What Is Nuclear Decommissioning?

Decommissioning of a nuclear facility is an action taken to fully consider the health and safety of workers and the public and environmental protection after the expiration of the life of a nuclear facility or suspension of service for other reasons. The ultimate goal of decommissioning is to achieve unrestricted opening and use of the site. The decommissioning of nuclear facilities does not include the closure of uranium mine waste rock yards and tailings depots and radioactive waste disposal (storage) sites ^[1] .

Decommissioning of a nuclear facility is an action taken to fully consider the health and safety of workers and the public and environmental protection after the expiration of the life of a nuclear facility or suspension of service for other reasons. The ultimate goal of decommissioning is to achieve unrestricted opening and use of the site. The decommissioning of nuclear facilities does not include the closure of uranium mine waste rock yards and tailings depots and radioactive waste disposal (storage) sites ^[1] .

Chinese name

Decommissioning of nuclear facilities

Foreign name

decommission of nuclear facilities

Subject

Nuclear geology

Definition

Public health and safety and environmental protection

Decommissioning strategy for nuclear facilities

Methods for decommissioning nuclear facilities include immediate dismantling, deferred dismantling, and in-situ burial. ^[2] There are many principles for selecting a decommissioning strategy. The main factors to be considered in the selection process include: social or political reasons, safety reasons, economic factors, site factors, and technological reasons. For example, reactor decommissioning and storage for an appropriate period of time can reduce the level of irradiation, and it is more advantageous to take delayed demolition. The nuclear fuel water smelting plant, purification plant, enrichment plant, component manufacturing plant and other nuclear fuel cycle front-end plants and spent fuel reprocessing plants are favored for immediate dismantling (see Figures 1 and 2). Uranium mines and uranium tailings reservoirs generally adopt measures such as soil cover vegetation and dam stabilization.

Figure 1 Before and after retirement of Winfrith Plutonium Fuel Plant in the UK

Figure 2 Before and after retirement of the Maine Yankee PWR in the United States

Decommissioning Technology (Process) for Nuclear Facilities

Decommissioning of nuclear facilities is a comprehensive project. Many technologies involved in decommissioning include source investigation, decontamination, dismantling and dismantling, waste management, radiation detection, radiation protection, site decontamination, etc. ^[3] .

Source item survey: It is conducted in the early stage of decommissioning. Through analysis and monitoring of radioactive and toxic and harmful source items in decommissioning facilities and sites, sufficient information is collected to formulate decommissioning strategies, select decommissioning plans, Optimization, estimation of decommissioning funds and exposure doses, formulation of decommissioning waste treatment and disposal plans, and decommissioning three major reports (feasibility study report, safety analysis report, and environmental impact assessment report) provide the basis.

Decontamination: A very important activity for decommissioning nuclear facilities. Decontamination in the decommissioning of nuclear facilities mainly includes mechanical, physical, chemical (including electrochemical), biological, and smelting methods. Decontamination of decommissioning of nuclear facilities runs through all stages of decommissioning.

Dismantling and dismantling: Cutting dismantling and dismantling and dismantling of nuclear facility systems, equipment and buildings (structures) are the main activities of decommissioning construction. Dismantling and dismantling are carried out through manual, mixed operation of remote control and remote control.

Waste management: The management of decommissioning waste is the last link of the entire decommissioning activity, and the management cost is an important part of the entire decommissioning cost ^[4] . Decommissioning often requires waste minimization and optimized waste management. Figure 3 is the composition data of the decommissioned waste at the Greifswald nuclear power plant in Germany.

Figure 3 Wastes generated during decommissioning of nuclear power plants and their proportion

Nuclear facility decommissioning history

Decommissioning of nuclear facilities has been proposed in the 1960s, but the emergence of more decommissioning projects occurred after the 1980s. It is roughly divided into 3 stages:

Phase : In the 1980s and 1990s, small research reactors, prototype reactor-type nuclear facilities, military nuclear facilities and some civilian radioactive pollution facilities (factories) began to be decommissioned from the 1940s to 1960s.

Phase : From the 1990s to the end of the 20th century, the nuclear power plants such as the Shiping Port Reactor in the United States, the Japan Power Demonstration Reactor, and the Nideraichbach in Germany began decommissioning of demonstration or intermediate reprocessing plants.

Phase III: Since the 21st century, many large nuclear facilities have been decommissioned, such as the decommissioning of the TPL of PPPL in the United States, the decommissioning of JET facilities and sites to be carried out in the United Kingdom, and the decommissioning of the JRR-2 reactor carried out in Japan, etc. ^[5] .