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Technology Factsheet

FriGeo

Category: Robotics > Characterization and Inspection > Underwater System
Reference # : Model No :

Sellafield are working with a Swedish company called FriGeo to develop a self-sinking probe to sample radioactive sludge from the bottom of a five-metre-deep legacy fuel storage pond.

The challenge posed was how to remotely collect samples of radioactive sludge up to 100cm deep from the bottom of the First Generation Magnox Storage Pond (FGMSP) at Sellafield, without disturbing the thick sludge bed or destroying the sample's characteristics.

The answer involved the development of a probe that could be remotely lowered into the sludge where it could pick up a sample from a predefined depth without disturbing the material.

FriGeo specialises in artificial freezing/stabilisation of sediment or ground, a technology which uses rapid freezing to solidify/stabilise an area of sediment for both dredging and salvage of objects, and from this was born the idea of freeze sampling.

Site:Sellafield
Industry:Maritime
Size:Very Large (>100kg/200lb, >120cm/48in)
TRL:Operational (9)
TRL2:Development (4-6)
Tether: *
Waterproof: *
Payload: *
Reach: *
Manipulator: *

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The concept of using a probe which fast-freezes a sample onto its surface means that the quality of the sample is likely to be preserved. There are no leaks, spills or dilutions and the sample can be easily recovered. Sellafield Ltd and FriGeo came up with the concept of using probes of different lengths to access and collect samples from a predefined depth in the sludge, which is up to 100cm deep in areas. FriGeo then pursued its idea of making a vibrating probe by borrowing technology from the construction industry. This vibrocore means that the probe is self-sinking, which helps to collect a sample from a predetermined depth. It operates at temperatures down to -40°C and the sludge sample is rapidly frozen onto the probe tip (in minutes), so importantly no sludge contamination drips from the probe when it is lifted out of the water.

FriGeo is undertaking Freeze Dredging of radioactive sludge at the disused nuclear power plant Bradwell in Essex in the United Kingdom. The project is commissioned by management and operations contractor Magnox South Sites.

Thanks to the innovative FriGeo method of Freeze Dredging, which limits direct human contact with radioactive material and radiation, the decontamination work at the former nuclear power plant can be carried out in a safe and efficient manner. The method also reduces the cost of after-treatment and storage of radioactive sludge. The dredging work at Bradwell is scheduled to be completed by early 2013.

Although initially developed for the FGMSP, freeze sampling could have extensive applications in the nuclear industry. A broad range of materials could be sampled, including sludges, wastes, toxic material and contaminated oils.

Development work on freeze technologies is progressing and more work will be carried out on assessing the capability of freezing processes for sampling and dredging. Improvement of these technologies will take in consideration the wider potential use of these tools both on the Sellafield site and in other nuclear decommissioning projects.

Operational Experience:

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