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But Plan A had failed - cooling systems down or additional clean water unavailable - so

Plan B came into effect. This is what it looks like happened:
In order to prevent a core meltdown, the operators started to use sea   water to cool the core. I am not quite sure if they flooded our pressure cooker with it (the second containment), or if they flooded the third containment, immersing the pressure cooker. But that is not relevant for us.

The point is that the nuclear fuel has now been cooled down. Because the chain reaction has been stopped a long time ago, there is only very little residual heat being produced now. The large amount of cooling water that has been used is sufficient to take up that heat. Because it is a lot of water, the core does not produce sufficient heat any more to produce any significant pressure. Also, boric acid has been added to the seawater. Boric acid is "liquid control rod". Whatever decay is still going on, the Boron will capture the neutrons and further speed up the cooling down of the core.

The plant came close to a core meltdown. Here is the worst-case scenario that was avoided: If the seawater could not have been used for treatment, the operators would have continued to vent the water steam   to avoid pressure buildup. The third containment would then have been   completely sealed to allow the core meltdown to happen without   releasing radioactive material. After the meltdown, there would have   been a waiting period for the intermediate radioactive materials to   decay inside the reactor, and all radioactive particles to settle on a   surface inside the containment. The cooling system would have been   restored eventually, and the molten core cooled to a manageable   temperature. The containment would have been cleaned up on the inside.   Then a messy job of removing the molten core from the containment would have begun, packing the (now solid again) fuel bit by bit into   transportation containers to be shipped to processing plants. Depending   on the damage, the block of the plant would then either be repaired or dismantled.

Now, where does that leave us?

The plant is safe now and will stay safe.

Japan is looking at an INES Level 4 Accident: Nuclear accident with   local consequences. That is bad for the company that owns the plant,   but not for anyone else.
Some radiation was released when the pressure vessel was vented. All radioactive isotopes from the activated steam have gone (decayed). A very small amount of Cesium was released, as well as Iodine. If you were sitting on top of the plants' chimney when they were venting, you should probably give up smoking to return to your former life expectancy. The Cesium and Iodine isotopes were carried out to the sea and will never be seen again.

There was some limited damage to the first containment. That means   that some amounts of radioactive Cesium and Iodine will also be   released into the cooling water, but no Uranium or other nasty stuff   (the Uranium oxide does not "dissolve" in the water). There are   facilities for treating the cooling water inside the third   containment. The radioactive Cesium and Iodine will be removed   there   and eventually stored as radioactive waste in terminal storage.

The   seawater used as cooling water will be activated to some degree.    Because the control rods are fully inserted, the Uranium chain reaction is not happening. That means the "main" nuclear reaction is not happening, thus not contributing to the activation. The intermediate radioactive materials (Cesium and Iodine) are also almost gone at this stage, because the Uranium decay was stopped a long time ago. This further reduces the activation. The bottom line is that there will be some low level of activation of the seawater, which will also be removed by the treatment facilities.

The seawater will then be replaced over time with the "normal" cooling   water The reactor core will then be   dismantled and transported to a   processing facility, just like during a   regular fuel change.

Fuel rods and the entire plant will be checked for potential damage. This will take about 4-5 years.

The   safety systems on all Japanese plants will be upgraded to   withstand a   9.0 earthquake and tsunami (or worse) I believe the most   significant   problem will be a prolonged power shortage. About half of   Japan 's   nuclear reactors will probably have to be inspected, reducing the   nation's power generating capacity by 15%. This will probably be covered   by running gas power plants that are usually only used for peak loads   to cover some of the base load as well. That will increase your   electricity bill, as well as lead to potential power shortages during   peak demand, in Japan .

If you want to stay informed, please forget the usual media outlets and consult the following websites:
http://www.world-nuclear-news.org/RS_Battle_to_stabilise_earthquake_reac...
http://www.world-nuclear-news.org/RS_Venting_at_Fukushima_Daiichi_3_1303...
http://bravenewclimate.com/2011/03/12/japan-nuclear-earthquake/
http://ansnuclearcafe.org/2011/03/11/media-updates-on-nuclear-power-stat...

<blockquote data-quote="Agentm" data-source="post: 619268" data-attributes="member: 5119">But Plan A had failed - cooling systems down&nbsp; or additional clean&nbsp; water unavailable - so Plan B came into effect.&nbsp; This is what it looks&nbsp; like happened:&nbsp;In order to prevent a core&nbsp; meltdown, the operators started to use&nbsp; sea&nbsp;&nbsp; water to cool the core. I am&nbsp; not quite sure if they flooded our&nbsp; &nbsp; pressure cooker with it (the second&nbsp; containment), or if they flooded&nbsp; &nbsp; the third containment, immersing the&nbsp; pressure cooker. But that is not&nbsp; &nbsp; relevant for us.&nbsp;The point is&nbsp; that the nuclear fuel has now been cooled down. Because&nbsp; &nbsp; the chain&nbsp; reaction has been stopped a long time ago, there is only&nbsp; &nbsp; very little&nbsp; residual heat being produced now. The large amount of&nbsp; &nbsp; cooling water that&nbsp; has been used is sufficient to take up that heat.&nbsp; &nbsp; Because it is a lot&nbsp; of water, the core does not produce sufficient heat&nbsp; &nbsp; any more to produce&nbsp; any significant pressure. Also, boric acid has&nbsp; &nbsp; been added to the&nbsp; seawater. Boric acid is &quot;liquid control rod&quot;.&nbsp; &nbsp; Whatever decay is still&nbsp; going on, the Boron will capture the neutrons&nbsp; &nbsp; and further speed up the&nbsp; cooling down of the core.&nbsp;The plant came close to a core&nbsp; meltdown. Here is the worst-case&nbsp; &nbsp; scenario that was avoided: If the&nbsp; seawater could not have been used for&nbsp; &nbsp; treatment, the operators would&nbsp; have continued to vent the water&nbsp; steam&nbsp;&nbsp; to avoid pressure buildup. The&nbsp; third containment would then&nbsp; have been&nbsp;&nbsp; completely sealed to allow the&nbsp; core meltdown to happen&nbsp; without&nbsp;&nbsp; releasing radioactive material. After&nbsp; the meltdown, there&nbsp; would have&nbsp;&nbsp; been a waiting period for the&nbsp; intermediate radioactive&nbsp; materials to&nbsp;&nbsp; decay inside the reactor, and all&nbsp; radioactive particles&nbsp; to settle on a&nbsp;&nbsp; surface inside the containment. The&nbsp; cooling system&nbsp; would have been&nbsp;&nbsp; restored eventually, and the molten core&nbsp; cooled to a&nbsp; manageable&nbsp;&nbsp; temperature. The containment would have been&nbsp; cleaned up on&nbsp; the inside.&nbsp;&nbsp; Then a messy job of removing the molten core&nbsp; from the&nbsp; containment&nbsp; would&nbsp; have begun, packing the (now solid again)&nbsp; fuel bit&nbsp; by bit into&nbsp;&nbsp; transportation containers to be shipped to&nbsp; processing&nbsp; plants. Depending&nbsp;&nbsp; on the damage, the block of the plant would&nbsp; then&nbsp; either be repaired&nbsp; or&nbsp; dismantled.&nbsp;Now, where does that leave us?&nbsp;The plant is safe now and will stay safe.Japan&nbsp; is looking at an&nbsp; INES Level 4 Accident: Nuclear accident with&nbsp;&nbsp; local&nbsp; consequences. That&nbsp; is bad for the company that owns the plant,&nbsp;&nbsp; but not&nbsp; for anyone else.Some&nbsp; radiation was released when the pressure vessel&nbsp; was vented. All&nbsp; &nbsp; radioactive isotopes from the activated steam have gone&nbsp; (decayed). A&nbsp; &nbsp; very small amount of Cesium was released, as well as&nbsp; Iodine. If you&nbsp; &nbsp; were sitting on top of the plants&#039; chimney when they were&nbsp; venting, you&nbsp; &nbsp; should probably give up smoking to return to your former&nbsp; life&nbsp; &nbsp; expectancy. The Cesium and Iodine isotopes were carried out to the&nbsp; sea&nbsp; &nbsp; and will never be seen again.There was some limited damage to&nbsp; the&nbsp; first containment. That means&nbsp;&nbsp; that some amounts of radioactive&nbsp; Cesium&nbsp; and Iodine will also be&nbsp;&nbsp; released into the cooling water, but no&nbsp; Uranium&nbsp; or other nasty stuff&nbsp;&nbsp; (the Uranium oxide does not &quot;dissolve&quot; in&nbsp; the&nbsp; water). There are&nbsp;&nbsp; facilities for treating the cooling water inside&nbsp; the&nbsp; third&nbsp;&nbsp; containment. The radioactive Cesium and Iodine will be removed&nbsp;&nbsp; there&nbsp;&nbsp; and eventually stored as radioactive waste in terminal storage.The&nbsp;&nbsp; seawater used as cooling water will be activated to some degree.&nbsp; &nbsp;&nbsp; Because the control rods are fully inserted, the Uranium chain&nbsp; reaction&nbsp; &nbsp; is not happening. That means the &quot;main&quot; nuclear reaction is&nbsp; not&nbsp; &nbsp; happening, thus not contributing to the activation. The&nbsp; intermediate&nbsp; &nbsp; radioactive materials (Cesium and Iodine) are also&nbsp; almost gone at this&nbsp; &nbsp; stage, because the Uranium decay was stopped a&nbsp; long time ago. This&nbsp; &nbsp; further reduces the activation. The bottom line&nbsp; is that there will be&nbsp; &nbsp; some low level of activation of the seawater,&nbsp; which will also be removed&nbsp; &nbsp; by the treatment facilities.The seawater will then be replaced&nbsp; over&nbsp; time with the &quot;normal&quot; cooling&nbsp;&nbsp; water The reactor core will then be&nbsp;&nbsp; dismantled and transported to a&nbsp;&nbsp; processing facility, just like during a&nbsp;&nbsp; regular fuel change.Fuel rods and the entire plant will be checked for potential damage. This will take about 4-5 years.The&nbsp;&nbsp; safety systems on all Japanese plants will be upgraded to&nbsp;&nbsp; withstand a&nbsp;&nbsp; 9.0 earthquake and tsunami (or worse) I believe the most&nbsp;&nbsp; significant&nbsp;&nbsp; problem will be a prolonged power shortage. About half of&nbsp;&nbsp; Japan &#039;s&nbsp;&nbsp; nuclear reactors will probably have to be inspected,&nbsp; reducing&nbsp; the&nbsp;&nbsp; nation&#039;s power generating capacity by 15%. This will&nbsp; probably be&nbsp; covered&nbsp;&nbsp; by running gas power plants that are usually only&nbsp; used for&nbsp; peak loads&nbsp;&nbsp; to cover some of the base load as well. That&nbsp; will increase&nbsp; your&nbsp;&nbsp; electricity bill, as well as lead to potential&nbsp; power shortages&nbsp; during&nbsp;&nbsp; peak demand, in Japan .If you want to stay informed, please forget the usual media outlets and consult the following websites:&nbsp;<a href="http://www.world-nuclear-news.org/RS_Battle_to_stabilise_earthquake_reactors_1203111.html" target="_blank">http://www.world-nuclear-news.org/RS_Battle_to_stabilise_earthquake_reac...</a><a href="http://www.world-nuclear-news.org/RS_Venting_at_Fukushima_Daiichi_3_1303111.html" target="_blank">http://www.world-nuclear-news.org/RS_Venting_at_Fukushima_Daiichi_3_1303...</a><a href="http://bravenewclimate.com/2011/03/12/japan-nuclear-earthquake/" target="_blank">http://bravenewclimate.com/2011/03/12/japan-nuclear-earthquake/</a><a href="http://ansnuclearcafe.org/2011/03/11/media-updates-on-nuclear-power-stations-in-japan/" target="_blank">http://ansnuclearcafe.org/2011/03/11/media-updates-on-nuclear-power-stat...</a></blockquote>

[QUOTE="Agentm, post: 619268, member: 5119"] But Plan A had failed - cooling systems down or additional clean water unavailable - so Plan B came into effect. This is what it looks like happened: In order to prevent a core meltdown, the operators started to use sea water to cool the core. I am not quite sure if they flooded our pressure cooker with it (the second containment), or if they flooded the third containment, immersing the pressure cooker. But that is not relevant for us. The point is that the nuclear fuel has now been cooled down. Because the chain reaction has been stopped a long time ago, there is only very little residual heat being produced now. The large amount of cooling water that has been used is sufficient to take up that heat. Because it is a lot of water, the core does not produce sufficient heat any more to produce any significant pressure. Also, boric acid has been added to the seawater. Boric acid is "liquid control rod". Whatever decay is still going on, the Boron will capture the neutrons and further speed up the cooling down of the core. The plant came close to a core meltdown. Here is the worst-case scenario that was avoided: If the seawater could not have been used for treatment, the operators would have continued to vent the water steam to avoid pressure buildup. The third containment would then have been completely sealed to allow the core meltdown to happen without releasing radioactive material. After the meltdown, there would have been a waiting period for the intermediate radioactive materials to decay inside the reactor, and all radioactive particles to settle on a surface inside the containment. The cooling system would have been restored eventually, and the molten core cooled to a manageable temperature. The containment would have been cleaned up on the inside. Then a messy job of removing the molten core from the containment would have begun, packing the (now solid again) fuel bit by bit into transportation containers to be shipped to processing plants. Depending on the damage, the block of the plant would then either be repaired or dismantled. Now, where does that leave us? The plant is safe now and will stay safe. Japan is looking at an INES Level 4 Accident: Nuclear accident with local consequences. That is bad for the company that owns the plant, but not for anyone else. Some radiation was released when the pressure vessel was vented. All radioactive isotopes from the activated steam have gone (decayed). A very small amount of Cesium was released, as well as Iodine. If you were sitting on top of the plants' chimney when they were venting, you should probably give up smoking to return to your former life expectancy. The Cesium and Iodine isotopes were carried out to the sea and will never be seen again. There was some limited damage to the first containment. That means that some amounts of radioactive Cesium and Iodine will also be released into the cooling water, but no Uranium or other nasty stuff (the Uranium oxide does not "dissolve" in the water). There are facilities for treating the cooling water inside the third containment. The radioactive Cesium and Iodine will be removed there and eventually stored as radioactive waste in terminal storage. The seawater used as cooling water will be activated to some degree. Because the control rods are fully inserted, the Uranium chain reaction is not happening. That means the "main" nuclear reaction is not happening, thus not contributing to the activation. The intermediate radioactive materials (Cesium and Iodine) are also almost gone at this stage, because the Uranium decay was stopped a long time ago. This further reduces the activation. The bottom line is that there will be some low level of activation of the seawater, which will also be removed by the treatment facilities. The seawater will then be replaced over time with the "normal" cooling water The reactor core will then be dismantled and transported to a processing facility, just like during a regular fuel change. Fuel rods and the entire plant will be checked for potential damage. This will take about 4-5 years. The safety systems on all Japanese plants will be upgraded to withstand a 9.0 earthquake and tsunami (or worse) I believe the most significant problem will be a prolonged power shortage. About half of Japan 's nuclear reactors will probably have to be inspected, reducing the nation's power generating capacity by 15%. This will probably be covered by running gas power plants that are usually only used for peak loads to cover some of the base load as well. That will increase your electricity bill, as well as lead to potential power shortages during peak demand, in Japan . If you want to stay informed, please forget the usual media outlets and consult the following websites: [URL="http://www.world-nuclear-news.org/RS_Battle_to_stabilise_earthquake_reactors_1203111.html"]http://www.world-nuclear-news.org/RS_Battle_to_stabilise_earthquake_reac...[/URL] [URL="http://www.world-nuclear-news.org/RS_Venting_at_Fukushima_Daiichi_3_1303111.html"]http://www.world-nuclear-news.org/RS_Venting_at_Fukushima_Daiichi_3_1303...[/URL] [URL]http://bravenewclimate.com/2011/03/12/japan-nuclear-earthquake/[/URL] [URL="http://ansnuclearcafe.org/2011/03/11/media-updates-on-nuclear-power-stations-in-japan/"]http://ansnuclearcafe.org/2011/03/11/media-updates-on-nuclear-power-stat...[/URL] [/QUOTE]

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