NWS progresses GDF project 07 December 2022

Nuclear Waste Services boreholes  Rosemanowes The initiative is part of a programme that will support construction of a safe and secure GDF underground

Nuclear Waste Services (NWS) has sealed existing boreholes at Rosemanowes Quarry, Cornwall, as part of a £5 million project for the disposal of higher activity radioactive waste.

Drilling and sealing boreholes will be key in the search for a suitable site for a Geological Disposal Facility (GDF), which will dispose of waste which otherwise would have to be stored for thousands of years above ground.

The UK search for a suitable site is a nationwide process based on community consent and includes investigations. Community Partnerships, which have formed in Mid Copeland, South Copeland, and Allerdale in Cumbria, and Theddlethorpe in Lincolnshire, are engaging with local people to ensure they have access to information about what hosting a GDF might mean.

During the process of exploring if a site is suitable to host a GDF, deep boreholes will be drilled to investigate the geology of the location. NWS will then need to seal these boreholes as part of the site restoration programme to minimise the impact on the environment.

The initiative is part of a programme that will support construction of a safe and secure GDF underground.

During August and September, the latest phase was carried out at the quarry’s borehole test facility. Two pre-existing boreholes in granite, one 2km deep and the other 300m deep, were successfully sealed using a technology called a Downhole Placement System (DPS) tool.

Bentonite clay was used as the sealant because of its low permeability and swelling properties, with cement being used for seal support. Bentonite will also be packed around some GDF waste packages as part of the barrier system that will isolate and contain radioactive waste in a GDF.

A rig was used to lower the DPS filled with dry bentonite pellets into the borehole. On reaching the appropriate depth, the DPS was hydraulically activated, deploying the bentonite in the water column. In total, over a tonne of bentonite was deployed at depth, forming a seal as it swelled in both boreholes.

The results demonstrated that the bentonite could be released from the DPS into a borehole at 2km depth. The DPS tool is being tested in different locations with varying rock types and at varying borehole depths.

Prof Simon Norris, principal research manager at NWS, said: “The aim of this research project is to demonstrate the process we plan to use for sealing deep boreholes during future investigations into potential sites for a geological disposal facility.

“We want to show that we have the necessary toolkit of approaches, procedures, and equipment to seal any boreholes we may construct in the GDF siting process, and this research was a step closer to achieving this goal.”

Operations Engineer

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