Safety of Spent Fuel 

 Transportation
U.S. Nuclear Regulatory Commission

The Agencies: Who Does What?

The U.S. Nuclear Regulatory Commission (NRC) is an 

independent agency created by Congress. Its mission 

is to regulate the nation’s civilian use of radioactive 

materials in a way that protects public health and safety 

and the environment. The NRC regulates commercial 

nuclear power reactors; research, test, and training 

reactors; nuclear fuel cycle facilities; and medical, 

academic, and industrial uses of nuclear materials. The 

NRC also regulates packaging for the transport, storage, 

and disposal of nuclear materials and waste, and 

licenses the export and import of radioactive materials.

The U.S. Department of Transportation (DOT)

coordinates with the NRC to set rules for the packaging 

of nuclear materials. DOT also works with the NRC 

and affected States to regulate their transport. DOT 

regulates carriers, sets standards for routes, and 

is responsible for international agreements on the 

transport of all hazardous materials.

The U.S. Department of Energy (DOE) is responsible 

by law for disposal of spent fuel from the nation’s 

nuclear power reactors. 

The International Atomic Energy Agency (IAEA) is a 

forum for scientific and technical cooperation in the 

nuclear field. Part of the United Nations, the IAEA sets 

global regulations in many areas of the nuclear industry. 

IAEA’s regulations for materials packaging and transport 

serve as a model for the United States and other nations.

IAEA

Cover Photos:

(Left) Transportable spent fuel storage casks sit on a storage pad. (Courtesy: Holtec International)

(Middle) Spent fuel transport cask arrives at Rancho Seco. (Courtesy: Areva)

(Right) Schematic of spent fuel transport cask. (Courtesy: Holtec International)

(Bottom) Spent fuel transport cask arrives on site.

Page 1 Photos:

(Left) Empty transportable spent fuel storage system arrives at Prairie Island. (Courtesy: Areva)

(Right) Transportable spent fuel storage system is readied for storage. (Courtesy: Areva)

(Bottom) Transport package is placed inside conveyance vehicle. (Courtesy: NAC International)
Safety of Spent Fuel Transportation – 1

The Nuclear Regulatory Commission

The NRC regulates the nuclear fuel cycle from beginning to 

end. Starting when the uranium is taken from the ground, 

the NRC oversees its processing and manufacture into 

fuel to be used in reactors. The NRC also plays a role in 

ensuring the safe transportation, storage, and permanent 

geologic disposal of used fuel.

The NRC works to protect public health and safety, the 

environment, and our national security. To keep the public’s 

confidence, the NRC aims to do its work openly and to be 

effective, efficient, and realistic.

Proper handling of nuclear materials helps to protect the 

safety of the public and plant workers. To achieve this aim, 

the NRC works with the DOT and DOE in the United States, 

and with the IAEA internationally. Together, these agencies 

help make sure nuclear materials are packaged and 

transported safely around the world.

This publication explains the NRC’s role in the safe 

packaging and transport of spent nuclear fuel from 

commercial nuclear power plants. The NRC oversees the 

design, manufacture, use, and maintenance of containers 

for these radioactive shipments. However, the NRC does not 

control the timing or destination of spent fuel shipments.

The NRC has three 

main functions:

1. To set standards 

and develop 

regulations

2. To issue licenses 

for nuclear 

facilities and 

nuclear materials 

users

3. To inspect facilities 

to ensure that NRC 

regulations are 

being met
2 – U.S. Nuclear Regulatory Commission

What is Spent Fuel?

Nuclear reactors make electricity and, as a waste product, 

spent fuel. Uranium fuel can power a reactor for a number 

of years until it needs to be replaced. The used fuel is then 

known as spent fuel. It must be stored safely until it can be 

shipped offsite. 

The Nuclear Waste Policy Act sets a policy for safe, 

permanent disposal of spent fuel and other high-level 

radioactive wastes. Congress in 1987 selected Yucca 

Mountain in Nevada as the site to be studied for a repository 

deep underground. DOE applied to the NRC in 2008 for a 

permit to construct the repository there. But DOE withdrew 

its application in 2010. The NRC’s role is to assess whether 

the facility would meet NRC regulatory requirements. Other 

policy considerations are up to DOE and Congress.

All nuclear power reactors move their spent fuel first into 

pools for storage on site. As the amount of spent fuel in 

the pool increases, many reactors are also using dry casks 

for storage. The NRC reviews and approves the designs for 

these systems. 

The NRC would also review any proposal for central interim 

storage of spent fuel. Eventually, spent fuel will need to be 

transported to a central storage or disposal facility from 

sites around the country. These shipments would likely be 

made by rail or on public highways.

Because spent fuel is highly radioactive, people may 

wonder:

• How does the NRC protect the public from radiation 

during transport?

• What is the likelihood one of these shipments will be 

involved in an accident?

• How well can the shipping containers withstand an 

accident and prevent the release of nuclear materials?

The NRC addresses these and other questions as a part 

of its ongoing efforts to ensure safe transport. As new 

technology and real-world information become available, 

the NRC evaluates that information against its regulations. 

It is important to know that spent fuel has been shipped 

safely within the United States and abroad for more than 

40 years. 

Radiation

About half of the 

public’s average 

annual radiation 

exposure comes 

from natural 

sources. These 

sources include 

radon, the human 

body, outer space, 

rocks, and soil. This 

natural radiation is 

called background 

and can vary greatly 

from place to place. 

Nearly all of the 

rest of an average 

person’s exposure 

comes from 

medical sources, 

such as x-rays 

and diagnostic 

tests that are 

used in health 

care. Radiation 

that can be traced 

to radioactive 

materials transport 

makes up a tiny 

fraction of an 

average person’s 

overall exposure. 

Such low levels of 

exposure are very 

unlikely to have any 

biological effect, 

but if they did they 

would be too small 

to be detectable. 

The human 

body responds 

to radiation in 

the same way 

whether it comes 

from natural or 

manmade sources.
Safety of Spent Fuel Transportation – 3

The Key to Ensuring Safety: 

the Spent Fuel Shipping Container

Spent fuel is highly radioactive and must be shielded and 

contained to be transported safely. Safe shipment requires 

a large, robust spent fuel container called a cask.

The NRC regulates the design and construction of these 

casks to ensure the public is protected. Containers used 

to move spent fuel by rail or highway are designed to 

withstand severe accidents. In the U.S. and internationally, 

these designs must pass a series of tests that mimic 

accident forces. The NRC reviews spent fuel containers 

very carefully to ensure they meet the design standards 

and test conditions in the regulations.

These containers must be able to survive four tests 

involving impact, puncture, fire, and submersion in water. 

During and after the tests, the casks must contain the 

nuclear material, limit radiation doses to acceptable levels, 

and prevent a nuclear chain reaction.

To protect workers and the public, a cask has walls of steel 

and shielding materials 5 to 15 inches thick and a massive 

lid. Truck containers weigh about 25 tons when loaded with 

one to two tons of spent fuel. Rail containers can weigh as 

much as 150 tons and can carry up to 20 tons of spent fuel. 

The ends of these transportation containers are encased 

in structures called impact limiters. In an accident, these 

impact limiters would crush and absorb the impact forces, 

protecting the package and its contents.

Spent fuel containers are tightly sealed and provide heavy 

shielding to protect anyone who might be near the cask 

during transport.

The NRC requires 

spent fuel shipping 

casks to survive four 

tests in sequence: 

1. free-drop impact,

2. puncture impact,

3. fire, and 

4. water immersion.

Truck carries NAC 

LWT transport 

package.
4 – U.S. Nuclear Regulatory Commission

Cask designers may use several techniques to demonstrate their 

containers are safe. They can use computer analyses, comparisons with 

other designs, component testing, physical testing of a scale model, or 

a combination of these techniques. Most often, they combine analyses 

and physical testing. They meet with technical review staff from the 

NRC, explain their design, and provide supporting documents in an 

application. The NRC evaluates each design, examines the information in 

depth, and performs its own calculations when needed. NRC reviewers 

are experts in different areas of science and engineering. They include 

structural and materials engineers and safety specialists with advanced 

degrees and many years of experience.

Once the NRC is satisfied that a design meets the requirements, 

it issues a certificate of compliance. This certificate describes the 

approved design (including what materials must be used), the authorized 

contents, and the dimensions of the container. Then the containers 

can be manufactured and used. Manufacturers and shippers have 

programs in place to ensure the containers meet design specifications 

throughout fabrication and transportation. These programs are known 

as quality assurance. To 

ensure the casks meet 

the certificates, NRC 

staff inspects both the 

manufacturer and the 

facilities that will use 

them.

But just having a 

certificate does not mean 

a cask can be used. Both 

NRC and DOT regulations 

also require a number 

of safety determinations 

before each spent fuel 

shipment. These include 

checks for leaks and 

tests to ensure radiation 

levels are within safe 

limits. These actions are 

designed to ensure that 

all aspects of every spent 

fuel shipment meet all 

Storage the safety standards.

Cask

Canister

Bundle of

Spent Fuel

Assemblies
Safety of Spent Fuel Transportation – 5

A Brief History of Spent Fuel Shipments and Studies

More than 1,300 spent fuel shipments have been 

completed safely in the United States over the past 

35 years. Four were involved in accidents, but none 

resulted in a release of radioactive material or a 

fatality due to radiation exposure.

This experience confirms that the safety system 

is sound. But will this hold true when shipments 

increase to move spent fuel to a future repository 

or a storage facility?

The NRC looks at the risks associated with spent 

fuel transport in a methodical and scientific way. 

Several NRC-sponsored studies over the years have 

focused on the risk related to spent fuel transport 

on highways and railroads. The results provide 

additional confidence in the current regulations 

to assure the safety of spent fuel transport.

In a 1977 study1, the NRC found the risk from transporting 

spent fuel to be low. The study gave the NRC confidence that 

existing regulations are adequate to protect the public.

In separate studies in 19872 and 20003, the NRC looked more 

closely at how shipping containers would perform in accidents. 

Each study used more advanced research methods than in the 

earlier studies. Both of these studies found the risk posed by 

spent fuel shipments would be even smaller than estimated in 

1977. That finding holds true even if the number of spent fuel 

shipments were to increase greatly.

The latest risk study, published in January 2014, modeled 

the radiation doses people might receive from spent fuel 

shipments. This study again confirmed that NRC 

regulations for spent fuel transport ensure safety of 

the public and the environment. 

The 2014 study4 looked at how three NRC-certified 

packages would behave during both normal shipments 

and transportation accidents. The study modeled a variety 

of transport routes using population data from the 

U.S. Census Bureau. It used statistics from actual highway 

and rail accidents and state-of-the-art computer models. 

The study considered doses from normal shipments to 

people living along transportation routes. It also looked at 

doses to occupants of vehicles sharing the route, vehicle 

crews and other workers, and anyone present at a stop. 

1. http://pbadupws.nrc.

gov/docs/ML1219/

ML12192A283.pdf

2. http://www.nrc.gov/

reading-rm/doccollections/nuregs/

contract/cr4829/

3. http://pbadupws.nrc.

gov/docs/ML0036/

ML003698324.pdf

4. http://pbadupws.nrc.

gov/docs/ML1403/

ML14031A323.pdf

NAC LWT spent 

fuel transport 

package is moved 

by crane. (Courtesy: 

NAC International)
6 – U.S. Nuclear Regulatory Commission

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.

In addition to these risk studies, the NRC has looked closely at 

real-world transportation accidents involving fires. The NRC did 

a series of case studies on the most severe accidents to see how 

well an NRC-certified spent fuel package would perform. These 

studies show the current regulations protect the public even in 

the most severe fires. The case studies include the Howard Street 

tunnel chemical fire that burned for five days in Baltimore in 2001; 

the 1982 Caldecott tunnel fire and the 2007 MacArthur Maze fire, 

both sparked by gasoline tankers outside Oakland, CA.; and a 2007 

brush fire in the New Hall Pass tunnel outside Los Angeles.

Additional NRC studies 

identified the conditions in an 

accident that could produce a 

fire severe enough to engulf a 

spent fuel transport package.

On the basis of these studies, 

plus operational experience 

and its own reviews, the 

NRC believes spent fuel can 

continue to be shipped safely. 

The evidence shows this will 

be true even if hundreds of 

shipments are made each year. 

The NRC is continuing to track 

spent fuel shipping, including 

more analyses and testing of 

spent fuel casks, to ensure that 

the risks remain low.

TYPICAL SPENT FUEL TRANSPORTATION CASKS 

Generic Truck Cask for Spent Fuel 

Typical Specifications

Gross Weight (including fuel): 50,000 pounds (25 tons) 

Cask Diameter: 4 feet 

Overall Diameter (including Impact Limiters): 6 feet 

Overall Length (including Impact Limiters): 20 feet 

Capacity: Up to 4 PWR or 9 BWR fuel assemblies 

TYPICAL SPENT FUEL TRANSPORTATION CASKS 

Generic Truck Cask for Spent Fuel 

Typical Specifications

Gross Weight (including fuel): 50,000 pounds (25 tons) 

Cask Diameter: 4 feet 

Overall Diameter (including Impact Limiters): 6 feet 

Overall Length (including Impact Limiters): 20 feet 

Capacity: Up to 4 PWR or 9 BWR fuel assemblies 

Generic Rail Cask for Spent Fuel 

Typical Specifications

Gross Weight (including fuel): 250,000 pounds (125 tons) 

Cask Diameter: 8 feet 

Overall Diameter (including Impact Limiters): 11 feet 

Overall Length (including Impact Limiters): 25 feet 

Capacity: Up to 26 PWR or 61 BWR fuel assemblies 

Spent fuel containers are specially designed to protect 

the public by withstanding accident conditions without 

releasing their radioactive contents.

Transportable spent fuel storage cask 

moves to storage pad. 

(Courtesy: Holtec International)

Rail Cask

Truck Cask
Safety of Spent Fuel Transportation – 7

Understanding the Risks

Risk is generally understood to be the chance of 

injury, damage or some kind of loss. The spent 

fuel shipment record in the United States has 

been outstanding to date. Many more shipments 

have been successfully completed internationally 

under the same basic safety standards.

While shipping spent fuel does involve risk, 

NRC studies show this risk is low. As a part of 

its safety effort, the NRC aims to manage the 

hazards to minimize the risk. To evaluate the 

risks, the NRC asks the following three questions 

and then converts the answers into numbers:

• What can go wrong?

• How likely is it to occur?

• If something goes wrong, what are the 

consequences?

The overwhelming majority of spent fuel 

shipments are accident-free. To calculate the 

radiation risks to the public, researchers 

use two scenarios. One involves a trip 

on which an accident occurs; the 

other covers the vast majority 

of journeys that do not 

involve an accident.

Researchers use a fourstep process to study 

actual and potential 

accidents and their effects.

Step 1. Experts determine what 

might happen. 

• They gather historic records.

• They also put together data on 

how many spent fuel shipments 

are likely each year.

• They look at the rate of 

accidents for rail and highway 

shipments.

• They look at a large number of 

accidents that are credible.

• They also look at the effects 

of crash impact forces, fires, 

or punctures on the shipping 

container. They pick forces that 

are more severe than those 

covered by NRC standards.

Shown is a computer simulation of the response of a cask to a severe fire environment. 

Analyses like this and tests are used by NRC to assure safe transportation of spent fuel.
8 – U.S. Nuclear Regulatory Commission

The Accident Scenario

NRC studies show the likelihood of a radioactive 

release is very low. Fewer than 5 in 10,000 

accidents involving a spent fuel container may 

be more severe than the conditions defined 

in the design standards. We would not expect 

a radioactive release in 99.99973% of those 5 

accidents. However, if a very unlikely chain of 

events occurs, an accident might be severe 

enough to cause a release.

To estimate the risk of these severe accidents, 

researchers use a multi-step approach. They use 

data and their experience with past highway and 

rail accidents involving other hazardous materials. 

Part of this step is to determine what kinds of 

accidents could happen and look at what their 

effects might be.

Using this method, the chance that an accident 

would be serious enough to lead to a release is 1 

in 1 billion. If an accident did release radioactive 

material, the dose to the most affected individual 

would not cause immediate harm. 

The Accident-Free Scenario

For most spent fuel shipments, nothing will go 

wrong and no nuclear material will be released. 

For these shipments, experts calculate the total 

radiation dose that all people along the route 

could receive. They use information on routes and 

local populations to determine how many people 

may be affected and the dose they could receive.

The risk to the public from an accident-free 

journey results from the very low levels of 

radiation that may come through the cask walls. 

A person standing along the highway or railroad 

track might receive a brief exposure that is 

well below regulatory limits. Exposure will vary 

depending upon the speed of the vehicle and 

how far away the person is standing. Doses from 

routine transport would be less than 1/1000 

the amount of radiation people receive from 

background sources each year.

Step 2. Engineers use 

complex computer 

programs to estimate 

how the parts of a shipping 

container might be damaged 

by collisions or fires.

• They gather data on how 

much spent fuel each 

container will carry. 

• They analyze how the spent 

fuel might respond in a 

given type of accident.

• They calculate the 

temperature of the 

container and the spent 

fuel itself during a 

long-term fire.

This information allows 

engineers to estimate the 

size of a potential leak and 

how much nuclear material 

might escape.

Step 3. Researchers match 

accident scenarios from 

Step 1 with the analyses 

from Step 2. This tells them 

the likelihood that there 

would be severe damage to 

the container or its contents.

Step 4. A special computer 

program computes a risk 

estimate. The program 

takes accident probability 

estimates, expected 

numbers of shipments, 

route data (like population 

densities), weather data (to 

estimate how any release 

might be spread by wind), 

and radiological dose data to 

produce a risk estimatee.
Safety of Spent Fuel Transportation – 9

The Bottom Line

The NRC believes that shipments of spent fuel in the United States 

are safe. This belief is based on the NRC’s confidence in the 

shipping containers that it certifies and its ongoing research in 

transportation safety.

• The NRC ensures that shipping containers are robust by:

– Defining strict requirements for package design and performance

– Reviewing designs and independently checking a container’s 

ability to meet accident conditions

– Doing inspections to ensure casks are built, maintained and used 

properly

• The NRC also looks at the risks involved in spent fuel shipments. 

The agency:

– Analyzes spent fuel transport records to fully understand potential 

safety issues

– Evaluates new transportation issues, such as projections for the 

number of shipments, changes in population along some routes, 

and other factors

– Keeps up with technology as it evolves to refine estimates of 

current and future risk to the public

There will always be a slight chance that an accident will cause a 

release of nuclear material. But the NRC has found the likelihood 

of such an event and the risk to the public to be extremely low. Even 

so, the NRC will continue to be vigilant about public safety as an 

essential part of its mission.

Spent Fuel Transport Security

The NRC also regulates how spent nuclear fuel is protected in transit 

against sabotage or theft. The agency strengthened these rules after 

Sept. 11, 2001. The current rules for the physical protection of spent 

fuel transport include:

• Coordinating with law enforcement agencies before the shipment

• Requiring advance notice to States, Indian tribes, and the NRC

• Using a communications center and other means to monitor 

shipments while in route

• Using armed escorts, and

• Using devices that allow drivers and escorts to shut the vehicle off
U.S. Nuclear Regulatory Commission

NUREG/BR-0292, Rev. 1

August 2016

For Additional Information Contact:

Office of Public Affairs

U.S. Nuclear Regulatory Commission

Washington, D.C. 20555-0001

Phone: (301) 415-8200

Email: OPA@NRC.GOV

Internet Home Page: http://www.nrc.gov