Ameren shuts down nuclear plant, investigates vibration

ST. LOUIS -- Ameren Corp. shut down its Callaway nuclear plant early Friday morning after unusually high vibrations were detected in the facility's power turbines.

The episode did not pose a danger to the public and was not an emergency, according to Ameren and the U.S. Nuclear Regulatory Commission, which regulates the plant.

The nuclear reactor remained closed late Friday morning as Ameren investigated the cause of the vibration.

St. Louis-based Ameren runs dozens of power plants in Missouri and Illinois to provide electricity to 2.4 million customers. State and federal regulatory agencies are investigating safety procedures within the company after its Taum Sauk reservoir collapsed last year.

NRC spokesman Jan Strasma said Ameren's safety procedures worked smoothly Friday morning. Strasma said the nuclear reactor itself was never in danger -- only the separate machinery in the plant that generates electricity.

Ameren spokesman Mike Cleary said employees at the mid-Missouri nuclear plant were conducting repairs Thursday night. They reduced power at the plant to 45 percent so they could replace instruments there, he said.

As power was lowered, an alarm went off indicating vibrations in the turbines. They were manually shut down, he said.

Minutes later, water levels built up in a steam generator, so employees manually shut down the nuclear reactor itself, according to NRC's report of the incident.

"It's an operating problem that happens in power plants and it's not an emergency," Cleary said.

At the Callaway plant, electricity generation starts in the reactor. Nuclear reactions there heat up rods, which are then cooled by flowing water. Steam from the water is funneled into the power turbines, which spin and make electricity.