The disaster set in motion on March 11 by a massive earthquake and tsunami struck Japan's Fukushima Daiichi nuclear powerplant in an unlikely place: its spent-fuel pools, where experts speculate that loss of water caused a nuclear reaction among the fuel rods, creating a hydrogen explosion that blew a hole through the pools' relatively flimsy exterior and released radiation into the air.
In the U.S., nuclear plant owners and regulators still say such an event is unlikely, not because exterior containment systems are more robust—they aren't—but because of redundant systems that would keep the water in the pools in the event of a similar incident. “Some simple measures that could have been taken early … would have avoided a lot of the problems [at Fukushima],” says Jeffrey S. Merrifield, senior vice president of the power division at The Shaw Group, Baton Rouge, La., and a former commissioner of the U.S. Nuclear Regulatory Commission. He is puzzled as to why the plant operators did not run firehoses into the containment pools, for instance.