NRC: Dam failures could severely damage nuclear plants

By John Williams

The NRC, under pressure from the indie journalists at Portland, Oregon based Cascadia Times, has released a heavily censored report about inadequate flood protection at dozens of US Nuke plants. :

The NRC report admits that regulators initially improperly calculated the likely levels of floods at several nuclear plant sites, and often failed to consider the additional dangers to nukes from upstream dam failures.

In several instances, rather than “hardening” their plants against the additional flood predictions, Nuke plant operators, including Fort Calhoun in Nebraska, have promised the NRC they will implement temporary measures like stacking sandbags if flooding reached the newly predicted levels.

Those temporary measures failed last year at Fort Calhoun.

Originally, the Federal Emergency Management Administration predicted the 100-year-flood at the Fort Calhoun plant, 15 miles north of the 408,000 residents of Omaha, Nebraska, would only reach 1006 feet above sea level. The plant protected itself to 1007 feet. In 1993, the Army Corps re-calculated that floods could reach 1009.3 feet.

Fort Calhoun promised it would make up the difference with flood gates and sandbags. In June 2011, flooding reached 1007 feet. Floodwaters surrounded the plant when the temporary measures, including a “bladder” that was supposed to be a flood wall, failed.

Several other Nukes, according to the NRC report at page 10, are still relying on similar temporary flood control actions. Cooper Station, south of Omaha, will install sandbags and wood planks. Three Mile Island and Vermont Yankee will install floodgates and sandbags, and plug their floor drains, among other measures.

Arkansas Nuclear One, Beaver Valley, Pa., Watts Bar, Tenn, and Sequoyah, Tenn, will just shut down when flooding threatens. Of course, those plants will still need to maintain core cooling with backup equipment and protect the plant from flood damage. However it isn’t clear the Nukes are well-prepared. The NRC warned “…it is not clear that the above (flood) factors were comprehensively and consistently considered for all plants.”

Several nukes are also downstream from large dams, and a dam failure could severely damage those plants. The NRC specifically cited risks to the Oconee plant in southeast South Carolina. Figure 6 in the NRC report also apparently revealed that a half-dozen nuclear plants are within about 10 miles of large upstream dams, and dozens of other plants face flooding risks.

The NRC’s discussed in some detail the dam failure risks at the Watts Bar and Prairie Island nukes. The NRC said the flood safety margin at Prairie Island “becomes negative,” which is engineer-eese for saying the plant will flood if there are “wave effects.”

Watts Bar is hardened against floods up to 728 feet above sea level. Yet “..the maximum probable precipitation event” could cause water to rise to 738.8 feet, apparently leaving part of the plant under 10 feet of water. But the Nuke operator claims its equipment “…is designed to operate submerged.”

Perhaps the most important issue is why the NRC initially withheld this information, and continues to withhold part of it. The NRC has allowed the nuclear industry to secretly delay hardening their plants against these updated flood dangers.

The NRC and other agencies justify their secrecy by claiming that terrorists could exploit these plants’ deficiencies, apparently by blowing up a dam upstream from a nuke. In my opinion, the best way to thwart terrorist attacks is to increase protections for the nuclear plants, not to keep their malfeasances secret.

Finally, I’m pro-nuke. But the Industry tries my patience way too often. This is the latest example.

(Cross posted from Daily Kos.)

Paul Koberstein