BOSTON — It may seem easy to prevent a nuclear accident like the one in Fukushima, Japan: avoid building reactors near a fault, or on a coastline vulnerable to tsunamis.
But it’s not quite that simple.
In fact, neither the jolt of tectonic plates grinding together nor the massive wave were directly responsible for the calamity. True, the 9.0-magnitude quake was larger than the reactor was designed to handle. Yet none of the six reactors at the station crumbled under the assault. Instead, the emergency systems kicked in, shutting down the three reactors that were operating at the time of the disaster (the other three were off for maintenance).
It was something far more mundane that triggered the accident: A blackout.
Nuclear facilities generate enormous amounts of heat even when they’re shut off. So it is essential that cooling systems continue operating. If not, the heat will eventually boil off the cooling water, melting the fuel into one very hot, uncontrollable mass. Because the reactors were down, because the electric grid was destroyed, and the diesel generators were washed away by the tsunami, there was no power left to run the cooling systems.
So a power cut is the culprit. Ever have one of those in your neighborhood?
If you think your local nuclear power plant is prepared to handle such a mundane event, you may want to heed the warnings of Dr. David Lochbaum, who directs the nuclear safety project at the Union of Concerned Scientists, a watchdog that is neither for nor against nuclear power.
“As at Fukushima, U.S. reactors are designed to cool the reactor core during a station blackout of only a fairly short duration,” Lochbaum told the Senate Energy and Natural Resources Committee (emphasis added). “It is assumed that either the connection to an energized electrical grid or the repair of an emergency diesel generator will occur before the batteries are depleted.”
In the United States, 104 reactors produce 20 percent of the nation’s energy. Only 11 of those, Lochbaum said, “are designed to cope with a station blackout lasting eight hours, as were the reactors in Japan.”
The other 93? They can only hang on for four hours.
Consider an accidental power cut — like, perhaps the one caused by solar flares in 1989 leaving 2 million Quebecois without power for nine hours. Or imagine that someone who didn’t care much for the United States knocked out the electric grid, and then interfered with emergency workers, for example by deploying a dirty bomb. Then add a failure (or knockout) of backup diesel generators. Most American reactors would have only four hours before the cooling systems run out of juice and the fuel starts heating up, triggering a crisis.
But that’s not all. Lochbaum also stated that the U.S. is vulnerable to a spent fuel pool disaster, similar to the one underway at Fukushima.
At issue here is the fuel rods that have already been used in the reactor. These remain dangerously radioactive for many centuries after they are no longer useful to produce electricity. The U.S. lacks a safe place to bury these. Yucca Mountain, Nevada was selected for that purpose in the 1980s, but political and safety concerns have prevented construction. As a result, they’ve been building up at nuke facilities, adjacent to the reactors.
Lochbaum told the Senators that at many U.S. reactors, there is “far more irradiated fuel in the spent fuel pool” than in the reactor itself. This material is cooled “by fewer and less reliable systems” than in the reactor, and is “housed in far less robust structures than surround the reactor core.” This means that any radiation release from a pool will be less-well contained than a release from the reactor core.
“It also means that spent fuel pools are more vulnerable to terrorist attack than is the reactor itself,” Lochbaum concluded. “More irradiated fuel that is less well protected and less well defended is an undue hazard.”
As a near-term alternative, Lochbaum suggested that after an initial cooling period, the fuel should be stored in dry casks. This is currently the practice in Germany, where regulators decided three decades ago that fuel pools were too dangerous in the event of a war.
In response to these lessons from Fukushima, this week Rep. Edward J. Markey (D-MA) introduced legislation requiring nuclear plants to increase their battery capacity to 72 hours, and to have 14 days worth of diesel fuel on-site. The legislation would also halt new reactor licenses or license extensions until regulators enact new safety standards based on the lessons learned at Fukushima.
The Nuclear Energy Institute, an industry association, suggested that Rep. Markey's legislation was redundant with existing regulation. Markey’s “call for a moratorium ignores the Nuclear Regulatory Commission's 90-day safety review and processes already in place in the licensing processes to review new information that may arise during new plant construction,” said Marvin Fertel, NEI president and chief executive officer, in a statement.
"The NRC chairman testified before a Senate committee today that U.S. nuclear plants are safe and secure, and it is 'very unlikely' that the combination of events in Japan earlier this month would occur in the United States. Nonetheless, the NRC is an independent regulator of the nuclear energy industry and therefore can require additional action by the industry as part of its licensing processes. Similarly, Congress has direct oversight of the NRC and has an established process to vet these issues before hastening to legislate changes to the licensing process,” Fertel said.
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