Improved radioactive waste analysis

Project

Non-intrusive, real time characterisation toolkit

Benefits

MFC can determine the internal activity of items without the time and expense associated with model-based characterisation techniques.

Current Status

The tool is now available for activity assessment for planning purposes. A package of work is planned for next year to further develop and substantiate this tool and allow it to be used for sentencing.

Delivery Partners

AtkinsRéalis, Cavendish Nuclear Ltd

Contact Details

Rochelle Heyhoe, Johnny Perry, Eryk Ryzko

innovation.team@sellafieldsites.com

Model Free Characterisation (MFC) is a new and innovative technique developed by Cavendish Nuclear to perform radioactive waste analysis. The MFC technique has the potential to improve radioactive waste analysis of items with complex geometries (such as those present in storage ponds) for the Sellafield site, as well as the wider NDA estate.

When performing waste characterisation, a ‘model’ is nearly always necessary to convert the signal measured into the activity present. Constructing the model itself can be a time consuming process. In most cases, the time taken to develop the model and to perform the analysis is far longer than the time taken to perform the measurement of the item itself.

The existing technique for this type of measurement is to use High Resolution Gamma Spectrometry (HRGS) and In-Situ Object Counting System (ISOCS). This requires complex computer models to be produced detailing material types, densities, or phyiscal dimensions of the item to convert measured count rates into activities. The production of these models is expensive, time consuming, and requires a specialist technician of which there is a shortage.

However, MFC requires no knowledge of the physical construction, such as material types, densities, physical dimensions of the item to generate a model. It only requires the external ‘shape’ of the item and its relative location with respect to the measurement locations themselves.

MFC involves performing multiple gamma spectrometry measurements around an item. At each measurement location, the ‘shape’ of the gamma spectrum measured is analysed. A simple 3D ‘free space’ representation of the item’s volume is all that is required to determine the amount of activity present. This technique can now be used for planning purposes and the intent is to develop it further over the next 12 months to allow sentencing of waste items.