Wriggling robots eye nuclear sites

19 February 2009

Robotic snakes and worms are helping operators inspect pipework and carry out repairs in confined and inaccessible areas of their nuclear plants and sites.

Snake-arm robot (OC Robotics)
A snake-arm robot inspecting beneath a reactor (Image: OC Robotics)
OC Robotics of the UK has just been awarded a contract by Canada's Ontario Power Generation (OPG) to design and make a snake-arm robot mounted on a mobile vehicle that will be used to inspect complex pipework and structures within its Candu reactors.
Snake-arm robots are flexible robotic arms which have many joints so they can "follow their nose" into confined spaces. The snake-arm to be manufactured for OPG will be 2 m in length and will have a rectangular cross-section measuring 25 mm in width and 50 mm in height. In the first instance the snake-arm will be equipped with tip cameras for pipe inspection.
OC Robotics completed its first commercial nuclear contract in 2004. Working with Uddcomb, OC Robotics supplied two types of robot (five in total) to Ringhals in Sweden to complete an urgent pipe replacement in an extremely awkward area below one of their reactors.
Replacing the leaking section of pipe at the Ringhals plant involved more than 30 distinct procedures with the majority being conducted by the robots working cooperatively. The more flexible snake-arm was used to get the ideal camera location to monitor the process whilst the other snake-arm was used to deliver the processing tools and fixtures, remove the old pipe, introduce the new pipe and conduct tasks such as welding and inspection. The actual pipe repair was completed within three days.
Worm's eye view at Dounreay
Meanwhile, at the Dounreay nuclear site in the UK, a hi-tech 'worm' is being used to inspect underground pipes used to discharge radioactive effluent from fast reactor experiments conducted between 1957 and 1992.
The 23 cm-diameter cast iron pipes, some 45 m underground, are connected on the surface to two disused tanks where effluent drained from the reactors, chemical plants and waste facilities. They are encased in the concrete wall of a tunnel that extends some 600 m offshore. When construction of the tunnel was completed in 1957 but it was since abandoned and allowed to flood.
The pipe crawler, costing some £100,000 ($144,000), has sent back video and radiation readings during its five-day journey through the pipes. The data will be analysed by a project team investigating how to leave the disused system in a safe condition as part of the site clean-up.
The head of the 'worm' is 2.5 m long and 15 cm in diameter. Its flexible tracked chassis can turn through bends in the pipes. An umbilical 'tail' allows the pipeline crawler to be controlled remotely from the surface.
Martin Howes, project manager with Dounreay Site Restoration Ltd, said: "The remotely-operated vehicle will allow us to inspect the inside of the pipes. We are looking for signs of structural degradation, trapped debris and radioactive contamination."
He added, "The findings will allow us to reach some judgements about the best course of action. It is our intention to present a proposal to the Scottish Environment Protection Agency by December."