OMAHA, Neb. (AP) — Regulators have told the utilities that own Nebraska's two nuclear power plants not to worry about some unlikely scenarios under which upstream dams might fail, even though regulator had ordered the utilities to study the flood risks facing the plants.
The Omaha and Nebraska Public Power Districts are re-examining flood threats at their nuclear plants that sit on the Missouri River as part of an industrywide review of unlikely safety threats after the 2011 meltdowns at the Fukushima Dai-ichi plant in Japan.
The Nuclear Regulatory Commission told the utilities this month that they didn't need to consider two of the five dam failure scenarios experts developed.
NRC officials didn't immediately respond Monday to questions about the decision.
Officials have been concerned about the potential for flooding at the two nuclear power plants since the historic flooding along the Missouri River in 2011.
OPPD's Fort Calhoun nuclear power plant sits on the banks of the river about 20 miles north of Omaha, and was surrounded by water during the flooding three years ago.
NPPD's Cooper nuclear station sits on the river's banks near Brownville, in southeast Nebraska. It was also threatened by the 2011 flood, but the plant sits on more elevated land and is roughly 100 miles downstream from Fort Calhoun, so the water was less of a threat.
In addition, an internal NRC report that was made public in 2012 estimated that the failure of an upriver dam could cause flooding that is 46 feet higher than Fort Calhoun is prepared to handle in a worst-case scenario.
Adding to the concerns about Fort Calhoun is the fact that regulators forced the plant to remain offline from April 2011 until last December while they addressed several regulatory violations and made sure the flood damage was repaired. OPPD had to deal with a small electrical fire in June 2011, address structural concerns and retrain workers to respond aggressively to safety concerns.
Mike Ryan, a spokesman for the environmental group Clean Nebraska, said he's worried that the study will downplay the risks posed by the upstream dams on the Missouri River. But he said he's not sure if the utilities could ever adequately prepare for such a scenario.
"With the utilities being in charge of the studies, I'm afraid they're going to paint the most optimistic picture possible," Ryan said.
Neither the OPPD nor the NPPD responded to questions about the flood study that were submitted to spokesmen for the agencies earlier Monday.
In the past, both utilities have stressed that they have plans in place to protect the nuclear plants from severe flooding. And the utilities and regulators say it is extremely unlikely that a dam will fail.
Independent expert David Lochbaum, of the nonprofit group the Union of Concerned Scientists, said it appears regulators decided the flooding scenarios were similar enough that the utilities don't need to prepare for all of them.
Regulators have given other nuclear plant operators in Tennessee and South Carolina similar guidance as they evaluate flooding hazards. Lochbaum said he's glad utilities are looking at the possibility of dam failures and not strictly relying on the dam remaining intact to protect nuclear plants.
"The protection measures taken against some flooding measures also provide protection against the dismissed scenarios," said Lochbaum, who oversees the nonprofit's Nuclear Safety Project.
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NRC page on Fort Calhoun: http://1.usa.gov/GBq2TF
Omaha Public Power District: http://www.oppd.com
Nebraska Public Power District: http://www.nppd.com