An innovative, Jamko-designed solution to an NRC reactor vessel examination requirement, first tried during U2R11 at Palo Verde Nuclear Generating Station, proved to be very successful. So much so, that the development team is submited for a Nuclear Energy Institute Top Industry Practice Award.
When the NRC required that PWR plants with bottom mounted instrumentation nozzles inspect them, Jamko knew it would be a challenge.
The mandated inspection requires a bare metal examination of the nozzles for signs of leaking every outage. Nearly all of them had a “spraylat” protective coating left from construction that would make the bare metal inspection difficult, and the area under the reactor was a very high radiation zone.
A seven member team comprised of engineers and technicians from Palo Verde and Jamko worked to develop a remotely controlled robot with a telescoping nozzle unit on top. This unit contained a camera and nozzle that fired carbon dioxide pellets that safely remove any residue from the reactor instrument nozzles.
Ed Fernandez, a Palo Verde senior engineer, ISI, and part of the project team, explained the operation. “The CO2 pellets removed the spraylat coating without any added radioactive waste or hazardous residues that have to be disposed. This produced a clean bare metal surface for remote visual inspections,” he said.Fernandez added, “This provides a baseline for future inspections to verify that no boric acid crystals are present on the nozzles, which could indicate a primary coolant leak.”
At the completion of the project in U2R11, the NRC was complimentary of the cleaning methods and inspection quality. The staff indicated that the dry ice media was “creative and innovative” and that the end result was above and beyond that of the minimum required.
“The Jamko robotic system should work on most PWR plants, which is why there is industry interest,” Fernandez added.