WASHINGTON (AP) -- Three commercial nuclear power reactors remained shut Tuesday in the aftermath of superstorm Sandy while another plant — the nation's oldest — was still on alert.
Nine Mile Point Unit 1 reactor on Lake Ontario, northwest of Syracuse, N.Y., shut down automatically around 9 p.m. Monday when an electrical fault occurred on a power line used to send electricity from the plant to the grid, according to the U.S. Nuclear Regulatory Commission.
The second reactor at the site lost one of its incoming power lines, causing a backup generator to start. That reactor was continuing to produce electricity.
Another nuclear reactor, Indian Point's Unit 3, about 25 miles north of New York City, was shut down Monday because of external electrical grid issues, said Entergy Corp., which operates the plant. The company said there was no risk to employees or the public, and the plant was not at risk due to water levels from the adjacent Hudson River, which reached 9 feet 8 inches before beginning to subside. Another unit at the plant continued to operate at full power.
At the Salem plant in Hancocks Bridge, N.J., near the Delaware River, the Unit 1 reactor was shut down early Tuesday because four of its six circulating water pumps were no longer available, according to PSEG Nuclear, which operates the complex. The pumps are used to condense steam on the non-nuclear side of the plant.
Another Salem unit has been offline since Oct. 14 for refueling, but the nearby Hope Creek plant remains at full power. Together, the Salem and Hope Creek plants produce enough power for about three million homes per day.
Since the condensers are unavailable at the Unit 1 reactor at the Salem plant, steam was being vented into the atmosphere. NRC spokesman Scott Burnell stressed that the steam being vented does not come into contact with radioactivity deep inside the nuclear generator, and does not pose a health threat.
The oldest U.S. nuclear power plant, New Jersey's Oyster Creek, was already out of service for scheduled refueling. But high water levels at the facility, which sits along Barnegat Bay, prompted safety officials to declare an "unusual event" around 7 p.m. About two hours later, the situation was upgraded to an "alert," the second-lowest in a four-tiered warning system.
The NRC, which oversees plant safety, said conditions were safe at Nine Mile Point, Indian Point, Salem, Oyster Creek and all other U.S. nuclear plants.
A rising tide, the direction of the wind and the storm's surge combined to raise water levels in Oyster Creek's intake structure, the NRC said. The agency said that water levels are expected to recede within hours and that the plant, which went online in 1969 and is set to close in 2019, is watertight and capable of withstanding hurricane-force winds.
The plant's owner, Exelon Corp., said power was also disrupted in the station's switchyard, but backup diesel generators were providing stable power, with more than two weeks of fuel on hand.
In other parts of the East Coast, nuclear plants were weathering the storm without incident.
Inspectors from the NRC, whose own headquarters in Washington, D.C., and Northeast regional office in King of Prussia, Pa., were closed for the storm, were manning all plants around the clock. The agency dispatched extra inspectors or placed them on standby in five states, equipped with satellite phones to ensure uninterrupted contact.
Nuclear power plants are built to withstand hurricanes, airplane collisions and other major disasters, but safety procedures call for plants to be shut down when hurricane-force winds are present, or if water levels nearby exceed certain flood limits.
"Our top concern is ensuring that the plants are in a safe condition, that they are following their severe weather procedures," said the NRC's Diane Screnci.
Some 60 million people in 13 states plus the District of Columbia get their power from PJM, the largest regional power grid in the U.S. Contingency plans call for power to be brought in from other areas to replace power lost if a nuclear plant reduces output or goes offline.
"It's done instantaneously," said Paula DuPont-Kidd, a spokeswoman for the grid. "Even if multiple plants go offline at the same time, we'd have to see how adjustments would be made, but for the most part we plan for that scenario."
In August 2011, multiple nuclear plants shut down due to Hurricane Irene, with others reducing power.
Henry reported from Atlanta. Reach Josh Lederman on Twitter at http://twitter.com/joshledermanAP