Three innovative projects seek to inform MSSS retrievals operations

Three pioneering proof-of-concept (PoC) projects have been launched to tackle a critical challenge in the management of legacy nuclear waste retrievals at Sellafield Ltd, marking progress in the UK’s effort to safely decommission one of its most complex sites.

The projects are developing innovative solutions to measure liquor levels within the waste bed of the Magnox Swarf Storage Silos (MSSS) – a group of legacy storage facilities that are central to Sellafield’s decommissioning programme.

The challenge

Over the coming years, Sellafield Ltd will begin retrieval operations to empty the MSSS Original Building (OB), which contains legacy waste stored under a head of water. The water plays a vital role in shielding and cooling the waste.

During retrievals, it may be desirable to allow the water to drain below the surface of the waste bed. However, to protect the structural integrity of the silos, it is essential to monitor the liquor level within the waste bed to avoid differential hydrostatic pressures between the silos’ compartments. Without this monitoring, there is a risk of unbalanced forces acting on internal walls.

This is a complex task analogous to measuring groundwater levels in impermeable clay. In February 2024, Sellafield Ltd launched this challenge through the Game Changers innovation programme.

From application to PoC

Following the challenge call, nine applications were submitted and six projects received initial funding for feasibility studies. These included four potential solutions that would rely on the deployment of sensors inside the waste bed and two that proposed external, non-invasive imaging techniques using muon tomography.

In the autumn of 2024, the six candidates pitched for progression to the proof-of-concept phase. The following three were selected and commenced work in April 2025:

• Fraunhofer UK Research Ltd (Glasgow): This project employs Distributed Temperature Sensing (DTS) via fibre optic cables placed vertically within the waste bed. The aim is to use the resulting temperature profiles to infer the level of the liquor with high spatial resolution.
• Lynkeos Technology Ltd (Glasgow): Leveraging its expertise in muon tomography, Lynkeos is developing a solution based on detectors deployed externally to the silos enabling the passive generation of 3D images of the internal structure using naturally occurring cosmic-ray muons. This technique could potentially provide a non-invasive, ex-situ means of observing internal liquid distributions.
• Vista Clara (Washington State, USA): A leader in Nuclear Magnetic Resonance (NMR) geophysical sensing, Vista Clara is exploring the use of high-resolution NMR technology for detection of hydrogen in subsurface fluids. The concept involves deploying their proprietary NMR Dart™ probe inside a protective tube inserted into the waste bed to directly measure water content within the compartment.

Looking ahead

These projects are designed to validate the respective approaches at the hundreds of litres scale in a laboratory setting and are scheduled to report outcomes by the end of this calendar year.

If successful, the technologies could form the foundation for new monitoring systems that ensure safe, efficient, and informed waste retrieval operations in the years ahead.