Superfund cleanup sites are not places you really want to hang around. So how does one survey a radioactive fuel storage pond without taking a dip? Send in a radiation-resistant ROV, of course.
The First Generation Magnox Storage and De-canning Facility (MSDF) is one such radioactive location. It was constructed in the 1950s at Sellafield near Cumbria, England. During its operation, the site was instrumental in the UK's civil nuclear power program. However, in 1974, circumstances required nuclear material to remain submerged for longer than normal. This corroded the ponds and clouded the waters, which in turn slowed the rest of the decontamination process and created a chain reaction of delays.
By 1992, the MSDF had been replaced by the Fuel Handling Plant at Sellafield and was used simply as a storage site for several types of nuclear material. According to Sellafield LTD, the company charged with the cleanup, each form of waste requires a separate cleaning method. To know how much of each type resided in each of Sellafield's numerous holding ponds, a survey was in order. However, since very few people volunteered to dive in the ponds and start counting, an alternate solution was devised. One with robots.
Enter the ROVTECH Systems Seaker Nuclear ROV. This meter-long robotic vessel is very similar to those employed in deep sea oil-drilling and scientific operations. It's powered by a series of four stainless steel thrusters, and it carries three colour cameras, LED lamps, radiation sensors and a 520p video camera. All power, control and information flows between the ROV and its handler via a 150m umbilical cable. And for use at Sellafield, the ROV required virtually no customisation.
It underwent a significant amount of testing — the last thing you want is an ROV sinking/melting into the middle of your hazmat pool. Once the ROV was cleared for use in the pools, it made short work of the survey, inspecting 60 per cent of the ponds. Some of the lower areas of the ponds were too crowded with waste for the ROV to access them, so it was outfitted with a camera boom for the 72mm wide spaces between the lower fuel skips.
The best part of the Seaker ROV is that it absorbs radiation so the handler doesn't have to. "After the initial launch into the pond, it enables the operators to withdraw to a low-radiation dose area of the building and thus reduce human dose." said Dave Skilbeck, head of the cleanup operations. "There is no alternative that is as safe as this method, which is evidenced by the absence of high-quality information on the pond conditions prior to this project."
"It can be deployed quickly, and it operates in a very efficient manner, surveying large sections of the pond in a short space of time," he continued. "The largest time savings come from the remote nature of the work, which means that risks to operators are correspondingly low." [Solid State Technology - ROVTech Systems - Nuclear Engineering - Sellafield Sites]