Tuesday, August 30, 2011

North Anna Nuke Plant: Quake May Have Exceeded Nuclear Plant's Safety Specs

But don't worry, says NRC, the plant is "less safe", not more dangerous.

From NBC News Washington (8/29/2011):

Despite being built to sustain more than the maximum expected shaking, last week’s earthquake may have exceeded the design parameters of the two nuclear reactors knocked offline.

That conclusion by Dominion Virginia Power and an independent government analysis prompted the Nuclear Regulatory Commission to send inspectors to the nuclear plant in Virginia.

The Dominion-operated North Anna Power Station 12 miles from the epicenter of the 5.8-magnitude quake in Louisa County temporarily lost power, but there was no significant damage to safety systems, according to the NRC. A low-level emergency was declared temporarily Tuesday after the incident.

The additional inspection should not be interpreted to mean the plant is less safe, the commission said Monday.

Nuclear power plants are built with margins of safety beyond the maximum expected shaking, and the damage detected so far at North Anna has been minimal.

(The article continues.)

In the meantime, Japan's Nuclear and Industrial Safety Agency now says there are 14 newly identified active faults near the nuclear facilities in Fukushima and Ibaraki Prefectures: 5 of them around TEPCO's Fukushima I and II Nuclear Power Plants, and 9 around the Tokai II Nuclear Power Plant operated by Japan Atomic Power Company and Tokai Fuel Reprocessing Facility operated by Japan Atomic Energy Agency. (From Kyodo News Japanese, 8/30/2011)

Don't worry, says NISA, they are all minor faults incapable of producing major earthquakes.


Anonymous said...

I doubt the NRC and their nuclear industry masters are going to allow anything but a glowing report. If the plants stays offline for an extended period it may have damage they are trying to quietly repair. On the other hand if they rush the plant back online to keep up appearances it may cause future problems. I keep seeing MSM articles referring to the plants seismic tolerance as 6.2 but there are two ratings 6.2 on soil and 5.9 on the solid rock portions of the plant. There are also acceleration factors that shouldn't be exceeded regardless of the earthquake's magnitude. From what I understand an outside lab is in the process of interpreting the G-force data.

Beyond Nuclear has an interesting report on America's many leaking nuclear power plants. Of course this report is pre-quake I wonder how leaky things are now?

"This “spaghetti bowl” of pipes is fabricated of a variety of materials from fiberglass to corrosion-susceptible materials like coated carbon steel and aluminum to more corrosion-resistant stainless steel. Because the pipes at today’s reactors are aging and corroding many are experiencing hidden, uncontrolled and unmonitored leaks of radioactive water that are contaminating underground water resources. Earthquakes have also caused underground pipes to leak. Leaking pipes have caused accidental radioactive releases both on and off nuclear power plant property."


Anonymous said...

"Don't worry, says NISA, they are all minor faults incapable of producing major earthquakes. "

A serious worry was reported a few weeks ago about the faults surrounding the Tsuruga nuclear power plant: http://www.asahi.com/national/update/0812/OSK201108120219.html

Anonymous said...

From a current Scoop.it article

"During the quake, 36 “scratch plates” at the facility recorded ground motion in three dimensions, said Richard Zuercher, a Dominion spokesman. Preliminary analysis of the plates performed by a seismologist contracted by Dominion showed “the plant may have exceeded design basis for ground-force acceleration,” Zuercher said.

(Notice Dominion doesn't name the seismologist they hired, I guess they don't want people asking inconvenient questions.)

The plant’s reactor containment buildings were built to withstand shaking equal to 12 percent of the force of gravity. Dominion said on the day of the quake that the plant would be safe up to a magnitude 6.2 earthquake. But the amount of shaking such a quake produces varies with distance to the epicentre, depth and the type of rock the quake occurs in.

(Both Dominion and the NRC have said "everything is OK" way before the G-force data has even been evaluated.)

Zuercher would not provide details on the amount of shaking revealed by the preliminary analysis. “We want to know for sure what we have,” he said, adding that Dominion would make available a fuller analysis of the shaking by the end of the week."

(I doubt Dominion will make any embarrassing announcements any time soon. If the plant received damage at 5.8 it would call into question all US NPP's I doubt the NRC will let that happen.)

With all the current earthquake activity it bring into mind the New Madrid fault line the USGS predicts a 10% chance of a magnitude 7+ and a 25%-40% chance of a mag 6 happening within the next 50 years.


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