Nuclear Reactors Hit By Earthquake In Japan
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kunkmiester
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Thus far the only true failure I can see here is the hydrogen venting issue that caused the explosion. Everything else from what I've read has worked well, even if you have one or two piles of half melted uranium. The only real question I have is if the elevated radiation levels are from radioactive stuff leaking/venting out, or is it just because you have a partially breached containment system?
This is mostly a condemnation of envirowackoes, and overregulation. These reactors probably should never have been built--IIRC there were safer designs available at the time. At the least, it should have been much easier to build better reactors to replace them much earlier, alleviating the risk, though it sounds like the only real issue here was the power loss. One of the comments on the Cringely article mentioned a convection based cooling backup that didn't need any power at all.
This is mostly a condemnation of envirowackoes, and overregulation. These reactors probably should never have been built--IIRC there were safer designs available at the time. At the least, it should have been much easier to build better reactors to replace them much earlier, alleviating the risk, though it sounds like the only real issue here was the power loss. One of the comments on the Cringely article mentioned a convection based cooling backup that didn't need any power at all.
Evil is evil, no matter how small
Yes, at this point, the radioactivty released is minor. But please note that the fuel assys have been breached, and this in turn put Fuel Products into the Reactor Vessel. Any venting done after the Zircalloy failures would have included FP.
However, the bulk (99.99999%) of the core fuel material remains inside the Vessel. The flooding will contain any further release.
It is a validation of the designs, with the graphic exception (IMHO) of the H2 controls.
However, the bulk (99.99999%) of the core fuel material remains inside the Vessel. The flooding will contain any further release.
It is a validation of the designs, with the graphic exception (IMHO) of the H2 controls.
I don't know if there was a design failure (except the H2 explosion, that may be), or operator failure, or simply a predictable but statistically unlikely failure based on the magnitude of the Earthquake. The shaking apparently lasted several minutes and moved everything (the entire island) several meters. I speculate that the tsunami itself should not have caused a problem. Surly, a 10 meter sea wall would be a conservative element in the design of these shore based reactors in Japan.
I have heard that diesel generator(s?) failed. That seems a likely single point failure that should have been redundant. Possibly even a passive steam powered turbine to provide backup plant power so long as there was heat and water available in the reactor building to cool the shut down reactor- so long as it retained enough residual heat in the core to continue production of steam. This is apparently a design element in some reactors.
I suspect the earthquake induced damage was much more severe than a simple failure of a diesel generator startup. Multiple water tank, water pipe, steam pipe ruptures, jammed valves, etc seems likely.
Finally, the maintenance and reliability of systems in these old plants may have been lagging.
PS: The use of boron in the cooling water to poison neutron production, suggests that the reactors may not have been adequately shut down (control rods inserted). The boron also might be used (?) if partial meltdown was expected, with the fissile uranium accumulating in a more uranium dense puddle than what would be seen if the fuel rods remained mostly intact and in their proper positions. Or, it occurs to me that the aluminum control rods might melt much earlier than the more resistant fuel rods, so that the neutron dampening of the control rods would be lost as the aluminum pools in the bottom of the reactor. For that matter, if the temperature climbs well above 2,000 degrees, would the melting aluminum still be protected by the normal thin layer of aluminum oxide that forms on solid aluminum, or would the reactive aluminum be exposed to very hot steam? That would make a very good explosive in itself. That is how fuel- air explosives work- fine aluminum powder without the protective oxide coating dispersed in air and ignited. The aluminum might not explode in a reactor, but I could see of the aluminum reacting more gradually with the steam to produce Al. oxide, and additional hydrogen gas. This may be a red haring, as molten aluminum in a foundry doesn't burn (like magnesium does). Then again, it will burn if hot enough(like in a destroyed armored vehicle). Of course steel will burn also, if you get it hot enough in the presence of oxygen.
Dan Tibbets
I have heard that diesel generator(s?) failed. That seems a likely single point failure that should have been redundant. Possibly even a passive steam powered turbine to provide backup plant power so long as there was heat and water available in the reactor building to cool the shut down reactor- so long as it retained enough residual heat in the core to continue production of steam. This is apparently a design element in some reactors.
I suspect the earthquake induced damage was much more severe than a simple failure of a diesel generator startup. Multiple water tank, water pipe, steam pipe ruptures, jammed valves, etc seems likely.
Finally, the maintenance and reliability of systems in these old plants may have been lagging.
PS: The use of boron in the cooling water to poison neutron production, suggests that the reactors may not have been adequately shut down (control rods inserted). The boron also might be used (?) if partial meltdown was expected, with the fissile uranium accumulating in a more uranium dense puddle than what would be seen if the fuel rods remained mostly intact and in their proper positions. Or, it occurs to me that the aluminum control rods might melt much earlier than the more resistant fuel rods, so that the neutron dampening of the control rods would be lost as the aluminum pools in the bottom of the reactor. For that matter, if the temperature climbs well above 2,000 degrees, would the melting aluminum still be protected by the normal thin layer of aluminum oxide that forms on solid aluminum, or would the reactive aluminum be exposed to very hot steam? That would make a very good explosive in itself. That is how fuel- air explosives work- fine aluminum powder without the protective oxide coating dispersed in air and ignited. The aluminum might not explode in a reactor, but I could see of the aluminum reacting more gradually with the steam to produce Al. oxide, and additional hydrogen gas. This may be a red haring, as molten aluminum in a foundry doesn't burn (like magnesium does). Then again, it will burn if hot enough(like in a destroyed armored vehicle). Of course steel will burn also, if you get it hot enough in the presence of oxygen.
Dan Tibbets
Last edited by D Tibbets on Mon Mar 14, 2011 12:43 am, edited 1 time in total.
To error is human... and I'm very human.
If that is true, that seems like a gross and obvious design flaw.Skipjack wrote:Dan, from what I heard (not official), the diesel generators failed because they were under water after the Tsunami. Diesel engines dont work under water.
It reminds me of the water pumps in New Orleans that could pump away a large amount of water back over the dikes. Of course they did not work when the pumps themselves (not just their intakes) were submerged in water.
Dan Tibbets
To error is human... and I'm very human.
Dan,
The Control Rods are normally made out of Halfnium, to my knowledge Aluminium is not used in the primary system for many reasons.
The backup generators are backed up by batteries. However, the batteries exist only to allow Diesel trouble shoot, or to get offsite trailer mounted units on site. The batteries onlhy last about 8 hours (or less). The Decay Heat problem runs over about a week, with the worst of it being the first two days. It is a simple exponential decay curve.
The design issue that will need to be reviewed in detail is for earlier generation BWRs and PWRs regarding Primary Relief venting and H2 mitigation. The accepted concepts appear to have failed (in a big way). The current (old) idea is to vent into Suppression Pools. The steam is condensed, and the H2 gas is suppossed to combine with O2 in the water. This does not happen, as evidenced. The other issue is that the Reliefs are situated inside the Containment, and thus the explosion more thatn likely breached the Containment. However, the Reactor Vessel itself remains intact within the now open vice closed bucket of the Containment/Building. The Containment itself is physically part of the building structure. Given that the top of the building is gone, and that the early BWR designs have the Suppresion Pools in the bottom of the containment, odds are the blast breached up through the top of the Containment. This is a serious design flaw in older plants. The newer designs have more in regards to Loss of Coolant Accidents by gravity deluge and H2 control.
The bottom line here is that if the plant failed in the way I am describing, you currently have Primary Coolant and Fuel Product contaminated fluids residing in the Containment Structure of the Building that is currently open to Atmosphere. Also, when the plant popped, there was a violent ejection of Primary Coolant and Fuel Product contaminated effluent into the atmosphere. This is what I maintain the Japanese are not saying, but talking around right now.
Boron: The Boron Kill is a planned last ditch. It is used when Geometry is violated, or imminent. I am sure the rods inserted just fine. The issue was control of Decay Heat and the failure of Residual Heat Removal systems, to include the emergency cooling plan. All plants revert to water flooding and Boron at the end of all else. In this case they will have flooded both the vessel and containment with water. The follow on drama will be making sure the containment water does not escape, and contaminate the plant grounds. Anything going inside the Containment is now considered contaminated by procedure (and probable reality).
They are left with essentially two choices at this point. Complete Entombment (Cherynobl) or Reactor Vessel with Core removal to a waste disposal site, and Entombment of the remaining plant (TMI-2).
The Control Rods are normally made out of Halfnium, to my knowledge Aluminium is not used in the primary system for many reasons.
The backup generators are backed up by batteries. However, the batteries exist only to allow Diesel trouble shoot, or to get offsite trailer mounted units on site. The batteries onlhy last about 8 hours (or less). The Decay Heat problem runs over about a week, with the worst of it being the first two days. It is a simple exponential decay curve.
The design issue that will need to be reviewed in detail is for earlier generation BWRs and PWRs regarding Primary Relief venting and H2 mitigation. The accepted concepts appear to have failed (in a big way). The current (old) idea is to vent into Suppression Pools. The steam is condensed, and the H2 gas is suppossed to combine with O2 in the water. This does not happen, as evidenced. The other issue is that the Reliefs are situated inside the Containment, and thus the explosion more thatn likely breached the Containment. However, the Reactor Vessel itself remains intact within the now open vice closed bucket of the Containment/Building. The Containment itself is physically part of the building structure. Given that the top of the building is gone, and that the early BWR designs have the Suppresion Pools in the bottom of the containment, odds are the blast breached up through the top of the Containment. This is a serious design flaw in older plants. The newer designs have more in regards to Loss of Coolant Accidents by gravity deluge and H2 control.
The bottom line here is that if the plant failed in the way I am describing, you currently have Primary Coolant and Fuel Product contaminated fluids residing in the Containment Structure of the Building that is currently open to Atmosphere. Also, when the plant popped, there was a violent ejection of Primary Coolant and Fuel Product contaminated effluent into the atmosphere. This is what I maintain the Japanese are not saying, but talking around right now.
Boron: The Boron Kill is a planned last ditch. It is used when Geometry is violated, or imminent. I am sure the rods inserted just fine. The issue was control of Decay Heat and the failure of Residual Heat Removal systems, to include the emergency cooling plan. All plants revert to water flooding and Boron at the end of all else. In this case they will have flooded both the vessel and containment with water. The follow on drama will be making sure the containment water does not escape, and contaminate the plant grounds. Anything going inside the Containment is now considered contaminated by procedure (and probable reality).
They are left with essentially two choices at this point. Complete Entombment (Cherynobl) or Reactor Vessel with Core removal to a waste disposal site, and Entombment of the remaining plant (TMI-2).
Frankly, this really is ridiculous.Giorgio wrote:The reactor was designed to withstand an earthquake magnitude 7.5. I have been hearing all the day journalists stating that this is a proof that nuclear reactors are not safe.....
With so many dead by tsunami, nobody was killed by those nukes. There were 300 dead in chemical plant exploding. I guess what went from that plant during the explosion was not very healthy stuff indeed. But nobody suggests that chemical plants are too dangerous and should be closed worldwide...
So far, those nuclear plants hold quite well, given conditions. No deads, not much radiation escaped. I would say they should rather by used to showcase the safety of nuclear plants.
If my information is correct, then the plant was built to widthstand a quake with the strength of 8.2 on the Richter Scale. However the quake was a 9.0. Since the Richter Scale is 10 base logarithmic, it was thus 8 times as strong and the reactor is STILL standing and very little has actually happened. Further the plant was built to widthstand a Tsunami with a 6 meters high wave, the wave however was more than 7 meters (almost 8?) high. I think that people are just not grasping the scale of the actual desaster. This earth quake was much, much stronger than anything anybody ever predicted to happen.
Nobody is blaming the authorities for letting people live that near to the coasts, where thousands have died...
So far, nobody is confirmed dead as a result of the nuclear accidents (and I dont really want to call them that, but for the lack of a better word).
Nobody is blaming the authorities for letting people live that near to the coasts, where thousands have died...
So far, nobody is confirmed dead as a result of the nuclear accidents (and I dont really want to call them that, but for the lack of a better word).