5 Ways ROVs Optimize Nuclear and Hydropower Site Inspections
Rachel Doornekamp | July 10, 2020
The regular inspection of submerged infrastructure in the energy sector is incredibly important. With consistent inspections operators are able to stay on top of maintenance and repairs and catch minor issues before they become catastrophic problems.
Submersible remotely operated vehicles or ROVs offer energy sector teams an alternative or complement to sending divers underwater to do both emergency and routine inspection work on structures like cooling towers, intakes, penstocks and trash racks.
The use of a Deep Trekker ROV allows operators to maximize their inspections to get the best results while minimizing time and cost.
Perhaps the most important way in which ROVs maximize underwater inspections is the increase in safety. By using an ROV human divers are kept safe and out of harm’s way.
Che Swearengen, a Commercial Inspection and Maintenance Diver with Ontario Power Generation shared with the Deep Trekker team a time when the use of an ROV allowed him to keep his team safe during the inspection of an injection water service tank at one of their Nuclear power stations.
“The benefits of using the ROV versus using an actual diver in the water are numerous,” explained Swearengen. “Number one is the radiological uptake. So there’s (a radiological) dose involved with these tanks as there are some nuclear particles in there causing radiation, but with the ROV we’re not too concerned about it getting contaminated. You can decontaminate the ROV or literally purchase another one. The other reason why we decided to use the ROV in this tank is that there was a valve that was on the bottom, it was passing water and we had no way to shut it off so to introduce a diver into that situation causes a hazard that we weren’t really looking to deal with.”
Following the inspection, the decontamination process took place, as the ROV had been in a radioactive tank. “It (the decontamination) was very very minimal compared to if it had been a diver.”
“In this instance, costs and safety were the two driving factors. With regards to safety it was the human factor, there was no radiation and no work protection involved for shutting down the systems...This was a great tool to get in there and do inspection while maintaining cost and safety for everybody.”
In addition to inspecting in lieu of divers, ROVs can also maximize safety by assisting divers. The vehicle can survey dive areas prior to sending down a human being, checking for any potential safety risks and determining the lay of the land. Using the robot for pre-dive inspections allows teams to confirm dive conditions reliably and effectively.
By piloting an ROV to monitor divers, those topside can ensure that divers are safe and following safety protocols. Real-time video observation allows any issues to be caught promptly with immediate emergency assistance if necessary.
The use of an ROV greatly expedites inspection processes. Deep Trekker vehicles are battery operated and easily transportable, meaning that teams do not have to lug around generators or find ways to get access for vehicles. The portability paired with ease of operation allows for quick deployment times.
Furthermore, operations do not have to be shut down before an ROV enters the water and then started up again following inspection. Swearengen noted how efficient the ROV was during inspection noting, “essentially we did this (inspection) in a hold-op, we informed the station owners that we were going to be doing the inspection and they did not operate any pumps while we were in there. It saves quite a bit of time from trying to lock them all out and going through a lockout, tagout procedure.”
Swearengen reflected on the injection water service tank inspection and recalled that by using the ROV, he and his team were able to conduct a thorough inspection of the tank and leaking valve in four hours. The inspection did not require complete shut down and decontamination of the ROV following the procedure was quick, meaning that set up and take down time is minimized.
The use of an ROV drastically reduces the costs involved in conducting inspections. Thomas Griner, a Maintenance Manager at a nuclear power facility in the Midwestern United States commented on his use of an ROV saying, “when everything was said and done, all three forebay inspections were completed 100% satisfactory, were done safer, faster and with the innovation of using the REVOLUTION ROV vs divers has the ability to save my company millions for the investment of a few thousand dollars into an ROV.”
Swearengen shared how the use of an ROV allowed his team to optimize their budget during a runner inspection at Chats Falls. As with any hydroelectric facility, inspections of submerged infrastructure at Chats Falls are required to maintain safety and regulatory standards. Swearengen noted that typically these routine inspections are done by divers who look at structures such as turbines, blades and throat rings to examine for cavitation, missing metal, etc. In the past, these inspections required a 6 person dive team and expensive and time consuming lockout work protection procedures.
“We’ve adapted (the inspections) to use ROVs. It’s now a two-person crew, the work protection isn’t involved, as it's a piece of equipment and not an actual human, and we can get some pretty good results with the ROV - this is now pretty much the way we do all of our runner inspections.”
Using the ROV for inspection means that no work protection is required and a smaller crew can be used, significantly reducing both the time and money required.
The ROV saved significant amounts of money in this mission as it was unnecessary to shut the unit down, dewatering and unfuel the unit with the vehicle entering the water in lieu of human divers.
Jon Thomas of the Eugene Water and Electric Board shared how a Deep Trekker ROV has allowed his team to save significant amounts of money by using the vehicle in lieu of divers.“I could come up with at least 5 times so far where we would have scheduled divers to do what the ROV did.”
Thomas also pointed to occasions where the ROV was being used to evaluate the accumulation of debris on the intake trash racks allowing the Utility to optimize the use of hired divers when needed.
The durability, flexibility and versatility of Deep Trekker ROVs allow operators to conduct a wide variety of tasks to make the most of their time underwater.
Swearengen shared a time when he and his team were able to take advantage of the versatility of the vehicle while conducting an inspection on a leak. In addition to locating the leak, the team was able to seal the leakage using the robot. “We actually adapted the ROV to deliver a sealant. So while we were on top of the reactor duct with the ROV we were able to apply a sealant and seal the leakage from the inside.”
Thomas also noted how the flexibility and versatility of Deep Trekker ROVs have benefited him and his team. “Many of the events in which we’ve used the ROV have been unscheduled,” shared Thomas. “The flexibility of having this tool available to us as the need arises is something we have found very convenient.”
Thomas shared a specific example during recent repair work at the Smith Reservoir intake structure as the team had been experiencing difficulty with lowering the gate into position. The rail guide system used to move the gate was jolting and not aligned, making moving the gate incredibly difficult. From topside the team was unable to see what was going on underwater. Using the ROV, the team was able to determine where the system was running into trouble and how they could fix it to allow the gate to open and close. Thomas noted here that, “without the camera on the vehicle, this would not have been possible.”
The flexibility and versatility of Deep Trekker ROVs can be taken advantage of to optimize submerged inspections.
Reach Difficult or Dangerous Areas
An ROV provides pilots with a safe and reliable way to inspect difficult or confined areas to inspect the entirety of submerged structures.
Swearengen shared a time when the ROV was used to inspect a hazardous area. There was a known leak on a calandria however the exact location could not be determined. Housing all of the fuel bundles, the calandria is surrounded by heavy water.
The OPG team made the decision to use an ROV to locate the leak. “The driving factor here was that there was no access to actually get in and do the inspection. There was also fuel still inside the reactor core - which is the calandria - so the radiation dosage was extremely high making it unreachable for humans. We were able to actually access this with the ROV and go down around the core with the fuel bundles and get to the bottom of the tank and continue with the inspection to find the leakage area.”
After use in the calandria, the ROV had to be decontaminated before any further use. “Over the course of a couple of months we were able to decontaminate the ROV and put it back into service.” The ability to conveniently and thoroughly decontaminate the vehicle lends itself well to accessing difficult and dangerous areas.
You can learn more by reading Using an ROV to Inspect Confined Spaces.
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