Two employees with the U.S. Nuclear Regulatory Commission (NRC) are accusing the regulators of not being open about the risk of catastrophic flooding at nuclear plants upstream from large dams.

Richard H. Perkins and Larry Criscione came forward independently with concerns that portions of a dam risk assessment had been kept secret since July 2011, and that the issue had been known since at least August 2010.

The document lists 20 operating nuclear power sites where flooding as a result of upstream dam failures are seen as a risk factor, including the 500 MW Fort Calhoun nuclear power plant in Nebraska, which experienced flooding not caused by a dam failure a month before the report was completed in 2011. Also given particular attention in the report are the Oconee Nuclear Station, operated by Duke Energy (NYSE: DUK) near Greenville, SC.; Tennessee Valley Authority's Watts Bar in Tennessee, and the Prairie Island Generating Station in Minnesota, owned by Xcel Energy (NYSE: XEL). According to the NRC report, Duke’s assessment of the likelihood of a failure of the Jocassee dam was low “by an order of magnitude.” Sections of the report the NRC blacked out before releasing it publicly include evidence that both Duke and the NRC have been aware of significant flood risk at the plant since the early 1990s, and that the NRC repeatedly brought their concerns to Duke without insisting that the situation be remedied.

According to The Huffington Post, Criscinoe first raised his concerns in a lengthy letter to the head of the NRC, which he later sent to several members of Congress. Perkins, who led the study that produced the report, wrote a letter to the NRC’s office of the inspector general, in which he alleged “that the Nuclear Regulatory Commission (NRC) has intentionally mischaracterized relevant and noteworthy safety information as sensitive, security information in an effort to conceal the information from the public.”

To read the full report, click here.

Subscribe to Nuclear Power International magazine