A Nebraska environmental group wants federal regulators to keep the Fort Calhoun nuclear plant shut down because it would be inundated by floodwaters in the unlikely event of a dam failing upstream.
The Clean Nebraska group says that the Nuclear Regulatory Commission's own assessment of the flood threat at the plant about 20 miles north of Omaha predicts all major equipment at Fort Calhoun would be flooded if the Oahe dam on the Missouri River failed.
The NRC says in its memo that this flooding issue at Fort Calhoun did not represent an immediate safety concern. Regulators say the problem could be addressed later as part of the agency's long-term effort to improve the safety of all nuclear plants in the wake of Japan's nuclear crisis last year.
The Clean Nebraska group argues that the flood threat is more pressing because the NRC estimates that dam failure could create floodwaters 46 feet higher than Fort Calhoun is prepared to handle.
"We now know that the flooding hazard at Fort Calhoun greatly exceeds the plant's flooding protection measures. It's not speculative; it's a real problem now," says David Lochbaum, nuclear safety director at the advocacy group Union of Concerned Scientists.
NRC spokesman Victor Dricks says this analysis of the flood threat at Fort Calhoun is preliminary and was designed to look at the consequences of a worst-case scenario. Dricks says the analysis doesn't suggest dam failure is likely.
"It's not an issue that needs to be addressed prior to any potential restart of the plant," Dricks says.
Omaha Public Power District (OPPD) spokesman Jeff Hanson says the utility has conducted an extensive analysis of the flood threats at Fort Calhoun and developed a strategy that would protect the public in the unlikely event of dam failure.
"In such an event, the containment building would withstand the floodwaters and the fuel would be protected," Hanson says.
OPPD is in the midst of reanalyzing flood threats as part of the NRC's larger review of unlikely safety threats in the wake the nuclear meltdowns at Japan's Fukushima Dai-ichi plant, Hanson says.
Fort Calhoun initially shut down for routine maintenance in 2011, but last summer's flooding along the Missouri River and several regulatory violations have forced it to remain offline.
The recent violations that have kept Fort Calhoun offline include a small electrical fire in June 2011, the failure of a key electrical part during a 2010 test and deficiencies in flood planning that were discovered a year before last summer's extended flooding along the Missouri River.
The record flooding last summer reached as high as 1,006 feet above sea level at Fort Calhoun, but the Omaha Public Power District was able to protect the core of the plant because it has planned to handle flooding up to 1,014 feet above sea level.
The NRC memo says the failure of the Oahe dam on the border with South Dakota could create flooding as high as 1,060 feet above sea level at Fort Calhoun. This analysis of the worst-possible flood threat at Fort Calhoun was done in response to last summer's record flooding, Dricks says.
Since the Clean Nebraska group obtained a copy of the memo, the NRC has redacted a number of key details, including the height of the floodwaters expected and the name of the dam.
Dricks says those details were removed because of security concerns about terrorists obtaining that information.
"There was no attempt on the part of the NRC to withhold information on the nature of the issue from the public," Dricks says.
Last month, OPPD hired Exelon Corp. to run Fort Calhoun for the next 20 years as part of its plan to bring the plant back online. Exelon had already been advising the utility on Fort Calhoun's recovery since January. Now, the private company will provide day-to-day management of the plant.
Chicago-based Exelon operates 17 reactors at 10 nuclear power plants in Illinois, Pennsylvania and New Jersey.
This summer, the Sierra Club of Iowa asked federal regulators to consider revoking the plant's license because of its history of safety violations. The Nuclear Regulatory Commission held a hearing on the Sierra Club's petition last month, but it has yet to rule on it.
Nuclear Regulatory Commission officials say there is no timeline for restarting the plant, and they won't allow Fort Calhoun to resume generating electricity until they are certain it is safe.
Dricks says the NRC didn't immediately conduct a similar flood threat analysis for the state's other nuclear plant, Nebraska Public Power District's Cooper station, because it is roughly 100 miles downstream.
Cooper also faces less risk of flooding because it sits on higher ground next to the river near Brownville, Neb.
But Dricks says Cooper will address the risk of upstream dam failure as part of the larger NRC review of safety threats to nuclear plants. U.S. nuclear plants must report to regulators on those threats by 2014.