Japan Earthquake: nuclear plants

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So what is your conclusion, nikkkom? Does the corium still need water cooling?
How much water is pumped in today, 100 tons/day? Isn't that too much?
And then, surprise, there are massive radioactive leaks. Doh...

Forced air cooling may be enough.
 
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Forced air cooling may be enough.
For fuel with intact geometry and well planned flow paths - yes.
For the suspected mess - not likely.
 
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Hi,

i have a hard time imagining how the "cooling" works with the injection of the water by Tepco. I mean, nobody knows where the fuel/corium is, but it's very probable that it has relocated outside of the reactor vessel or the containement vessel. It's maybe below the reactor somewhere on or in the basement, and maybe for reactor N°2 somewhere else, in the torus area...

To cool, you need to remove heat, and this is done by a flow of something, in this case of water. But the flow has to be to some degree, to be efficient, in contact with the hot fuel, debris and or corium. Then the question is: how do they manage to create a flow path to reach the hot stuff that is "somewhere" (they don't know where), and probably somewhere down, i mean in a low area which is probably "blind". How then a flow could be created in such an area? I don't know exactly what are the input and ouput point for water circuits on each reactor, but i doubt that the output points can be in places where the flow has REALLY TOUCHED the hot stuff...

Maybe you have some convincing answers and elements that i missed, but really, this supposedly "closed loop" (which is not) water cooling puzzles me...

There might be a flow that cools the hot stuff, but isn't it the groundwater mixed with additional water, with output points that are mainly... leaks to the ocean?

That would explain the increase in contamination in the port, by the way...
 
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i have a hard time imagining how the "cooling" works with the injection of the water by Tepco. I mean, nobody knows where the fuel/corium is, but it's very probable that it has relocated outside of the reactor vessel or the containement vessel. It's maybe below the reactor somewhere on or in the basement, and maybe for reactor N°2 somewhere else, in the torus area...

To cool, you need to remove heat, and this is done by a flow of something, in this case of water. But the flow has to be to some degree, to be efficient, in contact with the hot fuel, debris and or corium. Then the question is: how do they manage to create a flow path to reach the hot stuff that is "somewhere" (they don't know where), and probably somewhere down, i mean in a low area which is probably "blind". How then a flow could be created in such an area?
Hotter water rises, colder water goes down. Thus, if there is a dense heap of warm corium somewhere down there, water will convect around that, and "smear" thermal energy over the entire water volume. The hotter that lump of corium becomes, the more efficient convention is. In a limiting case, water can boil, and thus ensure that temperature stays below 100 C. However, I think such temps are very improbable today.

TEPCO basically injects water into RPV through some surviving piping, and pumps out somewhat warmer water out of turbine building basement (yes, not even from reactor building basement. Water needs to seep from one to another).

No wonder several *tons* of water manage to escape from such a haphazard cooling loop into the ground.
 
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Yes, convection creates of course a natural flow, but i see in fact the current situation more like some hot fuel, debris and or corium sitting somewhere at the bottom of the big messy pool that the buidings and the basements are in fact now: some convection will occur, but i wouldn't call that a circuit loop... They add fresh water, water gets a bit hotter and they remove blindly some of this water so the temperature stays somewhat constant.

In fact Tepco is injecting water from the top but the soil seem to inject even more from the sides and the bottom, and this is called groundwater flow!

Something interesting here that may create some problems with the plan to pump out groundwater (12 wells) and reject it to ocean before it cools the hot stuff and gets contaminated: it seems the groundwater may be already contaminated BEFORE it hits the reactor buildings, probably because of leaks from the storage tanks...

http://www3.nhk.or.jp/nhkworld/english/news/20130912_02.html [Broken]

The operator of the crippled Fukushima Daiichi nuclear plant says it has found rising tritium levels at a monitoring well near a wastewater storage tank.

One of the storage tanks leaked more than 300 tons of highly radioactive water in August. The water is likely to have seeped into the soil.

Tokyo Electric Power Company has since increased the number of monitors to check radioactive materials in groundwater near the tank.

The company says the level of radioactive tritium at one of the wells rose to 64,000 becquerels per liter on Tuesday, more than twice the reading the previous day.

The well is located 20 meters north of the leaking tank. Engineers checked soil taken when the well was dug and found beta radiation of 0.1 millisieverts an hour.

Beta rays are kind of radiation emitted from tritium and other substances.

The operator suspects the leak is spreading but says it doesn't know why as the well is not located near to the groundwater flows. It says most of the contaminated soil around the tank has been removed.

The company initially planned to pump up clean groundwater and release it into the ocean before it passes through heavily contaminated reactors buildings. The finding that the groundwater is already tainted before its reaches the buildings may hamper that plan.
Well, as ABE said, no need to worry about contaminated water, it's under control...
 
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Tritium is yet another red herring here.

Sure, it would be better to not have tritium.
However, the 300000 tons of water in that giant tank farm currently contain far, far worse isotopes (say, Sr-90) in high concentrations. Tritium is almost nothing compared to that.

Yet, again, TEPCO is in a difficult position where even if it would do everything right and would filter all this water to be completely free of all contaminants sans tritium, the usual suspects will scream bloody murder at mere suggestion of releasing this water to the ocean.
"Oh God, horrible tritium with its deadly 18kEv betas!!! We are all going to die!!! Evil corporations are killing us!!!"
 
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However, the 300000 tons of water in that giant tank farm currently contain far, far worse isotopes (say, Sr-90) in high concentrations.
if you count in this document
http://www.tepco.co.jp/nu/fukushima-np/f1/smp/2013/images/south_discharge_130826-1j.pdf
and given that there strontium 60%. in 全β
Approximately 40 thousand terabecquerels of strontium-90. it is 4 times the release of strontium-90 in the accident at Chernobyl.

Given that strontium is much more mobile and toxic cesium (ingestion) in the future, I think it will be a major problem.
 
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It seems that beyond reality, communication is going to become more important to describe this reality!

TEPCO official: Leakage 'not under control'

A senior official from the Tokyo Electric Power Company has acknowledged that the radioactive water leakage at the crippled Fukushima Daiichi plant is not under control.

The government's top spokesman later said the assessment does not contradict Prime Minister Shinzo Abe's statement, delivered internationally, that the situation in Fukushima is under control.

TEPCO official Kazuhiko Yamashita was speaking at a hearing on Friday in Koriyama City, Fukushima Prefecture. The session was organized by the opposition Democratic Party, with officials from the government and TEPCO taking part.

Yamashita apologized for the radioactive water leaks, saying that what's happening now goes beyond TEPCO's assumptions.
A lawmaker asked if Yamashita agrees with Abe's statement made last Saturday at a general meeting of the International Olympic Committee in Buenos Aires.

Yamashita replied that he believes the current situation is not under control.

Chief Cabinet Secretary Yoshihide Suga later told a news conference that he heard Yamashita made the comment after being pressed several times for an answer.

Suga said government officials have confirmed with TEPCO that Yamashita was speaking in reference to independent incidents, including a leak of radioactive wastewater from a storage tank at the plant.

Suga said that even if such independent incidents take place, multi-layered steps will be taken to prevent the radioactive water from contaminating the ocean.

Suga said it is true that tainted water has leaked from a tank. But he said workers' patrols of storage tanks have been increased from once to 4 times per day, as part of all-out efforts to urgently deal with the problem.
http://www3.nhk.or.jp/nhkworld/english/news/20130913_36.html [Broken]

And also read his article:
http://ex-skf.blogspot.fr/2013/09/contaminated-water-problems-at.html

And finally, did others here remarked that NHK world has removed since some days the Tag + link that was since the very beginning on the right side (below "Now on air") of their site, directly linking to data from Tepco about Fukushima?

I remarked it was around the date of the Olympic games announcement...

Communication is the way to "present" datas. Is it time to have datas not too visible?
 
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Also, i read in french here that steam has been seen again Friday morning (8h00 in the morning in Japan) above reactor N° 3, and that was an information from TEPCO and that it was seen from a camera (probably Tepco webcam).

http://www.lemonde.fr/planete/article/2013/09/13/fukushima-de-la-vapeur-reapparait-au-dessus-du-reacteur-3_3476943_3244.html

But i don't see any info about that in english elsewhere (maybe some in japanese?)?

Any news about this? Was it filmed and saved somewhere on the net?
 
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http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130913_01-e.pdf

What's most interesting:
- graph on page 24: the water flow direction might be even now reversed, it's flowing in from the ocean, at least at that point
- first graph on page 17
Another update from TEPCO and yet again, absolutely nothing covered other than the water issues. Status of the clean-up of the units? Fuel removal from Unit 4 SFP? Removal of the Unit 1 cover? Location of the cores? And on and on.

Thanks for posting.
 
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I have wasted a few minutes of my life to skim-read mr Barrett's creation. Fluff and handwavium.
 
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Another update from TEPCO and yet again, absolutely nothing covered other than the water issues. Status of the clean-up of the units? Fuel removal from Unit 4 SFP? Removal of the Unit 1 cover? Location of the cores? And on and on.
The water issues are, which actually most concerned by 'the public'.

OW no (really) new information about the other topics. U3 top clean up is almost down to the smaller fragments, but the operation is suspended due the steam from under the ceiling crane beam. They are planning the decontamination and the shielding.

U4 SFP cleanup work might start in the next month if everything works fine. Also that month they plan to go on with the 'core lookup' endoscopic missions.

I don't know about any plan to remove the cover of U1.

But all this is just based on small hints dispersed all over some dozen documents.
 
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Ah yes. That's why he's advocating the dumping of contaminated water. Okay.
Well... Once they will be able to remove Sr (and some other elements) they should dump that water somewhere. Even if I prefer places where it'll be isolated for some time (this includes some natural reservoirs deep below), it would do practically nothing even if they mix it well in the ocean.


But... ... we know about the Tritium concentration of that water, but what about Deuterium? I wonder, would it worth to process (and sell) it?
 
But... ... we know about the Tritium concentration of that water, but what about Deuterium? I wonder, would it worth to process (and sell) it?
I guess there isn't significant difference in concentration of D compared to natural water.
 
Another update from TEPCO and yet again, absolutely nothing covered other than the water issues. Status of the clean-up of the units? Fuel removal from Unit 4 SFP? Removal of the Unit 1 cover? Location of the cores? And on and on.

Thanks for posting.
Others have pointed out documents that give some clue as to timescales for some of these tasks, though I'd have to go back over a mess of documents to fill in some of the remaining gaps. I'll return to some in the coming hours or days but for now I will just deal with core location surveys.

Reactor 3 needs more decontamination inside the reactor building before they do any useful surveys. We hear very little about reactor 1. Reactor 2 is where there has been the most progress, including in recent months.

The last thing we learnt about reactor 2 is not many pages ago on this thread, with the last survey revealing a rate of 36 Sv/h just outside the pedestal opening. But now they have to look at the results & tricky operating conditions encountered during that survey in order to plan the next survey which will hopefully go inside the pedestal area and give a better idea about core location.

One other thing I may have learnt from that survey, if all the documents & diagrams were accurate, is that the location of the full 'door' into the pedestal area, is to the south-east. This is based on an assumption that this door, which was of interest to those wondering about molten core flow or splashing outside of the pedestal area, is opposite the pedestal opening that they got close to in this survey (this surveyed opening is more like a window than a door, and is used to replace control rod drivers).

Anyway, when trying to guesstimate core location at this stage, apart from that 36 Sv/h figure for reactor 2, and the various theoretical analysis done with models, I think the only other thing we have to go on is the state of the torus rooms at the three reactors. It is tempting to suggest that radiation dose levels in the torus rooms of reactors 2 & 3 are not spectacular enough to promote theories about core migrating away from the drywell containment in these reactors. But the very limited surveying possible at reactor 1 torus room, along with the levels of radiation measured there, may hint at a more interesting story for that reactors core. But I expect it would be grossly premature to make any conclusions based on this, its just what I'm throwing out there during the long wait for more substantial data. Thoughts more than welcome, including whether the 36 Sv/h reading near the pedestal opening of reactor 2 is the sort of reading we might expect if most of the core was either in the bottom of the RPV or the pedestal area of this reactor.
 

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