Frequently Asked Questions and Answers: Spent Nuclear Fuel Transportation
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Public Health and Safety during Transportation of Spent Nuclear Fuel
What is a typical spent fuel transportation package design?
Spent fuel packages have walls made of steel and shielding materials that are 5 to 15 inches thick. They are also sealed with a massive lid. These design features are put into service to protect workers and the public from radiation. Truck packages weigh about 25 tons when loaded with 1 to 2 tons of spent fuel. Rail packages can weigh as much as 180 tons, and can carry up to 25 tons of spent fuel.
The ends of both truck and rail transport packages are encased in structures called impact limiters to protect the package. In the unlikely event of an accident, the impact limiters crush, absorbing the force of the impact and protecting the package and its cargo.
Spent fuel packages are tightly sealed and provide shielding for spent fuel contents. However, it is not possible to block all radiation with shielding. Packages provide enough shielding to reduce external radiation to low levels that protect the public and workers. These levels meet U.S. Department of Transportation (DOT) and NRC regulatory limits for the allowable dose to individuals who might be near the package during transport.
What is the technical basis for NRC's conclusion that transportation containers for spent fuel are safe?
The NRC requires that packages be designed to survive a sequence of accidents – a drop onto a hard surface, a puncture impact, fire and immersion in water – to demonstrate the package is safe. Packages are designed to be robust and resistant to degradation to ensure continuing safety during transportation of the spent fuel. For a package design to be used it must first be approved by going through normal and hypothetical accident conditions.
Normal conditions of transport are conditions that a package may experience during a routine shipment. This includes exposure to rainfall, potholes, and other common conditions. A package is analyzed using advanced computer models at temperatures from -40º C (-40º F) to 38º C (100º F) to demonstrate its tolerance of different ambient conditions. It is also dropped up to four feet onto an essentially unyielding surface to simulate it falling while being loaded onto a transport vehicle. An essentially unyielding surface is a surface that is designed to be as firm as possible. Because it deforms so little, almost all of the energy from an impact is reflected back by the surface to the impacting object. This means that an impacting object will be subjected to much more energy in a collision than if it were dropped onto a "normal" surface, such as a concrete roadway. Water is sprayed on a package for an hour to simulate rain as well. These tests, and others, cover most routine transport conditions, and are used when determining if a package is safe for normal conditions of transport. For more information about the transportation of spent nuclear fuel, see NUREG/BR-0292.
Tests for hypothetical accident conditions include a 30-foot drop onto an essentially unyielding surface and a 4-foot drop onto a 6 inch pin to test for impact on a sharp object. These tests are similar to the tests for normal conditions of transport, but are more severe. An additional test involves immersion in a fully engulfing fire to test the package's response should an accident cause a fire. Finally, a package is immersed in water to ensure it is watertight up to 50 feet if it ends up submerged.. A package is required to meet NRC standards for protection against leakage, radiation dose rates, and criticality after all tests are performed in sequence. Such testing encompasses all but the most extraordinary accidents, and ensures that packages certified by the NRC are safe for spent fuel transportation.
How are workers and members of the public protected from potential radiation exposure from a transportation accident involving spent nuclear fuel?
The risks associated with the transportation of spent nuclear fuel come from the radiation that the fuel emits. This risk is reduced, but not eliminated, by the transportation package's shielding. The possibility of release of radioactive material during a severe accident is low, and the amount of material the package can release in such an occurrence is limited. The radiation emitted from the packages is a small fraction of naturally occurring background radiation, and the risk from an accidental release of radioactive material is several orders of magnitude less. The NRC has evaluated radioactive material transportation risks in NUREG-0170 and a risk assessment of spent fuel transportation in NUREG-2125.
How does the NRC protect the public when spent nuclear fuel is being transported?
NRC regulations establish safety standards for the design and construction of shipping packages as the primary way to protect the public during transportation of spent nuclear fuel. Packages used to move spent fuel by rail or highway are designed to be robust and withstand accidents. U.S. and international regulations require that these packages be evaluated for a series of tests that simulate accident conditions. Packages must meet safety criteria for containment, radiation shielding and criticality safety after the tests are performed in sequence. NRC staff conduct rigorous independent reviews to certify that spent fuel packages meet the design standards and test conditions in the regulations. Before any transportation of spent fuel occurs, NRC staff must review and approve a route plan provided by the carrier. The plan includes pre-arranged safe havens located every 50 miles, as well as arrangements with local law enforcement along the route.
How does the NRC estimate the risk of exposure of transporting spent fuel?
To estimate the likelihood and consequences of severe accidents, the NRC uses a multi-step approach to calculate risk. This approach uses accident data and experience with past shipping accidents involving other hazardous materials. This also involves determining the types, frequencies, and potential consequences of accidents that could impact the shipment of spent fuel. This is done to better understand safety issues and evaluate new transportation issues such as an increased number of shipments, and increases in population density along certain routes. In January of 2014, NRC published NUREG-2125, "Spent Fuel Transportation Risk Assessment". The study was the fourth major study involving the transportation of spent nuclear fuel. The improved analysis tools and techniques, improved data availability, and a reduction in uncertainty estimated the risk of accidental release of radioactive material in this study to be approximately several order of magnitude less than what was originally estimated in NUREG-0170. The results demonstrate that NRC regulations continue to provide adequate protection of public health and safety during the transportation of spent nuclear fuel.
Is there a risk to the public from the transportation of spent fuel?
The risk to the public from the routine shipment of spent fuel is very low. There is a low-level radiation field that surrounds the spent fuel package, but it must meet the regulatory limits of the NRC and the Department of Transportation. The regulatory limit for radiation exposure at a set distance near a transportation package is 10 millirem per hour (0.1 sievert/hr), but packages frequently measure far less than this limit. The limit is only slightly more than a typical chest x-ray and is not considered harmful. Exposure will vary depending on the time spent next to the package, but in normal transport conditions it is unlikely that an individual will be that close to a package for much longer than a few seconds at a time. Such exposure is significantly less than the dose received from background radiation annually and is not a safety concern.
Could a transportation accident cause release of spent fuel?
It is highly unlikely that a transportation accident would cause a release of spent fuel. Packages are designed to withstand severe accidents that are unlikely to occur in routine transportation. In the rare event that an accident were to occur, the robust design of the package would make it highly improbable that any spent fuel would be released. NUREG-2125 examined the risk associated with the transportation of spent nuclear fuel using three NRC-certified packages during routine transportation and in transportation accidents. If there were an accident during a spent fuel shipment, there is only about a one-in-a-billion chance that the accident would result in a release of radioactive material.
NRC's Safety Program (Package Standards, Design Reviews, Testing, Risk Studies, Quality Assurance & Inspections)
Will the NRC allow the transportation of a canister with a crack?
The NRC would allow the transport of a canister with a defect as long as the canister meets the criteria of an NRC-approved transport certificate of compliance. The canister would have to be evaluated against the requirements in 10 CFR 71 to ensure public safety if transported. The regulatory requirements of 10 CFR 71.87 require that before each shipment of licensed material, the licensee shall ensure that the package with its contents satisfies the applicable requirements of the license. A package would not be approved for transportation if a defect had fully penetrated the containment boundary. If a defect only partially penetrates the containment boundary, it would need to be evaluated further. If the defect presented a structural risk to the package, or impaired the casks ability to properly contain the spent nuclear fuel, it would not be approved for shipment. In cases where a defect in a package is present, repairs are also considered as a way to restore and/or ensure the package is acceptable for use.
How will aging and degradation such as chloride induced stress corrosion cracking (CISCC) affect the retrievability and transportability of dry storage canisters?
Analysis of existing canister designs and confirmatory testing of residual stresses in welded stainless steel canisters have shown that there are only limited parts of a canister where through-wall stress corrosion cracking may occur, primarily near welds performed during construction of the canister. The extent of cracking will be small and would not affect the structural integrity of the canister, or impair retrievability of the canister from any of the currently NRC certified systems. An assessment of flaw size for normal and accident conditions is included in the Flaw Growth and Flaw Tolerance Assessment for Dry Cask Storage Canisters (EPRI, Palo Alto, CA: 2014).
Prior to transportation, a licensee must evaluate a canister and its contents to verify they meet the description in the transportation certificate of compliance and the regulatory requirements. Spent fuel storage canisters may be inspected by the NRC prior to transportation. Verification of inspection system performance will follow practices that have been used for many years in the nuclear industry and must meet the requirements in 10 CFR 71.119.
For more information see the following: EPRI
What is the NRC doing to ensure that these shipments are transported safely and securely?
Activities conducted by the NRC staff fall into four broad areas that ensure that radioactive materials are transported safely. The NRC staff review and certify transport package designs for large quantities of fissile and radioactive material contents to ensure that the material will be transported in a safe container. The NRC staff inspect manufacturers of packages to provide additional assurance that packages conform to NRC approved designs, and have been manufactured in accordance with NRC required and approved quality assurance programs. The NRC staff also conduct a shipment inspection program to confirm that licensees are preparing shipments in conformance with the NRC Certificate of Compliance and applicable regulations. The NRC has developed security requirements for spent fuel shipments, including components such as immobilization devices on cargo vehicles, NRC pre-approval of routes, driver and escort training, arrangements with law enforcement officials along the route, notification of tribal officials, notification of governors, communications, and armed escorts through high-density population areas combine to enhance the protection of public health and safety.
At each location where nuclear material is accepted for transportation or placed in a train, the carrier must inspect each rail car containing the material at ground level for required markings, labels, placards, securement of closures, and leakage. Each rail car is also inspected for signs of tampering. This includes closures and seals, suspicious items, items that do not belong, or other signs that the security of the rail car may have been compromised. A rail car may not be moved or transported until any issues found during the inspection are corrected.
Working with our Department of Transportation (DOT) partners, the NRC understands and supports the Commercial Vehicle Safety Alliance (CVSA) Level VI inspections requirements for the material condition of the truck and tractor trailer upon which the spent nuclear fuel is placed for transport. A CVSA Level VI inspection is a stricter inspection standard than the Standard Level I inspection procedure for trucks and tractor trailers. It is adopted and intended for use only on select shipments of radioactive material, including spent nuclear fuel. Additionally, drivers of this material must have a current commercial driver's license, with a hazardous material endorsement. This means the drivers undergo extra training on safety and security procedures, as well as an FBI background check and drug testing.
Have there been any major accidents the NRC has evaluated for transportation of spent nuclear fuel?
While none of the following accidents involved the transportation of spent nuclear fuel, they were chosen due to their extreme circumstances. The MacArthur Maze accident, which occurred near Oakland, California on April 29, 2007, involved a gasoline truck overturning and catching fire under an elevated highway. This accident was selected by the NRC as the third study (NUREG/CR-7206 2016) in a series of evaluations of real-world accidents because of the extreme conditions that it caused. The severity of the fire caused the overhead roadway segments to collapse onto the lower roadway, where the accident occurred, while the fire was burning, leading to both structural and thermal concerns. Two previous studies of transportation accidents, one resulting in a fire in a railroad tunnel in Baltimore, Maryland (NUREG/CR-6886 2009) and one in a highway tunnel in Caldecott, California (NUREG/CR-6894 2007) were undertaken to study the hypothetical involvement of three different spent nuclear fuel package designs and their responses to these accidents. The truck and rail transportation accidents involving fire have been compiled in NUREG/CR-7209.
Based on the evaluation of conservative fire scenarios constructed from these real-world fire accidents, these studies demonstrated that NRC-Certified transportation package designs for spent nuclear fuel are sufficiently robust and capable of enduring even beyond-design-basis conditions, without adverse consequences to public safety. The packages in question were evaluated with state-of-the-art analysis techniques, which included the development of full-scale analysis models that captured the relevant physics and fire behavior to accurately portray the thermal and structural response of these package designs. In each case evaluated, the modeling results showed that the various spent fuel packages would be expected to maintain required shielding for ionizing radiation and maintain their structural integrity, limiting any potential release of radioactive material to within regulatory limits for accident conditions.
For more information see the following:
NRC's Security Program (Physical Protection Regulations, Shipment Plan Reviews, Sabotage Studies)
Are there procedures in place to ensure nuclear material is not damaged and/or hijacked by anyone during transit?
After the terrorist attacks of September 11, 2001, the NRC reviewed spent nuclear fuel transportation requirements and developed new requirements for several areas, including route selection and approval (including safe havens), vehicle immobilization devices, armed escorts, and other procedures. The regulatory bases for spent fuel shipment security are found in 10 CFR Part 73.
The NRC reviews and approves transportation routes to ensure requirements for advance arrangements with law enforcement officials along the entire route are complete and accurate. This ensures that local law enforcement authorities can provide swift and coordinated response to events and calls for assistance. A route plan must include pre-arranged safe havens, located every 50 miles, to provide temporary refuge or emergency assistance. Examples of possible safe havens include truck stops, rest areas, military installations, highway patrol barracks, and weigh stations.
The NRC approves immobilization devices on vehicles to prevent theft of the vehicle. A vehicle driver may immobilize the vehicle in the event of a security risk. The NRC requires a movement control center staffed and equipped 24/7 to monitor and control shipments. The control center is also required to communicate with local law enforcement authorities and respond to normal conditions and security contingencies. The NRC also requires armed escorts for the material at all times during all modes of transport.
Finally, security is enhanced by the robust components of the shipping casks. Packages are analyzed to ensure that they are resilient against sabotage. The outside of all packages must incorporate a feature, such as a seal, that is not readily breakable. While intact, this seal would provide evidence that the package had not been opened by unauthorized persons.
How are tribal, local and state governments along each route notified of spent fuel shipments?
The NRC requires licensees to notify the governor or the governor's designee prior to the transport of spent fuel within or through a state. Subsequent notification within the state is conducted at the direction and discretion of the governor and state government. This may include discussion of a possible law enforcement escort, or identification of safe havens. NRC licensees must also make notifications to participating Tribes for shipments going through or near tribal lands.
What are the primary organizations that develop regulations governing the transport of radioactive materials?
The primary U.S. organizations are the U.S. Department of Transportation and the U.S. Nuclear Regulatory Commission. The International Atomic Energy Agency publishes standards that inform the way the NRC licenses its safety and security regulations to ensure a consistent international standard of excellence is maintained during the movement of spent fuel.
Shipment Operations (Shipment Experience, Logistics, Emergency Response)
Can existing storage canisters be transported and then used again for storage?
Some canisters may be transported and used again for storage. This is dependent on the canister design and Certificate of Compliance (CoC). Certain canisters are designed so they can be removed from a storage system and transferred into a transportation package for shipment. These canisters can be placed back into storage at a new location, provided the licensee meets the regulatory requirements already established by the NRC. In other words, the licensee must ensure the storage canister will continue to meet the conditions set forth in the CoC any time it is to be relocated. The NRC has the regulatory framework and oversight in place to ensure public health and safety during both storage and transportation operations.
If a transportation accident involving spent nuclear fuel occurs, who is responsible to respond and what is NRC's role?
If an accident occurs, state and local governments have the primary responsibility for responding. State and local governments are also responsible for taking any actions deemed necessary to protect the public health and safety. The NRC and other federal agencies can assist upon request.
The NRC will activate its incident response program at the Headquarters Operations Center and one of the four Regional Incident Response Centers in response to any event involving NRC-licensed material that could threaten public health and safety or the environment. The NRC's highest priority is to provide expert consultation, support, and assistance to state and local public safety officials responding to the event. Once the NRC incident response program is activated, teams of specialists are assembled at the Headquarters Operations Center and Regional Incident Response Center to obtain and evaluate event information, and to assess the potential impact of the event on public health and safety and the environment.
How high a priority is population density when considering routes for transportation of spent nuclear fuel? If density is not a high priority, why not?
Routes for transportation of spent nuclear fuel are selected by the carrier (the entity transporting) in consultation with the shipper (the owner of the material), consistent with the U.S. Department of Transportation and carrier-specific requirements. A carrier is not required to consider population density along routes. Once selected by a carrier, each route is submitted to the NRC for evaluation. The NRC's physical protection and security regulations specify that shipments of spent nuclear fuel will be accompanied by an armed escort with constant communications capability. Additionally, efforts are made to transport packages during periods of low traffic. This is done in close coordination with state and local law enforcement. In rail shipments of spent nuclear fuel the NRC specifies that it be accompanied by two armed escorts with constant communications capability.
For more information on transportation, see the following:
Page Last Reviewed/Updated Monday, June 08, 2020