Dry Cask Storage

Nuclear power plants throughout the United States have been safely storing used nuclear fuel in steel-lined concrete pools, and in 1986 began expanding capacity by adopting dry storage technology.

This proven technology involves sealing used fuel in airtight steel (or in steel and concrete) containers or casks that provide both structural strength and shielding and housing them in reinforced concrete structures.   Dry fuel storage is a passive cooling system with no moving parts. The fuel is kept cool by air entering vents in the structure and circulating around the outside of the steel canister.  The systems are designed to withstand various natural phenomena such as floods, projectiles from a tornado, seismic events, temperature extremes and lightning.

Read our FAQ about Dry Cask Storage at SONGS here.

Thirty-four states have at least one dry cask storage facility; these are formally known as Independent Spent Fuel Storage Installations. Eleven states currently have shutdown reactors without an operating reactor, including three in California. San Onofre, one of those three sites, has safely stored used nuclear fuel for more than three decades. San Onofre, one of those three sites, began safely storing used nuclear fuel also in dry cask storage in 2003.

Key Facts about San Onfore’s Fuel:

  • San Onofre Units 2 and 3 are pressurized water reactors; each held 217 fuel assemblies in the reactor core when operating.
  • After the plant was officially shutdown in June 2013, all fuel was removed from the reactor cores and placed in spent fuel pools.
  • San Onofre has about 2,668 fuel assemblies in spent fuel pools for Units 2 and 3.
  • There are about 800 Unit 2 and 3 fuel assemblies in canisters in dry cask storage.
  •  There are about 400 Unit 1 used nuclear fuel assemblies in dry cask storage on site.
  • In addition, there are 270 fuel assemblies for Unit 1 stored offsite at General Electric's used fuel storage facility in Morris, Ill.