Nuclear Waste Services (NWS), part of the UK Nuclear Decommissioning Authority (NDA), has begun work on the final capping of historic trenches and vaults which are now full and ready for permanent closure at the UK’s low-level radioactive waste (LLW) repository near Drigg in Cumbria.

When LLW disposal started in 1959, the waste was tipped into lined trenches at the repository site. Disposal techniques evolved during the late 1980s and early 1990s through the construction of highly engineered concrete vaults. This resulted in an innovative approach to LLW treatment and safe disposal in specially designed metal containers, which were placed in engineered vaults at the site.

A long-term programme is now underway to permanently close the existing vaults and adjacent trenches – and initial work on the ground has now begun. NWS says this work is key to its mission to make nuclear waste permanently safe, sooner, which is vitally important to the UK and future generations.

The initial work of the Capping Operations is now progressing, and will take five years. This first phase, Southern Trench Cap Interim Membrane (STIM) project, will see a replacement membrane put in place over some of the trenches to continue to protect the waste and this will remain in place for up to 100 years.

Mike Pigott, Director of Sites & Operations for NWS, said the LLW repository is “an important national asset and is critical to delivering the Nuclear Waste Services mission”. He added: “I am pleased we’re progressing work on this long-term project with work commencing on site for this phase, it is vitally important that NWS caps the existing vaults and trenches to provide long-term protection to the wastes and the environment for generations to come.”

He explained that NWS was making good progress on the project with a cap design agreed, infrastructure in place to deliver this work and permission to build the cap granted by the local authority. “We will continue to work with our community to maintain our social licence to operate and are committed to being a considerate neighbour whilst delivering our important mission.”

NWS has been engaging with the local community with drop-in sessions and site tours to share more details about what residents will see and hear over the next 6-12 months of operations. Plans are in place to mitigate and minimise any associated noise, dust, traffic, ecological and visual impacts. This includes the installation of noise barriers and visual screening bunds, regular noise monitoring of activities and a commitment to bring the majority of aggregate and materials to the site via rail.

NWS is currently engaging with the supply chain to select the contractor for the next phase of the project, which is planned to be phased over four years and expected to start late in 2024.

Most radioactive waste arising in the UK is LLW or Very Low Level (VLLW). NWS delivers solutions for this waste, including at the Low Level Waste Repository (LLWR) in Cumbria – the UK’s primary LLW disposal facility.

Image: The Southern Trench Cap Interim Membrane (STIM) project (courtesy of NWS)