CHICAGO (AP) ― The U.S. Nuclear Regulatory Commission is launching a special inspection into how some equipment responded to a power failure at a nuclear reactor in the midwestern state of Illinois.

NRC spokeswoman Viktoria Mitlyng says some water pumps at the Byron Generating Station switched off when the Unit 2 reactor lost power Monday, then came back on without being manually reset.

She says the pumps are designed to switch off after a set amount of time if there is an undervoltage, but normally must be reset. She says there was no danger because the plant about 153 kilometers northwest of Chicago has multiple backup pumps, but the NRC wants all pumps to perform properly.

Exelon Energy officials say they’ve replaced a faulty electricity insulator at the plant that was responsible for the outage.