Monday, July 16, 2007

The Japan Quake and the Kashiwazaki-Kariwa Nuclear Plant

By now, most of you have already heard about the earthquake that struck parts of Japan overnight, an event that killed 8 and injured 900. As the result of the quake, the Kashiwazaki-Kariwa Nuclear Plant experienced two separate incidents:

Four of the seven nuclear reactors at Tokyo Electric Power Co.'s Kashiwazaki-Kariwa nuclear power station, the world's largest nuclear power plant in terms of power output capacity, were operating or set to commence operation at the time of the earthquake and automatically shut down after sensing the strong quake.

But an electric transformer outside one of the reactors caught fire shortly after the quake. The fire was extinguished about two hours later. No radioactive leak has been detected.

It was the first fire at a nuclear plant to be caused by a quake and the Ministry of Economy, Trade and Industry is checking the cause, METI officials said.

TEPCO announced later in the day that water containing radioactive material leaked from one of three reactors that had suspended operations for regular checks and some of the water was released into the nearby Sea of Japan.

But the level of the radioactive material in the water was below the legal standard, the utility company said.
In response, NEI's Steve Kerekes passed along some notes to keep in mind as press reports continue to come out of Japan:

U.S. nuclear power plants are built with a defense-in-depth philosophy that uses multiple safety barriers and redundant, physically separated safety systems to assure that public health and safety is assured even in severe circumstances like hurricanes and earthquakes.

  • The three main protective barriers are the zirconium cladding on the ceramic pellets of uranium fuel; the reactor vessel and cooling system; and the containment structure that surrounds the reactor and other major components.
  • Examples of the robust design elements include: several feet of steel reinforced-concrete in the containment structures; stainless steel liners within the containment structure and within the many feet of concrete in the used fuel pools, below-grade foundations for the reactor core structure; and reinforced pipe and tank supports.

All U.S. nuclear plants are designed to withstand earthquakes of a magnitude that is equivalent to or greater than the largest known earthquake for region where it is being built. “Withstand” means that you retain the ability to safety shut down the plant without a release of radiation.

  • Given the seismic history in California, for example, plants in that state are built to withstand a higher level of seismic activity than plants in many other parts of the country. They are designed with events like that which occurred in Japan in mind.

Initial press reports out of Japan suggest that the level of radioactivity in the water that leaked from unit 6 of the power station is very small – not only at a level that would not jeopardize public health and safety but even below reportable regulatory limits.

  • We do not have details regarding the radionuclides involved in the leak, nor on the manner in which the leak occurred. We have been told by Tokyo Electric officials that the release of the water containing radioactive isotopes has been stopped.
More details are they become available. For more on the "defense in depth" philosophy that comes into play with nuclear plant safety, click here.

10 comments:

Anonymous said...

"All U.S. nuclear plants are designed to withstand earthquakes of a magnitude that is equivalent to or greater than the largest known earthquake for region where it is being built."

I believe that's the case with Japanese NPPs as well, including KK. However, the July 16 quake was larger than the design basis seismic event they'd anticipated.

Fred D. said...

The LA Times and other outlets are reporting some other issues... pipes dislodged, low-level waste barrels tipped over, a release into the atmosphere.

Are these indicators of design flaws, especially for what seems to be an earthquake-prone area? I will be very interested in seeing after-action or lessons learned reports.

Porgie Tirebiter, Royce Penstinger and Pinto Bean said...

First, the quake in Japan was higher in magnitude than the DB specks by which these reactors were designed and built. There is a very good chance that said quake has made all seven of these reactors unsound from and engineering stand point.

Secondly, NEI can try to mitigate reality all they want...this quake has shown nuclear reactors to be unsafe, and with each passing hour, the number of SIGNIFICANT issues at the world's largest reactor site continue to grow.

Smart money...dump your nuclear holdings before the bottom falls out of the market. If I had Exelon or Entergy stock right now (too name two) I'd be more than nervous.

David Bradish said...

Actually no. The best thing to do right now is to see what the total damage is. From the looks of things, it looks like the significant areas of the plants (i.e. the reactors) performed exactly how they were supposed to with no damage done to them.

You're forgetting these plants are designed for earthquakes. Give it a week and we'll see where we are at. You can't start jumping to conclusions. Bet you several of the reactors will begin restarting within two weeks.

Porgie Tirebiter, Royce Penstinger and Pinto Bean said...

Tokyo Electric Power has already admitted that the reactors were not built to withstand and earthquake of the magnitude experienced. The reactors themselves were built on basically very elaborate shock absorbers...this according to a welder who used to work for Underwater Welding of Essex, Ct. who actually did work on the reactors involved. Without significantly tests and examinantion, the long term viability of these shock absorbers cannot be ascertained, and it is murder to restart these seven reactors until said testing is completed.

Josh said...

Long name person, I think you have a problem with your definition of "unsafe".

I've posted a more detailed response on my blog.

Luke said...

Come off it.

How much radioactivity was actually released, and what maximum dose could this have resulted in to any member of the public?

What are the actual risks that the public has been exposed to as a result of this earthquake affecting the nuclear plant?

KenG said...

Can anyone confirm that these units actually have seismic isolation as stated above? I've extensively studied these projects and never seen this. I have a 2001 paper from Hitachi (K-6/K-7 designer) stating that they are studying seismic isolation for future units based on K-7. Perhaps the post above confuses snubbers with supports. Snubbers are easily inspected and requalified.

tgf said...

So what leaked? Heavy water? Cs-137? Sr-90? I-131? I haven't been able to find that info anywhere.

Luke said...

The water that leaked ultimately came from a spent fuel pool.

The 2 microcuries (just to re-iterate) of radioactivity in the water spill from the pool was probably a cocktail of reasonably long-lived fission products in trace amounts from the spent fuel rods.

Probably not I-131, because it's so short lived, it isn't significant in stored spent fuel, except where it's straight out of a recently operating reactor.

Fission products like Cs-137 might be a pretty representative guess.