Waterford — An 8-month-long investigation by the Nuclear Regulatory Commission has turned up one or more “apparent violations” related to undisclosed security matters at Millstone Power Station.

In a July 20 letter to Millstone’s owner, Dominion Energy Inc., the NRC’s director of reactor safety says that evidence gathered during an investigation that began Sept. 2, 2016, and ended April 27, 2017, turned up “one or more apparent violations that are being considered for escalated enforcement action, including a Civil Penalty...”

Details of the investigation and the possible violations involve security matters and are considered sensitive information and therefore not disclosed publicly, according to the NRC.

The NRC has requested that Dominion provide a written response within 30 days on corrective actions it has taken or plans to implement to address the apparent violation or violations. Dominion also may choose a predecisional enforcement conference with the NRC to discuss the issue or an alternative dispute resolution mediation session.

Once the NRC has evaluated any information provided by Dominion, it will issue its enforcement decision, according to NRC spokesman Neil Sheehan.

Dominion spokesman Kenneth Holt said the company already has corrected the issues identified in the report.

"We take security of our nuclear stations very seriously," Holt said in a statement. "We will work closely with the NRC to respond to these apparent violations."