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Nuclear Safeguards Education Portal

Spent Fuel Storage

Spent Fuel Stored in Casks
Spent Fuel Stored in Casks  

There are two acceptable methods for short-term storage of spent nuclear fuel:

  • Spent fuel pools Photo available on Mouseover. This involves storing spent fuel rods under at least 20 feet of water. The water provides adequate shielding from the radiation for anyone near the pool. It also provides cooling for the fuel. The decay of fission products produces heat in the fuel (called decay heat) even after the reactor has ceased operation. This heat necessitates the storage of spent fuel in a pool to allow for heat removal by water. The rods are moved into the water pools from the reactor along the bottom of water canals, so that the spent fuel is always shielded to protect workers. The quantity of fuel that can be stored is constrained by the size of the pool.

  • Dry cask storage. This method involves spent fuel that has already been cooled in the spent fuel pool for at least one year. At this point, the heat production from fission product decay has decreased enough that storage in water is no longer necessary. The fuel is surrounded by an inert gas inside a container called a cask Photo available on Mouseover. The casks are typically steel cylinders that are either welded or bolted closed. The cylinder provides a leak-tight containment for 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. Each canister is designed to hold approximately 2-6 dozen spent fuel assemblies.

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