Dry cask storage

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A typical dry cask storage system with vertical cylinders

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. The fuel is surrounded by inert gas inside a large container. These casks are typically steel cylinders that are either welded or bolted closed. 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 [1]. 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.

[edit] History

In the late 1970s and early 1980s, the need for alternative storage 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 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 was licensed by the Nuclear Regulatory Commission in 1986 at the Surry Nuclear Power Plant in Virginia. 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 Engineering and Environmental Laboratory near Idaho Falls, Idaho. It is estimated that by 2014, all of the nuclear power plants in the United States will be out of room in their spent fuel pools, most likely requiring the use of temporary storage of some kind. Yucca Mountain is expected to open in 2010 at the earliest.

In Canada, Ontario Power Generation is in the process of constructing a Dry Storage Cask storage facility on its Darlington site. Construction work is taking place within their nuclear facilities to facilitate cask loading and transportation.