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Nuclear fuel has melted through base of Fukushima plant

The findings of the report, which has been given to the International Atomic Energy Agency, were revealed by the Yomiuri newspaper, which described a "melt-through" as being "far worse than a core meltdown" and "the worst possibility in a nuclear accident."

If I'm understanding this correctly, there is a sustained nuclear reaction heading for the water table.  So ... we're looking at a high probability of a steam explosion?

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre

by ATinNM on Sat Jun 11th, 2011 at 11:00:03 PM EST
It may be possible that it turns into a large, continuous steam vent, as from a geyser, either after or instead of an explosion. But this steam will contain serious levels of radioactivity, and this possibly at a time when the winds will be blowing from the north east.
One down through the concrete and two more to go?

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sun Jun 12th, 2011 at 12:32:15 AM EST
[ Parent ]
If a steam explosion were to happen--but it may not happen--much more fallout would be spewed and scattered than has been already.  

The entire northern hemisphere would begin seeing elevated health problems.  

We would quit worrying about Japan.  We would be worrying about ourselves.  

It is really important that they avoid this.  

The Fates are kind.

by Gaianne on Sun Jun 12th, 2011 at 12:36:31 AM EST
[ Parent ]
If a steam explosion were to happen--but it may not happen--much more fallout would be spewed and scattered than has been already.

The entire northern hemisphere would begin seeing elevated health problems.

Sanity check:
A cubic meter of Uranium weighs 20 tons. 20 tons of Uranium scattered evenly across the Northern Hemisphere would amount to 0.3 g per square km, or 300 nanogram per square meter.

Conclusion:
You need a lot of cubic meters of corium to get blown into the stratosphere to get beyond a rounding error in either the gamma background or total heavy metal exposure. (Any corium that remains in the troposphere will precipitate out within the first thousand km. Sucks to be downwind of that plume, but not something that will directly affect the entire Northern Hemisphere.)

- Jake

Friends come and go. Enemies accumulate.

by JakeS (JangoSierra 'at' gmail 'dot' com) on Sun Jun 12th, 2011 at 07:11:39 AM EST
[ Parent ]
is already fated to see a statistically measurable increase in cancer.  

Multiply by ten or hundred or whatever, and our health concerns will extend to the east coast and even Europe.  

Don't get me wrong:  This is not how humans will go extinct.  

But a cancer epidemic, yes.  Also birth defects.  

And, yes, I think it matters.  

The Fates are kind.

by Gaianne on Sun Jun 12th, 2011 at 07:23:59 AM EST
[ Parent ]


Friends come and go. Enemies accumulate.
by JakeS (JangoSierra 'at' gmail 'dot' com) on Sun Jun 12th, 2011 at 08:25:47 AM EST
[ Parent ]
Jake, why the focus on uranium? What am i missing?


"Life shrinks or expands in proportion to one's courage." - Ana´s Nin
by Crazy Horse on Sun Jun 12th, 2011 at 10:33:16 AM EST
[ Parent ]
You're not missing anything, but I wanted a ballpark figure. You can get a better ballpark figure by taking account of the composition of corium, but when you're looking at corium levels in fractions of microgram per square meter, I'm not sure that's the most productive use of your time.

- Jake

Friends come and go. Enemies accumulate.

by JakeS (JangoSierra 'at' gmail 'dot' com) on Sun Jun 12th, 2011 at 12:46:20 PM EST
[ Parent ]
At least 97% of the corium would be Uranium, except in the case of MOX fuel which can be 7% Plutonium.

Economics is politics by other means
by Migeru (migeru at eurotrib dot com) on Sun Jun 12th, 2011 at 06:27:24 PM EST
[ Parent ]
Eh?

Potentially there's quite a bit more than one cubic meter of active corium and spent fuel at Fukushima. There are around 1000 rods at each reactor - either active or in the SF pool - and each rod holds around 200kg of uranium.

So that's around 200 tonnes. Per reactor.

If one goes, the chances of the others surviving without maintenance are not high.

And the corium includes active fission products that are both lighter and more immediately problematic than uranium.

If just one reactor goes boom, that's immensely bad news for the immediate area. But if the spike in infant mortality in the North West is confirmed, there are already obvious health effects from the current slow burn.

But I think an explosive encounter with the water table would immediately become more of a political and military problem than a scientific one.

Effectively you'd have a cloud of death, which would either rain on the US west coast or would drift east over China and Russia.

The US would shrug and let its people fry.

Russia and China, not so much.

by ThatBritGuy (thatbritguy (at) googlemail.com) on Sun Jun 12th, 2011 at 09:51:20 AM EST
[ Parent ]
Thank you for the link.

After reading Crazy Horse's reference to the study I assumed the increase was two or three - or maybe five - percent increase.  A thirty-five percent increase is shocking.  

Granted it's a first study.  Granted the findings need to be verified.  It's still (barely) possible the increase is just one of those things that happens.  However, the math is as straight-forward as it can be and the findings are consistent with previous episodes.  I rather pride myself on my skepticism and I have a general unwillingness to theorize ahead of data but this is altogether too much like the early studies of the Navaho uranium mine tailings for me not to think the authors have got something.

Gawd, what a mess.


She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre

by ATinNM on Sun Jun 12th, 2011 at 11:24:06 AM EST
[ Parent ]
So Potentially there's quite a bit more than one cubic meter of active corium and spent fuel at Fukushima. There are around 1000 rods at each reactor - either active or in the SF pool - and each rod holds around 200kg of uranium.

So that's around 200 tonnes. Per reactor.

OK, that'd give you 3 microgram per square meter per reactor that goes boom, if spread evenly across the planet. The potassium background would still be a much bigger problem for anybody not immediately downwind of the plume.

For the people who are downwind of the plume... well, that's a different story, and one where I'm not qualified to come up with even ballpark figures.

Though personally I'd be a lot more worried about Japan having to filter its drinking water for radioactive heavy metals essentially forever.

- Jake

Friends come and go. Enemies accumulate.

by JakeS (JangoSierra 'at' gmail 'dot' com) on Sun Jun 12th, 2011 at 12:55:50 PM EST
[ Parent ]
How much of the caesium is still in the reactor?

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 01:57:54 PM EST
[ Parent ]
It won't spread evenly across the planet. It will collect in clusters and hotspots which will never be mapped accurately, and it will make its way into the food chain, where it will be concentrated and eventually eaten, and where the Cesium and other long-lived decay products elements will eventually cause cancers, infant mortality and birth defects.

It won't kill everyone, but how many birth defects do you need before an area becomes marginally habitable?

People could move back to Chernobyl tomorrow. Most of them wouldn't die for years or decades.

That doesn't mean the Hot Zone is safe, or an ignorable thing.

by ThatBritGuy (thatbritguy (at) googlemail.com) on Sun Jun 12th, 2011 at 03:39:51 PM EST
[ Parent ]
Would uranium be our primary concern?

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 10:13:03 AM EST
[ Parent ]
I'd wonder whether plutonium would be ~ the mixed uranium/plutonium fuel rods are just the start of that, since plutonium is a reasonably common reactor product for LWR ~ indeed, that is part of the argument for the thorium fuel cycle, that if its seeded by uranium, plutonium is several additional steps as a reactor product so far less common.

A major blow up now of the kind speculated above would be very bad news for those in the plume, but in a world where we are playing around with possible 5°C global warming, probably 2°C global warming, and genetically engineering crops so that we can pump fields with so much poison that it kills off honeybees ~ its seems like the stratospheric fallout would be in the "lets kill of thousands and make life miserable for thousands more" level of bad that we have permitted consistently over the past half century.


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

by BruceMcF (agila61 at netscape dot net) on Sun Jun 12th, 2011 at 12:17:58 PM EST
[ Parent ]
From the report linked by ceebs downthread, on the No. 1 reactor, results of the analysis run by TEPCO:

...almost all the
noble gases were vented out into the environment. The ratio of released radioactive iodine to the total iodine contained (hereinafter referred to as release ratio) was IV-44 approximately 1% from the analysis result, and the release of other nuclides was less than 1%.

Results of the re-run by NISA (which found that the pressure vessel was damaged 5 hours rather than 17 hours after the accident, though the timeline of the fuel rod meltdown was the same):

As for release ratio of radioactive nuclides, the analytical results show about 1% of tellurium, about 0.7% of iodine and about 0.3% of cesium.

So further away from Fukushima, I wouldn't worry about the heavy metals, but would worry about the lots of Iodine (even ater decay) and caesium still there.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Jun 12th, 2011 at 03:54:25 PM EST
[ Parent ]
They're saying
The nuclear fuel in three of the reactors at the Fukushima Dai-Ichi nuclear plant has melted through the base of the pressure vessels and is pooling in the outer containment vessels, according to a report by the Japanese government.

...

Melt-downs of the fuel in the No. 2 and No. 3 reactors followed over the following days with the molten fuel collecting at the bottom of the pressure vessels before burning through and into the external steel containment vessels.

The fuel appears to be stable at present as it is being cooled by water pumped into the vessels, although it will complicate the emergency recovery plan put forward by the government.

The problem with this is that concrete decays at a lower temperature than that at which the steel of the containment vessel melts. So "the fuel is pooling in the outer vessels but appears to be stable" seems reassiring until it doesn't.

If one believes that the people in charge know more than they are letting on and are "managing the information flow" this might mean that they know the corium will also breach the outer containment vessel, or that it has already done so.

If the melt is able to burn through the concrete containment it must be above 1000C - what are the odds that the melt will cool down enough before reaching the water table?

And, just a hundred meters or so from the sea, how deep is the water table?

Economics is politics by other means

by Migeru (migeru at eurotrib dot com) on Sun Jun 12th, 2011 at 08:01:40 AM EST
[ Parent ]
The one point I don't get is "the external steel containment vessels". Aren't the pressure vessels steel and the containment vessel concrete? Or does the containment vessel have a steel layer?

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 10:10:56 AM EST
[ Parent ]
Maybe they mean "steel containment" external to the "zirconium casing" of the fuel rods which we were being told was melting or burning back in March...

Economics is politics by other means
by Migeru (migeru at eurotrib dot com) on Sun Jun 12th, 2011 at 10:53:19 AM EST
[ Parent ]
If I'm understanding this correctly, there is a sustained nuclear reaction heading for the water table.

Is it? There aren't many useful details in what I read so far, I'm missing clarity on issues such as: what exactly (what kinds of physical evidence and/or simulation) is the basis of the new meltdown timeline estimate, what is the amount (even just the order of magnitude) of fuel that melted down and collected at the bottom of the pressure vessel, what is the amount of corium that escaped the pressure vessel after melting it through, what is the current estimated temperature of both pools? For your worse-of-the-worst scenario, material equivalent of that in multiple fuel rods would have had to collect in a single pool. If it is in smaller amounts, then just decay heat will have kept it hot until the flooding of the core, but there was no chain reaction.

Either way, if the bottoms of the cores got dry and there was lots of corium on it, they might have been lucky not to produce a major team explosion during the flooding.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Jun 12th, 2011 at 11:18:54 AM EST
[ Parent ]
The on-going back story to this is lying-by-omission of TEPCO and the Japanese and, perhaps, other governments.  

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre
by ATinNM on Sun Jun 12th, 2011 at 11:39:19 AM EST
[ Parent ]
There is so much spin and speculation overdrive about Fukushima that I'm having trouble separating on-going back stories and on-going framings. What lie by omission are you suspecting here?

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 02:01:48 PM EST
[ Parent ]
Thinking of what we learned this week: TEPCO was pissing around trying to save their nukes when the things were about to go ker-blooey and rain radioactive material all over northern Japan.


She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre
by ATinNM on Sun Jun 12th, 2011 at 03:18:14 PM EST
[ Parent ]
What have we learned this week?

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 03:55:18 PM EST
[ Parent ]
What I wrote.

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre
by ATinNM on Sun Jun 12th, 2011 at 04:58:02 PM EST
[ Parent ]
Could you be more specific? I don't see it in what you wrote in this thread, duh.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 05:04:44 PM EST
[ Parent ]
See this comment

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre
by ATinNM on Sun Jun 12th, 2011 at 05:37:54 PM EST
[ Parent ]
Well I replied to that one there (though I confounded the issues of venting and flooding), and found more contrary detail in the report ceebs linked to downthread. I think putting the blame on TEPCO's financial approach is more in place in connection with the issues of earthquake & tsunami resistance and employment policy.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Mon Jun 13th, 2011 at 04:44:13 AM EST
[ Parent ]
Reading the cited article it seems that they are confirming that three steel reactor containment vessels have been breached and that reactor fuel is pooling on the concrete floors of the concrete containment vessels. Absent a floor geometry specifically designed to disperse the corium into sub-critical packages it is likely to all be in one fairly small area under the hole melted through the steel. If this is the case could there be enough corium and it could be thick enough that criticality continues? If so, could not the top of the corium pool be cooled by water, which is boiling, while the bottom continues to react with the concrete?

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sun Jun 12th, 2011 at 12:53:55 PM EST
[ Parent ]
And would not the immanence of corium exiting the entire containment structure be the time to admit that corium has exited the reactor pressure vessel? That seems to be the pattern.

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sun Jun 12th, 2011 at 12:55:36 PM EST
[ Parent ]
Do I correctly recall that there were reports of having flooded the concrete containment structure around RPV #1? I recall some expressing concern that the added water could compromise the seismic integrity of the structure, (which may already be compromised, resulting in some of the leaks of radioactive sea water.) If that is so, would it not be likely that they have flooded all three concrete containment structures at least up to the level of the bottom of the RPV? And if they kept injecting water into the RPV until corium melted through the bottom, would there be a dramatic steam signature to signal that event?

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Sun Jun 12th, 2011 at 01:25:06 PM EST
[ Parent ]
There was much discussion about earthquake damage, added to the weight of water of water packed inside. TEPCO appeared worried that the weight of water was causing damage to the structure of reactors 1 and 3, so decreased the amount of cooling water at one point

Any idiot can face a crisis - it's day to day living that wears you out.
by ceebs (ceebs (at) eurotrib (dot) com) on Sun Jun 12th, 2011 at 02:17:46 PM EST
[ Parent ]
Reminds me: there is no info on the size and number of the hole or holes, either.

*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 02:03:35 PM EST
[ Parent ]

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