Expect the unexpected when it comes to nuclear power accidents, experts said Thursday in a report on the lessons learned from the 2011 disaster in Fukushima, Japan.
The industry and regulators must “seek out and act on” any new data about hazards, they reported, as well as take into account rare, low probability incidents -- not just the ones that plants were designed to withstand.
A case in point: Fukushima was designed to withstand a tsunami but not to have its power completely cut off, which is what happened and what caused staff to lose control of the six reactors there.
In fact, the experts noted, the world's other two major nuclear accidents -- Chernobyl and Three Mile Island -– were also incidents described as "beyond design basis."
In the U.S., the Nuclear Regulatory Commission still regulates based on "design basis" accidents, but those regulations "are clearly inadequate for preventing core-melt accidents," according to the report, which was requested by Congress and released by the National Research Council.
Fukushima, for example, involved problems with multiple reactors. Traditional risk assessment is based on a single accident at an individual unit, not having multiple reactors with problems, said study director Kevin Crowley.
"That was a different kind of accident that we just hadn't thought about when doing risk assessment," he said.
In the U.S, 70 percent of all nuclear reactors are sited at plants along with other reactors, noted panel member John Garrick, an independent nuclear power consultant.
The issue of looking at “beyond-design-basis” events is controversial within the nuclear industry and even the Nuclear Regulatory Commission, since planning for extremely rare incidents has not been part of the culture in 40 years of plant design and construction.
In a statement emailed to NBC News, the Nuclear Regulatory Commission accentuated the positive aspects of the report: It thanked the expert committee, and said it was "particularly pleased the committee noted the agency's status as a strong, independent regulator."
"The agency’s staff will review the report in depth and provide the commissioners with detailed comments in the near future," the statement said.
The Nuclear Energy Institute, an industry group, said in its own statement that the report "affirms the culture of safety adhered to by the U.S. nuclear industry."
Recommendations on safety strategies
The expert committee's advice for improving safety measures is worth pursuing, said Jacopo Buongiorno, a nuclear engineering professor at the Massachusetts Institute of Technology. While the shift has been slow, the Nuclear Regulatory Commission “is moving toward more risk-informed regulations, and that trend should be encouraged,” said Buongiorno, who did not help prepare the report.
Other recommendations included having regulations independently peer-reviewed, a continuous monitoring of safety culture, and training staff to make ad hoc decisions if the unexpected happens, said panel member Jan Beyea, a scientist with Consulting in the Public Interest.
The panel also advised exploring whether evacuating people around a nuclear accident is always the best strategy. "It is not clear at all and in fact it is dubious that the current evacuation-focused strategy minimizes the overall impact of a severe accident on the local population," said Buongiorno. "Sheltering in place may ensure low doses and it doesn't create the stress on children and older people."
"Studying the long-term social, psychological, and economic impacts of sheltering-in-place versus evacuating would be very a valuable contribution to the development of a rational and effective strategy to cope with releases," he said.