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Technology Factsheet

Adapted Mini-Digger

Category: Robotics > Dismantling and Retrieval > Underwater System
Reference # : Model No :

An adapted mini-digger used in R1 ponds. Bradwell, Chapelcross, Hinkley Point, Hunterston A.

Modification of a mini-digger to replace the electrical drive systems with water powered hydraulics, thus enabling underwater operations for such tasks as bulk sludge recovery.

Site:Magnox
Industry:Construction
Size:Very Large (>100kg/200lb, >120cm/48in)
TRL:Operational (9)
TRL2:Operational (9)
Tether: *
Waterproof: *
Payload: *
Reach: *
Manipulator: *

Benefits

Limitations

Comments

Following commissioning trials, the ROV was deployed into the pond—it would need to survive a depth of 20 feet for three weeks. The ROV worked for 326 days without fault or leak, clearing the debris effortlessly and re-handling everything from scaffold poles to fuel element debris without any problems. It proved to be easy to operate through a TV screen system with the only difficulty being the clouds of sludge which would blind the cameras.

Upon completion of the task, the ROV was recovered with the intention of retiring it and disposing of it throughout the waste stream. However, the sister Bradwell site in Essex had similar issues so the decision was made to redeploy the ROV at that site. Again, it proved successful in difficult conditions and worked a further 253 days without significant problems.

During this period, the ROV won the prestigious i4 award for innovation held in the UK each year.

By this time the ROV was nearing the end of its working life, generally due to the age of the donor unit. A decision was made to build two more ROVs using new JCB micro excavators as the base vehicles.

Although the new units are operationally the same as the prototype, they are larger and more powerful. The new ROVS are piped to take additional tooling, including underwater cutting equipment, and have been built with rotating grabs as an alternative to the digger bucket. One of these ROVs is currently deployed in the pond at the Hunterston A site in Scotland. The cost of these machines was £25k each.

Future plans for ROVs include the addition of diamond disc cutting equipment and manipulators, and adaption for the mounting of core drilling equipment. The ROV has proven to be adaptable and robust, and has become standard equipment in the Magnox toolbox.

Manufacturer Information: Magnox used a secondhand machine from a dealership in the UK was contacted, who had recently received a consignment of machines from a water company in Osaka, Japan. A visit to their premises provided a machine suitable for conversion for £3000. Once delivered to Site it was quickly dismantled and reconditioned where necessary (including one hydraulic ram seal at a cost of £10) with the cab, engine and seating being removed. All aluminium components were replaced or sealed with an epoxy resin. After finding a hydraulic power pack on-site, previously used for running a set of shears, the excavator control module was connected to the excavator via a 150-foot run of caustic resistant plastic hydraulic hose. Necessary ballast (concrete kerbing stones) was added and the excavator and power unit were filled with a biodegradable vegetable oil in place of mineral hydraulic fluid. Fishing net floats were added to the umbilical at intervals to assist with buoyancy. A talon was welded to the boom enabling items to be gripped between it and the excavator bucket. As a rudimentary hand it proved to be very useful. Once budget underwater video cameras were fitted (at a cost of £15k), the ROV was ready for deployment.

Operational Experience:

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