140mio tons of maize are being turned into ethanol in the USA alone. That's a quarter of the world maize production. Last year the world was supposedly in shock when Russia had the worst drought in 100 years or so and wheat production fell short by 10mio tons. (Yes, maize is not wheat, but the shortfall of the drought is still negligible in comparison to the amount of food burned.)
The consequences of Fukushima are a direct result of the power station being unchanged since the 1970ies, even though it became clear already in that decade, that safety precautions were insufficient. Especially concerning the risk of hydrogen explosions (hydrogen was already a known problem during the Three Mile Island accident in 1979), the lack of autocatalytic recombiners (which prevent them) and the lack of filtered containment vents - which were installed in both Germany and France (which you mention here) in the 1980ies and 90ies, in anticipation of otherwise unacceptable releases during a meltdown.
But Desertec doesn't plan to use sea water to cool its turbines - which would be hard to do anyway, because of the way such plants scale. The turbines and thermal storage must be centrally located in the collector array and this array is limited in size. Otherwise losses are too large. Which makes placing the turbines next to the coast impractical, not to mention a lot more expensive.
The 2km^2 demonstration plant Andasol already cost 300mio Euro, delivering about as much electricity as a small conventional 20MW power plant (180GWh per year). The new 12km^2 plant in Morocco, based on the same technology, is going to cost 2bn Euro. Right. Six smaller plants in Spain are cheaper than one big plant in Morocco - so much for claims that larger plants and more experience would decrease costs.
I'm not talking about sodium. I haven't said a word about sodium. It's an entirely different material, they neither belong to the same group of chemicals nor do they contain the same atoms. They don't have the same chemical reactions. And I'm not being dishonest for not talking about the properties of molten Na-metal, when I'm talking about LiF and BeF2 salts. You don't blame people working with concrete for not mentioning the flammability of wooden structures either.
Keep talking to yourself, I'll stop talking to you, that's for sure.
If you read the fourth comment in this thread, which I wrote long before your initial comment, you will find the following:
"As to contact with water causing problems, well, just keep water out of the containment - using either gas-driven turbines or a tertiary coolant loop. (That's part of "moderately well designed".)"
I didn't shift any goal posts, it's just that you're blind to the goal posts I set long ago.
First of all: You don't need steam spin a turbine. In fact, it is more efficient not to use water steam, provided that you have a high enough temperature to begin with. in this case, you can use a Brayton Cycle turbine with CO2 as your working gas.
But even if you insist on using steam turbines, there is nothing to stop you from using two heat exchangers to decouple the (radioactive) coolant flow inside the reactor from the water heated outside of the containment. In this case, if water get in contact with anything hot, it won't be anywhere near the reactor, there won't be any radioactivity involved. It would be a mess, it would be an accident, but not a nuclear one.
I don't think you know how a molten salt reactor works. The salt is not just the coolant, it is also the fuel itself. It contains both the Uranium, Plutonium or Thorium (molten salt reactors can use all of them) and the fission products. As the fuel is liquid and directly accessible, fission products can be removed from the reactor every couple of days, instead of leaving fuel rods (including fission products) in the reactor for over a year. This limits their amount to 1-2% at any time. Things that are not in the reactor in the first place, can't get out in an accident.
It also means that the fuel has a much lower power density. Because the fuel only consists of a small fraction of fissle materials and fission products, whereas fuel rods consist mostly of nothing else. They have a high power density, even after shutdown, because the fission products are tightly packed and there is almost a year's worth of them. Which is why they easily heat up and melt unless there is a steady flow of coolant - once molten, there is a small chance for a Bethe-Tait accident - depending on if and how fast the molten core is collapsing, the distribution of absorbing materials in the molten core and how much fissle material it contains.
None of this should happen on a major scale, but why go the risk of even small damage to the reactor vessel aggravating an accident, if you can avoid it outright by using an incompressible liquid with homogeneously dispersed fuel, where any such scenario is physically impossible? (Also, the amount of fissle material is limited to the minimum necessary to keep the chain reaction stable for just a few days, instead of months or years. Which reduces the scale of any power excess to very manageable levels even if you provoked one in a case of gross misconduct - as it happened in Chernobyl or the SL-1 accident.)
But that's just peak power - you have to consider night and day, the angle of the sun, the weather etc. You must further consider the gaps between the collectors. Practical values are more on the order of 10W/m^2 (Andasol in southern Spain - things get much worse even somewhat further north - with clouds being the primary culprit, latitude a not-too-distant second.)
I should have added that in case of the reactor overheating, there is a plug at the lower face of the reactor vessel with a melting point below operating temperature (which must be cooled all the time) - if it fails, either due to overheating or malfunction, the interior of the reactor is drained into the storage tanks. Those are designed to keep them deeply sub-critical and sufficiently cooled. (Even and especially when running at full power.)
I agree that corrosion is a problem and a spill anything but pretty. However, a spill is not the same as blowing up. As to contact with water causing problems, well, just keep water out of the containment - using either gas-driven turbines or a tertiary coolant loop. (That's part of "moderately well designed".)
You mean like solar power or wind power in countries where those are not privileged?
Wherever those are supposedly "successful" there are laws in place that guarantee that all power they generate is paid for - whether it is needed or not. Germany has run out of grid capacity years ago because of that policy. Since 2008 wind power generation has remained stagnant (even fallen by 10%) despite a 25% increase in generation capacity, because there are no power lines between northern and eastern Germany, where most of it is generated, and Southern and Western Germany, where it is needed. Wind turbines then have to be shut down to avoid a grid collapse. (Don't worry, the money keeps flowing, even for electricity not generated.) If they had to actually sell their electricity on an equal footing with everybody else, wind power would collapse.
I'm not even talking about the absurd prices of wind and solar. France shut down the Super Phenix reactor in 1997 when it became clear that its power would cost between 6 ct/kWh initially (running 50% of the time) and about 4ct/kWh (running 80% of the time). Luxurious compared to wind or solar, but too expensive compared to 2-3ct/kWh PWR power plants.
Please tell us how an even moderately well designed molten salt reactor is supposed to blow up. There is no pressure in such a reactor, because no component is gaseous and can't turn into a gas either without triggering the safety release into the storage tanks first. Because the core cannot be compressed in any way, a Bethe-Tait excursion is physically impossible and over-heating will cause the salt to expand and suppress the nuclear reaction without any intervention - even in the case of suicidal staff deactivating all safety mechanisms and pulling out all control rods simultaneously.
So, please, where is a sudden release of energy (aka "blowing up") supposed to come from?
Wrong. It depends on the temperature of the steam used and that temperature depends on the type of reactor. Unlike coal power plants water moderated reactors do not use superheated steam for technical reasons, which limits temperatures. The Advanced Gas-Cooled Reactors as used in Great Britain run at higher temperatures. Reactors using liquid metals (sodium or lead) as coolant run on still higher temperatures, as will molten salt reactors. The difference in water used can easily make up 50%.
Solar thermal is about the worst technology in this respect - About 6l per kWh. Nuclear power (PWR) clocks in at around 3l per kWh, coal plants use about 2l.
And of course you will find the most fervent supporters of Desertec - a project to build solar thermal on a HUGE scale in Northern Africa, well known for such water rich places as Libya or Morocco - among the exact same people who claim that nuclear power in France is unsustainable for lack of cooling water.
And they are merely the worst in 50 years. Meaning, they should have been prepared. Much worse than what we are seeing on TV has happened there in the past. Same goes for NY and Irene or NO and Katrina.
But there haven't been bloody hot summers over the last ten years, yet everybody is talking about global warming - while we're just experiencing natural variation.
But half the current radioactivity of Cesium is Cs-134 with a half-life of 2 years (thus being 15 times as radioactive for equivalent amounts). Which basically reduces the time by 30 years outright. It is known from other sites (Sellafield, Chernobyl) that a lot of the Cs will inevitably be removed by erosion, migrating deeper into the soil and being absorbed by clay minerals - thus not being bio-available (that is, staying in the soil and not being taken up by plants growing in the soil).
Without decontamination we're still talking about decades.
But it's not like Sellafield or Chernobyl, because the problem is limited to Cs. There is no Sr-90, no activation products or Plutonium to speak of (some 0.6Bq/kg were found right next to the power plant - it is not clear whether this is from the powerplant or Cold War residue which has similar concentrations in Japan.)
Warning, almost 2000 pages and 115MB worth of data to download. No, I didn't read it yet, I was merely trying to find a comprehensive source on the topic. Yes, it is not up to date, but it shows the historic development of the field until two years after Chernobyl.
I could have pointed to you to any number of studies of the soil contents of radionuclides, but most of those were pay-walled (a common problem not just in this area) and I hate referring to summaries and abstracts. Search google scholar if you want to see them. But there were several that had an excess which was equivalent to more than 2500Bq of Cs-137 compared to average concentrations when you add up Thorium, Uranium and their decay chain products.
Yes. Although, just to be sure, I by no means imply that there are no areas in Japan with possibly unsafe levels of Cs-137. There are, there should not be and whoever decided not to implement standard safety measures in Fukushima Daiichi that were common for nuclear power plants in general and Mark I containments in particular was a bleeping b@st@rd.
Any non-minor release of radioactive substances is unacceptable. (Coal, natural gas and geothermal, for example, release additional radium, radon, lead-210 etc.pp. Many other activities also release radioactive substances - including cancer treatments and diagnosis. So there must be some point where you must draw the line and say that some small amounts are acceptable. where that is, is debatable - but saying "none" is not.)
All I mean to say is that there are levels of Cs-137 that can be considered safe to be around with by analogy to naturally occurring higher concentrations of radioactive isotopes and their lack of health consequences. Not that you should sprinkle the neighborhood with it.
Slashdot Mirror
140mio tons of maize are being turned into ethanol in the USA alone. That's a quarter of the world maize production. Last year the world was supposedly in shock when Russia had the worst drought in 100 years or so and wheat production fell short by 10mio tons. (Yes, maize is not wheat, but the shortfall of the drought is still negligible in comparison to the amount of food burned.)
... there are people starving in Africa.
Food is meant for eating, not for driving cars!
http://www.worldhunger.org/articles/Learn/world%20hunger%20facts%202002.htm
The consequences of Fukushima are a direct result of the power station being unchanged since the 1970ies, even though it became clear already in that decade, that safety precautions were insufficient. Especially concerning the risk of hydrogen explosions (hydrogen was already a known problem during the Three Mile Island accident in 1979), the lack of autocatalytic recombiners (which prevent them) and the lack of filtered containment vents - which were installed in both Germany and France (which you mention here) in the 1980ies and 90ies, in anticipation of otherwise unacceptable releases during a meltdown.
Well, at least this spelling makes it clear they were not dunked into buckets of dye.
But Desertec doesn't plan to use sea water to cool its turbines - which would be hard to do anyway, because of the way such plants scale. The turbines and thermal storage must be centrally located in the collector array and this array is limited in size. Otherwise losses are too large. Which makes placing the turbines next to the coast impractical, not to mention a lot more expensive.
The 2km^2 demonstration plant Andasol already cost 300mio Euro, delivering about as much electricity as a small conventional 20MW power plant (180GWh per year). The new 12km^2 plant in Morocco, based on the same technology, is going to cost 2bn Euro. Right. Six smaller plants in Spain are cheaper than one big plant in Morocco - so much for claims that larger plants and more experience would decrease costs.
Yes, it's likely. Given that eco-terrorists shot several RPG's at the building during the construction ...
I'm not talking about sodium. I haven't said a word about sodium. It's an entirely different material, they neither belong to the same group of chemicals nor do they contain the same atoms. They don't have the same chemical reactions. And I'm not being dishonest for not talking about the properties of molten Na-metal, when I'm talking about LiF and BeF2 salts. You don't blame people working with concrete for not mentioning the flammability of wooden structures either.
Keep talking to yourself, I'll stop talking to you, that's for sure.
If you read the fourth comment in this thread, which I wrote long before your initial comment, you will find the following:
"As to contact with water causing problems, well, just keep water out of the containment - using either gas-driven turbines or a tertiary coolant loop. (That's part of "moderately well designed".)"
I didn't shift any goal posts, it's just that you're blind to the goal posts I set long ago.
First of all: You don't need steam spin a turbine. In fact, it is more efficient not to use water steam, provided that you have a high enough temperature to begin with. in this case, you can use a Brayton Cycle turbine with CO2 as your working gas.
But even if you insist on using steam turbines, there is nothing to stop you from using two heat exchangers to decouple the (radioactive) coolant flow inside the reactor from the water heated outside of the containment. In this case, if water get in contact with anything hot, it won't be anywhere near the reactor, there won't be any radioactivity involved. It would be a mess, it would be an accident, but not a nuclear one.
I keep reading about things touching water in places where there is no water. Strange.
I don't think you know how a molten salt reactor works. The salt is not just the coolant, it is also the fuel itself. It contains both the Uranium, Plutonium or Thorium (molten salt reactors can use all of them) and the fission products. As the fuel is liquid and directly accessible, fission products can be removed from the reactor every couple of days, instead of leaving fuel rods (including fission products) in the reactor for over a year. This limits their amount to 1-2% at any time. Things that are not in the reactor in the first place, can't get out in an accident.
It also means that the fuel has a much lower power density. Because the fuel only consists of a small fraction of fissle materials and fission products, whereas fuel rods consist mostly of nothing else. They have a high power density, even after shutdown, because the fission products are tightly packed and there is almost a year's worth of them. Which is why they easily heat up and melt unless there is a steady flow of coolant - once molten, there is a small chance for a Bethe-Tait accident - depending on if and how fast the molten core is collapsing, the distribution of absorbing materials in the molten core and how much fissle material it contains.
None of this should happen on a major scale, but why go the risk of even small damage to the reactor vessel aggravating an accident, if you can avoid it outright by using an incompressible liquid with homogeneously dispersed fuel, where any such scenario is physically impossible? (Also, the amount of fissle material is limited to the minimum necessary to keep the chain reaction stable for just a few days, instead of months or years. Which reduces the scale of any power excess to very manageable levels even if you provoked one in a case of gross misconduct - as it happened in Chernobyl or the SL-1 accident.)
But that's just peak power - you have to consider night and day, the angle of the sun, the weather etc. You must further consider the gaps between the collectors. Practical values are more on the order of 10W/m^2 (Andasol in southern Spain - things get much worse even somewhat further north - with clouds being the primary culprit, latitude a not-too-distant second.)
I should have added that in case of the reactor overheating, there is a plug at the lower face of the reactor vessel with a melting point below operating temperature (which must be cooled all the time) - if it fails, either due to overheating or malfunction, the interior of the reactor is drained into the storage tanks. Those are designed to keep them deeply sub-critical and sufficiently cooled. (Even and especially when running at full power.)
I agree that corrosion is a problem and a spill anything but pretty. However, a spill is not the same as blowing up. As to contact with water causing problems, well, just keep water out of the containment - using either gas-driven turbines or a tertiary coolant loop. (That's part of "moderately well designed".)
You mean like solar power or wind power in countries where those are not privileged?
Wherever those are supposedly "successful" there are laws in place that guarantee that all power they generate is paid for - whether it is needed or not. Germany has run out of grid capacity years ago because of that policy. Since 2008 wind power generation has remained stagnant (even fallen by 10%) despite a 25% increase in generation capacity, because there are no power lines between northern and eastern Germany, where most of it is generated, and Southern and Western Germany, where it is needed. Wind turbines then have to be shut down to avoid a grid collapse. (Don't worry, the money keeps flowing, even for electricity not generated.) If they had to actually sell their electricity on an equal footing with everybody else, wind power would collapse.
I'm not even talking about the absurd prices of wind and solar. France shut down the Super Phenix reactor in 1997 when it became clear that its power would cost between 6 ct/kWh initially (running 50% of the time) and about 4ct/kWh (running 80% of the time). Luxurious compared to wind or solar, but too expensive compared to 2-3ct/kWh PWR power plants.
Oh c'mon, that unit is sanity itself!
It's when people start talking about acre-feet per acre (in watering golf courses) that I want to strangle and knock some math into them.
Please tell us how an even moderately well designed molten salt reactor is supposed to blow up. There is no pressure in such a reactor, because no component is gaseous and can't turn into a gas either without triggering the safety release into the storage tanks first. Because the core cannot be compressed in any way, a Bethe-Tait excursion is physically impossible and over-heating will cause the salt to expand and suppress the nuclear reaction without any intervention - even in the case of suicidal staff deactivating all safety mechanisms and pulling out all control rods simultaneously.
So, please, where is a sudden release of energy (aka "blowing up") supposed to come from?
Wrong. It depends on the temperature of the steam used and that temperature depends on the type of reactor. Unlike coal power plants water moderated reactors do not use superheated steam for technical reasons, which limits temperatures. The Advanced Gas-Cooled Reactors as used in Great Britain run at higher temperatures. Reactors using liquid metals (sodium or lead) as coolant run on still higher temperatures, as will molten salt reactors. The difference in water used can easily make up 50%.
Solar thermal is about the worst technology in this respect - About 6l per kWh. Nuclear power (PWR) clocks in at around 3l per kWh, coal plants use about 2l.
And of course you will find the most fervent supporters of Desertec - a project to build solar thermal on a HUGE scale in Northern Africa, well known for such water rich places as Libya or Morocco - among the exact same people who claim that nuclear power in France is unsustainable for lack of cooling water.
And they are merely the worst in 50 years. Meaning, they should have been prepared. Much worse than what we are seeing on TV has happened there in the past. Same goes for NY and Irene or NO and Katrina.
But there haven't been bloody hot summers over the last ten years, yet everybody is talking about global warming - while we're just experiencing natural variation.
They contain nuclear knowledge!
But half the current radioactivity of Cesium is Cs-134 with a half-life of 2 years (thus being 15 times as radioactive for equivalent amounts). Which basically reduces the time by 30 years outright. It is known from other sites (Sellafield, Chernobyl) that a lot of the Cs will inevitably be removed by erosion, migrating deeper into the soil and being absorbed by clay minerals - thus not being bio-available (that is, staying in the soil and not being taken up by plants growing in the soil).
Without decontamination we're still talking about decades.
But it's not like Sellafield or Chernobyl, because the problem is limited to Cs. There is no Sr-90, no activation products or Plutonium to speak of (some 0.6Bq/kg were found right next to the power plant - it is not clear whether this is from the powerplant or Cold War residue which has similar concentrations in Japan.)
In general, if you want to know specific data, it's best to look for it yourself. Most people feel disinclined to do this for other people most of the time. However, you may try:
Radioactivity and health: A history (1988)
http://www.osti.gov/energycitations/servlets/purl/6608787-H6blQd/6608787.pdf
Warning, almost 2000 pages and 115MB worth of data to download. No, I didn't read it yet, I was merely trying to find a comprehensive source on the topic. Yes, it is not up to date, but it shows the historic development of the field until two years after Chernobyl.
I could have pointed to you to any number of studies of the soil contents of radionuclides, but most of those were pay-walled (a common problem not just in this area) and I hate referring to summaries and abstracts. Search google scholar if you want to see them. But there were several that had an excess which was equivalent to more than 2500Bq of Cs-137 compared to average concentrations when you add up Thorium, Uranium and their decay chain products.
Yes. Although, just to be sure, I by no means imply that there are no areas in Japan with possibly unsafe levels of Cs-137. There are, there should not be and whoever decided not to implement standard safety measures in Fukushima Daiichi that were common for nuclear power plants in general and Mark I containments in particular was a bleeping b@st@rd.
Any non-minor release of radioactive substances is unacceptable. (Coal, natural gas and geothermal, for example, release additional radium, radon, lead-210 etc.pp. Many other activities also release radioactive substances - including cancer treatments and diagnosis. So there must be some point where you must draw the line and say that some small amounts are acceptable. where that is, is debatable - but saying "none" is not.)
All I mean to say is that there are levels of Cs-137 that can be considered safe to be around with by analogy to naturally occurring higher concentrations of radioactive isotopes and their lack of health consequences. Not that you should sprinkle the neighborhood with it.