|Fort Calhoun Nuclear Facility|
These charges were echoed in separate conversations with another risk engineer inside the agency who suggested that the vulnerability at one plant in particular -- the three-reactor Oconee Nuclear Station near Seneca, S.C. -- put it at risk of a flood and subsequent systems failure, should an upstream dam completely fail, that would be similar to the tsunami that hobbled the Fukushima Daiichi nuclear facility in Japan last year. That event caused multiple reactor meltdowns.
In the letter, a copy of which was obtained by The Huffington Post, Richard H. Perkins, a reliability and risk engineer with the agency's division of risk analysis, alleged that NRC officials falsely invoked security concerns in redacting large portions of a report detailing the agency's preliminary investigation into the potential for flooding at U.S. nuclear power plants due to upstream dam failure.
In addition to the Oconee facility, the report examined similar vulnerabilities at the Ft. Calhoun station in Nebraska, the Prairie Island facility in Minnesota and the Watts Bar plant in Tennessee, among others.
Perkins was the lead author of that report, which was completed in July of 2011 -- roughly four months after an earthquake and subsequent tsunami flooded the Fukushima Daiichi nuclear power plant in Japan, cut off electric power to the facility and disabled all of its backup power systems, eliminating the ability to keep the reactors cool and leading to a meltdown.
The report concluded, among other things, that the failure of one or more dams sitting upstream from several nuclear power plants "may result in flood levels at a site that render essential safety systems inoperable." High floodwaters could conceivably undermine all available power sources, the report found, including grid power, emergency diesel backup generators, and ultimately battery backups. The risk of these things happening, the report said, is higher than acceptable.
"The totality of information analyzed in this report suggests that external flooding due to upstream dam failure poses a larger than expected risk to plants and public safety," Perkins's report concluded, adding that the evidence warranted a more formal investigation.
In response to the report, the NRC launched an expanded investigation, which is ongoing. It also folded the dam failure issue into the slate of post-Fukushima improvements recommended by a special task force formed in the aftermath of that disaster. But in a press release dated March 6 of this year, the agency said the report "did not identify any immediate safety concerns."
The NRC made a heavily redacted copy of the report publicly available on the NRC website the same day.
"Nuclear power plant designs include protection against serious but very rare flooding events, including flooding from dam failure scenarios," the agency release noted. "Dam failures can occur as a consequence of earthquakes, overflow, and other mechanisms such as internal erosion and operational failures. A dam failure could potentially cause flooding at a nuclear power plant site depending on a number of factors including the location of the dam, reservoir volume, dam properties, flood routing, and site characteristics." More