As we have written in previous articles, the United States Nuclear Regulatory Commission (USNRC) has strict rules governing nuclear power plant decommissioning, involving cleanup of radioactively contaminated plant systems and structures, and removal of the radioactive fuel.
The permanent closure of a nuclear power plant involves:
- Its safe removal from service.
- Dismantlement of the facility to the point that it no longer requires measures for radiation protection; i.e the radioactivity level is residual.
The Nuclear Energy Institute, which is the policy organization of the nuclear technologies industry, based in Washington, D.C., explains on its website:
The process involves decontaminating the facility to reduce residual radioactivity, dismantling the structures, removing contaminated materials to appropriate disposal facilities, storing used nuclear fuel until it can be removed from the site for disposal or consolidated storage, and releasing the property for other uses. The owner remains accountable to the NRC until decommissioning has been completed and the agency has terminated its license.
Advanced, integrated radiation detection and radioactivity measurement instruments, as well as chemical analyzers, help mitigate the threat and keep workers safe.
There are three ways to decommission: DECON, SAFSTOR, and ENTOM.
- DECON (Decontamination): Dismantling or removing all radioactive materials above acceptable limits. This step reduces the radiation level in the plant and minimizes the potential exposure to workers during subsequent decommissioning operations.
- SAFSTOR (Safe storage): Leaving the reactor intact but in a safe state. Highly radioactive components such as spent fuel are removed and placed in on-site storage while the surveillance and monitoring continue. This low initial cost process allows time for decay of radioactivity and the plant is dismantled in future years following steps like the DECON ones.
- ENTOM (Entombment): Permanently enclosing the facility on site into a condition that will allow the remaining radioactive material to be on-site without ever removing it.
According to the USNRC, DECON and SAFSTOCK are often used together, while ENTOM is a rarely used option.
Radiation exposure to the human body, contamination of skin, clothes, plant surfaces, air, or nearby water should be monitored while conducting decommissioning in any of these ways. Protecting workers is paramount and dose monitoring, air monitoring, and site screening should be utilized.
Dosimetry services offer accurate measurement of radiation dose exposure in the workplace, helping to ensure personnel safety in any environment where radiation exposure is a concern. There are electronic dosimeters that are used for active monitoring of employee exposure that feature a built-in telemetry option.
Site entry and exit screening involve several monitors that help detect radioactive material on personnel, clothing, and objects to help ensure contamination is not spread beyond the radiation control boundaries of a nuclear facility. Personnel contamination monitors identify surface contamination on the body, hands, and feet. Personnel gamma portal monitors provide simplified but advanced internal and external monitoring of workers well below clearance levels.
These requirements and the technologies used in the process are used in order to protect workers and the public during the entire decommissioning process and the public after the license is terminated.
Read about these technologies and more by downloading the ebook:
A Practical Guide to Radiation Safety During Nuclear Power Plant Decommissioning