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Author: Subject: Japanese nuclear reactor problems
Magpie
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 Quote: Originally posted by ScienceHideout To me, those look like functional cooling towers. snip

Actually I haven't seen any structure that looks like a cooling tower. Are you sure that the final cooling loop is not just using seawater cooled heat exchangers?

------------------------

FYI, here's an NRC document on BWR design showing the Mark I, II, and III:

[Edited on 16-3-2011 by Magpie]

The single most important condition for a successful synthesis is good mixing - Nicodem
entropy51
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 Quote: Originally posted by gregxy Of course it is harder than connecting a fire hose to the reactor. And the people that designed the thing know all this to 5 decimil places. I'm just trying to get some understanding of the magnitude of the problem since you cannot tell anything from the media reports. Even if I'm off by 10X it is still managable situation. If you don't agree with it fine. Present a better calculation, anyone can throw stones.
Apparently you think that one can calculate the thermal-hydraulics of a nuclear reactor under going a severe accident using back of the envelope calculations. As I pointed out, your heat source is a factor of 3 too low because you don't know the difference between the electrical and thermal ratings of a reactor. Your heat source is also low by orders of magnitude because you don't realize that the zirconium cladding is reacting with superheated steam to produce much more energy than the decay heat. You also assume that all the energy enters the coolant with perfect heat transer, ignoring the Leidenfrost temperature limits on heat transfer from superheated metal. You don't understand boiling heat transfer and departure from nucleate boiling. I will let my stone throwing stop with that.

Better to remain silent and appear a fool than to open your mouth and remove all doubt.
Twospoons
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Its also not simple as they will be pumping against an awful lot of steam pressure. IIRC the normal operating temp for the reactor is around 250C - which puts the steam pressure at ~39 atmospheres .

Personally, I think they've done bloody well so far, when you consider what they've been hit by : 9.0 quake and a monster tsunami - far outside what had been considered. Its easy to look back and say "oh, they did *this* wrong, they should have been better prepared etc". But, as with any engineering project, you have to draw a line somewhere otherwise nothing would ever get built. There's no crystal ball handed out with the engineering degree.

[Edited on 17-3-2011 by Twospoons]

Helicopter: "helico" -> spiral, "pter" -> with wings
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 Quote: But, as with any engineering project, you have to draw a line somewhere otherwise nothing would ever get built.

With regards to Fukushima, that clearly would've been a good thing. The line wouldn't have needed to be drawn too far away either, seeing as the problems with the reactor design, and the obscenely dangerous location, were very well known.

Also, I don't consider losing control over the situation, leaving others to speculate whether it'll dump lethal doses of radiation all over Japan, to be "doing well." A number of people have died, more may die yet from injuries, and there will surely be more cancer deaths due to the fallout already released. There's been four huge explosions, two of the containment vessels are cracked, multiple fires have broken out near massive quantities of nuclear waste, and the site is so radioactive now that approaching it may soon become a suicide mission. The waste pools are apparently dried up, and if that fuel bursts into flame in the open atmosphere, it will make Chernobyl look like a joke. Good luck throwing water on it at that point, too - counterintuitively, it could result in an inadvertent criticality.

I weep at the sight of flaming acetic anhydride.
DDTea
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Someone pointed out the Fukushima One station's "dangerous location." From what I can tell, it is a practical reality and maybe we're fortunate that it is located where it is: next to the sea. At least they can pump in sea water in the event of this kind of emergency and so far, much of the radioactive vapors have been carried out to sea instead of solely traveling over land and population centers.

That said, the operating conditions are exceedingly dangerous. The logistics are a nightmare that you or I simply cannot imagine. Suppose they do order an immediate, total evacuation of an area of 30km or so in a country with a population density as high as Japan. Short of teleportation, they'd have to open up both directions of their highways. The situation is further complicated by massive debris fields and blocked roads. The road traffic would make it a lot more difficult for emergency vehicles to get into the area. They would need to setup emergency shelters, they would need to ration food, there may be issues of law and order.

I can't imagine there being a point where everyone says, "Run for your lives!" and abandons ship. That would create a situation in which it is probably better to die than to survive. With that in mind, the Japanese authorities are probably sparing no efforts in containing the situation as much as possible. Any public panic would complicate that and may very well be the straw that breaks the camel's back. Should the situation suddenly go downhill quickly anyway, it may be that those who remain in the evacuation zone are going to die anyway. In their near-term future, it may be easier to simply let them die as soon as possible than to burden the already exhausted resources of the post-disaster country.

I hate to sound so cold, but these are the facts facing decision-makers in the event of these catastrophes. It's easy to say, "They could be handling this better." By what standard? When's the last time there was a 9.0 earthquake, tsunami, AND nuclear disaster in a country with such a high population density and such a huge role in the global economy? They are currently setting the standard. Think about that.

What I'm saying is it's easy to say what the Japanese government or TEPCo "should" be doing, but let's all agree: talk is cheap.

"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
Twospoons
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Did you read the whole sentence? Its been hit by forces so far outside the design parameters its amazing its all still standing. They've lost power, back-up power, back-up back-up power, had several explosions - and still haven't had a major leak. I call that heroic! Would you want to be on that site, desperately trying to cool 3 reactors and a spent fuel pool in the aftermath of a nationwide disaster? Things may still end really badly, but give them credit for trying.
I wish them the best of luck.

Helicopter: "helico" -> spiral, "pter" -> with wings
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 Quote: Someone pointed out the Fukushima One station's "dangerous location." From what I can tell, it is a practical reality and maybe we're fortunate that it is located where it is: next to the sea.

The location is why the disaster happened - the tsunami flooded the diesel backup generators, disabling them.

 Quote: What I'm saying is it's easy to say what the Japanese government or TEPCo "should" be doing, but let's all agree: talk is cheap.

My complaints don't pertain to what they're doing now, but what they should have done before - namely, not build a nuclear power plant right next to the ocean in a region prone to earthquakes and tsunamis. They didn't even bother to build it to survive the strongest expected earthquake (or tsunamis in any way whatsoever). Additionally, they ignored warnings from GE engineers that the containment vessel was basically garbage.

Twospoons, I do not mean to criticize the operators of the plant. Any attempt to do so would, in my eyes, amount to cruel slander. The accident is not their fault, and their efforts to mitigate its consequences have been nothing less than selfless and heroic. They did not make the decision to build the plant in such a poor location, to cut corners on costs for safety mechanisms, to implement a poor design to save money, or to build a nuclear power plant at all.

 Quote: and still haven't had a major leak.

They've had to evacuate the plant due to very dangerous radiation levels, and several workers have been hospitalized for acute radiation sickness. It doesn't have to be as significant as Chernobyl to be considered "major," or to have wide reaching implications for the health of staff and people in surrounding areas.

I weep at the sight of flaming acetic anhydride.
DDTea
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Earthquakes are almost a daily occurrence in Japan. The Fukushima power stations (and all power stations in Japan) have survived hundreds of earthquakes, including many strong ones. That's a good track record. As far as where they should have been located, though, again: I think placing it by the sea showed a lot of foresight (although the issue of the backup generators is going to warrant a serious investigation).

Imagine if they'd placed the power stations inland, suppose on higher terrain to safe-guard it from tsunamis. What if the reactor cooling failed for a different reason? There would be no feasible way to cool them down. More than that, radioactive clouds would drift overland and possibly over cities. Dangerous isotopes could fall out in the rain, contaminating groundwater, livestock, and plants. Again, it's good that Fukushima One is surrounded 180 degrees by water.

 Quote: Did you read the whole sentence? Its been hit by forces so far outside the design parameters its amazing its all still standing. They've lost power, back-up power, back-up back-up power, had several explosions - and still haven't had a major leak. I call that heroic! Would you want to be on that site, desperately trying to cool 3 reactors and a spent fuel pool in the aftermath of a nationwide disaster? Things may still end really badly, but give them credit for trying. I wish them the best of luck.

I read the sentence, but I was pointing out that a lot of the analyses I've seen are very simplistic--not that yours was, you hit the nail on the head. Expanding on what you said, all four reactors at Fukushima Number Two (Dai-Ni) successfully SCRAM'd and although there was a hiccup with the coolant systems in reactors 1, 2, and 4, all were brought online and all reactors are below 100 C right now--after the same set of circumstances that hit Fukushima Number One.

Nuclear power accidents are horrible and really, we won't even begin to understand the effects for at least a decade. The radiation effects will make themselves known in stillbirths, blood cancers, development disabilities (physical and mental), etc. That said, hydroelectric power still has caused the most severe accidents in terms of loss of life and destruction of property.

"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
Twospoons
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 Quote: Originally posted by madscientist They didn't even bother to build it to survive the strongest expected earthquake (or tsunamis in any way whatsoever).

As it happened the reactors survived a quake much bigger than planned for. If not for the tsunami, all would be well.
I believe they did have a sea-wall to stop tsunami - it was simply overcome by the exceptionally huge wave generated by this event. You can say it should have been bigger - but how much bigger? 10m? 20m? 100m?

If there is a silver lining to all this misery, it will be a global review of reactor safety, and contingencies for multiple failures. Lets hope the accountants don't get in the way.

Until nature throws us another curve ball ...

@DDtea : my comment was not directed at you - your post went up while I was typing

[Edited on 17-3-2011 by Twospoons]

Helicopter: "helico" -> spiral, "pter" -> with wings
DDTea
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 Quote: Originally posted by Twospoons If there is a silver lining to all this misery, it will be a global review of reactor safety, and contingencies for multiple failures. Lets hope the accountants don't get in the way. Until nature throws us another curve ball ...

Also a good point. I don't mean to change the topic, but this raises serious questions about Iran's desire to adopt nuclear power. That is also an extremely seismically active region of the world and many powerful earthquakes have hit the country (e.g. 2003 Earthquake in Bam).

It's also good to see questions being raised about reactors along the West coast of the United States. Some of the debate may be from hysteria, but in any case it's better to allay fears with honest facts and debate than to simply disregard them.

"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
Sedit
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Sorry to stray a little bit here but being as active as this story is I have no doubt it will get right back on topic in no time,

Does anyone know why they even build these things above ground? Why not bury them as deep as possible so that in case of an accident its nothing major at all. Underground bomb testings happened on a major scale as evident by the google earth pictures of Area 51, It looks like the surface of the moon its so cratered. However they still managed to plant the next device shortly after the last went off meaning radiation underground is of little concern.

What use comes from placing these things to the elements where they could go off and do a great amount of harm?

Knowledge is useless to useless people...

"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story before."~Maynard James Keenan
Twospoons
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I was wondering the same thing. $probably.$ always get in the way of truly great engineering.

Helicopter: "helico" -> spiral, "pter" -> with wings
Magpie
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 Quote: Originally posted by DDTea It's also good to see questions being raised about reactors along the West coast of the United States. snip

Are you talking about future possible constructions here? There's currently only two operating nuclear stations on the US West coast, ie, San Onofre and Diablo Canyon.

NRC Region Four (West)

* Arkansas Nuclear One, Arkansas
* Callaway, Missouri
* Columbia, Washington - formerly WNP-2
* Comanche Peak, Texas
* Diablo Canyon, California
* Fort Saint Vrain, Colorado (Decommissioned)
* Grand Gulf, Mississippi
* Hanford N Reactor, Washington (Retired - see Plutonium Production Reactors below)
* Humboldt Bay, California (Decommissioned)
* Palo Verde, Arizona
* Pathfinder, South Dakota (Decommissioned)
* Rancho Seco, California (Decommissioned)
* River Bend, Louisiana
* San Onofre, California
* Sodium Reactor Experiment, Santa Susana Field Laboratory, California (Accident 1959, Closed 1964)
* South Texas Project Electric Generating Station, Texas
* Trojan, Rainier, Oregon (Decommissioned)
* MSTR, Missouri
* Vallecitos, California (idle research center)
* Waterford, Louisiana
* Wolf Creek, Kansas

[Edited on 17-3-2011 by Magpie]

The single most important condition for a successful synthesis is good mixing - Nicodem
Regolith
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This is likely about to get better. They have almost finished the repairs to the power lines that activate the pumps to bring the cooling systems back online. The 50 workers who are risking their lives to keep the stricken plant running and are leaving the site and returning in teams to avoid the bulk of radiation are all heros.

Re. underground reactors. Think for a moment about that... Ground shakes and the say 40,000 tons of material above the reactor underground breaks free from the sides of the earth and is supported by nothing but the roof of the reactor, crunch. Further underground it's going to be already right beside the water table... Really bad idea. Watch the video link I posted above it talks about chernobyl and the water table. Running reactor with neutron output plus groundwater equals radioactive groundwater. Hence why they aren't underground.
watson.fawkes
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 Quote: Originally posted by madscientist The location is why the disaster happened - the tsunami flooded the diesel backup generators, disabling them.
I want to underline this point. The standard practice for life safety in tsunami zones is "vertical evacuation": get the people into a tall building above the surge level. I can't figure out why the design engineers didn't take the same approach, in advance, for the backup generators. Just build a four-story building near to the reactor (but not too near) and put the generators on the top floor. Such a building can be built to withstand even a 9.0 earthquake with adequate amounts of structural steel. Better steel geometry would help, too. Steel in most buildings is on a cubical grid of some form, usually with diagonal reinforcement in one of the major planes. Building the frame on the crystal space-filling plan of the octet truss would give such a building a quite high strength-to-mass ratio.

If you don't believe in getting backup power higher than the surge level with a building, just pick another site for the reactor that's high enough above sea level.
MrHomeScientist
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Slightly off topic, I've gotten a huge surge of interest in my YouTube video on making potassium iodide since the disaster. Many people are saying most places are sold out of KI tablets, and asking where to get the I2 and KOH for the reaction so they can make it themselves. The reaction, FYI, is 3I2 + 6KOH --> KIO3 + 3H2O + 5KI

I've been cautioning people to <b>not</b> try eating anything made in the lab, because I would never consider it. I just can't be sure of the purity of my reagents, and the product is almost certainly contaminated with excess I2, KOH, or KIO3.

While I'll still go on saying that, is that actually the case? I2 can be easily purified by sublimation, and the KI by multiple recrystallizations. According to KI's wiki page the dosage for adults is only 130mg/day, so even if there were impurities they would be almost at trace levels at that quantity. I'm starting to wonder myself if it's safe or not. As I've said, I'm leaning towards no.
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If you believe in global warming, then nuclear energy is really the only choice. To supply the energy needs for the USA requires 20,000 square miles of solar collectors. I can't
imagine building 20,000 square miles of anything. Here is
an interesting article on that topic:

http://www.scientificamerican.com/article.cfm?id=a-solar-gra...

However that approach will not work for Japan due to its
limited area and northern location. The growing energy
needs of China will present some real interesting issues.

Workers die in coal mining accidents, you just don't hear that
much about it. Workers were killed in the recent BP accident
(which did not turn out nearly as badly as everyone thought).
Wars are fought over oil.

If there were a simple solution, then this problem would have

International Hazard

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 Quote: I can't figure out why the design engineers didn't take the same approach, in advance, for the backup generators.

I would imagine this had been considered, but wasn't implemented due to cost cutting from above.

It was crazy to plop something sensitive to flooding adjacent to the ocean in an area prone to tsunamis and hurricanes. It's on the level of smoking cigarettes in a meth lab in a densely populated urban area - completely reckless and irresponsible.

gregxy: Solar allows the possibility of on-site power generation, which means avoidance of transmission losses. 20,000 square miles becomes a lot less intimidating when you consider the total area of all roofs in the US. The technology is also finally starting to become economical.

With nuclear power, acute radiation poisoning deaths indeed are comparable in number to coal mining. What's of concern, however, are the number of deaths, miscarriages, birth defects etc. that follow. For Chernobyl, estimates for deaths caused range from 4000 to a million. Cancer deaths have been often grossly understated by government and industry studies (both having an ulterior motive to gloss over the damages), who tend to only follow exposure victims for the first ten years - the cancers typically develop after a ten year "incubation period." Radiation means cancer and death, period.

Three major disasters in thirty years is not my idea of a good track record for the nuclear industry. And lord knows how many "minor" disasters have occurred that we don't know about. Considering that contaminated sites will remain hazardous for thousands, if not hundreds of thousands of years (in the case of the Chernobyl site), this frequency of occurrence is unacceptable. It's entirely possible, with the quantities of radioactive materials around, for us to render our planet uninhabitable. All the coal we've burned for hundreds of years has failed to do so, but the waste from half a century of nuclear energy is completely capable of it.

I see some similarity to going on a crime spree to fund a drug habit, hoping to get lucky and not get caught, instead of just cutting back on the drugs. We're gambling. We can only plan for what we foresee, and these accidents occur due to what is unforeseen, unrecognized in its significance, or greedily ignored. There will be more accidents. There always are.

Nuclear power is not even cheap or economical anyway. When you remove government subsidies, it becomes comparable to solar and wind power.

I weep at the sight of flaming acetic anhydride.
Arthur Dent
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Aren't there graphite rods in these japanese reactors? In case of a complete catastrophe, an emergency shutdown, called SCRAM is supposed to automatically take effect, and these graphite rods are supposed to drop by the force of gravity alone into the core of a reactor, effectively separating the fuel rods from each other and neutralizing the reactor completely...

Or is this a completely different system that doesn't use that security method?

Robert

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quicksilver
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 Quote: Originally posted by madscientist The location is why the disaster happened - the tsunami flooded the diesel backup generators, disabling them.

This is such a significant point that (IMO) it should be the focus of the issue. The level of safety on many things depends on orientation and location. A motorcycle is substantially safer where there is less (or no other) traffic; just as rifle ranges have back-stops, etc. Setting up any condition that is influenced by exterior stimuli (or lack there-of) is placing an "unknown" in the equation.

hissingnoise
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I agree qs, hindsight is a great thing but we all know that the designers of the plant had at the time believed that the chances of a 'quake occurring at the magnitude of the one that hit were so vanishingly small that safeguarding against such a scenario would have looked like expensive overkill . . .
There seems to be an element of sheer bad luck in all that's happened in Japan!
And things are unlikely to get much better any time soon.
It must be extremely frightening and depressing to have to live through a disaster of this size and complexity.
And the stoicism of those people we've seen on our screens is remarkable.
What more can one say?

gregxy
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Quote: Originally posted by entropy51
 Quote: Originally posted by gregxy Of course it is harder than connecting a fire hose to the reactor. And the people that designed the thing know all this to 5 decimil places. I'm just trying to get some understanding of the magnitude of the problem since you cannot tell anything from the media reports. Even if I'm off by 10X it is still managable situation. If you don't agree with it fine. Present a better calculation, anyone can throw stones.
Apparently you think that one can calculate the thermal-hydraulics of a nuclear reactor under going a severe accident using back of the envelope calculations. As I pointed out, your heat source is a factor of 3 too low because you don't know the difference between the electrical and thermal ratings of a reactor. Your heat source is also low by orders of magnitude because you don't realize that the zirconium cladding is reacting with superheated steam to produce much more energy than the decay heat. You also assume that all the energy enters the coolant with perfect heat transer, ignoring the Leidenfrost temperature limits on heat transfer from superheated metal. You don't understand boiling heat transfer and departure from nucleate boiling. I will let my stone throwing stop with that.

Your right I assumed the ~600MW was thermal when it is really the electrical output, so the residual power for each reactor is 3X higher or on the order of 90MW. I also
assumed that the water left the reactor as liquid at 80C, which seems about right if the backups had worked.

My calculation is based on conservation of the energy
and says nothing about the rate of transfer however,
the reactor was designed to transfer 1800MW so heat
transfer at 90 MW should not be an issue if they can keep water in it. Yes there will be complex heat transfer effects if
the rods are exposed, but if that happens you are f*cked anyway.

If you want to assume that the water leaves as steam, then
you need to include the heat of vaporization 2260kJ/kg
which is 10X more than I assumed and reduces the water
flow needed by 10X. Of course the pressure from the steam
will make it harder to pump water in.

As for energy from the Zr, my guesstimate is there are 10,000 Kg in there or ~ 1e5 moles
Zr + 2H2O -> ZrO2 + 2H2 - 430kJ/M
or 4.3e10J total energy if it all reacted.
This equals the residual power output (90MW) for about
8 minutes. This reaction can further heat the exposed
rods, but it does not seem like a large factor in the overall
energy flow.

Its also interesting to figure out how long it takes the core
to melt if there is no water. The wikipedia BWR article gives
the mass of UO2 in a BWR as 1e5kg. The average
specific heat for U2O over 300K to 3000K is ~400 J/kg/K
So the energy is 400 * 3000 * 1e5 = 1.2e11 J which
means exposed rods melt in about 20 minutes.

YMMV, Don't try this at home....

hkparker
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 Quote: Originally posted by MrHomeScientist Slightly off topic, I've gotten a huge surge of interest in my YouTube video on making potassium iodide since the disaster. Many people are saying most places are sold out of KI tablets, and asking where to get the I2 and KOH for the reaction so they can make it themselves. The reaction, FYI, is 3I2 + 6KOH --> KIO3 + 3H2O + 5KI I've been cautioning people to not try eating anything made in the lab, because I would never consider it. I just can't be sure of the purity of my reagents, and the product is almost certainly contaminated with excess I2, KOH, or KIO3. While I'll still go on saying that, is that actually the case? I2 can be easily purified by sublimation, and the KI by multiple recrystallizations. According to KI's wiki page the dosage for adults is only 130mg/day, so even if there were impurities they would be almost at trace levels at that quantity. I'm starting to wonder myself if it's safe or not. As I've said, I'm leaning towards no.

I think its plenty safe, KI has a very high LD<sub>50</sub> and KIO<sub>3</sub> is sometimes used in anti I<sub>2</sub><sup>131</sup> pills. As long as your sure of no KOH or I<sub>2</sub> contaminates to a reasonable degree. But like you said the doses are extremely small. I have a few hundred grams of reagent / A.C.S. KI that I have as a reagent, and would feel safe taking it if radiation level increased in the states, but I don't think that will be a problem this far away.

"Nothing is too wonderful to be true if it be consistent with the laws of nature." -Michael Faraday
entropy51
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 Quote: Originally posted by madscientist It was crazy to plop something sensitive to flooding adjacent to the ocean in an area prone to tsunamis and hurricanes. It's on the level of smoking cigarettes in a meth lab in a densely populated urban area - completely reckless and irresponsible.
If you check, you will find that any power plant, nuclear or not, has to be situated near a large body of water to provide cooling. In Japan, that's the ocean. I will resist the temptation to add "Duh!" The designers perform a statistical analysis of weather patterns and geologic upsets and identify a set of conditions that is expected to occur no more than once in 100 years. Then they design against that hazard. With large numbers of reactors operating over long time periods, every now and again one will face a hazard exceeding the design conditions. Fukushima was designed to withstand a Design Basis Earthquake of 7.9, very severe. Nature threw a curveball of 8.9. It happens. You cannot afford to design every plant to withstand an infinitely strong earthquake.

 Quote: Originally posted by madscientist With nuclear power, acute radiation poisoning deaths indeed are comparable in number to coal mining. What's of concern, however, are the number of deaths, miscarriages, birth defects etc. that follow. For Chernobyl, estimates for deaths caused range from 4000 to a million.
The only fatalities due to radiation in the nuclear power industry were 28 who died after Chernobyl. It is not unusual for more than that many coal miners to die in a single accident. Your figures are wrong. Care to cite a reference for a million dying as a result of Chernobyl? That's wrong too. Please support your assertions with some data. Study after study has shown that not one single death occurred as a result of Three Mile Island, the worst nuclear power accident in the United Sates.
 Quote: Originally posted by madscientist Nuclear power is not even cheap or economical anyway. When you remove government subsidies, it becomes comparable to solar and wind power.
When you remove the subsidies and tax breaks given to the oil, gas, coal and utility industries, there is no cheap or economical way of generating electricity.

Every advanced modern technology is a deal with the devil. Nuclear power is no exception.
DDTea
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 Quote: Originally posted by Arthur Dent Aren't there graphite rods in these japanese reactors? In case of a complete catastrophe, an emergency shutdown, called SCRAM is supposed to automatically take effect, and these graphite rods are supposed to drop by the force of gravity alone into the core of a reactor, effectively separating the fuel rods from each other and neutralizing the reactor completely... Or is this a completely different system that doesn't use that security method? Robert

The control rods contain Boron or some other substance with a high neutron-capture cross section ("neutron poisons"), which moderate the nuclear reaction. They're built on a fail-safe mechanism, as you described: if there is a sudden power loss, they will drop by force of gravity into the reactor. It doesn't separate the fuel rods, but simply captures the neutrons and poisons the nuclear reaction.

That said, the reactors did SCRAM. However, the core is still very "hot" (both thermally and in terms of radioactivity) and that's where the issue is coming from. I know next to nothing about nuclear chemistry, so I won't try to expand on that further!

Again, pointing out the elephant in the room: the situation is normal at Fukushima Dai-Ni power station, which experienced the same 9.0 earthquake and massive tsunami as Fukushima Dai-Ichi. Dai-Ni also lost power to its coolant pumps, but they were brought online and the reactors are now all offline.

What that tells me: the problem wasn't the earthquake or tsunami. Those were contributing factors. By analogy: lab accidents do not happen for only ONE reason. They result from a combination systematic safety failures, unforeseeable situations, bad luck, etc.

This may shed some light on the situation: http://cnic.jp/english/newsletter/nit117/nit117articles/nit1...

TEPCO has a history of data falsification.

 Quote: Originally posted by hkparker I think its plenty safe, KI has a very high LD50 and KIO3 is sometimes used in anti I2131 pills. As long as your sure of no KOH or I2 contaminates to a reasonable degree. But like you said the doses are extremely small. I have a few hundred grams of reagent / A.C.S. KI that I have as a reagent, and would feel safe taking it if radiation level increased in the states, but I don't think that will be a problem this far away.

Don't do this. Any potential benefits are far outweighed by the risks. Pharmaceuticals are produced according to extremely strict specifications (look up GMP's and the Pure Food and Drug Act). You have no idea what's in your tap water, your reagents, on your equipment, etc. I'm not simply referring to chemical contamination because that's only part of the problem: I'm referring to pyrogens, bacteria, and who knows what else.

Besides, KI only protects you from Iodine-131's accumulation in your thyroid. It does nothing against Strontium-90, Cesium-137, inhaled alpha radiation, beta particles, neutron radiation, gamma radiation.

Again, some silver-lining: the Japanese already have a diet rich in iodine because they eat so much fish and seaweed!

[Edited on 3-18-11 by DDTea]

"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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