a pool. Spent fuel is loaded into the canister, a lid is placed  on the canister, and then both the canister and transfer cask are removed  from the pool. The lid is welded onto the canister, and the water drained.  Then the canister and transfer cask are aligned with a storage cask and the  canister is maneuvered into the storage cask. The storage casks, in either  vertical or horizontal designs, are usually situated on a large concrete pad  surrounded by safety systems and a security infrastructure, such as  radiation detection devices and intrusion detection systems. The transfer  process has become routine at some power plants (see fig. 5).
In addition to regulating the construction and operation of commercial  nuclear power plants, NRC also regulates spent fuel in dry storage. NRC  requires that spent fuel in dry storage be stored in approved systems that  offer protection from significant amounts of radiation. NRC evaluates the  design of passively air-cooled dry storage systems for resistance to  certain natural disasters, such as floods, earthquakes, tornado missiles,  and temperature extremes. NRC may require physical tests of the  systems, or it may accept information derived from scaled physical tests  and computer modeling. For example, dry storage systems must be able  to withstand, among other things, being dropped from the height to which  it would be lifted during operations; being tipped over by seismic activity,  weather, or other forces or accidents; fires; and floods. NRC has also  analyzed the performance of dry storage systems in different terrorist  attack scenarios. Once a dry storage system is approved, NRC issues a  certificate of compliance for a cask design. Currently, NRC may issue a  cask certificate for a term not to exceed 40 years. Similarly, NRC may  renew a cask certificate for a term not to exceed 40 years (see fig. 6).
The length of time that spent fuel can safely be stored in dry casks is  uncertain. We earlier reported that experts agree that spent fuel can be  safely stored for up to about 100 years, assuming regular monitoring and  maintenance.associated rule stating that spent fuel can be safely stored for up to 60   In December 2010, NRC issued a determination and  years beyond the licensed life of the reactor in a combination of wet and  dry storage. Four states, an Indian community, and environmental  groups petitioned for review of NRC’s rule, however, arguing in part that  NRC violated the National Environmental Policy Act by failing to prepare  an environmental impact statement in connection with the  determination. On June 8, 2012, the U.S. Court of Appeals for the  District of Columbia Circuit held that the rulemaking did require either an  environmental impact statement or a finding of no significant  environmental impact and remanded the determination and rule back to  NRC for further analysis. NRC has not yet indicated what actions it will  take in response to the court’s action. On August 7, 2012, the  commissioners voted not to issue final licenses dependent on the  determination and rule until it addresses the court’s remand, however, the  commission is currently preparing an environmental impact statement on  the effects of storing spent fuel for 200 years. In addition, NRC, DOE, and  industry are conducting a series of studies to evaluate the regulatory  actions or additional engineering measures needed for long-term storage  of spent fuel to account for possible degradation of the canisters or the  spent fuel in the canisters.

		Federal Efforts to Identify and Develop a Site for a Spent Fuel Repository

Since the 1950s, even before operation of the first commercially licensed  nuclear power reactor in the United States, the federal government  recognized the need to manage the back end of the fuel cycle—spent  nuclear fuel removed from a reactor. A 1957 National Academy of  Sciences report endorsed deep geological formations to isolate high-level  radioactive waste, which includes spent nuclear fuel, but during the 1950s  and 1960s, nuclear waste management received relatively little attention  from policymakers. The early regulators and developers of nuclear power  viewed waste disposal primarily as a technical problem that could be  solved when necessary by applying existing technology. Attempts were  made to reprocess the spent nuclear fuel—that is, to reuse some useful  elements remaining in a spent fuel assembly after it is discharged from a  reactor, such as unfissioned uranium-235—but this process was not  pursued because of economic issues and concerns that reprocessed  nuclear materials raise proliferation risks.
As noted above, the Nuclear Waste Policy Act of 1982 charged DOE with  investigating sites for a federal geologic repository and authorized DOE to  contract with reactor operators to take custody of spent fuel for disposal  at the repository beginning in 1998. In 1987, Congress amended the  Nuclear Waste Policy Act to direct DOE to focus its efforts only on Yucca  Mountain for a repository. DOE did not submit a license application for  Yucca Mountain until 2008, however—10 years after it was supposed to  start taking custody of spent fuel. In 2009, DOE announced that it  planned to terminate its work related to the Yucca Mountain repository,  and in 2010 it filed a motion to withdraw the license application. NRC’s  licensing board denied the motion, but DOE continued to take steps to  dismantle the repository project. In September 2011, the NRC  commissioners considered whether to overturn or uphold the licensing  board’s decision, but they were evenly divided and unable to take final  action on the matter. Instead, the NRC commissioners directed the  licensing board to suspend work by September 30, 2011. NRC’s failure to  consider the application, among other things, is being contested in federal  court. Several parties have filed a petition against NRC asking the federal  court to, among other things, compel NRC to provide a proposed  schedule with milestones and a date for approving or disapproving the  license application. Currently, it remains uncertain whether NRC will have  to resume its license review efforts and whether a repository at Yucca  Mountain will be built. In the interim, in 2010, the administration directed  DOE to establish a Blue Ribbon Commission of experts to study an array  of nuclear waste management alternatives. DOE established the  commission, which studied alternatives including options for interim  storage of spent fuel and permanent disposal. In its January 2012 report,  the commission recommended that the nation adopt centralized storage  of some spent fuel as an interim measure but, at the same time, develop  a process to find and license a site for a permanent repository. With  nowhere to send the spent fuel, operators must keep it on-site at  decommissioned and operating commercial reactors until some option to  move it off-site becomes available.
Countries other than the United States also produce electricity from  nuclear power reactors and have programs to manage their spent nuclear  fuel. Some countries, such as France, store their spent fuel in pools until  it can be reprocessed, and other countries, such as Canada, use both wet  and dry storage systems. Following the accident at Fukushima, Japan  temporarily shut down its nuclear reactors, but it has restarted one and  may restart others. Several countries have programs to develop  permanent disposal facilities. See appendix II for more information on  other countries’ programs.

	Large Quantities of Spent Nuclear Fuel Are Expected to Remain at Commercial Reactor Sites for Decades

The amount of spent fuel accumulating at commercial reactor sites is  expected to increase by about 2,000 metric tons each year until it can  begin to be shipped off-site and, even then, shipping it off-site will be a  decades-long process. By then, currently operating reactors will begin to  retire, dismantling their spent fuel pools and leaving the spent fuel  stranded in dry storage canisters with limited options for repackaging  them, should repackaging be required to replace degraded canisters, or  to meet transportation or disposal requirements.

		Spent Nuclear Fuel Could Nearly Double before Being Transported to a Storage or Disposal Facility

The amount of spent fuel is expected to more than double to about  140,000 metric tons by 2055, when the last of currently operating reactors  is expected to retire, according to the Nuclear Energy Institute, but it may  take at least that long to ship the spent fuel off-site. This amount is based  on the assumption that the nation’s current reactors continue to produce  spent nuclear fuel at the same rate—about 2,000 additional metric tons  annually; that no new reactors are brought online; and that some decline  in the generation of spent fuel takes place as reactors are retired. At the  end of 2012, over 69,000 metric tons is expected to accumulate at 75  sites in 33 states, enough to fill a football field about 17 meters deep.Without central storage options or an available permanent disposal  facility, spent fuel continues to accumulate at the sites where it was  generated.
Current industry practice has been to store the spent fuel in the pools,  with an industry expectation that, at some point, DOE would begin to take  custody of it. In 2011, about 74 percent of commercial spent fuel was  stored in pools, and the remaining 26 percent was in dry storage, but  these proportions will slowly change as more pools fill and the spent fuel  is transferred to dry storage. According to the Nuclear Energy Institute, by  2025, assuming no new reactors, the proportion of spent fuel in wet  storage and dry storage should be roughly equal, about 50,000 metric  tons in each. Shortly after 2055, when the last currently operating  reactors’ licenses are expected to expire, and the reactors are expected  to retire, virtually all the spent fuel arising from the current fleet will have  been moved to dry storage. Figure 7 shows the trend of accumulated  spent fuel and the rate of spent fuel transferred from wet storage to dry  storage through 2067, according to our analysis of Nuclear Energy  Institute data.
When it became evident that DOE was likely decades behind its deadline  to pick up spent fuel, nuclear power plant operators began transferring  spent fuel to dry storage to retain enough space in their pools to safely  discharge fuel from their reactors. The rate of transfer differs by the  operating and spent fuel characteristics of the reactor—that is, reactor  type and size—as well as the size of the spent fuel pool. In general,  reactor operators must transfer an average of three to six canisters each  year to keep pace with the discharge of spent fuel from their reactors.  Table 1 provides data on reactors and spent fuel and the rate of transfer  anticipated to dry storage.
Reactor operators continue to fill their spent fuel pools until capacity is  reached, in part because the transfer of spent fuel to dry storage is costly  and time-consuming. Specifically, operators must take extensive steps to  ensure that safety precautions to protect workers and the public are met.  Before an operator can transfer a single fuel assembly to dry storage, the  operator must train personnel and practice the procedure. According to  industry representatives, these efforts involve several weeks of mobilization  and demobilization of equipment before and after the transfer. The transfer  of spent fuel to a single canister typically takes at least 1 week.
The amount of spent fuel that accumulates and is stored on-site will also  be affected by the timing of an off-site central storage or permanent  disposal facility, if and when one becomes available. To estimate the  amount of accumulation at commercial nuclear power plants before an  off-site facility becomes available, we considered three scenarios:  (1) Yucca Mountain as a permanent disposal facility, (2) two federally  funded centralized storage facilities, and (3) an alternative permanent  disposal facility. For purposes of our analysis, we assumed that each  storage facility would be licensed by NRC and funded by Congress.  Furthermore, for each scenario, we recognized that multiple factors could  affect the projected time frame. These factors include the siting, licensing,  and construction, and the start of operations of the storage or disposal  facility, as well as the time needed to ship spent fuel to the off-site facility  and reduce the backlog of already-accumulated spent fuel. For each  scenario, we made certain assumptions and incorporated them into our  analyses. We estimated the earliest likely dates that Yucca Mountain, two  federal centralized storage facilities, or a permanent repository could be  opened. Our analysis was based on information from our prior work in  analyzing alternatives to a repository at Yucca Mountain, including expert  input to develop assumptions to model the time frames for different  scenarios for spent fuel management.on our methodology for this analysis.
See appendix I for more details  Our analysis showed that regardless of which storage or disposal scenario  was considered, it would take at least 15 years to open an off-site location  and decades to ship the spent fuel once the central storage or disposal  facility became available. The time needed for shipment depends on the  amount of fuel accumulated and assumes a shipment rate of 3,000 metric  tons per year—the rate that DOE developed as part of its plans for Yucca  Mountain. Experts we consulted in our prior work agreed this rate was  reasonable. A faster or slower shipping rate could affect the rate of  continued accumulation or drawdown of the backlog. When we conducted  our analysis in 2009, we reported that Yucca Mountain—the first  scenario—was likely to offer the earliest option for off-site disposal, in 2020.  Since then, the process for licensing Yucca Mountain has stopped, and it is  unclear whether the licensing process will be resumed; in addition, many  key workers who worked on Yucca Mountain have left DOE for other  employment or retirement. If the licensing process for Yucca Mountain  were resumed in 2012, we estimate that DOE would require roughly at  least 15 more years to open the site as a repository, or sometime around  2027. We estimate that the second scenario—for the federal government to  site, license, construct, and open two centralized storage facilities—might  take about 20 years, with completion in 2032, because of the complexities  in siting, licensing, and constructing such facilities. We estimate that the  third scenario—for a potential permanent disposal facility as an alternative  to the Yucca Mountain repository—would take the longest to be realized,  about 40 years, or 2052, because of the additional scientific analysis  required to ascertain the safety of a permanent disposal facility. Figure 8  shows the amount of spent fuel that is expected to accumulate in each  state for the years 2012; 2027 (the earliest likely opening date if the Yucca  Mountain repository were to be licensed and constructed); 2032 (the  earliest a centralized storage facility could be expected to open); 2052 (the  earliest a permanent disposal facility other than Yucca Mountain could be  expected to open); and 2067, when all currently operating commercial  nuclear power reactors are expected to have retired and transferred their  spent fuel to dry storage.
Resolving the issue of what to do with commercial spent nuclear fuel will  likely be a decades-long, costly, and complex endeavor. Planning ahead  to allow reactor operators and local communities to make better-informed  and forward-looking decisions is important in such a complex   undertaking. For example, DOE had earlier created designs for a specific  type of canister for disposal at the Yucca Mountain repository, and had  informed reactor operators that all spent fuel destined for Yucca Mountain  needed to be packaged in this specific canister, called a transportation,  aging, and disposal canister. Although the canister had not gone into commercial production, its design specifications had at least informed  reactor operators. Now that both DOE and NRC have suspended their  licensing efforts for the Yucca Mountain repository, a great deal of  uncertainty exists about future spent fuel management. Given this  uncertainty, it may be difficult for reactor operators to make decisions  about issues such as the rate of transferring spent fuel to dry storage and  the type of canister to be used for disposal.

		As Many Nuclear Reactors Begin Closing in 2040, Growing Quantities of Spent Fuel May Be Stranded in Place

During the decades it will take to open a storage or disposal facility, many  reactors will be retiring from service, “stranding” their accumulated spent  fuel in a variety of different dry storage systems, with no easy way of  repackaging them should repackaging be required to meet storage or  disposal requirements. Most U.S. reactors were built during the 1960s  and 1970s and, after a 40-year licensing period with a possible 20-year  extension, will begin retiring in large numbers by about 2030 and  emptying their pools by about 2040. NRC regulations require radioactive  contamination to be reduced at a reactor to a level that allows NRC to  terminate the reactor license and release the property for other use after  a reactor shuts down permanently. This cleanup process—known as  decommissioning—costs hundreds of millions of dollars per reactor, and  NRC is responsible for ensuring that operators provide reasonable  assurance that they will have adequate funds to decommission their  reactors. Once a spent fuel pool is removed, reactor operators will have  limited options for managing spent fuel. For example, if reactor operators  need to repackage their spent fuel because a canister has degraded or  because other transportation or disposal requirements must be met, they  will have to build a new spent fuel pool or some other dry transfer facility,  or they will need to ship their spent fuel to another site with a wet or dry  transfer facility.
As of January 2012, the United States had nine decommissioned  commercial nuclear power plant sites. Seven of these plants have  completely removed spent fuel from their pools—a total of 1,748 metric  tons—as well as all infrastructure except that needed to safeguard the  spent fuel. The other two sites, which have a total of 5,103 metric tons  of spent fuel in both wet and dry storage, are in the process of emptying  their pools and transferring all their spent fuel to dry storage.
Assuming that no centralized storage or permanent disposal facility  becomes available, our analysis indicates that by 2040, the amount of  stranded spent fuel in closed commercial nuclear power plants will total  an estimated 3,894 metric tons; by 2045, that amount could increase to  28,751 metric tons; and by 2050, the amount could be 62,237 metric tons.  By 2067, nearly all of the 140,000 metric tons of spent fuel could be  stranded in dry storage. Figure 9 shows the expected pattern of growth  for total accumulated spent fuel compared with that of spent fuel from  decommissioned reactors, or stranded spent fuel.

	The Key Risk of Stored Spent Fuel Is Difficult to Quantify, but Some Mitigating Actions Have Been Taken

According to several studies on spent fuel storage, the key risk of storing  spent fuel at reactor sites is radiation exposure from spent fuel that has  caught fire when it is stored in a pool, but it is difficult to quantify the  probability of such an event. Nuclear reactor operators have put into  place several efforts to mitigate the effects of such a fire, although  disagreement exists on the mitigation needed. In contrast to pool storage,  spent fuel in dry storage is less susceptible to severe radiological  releases. Furthermore, NRC has no centralized database to help identify,  locate, and access classified studies on spent fuel.

		Radiological Release from a Pool Fire Is the Key Risk Posed by Spent Fuel Storage, but Quantifying This Probability Is Difficult

Radiation exposure—from a minor dose resulting from a work-related  accident to a severe, widespread release of radiation from a spent fuel  fire—is the key concern about the hazard of storing spent nuclear fuel.  According to studies we reviewed and NRC officials and representatives  of other groups we spoke with, the worst-case scenario for spent fuel at  reactor sites is the possibility of a self-sustaining fire in a spent fuel pool,  which could engulf all assemblies in the pool, with significant  consequences. According to the analysis in a February 2001 NRC study,  assuming a high release of radiation, the release of spent fuel fission  products resulting from a pool fire could result in nearly 200 early  fatalities, thousands of subsequent cancer fatalities, and widespread land  contamination. These early fatalities could be reduced or eliminated,  according to the study, if the radiation release was less severe and if  there were an early evacuation of the affected population. NRC officials  told us that the assumptions used in that study were very conservative  and that they believed that a lower release of radiation and an early  evacuation are more representative of potential scenarios involving  operating nuclear power reactors. A 2006 National Academy of Sciences  study also found that a spent fuel fire could release large quantities of  radioactive materials into the environment and cause widespread  contamination.
NRC officials, as well as studies by Sandia National Laboratories  (commissioned by NRC) and the National Academy of Sciences (2006),  informed us about the conditions that could lead to a fire. Such a fire  could occur only if enough water in the spent fuel pool were lost, such as  through drainage or boiling away, exposing roughly the top half of the fuel  assemblies. Without sufficient water to keep spent fuel covered and  cool, it is possible that some of the hotter assemblies—those most  recently discharged from a reactor—could ignite. Furthermore, once  started, a fire in a spent fuel pool would be very difficult to extinguish  because, in such a case, the zirconium alloy making up the metal  cladding surrounding the assemblies would react with oxygen and, when  a certain temperature was reached, would begin a chemical reaction that  releases energy and raises the temperature. Essentially, the fire becomes  hotter and self-sustaining and, depending upon the density of spent fuel  in the pool, could spread to other assemblies. On the basis of studies  cited by NRC officials and a Sandia National Laboratories study, a fire in  a fully drained pool can start at about 1,830 degrees Fahrenheit (about  1,000 degrees Celsius). A zirconium fire does not involve flames; rather, it  burns like a welding torch.
A zirconium fire can start only if a complex series of conditions occurs.  NRC and other studies indicate that such a fire is not likely. Furthermore,  the physical protection features and mitigation measures at nuclear power  reactors make the probability of a fire in a spent fuel pool very low. First,  there must be an initiating event, such as an earthquake more severe  than the pool was designed to withstand, an accidental drop of a cask  during dry cask loading operations, or a terrorist attack. Second, the  initiating event must result in a critical loss of water, such as through a  breach in the pool wall or floor that would allow water to drain out. Third,  the reactor operator must be unable to respond adequately to a water  loss, such as being unable to replenish lost pool water sufficiently to cool  the assemblies.
Whether a self-sustaining fire starts and spreads depends on additional  variables, according to Sandia National Laboratories studies  commissioned by NRC from 2003 through 2006 to assess the effects of  some of these variables for pool fires. Two important variables are:
The age and the heat of the spent fuel. Spent fuel is hottest when first  discharged from a reactor but cools relatively quickly. The risk of a  zirconium fire is much greater with recently discharged fuel than with  older fuel.
The size of a hole in the pool and subsequent rate of water drainage.
A Sandia National Laboratories study analyzed the effects of  differently sized holes for various fuel assembly configurations, fuel  ages, ventilation assumptions, and replacement water scenarios, and  this analysis showed that larger holes and drainage rates, all other  factors being equal, resulted in higher temperatures of the fuel  assemblies.
NRC officials told us that, from a regulatory perspective, the risks of an  event causing a large release of radiation that endangers public safety  from spent fuel in either wet or dry storage are low enough to be within  acceptable limits of risk. NRC officials also said the agency considers risk  to be the probability of an event occurring multiplied by the consequences  of that event and has determined that a spent fuel fire is a low-probability,  high-consequence event. In 2001, an NRC study estimated the frequency  of having spent fuel pool assemblies uncovered and exposed to the air to  be, on average, an event that occurs once every 420,000 years. NRC  officials told us the agency did not update its quantitative likelihood  estimates after the September 11, 2001, terrorist attacks. Since  Fukushima Daiichi, NRC has been engaged in ongoing initiatives related  to items such as addressing a loss of off-site electricity and seismic  hazard reevaluation. It has been conducting a study on the consequences  of accident scenarios affecting spent fuel pools and is undertaking a  probabilistic risk assessment to quantify spent fuel risk for a selected  reactor site of interest.
Independent studies we reviewed indicate the difficulty of quantifying the  level of risk of stored spent fuel. Examples of these studies follow:
The Institute for Resource and Security Studies, a Massachusetts- based technical and policy research group, reported in 2009 that the  methodology needed to estimate the probability of nuclear accidents  is complex, requiring consideration of internal and external initiating  events, analyses involving uncertainty, peer review, and estimates of  radiological consequences.
The National Academy of Sciences stated in a 2006 study that the  probability of a terrorist attack on spent fuel storage cannot be  assessed quantitatively or comparatively and that it is not possible to  predict the behavior and motivations of terrorists. This study noted,  and a National Academy of Sciences official expressed concern, that  in the NRC-sponsored studies available when the National Academy  of Sciences was performing its work, NRC did not examine some low- probability scenarios that could result in severe consequences and  that, although unlikely, should be protected against.

		Mitigation Efforts Could Reduce the Likelihood of Severe Consequences, but Disagreement Exists on the Mitigation Needed

Efforts to mitigate safety and security risks could reduce the effects of key  factors in the dynamics of a potential fire in a spent fuel pool, according to  our analysis of Sandia National Laboratories studies on pool fire  scenarios. Still, disagreement exists—largely between community action  groups and NRC—as to the appropriate density of assemblies in a spent  fuel pool.
Storage configurations that disperse the hottest spent fuel assemblies are  among the most important mitigation efforts that Sandia National  Laboratories has identified. NRC and community action groups differ,  however, on the extent to which these efforts should be employed. In  2011, Sandia National Laboratories reported on its study of the safety and  security benefits presented by five different fuel configurations in a  storage pool. According to this study, it is preferable to employ  configurations that place the more recently discharged, hotter assemblies  away from each other—the farther the better—and intersperse them with  older, cooler assemblies or, preferably, with empty adjacent cells. NRC  has provided regulatory guidance to reactor sites to take advantage of  these safer configurations.
Representatives from community action groups we interviewed said that  even with NRC’s mitigation efforts, spent fuel pools remain too densely  packed and that the total amount of spent fuel in the pools should be  reduced by accelerating the transfer of spent fuel into dry storage. In  addition, a 2003 study led by a scholar at a community action group  proposed open rack storage for spent fuel pools. Under this proposal, 20  percent of the pool assemblies would be transferred to dry storage, which  would then allow an open channel on each side of the pool. This  configuration would help promote air convection between the assemblies  and, in turn, reduce the probability of an ignition and subsequent spread  to other assemblies. The fewer assemblies that catch fire, the smaller the  amount of potential radiation that could be released into the  atmosphere.environmental groups collaborated to develop a set of principles for  safeguarding spent fuel. They advocated spent fuel storage policies,  including an open-frame, low-density layout for spent fuel pools and  transfer of this fuel to dry storage within 5 years after its removal from a  reactor. According to NRC, a state regional organization, and  representatives from industry and community action groups, there are  trade-offs between the benefits versus the costs and risks of moving  spent fuel. Nonetheless, no clear agreement exists—according to Sandia  National Laboratories’ analysis and input from community action groups— on the extent to which the density of spent fuel in pools should be  reduced.
Furthermore, in 2006, over 150 community action and  NRC requires nuclear reactor sites to develop and implement strategies  to maintain or restore cooling of reactor cores, containment, and cooling  capabilities for spent fuel pools under circumstances due to explosions or  fire—a requirement that includes providing sufficient, portable, and on-site  cooling equipment. A Sandia National Laboratories study determined that  when holes in pool structure cause significant water drainage, reactor  operators would generally have from a few hours to a few days to replace  lost water or cool spent fuel with sprays in an effort to prevent a fire. If no  water drained, such as in a loss-of-power event that caused a loss of  cooling and allowed the pool water to boil, reactor operators might have  days or weeks. NRC officials said that as spent fuel is uncovered, sprays  are efficient and effective in cooling fuel assemblies. They also told us  that trade-offs exist between installed and portable spray systems.  Installed spray systems can be operated remotely but are susceptible to  damage during an event. Portable systems provide adequate spray and  are stored at least 100 yards away from the pool in secure places, but in  case of an event, reactor operators may not always have access to the  pool area to use them because of radiation hazard or physical  obstruction. According to a member of a community action group we  interviewed, replacement water and sprays may be effective in cooling  spent fuel, but replacement water may not contain boron, which is needed  to absorb neutrons and prevent a critical chain reaction. This member told  us that there is no requirement for reactor operators to keep a supply of  boron to add to replacement water. According to NRC officials, only  operators of pressurized water reactors have the option of adding boron  to the water to prevent a critical chain reaction, but operators of these  reactors must also show that the assemblies will remain sub-critical  without the boron. The NRC officials stated that all reactors are required  to have a 5-percent margin of safety to prevent a critical chain reaction. In  addition to boron in the water, prevention of a critical chain reaction can  also be achieved by boron in plates in the racks, spacing among the  assemblies, and other storage configurations.
After the Fukushima Daiichi nuclear power reactor accident, NRC in  March 2012 supplemented existing requirements by issuing an order  instructing nuclear power operators to install monitoring equipment to  remotely measure a wider range of water levels in spent fuel pools. NRC  issued a second order, also in March 2012, that required reactor  operators to ensure the effectiveness of water mitigation measures. It is  more difficult to provide sprays and replacement water to boiling water  reactor pools because they are typically several stories above ground and  located close to the reactor, whereas spent fuel pools for pressurized  water reactors are at ground level or partially embedded in the ground. At  Fukushima Daiichi, cooling flow to the spent fuel pool was lost during the  loss of off-site power and was not immediately restored with the use of  emergency diesel generators. Emergency operators did not have remote  monitoring equipment to determine whether pool water levels had  dropped enough to expose the spent fuel. Subsequent inspections,  however, determined that water levels did not drop below the top of the  fuel assemblies in the pool.
As we stated in our 2003 report, air ventilation can mitigate the likelihood  of a pool fire in the event of water drainage. Logically, this mitigation  potential depends upon where the ventilation occurs and how much  ventilation can be created. A Sandia National Laboratories study found  that space between assemblies and the pool wall can help promote  ventilation, as can doors and vents in the room where the pool is located.  Space under the assemblies can be created at the foot of racks  supporting fuel assemblies, which allows circulating air to flow up  between the assemblies and carry heat away with it in the event of  complete drainage of water from the pool. However, according to a study  led by a scholar at a community action group, with assemblies packed in  dense configurations in racks at most nuclear reactor pools and boron  plates lining the racks of assemblies, ventilation may be reduced.

		Spent Fuel in Dry Storage Is Less Susceptible to a Significant Radiological Release Than Is Spent Fuel Stored in Pools

Spent nuclear fuel in dry storage is less susceptible to a radiological  release of the magnitude of a zirconium fire in a spent fuel pool,  according to documents we reviewed and interviews we conducted with  officials from NRC, the National Academy of Sciences, and the Nuclear  Waste Technical Review Board; officials from industry; and  representatives of community action groups. Such a release is less likely  for the following reasons:
Spent fuel cools rapidly, and spent fuel in dry storage—typically at  least 5 years old—has cooled sufficiently so that ignition is less likely.  In addition, passive air cooling in dry cask storage systems is not  affected by the loss of off-site power, and active monitoring—other  than ensuring that air vents are not clogged—is not necessary to  prevent overheating and possible ignition.
The amount of radioactive material in a dry storage canister is a  fraction of the amount of radiation in a spent fuel pool. According to  the National Academy of Sciences’ 2006 study, each dry storage  canister contains 32 to 68 fuel assemblies—whereas thousands of  assemblies are typically stored in pools—and therefore each canister  has less radioactive material that can be released than the radiation  from a pool. Logically, breaching dozens of spent fuel canisters  simultaneously could result in more severe consequences than a  single breached canister, but breaching dozens of canisters  simultaneously is difficult.
To trigger any severe off-site radiological release from spent fuel  stored in a canister, the fuel would have to undergo aerosolization,  which would entail breaching the outer and inner shielding units.  Furthermore, any holes would have to be sufficiently large enough to  allow release of the aerosolized spent fuel. It would be difficult to  aerosolize radioactive material in dry storage and difficult to have  some mechanism to transport the radioactive material away from the  reactor site. Such mechanisms would require energy, such as a fire.
Dry storage is not as susceptible to the buildup of hydrogen as are  spent fuel pools. If an accident or attack involving a spent fuel pool  causes a loss of water, the fuel assemblies can heat up and produce  steam. This steam can react with the hot zirconium cladding  surrounding the fuel assemblies, producing hydrogen that, when  mixed with oxygen, could cause an explosion and structural damage  to the reactor building.
As we reported in our 2003 study, NRC had concluded before September  11, 2001, that spent fuel in dry cask storage systems was considered  safe and secure. A Sandia National Laboratories study conducted from  2003 through 2005, supplemented by NRC analyses, evaluated several  representative types of dry cask storage designs against airplane and  ground attacks to determine if any other security measures were needed,  in addition to those already issued by order. This work did not find that  any further mitigating or security procedures were needed for nearly all  the scenarios, but it did identify some potential scenarios in which some  radiation could be released.
This study helped inform NRC’s technical evaluation—first discussed  internally at NRC in 2007, according to NRC officials, and published for  solicitation of public comments in 2009. This evaluation included a  proposal to establish a security-based dose limit that would require  owners of spent fuel in dry storage systems to develop site security  strategies to protect against a potential radiological release that exceeds  NRC’s acceptable dose limits at a site boundary. NRC issued this  evaluation for public comment for a proposed rule to revise security  requirements for storing spent fuel away from a reactor. During the public  comment period, NRC received general comments showing a preference  for guarding against a specific threat rather than the dose-based  approach proposed in the technical evaluation. For example, under the  dose-based approach, some owners told NRC that they might have to  increase their security forces to prevent potential radiological releases,  and they raised concerns about the cost of such efforts compared with  the benefit. As a result, according to NRC officials, the agency has  delayed the proposed rule in order to gather more information regarding  the public comments. NRC officials told us the agency plans to  commission additional studies to help assess the situation and determine  the appropriate security strategy.

		NRC Has No Centralized Mechanism to Help Identify, Locate, and Access Classified Studies on Spent Fuel

In conducting our work, we found that NRC does not have a mechanism  to ensure that it can easily identify and locate all classified studies  conducted over the years. When we requested classified and other  studies from NRC officials, it was difficult for them to provide us with the  information we requested in a timely manner. Specifically, nearly 5  months elapsed from our initial request for classified studies of wet  storage until NRC provided these documents. A National Academy of  Sciences official told us that the academy had also experienced difficulty  in obtaining some of NRC’s classified studies while performing its 2004  study. To identify studies, we interviewed numerous NRC and other  officials and identified studies through references in other studies we  reviewed. NRC officials said the classified studies are stored in the safes  of NRC officials. We also contacted officials from Sandia National  Laboratories and requested a list of all their studies on spent fuel safety  and security. NRC officials told us that developing and maintaining a  classified database covering the most important topics involving spent  fuel, as designated by agency management, would not be burdensome.
Managing spent fuel until permanently disposed of may take many  decades, and NRC and DOE managers and staff and operators with  appropriate clearances may need to review an extensive number of  classified studies conducted for NRC on the safety and security of spent  fuel. Several studies conducted after September 11, 2001, by NRC and  other groups referred to NRC studies conducted before that date—some  conducted as early as 1979. We also found decades-old NRC studies to  still be useful in our review. The nature and characteristics of spent fuel  discharged from a reactor likely will not change, and therefore the  underlying principles and knowledge of spent fuel safety and security are  likely to remain applicable and informative to future scientists and others.  Although preserving key scientific and technical studies is important,  preservation of information alone is not enough if others may not be  aware of a study’s existence or location. Scientists and others rely on  mechanisms that allow them to easily identify, locate, and access  pertinent information, as well as to prevent unnecessary duplication of  research.

	Transfer of Spent Fuel from Wet Storage Offers Benefits but Also Presents Challenges

Transferring spent fuel from wet to dry storage is generally safe and  offers several key benefits, but any movement of spent fuel entails some  level of risk. Accelerating the transfer of spent fuel from wet to dry storage  to reduce the inventory of spent fuel in a pool could increase those risks.  Additional operational and other challenges to accelerating the transfer of  spent fuel to dry storage may limit the degree of acceleration that may  ultimately be achieved. Once spent fuel is in dry storage, additional  challenges may arise, such as costs for repackaging should it be needed.

		Transferring Spent Fuel from Wet to Dry Storage Offers Benefits

The transfer of spent fuel from wet to dry storage and long-term storage  at reactor sites, although not originally part of the plan for managing spent  fuel, has offered some benefits, according to our analysis of documents  and interviews with NRC officials, representatives from industry, and  community action and environmental groups. For example, without a  permanent means of disposing of spent nuclear fuel for at least several  decades, the transfer of spent fuel from pools to dry storage has provided  the nation with time to develop a more permanent solution. We previously  reported—on the basis of input from experts—that dry storage is  considered safe for at least 100 years and is easily retrievable.
Moreover, because most spent fuel pools are nearly at capacity, reactor  operators must transfer as much spent fuel to dry storage as is  discharged from the reactor. According to our analysis of input from these  officials and representatives, accelerating the transfer of spent fuel from  wet to dry storage may offer the following additional benefits:
Reducing the potential consequences of pool fires. An accelerated  transfer of spent fuel to dry storage may return the pools to a low- density, open-frame configuration that could reduce potential  consequences should an unintended release of radiation occur from a  pool fire. Accelerated transfer has been advocated by more than 150  community action and environmental groups.
Potentially increasing the volume of transportation-ready spent fuel.  Accelerating the transfer of spent fuel to dry storage could increase  the volume of readily transportable spent fuel for ease of removal to  an off-site facility for storage, reprocessing, or disposal, with the  caveat that reactor operators take steps to ensure that canisters and  their contents meet transportation requirements.
In addition, we note that once a reactor is decommissioned, spent fuel is  less expensive to safeguard in dry storage than in wet storage.  Specifically, we previously reported that the cost of operating a spent fuel  pool at a decommissioned reactor could range from about $8 million to  nearly $13 million a year but that the cost of operating a dry storage  facility might amount to about $3 million to nearly $7 million per year.  Nine reactor sites nationwide are currently shut down and partly  decommissioned and have already transferred all their spent fuel to dry  storage or are in the process of doing so, with plans to remove their spent  fuel pools. A tenth site never had an operating reactor but was built as an  interim storage pool in anticipation of reprocessing. The operators of  this site have not announced any plans to transfer spent fuel to dry  storage.

		Accelerating Transfer of Spent Fuel from Wet to Dry Storage Presents Challenges and Some Risk

Accelerating the transfer of spent fuel from wet to dry storage entails  some operational challenges, and some industry representatives told us  that they have questioned whether the cost of overcoming these  challenges is worth the benefit, particularly considering the low probability  of a catastrophic release of radiation. Furthermore, in a 2003 response to  a recommendation by the Institute of Policy Analysis to accelerate the  transfer of spent fuel from wet to dry storage to reduce the likelihood and  potential consequences of a pool fire, NRC reported that accelerating the  transfer of spent fuel is not justified, particularly given the billions of  dollars it will cost, with no appreciable increase in safety. In commenting  on a draft of this report, NRC reiterated this position, stating that it does  not require the accelerated transfer of spent fuel to dry storage,  particularly considering the small increase in safety that could be  achieved, because it considers both wet and dry storage to be safe under  current regulations.
The studies that NRC provided to us on the safety and security of spent  fuel did not include any comprehensive analysis of the advantages and  disadvantages of accelerating the transfer of spent fuel from wet to dry  storage. However, NRC officials stated that the commission is currently  evaluating accelerated transfer of spent fuel to dry storage as part of a  larger review of lessons learned from the Fukushima event. The officials  stated that the evaluation will allow NRC to determine whether regulatory  action is needed to require accelerated transfer of spent fuel. NRC  officials have stated that they believe they can complete their planned  evaluation within about 5 years. Some of the challenges from accelerating  the transfer of spent fuel include the following:  Increasing the need for skilled workers and potential radiation doses  to those workers. Workers at reactors face radiation exposure during  routine transfer of spent fuel from wet to dry storage, particularly  during loading operations, but this risk could increase if transfer were  accelerated, according to a 2010 analysis by EPRI. The institute  estimated worker exposure rates, assuming transfer of spent fuel in  generic reactors both at the rate of current practice and at an  accelerated rate. At the rate of current practice, EPRI reported,  workers would collectively receive a dose of 15,836 rem over a nearly  90-year period associated with transferring the expected inventory of  about 140,000 metric tons from wet to dry storage, performing  annual maintenance and inspection of the dry storage systems, and  constructing additional dry storage systems if additional dry storage  capacity is needed. Assuming an accelerated rate of transfer after 5  years of cooling, EPRI calculated that worker dose would increase by  507 rem, or 3 percent, as a result of the transfer, maintenance and  inspection, and construction duties performed over the same 90-year  period. Assuming worker exposure rates would remain roughly the  same, the additional 507 rem under an accelerated transfer scenario  would represent the equivalent of an estimated 1,500 workers.  Furthermore, EPRI has reported that industry is moving to high-burn- up fuel for greater efficiency. But this high-burn-up fuel is hotter and  more radioactive than conventional fuel and requires cooling for about  7 years before it can be safely transferred to dry storage. If transfer is  accelerated, this high-burn-up fuel could potentially increase worker  dose.
NRC, A Survey of Crane Operating Experience at U.S. Nuclear Power Plants from 1968  through 2002, NUREG-1774 (Washington, D.C.: July 2003). assemblies or the pool liner, potentially leading to water drainage. A  single fuel assembly from a boiling water reactor weighs about 700  pounds, and a single fuel assembly from a pressurized water reactor  weighs about 1,500 pounds; dry storage casks, once fully loaded, can  weigh from 100 to 180 tons or more. NRC has provided guidance to  industry to take steps to minimize damage from such a drop, such as  using overhead cranes with special added safety features so that a  single failure will not result in dropping a damaging load or developing  handling routes designed to avoid lifting heavy loads over vulnerable  equipment.44,
Working within time constraints. Timing preferences and operational  limitations could constrain how much spent fuel is transferred in a  given year and may present an obstacle to accelerated transfer from  wet to dry storage. Industry representatives told us that under current  practice, reactor operators prefer to transfer spent fuel to dry storage  during periods of time that do not interfere with refueling, receiving  new fuel, required inspections, and maintenance or other activities  vital to plant operations. These activities typically consume about 8 to  9 months of each year’s calendar. A routine dry storage loading  operation may take 2 months or more, according to industry  representatives. For example, one industry representative told us that  it can take about 2 weeks to mobilize workers and equipment before  the operation and about 2 more weeks to demobilize after the  operation. Additionally, according to industry representatives at one  operating reactor site we visited, each canister takes about 1 week to  load, dry, seal, and move to a storage pad, which limits the number of  canisters that can be loaded in a given year. In addition, spatial  limitations—such as space for drying or welding lids onto multiple  canisters, limited heavy lifting capabilities, and lack of free space in  spent fuel pools to accommodate more than one cask at a time—may  make simultaneous loading of canisters difficult. Some industry  representatives we spoke with told us that there are limits on how  much acceleration can be achieved in a single year.
NRC, Single-Failure-Proof Cranes for Nuclear Power Plants, NUREG-0554  (Washington, D.C.: May 1979).
NRC, Control of Heavy Loads at Nuclear Power Plants: Resolution of Generic Technical  Activity A-36, NUREG-0612 (Washington, D.C.: July 1980).
Increasing costs. The transfer of spent fuel from wet to dry storage is  costly in several ways. We estimated in a November 2009 report that  the transfer cost for about five canisters is about $5.1 million to  $8.8 million. One industry representative told us that if the transfer of  spent fuel to dry storage were accelerated, the associated high up- front costs could strain some nuclear power plants’ budgets. These  up-front costs, which would be incurred over a longer period without  acceleration, include the construction of a storage pad with  accompanying safety and security features, which, we reported, could  cost about $19 million to $44 million. These costs are initially borne  by ratepayers or plant owners but may be passed on to taxpayers as  a result of industry lawsuits against DOE for failure to take custody of  the spent fuel. Moreover, EPRI reported that as older, cooler spent  fuel is loaded into canisters, reactor operators eventually will be left  with younger, hotter spent fuel to transfer from wet to dry storage.  Spent fuel stored in canisters generally should not exceed about  752 degrees Fahrenheit (400 degrees Celsius), and, as we reported  earlier, spent fuel being discharged from reactors today may have to  cool at least 7 years before it can be placed in dry storage. Given the  heat load requirements for storing spent fuel, EPRI noted that it may  not be possible to fill some canisters to capacity. Specifically, a  canister with a capacity for 60 boiling water reactor assemblies that  would store 60 older, cooler assemblies may be able to contain only  38 younger, hotter assemblies.

		Managing Spent Fuel after Transfer from Wet to Dry Storage at Reactor Sites Presents Additional Challenges

Reactor operators had never intended to leave spent fuel on their sites for  extended periods, but even if the United States began to develop an off- site centralized storage or disposal facility today, spent fuel—which has  already been stored on-site for several decades—would be stored on-site  for several decades more. As a result, the following challenges could  affect decisions on managing spent fuel.
Repackaging stranded spent fuel. Once reactors are decommissioned,  reactor operators have limited options for managing the stored spent fuel.
Specifically, once they package the spent fuel in canisters and dry casks,  they are unlikely to have any means of repackaging if the canisters  degrade over the long term, or if the operators have to meet different  storage or disposal requirements. As we previously reported, experts told  us that canisters are likely safe for at least 100 years, but by then the  spent fuel may have to be repackaged because of degradation. By the  time such repackaging might be needed, reactor operators may no longer  have pools or the necessary infrastructure to undertake the repackaging,  as was the case at the Haddam Neck site we visited. Specifically, the  Haddam Neck site had already decommissioned the reactor, transferred  all its spent fuel from wet to dry storage, and dismantled its spent fuel  pool. If the spent fuel at the site needed to be repackaged, a special  transfer facility would need to be built, or the spent fuel would need to be  shipped to a site that had a transfer facility. In addition, to reduce costs,  reactor operators are selecting a variety of dry storage systems that  maximize storage capacity. These varied systems do not raise safety  issues, but they may complicate a transfer to a centralized storage facility  or a permanent disposal facility because different systems require  different handling requirements, such as the type of grappling hook and  the size of the transport cask required. These differences may present  more complex engineering challenges and cost issues as time passes,  and the volume of spent fuel in various systems increases. In addition,  over time, it is possible that handling equipment would not be maintained  and personnel would not continue to be trained. Maximizing storage  capacity may raise additional engineering challenges and cost issues,  particularly since larger canisters may meet storage requirements but not  transportation requirements. The Nuclear Energy Institute has reported  that of all the spent fuel currently in dry storage, only about 30 percent is  directly transportable. It also reported that the remaining spent fuel could  need as much as 10 more years of cooling to meet NRC’s transportation  heat-load requirements to ensure that assemblies can withstand the force  of a potential accident.
Reducing community opposition. As reactors begin to be closed down  and decommissioned, reactor operators will leave spent fuel on sites that  will serve no other purpose than storing that fuel. Continued on-site  storage would likely face increasing community opposition, which could  make it difficult for operators to obtain NRC recertification for storage  sites at reactors, approval for licenses to extend the operating life of other  reactors, or licenses for new reactors. According to officials from a state  regional organization we spoke with, the longer the federal government  defers a permanent disposition pathway for spent fuel, the less likely the  public would be to accept interim solutions, for fear such solutions would  become de facto permanent solutions. Also, in our prior work, experts  noted that many commercial reactor sites are not suitable for long-term  storage and that none have had an environmental review to assess the  impacts of storing spent fuel beyond the period for which the sites are  currently licensed. As discussed above, in June 2012, a federal  appellate court remanded NRC’s waste confidence determination and  rule for the preparation of an environmental impact statement or finding of  no significant environmental impact.
Managing costs. Continued storage of spent fuel may be costly. Because  owners of spent fuel would have to safeguard it beyond the life of  currently operating reactors, decommissioned reactor sites would not be  available to local communities and states for alternative development.  The Blue Ribbon Commission recommended that the nation open one or  more centralized storage facilities and put a high priority on transferring  the so-called stranded spent fuel to free decommissioned reactor sites for  other uses. We previously reported the cost of developing two federal  centralized storage facilities to be about $16 billion to $30 billion, although  this estimate does not include final disposal costs, which could cost tens  of billions of dollars more. In addition, we also previously reported that if  spent fuel needs to be repackaged because of degradation, repackaging  could cost from $180 million to nearly $500 million, with costs  depending on the number of canisters to be repackaged and whether a  site has a transfer facility, such as a storage pool.
A license is required for delivery of licensed material to a carrier for transport or for the  transport of licensed material. 10 C.F.R. § 71.3 (2012). after transportation because of uncertainties over the condition of large  amounts of high-burn-up fuel that might have to be repackaged for  disposal. As a result, NRC stated that until further guidance is developed,  the transportation of high-burn-up fuel will be handled on a case-by-case  basis using the criteria given in current regulations. Without a  standardized cask design for storage, transportation, and disposal, it may  be difficult to design the type of large-scale transportation program  needed to transfer high-burn-up fuel away from reactor sites.
Maintaining security over the long term. Future security requirements for  the extended storage of spent fuel are uncertain and could pose  additional challenges. Specifically, before the September 11, 2001,  terrorist attacks, spent nuclear fuel was largely considered to be self- protecting for several decades because its very high radiation would  prevent a person from handling the material without incurring health or  life-threatening injury in a very short time, although incapacitating health   In addition, as  impacts may sometimes not occur for up to 16 hours. spent fuel decays over time, it produces less decay heat. A spent fuel  assembly can lose nearly 80 percent of its heat 5 years after it has been  removed from a reactor and 95 percent of its heat after 100 years. Given  the willingness of terrorists in recent years to sacrifice their lives as part of  an attack, the national and international communities have begun to  rethink just how long spent fuel really might be self-protecting. As spent  fuel ages and becomes less self-protecting, additional security  precautions may be required.
Continuing taxpayer liabilities. The continued on-site storage of spent fuel  will not alleviate industry’s lawsuits against DOE for failure to take  custody of the spent fuel in 1998 as required by contracts authorized  under the Nuclear Waste Policy Act of 1982, as amended. DOE estimates  that the federal government’s liabilities resulting from the lawsuits will be  about $21 billion through 2020 and about $500 million each year after  that. These costs are paid for by the taxpayer through the Department of  the Treasury’s Judgment Fund.
The International Atomic Energy Agency, DOE, and NRC have considered spent fuel to  be self-protecting with a radiation level exceeding 100 rad—or, radiation absorbed dose, a  unit of measurement—per hour at 1 meter unshielded. After short-term exposure to 250 to  500 rad, about 50 percent of the people coming in contact with the spent fuel would be  expected to die within 60 days.

	Conclusions

The decades-old problem of where to permanently store commercial  spent nuclear fuel remains unsolved even as the quantities of spent  fuel—in either wet or dry storage—continue to accumulate at reactor sites  across the country. It is not yet clear where a repository will be sited, but it  is clear that it may take decades more to site, license, construct, and  ultimately open a disposal site. In the interim, some scientists,  environmentalists, community groups, and others have expressed  growing concerns about the spent nuclear fuel that is densely packed in  spent fuel pools, especially after the water in the pools at the Fukushima  Daiichi nuclear power plant complex in Japan were at risk of being  depleted, increasing the risk of widespread radioactive contamination.  The chances of a radiation release are extremely low in either wet or dry  storage, but the event with the most serious consequences—a self- sustaining fire in a spent fuel pool—could result in widespread radioactive  contamination. NRC has studied the likelihood of such an event and has  taken a number of steps to prevent a fire, including a number of mitigating  measures, though some community action groups have raised questions  if those steps are enough, given the severity of consequences.
Moreover, because storage or disposal facilities may take decades to  develop, in managing spent fuel, NRC and DOE officials and others with  appropriate clearances and a need to know may need to review classified  studies conducted by and for NRC on the safety and security of spent  fuel. These studies are likely to be relevant for decades and, therefore,  continue to contribute to institutional knowledge and the ultimate  decisions made concerning the handling and storage of spent nuclear  fuel. Nevertheless, NRC does not have a mechanism that allows for easy  identification and location of classified studies conducted over the years.  Without such a mechanism, it may be difficult and time-consuming to  access the necessary studies.

	Recommendation for Executive Action

To help facilitate decisions on storing and disposing of spent nuclear fuel  over the coming decades, we recommend that the Chairman of the  Nuclear Regulatory Commission direct agency staff to develop a  mechanism that allows individuals with appropriate clearances and the  need to know to easily identify and access classified studies so as to help  ensure that institutional knowledge is not lost.

	Agency Comments

We provided NRC with a draft of this report for review and comment. In  written comments, which are reproduced in appendix IV, NRC generally  agreed with the findings and the recommendation in our report. NRC did  note, however, that our characterization of NRC’s position to not require  accelerated transfer of spent fuel to dry storage was factually incorrect.  Specifically, NRC stated that we characterized its position on accelerated  transfer as being solely a cost-benefit decision. NRC stated that it does  not require accelerated transfer because it considers both wet and dry  storage to provide a safe means of storing spent fuel that is in full  conformance with agency regulations. We clarified the report language to  more clearly state NRC’s position. Regarding the recommendation, NRC  stated that it planned to review its internal procedures to determine if any  measures need to be taken to ensure the classified information is readily  available to future decision makers. NRC also provided technical  comments, which we have incorporated as appropriate.
As agreed with your offices, unless you publicly announce the contents of  this report earlier, we plan no further distribution until 30 days from the  report date. At that time, we will send copies to the Chairman of the  Nuclear Regulatory Commission, the Secretary of Energy, appropriate  congressional committees, and other interested parties. In addition, the  report will be available at no charge on the GAO website at  http://www.gao.gov.
If you or your staff members have any questions about this report, please  contact me at (202) 512-3841 or aloisee@gao.gov. Contact points for our  Offices of Congressional Relations and Public Affairs may be found on  the last page of this report. Key contributors to this report are listed in  appendix V.

Appendix I: Scope and Methodology

To determine the amount of spent fuel projected to accumulate before it  can be moved from individual reactor sites, we obtained data from the  Nuclear Energy Institute, an industry advocacy organization, on current  inventories of commercial spent nuclear fuel in wet and dry storage and a  database on year-to-year projections of on-site spent fuel accumulation in  wet and dry storage. We developed the projections of this amount on the  basis of several assumptions, including that all 104 reactors would renew  their licenses for 20 years, with the early shutdown of Oyster Creek, in  New Jersey, 10 years before its license expires; that no new reactors are  brought online; that the nation’s current reactors continue to produce  spent fuel at the same rate; and that all spent fuel remaining in wet  storage would be moved to dry storage 12 years after a reactor’s final  shutdown. As part of our analysis, we obtained information in reports and  from interviews from the Nuclear Regulatory Commission (NRC); the  Department of Energy (DOE); the Electric Power Research Institute, a  nonprofit research entity; and representatives from industry, academia,  and community action and environmental groups. To assess the reliability  of existing data, we reviewed available documentation and conducted  interviews with individuals knowledgeable about the data. On the basis of  this information, we found these data to be sufficiently reliable for the  purposes of our report.
To determine the most likely options for moving spent fuel off-site, we used  prior work that had analyzed the Yucca Mountain program and its most  likely alternatives to help us assess three scenarios: (1) Yucca Mountain,  (2) two federally funded central storage facilities, and (3) a new permanent  disposal facility. We used assumptions from our prior work, including  updating dates from our assumptions, and we supplemented these  assumptions by reviewing documents and interviewing officials from federal  and state regional organizations and representatives from industry,  independent groups, and community action and environmental groups.  Specifically, for the Yucca Mountain option, we asked DOE how long it  would take for a repository at Yucca Mountain to open if licensing were to  resume in 2012, assuming the license and funding were both approved.  DOE told us that the best way to develop a new estimate would be to take  the estimates that existed before the program was shut down and add the  time elapsed between when DOE stopped work on licensing and when it  may resume licensing, which is 10 years. We previously reported, however,  that DOE’s original estimate for licensing was likely too optimistic.  Furthermore, because all of DOE’s former Yucca Mountain program staff  have been assigned to other offices, left the agency, or retired, some  delays are likely in reassembling a licensing team—as much as 2 years,  according to one former DOE official familiar with the Yucca Mountain  program. Given these challenges, we added 5 additional years to DOE’s  original 10-year estimate of completing Yucca Mountain. If licensing for the  Yucca Mountain program were to resume in 2012, the earliest possible  opening date is roughly 2027. For the two federal centralized storage  facilities, we updated dates we developed for a prior report, in which we  projected when the centralized storage facilities might be built, which was  19 years. Since these are rough estimates, we rounded the time frame to  20 years, meaning that if the process were started in 2012, the earliest that  two federal centralized storage sites could open would be 2032. For a new  repository, we analyzed DOE’s actual and projected time frames for  licensing and opening the Yucca Mountain repository and DOE’s report to  Congress on the time frames necessary to open a second repository. We  also analyzed the time frames necessary to open the nation’s only high- level radioactive disposal facility, the Waste Isolation Pilot Plant in New  Mexico. On the basis of our analysis, we determined that if a process were  started in 2012 to open a new repository, it could open in about 40 years,  or 2052.
To determine key safety and security risks of spent fuel, as well as  potential mitigation actions, we reviewed NRC-commissioned studies  performed by Sandia National Laboratories and studies by NRC, the  National Academy of Sciences, community action groups, and industry.  Our primary period of focus was post-September 11, 2001, which  included studies from 2002 to 2009, but we also reviewed pre-September  11, 2001, studies dating back to 1979. We identified relevant studies for  review by asking officials from NRC, DOE, and Sandia National  Laboratories, as well as knowledgeable persons whom we interviewed,  and by reviewing the citations in these studies to identify still other  relevant studies. We reviewed studies of spent fuel pools and dry casks  at the classified, NRC safeguards, official use only, and unclassified  levels. In addition, we toured the Haddam Neck decommissioned reactor  site and the Millstone reactor in Connecticut, the Hope Creek and Salem  reactors in New Jersey, and the Susquehanna reactor in Pennsylvania,  and we spoke with NRC officials and industry representatives about wet  and dry spent fuel storage issues, including potential mitigation actions, at  these sites. Our site visits included decommissioned and operating  reactor sites, sites with both pressurized water reactors and boiling water  reactors, sites having both wet and dry storage, and sites using both  vertical and horizontal dry storage systems. We also reviewed NRC  requirements addressing the safety and security of spent fuel, as well as  directives from the nuclear power industry.
To determine the benefits and challenges of transferring spent fuel from  wet to dry storage, including transferring this fuel at an accelerated rate,  we reviewed prior GAO reports and documents from NRC, DOE, the  Nuclear Waste Technical Review Board, the National Academy of  Sciences, the Blue Ribbon Commission on America’s Nuclear Future,  academia, industry, and community action and environmental groups. We  also interviewed officials from NRC, DOE, and state regional  organizations, and representatives of industry, academia, the Blue  Ribbon Commission on America’s Nuclear Future, and community action  and environmental groups. We spoke with industry representatives and  NRC inspectors at the decommissioned and operating reactor sites we  visited. In our interviews, we asked for their views on the benefits and  challenges of transferring spent fuel from wet to dry storage and the  benefits and challenges of accelerating that transfer. To further determine  the cost considerations for transferring spent fuel from wet to dry storage,  we updated cost component estimates developed for our 2009 report to  constant 2012 dollars. In that report, we obtained information from a small  group of experts to develop initial assumptions, which we then provided to  a larger set of nearly 150 experts for comment.
We conducted this performance audit from June 2011 to August 2012, in  accordance with generally accepted government auditing standards.  These standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives.

Appendix II: Selected Other Countries’ Spent Fuel Management Programs

Like the United States, other countries produce electricity from nuclear  power reactors and have programs to manage their spent nuclear fuel.  Table 2 provides a brief description of the programs in selected countries.

Appendix III: Accumulation of Commercial Spent Fuel by State over Time

Our report identified three scenarios in which spent fuel could be moved  to an off-site location. Briefly, the earliest likely opening date if the Yucca  Mountain repository were to be licensed and constructed is about 2027,  the earliest a centralized storage facility could be expected to open is  about 2032, and the earliest a permanent disposal facility that was an  alternative to Yucca Mountain could be expected to open is about 2052.  Table 3 summarizes the amount of spent fuel that is expected to  accumulate in each state for these dates, as well as 2012—the current  spent fuel accumulation—and 2067, when all currently operating  commercial nuclear power reactors are expected to have retired and  transferred their spent fuel to dry storage. The table also shows the rank  for each state in terms of the amount of its accumulated spent fuel in  comparison with the other states.

Appendix IV: Comments from the Nuclear Regulatory Commission

Appendix V: GAO Contact and Staff Acknowledgments

	GAO Contact

	Staff Acknowledgments

In addition to the individual named above, Janet E. Frisch (Assistant  Director), Antoinette Capaccio, Virginia Chanley, Ellen W. Chu, Randall  Cole, R. Scott Fletcher, Cristian Ion, Mehrzad Nadji, Kevin Remondini,  Robert Sánchez, Carol Shulman, Kiki Theodoropoulos, and Franklyn Yao  made key contributions to this report.

Summary:
Why GAO Did This Study

Spent nuclear fuel, the used fuel removed from nuclear reactors, is one of the most hazardous substances created by humans. Commercial spent fuel is stored at reactor sites; about 74 percent of it is stored in pools of water, and 26 percent has been transferred to dry storage casks. The United States has no permanent disposal site for the nearly 70,000 metric tons of spent fuel currently stored in 33 states. GAO was asked to examine (1) the amount of spent fuel expected to accumulate before it can be moved from commercial nuclear reactor sites, (2) the key risks posed by stored spent fuel and actions to help mitigate these risks, and (3) key benefits and challenges of moving spent nuclear fuel out of wet storage and ultimately away from commercial nuclear reactors. GAO reviewed NRC documents and studies on spent fuels safety and security risks and industry data, interviewed federal and state government officials and representatives from industry and other groups, and visited reactor sites.

What GAO Found

The amount of spent fuel stored on-site at commercial nuclear reactors will continue to accumulateincreasing by about 2,000 metric tons per year and likely more than doubling to about 140,000 metric tonsbefore it can be moved off-site, because storage or disposal facilities may take decades to develop. In examining centralized storage or permanent disposal options, GAO found that new facilities may take from 15 to 40 years before they are ready to begin accepting spent fuel. Once an off-site facility is available, it will take several more decades to ship spent fuel to that facility. This situation will be challenging because by about 2040 most currently operating reactors will have ceased operations, and options for managing spent fuel, if needed to meet transportation, storage, or disposal requirements, may be limited.
Studies show that the key risk posed by spent nuclear fuel involves a release of radiation that could harm human health or the environment. The highest consequence event posing such a risk would be a self-sustaining fire in a drained or partially drained spent fuel pool, resulting in a severe widespread release of radiation. The Nuclear Regulatory Commission (NRC), which regulates the nations spent nuclear fuel, considers the probability of such an event to be low. According to studies GAO reviewed, the probability of such a fire is difficult to quantify because of the variables affecting whether a fire starts and spreads. Studies show that this low-probability scenario could have high consequences, however, depending on the severity of the radiation release. These consequences include widespread contamination, a significant increase in the probability of fatal cancer in the affected population, and the possibility of early fatalities. According to studies and NRC officials, mitigating procedures, such as replacement water to respond to a loss of pool water from an accident or attack, could help prevent a fire. Because a decision on a permanent means of disposing of spent fuel may not be made for years, NRC officials and others may need to make interim decisions, which could be informed by past studies on stored spent fuel. In response to GAO requests, however, NRC could not easily identify, locate, or access studies it had conducted or commissioned because it does not have an agencywide mechanism to ensure that it can identify and locate such classified studies. As a result, GAO had to take a number of steps to identify pertinent studies, including interviewing numerous officials.
Transferring spent fuel from wet to dry storage offers several key benefits, including safely storing spent fuel for decades after nuclear reactors retireuntil a permanent solution can be foundand reducing the potential consequences of a pool fire. Regarding challenges, transferring spent fuel from wet to dry storage is generally safe, but there are risks to moving it, and accelerating the transfer of spent fuel could increase those risks. In addition, operating activities, such as refueling, inspections, and maintenance, may limit the time frames available for transferring spent fuel from wet to dry storage. Once spent fuel is in dry storage, there are additional challenges, such as costs for repackaging should it be needed. Some industry representatives told GAO that they question whether the cost of overcoming the challenges of accelerating the transfer from wet to dry storage is worth the benefit, particularly considering the low probability of a catastrophic release of radiation. NRC stated that spent fuel is safe in both wet and dry storage and that accelerating transfer is not necessary given the small increase in safety that could be achieved.

What GAO Recommends

To help facilitate decisions on storing and disposing of spent nuclear fuel over the coming decades, GAO recommends that NRC develop a mechanism for locating all classified studies. NRC generally agreed with the findings and the recommendation in the report.