The accurate planning and estimating of decommissioning activities is an essential requisite in supporting and underpinning data concerning the anticipated cost and duration of discharge of the nuclear liability. Those owning the liability and funding the activities which have to be undertaken require robust data to allow strategy development and to ensure a timely availability of funds.
TÜV SÜD Nuclear Technologies has significant expertise in helping clients develop detailed project schedules and cost estimates with data being used to compile sanction grade estimates, funding applications and programme validation.
We have extensive experience in assisting clients with the development of Category Summary, Site Summary, Near Term Work Plans, Life Cycle Baseline, Baseline Development Plan documents and Scope Element documents which describe in detail all work activities to take place on a site.
We add value by developing new, innovative and, above all, appropriate methodologies to assist clients in their planning process. One example is the development of a parametric cost estimating tool which enables clients to develop robust costs for decommissioning based on implementing a Fragnet/logic underpinned by using actual volumes of waste materials at the site. This allows cost and waste information from many facilities to be combined into a single data source enabling clients to gain estimates of decommissioning costs. This methodology is now used at several client sites to underpin their delivery programmes.
Key to the effective delivery of nuclear site decommissioning activities is a “real” understanding of the challenge. This includes detailed knowledge of the facility to be decommissioned, its radioactive inventory and the extent of contamination. There also needs to be a clear comprehension of the constraints under which decommissioning of any facility will be undertaken. This includes allowable radioactive dose uptakes, availability of funding and the status of waste conditioning and packaging routes amongst many others. A clear understanding of the challenge and its context allows for the development of robust strategies.
TÜV SÜD Nuclear Technologies undertake decommissioning challenges by the application of a 'waste led' approach. This involves the application of wiring diagrams and a nodal approach to define, understand and communicate the challenges. This ensures an integrated, robust and holistic approach to the decommissioning challenge which will ultimately provide success.
Having understood the challenge we provide decommissioning guidance and input to strategies and methodologies at a range of levels. Typically, this is achieved by implementing a staged and structured approach involving a range of stakeholders. This usually entails the following discrete phases:
- Identification of study aims and constraints
- Identification of options
- Initial information gathering and coarse screening of options
- Gathering detailed information on remaining options
- In-depth assessment to identify and justify the preferred option(s)
- Development of preferred option through more detailed assessments
- Identification of further characterisation work to confirm assumptions and mitigate risks
Nuclear decommissioning can present many different and unique challenges. These can be broadly divided into two categories:
- Alpha - In these cases the radioactive sources within the facility predominantly concern alpha sources such as plutonium. The facility and waste can be contact handleable with the challenge being to avoid internal uptake to personnel.
- Beta/gamma facilities, where the challenge is the direct radiation which requires a remote or semi-remote approach.
Many isotopes such as tritium can bring their own unique challenges and the requirement for unique technical solutions.
TÜV SÜD Nuclear Technologies have amassed extensive experience on a large variety of decommissioning projects and therefore have a unique understanding of the tools and techniques which can be applied to any particular decommissioning challenge.
We approach any decommissioning challenge by 'applying a waste led approach' and endeavouring to understand how the decommissioning/waste retrievals step fits within the life cycle of the waste process.
For contact handleable waste we have a detailed understanding of techniques and tooling which can be applied and those issues which allow an ALARP approach to be defined.
For beta/gamma projects we have extensive knowledge of remote handling systems, tooling and size reduction techniques, including practical, hands on experience. We have learned through experience, which techniques will work and which will fail.
We are therefore able to help our clients define their options and identify the most appropriate decommissioning tools, methodologies and techniques.
Due to our independence we are able to provide advice, without any bias, on what equipment will achieve success.
Examples: TÜV SÜD Nuclear Technologies were engaged by Sellafield Ltd to consider methods by which alpha decommissioning projects might be improved with an objective of reducing the requirement on air fed suit operations which carry the inherent risk of contaminated wound incidents to personnel. We started by understanding why there is such a large dependence on air suit operations and provided a number of strategic options for managing the waste lifecycle in different ways. We went on to develop an ALARP tool kit to allow the decommissioning practitioner to select and substantiate the ALARP approach towards any task. This includes definition of the tooling and approach which might be taken to any task.
When radioactive material becomes associated with equipment, structures or facilities where its presence is detrimental to safety, the environment or operational/decommissioning activities, there can be requirement to undertake decontamination. Drivers for decontamination might include:
- In operational facilities, accumulations of deposits in pipe work, vessels etc can lead to process blockages, reduced process efficiency and safety issues
- Instances of containment breach can lead to elevated dose rates in work areas and also increase the risk of contamination spread
- During decommissioning there is often a need to undertake decontamination to reduce overall dose uptake and if appropriate to facilitate the use of manual intervention
- Decontamination can be used to facilitate the re-categorisation of waste with the aim of minimising the volume of material which is routed to the higher activity categories
For each challenge we seek to understand and characterise the problem such that the optimal decontamination solution can be defined. This involves gaining an appreciation of the substrate to be cleaned, the key properties of the contamination present and the extent of decontamination to be achieved. From the outset, we also seek to understand the waste routes available and their compatibility with down stream plants and processes.
Having defined the decontamination method we can provide the client with confidence in the applicability of the technique based on experience gained in similar situations elsewhere and usually via trials of the selected technique. Such trials are often done inactively using mock ups of the plant/equipment which require decontamination. We would develop the decontamination process until it is suitable for active facility deployment. This would also include the development of the accompanying safety case, method statements and waste routing justifications etc.