Nuclear Fuel Cycle

- Overview

The nuclear fuel cycle includes front-end steps to prepare uranium for use in nuclear reactors and back-end steps to safely manage, prepare and dispose of spent (or spent) but still highly radioactive spent nuclear fuel. 

Uranium is the most widely used fuel for nuclear fission in nuclear power plants. Nuclear power plants use a certain type of uranium -- U-235 -- as fuel because its atoms split easily. While uranium is about 100 times more common than silver, U-235 is relatively rare, only slightly more than 0.7 percent of natural uranium. 

Uranium concentrate is separated from uranium ore at a uranium plant or from slurry at an in-situ leaching facility. It is then processed at conversion and enrichment facilities to increase U-235 levels to 3%–5% in commercial nuclear reactors, and made into reactor fuel pellets and fuel rods at the Reactor Fuel Fabrication Plant. 

Nuclear fuel is loaded into the reactor and used until the fuel assemblies become highly radioactive and must be removed for interim storage and eventual disposal. Chemical processing of spent fuel material to recover any remaining products that may re-fission in new fuel assemblies is technically feasible, but not permitted in the United States.

- At the Reactor

After the fuel assemblies are manufactured, trucks transport them to the reactor site. Fuel assemblies are stored on-site in fresh fuel storage tanks until they are needed by the reactor operator. At this stage, uranium is only slightly radioactive, and essentially all of the radiation is contained within the metal tube. Typically, reactor operators replace about one-third of the reactor core (40 to 90 fuel assemblies) every 12 to 24 months. 

The reactor core is a cylindrical arrangement of fuel bundles, about 12 feet in diameter and 14 feet high, housed in a steel pressure vessel with walls a few inches thick. The reactor core has essentially no moving parts, save for a handful of control rods inserted to regulate the nuclear fission reaction. Placing fuel assemblies next to each other and adding water triggers nuclear reaction