One of the key decisions for decommissioning is whether it will be performed remotely or will be hands-on, with operators using tools directly. It will often be cheaper and easier to use manual techniques since this allows maximum

3500000

Unknown, 116

Wood, 19836

flexibility in choosing appropriate tools and allows parallel working to reduce the time required for decommissioning. However, manual decommissioning may not be possible if radiation levels are too high.

Manual decommissioning can exploit hand tools as well as sit-on machinery. Remote decommissioning uses manipulators and other tools mounted on cranes or remotely-operated-vehicles and directed by operators using a camera for guidance.

Decommissioning may try to separate different waste categories such as intermediate and low level wastes from free release material. In some cases physical techniques such as cutting, scabbling a surface, water jetting or sand blasting might be used.13 In other instances chemical decontamination might
offer advantages. In each case the cost and environmental benefits of per­forming the operation must be weighed against the cost, resource usage and dose incurred by further processing the waste. Some methods for decontami­nation are discussed.14 Decontamination to support decommissioning can use more aggressive chemicals than are used for cleaning equipment prior to maintenance during plant operations, it is also possible to deploy decontami­nation either in situ prior to removal of items or ex situ after they are removed from their original location.

Examples of the successful decontamination of streams are the Berkeley fuelling machines: 1700 tonnes of which were recycled, 60 tonnes of which were disposed as LLW, while 30 tonnes remain in store awaiting disposal. Chemical cleaning of the Berkeley gas ducts allowed 750 tonnes of steel to be recycled.