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Regulators Aware for Years of Understated Seismic Risks to Nuclear Plants

Despite six years of study, industry collaboration, and a missed deadline, no decision on reactor fixes

by Jim Morris and Bill Sloat

Nearly six years before an earthquake ravaged Japan’s Fukushima Daiichi nuclear power plant, U.S. regulators came to a sobering realization: seismic risks to nuclear plants in the eastern two-thirds of the country were greater than had been suspected, and engineers might have to rethink reactor designs.

What are the risks of an earthquake beneath a reactor near you? This image combines a 2006 map by the United States Geological Survey showing varying seismic hazards across the U.S. with locations of nuclear reactors. Reactors in black are active; reactors in blue are proposed sites for the new model known as the AP1000. Probability of strong shaking increases from very low (white), to moderate (blue, green, and yellow), to high (orange, pink, and red). Credit: Kimberly Leonard/Center for Public Integrity. Thus began a little-noticed risk assessment process with far-reaching implications despite its innocuous-sounding name: Generic Issue 199. The process, which was supposed to have been finished nearly a year ago, is still under way. It is unclear when it will be completed.GI-199, as it is known, was triggered by new geophysical data and computer models showing that, as the Nuclear Regulatory Commission put it in an August 2010 summary document, “estimates of the potential for earthquake hazards for some nuclear power plants in the Central and Eastern United States may be larger than previous estimates.” 

Data from the U.S. Geological Survey and other sources suggest, for example, that “the rate of earthquake occurrence … is greater than previously recognized” in eastern Tennessee and areas including Charleston, S.C., and New Madrid, Mo., according to the NRC document. There are 11 reactors in Tennessee, South Carolina and Missouri.

GI-199, a collaborative effort between the NRC and the nuclear industry, has taken on new urgency in light of the crisis in Japan. “Updated estimates of seismic hazard values at some of the sites could potentially exceed the design basis” for the plants, the NRC document says.

NRC spokesman Roger Hannah said the exercise was never meant to provide “a definitive estimate of plant-specific seismic risk.”  Rather, he said, it was done to see if certain plants “warranted some sort of further scrutiny. It indicates which plants we may want to look at more carefully in terms of actual core damage risk.”

The information collected under GI-199 has been shared with operators of all 104 reactors at 64 sites in the U.S., Hannah said, and NRC officials are in the process of determining whether any plants require retrofits to enhance safety. He added that the assessment indicated “no need for any immediate action. The currently operating plants are all safe from a seismic standpoint.”

Every proposed nuclear plant in the U.S. already must undergo an extensive environmental review that examines the site’s seismology, hydrology and geology, NRC spokesman Joey Ledford said.

The Nuclear Energy Institute, a trade group, said in a statement this week that nuclear plants “are designed to withstand an earthquake equal to the most significant historical event or the maximum projected seismic event and associated tsunami without any breach of safety systems.” The U.S. Geological Survey updates its seismic hazard analyses roughly every six years, the institute said, and “the industry is working with the NRC to develop a methodology for addressing” newly recognized hazards.

Asked why GI-199 has taken nearly six years, Ledford said, “These are very complicated issues. We’re talking about 64 plant sites. It’s not a small task.” According to a January 2010 NRC document, GI-199 was to have been completed last April.  An agency document dated January 2011 says the completion date is “to be determined.”  The NRC blamed the delay on issues relating to the release of a copyrighted Electric Power Research Institute report to an NRC contractor and on “the desire for internal and external stakeholder agreement.” Over the years, the NRC often has been criticized for taking too long to resolve important safety issues. One example: what’s known in the industry as a loss-of-cooling accident, regarded as the most serious event that can happen at a reactor. Since the 1980s, the NRC has been looking into the problem of clogged emergency core cooling pumps in boiling water reactors. The issue has not been resolved. The Fukushima Daiishi reactor and 35 reactors in the U.S. are boiling water reactors.

[...]

Events Get Ahead of the Regulators

Earthquakes can occur in all sorts of locales. In January 1986, a late-morning quake measuring 4.96 on the Richter scale was blamed for cracks in the Perry Nuclear Power Plant on Lake Erie near Cleveland.  At first, people thought it wasn’t a quake; speculation focused on an explosion somehow related to the Challenger space shuttle disaster or an attack on New York City. The newly licensed plant’s reactor was to be fueled for the first time the next day. Officials and the public were caught by surprise; few suspected Northeastern Ohio was in an active seismic zone. But it is. Experts determined that the quake’s epicenter was 11 miles from the plant, which has been dogged by controversy ever since.

A previously unknown fault line also runs near the Indian Point plant, 24 miles north of New York City. Indian Point’s two units are up for relicensing by the NRC in 2013 and 2015, respectively, and a fierce battle is expected. New York Gov. Andrew Cuomo, while campaigning last year, called for Indian Point to be closed. Now he has ordered a safety review of the plant. In a 2008 paper, four researchers from Columbia University reported that “Indian Point is situated at the intersection of the two most striking linear features marking the seismicity and also in the midst of a large population that is at risk in case of an accident at the plants.”  Indian Point’s two reactors, the researchers noted, “are located closer to more people at any given distance than any other similar facilities in the United States.”

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