Transporting Spent Nuclear Fuel: How Do We Know It’s Safe?

John Cook
Senior Transportation Safety Scientist
Division of Spent Fuel Storage and Transportation
 

In May, we talked about changes to NRC regulations regarding shipments of nuclear materials – including spent fuel. This month, we wanted to share the results of a periodic evaluation of the risk posed by spent fuel shipments. The NRC expects to publish the final study later this year. A draft was published in 2012.

Microsoft Word - diagram-typical-trans-cask-system-2.docSpent fuel shipments are strictly regulated and have not released any radioactive materials since they began more than 30 years ago. But the NRC still periodically evaluates the risks. As more data become available and computer modeling improves, these studies allow us to refine our understanding of these risks.

The latest study, Spent Fuel Transportation Risk Assessment, modeled the radiation doses people might receive if spent fuel is shipped between various sites. The study confirmed that NRC regulations for spent fuel transport are adequate to ensure safety of the public and the environment.

Both the NRC and the U.S. Department of Transportation oversee radioactive material transport. DOT regulates shippers, vehicle safety, routing, and emergency response. The NRC certifies shipping packages for the more hazardous radioactive materials, including spent fuel.

To be NRC-certified, a package must provide shielding, dissipate heat, and prevent a nuclear chain reaction. It must also prevent the loss of radioactive contents under both normal and accident conditions. The package must be able to survive a sequence of tests meant to envelope the forces in a severe accident. These tests include a 30-foot drop onto an “unyielding” surface (one that does not give, so the package absorbs all the force), a puncture test drop onto a steel peg, and then a 1475-degree Fahrenheit fire that engulfs the package for 30 minutes.

The 2013 risk assessment examined how three NRC-certified packages would behave during both normal shipments and accidents. It modeled a variety of transport routes using population data from the 2000 census, as updated in 2008. It used actual highway and rail accident statistics. It considered doses from normal shipments to people living along transportation routes, occupants of vehicles sharing the route, vehicle crew and other workers, and anyone present at a stop. And it used state-of-the-art computer models. The risk assessment found:

 Doses from routine transport would be less than 1/1000 the amount of radiation people receive from background sources each year

 There is less than a 1 in 1 billion chance that radioactive material would be released in an accident

 If an accident did release radioactive material, the dose to the most affected individual would not cause immediate harm

The 2013 risk assessment builds on earlier studies of transportation risks. It uses real-world data and equipment in place of generic designs and conservative assumptions. The first study, done in 1977, allowed the NRC to say that its transport regulations adequately protect public health and safety. Other studies done in in 1987 and 2000 found the risks were even smaller than the 1977 study predicted. These studies, together with analyses we perform on major transportation accidents, previous physical testing of package performance, and the global experience with thousands of completed spent fuel shipments, give the NRC confidence in the safety of spent fuel shipments.

For more information on how the NRC regulates spent fuel transportation, click here. To read our updated backgrounder on the subject, click here.

Updating Nuclear Materials Transportation Regulations

Jessica Umaña
Project Manager, Division of Spent Fuel Storage and Transportation
 

The idea of transporting nuclear materials can make people nervous. It’s easy to imagine worst-case accidents on the highway or involving a train. But stringent safety requirements, as well as coordination among federal agencies, international regulators, and state and local officials, help to ensure these shipments are made safely. This structure provides many layers of safety.

From time to time, the requirements are updated to address new information. The International Atomic Energy Agency (IAEA) and U.S. Department of Transportation recently updated their requirements. The NRC is now amending ours to reflect those updates, as well as to make some changes we feel are needed based on recent experience. You can read the Federal Register notice on the proposed rule.

mapWhile the rules are being updated, the fact remains that nuclear materials are transported safely all the time. By far the majority of shipments involve small quantities of nuclear materials. Millions of these shipments are made each year and arrive at their destination without incident. Occasionally, the carrier might be involved in a traffic accident. But in decades of transporting nuclear materials, there has never been an accident that resulted in a radioactive release.

Smaller shipments must be made in compliance with DOT regulations for shipping hazardous materials. The greater the potential risk of the contents, the more stringent DOT’s packaging requirements are. The DOT regulations limit how much radioactivity can be transported in each package. That way, no transport accident involving these small shipments would pose a serious health threat.

But what about larger amounts of radioactive materials? What about spent nuclear fuel?

In addition to having to meet DOT requirements, more radioactive cargo such as spent fuel must meet NRC regulations for nuclear materials packaging and transport in 10 CFR Part 71. These regulations include very detailed requirements for shipping under normal conditions, as well as stringent tests to show the packages can withstand severe accidents. These are the regulations we are updating now.

If you would like to learn more about the transportation of spent fuel and radioactive materials, see our newly updated backgrounder.