Spent nuclear fuel shipping cask

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A typical SNF shipping cask mounted on a railroad car.

Spent nuclear fuel shipping casks are used to transport spent nuclear fuel used in nuclear power plants and research reactors to disposal sites such as the to-be-opened one at Yucca Mountain or the Nuclear reprocessing center at COGEMA La Hague site. Each shipping container is designed to maintain its integrity under normal transportation conditions and during hypothetical accident conditions.

In the United States, the acceptability of the design of each cask is judged against Title 10, Part 71, of the Code of Federal Regulations (other nations' shipping casks, possibly excluding Russia's, are designed and tested to similar standards). The designs must demonstrate (possibly by computer modelling) protection against radiological release to the environment under all four of the following hypothetical accident conditions, designed to encompass 99% of all accidents.:

A 9 meter (30-foot) free fall on to an unyielding surface
A puncture test allowing the container to free-fall 1 meter (about 37 inches) onto a steel rod 15 centimeters (about 6 inches) in diameter
A 30-minute, all-engulfing fire at 800 degrees Celsius (1475 degrees Fahrenheit)
An 8-hour immersion under 0.9 meter (3 feet) of water.
Further, an undamaged package must be subjected to a one-hour immersion under 200 meters (655 feet) of water.

In addition, between 1975 and 1977 Sandia National Laboratories conducted full-scale crash tests on spent nuclear fuel shipping casks [1] [2]. Although the casks were damaged, none would have leaked. (See also [3].)

Although the U.S. Department of Transportation (DOT) has the primary responsibility for regulating the safe transport of radioactive materials in the United States, the Nuclear Regulatory Commission (NRC) requires that licensees and carriers involved in spent fuel shipments:

Follow only approved routes;
Provide armed escorts for heavily populated areas;
Use immobilization devices;
Provide monitoring and redundant communications;
Coordinate with law enforcement agencies before shipments; and
Notify in advance the NRC and States through which the shipments will pass.

Since 1965, approximately 3,000 shipments of spent nuclear fuel have been transported safely over the U.S.'s highways, waterways, and railroads.

A typical small SNF shipping cask being mounted on a truck.

By comparison there has been limited spent nuclear fuel transport in Canada. Transportation casks have been designed for truck and rail transport and Canada’s regulatory body granted approval for casks, which may be used for barge shipments as well. Canadian Nuclear Safety Commission regulations prohibit the disclosure of location, routing and timing of shipments of nuclear materials, such as spent fuel. [4]

Over the past 35 years, British Nuclear Fuels plc (BNFL) and its subsidiary PNTL have conducted over 14,000 cask shipments of SNF worldwide, transporting more than 9,000 tonnes of SNF over 16 million miles via road, rail, and sea without a radiological release. BNF designed, licensed, and currently own and operate a fleet of approximately 170 casks of the Excellox design. BNFL has maintained a fleet of transport casks to ship SNF for the United Kingdom, continental Europe, and Japan for reprocessing.

In the UK a series of public demonstrations were conducted in which spent fuel flasks (loaded with steel bars) were subjected to simulated accident conditions. A randomly selected flask (never used for holding used fuel) from the production line was first dropped from a tower. The flask was dropped in such a way that the weakest part of it would hit the ground first. The lid of the flask was slightly damaged but very little material escaped from the flask. A little water escaped from the flask but it was thought that in a real accident that the escape of radioactivity associated with this water would be not a threat to humans or their environment.

For a second test the same flask was fitted with a new lid, filled again with steel bars and water before a train was driven into it at high speed. The flask survived with only cosmetic damage while the train was totally wrecked.