July 16, 2021
July’s BDA webinar took place Wednesday 14th July 2021 and looked at the interesting topic of “Sealing Deep Site Investigation Boreholes: Radioactive Waste Management’s (RWM) Field Demonstration Activities”.
The webinar was presented by Dr Simon Norris, Principal Research Manager, RWM, and after introducing the partner organisations on the project, he began with what RWM is doing in consideration of the position of the regulator, the Environment Agency (EA), and the draft guidance working towards preparing an initial site evaluation in respect to locating a Geological Disposal Facility (GDF) for the nation’s higher activity radioactive waste the UK. Site investigations associated with the GDF will require the drilling of deep boreholes, and the needs RWM to demonstrate it knows how to seal boreholes before it will give permission for their drilling. Note that safety case for the GDF considers site evolution on the one million year timescale – long-term seal performance is very important!
Simon then moved onto RWM’s top claim in its claims-arguments-evidence approach, which states: “Boreholes can be located, drilled and sealed to reduce the likelihood of GDF-related geosphere isolation and containment functionality being detrimentally affected and to ensure discrete groundwater units are not inadvertently connected.” Against this back drop he then spoke about the project objectives and how they are looking to develop approaches for sealing deep site investigation boreholes as well as to cover the range of generic geological settings (host rock and surrounding geology) potentially relevant for a UK GDF against groundwater and gas movement, recognising specific borehole parameters.
RWM’s achievements to-date were then discussed from the project’s initiation in 2013 through to its present work tendered to December 2022, broken into four phases. The work being planned for Phase Five of the contract was described, which will enable the timely deployment of further work as GDF Siting progresses and as further technical needs arise.
The use of the existing knowledge base was described and how it helped the project, before moving on to talk about ‘Sealing Concepts – Lower Strength Sedimentary Rocks and Evaporites’ and ‘Rocks with Discrete Fractures’. The choice of seal material was then introduced and the development of the Downhole Placement Systems (DPS) was presented. The large-scale laboratory tests undertaken were explained and then Simon explained the Workflow for design and installing borehole sealing systems.
From field demonstrations, ground surveys and pad construction through to the deployment of bentonite via the DPS were discussed for two sites (Simpevarp and Harwell), followed by a detailed look at borehole instability encountered at Harwell and overall field demonstration learning to date.
The presentation then moved on to the potential scope of Phase Five of the project and some of the key elements the project is looking to explore, before Simon presented a summary of RWM’s borehole sealing project to-date.
A questions and answers session closed the presentation.
A link to the webinar recording is available here: https://vimeo.com/574904561