When a power company decides to close a nuclear power plant permanently, the facility must be decommissioned by safely removing it from service and reducing residual radioactivity to a level that permits release of the property and termination of the operating license. The NRC has strict rules governing nuclear power plant decommissioning, involving cleanup of radioactively contaminated plant systems and structures and removal of the radioactive fuel. These requirements protect workers and the public during the entire decommissioning process and the public after the license is terminated.
The companies that operate nuclear power plants can use one or both of two options to decommission their facilities.
The first option is known as “DECON,” short for decontamination. With DECON, the first steps of taking the plant apart begin as soon as the fuel is removed from the reactor vessel. The operator first decontaminates or removes contaminated equipment and materials. The transfer of spent nuclear fuel into dry cask storage and the removal of equipment lowers the radiation level in the facility and significantly reduces the potential exposure to workers during subsequent decommissioning operations. DECON can take five years or more.
The second option is called “SAFSTOR,” for safe storage. This process takes much longer. After the fuel is removed from the reactor vessel, the plant is kept intact and placed in protective storage for an extended period of time. This allows the radioactive elements in components to decay to stable elements. During this time, the main components of the plant remain in place, including the reactor vessel, fuel pools, turbine and other elements. All fuel is removed from the reactor vessel and placed in fuel pools or dry storage on-site. The NRC continues to inspect the site and provides regulatory oversight of maintenance and security appropriate to the low risk profile of the site. The plant is dismantled in a process similar to the DECON option once radioactivity has decayed to lower levels and the safety risk to workers is substantially reduced. Generally, sites must spend no longer than 50 years in SAFSTOR to allow up to 10 years for decontamination. The entire process must be completed within 60 years.
According to the NRC website, eighteen commercial reactors in the United States are in the decommissioning process. Twelve of these reactors are using the SAFSTOR option, six are using the DECON option.
For more information about Decommissioning click on the link to U.S. Nuclear Regulatory Commission Decommissioning Information: https://www.nrc.gov/waste/decommissioning.html