In-situ Raman Spectroscopy of Sludge

Research Area:

Waste and Fuel Management

PI:

Prof. Thomas Scott,  University of Bristol

Partners:

Sellafield Ltd.

Contact details:

Kate Wyness, kw14747@bristol.ac.uk

The Challenge

Currently there are two legacy storage pond facilities based in Sellafield, Cumbria, the largest decommissioning and processing plant in the UK. These facilities were originally built to handle waste from the 1950’s plutonium breeder reactors, and therefore comprise of vast ponds filled with MAGNOX fuel and cladding. As a result of several decades of passive storage, severe corrosion has occurred in the base of the ponds, forming approximately 1500 m3 of a heterogeneous waste sludge material.

The high radioactivity and access restrictions imposed within these facilities makes in-situ characterisation studies extremely challenging, with none having been performed to date.

The aim of this project is to therefore utilise Raman spectroscopy techniques to characterise the complex sludge material, such that suitable strategies can be developed for the safe and efficient processing and eventual disposal of sludge material.

Figure 1 - sludge retrieval in action. This uses a large vacuum pump to transport the waste into a separate tank elsewhere on the Sellafield site.

The Solution

Raman Spectroscopy is a characterisation technique that provides chemical analysis of complex chemical compounds. Illuminating a sample with a monochromatic laser, induces interactions with molecular vibrations, phonons and additional excitations within the material causing a shift in the laser energy.

This energy shift can then be analysed to provide a fingerprint by which a wide range of molecules can be identified. The aim of this project is to miniaturise this technology and develop a probe which can be deployed within the Sellafield storage pond, to provide effective in-situ chemical characterisation.

The Impact

Figure 2 - example of a prototype Raman spectroscopy probe, used for chemical sludge characterisation.

The use of stand-off spectroscopy to characterise the sludge contained within Sellafield's radioactive ponds would provide chemical information, imperative to the UK nuclear clean up mission. Currently the ponds can be monitored via video delivered through an ROV system, and water chemistry can be systematically checked through experimental sampling.

However, pond corrosion cannot be chemically sampled in-situ. With the advent of such technology, pond composition could be continually mapped, such that fuel ‘hot spots’ can be identified and then processed for alternate HLW storage. This separation of waste will mean a more efficient clean up strategy and accelerate long-term storage procedures.

 

Waste and Fuel Management - In-situ Raman Spectroscopy of Sludge

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