Officials at the Oyster Creek Nuclear Generating Station in New Jersey had manually stopped its reactor without incident April 25. Crews repaired the transformer and modified its power supply.
Plant spokesman David Benson says the outage was extended so crews could further prepare the plant for summer operations.
The crews also found and stopped two small leaks in underground pipes believed to be the source of a weak radioactive substance recently detected on the plant's property in Lacey Township, about 60 miles east of Philadelphia and 75 miles south of New York City. They replaced the pipes.
Oyster Creek opened in December 1969. It generates enough electricity to power 600,000 homes a year.