By Scott DiSavino
(Reuters) - Power company Exelon Corp said Wednesday it ended an alert at the Oyster Creek nuclear power plant in New Jersey after high water from Hurricane Sandy returned to normal levels.
Oyster Creek, the nation's oldest operating reactor, declared the rare "alert" Monday night after water levels at the plant rose more than 6.5 feet above normal, potentially affecting the "water intake structure" that pumps cooling water through the plant.
The pumps were not essential to keep the reactor cool since the plant has been shut for planned refueling since October 22.
Exelon, however, was concerned that if the water rose more than 7 feet it could submerge the service water pump motor used to cool the water in the spent fuel pool, potentially forcing the company to use emergency water supplies from the in-house fire suppression system to keep the used uranium fuel rods in the pool from overheating, the U.S. Nuclear Regulatory Commission (NRC) said Monday night.
Exelon said there was no danger to public health or safety. The plant has numerous means of keeping the water in the spent fuel pool cool, including the use of a portable pump moved to the water intake structure and the fire suppression system.
Exelon said in a statement on Wednesday the winds and heavy rains generated tides 6.8 feet above mean sea level at the 43-year-old plant's water intake. But they were never high enough to top the intake canal banks or affect operation of the plant's equipment.
After water levels returned to normal and offsite power was restored, Exelon said the plant exited the alert early Wednesday morning.
The Oyster Creek alert was only the third time this year that the second-lowest of the NRC's four emergency action levels was triggered.
The incident at the relatively small 636-megawatt Oyster Creek plant, which is about 60 miles east of Philadelphia on the New Jersey Coast, came as Sandy made landfall as the largest Atlantic storm ever, bringing up to 90 mile per hour winds and 13-foot storm surges in the biggest test of the industry's emergency preparedness since the Fukushima disaster in Japan a year and a half ago.
INDUSTRY PASSES TEST
Despite the alert -- which is a serious but not catastrophic event that signals a "potential substantial degradation in the level of safety" -- the U.S. nuclear industry is broadly seen as having passed the test. About a dozen alerts have been issued in the past four years, according to NRC press releases.
The NRC said Wednesday morning it was beginning to return to normal inspection coverage for the nuclear power plants in the U.S. Northeast.
In addition to the event at Oyster Creek, three reactors were shut during the storm. They were Entergy Corp's Indian Point 3 in New York, Public Service Enterprise Group Inc's Salem 1 in New Jersey and Constellation Energy Nuclear Group's Nine Mile Point 1 in New York. The NRC said all safety systems responded as designed at the plants that shut.
The NRC also said three other plants reduced power due to the storm. They were Dominion Resources Inc's Millstone 3 in Connecticut, Entergy's Vermont Yankee in Vermont and Exelon's Limerick in Pennsylvania. By early Wednesday, the reactors had begun to return to full service.
(Reporting by Scott DiSavino; Editing by Gerald E. McCormick and Dan Grebler)