The NRC says the leak occurred Sunday morning in a turbine building at the Connecticut plant, and workers responded by manually shutting down the reactor.
Neil Sheehan, a spokesman for the Nuclear Regulatory Commission, tells The Day of New London that leak occurred after a sealant plug for hydrogen in the main generator came lose. He says workers successfully vented out the hydrogen.
The reactor recently returned to operation after a scheduled outage for refueling.
The NRC says it is trying to determine whether the leak may have been related to work done during that refueling.