IAEA considerations on nuclear decommissioning, decontamination and waste management
31/08/2020
Article by Mr. Vladimir Michal and Ms. Rebecca Robbins (IAEA International Atomic Energy Agency) included in EDI Special Publication 2020
The peaceful use of nuclear technology, either to produce electricity or other applications, inevitably leads to facilities and equipment that are radiologically contaminated.
These include nuclear power plants, research reactors, reprocessing facilities and other small research, medical and industrial facilities.
The nuclear industry uses the term ‘decommissioning’ to describe the removal of a facility from regulatory control.
Decommissioning covers the spectrum of activities from planning, physical and radiological characterization, decontamination, dismantling, demolition and management of the material and waste generated.
Decommissioning of nuclear facilities has all the complexities associated with conventional industrial decontamination and demolition but with the extra challenges of potential radiological exposure and radiologically contaminated hazardous material.
The IAEA provides guidance by a variety of means to Member States on how to approach and implement their decommissioning activities.
Decontamination and Decommissioning
Decontamination during decommissioning is used not only to reduce radiation levels but also to minimize the volume of radioactive waste consigned to disposal through facilitation of unrestricted reuse or recycle of materials and components.
An integrated approach which considers and balances many factors is essential to optimize the costs, benefits and safety of nuclear facility decommissioning operations.
Decontamination methods must be selected based on effectiveness, compatibility with the system or component, secondary waste generation and disposal, as well as radiological and industrial safety.
The optimal balance must be established between all these factors for the selection of a preferred decontamination process.
In some cases, decontamination may only be of marginal benefit and its costs may offset the benefits: if this is the case the best approach may be not to decontaminate, but to directly dispose.
A variety of chemical, electrochemical, mechanical methods are available to decontaminate metallic, concrete and other types of surfaces and components in nuclear facilities.
For example, decommissioning of nuclear power plants often generates radioactively contaminated large metallic items such as steam generators.
These components are often subject to melting in specialized facilities to separate the radioactive components and allow the clean metal to be recycled.
Decommissioning of nuclear facilities can also generate hazardous waste that is also radioactively contaminated.
Examples include asbestos, lead, mercury, polychlorinated biphenyls (PCBs) and organic solvents.
Such materials present a challenge as often disposal facilities for radioactive waste do not allow the disposal of large amounts of hazardous or organic material.
Some inorganic materials may be decontaminated to remove the radioactive constituents and recycled (for example large volumes of mercury or lead) outside of the nuclear industry.
While other types of material, particularly contaminated organic material (e.g. PCBs and solvents), need thermal treatment in a facility that is licensed to treat both radioactive and hazardous components.
Good record keeping, and waste minimization practices employed during the operational phase of the facility can facilitate downstream waste management and minimize the amount of material ultimately classified as radioactive waste during decommissioning.
