Nuclear power plant decommissioning or nuclear decommissioning is the process by which a nuclear power plant is dismantled to the point that radiation protection measures are no longer necessary. The presence of radioactive material requires processes that are classified as occupationally hazardous, a threat to the natural environment, expensive and time-intensive.[1]​.

The dismantling of nuclear power plants is distinguished from 'conventional' dismantling in the existence of radioactive or fissile materials that require special treatment measures.

Dismantling involves various technical administrative actions, including decontamination and progressive demolition of the plant. Once the facility is dismantled, there should be no risk of radioactive accidents that could affect people. After the facilities have been completely decommissioned, they are no longer under the need for regulatory control by the respective authority and the plant concessionaire is no longer responsible for compliance with nuclear safety standards. The dismantling can be until reaching the state of a "virgin land".

The objectives sought in the dismantling are:

The International Atomic Energy Agency has defined three options for decommissioning:

One of the key factors to be able to correctly carry out the dismantling of a nuclear facility is to have a radiological inventory, since it is key to say both the method of dismantling and its planning. The degree of decontamination and the transfer and treatment of radioactive material is a direct function of the type and magnitude of the radioactive source. An accurate inventory is necessary to estimate worker exposures as well as environmental impacts.

Depending on their origin, radioactive materials can be:

It is necessary to create a dismantling plan that serves as a basis for organizing the activities to be carried out by the participants in the project, as well as for informing the regulatory authority in order to obtain the necessary permits. The plan must consider the decontamination criteria, including the limits of acceptable surface contamination and final dispersed activity.