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Germany shuts down seven reactors‎ because of Fokushima

reuters.com

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Re: Germany shuts down seven reactors‎ because of Fokushima

#71

Post by asharp »

xlpz wrote: post #25
thematt wrote: post #19

Earlier quoted context omitted.

Why? I actually think the events of the past week prove it's safety. Let put it in perspective: a 40 year old nuclear reactor gets hit by a 9 magnitude earthquake, then slammed with 20 ft. tall swell of water, followed by an explosion due to the buildup of hydrogen gas that blows off the roof of the building, and after all that the core was still mostly intact and contained. That seems like an amazingly positive resu…

What potentially devastating consequences would there be if instead of a nuclear plant a windmill had been hit by an earthquake, tsunami and explosion? I honestly fail to be impressed by this kind of reasoning about nuclear energy's safety. Disclaimer: I still think fission power might be better in the long run than coal power (catastrophic global warming is worse than any nuclear disaster), but I'd rather do without…

What potentially devastating consequences would there be if an oil rig had been hit by an earthquake, tsunami and explosion? Also consider the size of an oil rig(s) that would need to provide the same amount of energy.

Similarly, what would the consequences be if a chemical plant producing say pesticides were to undergo the same fate? Simply because a process may be dangerous doesn't mean that it can't be safely harnessed into the service of man.

Re: Germany shuts down seven reactors‎ because of Fokushima

#72

Post by nopassrecover »

wladimir wrote: post #53
nopassrecover wrote: post #33

Earlier quoted context omitted.

The deaths from other fuel sources, while not as immediately obvious as "oh look that nuclear plant just blew up" are potentially far greater.

Frankly, I have heard that argument many times. I know other fuel sources cause deaths too. Gas tanks can explode, fossil fuels exhaust gasses can be poisonous, oil can leak into the sea, and so on. And still I'd rather be exposed to all of those risks than worry about one nuclear explosion. As I said, the consequences can be just too horrible, for too many people. I'd love to move on from fossil fuels to something e…

That's because you're mind is clouded by the effects of a mental fallacy (the availability heuristic to be precise) http://en.wikipedia.org/wiki/Availability_heuristic

Re: Germany shuts down seven reactors‎ because of Fokushima

#74

Post by ch0wn »

jgrahamc wrote: post #16
bhousel wrote: post #9

This strikes me more as a political stunt by Merkel to rally the conservative base in Germany than anything else. Still, it doesn't surprise me that this is such a hot button issue right now. I've long been a supporter of nuclear power, but the events of the past week have made me start to reconsider a lot of my beliefs about its safety.

Which beliefs? That a nuclear power station situated in a major earthquake zone next to the coast could magically survive a 9.0 earthquake and a tsunami? Right now, we don't know how serious this situation is, it could be that this will end with a small amount of radiation leaked and four reactors that have to be decommissioned. Or it could end with a major environmental disaster. We simply don't know yet. I'd cautio…

The nuclear power plants in Germany are a mess. Negative findings of investigations magically disappear, threats like earth quakes are simply ignored. The pre-defined runtimes are exceeded and still most of them are running. Turning these off is reasonable. It was without the Japan Desaster and still is.

Re: Germany shuts down seven reactors‎ because of Fokushima

#75

Post by [deleted] »

bhousel wrote: post #69
jgrahamc wrote: post #16

Earlier quoted context omitted.

Which beliefs? That a nuclear power station situated in a major earthquake zone next to the coast could magically survive a 9.0 earthquake and a tsunami? Right now, we don't know how serious this situation is, it could be that this will end with a small amount of radiation leaked and four reactors that have to be decommissioned. Or it could end with a major environmental disaster. We simply don't know yet. I'd cautio…

I've done a ridiculous amount of reading the past few days, and I still believe that nuclear power is probably the best source of power that we have available to us. But I didn't realize that keeping a reactor vessel (and fuel storage pools) cool after the reactor has been scrammed is such a challenge. I also didn't know that hydrogen explosions are a normal byproduct of cooling down a reactor core. Yes, I know that…

[deleted]

Re: Germany shuts down seven reactors‎ because of Fokushima

#76

Post by ErrantX »

mironathetin wrote: post #26
bhousel wrote: post #9

This strikes me more as a political stunt by Merkel to rally the conservative base in Germany than anything else. Still, it doesn't surprise me that this is such a hot button issue right now. I've long been a supporter of nuclear power, but the events of the past week have made me start to reconsider a lot of my beliefs about its safety.

I still remember the voices after Chernobyl: Light water reactors are safe and core meltdown can never happen, because the moderator is water. If it evaporates, the moderator is gone and the core will cool down. Chernobyl was a graphite moderated reactor. When the core overheated, the graphite melted together with the uranium and the nuclear reaction could not be stopped any more. Now we see how reliable those report…

Hmm, I think it is readily accepted and established that complete loss of coolant in a LWR will lead to meltdown - although I can't comment on whether that was the scientific opinion immediately after Chernobyl.

The problem at Chernobyl is not as you describe. The issue there was that through a process of bad core management, while trying to shut down the reactor and at the same time run an experiment, meant the core ended up in a very unstable state. Mostly the instability was managed automatically but at some point it went wrong; there is much debate over this, though conventionally it is accepted that someone, it is not known who, SCRAMmed the reactor - the poor design of the control rods meant that rather than immediately stop the reaction it actually made things worse as they were inserted, causing the core to overheat causing extreme pressure, cracking the control rods and essentially making the situation unrecoverable. Then a steam explosion broke the pressure seal and the chamber emptied of coolant.

After that the exact mechanics of what happened is somewhat unknown (instrument failure) but the lack of coolant lead to a critical "nuclear excursion"; i.e. essentially the neutron emission becomes so large that the fuel becomes supercritical. The excursion heated the fuel so that it expanded and "exploded" out of the pressure vessel; once that had happened the fuel was dispersed and the nuclear reaction ended.

At that point the graphite was exposed to the air and caught fire; it was this (and the resulting smoke plume) that spread most of the radiation.

Re: Germany shuts down seven reactors‎ because of Fokushima

#77

Post by uvdiv »

mironathetin wrote: post #26
bhousel wrote: post #9

This strikes me more as a political stunt by Merkel to rally the conservative base in Germany than anything else. Still, it doesn't surprise me that this is such a hot button issue right now. I've long been a supporter of nuclear power, but the events of the past week have made me start to reconsider a lot of my beliefs about its safety.

I still remember the voices after Chernobyl: Light water reactors are safe and core meltdown can never happen, because the moderator is water. If it evaporates, the moderator is gone and the core will cool down. Chernobyl was a graphite moderated reactor. When the core overheated, the graphite melted together with the uranium and the nuclear reaction could not be stopped any more. Now we see how reliable those report…

I still remember the voices after Chernobyl: Light water reactors are safe and core meltdown can never happen, because the moderator is water. If it evaporates, the moderator is gone and the core will cool down.

You misunderstood. No one reasoned that loss of water coolant would somehow cool the reactor (that's self-evidently absurd); they reasoned, and still reason, that loss of coolant would shut off the fission reaction. This rules out, not meltdowns, but uncontrolled power excursions like the one that created the steam explosion that blew up Chernobyl.

Re: Germany shuts down seven reactors‎ because of Fokushima

#78

Post by ugh »

nakkiel wrote: post #29
bhousel wrote: post #9

This strikes me more as a political stunt by Merkel to rally the conservative base in Germany than anything else. Still, it doesn't surprise me that this is such a hot button issue right now. I've long been a supporter of nuclear power, but the events of the past week have made me start to reconsider a lot of my beliefs about its safety.

Assuming the conservative base in Germany wouldn't back Nuclear Energy. I don't know what it's worth but this wouldn't be true in France for example. As for reconsidering Nucealr Energy, I still think we should wait for the end of the whole thing. Indeed I realize this won't happen.

It‘s not so much about the conservative base. The CDU can be relatively sure that their base will vote for them regardless. Opposition to nuclear energy is a popular position in Germany, also in the political center. This decision is supposed to appease those voters.

Re: Germany shuts down seven reactors‎ because of Fokushima

#79

Post by bhousel »

mortenjorck wrote: post #58
jgrahamc wrote: post #16

Earlier quoted context omitted.

Which beliefs? That a nuclear power station situated in a major earthquake zone next to the coast could magically survive a 9.0 earthquake and a tsunami? Right now, we don't know how serious this situation is, it could be that this will end with a small amount of radiation leaked and four reactors that have to be decommissioned. Or it could end with a major environmental disaster. We simply don't know yet. I'd cautio…

The real tragedy here is that while it's almost certain no civilians will die from radiation poisoning in this case, there quite likely will be or have already been deaths stemming from lack of electrical power. But people dying from illness from lack of clean water because their water treatment plant is offline and their hospital is out of emergency power doesn't get TV ratings, pageviews, and political attention li…

The loss of power is actually one of the aspects of the situation that I find especially tragic.

The USS Ronald Reagan is only 100 miles offshore and has its own nuclear power plant that could be tied into the local grid to provide emergency power to things like the water treatment plants, hospitals, and even the cooling system at the Fukushima Dai-ichi facility.

I know the details of parking an aircraft carrier outside a devastated port city and plugging it into the grid aren't trivial, but I wonder if it's something that's been considered?

FWIW: some great discussion here: http://message.snopes.com/showthread.php?t=52136

Re: Germany shuts down seven reactors‎ because of Fokushima

#80

Post by mironathetin »

mironathetin wrote: post #26
bhousel wrote: post #9

This strikes me more as a political stunt by Merkel to rally the conservative base in Germany than anything else. Still, it doesn't surprise me that this is such a hot button issue right now. I've long been a supporter of nuclear power, but the events of the past week have made me start to reconsider a lot of my beliefs about its safety.

I still remember the voices after Chernobyl: Light water reactors are safe and core meltdown can never happen, because the moderator is water. If it evaporates, the moderator is gone and the core will cool down. Chernobyl was a graphite moderated reactor. When the core overheated, the graphite melted together with the uranium and the nuclear reaction could not be stopped any more. Now we see how reliable those report…

uvdiv, I did not misunderstand.

The light water is the coolant AND the moderator. You need a moderator that slows down the emitted neutrons to keep the nuclear chain reaction going.

But evidently, the water is not the only moderator they use. They don't use graphite, though.

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