New Jersey’s Oyster Creek Nuclear Generating Station remains under an official Alert, a day-and-a-half after the US Nuclear Regulatory Commission declared the emergency classification due to flooding triggered by Hurricane Sandy. An Alert is the second category on the NRC’s four-point emergency scale. Neil Sheehan, a spokesman for the federal regulator, said that floodwaters around the plant’s water intake structure had receded to 5.7 feet at 2:15 PM EDT Tuesday, down from a high of 7.4 feet reached just after midnight.
Water above 6.5 to 7 feet was expected to compromise Oyster Creek’s capacity to cool its reactor and spent fuel pool, according to the NRC. An “Unusual Event,” the first level of emergency classification, was declared Monday afternoon when floodwaters climbed to 4.7 feet.
Though an emergency pump was brought in when water rose above 6.5 feet late Monday, the NRC and plant owner Exelon have been vague about whether it was needed. As of this writing, it is still not clear if Oyster Creek’s heat transfer system is functioning as designed.
As flooding continued and water intake pumps were threatened, plant operators also floated the idea that water levels in the spent fuel pool could be maintained with fire hoses. Outside observers, such as nuclear consultant Arnie Gundersen, suspected Oyster Creek might have accomplished this by repurposing its fire suppression system (and Reuters later reported the same), though, again, neither Exelon nor regulators have given details.
Whether the original intake system or some sort of contingency is being used, it appears the pumps are being powered by backup diesel generators. Oyster Creek, like the vast majority of southern New Jersey, lost grid power as Sandy moved inland Monday night. In the even of a site blackout, backup generators are required to provide power to cooling systems for the reactor–there is no such mandate, however, for spent fuel pools. Power for pool cooling is expected to come either from the grid or the electricity generated by the plant’s own turbines.
As the NRC likes to remind anyone who will listen, Oyster Creek’s reactor was offline for fueling and maintenance. What regulators don’t add, however, is that the reactor still needs cooling for residual decay heat, and that the fuel pool likely contains more fuel and hotter fuel as a result of this procedure, which means it is even more at risk for overheating. And, perhaps most notably, with the reactor shutdown, it is not producing the electricity that could be used to keep water circulating through the spent fuel pool.