Could it happen here?

Posted
Wednesday March 16, 2011

BRATTLEBORO -- With the eyes of the world fixed on the nuclear reactors in Japan, many people in the tri-state region are wondering if what is happening to the boiling water reactors at Fukushima could happen to the reactor at Vermont Yankee nuclear power plant in Vernon.

Vermont’s state geologist said a seismic event such as one that struck in Haddam, Conn., in 1791, or the one that struck Lake Ossipee, N.H., in 1940 or even the one that struck Canada last year, could happen tomorrow or 5,000 years from now.

Those earthquakes, which rated about 6.0 on the Richter Scale, were located deep within the earth and not on the surface like the one that struck Japan last week, said Laurence Becker, Vermont state geologist.

While you can see faults on maps of New England, he said, "Nobody has seen movement on these faults in events that occurred in historical times up to now."

Becker said New England is in a much lower seismic zone than Japan, which is at the edge of a tectonic plate, part of the "Ring of Fire," that follows the west coast of the Americas and the east coast of Asia.

In those areas, tectonic plates are colliding, grinding against and sliding over each other.

New England has had intraplate earthquakes and though they are very rare, when they happen they can cause a lot of damage.

"There is some potential, but it’s not as high," said Becker.

Most of the structure damage in New England would occur because buildings aren’t designed to resist the shaking of quakes, as they are on the West Coast.

"Brick isn’t tied into the structure of the building," said Becker. "That stuff can fall."

But Vermont Yankee was designed in the 1960s to withstand an earthquake of slightly above 6.0 on the Richter Scale, he said.

In actuality, said Becker, the plant was designed to withstand a certain amount of shaking -- called peak ground acceleration -- before going into safe shutdown.

While the Richter Scale measures the energy expended in an earthquake, peak ground acceleration measures the waves of energy radiating out from the epicenter, which cause the earth to shake.

Vermont Yankee was designed to withstand a peak acceleration of 14 percent of gravity before entering into safe shutdown, said Becker.

Larry Smith, spokesman for Vermont Yankee, said the power plant was built on bedrock to withstand "the most credible earthquake that has affected this region."

During the design phase of reactors built in the early 1970s, many natural disasters were taken into account, said Neil Sheehan, spokesman for the Nuclear Regulatory Commission.

Those included earthquakes, hurricanes, tornadoes, lightning strikes and wind storms.

"They were required to look at a historic seismic event -- the most severe earthquake -- and to put in safety margins above that," said Sheehan.

Most recently, when dry cask storage of spent nuclear fuel was proposed for Yankee, the state reviewed the chances of an earthquake and how it might affect the casks.

The state concluded the possibility of a quake was minimal and authorized the storage of nuclear waste at the site.

Smith said Vermont Yankee has a number of redundant systems to insure the plant’s reactor core continues to be cooled in a seismic event.

"There is redundancy here," he said.

It has three diesel generators -- two inside the turbine building and one outside -- which each have enough fuel to operate for seven days

The power plant also has a tie-in to the Vernon Dam, which automatically sends power to the plant if no other sources of electricity are available.

As with the Fukushima reactors, Vermont Yankee has batteries that are good for eight hours before needing a recharge, said Smith.

In addition, the plant’s high-pressure cooling system and reactor core isolation cooling, which pump water into the reactor, can be steam driven.

Bob Audette can be reached at raudette@reformer.com, or at 802-254-2311, ext. 160.


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