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29 November 2022
Existing boreholes at Rosmanowes Quarry in Cornwall, southwest England, have been successfully sealed by Nuclear Waste Services (NWS), in a demonstration of the technology it uses to seal boreholes drilled during the search to find a suitable location for a geological disposal facility. (GDF) in the UK.
Demonstration of Borehole Sealing Technology at Rozmenowes (Image: NWS)
The UK’s search for a suitable site is a nationwide process based on community consent and involves several years of detailed investigation. Community partnerships, which are formed in Mid Copland, South Copland and Allerdale in Cumbria and Thedlethorpe in Lincolnshire, are engaged in dialogue with local people so that they have access to information about what hosting a GDF could mean.
During the process of finding out if a site is suitable to host a GDF, deep boreholes will be drilled to examine the geology of the location. The NWS will then be required to seal these boreholes as part of a site restoration program to minimize the impact on the environment.
The NWS is running a project – costing more than GBP5 million (USD6 million) – to investigate and demonstrate its approach to deep borehole sealing to regulators.
The latest phase of the project was carried out at the Borehole Test Facility at Rosmenoves Quarry. The site, a former working mine, now provides access to one of the most extensively mapped well systems in the world, the NWS said.
Two pre-existing boreholes in granite – one 2 kilometers deep and the other 300 meters deep – were successfully sealed using an innovative technology called the Downhole Placement System (DPS) tool.
Bentonite clay was used as a sealant due to its low permeability and swelling properties, with cement used for the base of the seal. Commonly found worldwide and used in international waste management programs, bentonite will also be packaged around some GDF waste packages as part of an engineered barrier system that will separate and contain waste disposed of in UK GDFs.
The DPS tool is being tested at different locations on different rock types and at different borehole depths. The first successful test was carried out in 2018 in a 200-metre borehole in Sweden, followed by a 300-metre borehole in soil in Harwell, Oxfordshire.
“The purpose of this research project is to demonstrate the process we plan to use to seal deep boreholes during future investigations of potential sites for a geological disposal facility,” said Simon Norris, NWS principal research manager and project technical lead. “We wanted to show that we have the necessary toolkit of approaches, procedures and equipment to seal any borehole we can create in the GDF siting process, and this research was one step closer to achieving this goal.”
The GDF consists of a network of highly-engineered underground vaults and tunnels built to permanently dispose of high-activity radioactive waste so that no harmful levels of radiation ever reach the surface environment. Countries like Finland, Sweden, France, Canada and USA are also following this option.
Researched and written by World Nuclear News
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