Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[zapperzero]

The blowers of the standby gas treatment system haven't worked since the blackout, so they aren't going to push anything up the stacks.

It's not like there isn't a permanent pressure differential between the bottom and the top of the stacks. I don't know if they are isolated or not, though.

 

[joewein]

It's not like there isn't a permanent pressure differential between the bottom and the top of the stacks.

Only if they are hot inside. Are they?

 

[zapperzero]

Only if they are hot inside. Are they?

Huh? No. It happens because they are quite tall and because the wind is faster at altitude.

 

[CaptD]

Anybody seen this site before, seems to have "new" info:
http://www.houseoffoust.com/fukushima/fukushima.html

 

[Rive]

Here is this new handout: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110916_01-e.pdf

Can somebody please explain it for me?

Ps.: They have a new core cooling plan: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110916_02-e.pdf

 

[SteveElbows]

Anybody seen this site before, seems to have "new" info:
http://www.houseoffoust.com/fukushima/fukushima.html

Discussed here plenty in the past, not so much recently due to a lack of new material.

In my opinion the site was only useful when people were craving imagery, understanding of plant layout etc. But a somewhat hysterical interpretation of certain images, including faulty and credibility-eroding speculation about various 'smoke' events on the webcam, and fact-free jumping to conclusion about reactor 4 building 'leaning', significantly reduced the use that those with a scientific interest have for that site.

 

[SteveElbows]

Here is this new handout: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110916_01-e.pdf

Can somebody please explain it for me?

I can only provide a simple interpretation at this stage.

They have tried to learn more about the state of the bottom of reactor 1 vessel by using the system that tells them about the position of the control rods. But because they can't be sure what causes bad results, e.g. is it just wiring damaged or a more substantial destruction of some control rods, it seems hard to draw solid conclusions.

 

[zapperzero]

Ps.: They have a new core cooling plan: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110916_02-e.pdf

New cooling plan is: they have increased water injection rates, they plan on increasing them further via core spray system and have resumed injection of boric acid.

Things are looking up, yes?

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110915/index.html JAEA will present an analysis of the accident progression of unit 2 at the Japan Atomic Energy Society meeting held in Kitakyushu from 19 September. According to their findings, unit 2's meltdown and explosion on 15 March could have been avoided if water injection had been started 4 hours earlier, at 4 PM on 14 March instead of 8 PM. Because of circumstances such as some fire trucks being broken by unit 3's explosion, the start of the preparation work for unit 2's water injection had been delayed. Tepco asserts that "As we worked with the maximum effort under extremely severe conditions such as high radiations, it is not thought that we have been late to perform the water injection work". The head of JAEA nuclear safety centre, Masashi Hirano says: "Since the cooling of unit 2 reactor has continued for 3 days, there is time margin and sufficient possibility to prevent fuel damage. The behaviour of the operators and the circumstances of the preparation of water injection are important points of the accident investigation."

 

[CaptD]

RE: Increase water flow rates:
I believe that the increased water is an attempt to try and cool the Corium(s) before they make (in at least one case) contact with the Earth below the reactor structure!

The concept of safe shut down is nothing more than more Nuclear Baloney (NB) SPIN because the three (3) reactor vessels have holes in them with their Corium(s) outside the containments with highly radioactive water leaking into either the ground water and or the Pacific Ocean!

Pretty hard to achieve SAFE shutdown when the Corium is outside the Reactor and continuing to fission on it own! This is nothing more than Radioactive SPIN, by TEPCO...

http://mdn.mainichi.jp/perspectives/news/20110909p2a00m0na016000c.html
snip
As a radiation metrology and nuclear safety expert at Kyoto University's Research Reactor Institute, Hiroaki Koide has been critical of how the government and Tokyo Electric Power Co. (TEPCO) have handled the nuclear disaster at the Fukushima No. 1 nuclear plant. Below, he shares what he thinks may happen in the coming weeks, months and years.

The nuclear disaster is ongoing. Immediately after the crisis first began to unfold, I thought that we'd see a definitive outcome within a week. However, with radioactive materials yet to be contained, we've remained in the unsettling state of not knowing how things are going to turn out.
...

Recovering the melted nuclear fuel is another huge challenge. I can't even imagine how that could be done. When the Three Mile Island accident took place in 1972, the melted nuclear fuel had stayed within the pressure vessel, making defueling possible. With Fukushima, however, there is a possibility that nuclear fuel has fallen into the ground, in which case it will take 10 or 20 years to recover it. We are now head to head with a situation that mankind has never faced before.

 

[Borek]

The concept of safe shut down is nothing more than more Nuclear Baloney (NB) SPIN because the three (3) reactor vessels have holes in them with their Corium(s) outside the containments

Any reliable sources to that claim?

 

[CaptD]

Here are some links that I can find right now, plus the Fairewind Assoc. Updates...:
 http://www.fairewinds.com/

 http://mdn.mainichi.jp/mdnnews/news/20110828p2a00m0na002000c.html


http://www.tokyotimes.jp/post/en/1665/Fukushima+cleanup+could+take+a+century+Nature.html

 http://fukushima-diary.com/

 http://www.guardian.co.uk/commentisfree/2009/may/28/who-nuclear-power-chernobyl

 

[Borek]

Here are some links that I can find right now

Regardless of whether these are reliable sources, none states anything about state and position of the corium.

 

[CaptD]

RE:Corium(s) Position
I was not saying that I have direct knowledge of the location of any of the three corium(s),
but rather I was giving my opinion based upon my understanding of the info I have read and my best guess.

I would be interested in what others have to say about the corium(s) and their proximity to the Earth and water table/ocean interface below the reactor complex...

Thanks

 

[Cire]

RE:Corium(s) Position
I was not saying that I have direct knowledge of the location of any of the three corium(s),
but rather I was giving my opinion based upon my understanding of the info I have read and my best guess.

I would be interested in what others have to say about the corium(s) and their proximity to the Earth and water table/ocean interface below the reactor complex...

Thanks

How about this opinion. The fuel pellets are scattered on the bottom of the RPV's. There is little to no corium produced. The RPV's are leaking at the various seals, flanges but not breached in any other way.

For those that want to argue corium melted through the bottom you need to answer this for me.

How do you get temperature readings from a sensor on the bottom of the RPV that would have melted off (wires) and destroyed the thermocouple before the RPV failed?

 

[CaptD]

Think penetration failures on yet another part of the reactor itself; one side may be intact while yet another is "gone"... and this may be responsible for "The Fuky Effect", where the temperature graph zooms up then down!
http://atmc.jp/plant/rad/?n=1
Thanks for asking!

+
This from April 20th Japan nuclear agency finally admits fuel has melted in reactors 1, 2 & 3 http://enenews.com/japan-nuclear-agency-finally-admits-fuel-melted-reactors-1-2-3
+
Reactor Rod images:
http://www.houseoffoust.com/fukushima/rods.html

 

[Astronuc]

Reactor Rod images:
http://www.houseoffoust.com/fukushima/rods.html

Those are not images of fuel rods. Fuel rods are not that large. What they show is someone's uninformed opinion.

 

[Cire]

Think penetration failures on yet another part of the reactor itself; one side may be intact while yet another is "gone"... and this may be responsible for "The Fuky Effect", where the temperature graph zooms up then down!

How does molten corium move laterally out of the side of the RPV, melting through several inches thick steel wall but not fall through the thin perforated core plate?

There are plenty of papers modeling corium migration to the RPV bottom. Can you point to one where corium exits from the side?

Be careful reading into news reports when the term "melted" is used or "meltdown". Having fuel pellets melt through their cladding and fall down into the RPV is considered a meltdown. It's also something very different then the elephants foot from Chernobyl.

 

[MiceAndMen]

Anybody seen this site before, seems to have "new" info:
http://www.houseoffoust.com/fukushima/fukushima.html

Discredited. Fantastical rumor mongering and unsubstantiated speculation. If the site had paid advertisemets it would be the Fox News of Fukushima. But there are no ads there so it's more like Tinfoil Central.

Hey, Nancy, is building 4 still leaning? What do your inside on-site sources say?

 

[CaptD]

Melted Fuel at Fukushima May Have Leaked Through, Yomiuri Says
By Go Onomitsu - Jun 6, 2011 11:02 PM PT
http://www.bloomberg.com/news/2011-06-07/melted-fuel-at-fukushima-may-have-leaked-through-yomiuri-says.html
snip
The melted fuel at Tokyo Electric Power Co.’s Fukushima Dai-Ichi nuclear power station may have leaked through the pressure vessels of the Nos. 1 to 3 reactors, the Yomiuri newspaper reported.
The Japanese government will submit a report to the International Atomic Energy Agency that raises the possibility the fuel dropped through the bottom of the pressure vessels, a situation described as a “melt through” and considered more serious than a “meltdown,” according to the report, which cited the document.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110917/1330_kaisui.html An internal document reveals that on 16 March, the NISA had given Tepco a calculation estimating that the reactors would be filled with salt up to 5 metres above reactor bottom, preventing any further cooling, between 2 April early in the morning and 3 April in the morning. Tepco actually stopped using seawater and started using freshwater between 25 March and 26 March.

 

[rmattila]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110917/1330_kaisui.html An internal document reveals that on 16 March, the NISA had given Tepco a calculation estimating that the reactors would be filled with salt up to 5 metres above reactor bottom, preventing any further cooling, between 2 April early in the morning and 3 April in the morning. Tepco actually stopped using seawater and started using freshwater between 25 March and 26 March.

That is a relatively straightforward calculation to make, and I suppose it was done by many people following the event at that time: estimate the decay heat, assume that the coolant reaches the core in such a way that the decay heat will be transmitted by evaporation, and you get the evaporation rate of the order of about 100-200 tons per day. This translates into 3 - 7 tons of salt per day.

The only problem is that nobody knew then (and does still not know) how much of the cooling water will actually reach the core and how much will leak past it e.g. through the recirculation pump seals, and how intact the pressure vessel bottom is. That estimate given by NISA seems to be the conservative maximum estimate obtained by assuming no leaks at the RPV. (Conservative in the sense of estimating the amount of accumulated salt - hopeful in the sense of estimating the core damages.)

A similar calculation could also be made concerning the amount of oxygen brought into the containment in the cooling water and released into the containment when the water was being heated. IIRC, the number was several kilograms per day (don't have the relevant papers at hand now to double-check).

 

[dezzert]

First post after lurking since March. A quick question.

They estimated at the time that after 20 days of seawater injection there would be 15+ feet of salt in the bottom of the reactor. They used seawater for 14 days, so the estimate of salt levels inside the reactors would be approximately 10+ feet of salt on March 26. I know that this is purely hypothetical, and the true amount unknown, but the alternatives if I read this right are a) salt accumulation of that amount or b) a less amount if the bottom has been breached. Assuming no large breach in the RPV, and assuming that a fair amount of salt did make it into the reactor where it still resides, how can there be accurate measurements of temp at the bottom of the reactors if they are buried in salt.

 

[rmattila]

First post after lurking since March. A quick question.

They estimated at the time that after 20 days of seawater injection there would be 15+ feet of salt in the bottom of the reactor. They used seawater for 14 days, so the estimate of salt levels inside the reactors would be approximately 10+ feet of salt on March 26. I know that this is purely hypothetical, and the true amount unknown, but the alternatives if I read this right are a) salt accumulation of that amount or b) a less amount if the bottom has been breached. Assuming no large breach in the RPV, and assuming that a fair amount of salt did make it into the reactor where it still resides, how can there be accurate measurements of temp at the bottom of the reactors if they are buried in salt.

The RPV temperature measurements usually measure the temperature from the outside surface of the pressure vessel metal, so if the RPV is intact, its contents should have no effect on the measurement thermocouples. However, based on the current data it's very difficult to say anything about the contents of the RPV, as all depends on the condition of the RPV and the route the coolant water has been flowing during the past several months. In any case, there seems to be quite a lot of salt in the water they pump from the basements, and at least this salt has not accumulated in the RPV. It doesn't take a big leak to wash away the stuff, if there is a constant flow of water during several months.

 

[dezzert]

Thanks rmattila. Another question. Salt being a crystal, could it be storing energy via the Wigner effect (which I don't really understand other than atoms are pushed out of place and store energy in the process, yes?).

 

[Rive]

Tsk-tsk-tsk. Salt.

Could the molten core debris be cooled by the molten salt? Preventing it from breaking the RPV?

 

[swl]

For those that want to argue corium melted through the bottom you need to answer this for me.

How do you get temperature readings from a sensor on the bottom of the RPV that would have melted off (wires) and destroyed the thermocouple before the RPV failed?

If the thermocouples were held in place by magnetic recepticles, the steel of the RPV would have lost it's magnetic properties at about 770C, and the thermocouple(s) would have fallen to some position either hanging by their leads or at the bottom of the dry well.

With the information released by TEPCO, I am only certain that I don't know where the fuel is.

BTW, if the fuel is in a configuration of unmelted pellets, is recriticality possible, or is it impossible in such a configuration. If it did occur, it seems as though it would stop quickly as the water boiled away, but such a condition could make cooling difficult. As all 3 reactors are near or below 100C it's probably not an issue.

 

[dezzert]

Tsk-tsk-tsk. Salt.

Could the molten core debris be cooled by the molten salt? Preventing it from breaking the RPV?

Since they started seawater on the 12th, and supposing the contents of the RPV have melted into a corium mass, wherever it might be, wouldn't the salt just be a part of that mass. And a fairly big part. At least in R2 and R3.

And supposing if this is the case, would that hinder or help re-criticality.

 

[LabratSR]

Discredited. Fantastical rumor mongering and unsubstantiated speculation. If the site had paid advertisemets it would be the Fox News of Fukushima. But there are no ads there so it's more like Tinfoil Central.

Hey, Nancy, is building 4 still leaning? What do your inside on-site sources say?

100 percent, Spot on.

 

[Cire]

If the thermocouples were held in place by magnetic recepticles, the steel of the RPV would have lost it's magnetic properties at about 770C, and the thermocouple(s) would have fallen to some position either hanging by their leads or at the bottom of the dry well.

The type of thermocouple used on the RPV would have been completely damaged before reaching 770C. The wiring, cold junction connections, would also be damaged. They would be reading open or shorts on those sensors. Instead we see something that looks like a valid temperature. A reading that changes appropriately with water injection rates.

I don't see how that's possible with a dry well full of slag and corium glowing at >> 2700F. The radiant heat alone would have melted all the cables and wiring leading into and out of the RPV near the bottom.

I don't see how you get corium under the reactor and a few feet away a functioning temperature sensor. Think of what a steel induction furnace looks like.. That the environment people are suggesting these low temperature sensors are operating correctly in.

 

[tsutsuji]

A similar calculation could also be made concerning the amount of oxygen brought into the containment in the cooling water and released into the containment when the water was being heated. IIRC, the number was several kilograms per day (don't have the relevant papers at hand now to double-check).

Is there more oxygen in seawater than in freshwater ?
Is oxygen a cause for other troubles apart from hydrogen explosions ?
How is oxygen controlled during normal operation of a nuclear power plant ? You say "when the water was being heated". Does it mean that as long as water is not heated beyond the temperatures allowed in normal operation, there is no need for other control tools apart from controlling the temperature ?

The other day I read the following (a 2005 JNES course on nuclear safety)

Flammable gas control system:
The system is designed to prevent combustion of hydrogen and oxygen being generated in the containment vessel at the time of loss of coolant accident. After recombination of hydrogen and oxygen, remaining air goes back to the dry well through the vacuum breaker, so that gas concentration can be controlled in this manner throughout the containment vessel. In many cases, this system is composed of the portable recombiners of full 100 percent capacity and some others. At Unit No.6 and No.7 respectively of Kashiwazaki Kariwa Power Station, the system is arranged for common use at each reactor building.

Summary of Safety Design of Nuclear Power Station (Case of BWR) http://www.ansn-jp.org/item_file/2005-09.pdf

They didn't have those at Fukushima, did they?

 

[rmattila]

Is there more oxygen in seawater than in freshwater ?
Is oxygen a cause for other troubles apart from hydrogen explosions ?
How is oxygen controlled during normal operation of a nuclear power plant ? You say "when the water was being heated". Does it mean that as long as water is not heated beyond the temperatures allowed in normal operation, there is no need for other control tools apart from controlling the temperature ?

By "fresh" I meant pumping "new", cold, possibly oxygen-rich water (whether it is seawater or freshwater has no significant effect on the solubility) into the containment as opposed to circulating the same water, as is done during normal reactor operation. Solubility of oxygen is larger at lower temperatures, and when the water is heated, excess oxygen is released as gas. After reaching boiling point, all dissolved oxygen has been released from the water.

During outages, oxygen (as well as nitrogen) from the air is dissolved in the primary water, and removal of oxygen is one stage during the heating of the reactor when starting it up after a cold shutdown. During operation, oxygen enters the primary circuit both by radiolysis of the cooling water and by leaking into the condenser vacuum, and the vacuum must by continuously maintained with ejectors or vacuum pumps, which suck the non-condensible gases from the condenser through recombiners to the exhaust stack.

In addition to being released from the water used to cool the (damaged) fuel, oxygen may also enter the containment if the cooling rate is not constant, and at some points of time the condensing rate of the steam within the containment is larger than the rate of evaporation, and the contaiment consequently falls below the ambient pressure. The possibility of oxygen entering the containment is the reason they've continued the injection of nitrogen in order to keep the gases from accumulating to such concentrations that the hydrogen (possibly still present as a lighter gas within the containment dome) might ignite.

 

[Rive]

Since they started seawater on the 12th, and supposing the contents of the RPV have melted into a corium mass, wherever it might be, wouldn't the salt just be a part of that mass. And a fairly big part. At least in R2 and R3.

IMHO NaCl cannot be part of the corium. The melting point of salt is 801 Celsius, what means that the core debris had a kind of liquid coolant before it could melt: and NaCl has 1465 Celsius boiling point, what means salt must boil away before core debris could melt to corium. What also means some phase-changing cooling.

Am I right?

 

[mscharisma]

I have begun to read the big Fukushima Daini report that was published on 12 August : http://www.tepco.co.jp/cc/press/betu11_j/images/110812b.pdf ...

Forgive me if I simply missed it in the news, etc., but have they meanwhile come up with a plausible explanation and solution for the contaminated water found in the building basement(s) of the Daini site (the "from airborne emissions from Daiichi" not being plausible imho)?

Thanks.

 

[etudiant]

Has there been anything published on the effects of salt water cooling for a disintegrating core?
Specifically, it would be useful to have some idea of the likely reactions between the fuel oxides and the nuclear reaction products with the chlorine ions in the salt, both dissolved as well as molten.
As I remember my chemistry, the chlorine should have no trouble displacing the oxygen under high temperature conditions.
Would the resultant chlorides be materially more soluble than the fairly inert oxides?
What are the implications for the nature of the airborne emissions from the site and could that help explain the finding of plutonium and neptunium depositions quite a distance from the plant?