Decontamination and management of metals in decommissioning of nuclear installations

A nuclear facility, such as a nuclear power plant, contains large volumes of materials. Most of these materials are not radiologically contaminated. In a nuclear power plant, more than 99.9% of the radioactivity is inside the reactor vessel or next to the vessel.

From the reactor vessel, small amounts of radioactivity spread out in the systems and to a certain extent outside the systems whilst remaining contained within the facility. In decommissioning, all materials have to be managed properly in a structured way. Most contaminated materials, especially metals, are only contaminated on the surface.

If the surface is cleaned, the material is likely clean and possible to re-use or recycle outside the nuclear sector after verification measurements in line with the free release procedures.

Understanding the radiological status of the plant

In decommissioning, especially in the material and waste management area of decommissioning, it is essential to have a good understanding of the radiological status of the plant.

Through this knowledge, it will be possible to categorise the material depending on the risk of or measured level of radioactive contamination. Material which is considered to have no risk of contamination can be managed as conventional material while potentially contaminated material has to be cleared before it can be used and handled without restrictions.

Contaminated materials need to be decontaminated prior to going through the clearance process and recycling back to industry, when considered technically possible and economically reasonable, or be disposed of as radioactive waste.

In practice, one more dimension is added to the conventional sorting and segregation routines applied in the dismantling and demolition sector. In addition to the type of material and separation of hazardous substances, the radiological category has to be considered.

Treatment of contaminated metals.

Cyclife is a part of the French EDF Group, specialising in radioactive waste management and decommissioning services with facilities in France, Sweden and the UK.

The three key steps in the treatment process are: the separation of the radioactive contamination from the metal, the sampling for analyses to verify the radioactive content in the treated metal and the management of the residues containing the radioactivity.

These residues will have to be disposed of as radioactive waste while the metals are recycled into industry for use in new products.

Metal melting is a proven method for the separation of radioactivity and to establish conditions for high precision sampling and analyses of the remaining radioactivity. The entire treatment process, including the melting, is performed in isolated campaigns to allow return of the separated radioactivity to the nuclear facility where it was generated.

Only 2-3 percent of the total mass from decommissioning of a nuclear power plant has to be disposed of as radioactive waste. The rest of the material has either been cleaned throughout the entire lifetime of the facility or been decontaminated and cleared for reuse, recycling or conventional disposal.

Cost efficient decommissioning and sustainable metal management

In order to speed up decommissioning projects, to minimise investment on the decommissioning sites and to reduce the amount of waste for disposal, there is a strong preference to remove the material in as large pieces as possible.

In addition to the value of generating low-carbon electric power for several decades, the nuclear industry is taking strides towards a circular economy in the life cycle approach, including decommissioning.

NOTE. This article was written by: Mr. Arne Larsson
CYCLIFE SWEDEN AB VP TECHNOLOGY

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This article was featured in the 2020 edition of the publication. Access the full publication here:


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