The federal government will provide "enhanced oversight" for nine different nuclear power plants in the path of Hurricane Sandy, including Three Mile Island and New York's Indian Point.
The Nuclear Regulatory Commission said each plant is overseen by at least two NRC resident inspectors and the agency has sent additional inspectors to some of those sites in order to ensure 24-hour coverage before, during and after the storm.
The NRC is also monitoring the plants from its Incident Response Center in Pennsylvania and its Operations Center at its headquarters in Maryland.
In addition to Indian Point, which is north of New York City, and Three Mile Island, the Pennsylvania plant famous for a partial meltdown in 1979, the facilities receiving the "enhanced oversight" include the Salem, Hope Creek and Oyster Creek nuclear plants in southern New Jersey; Peach Bottom and Susquehanna in Pennsylvania, Calvert Cliffs in Maryland and Millstone in Connecticut.
"Nuclear power plant procedures require that the facilities be shut down prior to any projected hurricane-force winds on-site," said the NRC.
The agency noted that the plants have emergency diesel generators are available if off-site power is lost during the storm.
"Also, all plants have flood protection above the predicted storm surge," said the NRC, "and key components and systems are housed in watertight buildings capable of withstanding hurricane-force winds and flooding."
The Oyster Creek and Salem plants are close to where Sandy made landfall in southern New Jersey Monday evening, but their reactors had already been shut down for maintenance, as has the Susquehanna plant in Pennsylvania.
Operators declared an alert at Oyster Creek Monday evening after the center of Sandy came ashore, "due to water exceeding certain high water level criteria in the plant's water intake structure."
The alert is "the second lowest of four action levels," according to the NRC.
"Water level is rising in the intake structure due to a combination of a rising tide, wind direction and storm surge," the NRC said. "It is anticipated water levels will begin to abate within the next several hours."
Exelon Corporation, the owner of the plants, said in a statement that there was "no threat to the public health or safety" from the situation.
The plant also lost power, which is critical to keep spent fuel rods from overheating, but "the station's two backup diesel generators activated immediately," and it has two weeks of diesel fuel on site, Exelon said.
Jim Steets, the communications director for Entergy, which runs Indian Point, said that while they could experience flooding "greater than historically experienced," the plant is "still positioned well above that." Steets said that if conditions change and the storm takes a more threatening turn "such that we need to shut down the plant, we'll do that."
Japan's Fukushima nuclear power plant released radioactivity in March 2011 after an earthquake and tsunami there were followed by a meltdown.