As Hurricane Sandy reached the height of its fury on Monday night, October 29, the Oyster creek nuclear plant in southern New Jersey went on “alert” – the third-highest of four levels of emergency action for nuclear generating stations in the United States.

The oldest operating nuclear plant in the country, Oyster Creek is about 40 miles north of Atlantic City, just a mile from Barnegat Bay, an inlet off the Atlantic Ocean.  It has been plagued for years by environmental protests and lawsuits, mostly relating to the hot water it discharges into the bay.  It’s the same design as the ill-fated reactors at Fukushima-Daiichi in Japan that were inundated in the March 2011 earthquake and tsunami.  Oyster Creek is scheduled to be shut down in 2019.

In anticipation of the storm, emergency crews from the Nuclear Regulatory Commission were dispatched to Oyster Creek, along with eight other nuclear plants on the Eastern Seaboard.  Officials with the federal government and with Exelon, the nation’s largest producer of nuclear power and operator of Oyster Creek, were less concerned about damage to the reactor itself than about keeping the spent fuel rods, stored in a large pool onsite, from overheating.  Intake structures and pumps take water from the creek and pump it through the plant to cool off both the reactor core and the spent fuel.  While there is backup power for the reactor cooling system, there’s none for the spent-fuel pool.

“Exelon … was concerned that if the water rose over 7 feet it could submerge the service water pump motor that is used to cool the water in the spent fuel pool,” reported Reuters.  In fact, the flood peaked at nearly 7-and-a-half feet, above the threshold, but the pump motors continued operating.

Vulnerable systems like this are in place at nuclear plants across the country, where fuel rods are often stored in large pools that must be supplied with a constant source of fresh water.  Without that supply, the pool could boil in a day thanks to the residual heat of the radioactive fuel rods.  That almost happened at Fukushima-Daiichi, and the spent-fuel pool at that plant remains at risk today.  Nuclear industry spokespersons were full of assurances in the last few days that such a thing could never happen in this country.  An Exelon spokesman said the company’s nuclear facilities have “multiple and redundant” cooling systems.  U.S. nuclear power is “a whole different ballgame” than the Japanese industry, maintained Tom Kauffman of the Nuclear Energy Institute.

It could in fact happen here, and judging from the high levels of water at Oyster Creek it nearly did.  A disaster of this magnitude highlights the central flaw of conventional nuclear reactors, which are largely based on technology nearly a half-century old (Oyster Creek went critical in December 1969).  As I explain in SuperFuel: Thorium, the Green Energy Source for the Future, nuclear plants are controlled by elaborate engineering systems, with backup diesel generators and supposedly fail-proof systems, to keep the reactor and the spent fuel pools cool in emergencies.  The nature of Sandy-caliber disasters, though, is that such systems often fail.  Our nuclear fleet is one major flood away from a full-on disaster, and major floods are getting more common yearly.  Meanwhile, inherently safe reactor technology, like the liquid-fuel thorium reactor, cannot melt down or overheat due to the design and the physics of the machine.

We’ve been hearing reassurances like the ones this week from the nuclear power industry for decades, but the machines themselves just keep getting older.