Imagine, if you will, the unimaginable – a freak earthquake hits south central Pennsylvania and knocks out all electricity to the Peach Bottom nuclear station in York County.
Even the backup generators are lost.
Control room operators, unable to shut the plants reactors down, are powerless to prevent a meltdown.
The scenario is nearly identical to the disaster that hit the Fukushima Dai-Ichi plant in Japan nearly a year ago.
And what consequence would this disaster have on the surrounding region? The answer, according to a detailed computer study conducted by the U.S. Nuclear Regulatory Commission, is very little, at least in terms of radiation exposure and short-term and long-term deaths.
According to the study, which bears the cumbersome name State-of-the-Art Reactor Consequence Analyses, or SOARCA, there would be less radiation released into the atmosphere than previous studies suggested, no short-term deaths, and long-term cancer rates millions of times lower than expected.
Even in a worst-case scenario where reactors catch fire and begin to melt, the threat would be minimal compared to what happened in Japan.
“…Analyses indicated that the accidents progress more slowly and with smaller releases [of radioactivity to the atmosphere,]” the report said.
The finding was significantly less threatening that a 1982 study that predicted a large radiation release after 90 minutes.
The NRC’s staff confirmed the findings by running each computer scenario twice. Each time the result was the same, said Kathy Gibson, director of the NRC’s Division of Systems Analysis in the office of nuclear research.
“The SOARCA indicated that even if operators are unsuccessful at stopping the accident, the releases progress much more slowly and release less radiation that what has been projected in previous studies,” she said.
Why? In short, better regulations – many imposed after the 9-11 attacks – and well-planned and rehearsed emergency response plans, the NRC study concluded.
Because the releases are slower in coming, Gibson said, it allows more time for evacuations which could reduce health risks.
“What SOARCA shows is that the regulations we have in place will keep the public safe even in the face of a nuclear accident,” said Scott Burnell, a spokesman for the NRC.
The study, launched in 2007, well ahead of the Fukushima disaster, is encouraging news for the nuclear industry, whose forward momentum in the last decade was derailed by the disaster in Japan.
“The NRC’s new state-of-the-art analyses confirm that U.S. nuclear power plants are built with a highly effective defense-in-depth protocol that uses multiple layers of safety barriers and redundant systems to assure public health and safety even in severe circumstances,” said Tom Kauffman, a spokesman for the Nuclear Energy Institute, an industry lobbying group.
But watchdog groups, including the Union of Concern Scientists, which obtained a copy of the draft report for review last year, say the study underestimated some circumstances, and failed to consider others altogether.
“SOARCA significantly under-predicted the magnitude of potential hydrogen explosions compared with what actually happened at Fukushima,” said Edward Lyman, a senior scientist with the UCS. “This indicates serious problems with the NRC analyses that the agency must resolve before they can be used to reliably model severe accidents.”
Lyman also challenged the NRC’s assertion that cancer deaths would be lower than previously thought.
“The new study shows that, at least for the 50-mile population, the average predicted risk of cancer deaths is only a factor of 3 lower than if one assumes the worst-case radiation release characteristics used” in a 1982 study, he wrote in a blog on the UCS’s website. “Given the large uncertainties associated with studies of this kind, a difference of a factor of 3 is not significant, so one can conclude that SOARCA essentially confirms, rather than refutes, the results of past studies.”
The NRC will hold a public meeting to discuss the study and answer questions from 5-9 p.m., Wednesday, Feb. 22, at the Peach Bottom Inn, 6085 Delta Road, Delta, Pa.
The NRC modeled the study on two nuclear plants, the boiling water reactor at Peach Bottom, which is similar to the Fukishima plant; and a pressurized water reactor at Surrey, Va., which is similar to the reactors at Three Mile Island.
The plants were chosen because they are typical of most of the 104 reactors in the U.S, said Brian Sheron, director of the NRC’s office of Nuclear Regulatory Research.
“I would imagine that in the future, the BWR and PWRs will be influenced by this,” he said.
SOARCA team members combined the latest information about the plants’ layouts and operations with local population data and emergency plans, then analyzed it using state-of-the-art computer codes to incorporate decades of research into severe reactor accidents.
“We tried to be as realistic as we could,” Gibson said.
The smaller radiation releases and reduced cancer deaths were attributed to changes mandated by the NRC after the 9-11 attacks, particularly new pumps and back-up power supplies.
“Those show a significant benefit in accident situations,” said Burnell.
The modeling also showed that, even if meltdown occurs, more radioactive materials will remain inside the containment building, sticking to walls and debris, and reducing outside radiation levels.
The UCS’s Lyman, said the study assumes populations around the plant will be safely evacuated before a large radiation release occurs, but does not consider the alternative.
“It says nothing about the potential for acute fatalities if releases occurred before residents living near the facility were evacuated,” he said.
Such assumptions “indicate serious problems” that should be addressed before the SOARCA study can be used reliably model severe accidents, Lyman said.
Eric Epstein, chairman of the watchdog group Three Mile Island Alert and co-founder of RocktheCapital, cautioned against over reliance on computer modeling. The models have value, he said, but the lesson of Fukishima, a natural disaster followed by a nuclear catastrophe, is that it is not possible to predict every outcome.
“The plants are getting older and the weather is getting more severe,” Epstein said. “The opportunities for bad things to occur increases as the plants get older. It’s just basic engineering.”
Scott Portzline, a Harrisburg resident who has spent decades as a citizen watchdog, particularly in nuclear plant security, cautioned that the NRC’s computer model was incapable of measuring a significant variable in any accident scenario – confusion.
“Confusion cannot be accurately modeled by a computer simulation because of its thousands of possibilities,” Portzline wrote in a presentation he plans to make before the NRC Wednesday. “Intelligence may be advanced, but confusion knows no bounds.”
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