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Decommissioning: Residue and waste management

Both radioactive residues and deinstalled or dismantled radioactive plant components are the result of decommissioning a nuclear facility. According to § 9a of the Atomic Energy Act these must either be recycled safely (e.g. cleared or reused in another facility licensed under atomic or radiation protection legislation), or disposed of correctly as radioactive waste. Only a few percent of the total mass of the restricted access area has to be disposed of as radioactive waste.

So far, the experience with decommissioning projects has shown that a period of several years passes between the final shut-down and the starting of deinstallation of higher-contaminated or activated plant components that comprise the greatest part of the resulting radioactive waste. In the case of the nuclear power plant Obrigheim, which was shut-down in the year 2005 and whose decommissioning started in 2008, the deinstallation of plant components in the restricted access area started 6 years after the final shut-down. In the case of the nuclear power plant Stade, which was shut down in the year 2003 and has been under decommissioning since 2005, the deinstallation of high contaminated or activated plant components started 5 years after the final shut-down.

Various decommissioning options exist for residues and waste materials:

Clearance

Clearance is an administrative act effecting the release from nuclear supervision. It is regulated by § 29 of the Radiation Protection Ordinance, as well as appendices III and IV.

Measuring facility for clearance Greifswald Measuring facility for clearance GreifswaldMeasuring facility used for clearance of batches of residual material from the decommissioning of the Greifswald nuclear power plant (KGR). Source: EWN GmbH

Unrestricted clearance

In the case of unrestricted clearance, the relevant authority conducts the necessary administrative steps to release any residue from supervision as stipulated by the atomic legislation; these may then be reused, recycled or disposed of in the same way as standard waste.

Materials are only awarded unrestricted clearance if measurements show that they do not exceed the clearance threshold for unrestricted clearance as laid down in the Radiation Protection Ordinance. This means their release shall not cause individual members of the population to be exposed to an effective annual radiation dose of more than ten microsievert.

Specified clearance

A second option is that of specified clearance. This is applied to residues suitable for disposal in a conventional waste disposal or incineration facility, provided that the relevant clearance thresholds specified in § 29 of the Radiation Protection Ordinance are not superseded.

Specified clearance includes the clearance of solid materials for disposal, liquid substances for disposal, buildings for demolition, and scrap metal for recycling in a conventional melting plant.

Moreover, at a melting installation having a nuclear licence contaminated scrap metal may also be melted down in a controlled way if the clearance thresholds of the Radiation Protection Ordinance for specified release are exceeded.

Disposal as radioactive waste

Materials which can neither be recycled nor cleared must be disposed of as radioactive waste. An estimated 5,000 m3 of conditioned decommissioning waste is created by the decommissioning of a single nuclear power plant. Decommissioning waste is waste with negligible heat generation. The waste must be stored at an interim storage facility until the Konrad repository for low and medium radioactive waste becomes available. This generally takes place in an interim storage facility on the site of the plant.

Prior to transporting the radioactive waste to an interim storage facility or final repository, it must be treated appropriately (conditioned). Solid waste, for instance, undergoes compacting. Liquid waste is given a solid form, e.g. by means of drying/evaporation or cementation. When transporting conditioned waste to an interim storage facility, current traffic regulations must be observed. Special transportation containers and packaging must be used when moving any radioactive materials.

Decay storage

Reactor pressure vessel Rheinsberg Reactor pressure vessel Rheinsberg during consignementReactor pressure vessel from Rheinsberg nuclear power plant: consignment in interim storage facility north (Zwischenlager Nord - ZLN). Source: EWN GmbH

In the case of decay storage materials are stored for longer periods of time. The process of radioactive decay means that the activity of these materials gradually decreases.

Decay storage is used for dismantled scrap metal, for instance, as well as for large components such as reactor pressure vessels or steam generators. By reducing the activity of these large components, the idea is to enable simplified treatment at a later date while also reducing the quantity of radioactive waste, since once activity has decreased, clearance may even become a potential option.

The interim storage facility north (Zwischenlager Nord - ZLN) operated by EWN GmbH is used, among other things, as a storage facility for the decay storage of radioactive residual materials and waste that occur during plant decommissioning and dismantling.

State of 2016.10.11

© Federal Office for the Safety of Nuclear Waste Management