SENECA - An emergency was declared at a nuclear power plant early Monday when operators could not confirm the position of three control rods after the reactor shut down, officials said.
There were no injuries, no radiological releases and no equipment damage at the LaSalle Generating Station in rural Brookfield Township in LaSalle County, according to Exelon Nuclear officials.
The plant, which is owned by Chicago-based Exelon Corp., was scheduled to shut down early Monday for a refueling outage.
According to the Illinois Emergency Management Agency, the reactor did not shut down properly.
Company officials said instruments showed three of the 185 control rods failed to insert fully into the reactor core and operators declared a "site area emergency" at 12:28 a.m. That is the second-highest of the four emergency categories in the U.S. Nuclear Regulatory Commission's emergency response system.
The emergency was over about four hours later, Exelon Nuclear officials said.
Operators reset the control rod position indication system and then found only one rod was out of position, company officials said.
Exelon Nuclear officials are trying to determine why the control rod indicators originally showed the rods weren't inserted properly. The NRC said it also will investigate the shutdown and the IEMA is monitoring the station.
Preliminary information showed a malfunction of the plant's turbine control system caused the automatic reactor shutdown, according to the NRC.
The nature of the incident - a control rod not going into the reactor - triggered the site area emergency, but "it never really progressed into being a danger," said IEMA spokeswoman Patti Thompson.
The plant, which is near Seneca, is about 55 miles southwest of Chicago.