For almost 70 years, nuclear power has been an integral part of the energy supply chain and it is currently experiencing a resurgence reflecting its green credentials. However, as much of it was built with haste and no focus on how to deal with it afterwards, the nuclear legacy left behind presents complex challenges to decommissioning in uniquely hazardous environments.
There is renewed excitement around nuclear with small modular reactor (SMR) technology and plans for new large light water reactors signalling the start of a new nuclear age. But for nuclear to remain a vital part of the energy mix, the industry needs to deal with the legacy of the previous age efficiently and cost-effectively to maintain positive public perception and support and protect future generations.
The buildings, plant and related infrastructure that comprise the nuclear legacy were not designed for decommissioning, follow no uniform structure or design and no unique solution can be deployed. They therefore require innovative solutions to enable their decommissioning and management of the generated wastes, drawing upon past learning and engagement of stakeholders to establish waste-led decommissioning approaches that optimise waste management practices aligned with the waste hierarchy.
Early definition of the decommissioning challenge for each facility and the options available to address them is fundamental to successful delivery. Whether developing decommissioning strategies, addressing waste disposal challenges or scrutinising engineering designs, adopting a methodical approach delivers outcomes that are underpinned and cost-efficient.
Data-led decision making
Waste-led decommissioning implies decommissioning with a focus on waste management. Historically, decommissioning approaches were often designed around the physical process of dismantling, with how the waste was to be managed left as an afterthought, resulting in much of the existing waste legacy that now needs to be dealt with. With the development of waste management infrastructure over the last 15 years, introducing a wider range of treatment and disposal options, there is now an increased focus on segregating wastes for optimised management aligned with the waste hierarchy, with a focus on accessing treatment routes rather than disposal. This change in waste management landscape has also increased scrutiny on the quality of waste characterisation data and demonstration of compliance with waste route acceptance criteria. Strategic planning tools such as Data Quality Objectives (DQO), supported by the development of waste-led process wiring diagrams (following IAEA recommendations), are tools that we typically use to clearly map out whole lifecycle requirements, challenges and opportunities from waste retrieval/generation through to final disposal. This approach ensures that management and data collection requirements at each step of the decommissioning and waste management lifecycle are identified and given appropriate consideration, including non-technical requirements, wider interfaces such as compatibility with treatment/disposal route acceptance criteria and workface implementability. This also forms the starting point for identifying waste management options aligned with the requirement to minimise radioactive waste disposal volumes and implement appropriate characterisation to support optimised waste routing.
Following a DQO-based approach allows for the development of underpinned, integrated strategies that consider technical and non-technical aspects, which can be de-risked at the earliest opportunity. Whether tackling nuclear waste or simple hedge trimmings in the garden, wiring diagrams can be developed to support a DQO exercise by identifying the long list of questions to support answering the problem statement.
The wiring diagram methodology was developed by the IAEA and follows the waste management lifecycle steps from retrieval of a waste stream to final disposal. For that waste stream, they will represent the baseline and potential alternative approaches for its management by identifying the needs, risks and opportunities associated with the implementation of these waste management approaches. The diagrams also become an extremely effective tool in communicating strategy preferences, challenges and opportunities to stakeholders.
Additionally, the use of a DQO exercise will identify any waste characterisation activities, such as waste characterisation on site, needed to support appropriate waste characterisation and disposability assessments for all waste types. This can include activities to demonstrate that some bulk demolition waste streams are non-radioactive (out of scope) to support the consignment of lower activity waste to appropriate treatment and disposal routes, and to support the management of higher activity waste pending – for example, segregation, treatment, conditioning, and interim storage – once a GDF becomes available.
Moreover, a DQO exercise, whilst identifying desk-based studies, will also identify modelling/trial activities that if delivered will give a useful insight to the general approach. Practical work through trials, training and simulation to mock-up or functionally to test an idea saves time and money and can be vital in validating a detailed design. Trials can also be carried out to reduce the risks to a project and, if a minor modification is required, be rapidly implemented and tested with minimal impact on the programme.
Author: Rob Thied, Head of Consultancy (North), NSG Environmental Ltd
