Innovation needs in decommissioning

The nuclear industry has not fully exploited or implemented current technological capabilities, and too often relies on outdated technology to perform decommissioning tasks, suggests a report from the OECD Nuclear Energy Agency.

The report, 'R&D and Innovation Needs for Decommissioning Nuclear Facilities', calls for improvements to decrease the hundreds of billions of dollars that will be required to decommission facilities around the world. (Recent estimates of nuclear liabilities from various sources amount to $80 billion in France; $82 billion in the USA; $97 billion in the UK, based on the cost to decommission legacy facilities and operating reactors.)
The report says there is 'a powerful economic incentive' to fund development of more efficient decommissioning technologies due to the backlog of facilities awaiting or approaching decommissioning.

As of December 2013 according to IAEA figures, 149 nuclear power reactors had been shut down in 19 countries, including 32 in the United States, 29 in the United Kingdom, 27 in Germany, 12 in France and 11 in Japan. Decommissioning had only been completed for 17 of the world's permanently shut down reactors as of October 2010.

The backlog is expected to grow significantly over the next decade. NEA predicts that in Western Europe over 160 nuclear power plants are either already closed or to be closed by 2025, with over 60 in North America and more than 40 in Russia. There is also a large legacy of military and research reactors requiring decommissioning.

Barriers to innovation

Decommissioning is a complex process that takes years. In addition, the applicable strategies, practices and guidance vary widely due to the diverse nature of the facilities involved.

D&D strategies and practices are also driven by the marketplace, waste disposal options and regulatory requirements, which vary from country to country.

In general, decommissioning across the globe is being executed largely through the force of manual labour. This requires extensive personnel-protection measures, engineering controls, and detailed work planning and monitoring that is costly and inefficient to achieve the high levels of safety required. Although this approach is ubiquitous, it is clearly not as efficient as using remotely-operated robotic technologies. Modular, automated, remotely-operated technologies need to be assembled and field-tested in dismantling and material handling at facilities undergoing active decommissioning.

A significant factor that has stifled the adoption of new technologies, says the report, is that decommissioning tends to be sporadic and isolated. This lack of sustainability and coordination limits the potential 'payback' for capital expenditures required to incorporate and develop new technologies and practices. The cost-effectiveness of such efforts to date has tended to be evaluated on a project-by-project basis, rather than considered as an investment cost spread over multiple projects. The 'stop and go' nature of decommissioning also hinders the transfer of knowledge and technology among projects.

Despite these variations, there are certain features that D&D efforts tend to have in common. These include characterisation and survey, segmentation and dismantling, remediation and decontamination, material and waste. It is these areas that offer potential for international collaboration in R&D, as suggested by the report.

Promising technology

The report documents a vast array of promising current and future technologies that could be deployed today or developed in the future to accomplish the goal of better, cheaper, faster and safer decommissioning.

What is clear, however is that targeted, collaborative R&D funding, as well as strategies and funding to deploy, test, improve and redeploy technologies on current large-scale decommissioning projects, will be necessary to achieve this goal.

If lessons learned to refine existing technologies and durable R&D for decommissioning applications are not pursued, the industry will continue to have to adapt, tweak and assemble legacy technologies developed for other applications.

Key development areas

Characterisation / site monitoring
Modern geostatistical capabilities should be integrated into the characterisation and final status survey methodologies used to demonstrate compliance with the licence termination criterion.

Updated, scalable and modular fate and transport software needs to be developed and integrated with geostatistical capabilities to ensure that relatively simple and complex site end states and contaminant distributions can be modelled.

There is also a need to take advantage of advances in telemetry and satellite-based Internet connectivity to integrate mapping and sample and survey data acquisition with the fate and transport models and routine monitoring tasks.

Segmentation and dismantling
Segmentation and dismantling technologies specifically for reactor vessels and internals, steam generators, pressurisers and reactor coolant pumps and associated piping, have by and large been developmental, using off-the-shelf equipment adapted to decommissioning.

The report recommends basic research toward creating intelligent remote systems that can adapt to a variety of tasks and be readily-assembled from standardised modules, with special emphasis on actuators, universal operational software and virtual presence.

R&D could also focus on developing cutting technologies that minimise the generation of secondary wastes, and improved secondary waste collection and filtration methods.

Potential solutions could include the use of innovative cutting technologies such as arc saws and lasers for system, structure, component (SSC) and reactor vessel and internals segmentation.

Surface decontamination
Decontamination and remediation tends to rely on standard practices such as chemical treatment and abrasive, high pressure, mechanical surface removal.

Areas to be explored include achieving a better understanding of the chemical interactions and mobility of contaminants with substrates, and chemical and physical processes that can be used for decontamination of decommissioning materials such as concrete, metals, graphite, tank heels, groundwater and soil.

Innovative technologies include ligands that bind actinides, laser scabbling and decontamination, as well as cryogenic technologies. There are also prospects for expanded use of robotics and for more automated, modular decontamination processes.

Materials and waste management

Given the large volumes of legacy waste around the world, prioritised research in handling, stabilisation, encapsulation and containment, and co-ordinated development of stable, efficient disposal options, are and will continue to be critical.

Decontamination, recycling and reuse of decommissioning materials is also an important factor for reducing the volume of materials requiring disposal. The recycling and reuse of contaminated metal, concrete and graphite within the nuclear industry would greatly ease the burden on waste disposal facilities.

Reusing decommissioning material in new-build projects and the R&D necessary to process the materials such that they meet the new-build material standards is a worthwhile consideration in order to continuously reduce the decommissioning waste burden on waste disposal facilities.