Nuclear industry ‘eyeballs’
Right from the start, ROVs have been designed to get into places where it’s impractical or impossible to place a human being. And no man-made environment needs them more than a nuclear reactor.
Steve Phelps of Rovtech Solutions told MJ that remotely operated vessels were first used in 1984 to survey the damage from the - then Windscale - original 1950s pile fire and radioactive leak which led to its eventual closure.
It set a precedent, he explained. After this ROVs became Sellafield’s “underwater eyeballs” that allowed a look around several storage ponds.
Rovtech has supplied nine ROVs for Sellafield’s decommissioning process: these have, over the last three or four years, helped to move and reclassify several tonnes of radioactive material. However, it became obvious quite early on “that usability is a lot more important than high end tech” he said.
“One issue is that getting up close to highly radioactive material has a temporary effect on electronics, for example, cameras stop working.” The only real answer to this was to reserve most of the complexity for the above-water controls. There’s also the matter of an extremely corrosive 11.4ph environment and the need to decontaminate by jet washer, so the ROV’s construction needs to be as tough and simple as possible, with a reliance on stainless steel and polycarbonates.
Despite this, the ROVs still need to be flexible: “The Adaptable Seaker allows you to drop in different tooling options, the sludge sampler takes samples of radiation levels, the jet pump allows you remove or redistribute sludge to expose specific areas, then the manipulator can pick up the fuel rods themselves which can be up to a metre long.”
It’s probably the fact that the operating technicians still need to wear three pairs of gloves for maintenance, even after the decontamination process that makes one of the biggest differences. There’s a plug and play philosophy on cameras, thrusters and lights that enables an easy turnaround explained Mr Phelps, “all the items have to be quick release; you can’t have anything that requires a lot of dexterity”.
But although this is a somewhat unusual development pathway, there are crossovers that link into other areas: “Sellafield has some very small entrances, less than 900mm wide, so Rovtech is now developing a smaller ROV, it’s about a fifth of the size of the Seaker which can be picked up in one hand.”
This, he said, “would also be ideal for surveying in turbid conditions or where there’s restricted access such as black water areas or canals; I’d be very excited to see it used for environmental sampling”.
By Stevie Knight
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