In the "So You Don't Run Out of Things to Worry About" Department...

A pipe bomb turned up in the truck of a worker at a nuclear power plant...

A nuclear power plant in Arizona was locked down Friday morning after security guards discovered a pipe bomb in a contract worker's truck, authorities said.

Plant operator Arizona Public Service called the discovery an "unusual event" and sealed off the site, with no traffic entering or leaving the grounds.

A bomb squad from the Maricopa County Sheriff's Department declared the pipe bomb a "credible explosive device."

The contract worker was entering Palo Verde Nuclear Generating Station at a checkpoint for a standard security inspection at the beginning of the day shift. Guards armed with automatic rifles check identification and search under the hoods of all vehicles entering the plant.

There was no danger to the plant, officials said.

"This is not a threat to the public," said Jim McDonald, a spokesman for Arizona Public Service Co. "If it had the potential to be, the security guards stopped it."