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Chain Reactions Reignited At Fukushima

CmdrTaco posted more than 3 years ago | from the someone-explain-the-science dept.

Japan 234

mdsolar writes "Radioactive byproducts indicate that nuclear chain reactions must have been burning at the damaged nuclear reactors long after the disaster unfolded. Tetsuo Matsui at the University of Tokyo, says the limited data from Fukushima indicates that nuclear chain reactions must have reignited at Fuksuhima up to 12 days after the accident. Matsui says the evidence comes from measurements of the ratio of cesium-137 and iodine-131 at several points around the facility and in the seawater nearby."

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Tetsuuuuuoooooooo!!!! (2, Funny)

Anonymous Coward | more than 3 years ago | (#36071284)

That is all.

Re:Tetsuuuuuoooooooo!!!! (0)

RailGunner (554645) | more than 3 years ago | (#36071512)

Kaaaaaaneeeeeeetaaaaaaaa!

Re:Tetsuuuuuoooooooo!!!! (1)

the_hellspawn (908071) | more than 3 years ago | (#36071890)

Shoryuken! for the win.

Re:Tetsuuuuuoooooooo!!!! (1)

asylumx (881307) | more than 3 years ago | (#36072088)

*Matsui!*

I spit in your general direction!

Sensational! (0)

Anonymous Coward | more than 3 years ago | (#36071292)

Sensational!

Re:Sensational! (3, Informative)

repvik (96666) | more than 3 years ago | (#36071588)

Sensationalistic, atleast.
Did they restart? Techreview says "yes", Nature says "No":
http://blogs.nature.com/news/2011/05/analysis_suggests_fukushima_re_1.html [nature.com]

Re:Sensational! (1)

dirtyhippie (259852) | more than 3 years ago | (#36071856)

The "Nature" article is based on old data from the same researcher - Tetsuo Matsui. His latest thinking (presumably with more data) as shown in the technologyreview article is that reactions did restart.

Re:Sensational! (1)

repvik (96666) | more than 3 years ago | (#36071942)

They both reference the exact same study from 02. may: http://arxiv.org/abs/1105.0242 [arxiv.org]
Look at the end of the Techreview article:

Ref: arxiv.org/abs/1105.0242: Deciphering The Measured Ratios Of Iodine-131 To Cesium-137 At The Fukushima Reactors

And the beginning of the Nature article (*cough*blogpost*cough*):

A new analysis [arxiv.org] posted to the popular physics preprint server ArXiv.org suggests...

Re:Sensational! (1)

gilleain (1310105) | more than 3 years ago | (#36072082)

They both reference the exact same study from 02. may: http://arxiv.org/abs/1105.0242 [arxiv.org] Look at the end of the Techreview article:

Ref: arxiv.org/abs/1105.0242: Deciphering The Measured Ratios Of Iodine-131 To Cesium-137 At The Fukushima Reactors

And the beginning of the Nature article (*cough*blogpost*cough*):

A new analysis [arxiv.org] posted to the popular physics preprint server ArXiv.org suggests...

Furthermore, the Nature blogpost says clearly : " The work is not peer-reviewed, and like all speculation about Fukushima, it is based on sketchy and sometimes incorrect readings from the plant".

Not surprising: (3, Insightful)

Hartree (191324) | more than 3 years ago | (#36071298)

If you melt the fuel, you can get localized criticalities.

Without a moderator? (3, Interesting)

JSBiff (87824) | more than 3 years ago | (#36071360)

How, without a moderator?

My understanding is that LEU (low-enriched uranium) cannot achieve criticality without a moderator to slow down the neutrons?

Can anyone with a nuclear physics/engineering background give any explanation of how you can get a chain reaction without moderator?

Ok, they were cooling the reactor with water, and water is a moderator, but the water was also boronated, which should cancel the moderation property of water, shouldn't it?

Re:Without a moderator? (4, Informative)

Pumpkin Tuna (1033058) | more than 3 years ago | (#36071388)

In the first-12-day timeframe, the water wasn't boronated, it was just seawater.

Re:Without a moderator? (1)

JSBiff (87824) | more than 3 years ago | (#36071552)

I thought the news reports all said they boronated the seawater? Maybe I'm misremembering, but it seemed like that had been the case.

Re:Without a moderator? (5, Interesting)

Hartree (191324) | more than 3 years ago | (#36071828)

They didn't initially use seawater. They still had normal water in the pile and as far as I know hadn't triggered the systems to release boron in it.

These would be tiny little areas that would have an accelerated fission rate over just the fuel sitting in the elements. I'm not even sure you could truly call it a criticality in that it wouldn't be self sustaining. You'd get a momentary spike that would tail off. It's pretty insignificant as far as a source of heat or radiation compared to the decay heat and radiation from the fission products.

Thing is, using a mass spectrometer, you can measure truly tiny amounts of isotopes. You could expect some of the shorter life isotopes from just from occasionaly fissions without criticality. What this study was saying was that the observed ratio of isotopes was such that the particular researcher felt that it would require more than just the expected rate of fissions to get to that ratio.

That really doesn't surprise me. Nor is it terribly significant.

Re:Without a moderator? (1)

Vreejack (68778) | more than 3 years ago | (#36071646)

It isn't clear to me how sea water would affect a neutron flux, especially after it had boiled a bit. I don't think it is clear to anyone else, either, but certainly the lack of boron absorb stray neutrons and keep them out of the chain reaction makes criticality more likely.

Re:Without a moderator? (3, Insightful)

Dunbal (464142) | more than 3 years ago | (#36071580)

The scientific method in general terms consists of observation, then hypothesis, then designing an experiment to prove the hypothesis.

You are arguing "shouldn't it" and closing your mind to the understanding of the observed results - it doesn't matter what it "should" and "shouldn't" do under current models - what is important is what it actually did. Which means that either a) there were conditions that we don't know about that enabled the reaction or b) there are additional underlying scientific principles that we don't fully understand yet. My money would be on the former. However that the data do not agree with what you expected does not necessarily mean the data are wrong. It means you are wrong. Especially in a situation like this where I am sure that the data have been double and triple-checked.

If you stop trying to fit a square peg into a round hole, this will help you understand the universe better.

Re:Without a moderator? (3, Informative)

JSBiff (87824) | more than 3 years ago | (#36071714)

I'm not arguing anything. I asked a question. If (and that still hasn't been conclusively proven, but there is evidence to indicate a good possibility) that re-criticality occured, then the natural next question becomes *how* did this happen? How is my model flawed? There's absolutely nothing wrong with that.

I never, ever said in my post that the data is wrong, nor even implied that. I simply asked how this happened without a moderator. So, please climb down off that horse and join the rest of us.

Re:Without a moderator? (1)

JSBiff (87824) | more than 3 years ago | (#36071778)

I think another poster, perhaps, has a good explanation, btw - I thought the seawater they injected was boronated from the very start, but that may have been the result of either reading inaccurate media reports, or perhaps just confusion on my part as they apparently *did* boronate the water later, but perhaps not right from the start.

So, it seems the answer to my question may be as simple as, they injected "moderator" (in the form of non-boronated water) into the reactor, creating the conditions necessary for re-criticality. In other words, my model wasn't wrong, so much as my data (that G.I.G.O. thing I mentioned above - Garbage In, Garbage Out).

Re:Without a moderator? (0)

Anonymous Coward | more than 3 years ago | (#36071736)

Sheldon? Is that you???

Re:Without a moderator? (1)

Dunbal (464142) | more than 3 years ago | (#36071958)

No, but I can see how this can be confusing for you.

Re:Without a moderator? (2)

TheRaven64 (641858) | more than 3 years ago | (#36072000)

The scientific method in general terms consists of observation, then hypothesis, then designing an experiment to prove the hypothesis.

No! You never design an experiment to prove the hypothesis, you design an experiment to disprove it. If people try for a bit and fail, then the theory is accepted (which is not the same as being true).

Re:Without a moderator? (0)

Anonymous Coward | more than 3 years ago | (#36071596)

Maybe somebody in Japan had mod points.

(But which category to use? Flamebait? Insightful?

Re:Without a moderator? (3, Informative)

camperslo (704715) | more than 3 years ago | (#36071648)

Perhaps it has something to do with more fuel clumped more closely, like in a pile at the bottom of containment.

I believe it was unit 1 that had temperatures shoot up after a magnitude 7 aftershock. Given that the cooling situation hadn't changed, is there anything else but fuel shifting that would account for that?

Fuel that's piled up on the bottom may also get less of the inhibiting effects from either the boron control rods, or boron in solution.

Some believe that has has been some level of criticality in the unit 4 fuel pond based on the nature of the radiation coming off of that. Between some fuel damage from previous loss of coolant, possible use of coolant without boric acid for a time, and the world-wide industry practice of re-racking, it isn't surprising to have an issue with that. Re-racking is the practice of placing fuel assemblies at a closer spacing than original safety standards called for in or to be able to store more spent fuel.

Unit 3 has mixed oxide (MOX) fuel which includes plutonium. Since it gives off more neutrons when hit by them, it is harder to control. Reactors may need additional control rods and more boric acid in the coolant during normal operation to stay in control, and more yet when shut down. Unit 3 is potentially more troublesome to control if too much damaged fuel piles up on the the bottom. The environmental damage is also more apt to be longer term. As plutonium breaks down, the material produced actually gives off more radiation..

This blog has a fairly in depth look at MOX fuel

http://abundanthope.net/pages/Environment_Science_69/MOX-Fuel---Insanity-Part-1.shtml [abundanthope.net]

Re:Without a moderator? (1)

KenSeymour (81018) | more than 3 years ago | (#36071838)

These reactors have fuel rods, moderator rods, and control rods. A sub-critical reactor still generates heat.
Subtract the cooling water, melt some fuel and moderator, the geometry changes, then who knows.
I can't find what material is in the moderator rods, probably graphite.

Re:Without a moderator? (1)

JSBiff (87824) | more than 3 years ago | (#36071926)

Are there moderator rods? I was under the impression that Boiling Water Reactors just used the coolant water as the moderator, not rods?

I think the poster who said the emergency seawater coolant wasn't boronated probably has the answer. I had been (perhaps wrongly) under the impression that boron was being added to the seawater before injection specifically to keep the seawater from acting as a moderator.

If that was not the case, then there would have been moderator present, and if there were any holes/channels in the melted fuel mass where the seawater could penetrate, it could then start acting as a moderator, leading to re-criticality.

Re:Without a moderator? (4, Interesting)

camperslo (704715) | more than 3 years ago | (#36072110)

Chernobyl had grapite rods which added to the problems since they burned.

The Fukushima reactors have boron control rods.

Hopefully there won't be additional fuel damage. There apparently was some in unit 1 a week ago. Although they reported things as stable, they interruptted cooling for an hour or two to set up more permanent power connections. Later the temperature at the bottom of the reactor went from 110C to 143C. They increased the rate of adding water some. I think they're in a hurry to get better cooling with actual recycling, finned radiators, filtering, and good control of the boron levels going. They got air filtering going recently and made the building safe to enter. Last I heard they were about to remove some contaminated material and start checking the original circulating pump. It's good to see them finally making some progress. For a while it seemed like they were hopelessly kept away by the highly contominated water all over. Hopefully they'll get whatever cleans/processes that working well before they run out of space to put the water. Starting to recycle would really help that mess. It sounded like much of the water being pumped out was from turbine areas or tunnels nearby. Without actually sealing up the leak, whatever water does come out will tend to build up more and more contamination.
I believe they concluded that that mess is all coming from the unit 2 suppression tank. In the drawing it looks like a tire around the bottom (old GE Mark I design). But it's huge. A during-construction photo I saw with someone standing nearby made that suppression pool look maybe 30 feet tall. They'd have to pump in an awful lot of concrete or something to seal that leak...don't know if that;d work while wet and many tons of water and hour going through.

Re:Without a moderator? (2)

vlm (69642) | more than 3 years ago | (#36071924)

How, without a moderator?

My understanding is that LEU (low-enriched uranium) cannot achieve criticality without a moderator to slow down the neutrons?

Can anyone with a nuclear physics/engineering background give any explanation of how you can get a chain reaction without moderator?

I did about one year of nuke eng, after saying F Chem-Eng, then said F nuke eng and went EE. And then I never did any EE other than ham radio at home and have been a programmer / sysadmin since then. Yeah I was indecisive as a kid.

Anyway read the paragraph under the table at:

http://en.wikipedia.org/wiki/Critical_mass#Critical_mass_of_a_bare_sphere [wikipedia.org]

I cannot get a straight answer on how enriched the fuel was in the U plants. I believe the one reactor with MOX Pu was running about 5%.

I cannot get a straight answer on the core mass. As a gut level estimate a plant with that power output to have a sane thermal to mass ratio of about one ton per 10 MWt the core must have had about a hundred tons of U. Now that is U mass not mass of reactor vessel or mass of control rods and stuff, just "about a hundred tons of U". Also that ratio is from 20 year old memory and I don't know the MWt rating of the reactor, guessing about "1 GWt or so" It was a pretty standard GE BWR-3 installation, wasn't it? So whatever the standard BWR-3 core weight at any other site is probably close enough. Its all very confusing because there are/were like 6 reactors on site with 2 more planned and I can't be bothered to line up all the ducks in a row WRT which core we're all talking about. However, they are all well within an order of magnitude in size and other parameters, as far as I know.

Also I can't be bothered at this moment to look up the formula for minimum enrichment of "about a hundred tons" in optimal conditions. I'm guessing they specifically spec'd the enrichment to be low enough that if the whole core were melted into a perfect sphere surrounded by a perfect neutron reflector at the perfect low temperature (neutron doppler broadening) that it would still be non-critical, but like I said I dropped out of nuke-eng. Also I hated BWRs, all those transient calculations to figure out if the wetwell or drywell or whatever would pop like popcorn when you scram. Hated those things. Loved PWRs, so freaking simple and the turbine hall stays nice and clean. Bipolar transistor models or waveguide field equations, yeah that math sucks, its just fluid dynamics of a BWR during an "incident" suck even more.

Re:Without a moderator? (1)

Scrameustache (459504) | more than 3 years ago | (#36072054)

without a moderator?

Is the moderator something that would go away when everything melts, or is it something that would fall down in the pool of unevenly mixed material we're talking about? Because we're not talking about pure uranium, we're talking about a mess.

Ok, they were cooling the reactor with water, and water is a moderator, but the water was also boronated

They were dumping sea water scooped up from helicopters on the damn things, and you think they were stopping in mid-air to add some boron?

Monsters! (5, Funny)

CarsonChittom (2025388) | more than 3 years ago | (#36071304)

I feel bad for it, but I can't help but wish—just a little bit—that we'll get Godzilla out of this.

Re:Monsters! (0)

Anonymous Coward | more than 3 years ago | (#36071712)

I see that you were modded down, but please know if I had 5 I'd give them to you.

Another good reason to switch to Thorium (2, Informative)

Anonymous Coward | more than 3 years ago | (#36071314)

http://www.energyfromthorium.com

We have no one to blame but ourselves for any accident that happens when a safer, cleaner, more efficient, and cheaper nuclear fuel is readily available and already has most of the hard problems with its implementation worked out through several running prototypes.

Re:Another good reason to switch to Thorium (0)

Anonymous Coward | more than 3 years ago | (#36071400)

How can we build nuclear bombs from this shit?

Re:Another good reason to switch to Thorium (3, Insightful)

Eunuchswear (210685) | more than 3 years ago | (#36071720)

With difficulty, but it's possible.

As for any claim that Thorium is some magic pixy dust that prevents all forms of nuclear accident.... pah.

Re:Another good reason to switch to Thorium (-1)

erroneus (253617) | more than 3 years ago | (#36071412)

I'm sorry but you are wrong. Berillium Spheres are what is needed as the power source of the future.

Re:Another good reason to switch to Thorium (1)

gilleain (1310105) | more than 3 years ago | (#36071570)

I'm sorry but you are wrong. Berillium Spheres are what is needed as the power source of the future.

Beryllium

Re:Another good reason to switch to Thorium (1)

Dr.Bob,DC (2076168) | more than 3 years ago | (#36071608)

Sorry, but all this radiation is killing the planet.

Earth used to be a nice, hospitable place until the invention of radioactivity. What do we have to show for it? Cancer, mutations and vertebral subluxations.

Sure, high rates of subluxations are good for Doctors of Chiropractic, but they are killing people. Mark my words, in the future they will vilify the inventor of radiation while holding chiropractic up high as the saviour of mankind!

Re:Another good reason to switch to Thorium (1)

rwven (663186) | more than 3 years ago | (#36071678)

Invention of Radioactivity? Please tell me you're kidding.

Re:Another good reason to switch to Thorium (1)

Thud457 (234763) | more than 3 years ago | (#36071708)

You must not read at -1 much. Dr.Bob,DC [slashdot.org] is a somewhat amusing new theme troll that tries to derail any discussion into a flamewar over the merits of chiropracy.

Re:Another good reason to switch to Thorium (1)

rwven (663186) | more than 3 years ago | (#36071922)

Color me bashful. :-(

Re:Another good reason to switch to Thorium (1)

SilentStaid (1474575) | more than 3 years ago | (#36071740)

I'm pretty sure that Dr. Bob, DC [wikipedia.org] was joking.

Re:Another good reason to switch to Thorium (1)

Dr.Bob,DC (2076168) | more than 3 years ago | (#36071864)

I'll admit that I shouldn't have pushed chiropractic so strongly. It probably comes across as 'astroturfing'.
To your question: Madame Curry invented radioactivity with husband. It killed them both.

Re:Another good reason to switch to Thorium (1)

fuzznutz (789413) | more than 3 years ago | (#36071630)

Never give up! Never Surrender!

Re:Another good reason to switch to Thorium (0)

Anonymous Coward | more than 3 years ago | (#36071764)

I'm sorry but you are wrong. Dyson Spheres are what is needed as the power source of the future.

Gas effect (1)

Anonymous Coward | more than 3 years ago | (#36071328)

Has the Gas Effect contributed to the disaster? Its one of the least understood parts of nuclear reactions, fussion/fission and radiation, we need more funding for Gas Effect research.

Whack-a-mole (-1, Flamebait)

Sir_Kurt (92864) | more than 3 years ago | (#36071334)

More and more I see the attempt to design and operate Nuke plant as a very dangerous game of Whack-a-mole. Operator error, Wham, Design error, Wham, Maintenance failure, Wham. Earthquakes. Wham. Tsunamis, Wham. Terrorism, Wham,

and, what do we do with the waste for the next 20,000 years? Wham, Wham, Wham, Wham........

Miss one time, game over.

Kurt

Re:Whack-a-mole (4, Insightful)

Colonel Korn (1258968) | more than 3 years ago | (#36071362)

More and more I see the attempt to design and operate Nuke plant as a very dangerous game of Whack-a-mole. Operator error, Wham, Design error, Wham, Maintenance failure, Wham. Earthquakes. Wham. Tsunamis, Wham. Terrorism, Wham,

and, what do we do with the waste for the next 20,000 years? Wham, Wham, Wham, Wham........

Miss one time, game over.

Kurt

And operating a coal plant is akin to all the moles poked out of their holes and looking at you while you shrug and say "working as intended."

Re:Whack-a-mole (-1)

Anonymous Coward | more than 3 years ago | (#36071474)

And operating a coal plant is akin to all the moles poked out of their holes and looking at you while you shrug and say "working as intended."

Not too much wrong with coal, and if something does go wrong the effects are temporary and localized. Most of the coal is old biomass that used to be here in the biosphere. When nature started sequestering it in the ground in the form of coal the climate cooled and the deserts grew larger. I say it's time to bring the CO2 back. So what are these moles you speak of with coal?

Re:Whack-a-mole (2, Informative)

Anonymous Coward | more than 3 years ago | (#36071554)

The thousands of people coal plants kill every year due to air pollution and mining accidents? Must admit I'm struggling to find an absolute number, but this'll have to do:

http://nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html

Re:Whack-a-mole (0)

Anonymous Coward | more than 3 years ago | (#36071918)

Wow, FUD much? Solar and Wind, killing people near you!

Re:Whack-a-mole (0)

Anonymous Coward | more than 3 years ago | (#36071788)

Not too much wrong with coal, and if something does go wrong the effects are temporary and localized.

What, localized to planet Earth?

Re:Whack-a-mole (1, Insightful)

Anonymous Coward | more than 3 years ago | (#36071690)

False dichotomy much. And obviously intentionally too.

Both fossil fuels and nuclear fuels will end soon. And even if they wouldn't it's still just plain retarded backwards redneck shit technology.
We're in the motherfucking 21st century! Where's the geek in you?? We should only be using straight unprocessed energy from our fucking awesome giant fusion reactor in the sky by now!
We should be full circle in environment neutrality through balancing of all natural cycles that resulted from our actions by now!
Because that's how awesome I expect a humanity to be, that I consider worthy of existing!

Interestingly, nature agrees. And she always wins. She doesn't care if we wipe out the planet and pollute it to death. Something will survive and prosper.
But with all you idiots, it sure as hell won't be your version of humanity! :P

Re:Whack-a-mole (1)

Forty Two Tenfold (1134125) | more than 3 years ago | (#36071836)

And operating a coal plant is akin to all the moles poked out of their holes and looking at you while you shrug and say "working as intended."

And of course boiling water with nuclear and fossil fuels are the only two possible ways to produce electricity.

Re:Whack-a-mole (5, Informative)

jonescb (1888008) | more than 3 years ago | (#36071422)

There are reactor designs that currently exist that are more resilient to meltdowns. Most notably, thorium molten salt reactors, but there are only a handful of experimental reactors in existence. There is also the CANDU reactor primarily used and designed in Canada which is a uranium heavy water reactor.

I will agree with you that the ancient nuclear technology most reactors use today is not that safe, but more modern reactors have solved that issue. The only problem has been rolling out thorium and CANDU reactors.

And WRT your comment on terrorism, there's a video on Youtube I've seen that debunks the whole "flying a plane into a reactor" myth. Nuclear plants have concrete walls that are like 10 feet thick and the plane collapses on it self and does nothing to the wall.

Next time will be different (0)

Anonymous Coward | more than 3 years ago | (#36071490)

I've been watching the nuclear industry for a long long time, since they publicly announced come watch the test in Nevada next Monday, come to the viewing area at........ back in the 1950's in fact. They always have had newer better safer technology to replace the old dangerous crud.

Child of innocence wake up!

Re:Whack-a-mole (1)

Paul Jakma (2677) | more than 3 years ago | (#36071734)

Those walls appeared to be missing at Fukushima though. The reactor outer building seemed to be a relatively normal girder+concrete building. The reactor may have been in a reasonably thick, steel containment vessel, however the spent fuel pool wasn't protected by much. It was several stories up, near the top of a not particularly strongly reinforced, standardish building, and the top of the reactor - to minimise handling after unloading).

Re:Whack-a-mole (1)

Microlith (54737) | more than 3 years ago | (#36071968)

You obviously haven't looked at the design of the plant. There are 3 layers:
- The outer cosmetic steel box, to keep the weather out
- The inner concrete containment chamber
- The inner steel pressure vessel that houses the actual reaction

The concrete containment chamber is present in virtually every modern reactor, and every Western reactor for the precise reasons we see described today. Lack of a containment chamber is one of the reasons Chernobyl was infinitely worse than anything else, since when the steel pressure vessel exploded it was instantly exposed to the atmosphere.

Re:Whack-a-mole (1)

Paul Jakma (2677) | more than 3 years ago | (#36072120)

Ok, sorry, yes, the reactor in Fukushima is inside a concrete shell. However, the storage pool is not. Further, the Fukushima concrete shell was not designed for explosive or impact containment, because it seems it was broken apart by the hydrogen explosion in at least one of the reactor buildings (which I gather was outside of the concrete containment). Pictures taken from the air of the damaged buildings appear to show the top of the actual reactor pressure vessel (which was itself inside a steel containment vessel) exposed in at least reactor 4:

http://cryptome.org/eyeball/daiichi-npp8/daiichi-photos8.htm [cryptome.org]

I.e. the Fukushima design does NOT appear to have had any high-strength concrete containment, other than one designed for general structural support and low-pressure vapour/liquid containment.

Re:Whack-a-mole (-1, Troll)

Sir_Kurt (92864) | more than 3 years ago | (#36072012)

Sorry,

You did not address waste issue. Wham. Wham

Also, I think it is obvious from the design of the Japanese reactors, That you could certainly fly a plane into the secondary containment building where the spent fuel pools are and cause a very major release, and probably disable the primary cooling pumps to boot. Wham Wham Wham

And even with the best design you still have:
Possible design errors. Wham
or
Maintenance problem Wham

What else will pop up?

Kurt

Re:Whack-a-mole (3, Interesting)

Anonymous Coward | more than 3 years ago | (#36071432)

You can get rid of the waste whenever we are smart enough to switch to thorium fueled fluoride salt reactors which are inherently safer, much more efficient using only a fraction of a much more plentiful fuel to produce the same energy. The small amount of unusuable nuclear byproducts of a thorium reactor have much more manageable half-life of around 330 years. The useful byproducts include many things that are otherwise difficult to produce like the isotope of plutonium used to power deep space probes, bismuth-213 which is used in cancer treatments and has a 45-minute half life.

But to your point the best thing is the inherent safety, LFTRs (liquid fluoride thorium reactors) can be easily designed to passively shutdown rather than requiring active cooling inside the operating core which is the problem with all water cooled reactors which is all we have today. The funny thing is we have tested and proven this technology, we know it works, but the unsafe technology that produces weaponizable nuclear components and huge amounts of dangerous waste is so lucrative and entrenched that current nuclear players have no financial incentives to make the shift.

And the fact that a LFTR can reduce the waste we have produced from current nuclear technologies and turn it into more energy and more manageable waste.

Re:Whack-a-mole (1)

Joce640k (829181) | more than 3 years ago | (#36071466)

Terrorists can still take over 'planes? I thought they fixed the cabin doors...

(All that other TSA strip-search stuff is a waste of time...)

Re:Whack-a-mole (1)

Paul Jakma (2677) | more than 3 years ago | (#36071776)

Boeing designed the 787 without isolation between the network running the in-flight entertainment system (some of which allow PAX to plug in USB storage devices) and the network on which flight systems sit. So conceivably a passenger could have hijacked the plane without ever leaving their seat, e.g. with a crafted media file to exploit, say, ID3 parser bugs.

I presume Boeing have been forced to fix this, but I havn't checked...

Re:Whack-a-mole (1)

oiron (697563) | more than 3 years ago | (#36071936)

Wait... What? Terrorism or no, that would be a breathtakingly stupid move on their part; outside of bad movies, I can't imagine any design where someone would be able to hack an entertainment system and make the plane do a loop-the-loop... Have any reference to this?

[citation needed]

Re:Whack-a-mole (2)

gman003 (1693318) | more than 3 years ago | (#36071482)

As opposed to coal/oil/gas plants, where the game is Russian Roulette. They're going to kill people eventually from all the shit they pump out - the game is just hoping it isn't you.

Hydroelectric is a game of Jenga - lots of fun, but eventually something'll make the dam break, which is actually the most massively devastating type of power plant failure. The Johnstown Flood (caused by a dam failure) remains the deadliest disaster in US history. Estimates for a failure of the Three Gorges dam usually have 6-7 digit body counts.

Solar/Wind/Tidal/Geothermal/Fusion are all games of "how the hell can we make this actually work?". AFAIK, nobody has ever run an entire full-sized country, or even a significant fraction of a country, off any of those. It would be nice if we could, but so far, they are either not cost-effective, not able to produce enough to meet demand, or not even fully functional.

Re:Whack-a-mole (2)

SmilingBoy (686281) | more than 3 years ago | (#36071582)

Solar/Wind/Tidal/Geothermal/Fusion are all games of "how the hell can we make this actually work?". AFAIK, nobody has ever run an entire full-sized country, or even a significant fraction of a country, off any of those.

Iceland does - 66% geothermal.

But I agree that this is a very special case. Wind and (eventually) solar would be able to cover a large part of the energy needs of many countries - was it not for the tiny little problem of storage when it is winter, cloudy, and windless. Or just night.

Re:Whack-a-mole (2)

oiron (697563) | more than 3 years ago | (#36071964)

Know what? If we could use wind/solar/whatever during the day, and leave coal/oil/nuclear for just the night (and cloudy/windless days), that would still be a good 50% (give or take) reduction in dependence...

Re:Whack-a-mole (1)

gman003 (1693318) | more than 3 years ago | (#36072108)

A 50% reduction in dependence is not necessarily a 50% reduction in risk. A power plant is quite often still dangerous, even when off. Particularly nuclear - the most dangerous thing you can do to a nuclear reactor is try to shut it down. Chernobyl, Three Mile Island and even part of Fukushima (while the earthquake and tsunami did plenty of damage on their own, it was only when the power went out that the meltdown occured) were caused by attempts to shut down the reactors.

Re:Whack-a-mole (2)

Vectormatic (1759674) | more than 3 years ago | (#36071510)

Miss one time, game over.

Hardly, chernobyl and fukushima were about as miss as you are going to get, reactors dont blow up in the same way that a fusion bomb does.

Granted, chernobyl has a 30 KM exclusion zone, and fukushima will likely need a permanent exclusion zone as well, but it's hardly game over for the human race. It would be a good idea to build these things far away from large cities (having tokyo inside the exclusion zone would suck), but in the grand scheme of things, these kind of events are rather survivable

No disrespect to the victims of chernobyl or fukushima by the way, i dont mean to trivialise their plight, just saying that on a world scale, this isnt that big of a deal

Re:Whack-a-mole (0)

Anonymous Coward | more than 3 years ago | (#36071638)

Even with the Exclusion zone in Chernobyl, they still operated the plant into 2000

http://en.wikipedia.org/wiki/Chernobyl_Nuclear_Power_Plant

http://www.youtube.com/watch?v=6dN5T9eAVFg

Re:Whack-a-mole (1)

Microlith (54737) | more than 3 years ago | (#36072008)

fukushima will likely need a permanent exclusion zone as well

Doubtful. The lack of a core explosion means that the vast majority of long term radiological hazards and dangerous isotopes are still contained. The primary hazards in Chernobyl are high quantities of enriched uranium, plutonium, and strontium in the areas surrounding the plant.

We'll know more once the plant stops leaking material and the Iodine has had time to decay, but I suspect that the radiation will drop dramatically and that a minor cleanup effort will be needed in the areas surrounding the plant. Permanent evacuation? Unlikely.

Re:Whack-a-mole (0)

Anonymous Coward | more than 3 years ago | (#36072044)

We have one plant failure with core meltdown and significant radiation release every ten years, from a total that has been hovering around 400. That's not good by any count and it certainly puts a kink in the "too cheap to meter" meme. If nothing else, NPP failures are expensive on a scale that, indeed, only dams can replicate. Yet with a flood, you can come back a week later and start doing agriculture. Not so with the NPP. On a global scale (say, if we were trying to get 50% of all our electricity from nuclear), we cannot afford that.

Re:Whack-a-mole (0)

Anonymous Coward | more than 3 years ago | (#36071518)

I agree, but it is my understanding that there is a way for nuclear waste to be "burned" in the reactor greatly reducing it's half life. Is this correct?

Re:Whack-a-mole (1)

jonescb (1888008) | more than 3 years ago | (#36071692)

I don't know about reducing the half life, but there are reactors out there that you put the waste into and can burn up and get energy from, so you have less waste when it's done.

Re:Whack-a-mole (-1)

Anonymous Coward | more than 3 years ago | (#36071758)

It's called fast breeding, but here's the rub: it is breeding which causes the reaction to continue long after a shutdown has been initiated, and there's nothing you can do except keep cooling the fuel until the breeding stops. It is precisely this which is causing the problems in Fukushima at the moment.

Re:Whack-a-mole (2)

m.ducharme (1082683) | more than 3 years ago | (#36071766)

Yes, but it requires a different type of reactor. CANDU reactors can do it.

Re:Whack-a-mole (1)

Dunbal (464142) | more than 3 years ago | (#36071616)

Then by your definition, explain why we have already "missed" several times, and the "game" is far from over?

Re:Whack-a-mole (1)

Paul Jakma (2677) | more than 3 years ago | (#36071702)

It's still quite radioactive because there's still *lots* of energy in it - current reactors only extract a couple of % of the energy. At some stage in the future technology advance and the economics of uranium availability will make it viable to re-use this waste as fuel.

I.e. it's not waste, it's fuel we're going to use again in the future.

Re:Whack-a-mole (1)

Anonymous Coward | more than 3 years ago | (#36071792)

The waste? I think you meant the fuel for the next 20,000 years worth of reactors. It's not waste, it's a re-usable by-product.

But you already knew that, right?

Re:Whack-a-mole (2)

khallow (566160) | more than 3 years ago | (#36071962)

Fukushima shows that missing a mole isn't that serious and that your perception is incorrect.

and, what do we do with the waste for the next 20,000 years?

The part that is truly dangerous over that time span can be recycled. Just do that instead.

Re:Whack-a-mole (0)

Anonymous Coward | more than 3 years ago | (#36072090)

So in other words, nuclear energy is like almost everything else we've tried up to now.

Fossil fuels: oops, the CO2 got out into someone else's atmosphere, whether by operator error or even design.

Hydroelectric: this damn is working great, but the hippies and fishermen are protesting outside the gate.

Direct solar: no downside? Whaddya bet there's some horrible catch during the manufacturing, and some day hippies will be protesting outside the factory.

Well, duh. (2)

sribe (304414) | more than 3 years ago | (#36071344)

If the reactors had been successfully scram'd completely, heat from decay of by-products would have burned out in a very few days. As became obvious, that didn't happen.

Re:Well, duh. (0)

Anonymous Coward | more than 3 years ago | (#36071394)

Heat from decay products decreases rapidly (similar to but not exactly an asymptotic decrease), but never goes to completely zero, which is why spent fuel has to be kept submerged and cooled for years after it is removed from the reactor

Re:Well, duh. (2)

fritsd (924429) | more than 3 years ago | (#36071738)

And the fact that spent fuel pool #4 was almost full indicates that the most cost-effective and safe solution for 40 years of nuclear waste produced by TEPCO was to, um, keep a few more years worth of the spent fuel in that pool on the first floor of reactor building #4 until... you know, someone has a better idea later this century.

After the TEPCO directors are retired.

And moved to another prefecture on the other side of Japan.

Re:Well, duh. (5, Interesting)

Anonymous Coward | more than 3 years ago | (#36071408)

It did scram completely. The decay heat, which is 7% of 1000 MW boiled away all the water they lost the ability to pump, and then melted the zircalloy fuel rods into a pile of molten slag in places. That slag then has the geometrical configuration to do some more fission. Ironically, they may have had no problems if they didn't scram, as the reactor could then drive power to the cooling pumps, as opposed to relying on diesel generators.

Re:Well, duh. (2)

Dynetrekk (1607735) | more than 3 years ago | (#36071548)

Ironically, they may have had no problems if they didn't scram, as the reactor could then drive power to the cooling pumps, as opposed to relying on diesel generators.

Could be, but you are assuming that all the other stuff was intact after the tsunami: generators, pumps, cooling systems for the generators, etc. I'm guessing they were not, since they've had such huge issues getting water circulating after the tsunami.

Re:Well, duh. (1)

L4t3r4lu5 (1216702) | more than 3 years ago | (#36071760)

No, they were. The problem was that the diesel pumps were swamped by the tsunami, and therefore unavailable; The reactor itself was functioning despite a quake in excess of its designed tolerance. The SCRAM shut down the reactor, the diesel generators were unavailable... "Hilarity" ensued (with the portable generators having different connectors to those required for the pumps). With a short period of time before the coolant remaining boiled off, they had to get drastic and pumped in sea water. As water is a moderator, this allowed the reactions to start up again. It wasn't until 12 days after the earthquake that boronated water was used to mitigate the neutron moderation properties. It obviously wasn't enough, or there was some unboronated water trapped lower in the containment vessel where meltdown occured, so up on top all is rosey, underneath it ain't so good.

At least that's my take on the thing, having not thought about it for a few weeks.

It might be worse than that. . . (4, Insightful)

JSBiff (87824) | more than 3 years ago | (#36071668)

"The decay heat, which is 7% of 1000 MW"

IIRC, the reactors were 1000MW *electrical* output. Because of thermal efficiencies of steam generators of around 35%, I believe that means the thermal output of each reactor would have been about 1000/.35 ~= 2800 MW thermal energy.

So, instead of 7% of 1000MW = 70MW, I think you're looking at 7% of 2800 = 196MW.

That's a LOT of heat to get rid of, even if it is a small percentage of the 2800MW full output.

Re:Well, duh. (1)

Anonymous Coward | more than 3 years ago | (#36072118)

The decay heat drops very quickly over a few days before it starts to level off. You know those spent fuel pools that warmed up? Where do you think the power for that came from? Wiki has it at 0.2% after a week (of the 2.8GW thermal power of the reactor) that's 56MW of heat. So if it takes 4186 joules to raise the temperature of 1Kg of water by 1 degree Celsius, that is enough power to raise 13.4 tonnes (1000Kg) of water by 1 degree Celsius every second.

Chain Reaction! (2)

toygeek (473120) | more than 3 years ago | (#36071354)

I saw that movie. Not only does it end well but its got Neo in it. Don't worry. There is no spoon.

Seriously though... that's scary. It might not be Chernobyl but this has got to be the worst nuclear disaster of its type. Although since they're in Japan wouldn't it be called the South America Syndrome? (polar opposite of Fukushima is Chile)

SHUT UP SHUT UP SHUT UP! (0, Troll)

Thud457 (234763) | more than 3 years ago | (#36071456)

The fictional reactor they developed in the movie "Chain Reaction" as an cavitational sonofusion device. If you can't tell the difference between fission and fusion, please refrain from muddying the waters. And no matter what, never, under any circumstances remove the sands.

Re:SHUT UP SHUT UP SHUT UP! (1)

toygeek (473120) | more than 3 years ago | (#36072030)

The comment that was developed in the prior comment "Chain Reaction" was an attempt at humor. If you can't tell the difference between Humor and Serious, please refrain from watering the mudders. And no matter what, never, under any circumstances use your brain not your ass.

"So Achmed, what was the last thing to go through your mind?"

"My ass"

Power constraints? (1)

mdsolar (1045926) | more than 3 years ago | (#36071364)

I've looked through the paper this report is based on http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.0242v1.pdf [arxiv.org] and I don't see much discussion of the amount of power generated by the proposed post-shutdown criticality. It seems to me that standard operating power is assumed but I don't see how that could work without other signs such as a glowing reactor building.

Unit 3 explosion may have been Prompt Criticality (2)

edxwelch (600979) | more than 3 years ago | (#36071508)

As well as that there has been some speculation that the explosion in unit 3 was more than just a hydrogen explosion. If you compare the unit 1 and unit 3 explosions, you see the unit 3 was far larger in magintude, plus there is a flash right where the spent fuel pool is located. Also pieces of nuclear fuel rods were found 2 km from the site. Arnie Gundersen speculates that this was caused by a "prompt criticality" in the fuel pool, triggered by the hydrogen explosion. http://fairewinds.com/updates [fairewinds.com]

Re:Unit 3 explosion may have been Prompt Criticali (1)

mdsolar (1045926) | more than 3 years ago | (#36071658)

This seems like a stronger argument than the current paper.

Re:Unit 3 explosion may have been Prompt Criticali (0)

khallow (566160) | more than 3 years ago | (#36071726)

If that's true, then there should be some evidence for this assertion other than merely that the unit 3 explosion was bigger than the unit 1 explosion.

Age of Fuel (1)

SmilingBoy (686281) | more than 3 years ago | (#36071634)

One big issue I see is that the assumption is 7 to 9 months of fuel usage. In block 4, the fuel in the pond was probably significantly older.

Re:Age of Fuel (1)

mdsolar (1045926) | more than 3 years ago | (#36071698)

According to the paper, that is where the highest ratio I/Cs was found so this is the strongest case for a reaction.

good job (2)

sandrine (2131194) | more than 3 years ago | (#36071686)

There are reactor designs that currently exist that are more resilient to meltdowns.

Interesting. (1)

drolli (522659) | more than 3 years ago | (#36071706)

i have to say that the article is interesting, but as far as i understand the fuel in the different reactors is different and has undergone a quite different history.

The data and evaluation seems a little weak to me in that respect.

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