CORRECTION: A previous version of the story stated that Dominion was not planning to appeal the decision. Dominion is reviewing the decision and has not yet decided whether to appeal.

Waterford — For the second time in less than a year, the Nuclear Regulatory Commission has cited the Millstone Power Station for a violation that merits additional inspections and oversight.

The NRC announced Thursday that it has finalized its decision on a security violation found during an inspection in November. The finding was first announced in January, but the NRC had not categorized the severity of the finding until after a meeting in February with officials from Millstone owner Dominion Resources.

During that meeting, Dominion disagreed with the NRC’s assessment of the significance of the violation, according to a letter the NRC sent Thursday to David Heacock, president and chief nuclear officer of Dominion.

Despite Dominion’s objections, the NRC determined that the violation was significant enough to be “greater than green.” The NRC uses a four-tiered color coded system to categorize the severity of safety findings, with green being the lowest, followed by white, yellow and red. Because the violation relates to security, the NRC said it will not disclose the color code assigned to it, nor the nature of the violation.

The NRC said it will increase its oversight of Millstone, including assigning additional inspections of security systems and procedures. Three NRC resident inspectors are assigned to the plant on a day-to-day basis, and additional inspectors are brought in periodically to examine specific areas.

Millstone 3, one of the two operating reactors at the power station, is already under increased NRC scrutiny due to a white finding issued in August. The NRC found the plant had violated safety regulations pertaining to the operation of a backup pump that provides cooling water to the plant.

In addition, Millstone has been cited for several green violations over the past year, including two related to the pump and another related to security. In February, the NRC also found Millstone violated federal requirements in incidents leading up to the unplanned shutdown of both reactors last May.

In its letter, the NRC requires Dominion to respond to its determination, and states that it will decide whether to levy a financial penalty after that.

In a statement, NRC Region I Administrator Dan Dorman said that “it should be noted that the security of the plant is not in question” and that the inspectors made sure corrective actions were taken immediately.

Ken Holt, spokesman for Millstone, said Dominion is reviewing the Nuclear Regulatory Commission's decision and has not yet decided whether to appeal.

“The issue was promptly addressed when it was identified, and corrected before the inspectors left the site,” he said.

He declined to comment further.

Bill Sheehan, chairman of the Nuclear Energy Advisory Council, a citizens group that monitors the plant, said he anticipates the violations will be discussed during his group’s annual meeting with the NRC, which is scheduled for 6 p.m. April 14 at town hall.

“This certainly adds interest" to the meeting, he said.

Sheehan said he has met twice with Millstone Power Station site Vice President John Daugherty, who took over the post in December, about issues at the plant. Sheehan said there has been a “significant turnover in senior management” at the plant that he believes indicates the issues are being taken seriously.

“It seems like he’s got a good handle on what’s going on,” Sheehan said. “Time will tell.”

j.benson@theday.com

Twitter: @BensonJudy