Dry cask storage


Dry cask storage
Example of a dry cask storage area.

Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel that has already been cooled in the spent fuel pool for at least one year.[1]. These casks are typically steel cylinders that are either welded or bolted closed. When inside, the fuel rods are surrounded by inert gas. Ideally, the steel cylinder provides leak-tight containment of the spent fuel. Each cylinder is surrounded by additional steel, concrete, or other material to provide radiation shielding to workers and members of the public. Some of the cask designs can be used for both storage and transportation.

There are various dry storage cask system designs. With some designs, the steel cylinders containing the fuel are placed vertically in a concrete vault; other designs orient the cylinders horizontally.[2] The concrete vaults provide the radiation shielding. Other cask designs orient the steel cylinder vertically on a concrete pad at a dry cask storage site and use both metal and concrete outer cylinders for radiation shielding. Currently there is no long term permanent storage facility, dry cask storage is designed as an interim safer solution than spent pool storage.

The containers are also known as castor containers, which is an acronym for "cask for storage and transport of radioactive material". CASTOR is a tradename of the Gesellschaft für Nuklear-Service, a company for nuclear services.

Contents

Usage

During the 2000s, dry cask storage was used in the United States, Canada, Germany, Switzerland, Belgium, Sweden, the United Kingdom, Japan, and Lithuania.[3][4]

United States

In the late 1970s and early 1980s, the need for alternative storage in the United States began to grow when pools at many nuclear reactors began to fill up with stored spent fuel. As there was not a national storage facility in operation (Yucca Mountain nuclear waste repository was, and remains, embroiled in controversy), utilities began looking at options for storing spent fuel. Dry cask storage was one of the most practical options for temporary storage.

The first dry storage installation in the US was licensed by the Nuclear Regulatory Commission (NRC) in 1986 at the Surry Nuclear Power Plant in Virginia, at 37°09′47″N 76°41′10″W / 37.1630°N 76.6861°W / 37.1630; -76.6861 (Surry Power Station spent fuel storage). Spent fuel is currently stored in dry cask systems at a growing number of power plant sites, and at an interim facility located at the Idaho National Laboratory near Idaho Falls, Idaho. The Nuclear Regulatory Commission estimates that many of the nuclear power plants in the United States will be out of room in their spent fuel pools by 2015, most likely requiring the use of temporary storage of some kind.[5] Yucca Mountain was expected to open in 2017. However on March 5, 2009, Energy Secretary Steven Chu reiterated in a Senate hearing that the Yucca Mountain site was no longer considered an option for storing reactor waste.[6]

In the 1990s, the NRC had to “take repeated actions to address defective welds on dry casks that led to cracks and quality assurance problems; helium had leaked into some casks, increasing temperatures and causing accelerated fuel corrosion”.[7]

The 2008 NRC guideline calls for fuels to have spent at least five years in a storage pool before being moved to dry casks.[8] It describes the dry casks used in the US as "designed to resist floods, tornadoes, projectiles, temperature extremes, and other unusual scenarios."[8]

With the zeroing of the budget for Yucca Mountain nuclear waste repository in Nevada, more nuclear waste is being loaded into sealed metal casks filled with inert gas. Many of these casks will be stored in coastal or lakeside regions where a salt air environment exists, and the Massachusetts Institute of Technology is studying how such dry casks perform in salt environments. Some hope that the casks can be used for 100 years but cracking related to corrosion could occur in 30 years or less.[9]

Canada

In Canada, above-ground dry storage has been used for a number of years. Ontario Power Generation is in the process of constructing a Dry Storage Cask storage facility[10] on its Darlington site, which will be similar in many respects to existing facilities at Pickering Nuclear Generating Station and Bruce Nuclear Generating Station. NB Power's Point Lepreau Nuclear Generating Station and Hydro-Québec's Gentilly Nuclear Generating Station also both operate dry storage facilities.

Germany

A centralized storage facility using dry casks is located at Ahaus.[11] As of 2011, it housed 311 casks; 305 from the Thorium High Temperature Reactor, 3 from the Neckarwestheim Nuclear Power Plant, and 3 from the Gundremmingen Nuclear Power Plant.[11] The transport from Gundremmingen to the Ahaus site met with considerable public protest and the power plant operators and the government later agreed to locate such casks at the powerplants.[11]

Lithuania

Spent fuel from the now-closed Ignalina Nuclear Power Plant was placed in CASTOR and CONSTOR storage casks during the 2000s.[4]

See also

References

  1. ^ "Dry Cask Storage". Nuclear Regulatory Commission. http://www.nrc.gov/waste/spent-fuel-storage/dry-cask-storage.html. Retrieved 2011-03-17. "Dry cask storage allows spent fuel that has already been cooled in the spent fuel pool for at least one year to be surrounded by inert gas inside a container called a cask," 
  2. ^ [1] NRC; Dry Cask Storage Figure 43
  3. ^ OECD Nuclear Energy Agency (May 2007). Management of recyclable fissile and fertile materials. OECD Publishing. p. 34. ISBN 9789264032552. http://books.google.com/books?id=E1UuVHi7CDAC&pg=PA34. Retrieved 22 March 2011. 
  4. ^ a b "Radiological and thermal characteristics of CASTOR RBMK-1500 and CONSTOR RBMK-1500 casks for spent nuclear fuel storage at ignalina Nuclear Power Plant". Hanser, cited through CAT.INIST. 2006. http://cat.inist.fr/?aModele=afficheN&cpsidt=18041752. Retrieved 2010-01-01. 
  5. ^ NRC Graph of Spent Fuel Capacity
  6. ^ Hebert, H. Josef. 2009. “Nuclear waste won't be going to Nevada's Yucca Mountain, Obama official says.” Chicago Tribune. March 6, 2009, 4. Accessed 2009-03-06.
  7. ^ Benjamin K. Sovacool (2011). Contesting the Future of Nuclear Power: A Critical Global Assessment of Atomic Energy, World Scientific, p. 144.
  8. ^ a b "Fact Sheet on Dry Cask Storage of Spent Nuclear Fuel". NRC. May 07, 2009. http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/dry-cask-storage.html. Retrieved 2011-03-21. 
  9. ^ Matthew Wald (August 9, 2011). "Researching Safer Nuclear Energy". New York Times. http://green.blogs.nytimes.com/2011/08/09/researching-safer-nuclear-energy/. 
  10. ^ [2] Ontario Power Generation ; Darlington Waste Management Facility
  11. ^ a b c "Safety and Security of Commercial Spent Nuclear Fuel Storage: Public Report (2006) Board on Radioactive Waste Management (BRWM)". National Academies Press. http://www.nap.edu/openbook.php?record_id=11263&page=94. Retrieved 2011-03-21. 

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