Exelon Corp.'s 1,136-megawatt Unit 2 at the Byron nuclear power plant in Illinois shut by late Monday soon after ramping up to 25 percent power earlier in the day, due to a turbine trip, the U.S. Nuclear Regulatory Commission said.
The plant had been shut down last week, after reporting a loss of offsite power a day earlier.
"The insulator, which was the cause of the loss of offsite power, is fixed. At this point, we're double-checking various systems and performing testing so we can bring the unit back online," a company spokeswoman said.
However, she could not say when the unit would return to service.