
Nuclear Experts Explain Worst-Case Scenario at Fukushima Power Plant - gommm
http://www.scientificamerican.com/article.cfm?id=fukushima-core
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nazgulnarsil
"we're in a land where probability says we shouldn't be."

You, sir, need better advisors.

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Ratfish
Go easy... "it was the earthquake and tsunami." they didn't go together in any
of the scenarios they ran.

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mbreese
The earthquake and tsunami weren't the coupled failures they were talking
about. It was the loss of external power and backup generators. This is what
they didn't expect, because it is hard to predict the probability of an event
big enough to trigger these two things failing at the same time.

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moe
Yes, it's indeed hard to predict an earthquake to take out the external power
and the subsequent tsunami to take out the backup generators _on a coastline
facility_.

(Note: This was sarcasm)

~~~
mbreese
How big of a tsunami was required? How big of a earthquake would be required
to generate such a wave? How much water would be needed to reach the facility?
How much to damage it? What about damaging backups?

Sarcasm aside, it is easy to predict that the facility would be at risk for an
earthquake/tsunami combo. The hard part is to predict how much of one to
prepapre for. Remember, even in this neck of the woods, the was a quake of
historic proportions.

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extension
In the case of a meltdown, what exactly is the damage?

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adbge
If a meltdown does occur, damage will depend on whether or not the reactor's
containment structure holds. In the case that it does hold, the plant itself
is FUBAR'd but, otherwise, there isn't significant cause for concern. This
would be analogous to the Three Mile Island accident -- in which a partial
meltdown occurred but was successfully contained.

If the containment structure is breached, the resulting fallout will be
comparable to that of the Chernobyl disaster which, like most Soviet reactors,
had _no containment structure whatsoever._ Wikipedia has a good article on the
effects of the Chernobyl disaster:
<http://en.wikipedia.org/wiki/Chernobyl_disaster_effects>

~~~
Ratfish
Are the containment domes intact in Japan? Edit: found this on IAEA site:
"Containment remains intact at Fukushima Daiichi Units 1, 2 and 3". It doesn't
even mention the 4th, but does say the explosion occurred outside unit 1s
primary containment dome. What does that mean? It's outer shield is wrecked?

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cnvogel
There's no containment dome.

<http://i.imgur.com/CckjP.jpg> (X)

The reactor is the red cylinder in the middle, the containment is the pear-
shaped cavity it sits in, closed on top with the yellow hood and connected to
that torus in the lowest-level which in case of an accident is supposed to
condense the steam back into water, thereby removing heat from the
containment.

The part that's exploded is the flimsy metal "hut" on top of the concrete
building.

(X) from another HN comment I can no longer find, sorry, no attribution for
who posted it initially

~~~
uvdiv
Original was

NRC: "Reactor Concepts Manual | Boiling Water Reactor (BWR) Systems"

<http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf>

Here's one with labels:

<http://i.imgur.com/Oj4kg.png>

Magdi Ragheb, "Containment Structures"

[https://netfiles.uiuc.edu/mragheb/www/NPRE%20457%20CSE%20462...](https://netfiles.uiuc.edu/mragheb/www/NPRE%20457%20CSE%20462%20Safety%20Analysis%20of%20Nuclear%20Reactor%20Systems/Containment%20Structures.pdf)

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Entlin
Why aren't all reactors mandated to keep a huge tank of emergency water at
some height, so that you only need to open some bulkhead and gravity will
ensure that the reactor gets cooled during the 7 or so days it takes to cool
down. No batteries, no diesel, no offsite power needed.

~~~
patrickgzill
This is actually the case for the design of some of the newer ALWR style
reactors.

There are 3 or more holes at different heights, designed so that the most
water flows in the early hours of cooling when the most cooling is needed,
then tapering off to 2 then 1 holes with the water flow lessening over time.

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nicolas_t
As someone who lives in Shanghai, 1850km away, I wonder if I should go a bit
further away as a precaution? During the Chernobyl accident the nuclear clouds
reached up to 2500 kms away from Chernobyl...

~~~
masklinn
Dominant winds go to the Pacific, even if there is meltdown _and_ containment
breach, California is more at risk than China is.

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nostrademons
As someone who lives in California, 8800km away, I wonder if I should go a bit
further away as a precaution...? ;-)

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codingthewheel
You should probably move away to avoid the air pollution in California.

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sanxiyn
Things are moving fast. TEPCO(Tokyo Electric Power Company) reported that they
have restored AC power to all units.

[http://www.tepco.co.jp/en/press/corp-
com/release/11031302-e....](http://www.tepco.co.jp/en/press/corp-
com/release/11031302-e.html)

~~~
lispm
No, that is not the plant where the main problems are.

They are talking about the Daiichi reactors here:

[http://www.tepco.co.jp/en/press/corp-
com/release/11031305-e....](http://www.tepco.co.jp/en/press/corp-
com/release/11031305-e.html)

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rabidsnail
Lesson: Don't build systems whose steady state is a catastrophe.

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ck2
Serious suggestion for our Japanese friends <http://nukalert.com>

added: looks like they have a page for Japan <http://nukalert.jp>

