nuclear-news

Accidents that American reactors are designed to withstand, like a major pipe break, are “stylized” and do not reflect the bigger source of risk, which is external, according to the study. That conclusion is one of the major lessons from the Fukushima Daiichi nuclear accident in Japan in 2011, which began after an earthquake at sea caused a tsunami.

The Nuclear Regulatory Commission calculates which problems are most likely and most troublesome, and aims to find components or systems that should be improved. B. John Garrick, a nuclear engineering consultant and vice chairman of the two-year study, said that engineers had more experience calculating the probability of failure in a valve or a pipe than in predicting earthquakes or floods. Better predictions of such events were possible, he said.

The study, ordered by Congress after the triple meltdown at Fukushima Daiichi’s reactors, said that the Nuclear Regulatory Commission and the American nuclear industry should focus on the main sources of risk: accidents set off by “extreme external events,” like earthquakes or floods; multiple human or equipment failures; and “violations of operational protocols.”……….

In addition, the study said that safety officials should take into account the reduced capacity and maneuverability of outsiders to help a nuclear plant in trouble after a major earthquake or flood.

The United States should study costs not currently accounted for in making cost-benefit analyses about safety, like the expense of decontaminating areas distant from the plant, which the authors said was another lesson of Fukushima.

Psychological and social costs of evacuation or “sheltering in place,” meaning the confinement of people to homes, should also be considered, the study said, and so should decision-making about resettling people who had been evacuated because of the release of radioactive material.

And if two reactors at the same site had an accident at the same time, the study said that staffing might be inadequate for an event of long duration.

Congress also asked the academy to study the safety of spent-fuel storage,an area of concern since the Japanese accident. In the Fukushima accident, American officials became convinced — mistakenly — that water had drained or boiled from a pool of spent fuel and they urged Americans in Japan to stay 50 miles away. But the academy has not finished that part of its study.http://www.nytimes.com/2014/07/25/us/nuclear-plants-should-focus-on-risks-posed-by-external-events-study-says.html?_r=0