The agency says the fine is for a security-related violation stemming from routine inspections.
Dominion Resources Inc. shut down the 556 MW plant east of Green Bay in May 2013. The NRC conducted the inspections between June and December of last year. Agency inspectors looked at the security requirements for the permanently shut-down plant, conducted on-site inspections and reviewed plant documents.
The agency says once the issue was identified, the plant took corrective action before the inspectors left.
In a statement, Dominion says the company misunderstood how to implement security changes for a shutdown reactor. Dominion says it accepts the NRC decision and will pay the penalty.