The US Nuclear Regulatory Commission (NRC) is proposing a $17,500 (£11,837) penalty against the owner of a decommissioned nuclear power plant.
It said the fine is for a “security-related violation” following routine inspections.
Dominion Resources shut down the 556MW Kewaunee nuclear power station in Wisconsin in May 2013.
The NRC had conducted inspections between June and December last year looking into the security requirements and reviewed plant documents.
“Once the issue was identified the plant took corrective actions to address the security violations before the NRC inspectors left the site. To emphasize the importance of security awareness as well as the need for prompt identification of a violation the NRC has proposed a $17,500 civil penalty,” it said in a statement.