Spent nuclear fuel shipping cask

  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.

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United States

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.

Canada

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]

United Kingdom

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.

Baltimore train tunnel fire

On July 18, 2001, a freight train carrying hazardous (non-nuclear) materials derailed and caught fire while passing through the Howard Street railroad tunnel in downtown Baltimore, Maryland, United States.^[1] The fire burned for 3 days, with temperatures as high as 1000°C (1800°F).^[2] Since the casks are designed for a 30-minute fire at 800°C (1475°F), several reports have been made regarding the ability of the casks to survive a similar fire to the Baltimore one.

State of Nevada

The State of Nevada, USA, released a report entitled, "Implications of the Baltimore Rail Tunnel Fire for Full-Scale Testing of Shipping Casks" on February 25, 2003. In the report, they said a hypothetical spent nuclear fuel accident based on the Baltimore fire:^[2]

• "Concluded steel-lead-steel cask would have failed after 6.3 hours; monolithic steel cask would have failed after 11-12.5 hours."
• "Contaminated Area: 32 square miles (82 km²)"
• "Latent cancer fatalities: 4,000-28,000 over 50 years (200-1,400 during first year)"
• "Cleanup cost: $13.7 Billion (2001 Dollars)"

National Academy of Sciences

The National Academy of Sciences, at the request of the State of Nevada, produced a report on July 25, 2003. The report concluded that that the following should be done:^[3]

• "Need to 3-D model (bolts, seals, etc) more than HI-STAR cask for extreme fire environments."
• "For safety and risk analysis, casks should be physically tested to destruction."
• "NRC should release all thermal calculations; Holtec is withholding allegedly proprietary information."

NRC

The U.S. Nuclear Regulatory Commission released a report on November 2006. It concluded:^[1]

The results of this evaluation also strongly indicate that neither spent nuclear fuel (SNF) particles nor fission products would be released from a spent fuel transportation package carrying intact spent fuel involved in a severe tunnel fire such as the Baltimore tunnel fire. None of the three package designs analyzed for the Baltimore tunnel fire scenario (TN-68, HI-STAR 100, and NAC LWT) experienced internal temperatures that would result in rupture of the fuel cladding. Therefore, radioactive material (i.e., SNF particles or fission products) would be retained within the fuel rods.

There would be no release from the HI-STAR 100, because the inner welded canister remains leak tight. While a release is unlikely, the potential releases calculated for the TN-68 rail package and the NAC LWT truck package indicate that any release of CRUD from either package would be very small - less than an A2 quantity.

Rail security

On July 21, 2006, the British newspaper The Daily Mirror reported that one of their reporters was easily able to plant a fake bomb on a train carrying nuclear waste. The reporter, "exploited security lapses to wander up to the unattended wagons at a North West London depot." The newspaper quoted an expert stating that an attack on containers of radioactive waste could kill over 8,000 people and release a poisonous cloud of up to 100 square miles (259.0 km²) across Britain. They also reported that the train could have been hijacked by anyone with a basic knowledge of driving trains.^[4]

The rail company spokeswoman initially claimed that getting close to the nuclear casks was not possible. However, after seeing the Mirror's photographic evidence that they did exactly that, she stated, "The entire journey is protected by very stringent security. However, having seen these pictures we will speak with our security people. A full investigation will be carried out."^[4]

See also

• Dry cask storage
• Spent fuel pool
• Nuclear fuel cycle
• Deep geological repository

References

This article incorporates text from Spent Fuel Transportation Package Response to the Baltimore Tunnel Fire Scenario (NUREG/CR-6886), a public domain work of the United States Government.