This story was updated March 19, 2018, at 11:59 p.m. with more information.
Two contract workers were burned from an arc flash while working near the cooling towers of a Tennessee Valley Authority nuclear plant over the weekend.
The workers employed by Day & Zimmerman at the Sequoyah Nuclear Power Plant near Soddy-Daisywere hospitalized Friday night for first- and second-degree burns.
The Nuclear Regulatory Commission said in an incident report that both workers were transported to a hospital for treatment. Neither worker was shocked nor contaminated by any radiation from the 6.9 kilovolt electrical bus they were working on during the accident.
"The cause of the arc flash is not understood at this time; an accident investigation has been initiated by TVA," the NRC said in its report on the incident.
TVA spokeswoman Malinda Hunter said Monday that TVA is investigating the incident, which occurred in the non-nuclear part of the plant and did not jeopardize operations of either of the power generating reactors.
"We have suspended similar work activities across the fleet until we have a full understanding of the cause," Hunter said. "Our thoughts are with the injured workers and their families. TVA's primary focus is on the safety of employees, contractors and the public. As such we are investigating the incident to prevent recurrence."
Neither TVA nor its contractor, Day & Zimmerman, released the identity or any specific information about the injuries suffered by the two workers.
An arc flash is the light and heat produced as part of an arc fault — essentially an electrical discharge. Unlike a shock, a person does not have to touch an electrical conductor. The heat from an electrical arc can result in burn injuries.
Both Sequoyah reactors remain at full power since the incident occurred away from the power generating side of the plant "and there are no public or nuclear safety concerns," Hunter said.
TVA also said Monday that its oldest nuclear reactor shut down midday Sunday due to a turbine control problem.
The Unit 1 reactor at the Browns Ferry plant near Athens, Ala., was automatically taken off line shortly after noon, EDT, Sunday following a problem detected with the main turbine control logic.
"Safety systems responded as designed and operators responded as trained using plant procedures to safely place the unit in a shutdown condition and the plant staff is investigating the cause of the shutdown," Hunter said.
The trip resulted from a problem on the non-nuclear part of Browns Ferry and Hunter said there were no public safety concerns from the incident.
Browns Ferry's Unit 2 is generating electricity at 100 percent power while Unit 3 is shut down for a scheduled refueling and maintenance outage.
Contact Dave Flessner at firstname.lastname@example.org or at 757-6340.