Columbus, Neb. – Shortly after 7 p.m. Saturday evening, October 11, while shut down for a planned refueling outage, specialized contract technicians at Nebraska Public Power District’s Cooper Nuclear Station in Brownville were performing a planned, underwater control blade “shuffle” where certain blades are replaced and others moved to new locations in the reactor core. One of the control rod blades fell from the lifting tool and came to rest atop the reactor vessel top guide in a section that contained no fuel.
Personnel responded appropriately, suspending all activities in the area to inspect and evaluate the fuel. NPPD is working with the contractor on an investigation as to the cause of the incident. The control blade was successfully and safely removed and placed in the proper location in the spent fuel pool early Monday morning. There was no increase in radiation exposure to workers, and at no time was the public at risk from the incident.
As part of its regular protocols, Cooper’s leadership informed the Nuclear Regulatory Commission resident inspectors onsite and confirmed there were no indications of any adverse impact to the station’s fuel or radiation levels.
“This refueling outage is the 28th one we have performed at Cooper in 40 years,” said NPPD President and CEO Pat Pope. “Every maintenance outage can be accompanied by challenges. Our Cooper team remains focused on ensuring a safe work environment for personnel, adherence to procedures, proper job briefs and work oversight, as well as a commitment to completing the work in a manner that protects our employees and the public.”
Cooper’s control rod blades, approximately 14 feet in length, are x-shaped elements that occupy alternate spaces and separate the fuel assemblies throughout the core and are positioned axially within the core to control reactivity as part of the primary power generation system. The equipment plays a central role in plant safety by providing the principal means of quickly and safely shutting down the reactor during online operation. During refueling and maintenance outages, the reactor is shut down, which allows for these components to be removed and replaced.
This year’s refueling and maintenance outage utilizes a team of employees and contractors totaling 1,600 people expected to complete close to 4,500 work activities, including the replacement of approximately one-third of the fuel assemblies in the reactor core with new fuel rods to operate the plant for another two years.