Security guards at an Exelon Corp. (NYSE: EXC) nuclear power plant in Pennsylvania were found sleeping on the job, according to media reports. The Chicago-based utility company said it dropped Wackenhut as security contractor for its Peach Bottom plant and is reviewing the security firm's work at other company reactors, according to The Philadelphia Inquirer,

This couldn't have come at a worst time for the nuclear power industry whose reputation has improved over the past few years as a lesser evil to global warming-causing coal-fired power plants. NRG Energy Inc. (NYSE: NRG) is even proposing to build its first nuclear power plant in almost 30 years. But every time the nuclear power industry takes one step forward, it takes two steps back.

In Exelon's case, the embarrassment was captured on video by another security guard over several months and sent to New York television station WCBS-TV, The Inquirer said. The incident, involving fewer than 10 workers, is investigated by the company and the Nuclear Regulatory Commission, the paper said.

Exelon, of course, was mortified by the video.

"This is not acceptable and we will not tolerate it," said Exelon Generation Chief Operating Officer Chris Crane in a press release. "I want to be clear that nothing has happened at Peach Bottom that represents a security or safety threat to the public. We are dealing with unacceptable behavior, and we will fix it."

What's scary is that it's happened before. Workers were caught napping at the control room of the same nuclear power plant in the late 1980s, according to the New York Times.

Those that don't learn from history are doomed to repeat it.