Nuclear Experts Explain Worst-Case Scenario at Fukushima Power Plant

http://www.scientificamerican.com/article.cfm?id=fukushima-core

by gommm • 15 years ago

94 77 15 years ago

scientificamerican.com

nazgulnarsil• 15 years ago

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

You, sir, need better advisors.

Ratfish2• 15 years ago

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

makmanalp• 15 years ago

Are you shitting me? This is Japan. Earthquakes happen very often and it's well known even by common people that they are closely followed by tsunamis. The fact that they didn't go together in any of the scenarios is mindblowing.

user97562• 15 years ago

Your comment broke my sarcasm detector.

According to Wikipedia: http://en.wikipedia.org/wiki/Tsunami#Generation_mechanisms

"The principal generation mechanism (or cause) of a tsunami is the displacement of a substantial volume of water or perturbation of the sea. This displacement of water is usually attributed to either earthquakes, landslides, volcanic eruptions, or more rarely by meteorites and nuclear tests."

Like the previous gentleman stated. Better advisers?

EDIT: spelling

wtn2• 15 years ago

Yes, this part of the article was incredibly hilarious.

starpilot2• 15 years ago

To be fair, the plant has operated through thirteen [1] previous earthquakes in Japan since its first reactor reached criticality in 1970 [2].

[1] http://en.wikipedia.org/wiki/List_of_earthquakes_in_Japan

[2] http://en.wikipedia.org/wiki/Fukushima_I_Nuclear_Power_Plant...

mbreese2• 15 years ago

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.

btmorex• 15 years ago

It's interesting. I've been reading the science subreddit and a lot of people are holding this up and some kind of engineering triumph, but to me it's an absolute engineering failure. Even if nothing bad happens from this point forward, two reactors were almost certainly destroyed and they'll have to sit dormant for a long while before they can be properly cleaned up. And as far as I can tell, there's still a very real risk of meltdown/containment vessel breach.

From my perspective, the root cause of what happened is that no one anticipated an event that would simultaneously cause failures in multiple systems (power loss, and destroy probably multiple redundant generators). It's easy to say after the fact that of course someone should have thought about that, in your words they should have had "better advisors", but I'm not sure how useful it is. All nuclear accidents that I'm familiar with were unanticipated. Can anyone really argue that they all just had bad advisors or engineers?

To me, this is the real argument against nuclear power and I say this as someone who still thinks that overall it's a good idea. How can we say something is truly safe when the accidents that did happen were not anticipated?

wtallis3• 15 years ago

I think it's too soon to say that this failure mode was never considered or even conceived of in the contingency planning for the power plant. If you have a source that says otherwise, please provide a link.

Keep in mind that this is currently estimated to be the biggest earthquake in the recorded history of Japan. It's completely unreasonable to expect stuff to totally not break when the big one hits. If some reactors are damaged beyond repair, that's understandable, as long as the radiation is contained well enough to keep the public safe. After all, good safety plans will always be willing to sacrifice expensive infrastructure in order to save lives.

Confusion2• 15 years ago

The scenario is slightly more complicated: power loss, loss of backup power sources and not being able to solve either of those two issues before the secondary backup power source, the batteries, ran out.

We're dealing with what is almost the worst case scenario the reactors are prepared for. That the reactors should be considered lost in such a situation is by design. How is it an engineering failure if everything operates as it was designed to?

  And as far as I can tell, there's still a very real risk
  of meltdown/containment vessel breach

There is, but that is the worst scenario that the reactor is prepared for: that the fuel rods melt through the bottom of the containment vessel. There is secondary containment with a huge heat sink down there. Damage will still be contained. But as they are now pumping seawater into the reactor, we won't get to test that bit of engineering.

dublinclontarf2• 15 years ago

I think that the greatest problem with nuclear is that we are still using reactors that were commisioned over 40 years ago!

Why the hell have they not been replaced with newer, safer, more effient reactor designs?

I'll tell you why, environmentalists. We need energy, we NEED electricity. Because of this need, and the fact that we can't build any new reactors thanks to the green lobby we are stuck with old reactors(which become riskier with age).

We cant turn them off because we need them and are not allowed to replace them.

The green movement, because of it's anti-nuclear stance is putting increasing number of lives at risk. If they were worried about safety they would make sure old plants are shut down and replaced with new ones. But they don't want this, they will only accept wind or solar.

blue1• 15 years ago

In other words, it's a magnificent example of Black Swan. Nassim Taleb will be happy.

squidsoup• 15 years ago

Building a nuclear power plant on the coastline of a subduction zone in a country with a long history of earthquakes and tsunamis does seem like a questionable idea.

JonoW• 15 years ago

Yeah I don't understand why these plants weren't built on the West coast, and why they weren't built on higher ground to mitigate against tsunamis.

sanxiyn• 15 years ago

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....

gommm• 15 years ago

You were linking to Fukushima Daini and not Daiichi http://www.tepco.co.jp/en/press/corp-com/release/11031305-e.... It doesn't mention that the AC power is restored

lispm6• 15 years ago

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....

extension• 15 years ago

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

user97562• 15 years ago

Everything?

adbge• 15 years ago

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

wtallis3• 15 years ago

Chernobyl was worse than just a meltdown. The graphite moderator caught fire and helped carry fallout into the atmosphere. This would not likely happen at Fukushima, as it is water-moderated, nor would the uranium fuel be able to catch fire as happened at Windscale, because modern reactors use uranium oxide instead of metallic uranium. In the event that containment is lost, there will still be contamination, but it probably couldn't be spread anywhere near as widely as the fallout from Chernobyl.

Ratfish2• 15 years ago

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?

cnvogel2• 15 years ago

That comparison is not correct.

The chernobyl plant exploded because of a instantaneous power excursion to many times the rated maximum, and it contained a huge amount of Graphite (=Coal!) which caused a fire that dispersed a lot of fine-grained core material.

The activity in the reactor core(s) in Japan right now should have decayed to a heat-output that is a few % of their rated power and, to make up some vivid comparison with the reality as we know it: The reactor core should look like what you get if a blacksmith puts glowing-hot iron (which in the reactor-case magically heats itself up constantly) in water, the resulting steam bubbles are what creates the increase in containment pressure.

Even if there would be another hydrogen induced explosion there's no chance that even a tiny fraction of the amount of radioactive material set free in Chernobyl would be released to the environment.

jessedhillon• 15 years ago

The plant itself would not be FUBAR'd. As it stands, that reactor will never be brought back online, but the other units at the plant can still generate power. (This is assuming that containment at reactor 1 succeeds and that it would be safe for humans to be working at the plant.)

This is what happened at Three Mile Island. Reactor 2 was taken offline and retired, but reactor 1 has continued operation. [1]

[1] http://en.wikipedia.org/wiki/Three_Mile_Island_accident#Curr...

ck2• 15 years ago

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

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

nicolas_t• 15 years ago

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...

wtn2• 15 years ago

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

davidw• 15 years ago

Depends on the prevailing winds, which I think generally go from west to east in the northern hemisphere, but no idea how things actually work in that area.

masklinn• 15 years ago

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

nostrademons• 15 years ago

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

Entlin• 15 years ago

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• 15 years ago

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.

rabidsnail• 15 years ago

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

Nuclear Experts Explain Worst-Case Scenario at Fukushima Power Plant

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