An aerial view of the Calvert Cliffs Nuclear Power Plant in Southern Maryland.
An aerial view of the Calvert Cliffs Nuclear Power Plant in Southern Maryland. (Baltimore Sun photo by Kim Hairston)

The Calvert Cliffs nuclear power plant will face increased regulatory oversight after an August finding that a miscalculation on the operators' part could have led to an unnecessary emergency response to an insignificant radiation leak.

The Nuclear Regulatory Commission on Monday released the final results of its Aug. 8 inspection of the twin-reactor facility in Lusby, 70 miles south of Baltimore, which reported that Exelon Generation Co. had made a mistake of "low to moderate" safety significance.


Radiation detectors replaced a year ago on the main steam lines for the plant's Unit 2 were set to trigger an alarm at a radiation level 100 times lower than would be deemed a safety threat, the NRC said. Plant operators discovered and corrected the error four months later, but the NRC said it was concerned the mistake may have prompted an overreaction to low readings, leading to an unwarranted emergency response.

In a formal response last month to the inspection's findings, Excelon acknowledged the lapse but argued that prematurely reacting to a low-level leak would be less significant than missing a warning and not evacuating the area quickly enough, the NRC said. The agency said the response contained "no new information" and it did not alter its decision.

The facility likely will undergo a special inspection to ensure whatever led to the mistake has been corrected, plant spokesman Kory Raftery has said.

"We identified and promptly corrected an overly conservative radiation monitor setting and we remain 100 percent ready to protect the public in the unlikely event of an emergency," Raftery said in a statement Tuesday. "Our comprehensive corrective action program ensures that we identify, correct and share issues, including those of low safety significance."

Baltimore Sun reporter Tim Wheeler contributed to this article.