Dry cask storage
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 and often as much as ten years.Casks are typically steel cylinders that are either welded or bolted closed. The fuel rods inside 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.
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. 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 fuel pool storage.
Some of the cask designs can be used for both storage and transportation. Three companies – Holtec International, NAC International and Areva-Transnuclear NUHOMS – are marketing Independent Spent Fuel Storage Installations (ISFSI's) based upon an unshielded multi-purpose canister which is transported and stored in on-site vertical or horizontal shielded storage modules constructed of steel and concrete.
During the 2000s, dry cask storage was used in the United States, Canada, Germany, Switzerland, Spain, Belgium, Sweden, the United Kingdom, Japan, Armenia, Argentina, Bulgaria, Czech Republic, Hungary, South Korea, Romania, Slovakia, Ukraine and Lithuania.
A similar system is also being implemented in Russia. However, it is based on 'storage compartments' in a single structure, rather than individual casks.
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 nuclear storage facility in operation at the time, utilities began looking at options for storing spent fuel. Dry cask storage was determined to be a practical option for storage of spent fuel and preferable to leaving large concentrations of spent fuel in cooling tanks. 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. 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. 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.
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