Regulators have cited the Tennessee Valley Authority for several violations related to the federal utility's Tennessee River flood preparations.

Sequoyah nuclear plant. Source: TVAThey all involve extreme flooding scenarios that have never occurred before and have since been factored into the emergency planning at the Watts Bar and Sequoyah plants. Nonetheless, the Nuclear Regulatory Commission asserted that both sites were left with inadequate flood preparation measures for an extended period of time.

The NRC issued a yellow finding, its second most serious citation, at Watts Bar related to the plant's potential inability to implement some flood mitigation measures in a timely fashion during that period. Regulators also issued the plant two lower-level white findings related to flood protection to guard against upstream dam failures and for not immediately reporting deficiencies in its emergency planning to the NRC.

At Sequoyah, the NRC said it issued white findings related to the potential for dam failure, for not establishing adequate measures to prevent flood water from entering the plant's intake pumping station and for not quickly reporting the potential deficiencies.

The violations date back to a 2008 reassessment of potential flood conditions along the Tennessee River as part of a license review at TVA's Bellefonte plant. TVA concluded the new data revealed potential conditions that could breach dams upstream of the plants. Although TVA later raised the height of the dams in question, an NRC inspection found that TVA did not account for the potential effects of a dam breach at the plants. The agency determined the Watts Bar flood mitigation strategy was inadequate until July 2012.

In a statement Wednesday, TVA said, "We take the regulatory deficiencies noted by the Nuclear Regulatory Commission very seriously and have taken steps to immediately address many of the conditions identified by the NRC. In addition, TVA has committed to install an entirely new layer of redundant reactor safety systems in seismically reinforced buildings located above probable maximum flood levels, further strengthening our ability to protect the public even under the most extreme conditions."