published Thursday, March 17th, 2011

Quake faults could affect Sequoyah, Watts Bar

  • photo
    Sequoyah Nuclear Plant near Soddy-Daisy, Tenn. The plant is operated by the Tennessee Valley Authority.
    Photo by Dan Henry /Chattanooga Times Free Press.


In addition to what’s inside the core of six local reactors, TVA stores spent fuel and fuel rods at all three operating plants. In March, 2010, the stored wastes included:


1,094 metric tons

  • 812 in pool storage inside the plant
  • 282 in casks outside the plant

Watts Bar

315 metric tons, all in pool storage inside the plant

Browns Ferry

1,604 metric tons

  • 1,415 in pool storage inside the plant
  • 189 in casks outside the plant

TOTAL: 3,013 metric tons

Source: Tennessee Valley Authority

The two reactors at TVA’s Sequoyah Nuclear Plant in Soddy-Daisy have the nation’s fourth-highest earthquake risk, according to assessments by the Nuclear Regulatory Agency.

Understanding of the risk at TVA nuclear plants at Sequoyah, Watt’s Bar in Spring City, Tenn., and Browns Ferry in Athens, Ala., has grown in recent decades as knowledge has increased about earthquake research and fault mapping.

What’s unclear now is what, if any, changes the upgraded risks might prompt.

At Sequoyah, about 20 miles north of Chattanooga, the chances of an earthquake causing core damage at each reactor are 1 in 19,608, according to an analysis of new NRC risk assessments.

For local residents, those core odds are far greater than the chance of being struck by lightning, which the National Weather Service says is about 1 in 500,000.

NRC spokesman Roger Hannah on Wednesday said the analysis and a spreadsheet ranking of the nation’s plants and their risks shouldn’t be misinterpreted.

“It doesn’t mean there is a safety issue or need for immediate action,” Hannah said. “It may be determined that nothing needs to be done.”

Up the road in Spring City, Tenn., the Watts Bar Nuclear Plant, licensed in 1996, has the 14th-highest quake risk among the nation’s 65 operating plants.

There, the chance for reactor core damage is 1 in 27,778, according to the NRC.

And at Browns Ferry, licensed in the 1970s, the odds are 1 in 185,185 in reactors 2 and 3. Reactor 1’s risk is 1 in 270,270.

Learning more

While Japan faces a crisis at a nuclear plant damaged after a 9.0 magnitude earthquake caused a tsunami, TVA called off a long-scheduled media tour Wednesday at its Watts Bar plant, the site of the only U.S. nuclear reactor under construction.

The utility said in a statement that the tour was indefinitely postponed “while the industry focuses on events in Japan.”

When Sequoyah was licensed in 1980 and 1981, its risk for quake-induced core damage was 1 in 102,041. TVA officials have said it was built to withstand a 5.8-magnitude quake.

But at that time, most geologists thought the nearest seismic zone of note was West Tennessee’s New Madrid fault. That fault let go in a series of quakes in 1811-1812 that formed Reelfoot Lake in West Tennessee and made the Mississippi River run backward for a time.

In the years after Sequoyah’s design, researchers began studying the East Tennessee Seismic Zone, which scientists now know is the second-most-active quake zone east of the Mississippi River.

Stretching up along the Tennessee mountains from Alabama to Virginia, the 185-mile-long, 30-mile-wide East Tennessee seismic zone runs right through Chattanooga and the tri-state area.

It was responsible for a 4.6-magnitude quake near Knoxville in 1973 and a 4.6 quake near Fort Payne, Ala., in 2003.

TVA spokesman Ray Golden said conversations have just begun among TVA officials and NRC about the new risk assessments.

“There is a design basis [in place now] for all of our plants, and we are in full compliance with that. We will abide by whatever [new] requirement NRC has for us,” he said.

Hannah said it’s too early to know if the assessments will prompt changes, or what those changes might be. The rankings to help NRC prioritize further study were just completed in the fall, he said.

“We’ll be sending letters soon,” he said.

For now, a Sept. 2, 2010, memorandum sums up the work on “Generic Issue 199,” as the effort is labeled in NRC documents online.

“Recent data and models indicate that estimates of the potential for earthquake hazards for some nuclear power plants in the Central and Eastern United States may be larger than previous estimates. While it has been determined that currently operating plants remain safe, the recent seismic data and models warrant further study and analysis.”

about Pam Sohn...

Pam Sohn has been reporting or editing Chattanooga news for 25 years. A Walden’s Ridge native, she began her journalism career with a 10-year stint at the Anniston (Ala.) Star. She came to the Chattanooga Times Free Press in 1999 after working at the Chattanooga Times for 14 years. She has been a city editor, Sunday editor, wire editor, projects team leader and assistant lifestyle editor. As a reporter, she also has covered the police, ...

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fftspam said...

An earthquake and Sequoyah makes for a good headline... but, remember, the cooling problems at the Japanese Nuke were not caused by the quake... they were, as stated, caused by the tsunami knocking out power and multiple layers of backup. Yes, undoubtedly, it is a comedy of errors down to 'the plug didn't fit' and the switch was in a flooded basement. The cooling equipment is not damaged. Once power is restored to the plant, cooling will be restored. What the story does not address is... how strong are TVA's procedures for immediately shutting the plant down in case of any emergency? And what sort of 'monday morning quarterbacking' is already going on within TVA when they look at the Japanese crisis and looking at their own plans? Follow up please.

March 17, 2011 at 12:38 a.m.
inquiringmind said...

I can't call it a comedy of errors, but you are right the engineering design remarkably withstood the 4th or so greatest modern earthquake of magnitude 10X larger than the design goal (7.9). I only worry about the blind spots in our design thinking, I mean put a set of reactors on the coast in one of the more seismically active areas of the world and not think possible tsunami and possible impact on backup power, and have the third line of defense lead-acid batteries that last 4 hours? I guess that allows enough time to evacuate the plant in advance of impending total failure.

That's the challenge with design errors, and I don't fault TVA for rethinking design in light of this lesson.

March 17, 2011 at 8:43 a.m.
smdrlk said...

All TVA Nuclear Plants have an automatic shut off sytem during emergencies.

March 17, 2011 at 8:50 a.m.
mtngrl said...

"All TVA Nuclear Plants have an automatic shut off sytem during emergencies."

So do the ones in Japan, including Fukushima Dai-ichi. All 3 running reactors immediatly shut down as soon as the quake hit - but that does not mean they are safe as we are now seeing.

You still convinced we are not in an earthquake zone and are totally safe smdrlk? Nothing at all to worry about, right?

Notice we are also storing spent fuel in the same method as Japan.

March 17, 2011 at 10:34 a.m.
riverstronghold said...

Producing nuclear weapons material (Tritium) at Sequoyah and/or Watts Bar increases potential terror targeting of these facilities.

Using reprocessed nuclear warhead (mixed oxide/mox) (as proposed by TVA) fuel mixtures increases the danger of any release which might occur, engineering design notwithstanding.

Spent fuel cooling ponds are as dangerous or more dangerous targets than the reactors.

Engineering is not the only issue here, either. In general we have the best of the best, and they do amazing work. And still -- the Challenger blew up because of a simple o-ring. That, and people thinking "i've / we've got this."

Additionally, several times more people live near the plants now than when the safety studies and plans were originally made. Evacuation planning, communication, and transportation, sheltering resources, physical and human, and longer term / larger area planning all need thorough -- and public -- re-evaluation.

Design safety also assumes that plant operations are under control. A whacked operator could potentially cause problems that would make physical attack redundant. People are screened carefully and well, but we might possibly could miss one some day. And/or, one day some well screened and reasonable person could totally lose it.

If after 20 years of operations and technological developments, especially in communications and information processing, we truly can't find anything we can and should improve we probably need to find someone else to look for us.

An organization that struggled so hard over an ash pile, with its failure, denials, and minimizing may not be the best one to look at this for us. Or maybe they are. In any event the public will get -- and maybe deserve -- the thoughtful, careful, review which it demands.

More broadly, earthquake preparedness needs examination and action. With increased understanding of a higher hazard level should come increased resources devoted to at least identifying and perhaps reducing risks. We can't keep roads from falling off the mountains when it rains. We have many bridges not in the best shape, and a few tunnels. Liquefaction of soils at riverside chemical stations, water treatment/fresh water facilities, and potential for fires from broken gas lines, with broken water lines to prevent fighting them, all could be potential issues in some scenarios. What exactly have we done in response to this dawning realization of heightened threat?

Lastly, the Memphis area is severely threatened. A smaller event than the Japan quake could cause greater devastation there due to lack of physical seismic mitigation and unprepared populations. Chattanooga is a promising staging area for materials and personnel to respond, and might make a good sister city to Memphis for specific purposes if we planned to do so.

March 17, 2011 at 12:01 p.m.
rockman12 said...

To the Media, It is about time you stop trying to cause mass hysteria over every little thing that happens in the world. Also, there is no need to be a bunch of hypochondriac's every time something happens in the world. There is absolutely no comparison between what is happening in Japan and what "may happen" in Tennessee. Japan had a 9.0 earthquake and a major tsunami. While east TN can and does have earthquakes (largest to date was a 4.6 in Knoxville in 1973 as stated in the article) I am pretty sure that there will never be a tsunami in east TN. Stop trying to sensationalize the story and stop trying to connect it to Tennessee. They are two totally different situations.

March 17, 2011 at 5:04 p.m.
riverstronghold said...

i too am pretty sure that we will never have a tsunami in East Tennessee...but...

i wonder what we'd call it if an earthquake broke one of our dams on the Tennessee River...17 feet of water on Market Street in 24 hours if we lost Chickamauga...and that first wave would be a doozie...

...another one of those low-probability high-consequence events that we have all mostly been avoiding thinking about so successfully...

but it's a beautiful day and i'm going back to daydreaming now...

March 18, 2011 at 9:20 a.m.
drtdgr said...

The big thing to think about is the radiation getting in the water, they all set right on the river that you and i drink and shower and wash everything with. Thousands of people not just the ones within 12 or so miles look at it now ONE reactor in JAPAN and its setting off alarms at our nuclear plants, if its safe and no more than normal levels why do they not go off all day everyday?

March 31, 2011 at 2:03 p.m.
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