September 04 2022 0comment

Dismantling and demolition processes

Proven commercial dismantling techniques involving cutting for removing radioactive material from a facility, which are substantial in every decommissioning project, are described. The techniques have been applied successfully on an industrial scale in the dismantling of light-water reactors. Issues affecting the selection of various cutting technologies are discussed. Any successful application must be safe, reliable and cost effective, without being a hazard to people or the environment, and due consideration must be given to performance, effort, and collective dose, as well as the type and volume of any generated radioactive waste.

A few decontamination processes for dose-reduction purposes are also described. Factors allowing the selection of the appropriate technology are listed and discussed. Specific examples from the decommissioning of the Belgian BR3 reactor are summarized. The lessons learned since decommissioning started in 1987, both early and more recent experience, are outlined as a basis for future applications of the decommissioning technologies.

The basic technical background of technologies is presented for remote operation equipment and robotics for radiological characterization, retrieval, dismantling, demolition, decontamination, and other activities related to decommissioning. Overviews of state-of-the-art worldwide applications are given and expected future trends for their development and deployment are discussed.

Aspects of successful radioactive waste management are explored for decommissioning projects, including the availability of enough interim storage capacity for empty and filled radioactive waste packages. The need for storage space for decommissioning-generated material, whether it is to be recycled, reused or conventionally disposed of, is emphasised. Requirements for the treatment of radioactive waste are outlined including the operation of appropriate facilities for segregation, dismantling, segmentation, decontamination and final treatment of solid, liquid or gaseous material identified as radioactive waste, for example by supercompaction, incineration, evaporation, solidification (drying or cementation). The importance of reducing the volume of the waste, thus limiting the space needed in the interim storage facility and in the final repository, is emphasised. The role of precise radiological characterization of material in determining its potential for release, storage and/or disposal is examined.

The use of environmental remediation and restoration technologies in nuclear decommissioning projects is discussed. Criteria for choosing ex situ remediation techniques, including excavation, surface stabilisation, soil washing, chemical treatment and magnetic separation, or in situ treatment techniques, including natural attenuation, electroremediation, phytoremediation, bioremediation, vitrification, capping or cryogenic barriers, are examined. Treatment of contaminated groundwater is addressed and some particularly challenging aspects are explored, including the presence of long-lived isotopes and contamination at deep levels or over large areas. The potential applications of emerging technologies are indicated.