Friday, February 03, 2012

SOARCA and the Decreasing Risk of Death

How likely is it that a major accident at a nuclear energy facility would kill you? Japan just had such a major accident and no one died due to radiological exposure – there were industrial accidents at Fukushima that led to worker death but those were specific to occurring at a physical plant. The general public, while suffering displacement and its attendants stresses – not to mention those caused by the earthquake and tsunami that precipitated the accident – has been fatality free.

The NRC has been investigating the risk of death from a nuclear facility accident and has an answer: your risk is vanishingly small.

The study found there was "essentially zero risk" to the public of early fatalities due to radiation exposure following a severe accident. The long-term risk of dying from cancer due to radiation exposure after an accident was less than one in a billion and less than the U.S. average risk of dying from other causes of cancer, which is about two in one thousand.

Another conclusion: severe accidents at nuclear energy facilities would unfold more slowly and potential releases of radioactive material would be much smaller than earlier studies indicated.

The NRC looked at Surry and Peach Bottom for the study because they are different kinds of reactors.

If core cooling is not restored [following an accident], the NRC said containment failure and radiological release could begin at about 8 hours for Peach Bottom and at 25 hours for Surry.

That’s the worst case scenario, of course, with safety systems intended to prevent its occurrence at multiple points. (Remember, though, that this report assumes that all these systems fail and radiation is released – that eventuality is what it wants to model)

The story doesn’t go into evacuation, but the report does:

For the purposes of evaluating accident consequences in the SOARCA project, the most evident part of a plant's emergency response plan is the evacuation of the public in the 10-mile (16-km) plume exposure pathway Emergency Planning Zone (EPZ). Actions in this EPZ could be expanded if the plume projections suggest that the population in a wider area need to take protective actions. Thus, the project team assessed additional aspects of emergency response, including relocation from areas of relatively high potential for exposure, as well as variations of evacuation and sheltering of population groups outside the 10-mile EPZ to a distance of 20 miles from the plant.

The plume is what many think of as a cloud of radiation.

The report also says that existing safety measures—including those put in place after 9/11—would be highly effective in protecting the public. Moreover, even if mitigating measures fail or are not used, “the analyzed accidents would cause essentially zero immediate deaths and only a very, very small increase in the long-term cancer deaths.”

Any industry – from chemical and gas plants to paper mills to refineries – has to know the worst possible event that can happen and figure out how to keep people alive though it and get them out of the way should it occur. These are the risks of an industrialized society and not specific to the nuclear energy industry.

But it does suggest the responsibility industry and government regulators have to know the risks and how to mitigate them. This report, State-of-the-Art Reactor Consequence Analyses (or SOARCA, in Washington-acronym speak), provides a careful analysis and concludes that the risk is present, and must be acknowledged, but it is very, very small.

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