Spent Nuclear Fuel: Options Exist to Further Enhance Security
Published: 2003-07-15T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: Spent nuclear fuel, the used fuel periodically removed from nuclear power reactors, is one of the most hazardous materials made by man. Nuclear power companies currently store 50,000 tons of spent fuel at 72 sites in 33 states. That amount will increase through 2010, when the Department of Energy (DOE) expects to open a permanent repository for this fuel at Yucca Mountain, Nevada. Concerns have been raised since September 11, 2001, that terrorists might target spent fuel. GAO was asked to (1) review federally sponsored studies that assessed the potential health effects of a terrorist attack or a severe accident on spent fuel, either in transit or in storage, and (2) identify options for DOE to further enhance the security of spent fuel during shipping to Yucca Mountain.
section_title: What GAO Found
paragraphs: The likelihood of widespread harm from a terrorist attack or a severe accident involving commercial spent nuclear fuel is low, according to studies conducted by DOE and NRC. Largely because spent fuel is hard to disperse and is stored in protective containers, these studies found that most terrorist or accident scenarios would cause little or no release of spent fuel, with little harm to human health. Some assessments found widespread harm is possible under certain severe but extremely unlikely conditions involving spent fuel stored in storage pools. As part of its ongoing research program and to respond to increased security concerns, NRC has ongoing and planned studies of the safety and security of spent fuel, including the potential effects of more extreme attack scenarios, including deliberate aircraft crashes. While NRC and DOE have found that spent fuel may be relatively safe and secure, DOE could potentially enhance the security of this fuel through options such as minimizing the number of shipments and picking up fuel in an order that would reduce risk, such as moving older less dangerous fuel first. These options could reduce the risk during transport and at some locations where the fuel is currently stored. However, contractual agreements between DOE and owners of spent fuel may limit DOE's ability to choose among these options. In addition, it is not clear that the benefits of these measures would justify the potential costs, including a possible renegotiation of the contracts between DOE and the spent fuel owners.

section_title: Letter
paragraphs: One of the most hazardous materials made by man is spent nuclear   fuel—the used fuel periodically removed from reactors in nuclear power  plants. Without protective shielding, the fuel’s intense radioactivity can kill  a person exposed directly to it within minutes or cause cancer in those  who receive smaller doses. As the fuel ages, it begins to cool and becomes  less radiologically dangerous—some of the radioactive particles decay  quickly, within days or weeks, while others exist for many thousands  of years. Currently, more than 50,000 tons of commercial spent fuel are  stored at 72 sites at or near nuclear power plants in 33 states. Most of this  nuclear fuel is stored immersed in pools of water designed to cool the fuel,  but some sites also keep older, cooler fuel in “dry storage” units that  generally consist of steel containers placed inside reinforced concrete  vaults or bunkers. Concerns about the security of these sites and their  spent fuel inventories have been raised following the terrorist attacks of  September 11, 2001.
To provide secure, permanent disposal for spent fuel, the President  and the Congress have approved development of a deep underground  repository at Yucca Mountain, Nevada. The Department of Energy (DOE)  is to construct and operate the repository after receiving a license from the  Nuclear Regulatory Commission (NRC). Shipping this fuel from current  storage locations to Yucca Mountain will be managed by DOE, which in  1983 entered into contracts with owners of spent fuel (essentially owners  and operators of nuclear power plants) requiring DOE to take title to and  dispose of this fuel. DOE estimates that 175 shipments per year over  24 years will be required to move the accumulated inventory of spent  nuclear fuel. These shipments have increased public concern about  nuclear security. Recent media reports suggest that if terrorists could  release spent fuel into the environment during transit or from wet or dry  storage sites, particularly near large cities, the human health effects could  be severe.
We agreed with your office to (1) review federally sponsored studies that  examined the potential health effects of a terrorist attack or a severe  accident involving commercial spent nuclear fuel, either in transit or in  storage, and (2) identify options for DOE to enhance the security of  spent fuel as it develops its plans to ship the fuel to Yucca Mountain. In  conducting our review, we did not assess the reliability of data or the  methodologies used in the studies that examined potential health effects.  We also did not examine economic or broader environmental effects of  terrorist attacks or severe accidents, nor did we examine the effectiveness  of certain other safety and security measures, such as the effectiveness of  armed guards and intrusion barriers.
subsections: section_title: Background
paragraphs: Fuel for nuclear power plants consists of fingernail-sized pellets of  uranium dioxide, a radioactive compound. The pellets are fitted into  hollow metal rods, typically constructed of zirconium alloy, and the rods  are then gas pressurized. The rods are generally 12 to 14 feet in length and  are bundled together into assemblies. A portion of the assemblies must be  replaced every 1 to 2 years as the fuel in the reactor expends energy,  becoming less efficient at producing heat. As part of the process of  expending energy during a nuclear reaction, the fuel becomes highly  radioactive and thermally hot. Spent fuel emits radiation as a consequence  of radioactive decay. Barriers such as thick walls, sealed containers, and  water are used to shield individuals from exposure to this radiation.
NRC regulates not only the construction and operation of commercial  nuclear power plants but also the storage, transportation (together with  the Department of Transportation), and disposal of spent fuel. NRC  requires each operating nuclear power plant to have safety and security  programs. For example, NRC requires protective shielding and security  systems, including armed guards, at nuclear power plants. When spent  fuel assemblies are removed from a reactor, they are stored in large  pools of cooling water. These pools are constructed according to NRC’s  requirements, typically with 4- to 6-foot thick steel-lined concrete walls  and floors. Pools are typically 30 to 60 feet long, 20 to 40 feet wide, and  40 feet deep. The location of these pools is dependent on the type of  reactor. Essentially, all commercial power reactors in the United States  are one of two types, either a boiling water reactor or a pressurized water  reactor. For most boiling water reactors, the pools are located close to the  reactors, several stories above ground. For pressurized water reactors, the  pools are located in structures outside the reactor building, on the ground  or partially embedded in the ground. Regardless of reactor type, these  pools are required by NRC to be constructed to protect public health  against radiation exposure, even after a natural disaster, such as an  earthquake. The water in the pool is constantly cooled and circulated, and  the fuel assemblies are generally 20 feet below the surface of the water.
In 1982, through the Nuclear Waste Policy Act, the Congress directed DOE  to construct an underground repository for disposal of spent fuel and  other high-level radioactive waste. The Congress amended the act in 1987  and required DOE to only consider Yucca Mountain, Nevada, as a potential  site for a repository. In 2002, the President recommended to the Congress,  and the Congress approved, Yucca Mountain as a suitable site for the  development of a permanent high-level waste repository. As we reported  in 2001, for a variety of reasons, DOE is unlikely to open the repository as  planned in 2010.
Lacking a long-term disposal option now, some nuclear utilities must  move a portion of their spent fuel into dry storage or face shutting down  their plants because their wet pools are reaching capacity. Currently, 25 of  the 72 storage sites use dry storage, and 11 other sites have plans to move  some of their inventory of spent fuel into dry storage. Dry storage facilities  for spent fuel typically consist of steel containers that are placed inside  concrete vaults or bunkers where the fuel is cooled by air rather than  water. These storage systems are required by NRC to be capable of  protecting against radiation exposure and of surviving natural disasters.  Because the move to dry storage is time-consuming and expensive,  utilities are, wherever possible, modifying wet pool storage capacity so  they can store larger quantities of spent fuel in these pools.
To expose a large number of people to the harmful effects of radiation  from spent fuel, the fuel would have to be released from its protective  containers and dispersed over a wide or densely populated area. However,  unlike many other hazardous materials, spent fuel is a hard, heavy ceramic  material that is neither explosive nor volatile. To achieve a wide dispersal,  some portion of the spent fuel assemblies would have to be pulverized into  small particles by an external force—such as a high-speed impact or a  violent explosion—or some portion of the spent fuel assemblies would  have to burn in a sustained, high-temperature fire. According to NRC,  the redundancy and robustness of the designs of the fuel containers  make wide dispersal highly unlikely. In the event of a dispersal, the most  significant health effects would involve persons who inhaled very small  (respirable) particles—10 microns or less in diameter. Such particles  would be absorbed into the body and possibly remain there for  many years. In addition, these particles could be deposited on buildings  and the ground where, in the absence of a costly cleanup effort, they could  expose people to elevated levels of radiation.
The transportation of spent fuel to Yucca Mountain—most likely by both  truck and rail, but with a preference for using mostly rail—will be a major  undertaking, spanning 20 to 30 years. According to DOE, more than  50,000 tons of the spent fuel have accumulated at 72 sites in 33 states,  many located near urban areas in the Midwest and the East. DOE has  estimated that the accumulated inventory will have grown to 69,000 tons  by 2010 and that moving this volume could require approximately  175 shipments per year over 24 years, relying on a combination of truck  and rail shipments.
For the transportation of spent fuel, NRC has certification and inspection  requirements for shipping containers to ensure that the containers protect  against radioactive releases under accident scenarios. NRC has certified  a number of shipping container designs for use on trucks and rail. The  Nuclear Waste Policy Act of 1982, as amended, requires DOE to ship  spent nuclear fuel and high-level radioactive waste to Yucca Mountain  in containers that have been certified by NRC. The act also requires DOE  to notify NRC in advance of spent fuel and high-level radioactive  waste shipments.
In addition to NRC, the Department of Transportation plays a role in  regulating the transportation of spent fuel and other high-level waste. The  department’s Research and Special Programs Administration sets certain  safety standards for the transportation of hazardous materials, including  spent fuel. These standards include, among other things, documentation  and labeling of containers, including placards identifying the shipment,  and requirements for separating certain radioactive materials while in  transit. The Federal Motor Carrier Safety Administration oversees the  safety of shipments by highway, and the Federal Railroad Administration  oversees the safety of shipments by rail. The U.S. Coast Guard oversees  the safety of shipments that may be made by barge.
section_title: Likelihood of Widespread Harm from Terrorist Attacks or Severe Accidents Involving Spent Fuel Is Low
paragraphs: Studies conducted by NRC and DOE have consistently found that the  likelihood of widespread harm to human health from a terrorist attack or  a severe accident involving spent fuel is very low. None of the studies  involving the transportation of spent fuel or dry storage of spent fuel  identified a scenario resulting in widespread harm—largely because of  the protective containers required by NRC. For example, these studies  repeatedly found that transportation containers would be very difficult to  penetrate, and in the worst-case scenarios where they may be penetrated,  only a small fraction of the material would be released. Some studies  involving spent fuel stored in pools of water found that widespread harm  is possible under severe but unlikely accident conditions. Such conditions  may include a catastrophic earthquake or a severe but unlikely accident  that could uncover the fuel for several hours, possibly allowing it to  spontaneously ignite and scatter radioactive material over a wide area.  To respond to increased security concerns stemming from the  September 11, 2001, terrorist attacks, NRC is further studying the safety  and security of spent fuel in transit and in wet or dry storage, including  the potential effects of more extreme attack scenarios such as deliberate  aircraft crashes.
subsections: section_title: Shipping Containers Protect against Widespread Release of Fuel in Transit
paragraphs: Since the late 1970s, federal studies have examined the effects of both  terrorist acts of sabotage and severe accidents involving shipping  containers for spent fuel. Sabotage studies have sought to determine  whether radioactive material could be released from shipping containers  in specific sabotage scenarios, while accident studies have assessed  whether radioactive material could be released in a variety of accidents,  and the overall probability of their occurrence. Some of these studies were  commissioned by NRC, and others by DOE, and many of them were  conducted through DOE’s Sandia National Laboratory and other DOE  laboratories. These studies collectively indicate that the construction of  the shipping containers helps to limit releases. Although NRC is confident  in these results, it is sponsoring assessments to further validate computer  models and address heightened security concerns.
subsections: section_title: Sabotage Studies
paragraphs: The most recent sabotage study—conducted by DOE’s Sandia National  Laboratory for DOE in 1999—estimated the amounts and characteristics of  releases of radioactive materials from truck and rail spent fuel containers  subjected to two different types of weapons. The results of this study  confirmed the findings of earlier studies that armor-piercing weapons  could penetrate shipping containers and release small quantities of  radioactive material. The study found that, under a worst-case scenario,  the weapon could penetrate a shipping container and release a small  amount of material—equal to about 0.016 of 1 percent of the spent fuel in  the container—as small, respirable particles. These small, respirable  particles could become airborne and spread beyond the immediate vicinity  of the attack.
A subsequent DOE-sponsored report used the results of the 1999 Sandia  National Laboratory study to estimate the human health impact of the  most severe release. Using a computer-based analytic model and  conservative assumptions, DOE’s contractor found that the predicted  release from a truck container would cause about 48 cancer deaths over  the long term and that a predicted release from a rail container would  cause about 9 cancer deaths over the long term. DOE’s contractor’s  analysis explained that these cancer deaths should be considered against  a backdrop of an expected 1.1 million cancer deaths among the same  population expected from other causes. This analysis assumed that the  release would occur in an urban area with a population projected to the  year 2035 under stable weather conditions. The analysis also assumed that  the spent fuel release would contain twice the radioactive content of a  typical spent fuel shipment and that there would be no evacuation or  cleanup of the affected area for 1 year after the incident.
These studies are the most recent in a series of studies dating back to  the 1970s. According to NRC and DOE officials, confidence in the results  of these studies has increased significantly as better data and more  sophisticated analytic techniques have been used. Appendix II contains a  fuller description of the methodology of these recent studies and the  results of previous studies.
section_title: Accident Studies
paragraphs: Since the 1970s NRC has also sponsored a series of studies examining  the risk that spent fuel could be released during transportation accidents.  NRC’s most recent assessment of spent fuel transportation accident risks  was conducted for NRC by Sandia National Laboratory and was published  in 2000. The 2000 Sandia National Laboratory study, like preceding  accident studies, found that an accidental release of spent fuel in transit  is very unlikely and that significant human health impacts are even less  likely. The study estimated that in over 99.9 percent of all truck and rail  accidents, the shipping container would experience no significant damage,  and no radioactive material would be released. In fact, the analysis found  that only 7 in 100,000 (0.007 of 1 percent) truck accidents and 4 in 100,000  (0.004 of 1 percent) rail accidents would involve spent fuel casks in  impacts or fires that might cause a release of radioactive material. While  this study did not project the human health impacts of particular accident  scenarios, it concluded that the overall risk of human exposure to  accidental releases of spent fuel was far less than that estimated in the  1977 study, which confirmed that NRC’s safety and security regulations  then in place were adequate.
A subsequent DOE-sponsored study used the results of the 2000 Sandia  National Laboratory study to determine the potential health effects of the  estimated quantity of material released. DOE’s contractor used the  estimated amount of material released in what DOE determined as the  most severe reasonably foreseeable accident to estimate the number of  latent cancer fatalities that could result from severe accidents while  shipping spent fuel to the Yucca Mountain repository. From this study,  DOE concluded that this type of accident—having a probability of  occurring about 2.8 times in 10 million accidents per year—could cause  about 5 long-term latent cancer fatalities—far less than its estimate of  48 latent cancer deaths in the event of a successful sabotage attack with  armor-piercing weaponry. Apart from this type accident, DOE found that  the probability of any deaths due to an accidental release of radiation was  quite small. DOE’s final environmental impact statement for Yucca  Mountain projected that accidents over 24 years of shipping would cause  fewer than 0.001 latent cancer fatalities. In contrast, DOE projected that  these same shipments had a much greater probability of resulting in  deaths due to normal traffic accidents—between 2.3 and 4.9 traffic  fatalities over the same 24-year period.
As with the sabotage studies, these studies of accident scenarios are the  most recent in a series of studies dating back to the 1970s. According to  NRC and DOE officials, confidence in the results of these studies has  increased significantly as better data and more sophisticated analytic  techniques have been used. Appendix II contains a fuller description of the  methodology of these recent studies and the results of previous studies.
section_title: Ongoing and Planned Assessments
paragraphs: Although NRC believes that the results of the federally sponsored studies  are valid, it has several evaluations ongoing and planned to further assess  its security and safety measures. To assess its existing security measures  following the September 11, 2001, terrorist attacks, NRC initiated a  commissionwide review. As part of this review, NRC commissioned  Sandia National Laboratory to examine more severe terrorist attack  scenarios involving spent fuel shipping containers. For example, the  laboratory will assess the effects of (1) a 20-passenger aircraft loaded with  explosives crashing into shipping containers and (2) a sustained attack on  these containers using a variety of weapons in combination.
As part of an ongoing process to assess its safety measures, NRC has a  number of ongoing and planned studies. NRC commissioned Sandia  National Laboratory for further validation of computer models used to  evaluate the safety of shipping containers. To solicit comments on the  scope of its evaluation, NRC held a series of public meetings beginning in  1999. It considered comments obtained during these meetings and issued  an interim report in 2002 that recommended several additional studies.  Although these studies are still being designed, their preliminary  objectives include (1) validating past computer-based predictions of  damage to containers resulting from collisions, (2) validating past  computer-based predictions of how well containers withstand fires, and  (3) identifying the response of fuel pellets, fuel rods, and fuel assemblies in  severe impacts. In contrast to past analyses of severe accident scenarios,  the studies are to include physical tests of full-scale current model  shipping containers. The results of these physical tests will be compared  to the predictions of past computer-based analyses and serve to either  validate or to correct those results. The studies are also to address some of  the technical issues that were not adequately addressed by past accident  analyses. For example, while past studies relied on expert judgment to  assess the complex chain of variables involved in releasing respirable  spent fuel from containers—including fracturing spent fuel rods and  pellets—the planned studies will examine these events experimentally.
According to NRC officials, the studies are expected to be completed  by 2006.
section_title: Widespread Release from Wet Storage Theoretically Possible but Unlikely
paragraphs: NRC studies have reported that a risk of widespread harm to human  health from spent fuel arises from the remote possibility of a sustained  loss of coolant in a spent fuel pool. Such a loss could potentially lead to a  fire that would disperse radioactive material across a wide area. NRC’s  most recent published study of this risk, released in 2001, found that,  though the potential consequences of such a fire could be severe—nearly  200 early fatalities and thousands of latent cancer fatalities—the likelihood  of such a fire is low. The study estimated that a catastrophic earthquake  or a severe but unlikely accident, such as dropping a 100- to 150-ton  storage container into the pool, could precipitate a pool fire.
The study was conducted to assess the risks associated with accidents  at nuclear reactors that have been permanently shut down. According to  NRC, once the fuel is removed from the reactors, there is a risk associated  with the fuel stored in pools. NRC designed the study with conservative  assumptions to identify the most severe possible impact on public health.  The study assessed a variety of natural disasters and accidents that could  drain coolant and cause a fire. These events included loss of electrical  power, which would shut down the pool cooling system; an event that  would significantly damage the pool cooling system; a drop of a heavy  load, which could damage the pool wall or floor; a severe earthquake;  and an accidental aircraft crash. The study found that a catastrophic  earthquake and a heavy load drop were the events most likely to  significantly damage the pool, leading to sustained loss of coolant and  potentially causing a fire.
The study then calculated the amount of radioactive material that might  be released by a fire and the possible human health effects stemming from  exposure to this material. In making these calculations, the study made  various conservative assumptions to ensure that NRC identified the most  severe consequences possible. For example, the study assumed that a pool  fire would involve 100 percent of the spent fuel assemblies in the pool,  releasing large amounts of radioactive material into the atmosphere.
Two of the authors of the study noted that it was not certain how many  spent fuel assemblies would actually burn in a fire. The uncertainty in  the amount of radioactive material released depends on the fuel age and  distribution in the pool and the characteristics of the accident scenario.  The authors noted that some spent fuel assemblies might not reach the  high temperatures required to burn and that some of the radioactive  material might remain trapped in the pool or building. Because spent fuel  decays and thus becomes less dangerous over time, the study evaluated  scenarios in which the reactor had been shut down for 30 days, 90 days,  1 year, 2 years, 5 years, and 10 years. For each scenario, the study  evaluated two levels of radioactivity released from the fuel. NRC used the  results of this study to calculate the potential health effects of a fire in a  spent fuel pool. These results are shown in table 1.
The study noted that the results are based on a natural disaster or an  accident severe enough to lead to a pool fire and that the risk of such an  event occurring is very low. NRC also noted that part of the reason for  the low probability is NRC’s defense-in-depth policy, which states that  NRC establishes requirements to ensure that safety will not be wholly  dependent on any single system. Instead, NRC’s requirements ensure  multiple or redundant safety systems. In the case of the storage pool  studied in the 2001 report, NRC noted that several factors combine to  make a pool fire unlikely, including the robust design of the pool; the  simple nature of the pool support systems; and the long time required to  heat up the fuel, which allows time for operators to respond. For  example, according to the 2001 report, heating the least-decayed spent fuel  to the ignition point—were it to occur at all—would take hours, perhaps  even days. Thus, NRC officials explained that even if a massive loss of  coolant occurred, plant operators might still have time to react, depending  on the extent of the damage. NRC requires that nuclear power plants have  a backup water supply that can cool fuel in case of an accident, so,  depending on the extent of damage, plant operators might be able to keep  the fuel submerged.
The risk of a pool fire is also limited by the ability of some of the fuel to  be cooled by simple air ventilation if the coolant drains out. According to  NRC, completely draining a pool may allow enough air ventilation among  the stored fuel assemblies so that the spent fuel would stay below the  ignition point of a self-sustaining fire (about 1,650 degrees Fahrenheit).  Furthermore, even if a fire did begin in one assembly, there is considerable  uncertainty about whether the fire would spread to other assemblies. A  1987 study of spent fuel pools found that spent fuel in pools with fewer  assemblies, after being cooled for just a few weeks, would not ignite if  subjected to loss of coolant. Under the dense storage conditions  characterized by most spent fuel pools today, however, air ventilation  becomes less effective.
subsections: section_title: NRC Continues to Study the Risks of Storing Spent Fuel in Pools
paragraphs: To begin addressing some of the uncertainties regarding the risks of  storing spent fuel in wet storage pools, NRC has some ongoing work, and  recently completed some initial evaluations of sabotage attacks on these  pools, and has more work planned and ongoing at two DOE national  laboratories. Following the terrorist attacks of September 11, 2001, NRC  commissioned the U.S. Army Corps of Engineers to examine potential  effects of sabotage directed at spent fuel pools. The Corps conducted  several computer-based analyses of the potential effects of armor-piercing  weapons and high explosives on typical spent fuel pools. The analyses  found that the penetration of armor-piercing weapons and high explosives  could vary considerably, depending, among other things, on the size of the  weapon or explosive and the sophistication of the attacker.
NRC is also conducting studies with less conservative assumptions to  more realistically evaluate the risks of spent fuel in a drained pool. NRC  has contracted with Argonne National Laboratory to study the conditions  necessary to ignite a pool fire. NRC has also contracted with Sandia  National Laboratory for a series of studies to define potential threats, and  to identify potential vulnerabilities, regulatory improvements or legislative  initiatives to improve security and safety and better protect public health.  The studies by Sandia National Laboratory include a review of a variety of  terrorist scenarios, including attacks on fuel pools with aircraft and high  explosives. According to NRC, preliminary results of these studies indicate  that spent fuel may be more easily cooled than has been predicted in some  past studies and that off-site radiological releases may be substantially  reduced from previous worst-case estimates. Predicted public health  effects might also be substantially reduced for the worst scenarios where  coolant is lost and recovery actions are not successful in cooling the fuel.
section_title: Dry Storage Containers Safeguard against Widespread Release
paragraphs: Dry storage containers, like shipping containers, pose a considerable  barrier to releasing spent fuel. Used to store spent fuel when it is removed  from wet storage, dry storage containers are constructed of layers of steel  and radiation barriers such as concrete. In establishing regulations for  dry storage of spent fuel, NRC stated in 1998 that dry storage containers  are structurally similar to shipping containers and that the results of  sabotage studies on shipping containers could reasonably be applied to  dry storage containers. Nevertheless, NRC is continuing to study potential  risks of releases from dry storage containers.
Studies by DOE and the Corps on dry storage containers have generally  reached the same conclusion—that the thick walls of the containers,  consisting of an inner steel container and an outer steel or concrete  container, could not be penetrated by airplane crashes and would result in  no significant release of radiation when attacked with advanced weapons.  Two DOE-sponsored reports, released in 1998 and 2001, found that  airplane crashes would not penetrate dry storage containers. The reports  focused on the most penetrating components of the commercial jet  aircraft: the engines and landing gear. Both reports concluded that  although airplane crashes could damage the containers, no radioactive  material would be released. The analysis showed that the containers  would break up the airplane, spreading jet fuel over a wide area,  causing the jet fuel to dissipate or burn without affecting the spent fuel  in the containers.
Two other studies, performed in 2001 by the Corps, found that the  containers would not release significant amounts of radioactive  material when attacked by armor-piercing weapons or high explosives.  The study examining the effect of armor-piercing weapons found that the  penetration to the containers was very limited. NRC and DOE officials and  independent experts told us that, based on a previous analysis and similar  studies involving shipping containers, the weapons would not likely cause  a significant release. The study examining the effects of high explosives  found that the explosives would not completely penetrate the container.  The study showed extensive exterior damage, but no penetration to the  spent fuel.
subsections: section_title: NRC Continues to Study Risks to Dry Storage Containers
paragraphs: NRC is continuing to study potential risks to dry storage. NRC has  contracted with Sandia National Laboratory to assess the vulnerability of  dry storage containers to terrorist attacks, including a further analysis  of aircraft crashes and the effects of high explosives. In addition, the  laboratory will investigate measures to mitigate any vulnerability identified  through the assessment.
section_title: Options May Exist to Further Enhance Security and Safety
paragraphs: As DOE develops its plans for shipping spent fuel to the Yucca Mountain  repository, the agency has several potential options for enhancing the  security of spent fuel during the Yucca Mountain shipping campaign.  Specifically, DOE could potentially minimize its total number of spent  fuel shipments, ship the fuel in an order that reduces risk, or transport the  fuel on railroad trains dedicated exclusively to hauling spent fuel. Not all  of these options may be feasible under the terms of DOE’s contracts with  spent fuel owners, and some options for shipping in a particular order  would conflict with one another.
subsections: section_title: Minimizing Number of Shipments
paragraphs: DOE could enhance the overall security of spent fuel by minimizing the  total number of shipments. Fewer shipments would present fewer  potential targets for terrorists and could also enhance safety because there  would be fewer chances for an accident. Representatives of the nuclear  power industry and nuclear safety experts that we contacted agreed on  these points. For example, a representative of a consortium of nuclear  utilities told us that shipping spent fuel by rail is preferable to shipment  by truck because spent fuel containers designed for rail can carry about  5 times more spent fuel than truck containers. This larger capacity  translates to fewer shipments overall. Similarly, a frequent critic of the  safety of spent fuel shipments agreed that fewer shipments would be  better, noting that fewer, large shipments are easier to protect and track.  Beyond expressing a preference for shipping spent fuel to Yucca Mountain  mostly by rail, DOE has not yet developed its plans to implement the  shipping campaign.
In addition to providing security advantages, minimizing the number  of shipments by using rail provides safety and efficiency benefits.  According to a 1998 Department of Transportation report, rail was the  safer mode for shipping large amounts of spent fuel. The report states  that minimizing trips usually reduces total risk by reducing risks  associated with routine radiation exposure—such as the incidental  exposure experienced by transportation and plant workers while shipping  containers are being prepared—as well as accident-related exposure and  other nonradiation accident consequences.
DOE’s ability to minimize the total number of shipments may be limited  by its contracts with owners of spent fuel. Under the contracts, DOE is to  establish a shipping queue, in which each utility has shipping rights based  on the date and quantity of fuel removed from a reactor. In many cases,  the places in the queue correspond to quantities of spent fuel that would  fill less than three large rail containers—an amount that, according to the  Association of American Railroads, would be a reasonable size for a  single rail shipment. If strictly followed, the queue could result in many  more shipments than necessary. For example, the 12 spent fuel owners  with the largest quantities of spent fuel would make approximately  576 shipments based on the shipping queue. On the other hand, if these  12 owners consolidated all their shipments into rail containers and used  3 containers per shipment, they could reduce their total shipments to 479,  a 17 percent reduction. If these same owners consolidated shipments  into 5 rail containers per shipment, which according to DOE is another  possible option, total shipments could be reduced to 287—a nearly  50 percent reduction.
section_title: Order in Which Spent Fuel Is Shipped Could Enhance Security
paragraphs: DOE could also enhance security by shipping spent fuel in an order  that minimizes risk. There are at least three shipping orders that would  potentially reduce risk: (1) shipping fuel from shutdown nuclear reactors  first, reducing the number of sites storing spent fuel; (2) shipping the  oldest and least radiologically dangerous fuel first to reduce transportation  risk; or (3) shipping fuel from storage pools first, reducing the likelihood  of a pool fire. Shipping fuel first from shutdown nuclear reactors would be  permissible under DOE’s contracts with fuel owners, but the contracts  might preclude the other two options. Further, to some extent, these  options conflict with one another. For example, an emphasis on shipping  fuel from spent fuel pools first could leave some older fuel in dry storage  at current storage facilities. Data are not available to determine which  order would provide the greatest risk reduction.
subsections: section_title: Shipping Fuel from Shutdown Reactor Sites First
paragraphs: DOE could potentially enhance the overall security of spent fuel by  first shipping fuel currently stored at shutdown nuclear reactor sites.  Currently, about 4,100 tons of spent fuel—about 8 percent of the total  stored nationwide—are stored at 14 shutdown nuclear reactors. Because  nine of these sites will not be accumulating additional spent fuel, clearing  their spent fuel inventory would eliminate them as potential targets of a  terrorist attack.
DOE recognized the potential importance of removing spent fuel from  shutdown reactors when it established its contracts for disposal of spent  fuel. Although the contracts establish a shipping queue, the contracts  allow DOE to override the queue to make an exception for spent fuel  from shutdown reactors. Specifically, the contracts provide that,  notwithstanding the age of spent fuel, priority may be accorded any spent  fuel removed from a civilian nuclear power reactor that has reached the  end of its useful life or has been shut down for whatever reason.
section_title: Shipping Oldest Fuel First
paragraphs: DOE could lower the risk of transporting spent fuel by shipping the  oldest spent fuel first. Radioactivity emitted by some components of spent  fuel declines significantly over comparatively short periods of time. For  example, one of the more radioactive elements in spent fuel—cobalt— accounts for about 90 percent of the gamma radiation emitted by spent  fuel when it is first removed from the reactor. However, after about  25 years, cobalt, a  comparatively volatile element that would be a major component of any  accidental or deliberate release, declines by half after 30 years. Shipping  older spent fuel first could therefore be preferable in the event of a  deliberate or accidental release during transit. For example, a release of  spent fuel that is 25 or 30 years old would be a lesser—though still  significant—threat to public health than fuel that is only 5 or 10 years old.
Analyses performed for DOE’s environmental impact statement for the  Yucca Mountain repository illustrate the reduced impact that a release  of older spent fuel can have on public health. In the draft environmental  impact statement, DOE estimated that a particular release due to a  sabotage attack could result in about 16 latent cancer fatalities. This  scenario assumed that the shipped fuel was about 23 years old, which is  approximately the average age of the inventory of spent fuel. The final  environmental impact statement analyzed the same scenario, except that it  assumed that the shipped fuel was about 15 years old. This analysis found  that such a release would cause about 48 latent cancer deaths—3 times as  many as the older fuel. The age of the fuel was one of two major factors  that resulted in the higher estimate of latent cancer fatalities in the final  statement. DOE noted that the younger, more dangerous fuel, such as  spent fuel discharged 5 years or less from a reactor, makes up a small  percentage of the total inventory of spent fuel. As a result, the youngest,  hottest fuel would be less likely to be shipped or would represent a small  fraction of the fuel that is shipped. requires about 704 million years for its radiation output to be cut  in half. shipping older spent fuel first. An analyst under contract with the state  of Nevada noted that shipping the oldest fuel first would be the most  important factor in protecting public health during transit. Not only would  older fuel have lower consequences if released in an accident or a terrorist  event, but it also would be safer for transportation workers—drivers and  handlers at intermodal transfer points—and the general public. A  representative of the National Research Council’s Board on Radioactive  Waste Management told us that shipping the oldest fuel first would help  minimize potential human health consequences in the event of a release  during transit. However, this representative said that if one assumes that  the robust shipping containers make a release unlikely, the potential risk  reduction associated with the age of the fuel becomes less important.
Regardless of the potential transportation-related security benefits, DOE’s  contracts with spent fuel owners limit its ability to ship the oldest fuel  first. In addition to establishing a shipping queue, the contracts allow each  fuel owner discretion to decide which of its spent fuel is actually delivered  to DOE, commensurate with the quantity of fuel associated with a  particular spot in the queue. For example, the Exelon company—the  nation’s largest nuclear power company—has a place in the queue for  about 35 tons of spent fuel removed from a reactor located at its plant in  Zion, Illinois. When the time comes to ship this fuel to the repository,  Exelon may deliver either this fuel or an equal quantity of fuel—possibly  much younger and more radioactive fuel—from any of its facilities located  at sites in Illinois and sites in Pennsylvania and New Jersey.
Because owners have discretion to choose which fuel they will actually  ship under the terms of the contract, DOE does not have the ability under  the contract to require that oldest fuel be shipped first. Fuel owners will  likely select spent fuel for shipment based on their operational needs. For  example, representatives of Progress Energy, a fuel owner with reactors in  the Southeast, said they would will likely ship from their pools first  because their pools are reaching capacity. Similarly, an Exelon official  said that shipping from pools first would minimize the need for dry  storage facilities.
section_title: Shipping Fuel from Densely Packed Pools First
paragraphs: As discussed in the first section of this report, a fire in a wet storage pool,  while highly unlikely, is theoretically possible. Shipping spent fuel from  densely packed spent fuel pools first could have security benefits.  Because DOE has not yet opened a permanent repository, spent fuel has  accumulated in quantities that pools were not originally designed to  contain. NRC officials noted that while a few spent fuel pools have low  density in at least part of the pools, nearly all pools are densely packed.
These densely packed pools contain as much as 3.5 times more spent  fuel on average than the pools were originally designed to store. Reducing  the density of spent fuel in the pools would reduce the likelihood of a  fire. Recent NRC and independent studies show that lower-density  configurations allow for greater spacing between assemblies, which allows  air to more efficiently circulate in the event of coolant loss. According  to these reports, greater spacing could also help prevent a fire from  spreading among assemblies. Also, in the unlikely event of a fire, fewer  assemblies in the pool could result in reduced consequences.
As noted earlier, DOE’s contracts limit its ability to influence the order in  which spent fuel is shipped. Some owners may prefer to ship fuel from  densely packed pools first because when the pools reach full capacity, the  fuel must be removed or the plant must shut down. To the extent that, as  Exelon and Progress Energy officials stated, utilities are likely to ship from  their wet pools first, the threat would be reduced earliest at these pools.  This would, however, result in a relatively higher threat during transport  from relatively younger, more radioactive, spent fuel. It is not clear  whether this will be a common preference.
section_title: Shipping Fuel on Trains That Haul Only Spent Fuel
paragraphs: According to some analysts, DOE could enhance the security of spent  fuel shipments by using trains dedicated to carrying only spent fuel.  Such trains would typically consist of three to five rail cars, carrying one  container of spent fuel per car. A truck shipment can carry 1 to 2 tons of  spent fuel. In contrast, depending on the containers used, a 3-car train can  carry from 50 to 65 tons of spent fuel and a 5-car train can carry from  about 80 to 110 tons of spent fuel. Although dedicated trains could  enhance the security and safety of spent fuel shipments, these benefits  would have to be weighed against potential drawbacks. The benefits  would also have to be weighed against constructing a rail line to Yucca  Mountain. Currently, no rail line extends to Yucca Mountain.
Advocates of dedicated trains told us that such trains offer two primary  security and safety advantages. First, the use of dedicated trains would  significantly reduce the exposure of spent fuel shipments to a terrorist  attack by significantly shortening the trip duration from its point of origin  to the repository. A representative of the Association of American  Railroads, which recommended that DOE use dedicated trains for the  shipment of spent fuel, explained that a spent fuel shipment from the East  Coast to Nevada would take about 3 to 4 days by dedicated rail, while the  same trip by regular rail would take about 8 to 10 days. Specifically, spent  fuel transported by regular rail would spend significant amounts of time in  rail yards where trains are broken up and reconfigured. While in the rail  yards, spent fuel containers could be stationary targets.
Second, using dedicated trains would ensure that spent fuel was not  shipped with flammable hazardous materials. If spent fuel were released  from its containers in an accident or a terrorist attack, a fire fueled by  flammable materials could spread radioactive material over a wide area.  For example, NRC recently issued an analysis regarding a rail tunnel  fire that occurred in Baltimore in July 2001 that involved more than  28,000 gallons of a flammable solvent. NRC estimated that temperatures as  high as 1,800 degrees Fahrenheit were reached at certain locations in the  tunnel during the course of the fire but found that temperatures averaged  900 degrees in other parts of the fire. NRC studied the potential effects of  this fire on a spent fuel transportation container carrying spent fuel and  concluded that, when subjected to similar fire conditions, the container  would not release radioactive material.
According to transportation officials we spoke to, dedicated trains can  also have safety and other benefits beyond sabotage prevention. For  example, officials of the Union Pacific Railroad and the Association of  American Railroads said that combining cars carrying fully loaded spent  fuel containers on trains with those carrying other cargo raises operational  and safety issues. Rail cars carrying spent fuel rail containers are  extraordinarily heavy—such a car weighs about 470,000 pounds compared  to about 200,000 pounds for a standard loaded rail car. This weight  differential introduces difficulties in the physical dynamics of a train  carrying spent fuel and other cargo, making derailments more likely.
On the other hand, it is not clear that the advantages of dedicated trains  outweigh the additional costs. In 1980, while considering amendments to  its security regulations, NRC examined the case for requiring dedicated  trains for rail shipments of spent fuel. NRC noted the advantages of  dedicated trains but also noted that dedicated trains are no more capable  of avoiding high-population areas than are regular trains, that a regular  train in a rail yard would be under surveillance by escorts and railroad  police, and that the necessary physical protection measures can be as  easily implemented on regular trains as on dedicated trains. For these and  other considerations, NRC declined to require dedicated trains. Further,  although DOE recognized the possible advantages of shipping spent  nuclear fuel by dedicated trains, DOE also concluded in its final  environmental impact statement that available information does not  indicate a clear advantage for the use of either dedicated trains or general  freight service.
section_title: Conclusions
paragraphs: The events of September 11, 2001, elevated lingering public concerns  about the security of spent fuel, and in particular the security and safety  of large-scale shipping of spent fuel. NRC and DOE studies show a low  likelihood of widespread harm to human health from terrorist attacks or  severe accidents involving spent fuel. Nonetheless, DOE could potentially  take a number of measures to further enhance the security and safety of  the shipping campaign to Yucca Mountain. It is not clear whether the  additional security and safety benefits such measures offer are worth  the additional costs and effort—possibly including a renegotiation of  contracts that DOE has established with the nation’s utilities—that they  would entail. In addition, it is not clear which of these measures—some of  which conflict with each other—would provide the greatest safety and  security benefit. However, we believe they should be explored.
section_title: Recommendations for Executive Action
paragraphs: To ensure that all reasonable options to further enhance the security and  safety of spent fuel in storage at nuclear power plants and in transit are  explored, we recommend that the Secretary of Energy assess the potential  benefits and costs of (1) minimizing the total number of shipments of  spent fuel by consolidating shipments where possible, (2) shipping spent  fuel in an order that further minimizes risk, and (3) emphasizing the use of  trains dedicated to hauling spent fuel.
section_title: Agency Comments and Our Evaluation
paragraphs: We provided DOE and NRC with drafts of this report for review and  comment. DOE generally concurred with the facts of the report, noting  that the information on transit was accurate and well balanced. DOE also  concurred with our recommendations, with one exception. DOE noted  that the Department of Transportation was expected to release a study  later this year on the safety and security implications of transporting spent  fuel by dedicated train. DOE stated that it preferred to wait for the  outcome of the study before beginning its own review. DOE also provided  technical comments, which we incorporated into the report.
NRC also generally concurred with the facts of the report, noting that  the information provides a reasonable characterization of the current  understanding of risks associated with spent fuel storage. However, NRC  stated that it does not consider the results of its most recently published  studies on spent fuel in a pool and spent fuel in transit, as quoted in the  report, to accurately reflect the consequences of a potential terrorist  attack. Rather, NRC indicated that the studies started with overly  conservative assumptions, resulting in “unrealistically conservative”  results. NRC noted that it is currently conducting studies to assess the  potential consequences of a terrorist attack that use more realistic  assumptions. NRC also noted in its technical comments that preliminary  results from these ongoing studies show that potential consequences may  be far less severe than reported in the current publications.
We revised our report to account for NRC’s preliminary findings from  ongoing work involving the risk associated with spent fuel pools. As our  report states, these findings indicate that risks from spent fuel pools  may be substantially reduced from previous estimates. We used NRC’s  February 2001 report, Technical Study of Spent Fuel Pool Accident Risk  at Decommissioning Nuclear Power Plants, with the understanding that  the report received a high level of scrutiny both within and outside NRC  prior to its publication. As stated in the report, “Preliminary drafts of this  study were issued for public comments and technical reviews in June 1999  and February 2000. Comments from interested stakeholders, the Advisory  Committee on Reactor Safeguards, and other technical reviewers have  been taken into account in preparing this study. A broad quality review  was also carried out at the Idaho National Engineering and Environment  Laboratory, and a panel of human reliability analysis experts evaluated the  report’s assumptions, methods, and modeling.” The report also states that,  based on the comments received, “staff did further analyses and also  added sensitivity studies on evacuation timing to assess the risk  significance of relaxed offsite emergency preparedness requirements  during decommissioning.” Given this level of review, we believe it to be  appropriate to report the results of this study.
NRC also took issue with our use of its report, Reexamination of Spent  Fuel Shipment Risk Estimates. NRC explained that the analyses in this  document are similarly overly conservative. This March 2000 study was  conducted by Sandia National Laboratory at the request of NRC to  reexamine the conclusions reached in previous studies regarding the risks  of spent fuel shipments. As with its February 2001 report, this report also  indicated a high level of review prior to publication. Specifically, the  report mentions a number of individuals who provided comments to the  report, including staff at Sandia National Laboratory, Lawrence Livermore  National Laboratory, and “a number of technical experts at the NRC.”
Given the intent of this study and its level of review, we believe it to also  be appropriate to report the results of this study.
section_title: Scope and Methodology
paragraphs: We performed our review at DOE and NRC headquarters in Washington,  D.C., at NRC’s Region III office near Chicago, Illinois, and at DOE’s Yucca  Mountain Project office in Las Vegas, Nevada. We visited several sites  where spent fuel is stored, including operating nuclear power plants, a  decommissioned nuclear power plant, and independent spent fuel  storage sites. We conducted our review from April 2002 to June 2003 in  accordance with generally accepted government auditing standards.
To determine the potential health effects of a terrorist attack or a severe  accident involving commercial spent nuclear fuel, we examined a variety  of federally sponsored studies, primarily conducted or sponsored by DOE  and NRC. We examined critiques of these studies prepared by a variety of  groups and individuals. We also spoke to many of the authors of these  federal studies, authors of critiques of these studies, nuclear energy  representatives, and other individuals representing a variety of  backgrounds, including academia and special interest groups.
To identify options for DOE to enhance the security of spent fuel as it  develops its plans to ship the fuel to Yucca Mountain, we reviewed  documents analyzing DOE’s plans and preferred alternatives, including the  environmental impact statement and many of its supporting documents.  We also interviewed DOE, NRC, and Department of Transportation  officials responsible for developing and coordinating safe shipments of  spent nuclear fuel. We also spoke to state and local government officials in  a number states, including Nevada; nuclear energy representatives; and a  variety of groups and individuals representing a spectrum of viewpoints on  the shipment of spent nuclear fuel.
As agreed with your office, unless you publicly announce the contents  of this report earlier, we plan no further distribution of it until 30 days  from the date of this letter. At that time, we will send copies of this report  to other interested parties and make copies available to others who  request them. In addition, the report will be available at no charge on  GAO’s Web site at http://www.gao.gov/.
If you or your staff have any questions about this report, please call me at  (202) 512-3841. Key contributors to this report are listed in appendix V.
section_title: Appendix I: Nuclear Regulatory Commission Requirements for Safety and Security of Spent Fuel
paragraphs: As the regulating agency responsible for spent fuel, the Nuclear Regulatory  Commission (NRC) must adequately protect the public health and safety  against accidents or acts of sabotage. To provide this assurance, NRC uses  a “defense-in-depth” philosophy. Consistent with this philosophy, NRC  designs its safety and security requirements to ensure that public safety  and health are not wholly dependent on any single element of the design,  construction, maintenance, or operation of a nuclear facility. More  specifically, NRC designs multiple or redundant measures to mitigate  areas of known risk or to increase confidence in areas of uncertainty.  Listed below are some of the primary requirements NRC has recognized as  protecting spent fuel while in transit, in wet storage, and in dry storage.
subsections: section_title: Requirements for Preventing Release of Spent Fuel in Transit
paragraphs: NRC requires that transporters of spent fuel (1) contain the fuel in  NRC-certified shipping containers that must meet stringent durability  performance requirements and (2) comply with requirements designed  to impede an act of sabotage on the fuel.
NRC regulations for spent fuel shipping containers dictate that the  containers prevent releases of significant amounts of radiation under both  normal operating conditions and in hypothetical accident scenarios. The  containers include shielding to ensure that persons near a container are  not exposed to significant amounts of radiation. In addition, the containers  must remain intact after a series of simulated accident conditions,  including    an impact test, in which containers are dropped from 30 feet onto a flat,    a puncture test, in which containers are dropped from 40 inches onto a  6-inch diameter steel bar at least 8 inches long;    a fire test, in which containers are engulfed in a 1,475-degree Fahrenheit  fire for 30 minutes; and    an immersion test in which containers are submerged in 3 feet of water for  8 hours.
The containers must survive each of these tests in succession, without  significant levels of surface radiation or release of spent fuel. Containers  must also be shown to survive water pressure equivalent to immersion  under nearly 670 feet of water for 1 hour.
Because of these requirements and the dimensions of the spent fuel  assemblies they contain, spent fuel shipping containers are massive and  robust. A typical train container is about 25 feet long and 11 feet in  diameter, weighs about 100 tons empty, and about 120 tons fully loaded— thus the container can account for over 80 percent of the total weight of a  shipment. Though truck containers have significantly less capacity than  rail containers, both types have similar basic designs. As figure 2 indicates,  they are generally composed of several layers of shielding material,  totaling about 5 to 15 inches in thickness, including a radiation barrier  consisting of lead or depleted uranium.
When in transit, each end of the container is made of material that is  designed to absorb much of the force of an impact. Figures 3 and 4 show a  spent fuel rail container and a truck container, respectively.
Although the shipping container is the most important component in  preventing release and dispersal of spent fuel in transit, NRC also requires  transporters of the spent fuel to implement measures designed to further  protect spent fuel shipments from sabotage. For example, transporters  of spent fuel must ensure that shipments are under surveillance, that  arrangements have been made with local law enforcement agencies for  their response in the event of an emergency, and that rail and highway  routes have been approved by NRC. NRC had also required that armed  escorts be either aboard the shipping vehicle or in a following vehicle in  areas of high population; NRC has since strengthened the security required  of shipments following the September 11, 2001, terrorist attacks.
subsections: section_title: Requirements for Preventing Release of Spent Fuel in Wet Storage
paragraphs: Spent fuel pool designs must meet specific performance criteria before  NRC can issue a license for construction or operation. The requirements  focus on ensuring that the safety features of the pool survive certain  natural phenomena or accidents to ensure that, among other things, the  pool will retain water and keep the stored fuel sufficiently cool. Spent fuel  in wet storage is also protected by the physical security measures in place  at the storage site.
As part of the licensing process prior to construction and operation,  utilities must submit reports that analyze the likelihood of certain natural  phenomena, such as earthquakes, hurricanes, floods, and tidal waves.  Using probability analyses, historical information, and current information  on seismology, geology, meteorology, and hydrology, the utilities must  determine the risks of certain types of natural phenomena. Then the  utilities must show that the proposed pool designs would survive the most  severe natural phenomena or combinations of less severe phenomena  expected for that particular area. The utilities must also perform the same  exercise for the likelihood and severity of certain accidents, including  airplane crashes. For example, pools constructed near airports may have  to be designed to withstand certain types of accidental airplane crashes.
Consequently, although the specific designs of wet storage pools vary  from site to site, they are massive, robust structures. Pools are typically  30 to 60 feet long, 20 to 40 feet wide, and 40 feet deep. Pools could nearly  hold three semi-truck tractor-trailers parked side-by-side and stacked  three deep. The pool is contained by a structure consisting of a 1/8 inch to  1/4 inch stainless steel liner, and 4- to 6-foot thick walls of steel-reinforced  concrete. Generally, the pools are contained in other buildings. The roofs  of some of these buildings may be made from industrial-type corrugated  steel. The assemblies, stored vertically in racks, must be immersed at least  20 feet below the surface of the water in order to keep the fuel cool and to  provide a sufficient radiation barrier. See figure 5 for a photograph of a  wet storage pool.
Spent fuel pools are also protected by the physical security measures in  place at the facilities where they are located. About 95 percent of the spent  fuel inventory is stored in pools, most of which are located at operating  nuclear reactors. The perimeters of these reactor sites are secured by  fences topped with barbed wire, vehicle barriers, and intrusion detection  systems—including perimeter cameras and motion detection technology— that are monitored 24 hours per day. Access to the building containing the  wet storage pools is impeded by locked steel doors capable of surviving  armed assault and security checkpoints where a person’s identity must be  verified and where security searches take place. Finally, these facilities are  manned by a force of armed guards.
In addition, nuclear power plants are required to coordinate an emergency  response to the site in the event of a terrorist or sabotage event. The  coordination requires contingency plans and joint exercises with local  law enforcement agencies to ensure an adequate and timely response to  an event. Since the terrorist attacks of September 11, 2001, NRC has  added additional requirements, including additional armed guards and  vehicle barriers.
section_title: Requirements for Preventing Release of Spent Fuel in Dry Storage
paragraphs: NRC requires that spent fuel in dry storage be stored in containers that  protect workers and other nearby persons from significant amounts of  radiation, and that can survive operational accidents at the storage site, as  well as extreme meteorological and other natural events. In addition, fuel  in dry storage is protected by physical security measures in place at the  storage site.
Among other things, dry storage containers must be capable of surviving    a drop test, in which containers are tested by a drop from the height to  which it would be lifted to during operations;    a tip-over test, testing containers against seismic, weather, and other  forces or accidents that could knock over 100- to 150-ton containers,    an explosion test, in which containers are tested against nearby explosions  and the resulting pressures created by the blasts;    a tornado and tornado missile test, in which high winds and tornado    a seismic test, in which containers are tested against the seismic motions  that might be expected to occur in its geologic area (certification  requirements may differ from region to region);    a flood test, in which containers are analyzed for floods; and    a fire test, in which containers are engulfed at temperatures up to  1,475 degrees Fahrenheit for 30 minutes.
Manufacturers must provide NRC with information on how well a  container design meets these performance requirements. NRC does not  require physical tests of the containers, but it accepts information derived  from scaled physical tests and computer modeling.
As with shipping containers, to meet these performance requirements,  certified dry storage containers are massive and robust. A typical dry  storage container consists of a 1-inch thick steel container housing the  spent fuel. At some facilities, the containers are placed horizontally in  garage-sized bunkers constructed of concrete. The concrete protects  nearby workers and the public from radiation. At other facilities, the  container is encased in an outer cask. The outer cask typically is  constructed of steel-reinforced concrete, 18 or more inches thick. Like  the concrete bunkers, the outer cask shields workers and the public from  radiation. The free-standing, upright units, stored on concrete pads, can  weigh from 100 to 150 tons each with nearly 90 percent of that consisting  of the container weight. A dry storage container can store between 7 and  68 assemblies, depending on the size of the container. See figure 6 for an  illustration of a dry storage container.
In addition to the physical performance requirements of dry storage  containers, the containers are protected by the physical security measures  in place at the facilities where they are stored. Dry storage containers at  operating nuclear power plants generally benefit from the physical  security measures already in place at the sites. The large majority of spent  fuel in dry storage is located at operating nuclear power plants. For dry  storage containers situated away from a reactor site, NRC requires vehicle  barriers, fences, intrusion detection systems, and guards. The guards are  also able to contact local law enforcement agencies for assistance, if  required. NRC requires that dry storage facilities coordinate response  plans with local law enforcement agencies to ensure assistance can be  readily provided, if needed. In the wake of the September 11, 2001,  terrorist attacks, NRC issued orders to dry storage facility licensees that  required enhanced security measures, including additional protections  against a vehicle bomb threat.
section_title: Appendix II: Additional Information on Studies on the Safety and Security of Spent Fuel in Transit
paragraphs: The human health implications of sabotage events and accidents  involving spent nuclear fuel shipments described in the report are based  on computer-based engineering and other analytic models that rely, in  part, on physical experiments. In addition, these studies are the most  recent in a series of studies that date back to the 1970s. According to NRC  and DOE, better data and improved analytic tools over the years have  significantly enhanced the agencies’ confidence in the results of these  studies. This appendix provides an overview of the methodology of the  most recent studies, as well as the approach and results of previous  studies.
subsections: section_title: Sabotage Studies
paragraphs: Methodology of Most Recent Studies. The 1999 Sandia National  Laboratory study was undertaken at the request of DOE for use in its  preparation of an environmental impact statement for the Yucca Mountain  repository. The study relied on computer models to estimate how the  two selected armor-piercing missiles would damage shipping containers.  Although no physical tests or experiments were conducted in this study,  the study used computer models that were validated using the results of  previous studies that included experimental data.
Two of the most important factors considered in designing the study were  the types of shipping containers and the weapons selected for analysis.  For the shipping containers, the study used truck and rail containers  considered representative of those that would be used to transport the  spent fuel likely to be shipped in the early decades of the 21st Century.  NRC’s performance standard for these containers requires that they  prevent release of significant amounts of radiation under normal  operating conditions and in accident scenarios. For example, radiation  levels at the exterior of the container must remain below specified  minimal levels after a series of tests to simulate accident conditions,  including an impact test, in which the container is dropped from 30 feet  onto a flat, unyielding surface.
In selecting the weapons used in the analysis, the authors researched the  latest information available and chose weapons they believed represented  the two weapons that would penetrate spent fuel shipping containers, and  which could also be available to terrorists.
To ensure that the analysis would represent the upper limit of possible  damage, the authors made conservative assumptions, including the  following:    No security measures were in place, such as armed guards who travel with  spent fuel shipments and who are required to have the capability to  contact local law enforcement personnel in the event of an attack.
The weapons would be employed at a distance from these containers that  would result in maximum damage to the container and that the weapon  would strike the container dead center; if the missile were to strike higher  or lower, it could be deflected by the cylindrical shape of most containers,  and penetration of the container would be lessened or not occur at all.
Previous Studies. The 1999 Sandia study is the most recent in a series of  federally sponsored studies dating back to the 1970s that have examined  the ability of armor-piercing weapons to penetrate spent fuel containers.  A draft version of a Sandia study from 1978, for example, concluded that  a successful sabotage attack on a spent fuel container would not cause  prompt fatalities but could cause several hundred latent cancer fatalities in  a densely populated urban area. The final version of this study reduced  the total latent cancer fatalities to fewer than 100, based on a re-evaluation  of the quantity of radioactive material released. Based largely on the  initial draft of this study, NRC established its regulations for security of  spent fuel in transit. Because this study was based on a conservative set of  analytical assumptions instead of on experimental data, there was a high  degree of uncertainty regarding the quantities of radioactive material  released, and the human health consequences. Consequently, in 1983, DOE  commissioned Sandia National Laboratory to conduct physical tests, in  which armor-penetrating missiles were fired at shipping containers  containing mock spent fuel assemblies. The study found that, under the  worst-case scenario, about 24 ten-thousandths (0.0024) of 1 percent of the  total solid fuel inventory in the container could be released as respirable  particles. To estimate the human health impact, the study included  conservative assumptions, including that the attacks occurred in  Manhattan, in New York City, on a business day, that the fuel had been  removed from the reactor for only 150 days (and thus was comparatively  more radiologically dangerous), and that no evacuation took place to limit  human exposure. Based on these results and assumptions, the study  predicted no early deaths and between two and seven long-term latent  cancer fatalities.
section_title: Accident Studies
paragraphs: Methodology of Most Recent Studies. According to NRC, the 2000  Sandia National Laboratory study was conducted to address three  developments—the likelihood that spent fuel shipments would be  increasing as a result of the progress on the Yucca Mountain repository,  the use of containers and transportation routes that differed from those  considered in previous studies, and the increased effectiveness in risk  assessment and computer modeling of spent fuel containers. The overall  objective of the study was to determine the degree of risk involved in  shipping spent fuel by truck and rail.
The study examined the effects of severe collisions and fires on four  types of shipping containers—a lead-lined steel truck container, a  depleted uranium-lined steel truck container, a lead-lined steel rail  container, and a monolithic steel container. The study relied on computer  analysis to estimate the probability of such events and the quantity of  radioactive material that might be released. The analysis developed  19 representative truck accidents and 21 representative rail accidents.
The study simulated the effect on each of the truck and rail containers  after slamming them into a rigid surface from a variety of angles at 30, 60,  90, and 120 miles per hour. None of the cases modeled showed that the  body of the container would fail. Moreover, the modeling showed that the  seals around the lid at each end of the truck container would not allow a  release at 30, 60, and 90 miles per hour, although they may leak at  120 miles per hour. The results from modeling the two different rail  containers, however, showed that the seals may leak, for some collisions  at a speed of 60 miles per hour, depending on the angle of impact.
DOE’s study that predicted the health effects of these releases used a  computer code. The code calculated the dispersion of radioactive particles  and the resultant dose to the population. To estimate latent cancer deaths,  DOE made a number of key assumptions. DOE’s analysis assumed the  accident occurred in the most populous center of an urban area and that  the population distribution from the accident site in the urban center to  the outer fringes was similar to the average populations—projected to the  year 2035—of the 20 largest U.S. metropolitan areas, plus Las Vegas,  Nevada. Stable weather conditions—with comparatively slow wind  speeds—were assumed to prevail at the time of the accident. Finally, the  population was assumed to be exposed to remnants of the release for 1  year after the accident, with no evacuation or cleanup.
Previous Studies. The 2000 Sandia study reexamined the risks  associated with the transport of spent fuel by truck and rail and compared  the results to two previous studies—one conducted by NRC in 1977 and  one performed by DOE’s Lawrence Livermore National Laboratory in  1987. According to NRC, the 2000 Sandia study extended the methods  used in the 1987 report for container analysis and used improved risk  assessment methods.
The 2000 Sandia study found that previous NRC-commissioned studies  overestimated the risks of human exposure due to transportation  accidents. According to NRC and Sandia officials, they have become more  confident in their results as analytical techniques and data have improved.  In 1977, NRC examined the risks of shipping a variety of radioactive  materials, including spent fuel. At that time, NRC determined that the  risks of accidental releases involved in shipping spent fuel and other  radioactive materials were quite small—specifically, the study estimated  latent cancer deaths to be about 3 in 200 years of shipping spent fuel at  estimated rates for 1985. The study concluded that the existing NRC  requirements were adequate to protect public health. Partly because this  study was based on conservative engineering judgments and did not  include physical tests of shipping containers in severe accidents, NRC  subsequently commissioned a study published in 1987 that found that the  risks of spent fuel releases under transportation accident conditions were  much smaller. Performed by Lawrence Livermore National Laboratory  for NRC, this study included a more sophisticated analysis than the 1977  study, using historical data on past transportation accidents to determine  the likelihood of specific accident scenarios. The study then used a  computer-based analysis of accident scenarios involving collisions and fire  temperatures exceeding NRC standards. The 1987 study found that in  99.4 percent of all rail and truck accidents, the container would experience  no significant damage, and no radioactive material would be released.
section_title: Appendix III: Comments from the Department of Energy
section_title: Appendix IV: Comments from the Nuclear Regulatory Commission
section_title: Appendix V: GAO Contact and Staff Acknowledgments
subsections: section_title: GAO Contact
section_title: Acknowledgments
paragraphs: In addition to the individual named above, Doreen Feldman, Michael  Hartnett, Gary Jones, Cynthia Norris, Robert Sanchez, Amy Stewart,  Barbara Timmerman, and Dwayne Weigel made key contributions to  this report.