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Dry cask storage is a way to safely contain spent nuclear fuel and other radioactive waste. The spent rods are surrounded by inert gas in containers made of a heavy-duty material such as lead, steel-enforced concrete, and steel. These vessels are typically bolted or sealed shut via welding. They are then surrounded by further means of protection such as cement or more steel. The goal is to avoid leakage of hazardous, high-level waste and shield the environment from radiation. It is meant to be a temporary containment for the rods until more secure storage is found.
When it is first produced, radioactive waste is cooled in an area called the spent fuel pool. Once at least a year — and typically several — have passed, it is put into dry cask storage. Radioactive waste that is stored via this method is typically safe for both transport and storage, though the amount of movement it can handle depends on how the cask is designed.
There are several different ways dry cask storage can be oriented. It may be placed inside a vault or on a cement pad. The canisters can be store vertically or horizontally and are typically in the shape of a cylinder. How the storage is arranged depends upon the location and resources of a particular facility, though it is often placed in two rows of canisters.
Dry cask storage was created in order to deal with an excess of spent fuel pools. In the late 1970s and early 1980s it was determined that these pools would pose an environmental hazard if an alternative method of containment was not found. Now there are several facilities, known as dry storage installations, which house the casks. Storage vessels can number in the hundreds in these locations.
Ensuring the security of the vessels used for dry cask storage is an ongoing process. There have been cases where casks have cracked or eroded, allowing other gases into the vessel. These incidents are typically the result of poor construction as the waste itself does not typically lead to degeneration of the containers.
Government agencies such as the Nuclear Regulatory Commission (NRC) in the United States of America provide regulations, oversight, and other aid to power plants. This includes ensuring the proper storage of waste, such as with the dry cask method. These organizations serve as an advocate for citizens and ensure that they have a safe environment where waste is concerned.
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