When engineers at Harris Nuclear Plant recently developed plans to make repairs to a small flaw in a nozzle in the top of the plant’s reactor vessel head, they used a high-tech robot to reduce the risk of human error and to ensure precise, consistent, high-quality results.
Nuclear plants across the world use high-tech robots for maintenance and to conduct examinations of highly specialized nuclear equipment. Robots also perform inspections and make repairs on equipment in remote locations, providing access to difficult to reach areas without risk to worker safety.
On May 15, operators at the plant removed the unit from service for maintenance to repair the imperfection, which was noticed during a re-evaluation of inspection data from the plant’s last refueling outage.
Repairs like the one at Harris are well understood in the industry and have been completed many times across the country. The reactor vessel and head are similar to a cup with a lid. The cup represents the reactor; the lid represents the reactor head, and the straw represents the nozzle.
The flaw would be like a crimp in the straw, it still works, but repair it and you don’t have to worry about future issues. There was no leakage from the reactor vessel and never any risk to the health and safety of plant neighbors or employees.
With the reactor vessel head in a stand, a remote controlled robot was placed underneath the head to repair the small, quarter-inch flaw in the nozzle. The use of the advanced robot allowed plant employees to safely repair a welded area around the nozzle, without workers having to physically stand underneath the more than 355,000 pound vessel head.
The maintenance was completed in the expected time frame and the plant safely returned to service, with no negative effect on power supply to customers.
The continued safe operation of all of our power plants remains Duke’s number one priority. Harris had been safely operating for 342 days since its last refueling outage before going off line.