Were the Nuclear Protesters Right?
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Tigger
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ls99
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
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While the thread is in hijack mode: Did you hear the joke about British and Italian drivers?
The Italians drivers use their cars as an extension of their penis, the British instead of it.
The Italians drivers use their cars as an extension of their penis, the British instead of it.
(I'm Belgian)
Well, at as the Germans say - at least you're not Dutch - the bright yellow license plates and campers make them quite visible....let alone their driving ;-)
OK - you live in France - yes, what you describe can happen in Germany - however, one just needs to know where and when the open road is truly open....
Joke about the Italians drivers is not a joke - they are scary - what I like about the Germans is they are predictable - the Italians are not.....did I say they were scary
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I have driven in Italy and have noticed a difference between the city drivers and the autostrada drivers.
In the city, they are, for lack of a better word, insane. The traffic signs and signals are mere suggestions, not commandments. To the victor go the spoils, or more appropriately -- to the boldest goes the intersection.
On the autostrada, I find the Italian drivers to be far superior to American drivers. They pay attention to their driving. They don't talk on the phone, eat or apply their makeup while driving. They don't hog the left lane. They look well ahead, anticipate correctly and act accordingly.
In the city, they are, for lack of a better word, insane. The traffic signs and signals are mere suggestions, not commandments. To the victor go the spoils, or more appropriately -- to the boldest goes the intersection.
On the autostrada, I find the Italian drivers to be far superior to American drivers. They pay attention to their driving. They don't talk on the phone, eat or apply their makeup while driving. They don't hog the left lane. They look well ahead, anticipate correctly and act accordingly.
growing_older
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Merkel's government announced Monday that it will shut down all of the 17 nuclear power plants in Germany -- the world's fourth-largest economy and Europe's biggest -- by 2022. But Merkel, who holds a Ph.D. in physics, now says industrialized, technologically advanced Japan's "helplessness" in the face of the Fukushima disaster made her rethink the technology's risks.
Japanese nuclear regulators trusted that the reactors at the Fukushima Dai-ichi complex were safe from the worst waves an earthquake could muster based on a single-page memo from the plant operator nearly a decade ago. In the Dec. 19, 2001, document — one double-sized page obtained by The Associated Press under Japan's public records law — Tokyo Electric Power Co. rules out the possibility of a tsunami large enough to knock the plant offline and gives scant details to justify this conclusion, which proved to be wildly optimistic.
It looks like the problems are not purely technical, but also that mitigating very large risks by relying on human processes are also fallible. Germany, even with their reputation for engineering excellence, has apparently decided to refuse to take that risk in the future.
Japanese nuclear regulators trusted that the reactors at the Fukushima Dai-ichi complex were safe from the worst waves an earthquake could muster based on a single-page memo from the plant operator nearly a decade ago. In the Dec. 19, 2001, document — one double-sized page obtained by The Associated Press under Japan's public records law — Tokyo Electric Power Co. rules out the possibility of a tsunami large enough to knock the plant offline and gives scant details to justify this conclusion, which proved to be wildly optimistic.
It looks like the problems are not purely technical, but also that mitigating very large risks by relying on human processes are also fallible. Germany, even with their reputation for engineering excellence, has apparently decided to refuse to take that risk in the future.
Context: In Baden-Württemberg she got her a$$ handed to her in the election - a conservative area for 40+ years went liberal (her party lost). This happened right around the Fukushima issues. If you read the German press, they say they will do this by 2022, but they want to refuse any importation of energy from nation-states using nuclear and want to try to improve their other alternative energy sources. German energy prices are already quite expensive - very expensive (I live here). What with the bailout of Greece (the Landerbanks bought most of the crappy Greek bonds), Ireland, Portugal and possibly Spain being manily floated by Germany; what with Libyan oil not flowing as easily as before; what with Germans being very sensitive about inflation due to the Weimar Republic history; we'll see how much this stands. The group that lives here in Baden-Württemberg are notoriously cheap (Schwabian) and don't take too kindly to too much spending.
So, all politics is local - I believe Merkel did this to try and shore up her prospects for staying in office and not necessarily because of any safety issues......
M Paquette
Moderator Emeritus
Hmmm... There goes 20% of the German electrical production capacity. I wonder what it will be replaced with?
Heh. I know the usual suspects will declare the Germans will move to solar and wind power... in a country with the most energy-intensive industries in Europe. I eagerly await the results of moving Germany's metallurgical foundries, glassmaking, and industrial production facilities to solar and wind power.
(This will not actually happen, of course. A combination of coal-fired power plants, and import of power from France and the Czech Republic, from nuclear and coal power plants respectively, will be used.)
Wasn't Germany getting ready to cut its photovoltaic subsidies back in January or February?
M Paquette
Moderator Emeritus
Yup. First round of cuts are up to 15%, starting July.
UPDATE 1-Germany to cut solar subsidies by up to 15 pct | Reuters
There is consideration of a further 6% cut starting in March 2012 as part of the renewable energy law reform, tied to the nuclear energy phaseout.
Germany Mulling Further Cut To Solar Subsidies - Minister - WSJ.com
More coal plants are planned but are hitting assorted roadblocks, along with some conversions to natural gas. Gazprom, the Russian state gas monopoly that is Germany's biggest supplier, is doing a bit of a happy dance, I suspect.
Power imports from France and the Czech Republic have doubled since the March shutdowns, and exports to Switzerland and the Netherlands are roughly halved. The biggest headache appears to be in southern Germany, which has lost four nuclear power plants, with marginal grid capacity to import power from other regions.
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As we used to say back in the day -- "No nukes? Learn Russian and freeze in the dark."
I'd love to know what a roll of aluminum foil would cost if all the energy used to produce it came from renewable sources at present market rates.
At those prices, demand for aluminum foil might drop to zero...
Tigger
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A physicist about the risks: We 'came close to losing northern Japan' - CNN.com
Now this man, while an important physicist, does seem to love sensational language.
What I would like to know: is what he says wrong?
"Michio Kaku (加来 道雄 Kaku Michio?, born January 24, 1947) is an American physicist, the Henry Semat Professor of Theoretical Physics in the City College of New York of City University of New York, the co-founder of string field theory, and a "communicator" and "popularizer" of science."
http://en.wikipedia.org/wiki/Michio_kaku
Now this man, while an important physicist, does seem to love sensational language.
What I would like to know: is what he says wrong?
"Michio Kaku (加来 道雄 Kaku Michio?, born January 24, 1947) is an American physicist, the Henry Semat Professor of Theoretical Physics in the City College of New York of City University of New York, the co-founder of string field theory, and a "communicator" and "popularizer" of science."
http://en.wikipedia.org/wiki/Michio_kaku
ERD50
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
Some of it does seem sensationalized, others oddly the opposite. I wish it was a transcript, I went to listen again, but you get the ads, and then it advanced to the next segment and I gave up (finally did the original link again), but...
When he was describing the state of the nuclear material, I think he said it was like a bowl of granola with cream on it? That doesn't convey anything dangerous (though it clearly is!), so it was an odd choice of words (reminds me of the Stay-Puft Marshmallow man!). Even the interviewer seemed to try to get him to change tact there.
I had trouble accepting that the reason the company was reluctant to throw sea water on it was that they hoped to salvage anything. I can't imaging there is anything to salvage there.
I think the bigger questions is - would it have ever got to the point of a meltdown, really, or would they have seen that and pumped the sea water in before then? I don't know enough to even guess, but the fact is that it didn't go that far. Maybe that is sensationalizing this, maybe not if it really was close to getting much worse and there was no solution.
I got lost when he said there was a 100% meltdown, but then also says that if they didn't put seawater in it would have been worse. I guess the seawater kept it cool enough to contain, but I thought 100% meltdown meant melting through (down to China!)
What may well be sensationalizing (again, I can't know for sure), is that 20x number for radiation for children versus workers. Without some more info, that might just be some clever statistics munching, but maybe not. I assume he meant a normal exposure for workers, not the elevated numbers they are using for rescue workers. Hard to say.
It is tough to know enough to talk about what could have been. But again, to put this in perspective, how many deaths are traceable to this being a nuclear plant, versus the total deaths from this tragedy? And how many deaths would there be if those were some other type of power source? There were injuries/deaths at some oil refineries in Japan. And those other power sources have deaths associated with them even when nothing extraordinary like an earthquake happens:
India child labor: In India coal towns, many miners are children - latimes.com
I'm hoping that the next gen of nukes are smaller units, scattered across the grid. It's easier to make something small hold up to a disaster, and by spreading them around there is more redundancy and less loss to the grid.
-ERD50
M Paquette
Moderator Emeritus
Yes.
(This should produce an entertaining response. String theory != nuclear engineering.)
Northern Japan is pretty big. Three reactors, the old GE BWR models there, with the cores completely melted down (the industry slang is corium), won't sustain a fission reaction. The careful geometry needed to sustain a reaction is lost. The water, which slows neutrons to the point where they can be captured and sustain a fission reaction was lost.
The reaction products still continue to release decay heat. Without coolant that produces a meltdown. They might melt 5-7 cm of the reactor vessel inner lining. It will not be a nuclear explosion. It will be one heck of a cleanup mess within the containment, and as we saw, with a huge earthquake and tsunami exceeding the historical record and the design limits of the facility, the containment was damaged and there was some contamination outside the facility.
Dumping in seawater in the presence of fuel element failures was risky, and ran a risk of making the contamination problem worse. They had no instrumentation that could inform them that the core might be completely dry and in meltdown, though. They could detect fission products in the gases vented from the primary plant, which told them that they did have a fuel element failure. How big was unknown. The safest action in the face of that unknown state was to provide some form of emergency cooling. (BTW, the professor was wrong about that, too. Reactor Plant Manuals do describe the use of seawater as a coolant of last resort. It's very corrosive compared to the normal ultra-pure water, and as seen here spreads contamination from corroding the fuel charge.)
So, no nuclear explosion possible, some local contamination problems, and one heck of a mess to clean up on site. Nothing as hideous as Chernobyl, where there was no containment, and the actual fuel matrix (graphite) was on fire!
Tell me how that would lose Northern Japan. We Americans dropped two freaking nuclear bombs on Southern Japan, with horrendous results, but that didn't 'lose Southern Japan.'
If I wanted to look at something that darn near lost Northern Japan, I'd look at that tsunami. That was horrific, the sort of thing that gives civil engineers and disaster contingency planners nightmares.
I think the physicist was trying to say that the core melted down to rearrange itself into a critical mass of uranium that could have caused a nuclear explosion. That just doesn't happen, and thank goodness it doesn't or the terrorists would have made a mess of the world by now.
The reactor reality is that the uranium spews a lot of neutrons and heat while it's slagging down into a puddle at the bottom of the pressure vessel, and both are pretty much wasted by dissipating into the surrounding structure. The only way to put those neutrons to good fission use would be to somehow stop them, turn them around, and shoot them back into the uranium mass: like banking a raquetball off the side wall. Turns out that's accomplished with... water. So dumping a bunch of water onto a mass of uranium can still get pretty exciting if you do it wrong. But even if something critical (so to speak) happened, the whole mass would just heat up again and spread out some more to waste all those fission neutrons-- again.
Half the challenge of building a nuclear weapon is holding the critical mass together long enough to gain full effect from the fission neutrons. That only happens with a huge ball of pressure wrapped around the critical mass... like slamming one piece into another (the "gun" method) or compressing it with a dynamite explosion. In the case of the reactor, though, the best they could hope for would be a little more enthusiastic bubbling and spewing.
I'd sure love to hear his fellow physicists "reviewing" his hypothesis with him tomorrow in their coffee lounge... maybe this is why he's "popularizing" science instead of sticking to string theory.
The reactor reality is that the uranium spews a lot of neutrons and heat while it's slagging down into a puddle at the bottom of the pressure vessel, and both are pretty much wasted by dissipating into the surrounding structure. The only way to put those neutrons to good fission use would be to somehow stop them, turn them around, and shoot them back into the uranium mass: like banking a raquetball off the side wall. Turns out that's accomplished with... water. So dumping a bunch of water onto a mass of uranium can still get pretty exciting if you do it wrong. But even if something critical (so to speak) happened, the whole mass would just heat up again and spread out some more to waste all those fission neutrons-- again.
Half the challenge of building a nuclear weapon is holding the critical mass together long enough to gain full effect from the fission neutrons. That only happens with a huge ball of pressure wrapped around the critical mass... like slamming one piece into another (the "gun" method) or compressing it with a dynamite explosion. In the case of the reactor, though, the best they could hope for would be a little more enthusiastic bubbling and spewing.
I'd sure love to hear his fellow physicists "reviewing" his hypothesis with him tomorrow in their coffee lounge... maybe this is why he's "popularizing" science instead of sticking to string theory.
I'm glad I bit my tongue and waited for you to offer your answer first. You were much more restrained than I could've been. But spouse still got my eyeball-glazing dinnertime rant on the sad state of teaching reactor core physics in American public schools.
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Well done to both of you. I have nothing to add.
All this anti-nuclear fear-mongering seems ridiculous to me. What's the death toll from Fukishima so far? 3? Have we already forgotten the 11 souls who died on Deepwater Horizon just a year ago drilling for oil? Or the 29 miners who died in New Zealand just this past November, drilling for coal?
You simply cannot make a case against nuclear based on risk of death when you compare the death tolls for nuclear against oil or coal. Coal mining alone has literally killed thousands. It's pure emotional sensationalist fear-mongering.
You simply cannot make a case against nuclear based on risk of death when you compare the death tolls for nuclear against oil or coal. Coal mining alone has literally killed thousands. It's pure emotional sensationalist fear-mongering.
Hmm. My (admittedly layman's) understanding of nuclear physics is that in the absence of a neutron "brake" (eg., the control rods), the reaction will occur uncontrollably. In fact, even with the "brake" fully applied (the control rods fully inserted, absorbing a large percentage of stray neutrons), the nuclear fuel still generates an enormous amount of decay heat (7-10% of full capacity). So much so that they still need to be cooled by being completely immersed in water. And that water gets so hot that if it were not in a sealed pressure vessel, it would be boiling. In fact, in cases where the water level dropped and the water did in fact boil, even the tiny "voids" in the water (the bubbles) were enough to compromise the cooling effect of the water, and overheating occurred.
My point is that even with the control rods fully inserted, the reaction is still occurring. If the cooling agent (water) drops below the tops of the fuel rods, they overheat and melt, even when only producing "decay" heat. Thus, the reaction is "sustained," even after the geometry of the fuel rods disintegrates into a puddle of molten uranium.
As I understand it (and again, I'm no physicist), the only requirements for a sustained fission reaction is proximity/density of fuel, and absence of a neutron absorber. In a molten state, at the bottom of the reactor chamber, I would expect that both of these conditions would be met, and the reaction would indeed be sustained indefinitely.
I'm not sure what you mean here - you seem to be saying the water helped facilitate the fission reaction. My understanding is that the water actually discourages the nuclear reaction (by absorbing stray neutrons, preventing them from perpetuating more reactions), in addition to providing a cooling effect to avoid meltdown.
Sure, but I believe that that "decay heat" is itself a fission reaction, and in the absence of a cooling agent, will generate enough heat to reduce the fuel to a molten state.
To be fair, we're talking about dramatically different amounts of nuclear fuel here. The amount of raw nuclear material in the Hiroshima and Nagasaki bombs were about the size of a softball. The nuclear reactors in question contain much, much more fuel than that. Also, the bombs were only able to fission about 10% of their material before being dissipated too broadly for the reaction to continue. Left undisturbed, the reactor core material will continue to fission to a much higher percentage, unless we can extract it and separate it from itself.
Again, I'm not a physicist, everything I just wrote could be completely wrong.
GregLee
Thinks s/he gets paid by the post
Should I listen again? I didn't hear Kaku saying either directly or by implication that there would have been a nuclear explosion if seawater had not been used. He said that northern Japan might no longer have been habitable, and I took him to be referring to contamination.
GregLee
Thinks s/he gets paid by the post
That's a non sequitur. There can be risk of future death even when there have been no past deaths at all. In the Kaku discussion, we are considering hypothetically what might have happened had seawater had not been used to cool the troublesome reactors, and then, how likely in the future a private company would be to make what, in this case, turns out to have been the right decision.
M Paquette
Moderator Emeritus
Decay heat for a uranium or MOX reactor starts off at 6.6% of the previous sustained power level and drops off on an exponential function from there, to 1.5% after an hour, down to 0.2% after a week.
The decay curve function:
The fission chain reaction in these plants relies on thermal neutrons, neutrons produced by a fission of uranium or plutonium and slowed by a 'moderator' until they are moving so slowly that they can be caught and absorbed by another uranium or plutonium nucleus. There's a thing called the 'absorption cross-section' that indicates how readily the neutron is captured. Fast moving neutrons are not readily captured by the nuclear fuel in these reactors, and need to be slowed down.
In the Chernobyl plant, the moderator that slowed down neutrons was the graphite blocks the fuel was embedded in. That meant that unless the control rods could be fully inserted, the nuclear chain reaction would continue.
The water-moderated reactors, used for almost all nuclear power applications currently, rely on the water to slow the neutrons. With the water removed, the fast neutrons rapidly escape the reactor core and are absorbed in the surrounding neutron shield. (Typically a jacket including boron, which has a high absorption cross-section for neutrons but doesn't become radioactive.)
With the water removed, the nuclear chain reaction that supports continued fission stops.
The fission reaction is stopped at this point, as the water 'moderator' is removed. The control rods, metal alloys that absorb neutrons so as to damp the chain reaction, sill in the event of a core meltdown become part of that puddle in the bottom of the reactor vessal.
Proximity of fuel, and presence of a neutron flux sufficient to be absorbed and maintain a chain reaction, to be specific. Removing the moderator results in a loss of the neutron flux. The remaining fast neutron flux is insufficient to maintain a chain reaction. The core being collapsed and spread out over a reactor vessel bottom doesn't provide the needed proximity. (The fuel region looks like a disk, rather than a concentrated sphere, and is laced with neutron absorbing material from the control rods.)
Note that when water was eventually injected for cooling, it included a charge of boric acid. The boron atoms are potent neutron absorbers, 'poisoning' any neutron chain reaction. This is done to prevent the coolant from acting as a moderator for a partial meltdown configuration that might otherwise sustain a local chain reaction in part of the core.
There are reactors, such as the fast breeder design, that can maintain a chain reaction using a fast neutron flux. These use a different fuel mix, and special materials to reflect and concentrate the neutron flux in the core. A precise core geometry is also needed to keep the reaction going. The conditions to sustain this reaction simply do not exist in a thermal neutron reactor such as the Fukushima plant uses.
Pure water does facilitate the reaction, by slowing neutrons so that that can be absorbed by the fuel. Borated water, and to some extent ordinary sea water will damp the reaction by absorbing neutrons.
Decay heat is not a fission reaction. Decay heat comes from radioactive decay processes. Often the products of a fission reaction are two atoms, with roughly similar masses about half that of the fissioned atom. (That is, fission typically breaks a big atom in half, so we get two lighter atoms, and maybe a couple of free neutrons.) These fission product atoms often have an extra neutron or two in their nucleus compared to stable atoms of the same element. These atoms will 'decay' by emitting an electron from their nucleus, effectively trading a surplus neutron in for a proton and becoming more stable.
This process results in the release of heat, but it is not a chain reaction. As shown above, the decay heat from these secondary nuclear reactions drops off pretty quickly.
To be fair, we're talking about dramatically different amounts of nuclear fuel here. The amount of raw nuclear material in the Hiroshima and Nagasaki bombs were about the size of a softball. The nuclear reactors in question contain much, much more fuel than that. Also, the bombs were only able to fission about 10% of their material before being dissipated too broadly for the reaction to continue. Left undisturbed, the reactor core material will continue to fission to a much higher percentage, unless we can extract it and separate it from itself.
Again, I'm not a physicist, everything I just wrote could be completely wrong.
Actually, the reactor core contains a much more dilute form of the active nuclear material (Uranium-235) than a weapon, and as I have indicated above, the fission reaction stops in the absence of the moderator, or the insertion of control rods. (It also stops pretty quickly if one simply stops managing the reaction at all courtesy of a thing called the negative temperature coefficient of reactivity, but that is beyond the scope of the current topic.)
Oh, I do have a degree in physics, and taught reactor plant operation for two and a half years. I think I was fairly successful at it, as Nords and Gumby never did manage to vaporize central Idaho...
* Graphs, formulae, and links courtesy of Wikipedia. It's nice that someone else scanned in the texts and graphs.
Great. So now second-guessers won't be satisfied until we also consider what would happen if operators repeatedly do dumb things? This should be fun. I'd suggest that hydoelectric power won't do well under this new paradigm (unless we are prepared to vacate all
structures downstream of them right now). And when this new "analysis" tool is used to examine the commercial air transport industry, I think we'll have some changes coming. But, we'll still be able to travel across the country. Wagons, Ho!!
It's useful to consider alternate scenarios in order to find ways to mitigate risk (e.g. the operators at Fukushima could have used more sensor redundancy as a means to make better decisions). But there's clearly a limit as to how far we need to go down the "and then they make 22 consecutive incorrect decisions, what about that?"
