Nuclear Experts Explain Worst-Case Scenario at Fukushima Power Plant

[Frisbee]

By Steve Mirsky | March 12, 2011 | Scientific American Magazine


First came the earthquake, centered just off Japan's east coast, near Honshu. The added horror of the tsunami quickly followed. Now the world waits as emergency crews attempt to stop a core meltdown from occurring at the Fukushima Daichi nuclear reactor, already the site of an explosion of the reactor's housing structure.

At 1:30 P.M. Eastern Standard Time on March 12, American nuclear experts gathered for a call-in media briefing. Whereas various participants discussed the policy ramifications of the crisis, physicist Ken Bergeron provided most of the information regarding the actual damage to the reactor.

"Reactor analysts like to categorize potential reactor accidents into groups," said Bergeron, who did research on nuclear reactor accident simulation at Sandia National Laboratories in New Mexico. "And the type of accident that is occurring in Japan is known as a station blackout. It means loss of off-site AC power—power lines are down—and then a subsequent failure of emergency power on-site—the diesel generators. It is considered to be extremely unlikely, but the station blackout has been one of the great concerns for decades.


http://www.scientificamerican.com/article.cfm?id=fukushima-core&WT.mc_id=SA_DD_20110314

[aquart]

1. "Extremely unlikely", oh well.

[snagglepuss]

8. I believe you've misread his remark. Bergeron is extremely worried and says

this is uncharted territory. The "extremely unlikely" remark refers to how the industry has always pooh-poohed the possibility of station blackouts that lasted more than a couple of hours.


snip


Finally, Bergeron summed up the events so far: "Based on what we understand, the reactor has been shut down, in the sense that all of the control rods have been inserted—which means there's no longer a nuclear reaction. But what you have to worry about is the decay heat that's still in the core—that will last for many days.

"And to keep that decay heat of the uranium from melting the core, you have to keep water on it. And the conventional sources of water, the electricity that provides the power for pumps, have failed. So they are using some very unusual methods of getting water into the core, they're using steam-driven turbines—they're operating off of the steam generated by the reactor itself.

"But even that system requires electricity in the form of batteries. And the batteries aren't designed to last this long, so they have failed by now. So we don't know exactly how they're getting water to the core or if they're getting enough water to the core. We believe, because of the release of cesium, that the core has been exposed above the water level, at least for a portion of time, and has overheated. What we really need to know is how long can they keep that water flowing. And it needs to be days to keep the core from melting.

"The containment, I believe, is still intact. But if the core does melt, that insult will probably not be sustained and the containment vessel will fail. All this, if it were to occur, would take a matter of days. What's crucial is restoring AC power. They've got to get AC power back to the plant to be able to control it. And I'm sure they're working on it."

[aquart]

10. No, I got that.

"Extremely unlikely" is where any sane engineer or what ever should begin the fail safes, not end them.

[RUMMYisFROSTED]

2. -snip-

"The probability of this occurring is hard to calculate, primarily because of the possibility of what are called common-cause accidents, where the loss of off-site power and of on-site power are caused by the same thing. In this case it was the earthquake and tsunami. So we're in uncharted territory, we're in a land where probability says we shouldn't be. And we're hoping that all of the barriers to release of radioactivity will not fail."


Aka: A kiss and a prayer

[Kennah]

3. What? No baby wipe?

Before I kiss my own ass good bye ...

[RUMMYisFROSTED]

4. You can have a baby wipe if you want.

:shrug:

[villager]

5. "we're in a land where probability says we shouldn't be."

so much for the "but recurring terrible accidents aside, it's perfectly safe!" arguments...

[TomClash]

6. That was two days ago

I think the situation has worsened considerably.

[FourScore]

7. This article is 2 days old.

alot has happened since then.

[LiberalAndProud]

9. Final paragraph -- this guy is no nuclear Pollyana.

"The containment, I believe, is still intact. But if the core does melt, that insult will probably not be sustained and the containment vessel will fail. All this, if it were to occur, would take a matter of days. What's crucial is restoring AC power. They've got to get AC power back to the plant to be able to control it. And I'm sure they're working on it."


.