Development of thermal treatment solutions for higher activity nuclear wastes

TÜV SÜD has been supporting the Sellafield Ltd programme since 2016 and now provides ongoing technical expertise to understand the demand on potential future treatment facilities.

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Summary

Client name:  Sellafield Ltd

Industry:  Nuclear

Company profile:  Part of the NDA Group, an organisation responsible for cleaning-up the country’s highest nuclear risks and hazards, safe guarding nuclear fuel, material and waste.

Business challenge:  To develop and maintain waste order books to support the treatment programme, assess characteristics and explore opportunities for alternative disposal methods.

Our solution:  Facilitation of workshops, desk top research, data analysis and stakeholder engagement.

Business benefits:  Robust waste order books and research to enable decision making. Long term client / consultant relationship that responds to a changing environment.

Business Challenge

The Nuclear Decommissioning Authority (NDA) is progressing the expansion of the toolbox of treatment options for higher activity waste (HAW) and has supported the development of thermal technologies over many years such that they can be considered as credible alternatives to conventional grout encapsulation when key waste treatment decisions are taken. Thermal treatment can offer advantages over grout encapsulation by reducing overall waste package volumes and producing passive wasteforms. Initially, focussed research and development was undertaken by a multi-disciplined integrated project team, to demonstrate the feasibility of the technology with simulated materials and in 2021, Sellafield Ltd established the HAW thermal treatment programme. This team has been progressing opportunities for processing plutonium contaminated materials (PCM), pumpable wastes and mixed beta gamma solid wastes from across the NDA estate.

To understand the demand on future treatment facilities, work has been ongoing to determine the volumes and investigate the nature and characteristics of potential feeds to thermal treatment facilities, with TÜV SÜD support. Comparison was then made with the characteristics of a range of solid beta / gamma wastes to identify potential areas of future opportunity. The study was a first attempt at exploring potential links between thermally treated wastes and near surface disposal, recognising that acceptance criteria associated with a UK near surface disposal concept will be dependent on a complex range of factors.

Business Benefits

The TÜV SÜD project team has a strong working relationship with the Sellafield Ltd led thermal team, established over many years. As such the team has gained extensive knowledge of the programme and has provided independent technical expertise and underpinning information throughout the lifetime of the project and is therefore able to respond to a rapidly changing environment whilst completing high quality deliverables.

Solution

TÜV SÜD support over recent years has primarily focussed on the following scope which aims to address the uncertainties associated with complex feeds and new treatment options:

Live waste order book development and maintenance

By collating data from the UK Radioactive Waste Inventory and waste producers, order books have been prepared and maintained. They capture the range of candidate feeds that could be available for HAW thermal treatment and include data such as feed volumes, their origin, characteristics and how they are currently stored.

Characterisation

TÜV SÜD carried out a high-level evaluation of the waste characterisation requirements associated with thermal treatment of PCM. The objective of the exercise was to establish an early basis for future ‘conditions for acceptance’ for a thermal process by highlighting potential waste components that may need to be excluded or controlled within any of the process feeds. The study involved a workshop discussion supported by subject matter experts which highlighted potentially challenging materials that will inform future characterisation needs.

Miscellaneous plutonium residues
The team recently completed a study on the technical feasibility of thermally treating various plutonium residue streams, identifying key technical challenges in relation to processing and the potential disposability of various residues. It also explored opportunities for including simulated residue packages as feeds to proposed prototype trials to further understand their behaviour in a thermally treated system.

An assessment of alternative disposal options
TÜV SÜD carried out a preliminary assessment of potential opportunities to utilise near surface disposal as an option for thermally treated wasteforms. The waste acceptance criteria for a range of global facilities were reviewed and used to inform potential boundary thresholds for intermediate level waste disposal in this type of facility.


“The support to HAWTT Tranche 3 brought a positive and different dimension to the strategic scope with the breadth of knowledge provided. The TÜV SÜD team showed strength in depth and were available to help unlock problems that were not always obvious.”

Chris Mounsey, HAWTT Programme
Manager, Sellafield Ltd


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