Posted on 03/15/2011 7:39:54 PM PDT by Mr. K
The plants after a cold shutdown have residual energy of about a third of a megawatt, from nuclear decay only.
That’s simply not sufficient to make the core turn critical.
If they are smart, the “US military help” they ask for will be include several Predators or other RPVs with IR imaging capability. That would greatly enhance their knowledge of the situations in the reactor buildings — and just might detect a few survivors in the tsunami rubble...
Interesting. I have my Google Earth window looking at Yucca Mount at this very moment. After all we spent there, it is sheer idiocy not to go ahead and use it as a spent fuel site.
If only we had plants there ... but what those are nothing but "piles," at best. Nobody knows what's inside.
The difference is huge. In a normal reactor the fuel is carefully spaced, interleaved with moderating material, and has channels for the coolant. In a failed reactor we have none of that; the fuel may be wherever it wishes (at the bottom, likely) and the moderating material is somewhere on top, where it does nothing, and the coolant is nowhere in sight, and the heat-producing area is a small pool of white-hot lava. I have no idea where the Japanese reactors are on this scale, but clearly not at the "perfectly functioning" end of it.
Yes buccaneer81, Silkwood came to mind reading the wild assumptions and seeing the gullibility of so many. People who saw the Silkwood movie never realized that this activist, I believe with some substance abuse problems, drank plutonium in solution for a month and died in an auto accident. This "most dangerous substance known to man" didn't even give her indigestion.
The discussions here have much of that flavor. Three Mile Island resulted in a full core melt and no one was hurt. Tiny amounts of radioactive iodine were released, not as much as you'd get walking around an oncology center where thyroid uptake exams are administered, and not nearly the radiation exposure someone taking time from the clearup to ski at Aspen would absorb flying to and spend a few days at altitude.
Even non-commercial Chernobyl, which had no containment, resulted in two direct radiation deaths and various estimates up to about 150 due to burns (not from radiation) and some excess leukemia (although those data are in the noise). A number of deaths at Chernobyl were alcohol poisoning. How much of the excess drinking was the direct result of the frightening scenarios created by the press fed by left-wing propagandists is impossible to know. Still the worst quantitative risk related to Chernobyl was caused by its in-operation. Replacement electricity was generated by coal, which results in about two hundred excess deaths from respiratory illness per thousand megawatts per year. (Coal plants release, on average, much more than one thousand times more radionuclides into the air than nuclear plants. While true, that statement depends upon the extremely low amounts of radiations released by nuclear plants. Neither technology poses a risk from radioactivity. Coal, after all, is dug from the earth, where uranium is not a rare mineral)
Nuclear power development ended in the the U.S. forty years ago, largely because coal was so inexpensive, and because of our energetic left-wing antinuclear cabal, actively supported by our enemy, the USSR. It remains the safest ever source of electrical power, never having resulted in a single death from commercial plants. The Chinese are smarter than we are. They have brought four new plants on line over the past two years. These are based upon GE designs. Since GE Nuclear was acquired four or five years ago, the Chinese bought these from the Japanese owner, Toshiba, I believe. China is executing a plan to bring on 124 plants by 2025. They will look at Japan and have no doubts that there is no safer source, and clean the air in Beijing and other large cities in the bargain. Think of what would have happened had the earthquake occurred near one of the enormous dams in China, Brazil, or the U.S.
Radiation monitoring is a very mature technology. The exposure limits, just extended from very low tolerance levels to about the level of a dental X-ray, are extremely conservative. Too bad about the loss of the reactors, but the cost of reactors, when you are not funding teams of wealthy lawyers working for both defense and prosecution, is recovered before the second year of full power production. The U.S. has become the golden egg by the lawyers and for the lawyers, who produce nothing but stifle so much.
Cooling the reactors without external power is ugly, but well understood and will almost certainly result in the continued perfect record of commercial nuclear power. All the Japanese reactors were shutdown within seconds of the quake. Without the diesel generators, a problem which will no doubt be addressed in future plant designs, the stored heat from the no-longer-fissioning cores is carried away by boiling - by steam. These are boiling water reactors. Like your auto radiator when the fan belt is broken, the heat is radiated but there is no convection cooling. What happens with the car is that the pressure valve is forced open releasing steam which carries away heat. Since the pumps aren't working, the heat transfer is much less efficient, and some of the contaminants get released with steam which is, like the radiator cap, set to release when pressure could burst the radiator. The short-lived radionulides - half lives of hours, and are of little danger. They are the result of neutrons activating impurities in the now contaminated water.
These reactors have been cooling since the quake and have less than 1 percent of their rated energy remaining in the core. It will cool in time. Not having tracked reprocessing for years, a guess is that uranium is cheaper on the market than the cost of reprocessing, or those stored fuel rods would not be there. France, the USSR, England, and the U.S. had reprocessing plants. Not sure the U.S. still has a plant operational. But referring to used fuel rods as "waste" is naive. These rods have ninety percent of the fissile material remaining to be used. If we don't reprocess, it is for political reasons.
If the U.S. continues its suicidal “Path not Taken” (from "Small is Beautiful" E.F. Shumacher), we had better learn Mandarin or Spanish or Russian because our currency, manufactured goods, and perhaps even food, will come from another country. China already needs to subsidize our economy so that we can buy windmills to tilt toward and solar panels from them, which enables them to build their 124 new nuclear plants. For the time being, our fantastical economy keeps China's factories busy producing Ipods and flatscreen televisions; so China is loaning some money to its workers while helping our politicians avoid the reality of the hole they have dug for us.
Some conservative pundits point to the fact the the U.S. still has the “largest economy.” We are spending borrowed money to buy goods manufactured in those countries which are building the energy infrastructure we used to have. We are insolvent today, and creditors will demand better terms for the greater risk they are taking, knowing that soon we must default if they don't boy our bonds. China really doesn't need us, and they will decide when to let the crisis proceed.
Japan will replace the Fukushima plants within five years with new nuclear plants, and they will survive the next 9.0 earthquake and tsunami, without injuring citizens or workers, just as these have, but still run afterward!
0.5% of full output is still a significant amount of BTUs... something on the order of 5KW per MW of operational output.
Empirically, though, it is obviously still significant in this case -- otherwise there would be no ongoing thermal problems, and everyone could go home and get some sleep...
Thank you. Your curve supports my explanation.
Dumbed down? For verification of your statement, just read this thread ...
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I don't recall saying that!
What I did say was that, after a reactor has operated for a while, it accumulates reaction products (in the fuel rods) that, due to radioactive decay, continue to produce heat -- even after the fission reaction is shut down.
The good news (in this case) is that their thermal output decreases exponentially as a function of their half-life. (See jwalsh07's graph above in #311.)
The bad news is that, even after ten days, that radionuclide decay heat output is still significant enough to require supplemental cooling.
Your wild runaway scenario is more bunk than Hanoi Jane in the China Syndome. For one thing, the boron that has been dumped into the reactors will "poision" the reaction to prevent re-start of fission. (That's why new designs also include a boron "catch bowl" beneath the containment vessel....)
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"Stellar levels" -- from a small fission reaction? Talk about "Drama llamas"! Time for you to go to bed -- and when you wake up tomorrow, I recommend signing up for a course in high school physics -- and a Valium prescription...
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"But I'm not a nuclear engineer anyway, what do I know..."
First question you should have asked... '-)
Thank you for that.
I think you have an idea worth discussing
For everyone here who may not know, a nuclear generator works by putting enough of the fuel together to make a pile big enough to start reacting.
One little piece of that material in your hand is radioactive and all that, but it wont do anything. (except kill you)
But put 10,000 little pieces of it together and it starts getting hot. This is how they generate heat to make the steam generators work.
If it gets too hot it will melt into a pool of molten material.
Put enough of it together quickly with a lot of pressure and it will explode - a nuclear bomb.
The fuel is shaped into rods, they are kept physically apart by other rods inserted in spaces between them that shield each piece from the others and prevents the reactions. They move the rods in and out to increase/decrease the heat.
Whan a nuclear generator ‘scrams’ it means they slam down the shielding rods between the nuclear fuel rods, and cool everything as fast as possible.
If they cannot cool it then it starts to overheat and melt. The theory is that it can get so hot it will melt through everything, sinking into the earth. When it hits the water table then whammo.
So it seems what we have in japan is a pile of melted material.
Should it be left in a big pile? Or blow it apart with a bomb so that there is not enough of the matierial next to itself to continue to heat up.
Doing that would expose a lot of radiation, pretty quickly- but it would prevent additional heating by seperating the material into smaller pieces far away from each other.
Geez my typos are getting bad- my eyesight is going with my old age...
Yeah, but one that hangs around for a looooong time.
Perhaps the CANDU reactors are safer, but one just had a leak of water:
Canada regulator reports water leak at nuclear plant
Why is a safer reactor leaking water?
Point is that the decay rate is exponential, and will decrease over time. That’s the only thing generating heat.
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