Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[elektrownik]

I found some document from tepco in english, I can't find orginal version, maybe there is translation error: http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e12.pdf
There is: "status of the plant at the time of earthquake" and for unit 4: "maintenance (removing fuel)" So this is translation error ?
Also for unit 6: "rpv closed" if it is closed should it be at atmospheric pressure like now ?

 

[joewein]

I found some document from tepco in english, I can't find orginal version, maybe there is translation error: http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110516e12.pdf
There is: "status of the plant at the time of earthquake" and for unit 4: "maintenance (removing fuel)" So this is translation error ?
Also for unit 6: "rpv closed" if it is closed should it be at atmospheric pressure like now ?

They must have meant "fuel removed".

The definition of cold shutdown is below 100 deg C and at atmospheric pressure (because there's no steam at that temperature).

 

[joewein]

I suppose that the contamination of water in the basements and SFPs is being measured near the surface, is this correct?

But then the measurements will be meaningful only for metals whose salts are generally soluble, like cesium;as well as forr elements with very soluble anions, like the halogens. Most other elements should tend to precipitate out. Since there is little circulation in those spaces, they should accumulate as a layer of sludge (or dirtier water) at the bottom of the liquid.

Is this likely to be happening? Could it become a problem for the decontamination efforts?

I think your assumptions are correct, Jorge. They can only take a sample in an accessible spot, probably near one of the stairwells.

The less soluble salts will be more concentrated in sludge at the bottom, but overall there should be less of them in the basement because they would have been more likely to stay inside the containment to start with, simply because they were less soluble.

Most likely hot water, especially pressurized hot water (> 100 deg C) will leach out some less soluble salts from the fuel or from condensate on the containment walls, like water in a coffee maker or espresso machine. The water leaks outside via damaged seals and as it cools off in the basement some of the salts precipitate out as solubility drops with temperature.

For the water decontamination efforts that sludge is not an immediate problem, since the primary objective is to prevent contaminated water from overflowing, which can be achieved if the overall quantity is reduced. Once solubles are separated out, the cleaned water can be reused or evaporated.

In the more long term, once the goal becomes to decontaminate the buildings and pack up their radioactive inventory into containers for transport to a permanent storage site, then any sludge would have to be removed too. At that stage there might be demand for a good steam cleaning robot for the Fukushima basements.

In the near term I see little need for any human to venture into those basements.

 

[ceebs]

Aha, I see that article also describes how the Japanese robot has failed on its first mission.

To be honest I am not too shocked at this news, because that robot looks rather fragile to me, like a prototype that is not ready, especially in the video they posted of it which shows it doing the things it has apparently failed to do properly today.

So is this crash down to equipment failure? or radiation effected electronics?

 

[elektrownik]

And here: http://www3.nhk.or.jp/daily/english/26_11.html I think that they could find something not so expensive like boric acid to prevent corrosion

 

[zapperzero]

They could add any acid, but they need the boron to prevent criticality, should their worst-case scenario described in the article (racks failing due to corrosion) come true.

 

[elektrownik]

They could add any acid, but they need the boron to prevent criticality, should their worst-case scenario described in the article (racks failing due to corrosion) come true.

But why they weren't doing this until today ?

 

[Atomfritz]

But why they weren't doing this until today ?

They took water samples in May.
Then they started to add hydrazine to the water to avoid corrosion.
Now they are adding boric acid again.
I am no chemist and cannot say anything about the behavior of the neutron absorbers in the SFP.

Could it be possible that they found out that there could be potential danger of the neutron absorbers dissolving in the basic water?

If this is the case then the boron acid added again could be not only for the (official) reason to avoid fuel leaks.
It could be also to avoid criticalities when the thinning of the neutron absorbers reaches a critical threshold.

And here: http://www3.nhk.or.jp/daily/english/26_11.html I think that they could find something not so expensive like boric acid to prevent corrosion

Just assuming that other acids would be used to neutralize the water to around pH 7.
Couldn't then be a risk that if boric acid is added a later time when a criticality should happen, that it would be less efficient? Maybe due to boron precipitating out instead of staying in solution?

And, consider debris sludge and pockets also which can hamper water circulation. In case of a sudden criticality there could be a problem to get boron to critical places quickly enough. So it might be better to have it already there prophylactically.

And, then the compatibility question in regard to water decontamination.
I suppose this would be somewhat more difficult if you have not only boric acid in the water but a full cocktail of acids.

Just my unqualified thoughts.

 

[elektrownik]

@up I think so also, maybe they know more, maybe they detected some proofs of recriticality in unit 3 sfp... who know

 

[Borek]

My first thought is that it is just a KISS principle. Water is highly alkaline - that's bad, so they have to neutralize it. Boric acid is probably a thing they already have at place, it will serve multiple purposes, it is already everywhere, so they will have to deal it anyway - does it make sense to use something else and add another unknown into the equation?

 

[Jorge Stolfi]

They took water samples in May. Then they started to add hydrazine to the water to avoid corrosion. Now they are adding boric acid again.

Somewhere earlier in this thread it was said that hydrazine (which is quite toxic) is added to purified water in working reactors to fight corrosion, but in very small amounts --- parts per million or so. If that is correct, it would not make much difference to the pH.

Boric acid was initially used as a source of neutron-absorbing boron to prevent criticality. Whether it is now being added for that reason, or to adjust the water's pH, the amounts needed must be much larger. I recall that early on Areva shipped to Fukushima several tons of the stuff, enriched for boron-10. (Presumably they used boric acid at the beginning, rather than some other boron compound, because it is soluble, fairly non-toxic, and contains no extra elements -- only H and O. Now they may be using it simply because it is a mild harmless acid already at hand).

However, I cannot imagine what could have made the saltwater in the basement alkaline. Perhaps reaction between the salt and reactor metals, like steel and zirconium?

 

[Calvadosser]

(snip)

However, I cannot imagine what could have made the saltwater in the basement alkaline.

(snip)

All that radioactive cesium?

 

[joewein]

TEPCO found that the water in the pool had turned strongly alkaline, with its PH level reaching 11.2. The leaching of calcium hydrate from the debris is believed to be the cause.

I guess this is because while the concrete of the pool is protected by a steel liner and hence should not come into contact with the hot pool water, any bits of concrete knocked into the pool by the explosion will gradually dissolve.

I wonder when they first tested the pH of the pool water.

Aluminium certainly doesn't take very well to being immersed in strongly alkaline liquids. Not only does it quickly corrode the aluminium, it can also produce large amounts of hydrogen (as a teenager I used to fill balloons with hydrogen made from aluminium foil dropped into bottles filled with sodium hydroxide solution).

 

[joewein]

However, I cannot imagine what could have made the saltwater in the basement alkaline. Perhaps reaction between the salt and reactor metals, like steel and zirconium?

Unless I missed something, weren't they only talking about the spent fuel pool?

However, if it happens with calcium from concrete bits in the SFP, one should it expect it to happen in the basement too. In fact, there should be a lot more concrete in permanent contact with water in the basements than in the fuel pools. Hopefully they'll test the pH in the basements too.

 

[MadderDoc]

And here: http://www3.nhk.or.jp/daily/english/26_11.html I think that they could find something not so expensive like boric acid to prevent corrosion

Certainly any acid could be used to neutralize an alkaline solution, but using boric acid has the added benefit of tending to produce a buffered solution at about pH 7-9, right where you'd want a solution containing aluminium to be in order to avoid corrosion.

 

[Borek]

However, I cannot imagine what could have made the saltwater in the basement alkaline.

All that radioactive cesium?

Radioactivity doesn't matter. Cesium per se is not alkaline, and it doesn't react with water as it was never metallic in the first place. Could be it was present as oxide in the uranium dioxide pellets, that could produce hydroxides when reacting with water, but it also requires broken fuel rods - my understanding is that so far we have no idea if they were broken or not.

No idea what they mean by "calcium hydrate", as far as I can tell there is no such compound.

 

[joewein]

No idea what they mean by "calcium hydrate", as far as I can tell there is no such compound.

Presumably calcium hydroxide.

 

[Fine]

However the following document does contain some pictures that I don't think I've seen before, outside reactor 3 building (demolished the damaged vehicle entrance tunnel by the looks of it). And also, joy of joys, a view of the site looking down from the top of the slope where the webcam is, so that we can actually see the ground around the reactors and further to the left of reactor 1 than normal. Its not very high res within this pdf, but it still gives me a much improved sense of the state of a good chunk of the site these days. (that photo, or rather 3 photos stitched together, is on page 13)

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110617e4.pdf

There is a very interesting intesting picture of reactor 3 on Pg 7. what is the semi-circular structure/debris toward the upper left of the photo ? A reactor pit plug ? Sorry for the speculation but I sure would like to have some expert eyeballs and opinions on this.

 

[SteveElbows]

There is a very interesting intesting picture of reactor 3 on Pg 7. what is the semi-circular structure/debris toward the upper left of the photo ? A reactor pit plug ? Sorry for the speculation but I sure would like to have some expert eyeballs and opinions on this.

Well that photo is fairly old now, and so this question has come up before. Although it is hard to make out too much in that photo with certainty, it seems pretty likely that the concrete you see is simply far too small to be a reactor plug.

 

[Fine]

I know it is old but I have been carefully following the threads and have not seen any discussion at all about it. If it isn't a plug what is it ? I still think this the best view of reactor 3 that I have seen.

 

[Orcas George]

I would guess that it has something to do with the seawater that they were pumping (did they pump seawater into SFP #3?) Not the seawater itself although it is more alkaline than pure water, but all of the sea creatures that they sucked up at the same time. Crabs excrete ammonia, for example.

The plankton filter in front of an RO system gets really nasty (and puts a foul taste in the water) if you don't change it often. If they have tons of plankton, seaweed, brine shrimp, etc. in the bottom of the pool then chemistry changes are not surprising.

I feel like they are a juggler trying to hold up a bunch of spinning plates into the air.

By the way, have they started treating the water yet? I thought it was urgent...

 

[ManuBZH]

By the way, have they started treating the water yet? I thought it was urgent...

According to this news report: http://www3.nhk.or.jp/daily/english/26_16.html , they have processed 5400t of water already and aim to start their "full-scale operation" tomorrow. Then, we'll see if the system is stable on the long-run...

 

[tsutsuji]

According to this news report: http://www3.nhk.or.jp/daily/english/26_16.html , they have processed 5400t of water already and aim to start their "full-scale operation" tomorrow. Then, we'll see if the system is stable on the long-run...

The 5400 tons are decontaminated, but not all of it is desalinated. http://www3.nhk.or.jp/news/html/20110627/t10013780371000.html says 600 tons have been desalinated.

http://www.chunichi.co.jp/s/article/2011062690220051.html : Between June 20th and June 26th, 5178 tons were decontaminated at a 49.7 ton/hour flow. But the system was kept idle during a total of 38 hours of flushing. As a result, the average flow was 863 tons per day, falling short of the originally planned 1200 tons per day.

 

[elektrownik]

Can anyone explain me why unit 5 plots are so strange ? It was normal, but something changed between 6/24 and 6/25: http://www.tepco.co.jp/nu/fukushima-np/f1/images/11062612_temp_data_56u-j.pdf

 

[MadderDoc]

Can anyone explain me why unit 5 plots are so strange ? It was normal, but something changed between 6/24 and 6/25: http://www.tepco.co.jp/nu/fukushima-np/f1/images/11062612_temp_data_56u-j.pdf

It looks to me like the sfp previously was cooled by a system shared with the RPV, and has now been switched to use its own cooling system.

 

[MadderDoc]

There is a very interesting intesting picture of reactor 3 on Pg 7. what is the semi-circular structure/debris toward the upper left of the photo ? A reactor pit plug ? Sorry for the speculation but I sure would like to have some expert eyeballs and opinions on this.

Many unit 3 photos from many angles have been scrutinized by many people. The chance of a reactor pit plug sized and shaped object lying about somewhere in unit 3, with relatively free view to it as suggested by the photo your are referring to seems very small.

 

[tsutsuji]

Can anyone explain me why unit 5 plots are so strange ? It was normal, but something changed between 6/24 and 6/25: http://www.tepco.co.jp/nu/fukushima-np/f1/images/11062612_temp_data_56u-j.pdf

I don't remember if he was talking about unit 5 or unit 6, but the other day, if my understanding is correct, Mr Nishiyama of the NISA said that there was no need any longer to share the same cooling system between the spent fuel pool and the reactor. So from now on, the spent fuel pool and the reactor will be cooled simultaneously instead of flip-flopping.

For unit 5 http://www.nisa.meti.go.jp/english/press/2011/06/en20110626-1-2.pdf page 12 says "June 24 16:35 Cooling of the Spent Fuel Pool was started using the Fuel Pool Cooling and Clean-up System."

 

[elektrownik]

It looks to me like the sfp previously was cooled by a system shared with the RPV, and has now been switched to use its own cooling system.

[STRIKE]But there is change in rpv plot for unit 5 also ?[/STRIKE]
@up I see now, thanks !
I found some new contamination data (english): http://www.acro.eu.org/RAP110620-OCJ%2801%29-v1.pdf

 

[MadderDoc]

Unless I missed something, weren't they only talking about the spent fuel pool?

However, if it happens with calcium from concrete bits in the SFP, one should it expect it to happen in the basement too. In fact, there should be a lot more concrete in permanent contact with water in the basements than in the fuel pools. Hopefully they'll test the pH in the basements too.

The surface-near layer of concrete structures weathers and becomes less alkaline as it reacts with the carbondioxide of the atmosphere, while concrete bits produced by the explosion would feature fresh concrete surfaces which are considerably more alkaline.

 

[joewein]

I don't remember if he was talking about unit 5 or unit 6, but the other day, if my understanding is correct, Mr Nishiyama of the NISA said that there was no need any longer to share the same cooling system between the spent fuel pool and the reactor. So from now on, the spent fuel pool and the reactor will be cooled simultaneously instead of flip-flopping.

The diagram indicates that in unit 6, the same cooling system is still being shared between the RPV and the fuel pool, as you can see the temperature of one going up whenever the other is going down.

 

[robinson]

Has this already been discussed to death?

http://www.technologyreview.com/blog/arxiv/26738/

 

[jim hardy]

@ robinson
well that one gets curiouser and curiouser...
From the article ...
"Matsui points out that there are some potential question marks about the data. One possibility is that the chemical properties of cesium and iodine might mean they are flushed away from the reactors at different rates, changing their ratios.""

Strictly speaking a fellow ought to compare Cs to Cs or I to I so the dilutions via chemistry are similar.

i was trying in early days using Cs137 to Cs136 ratio, never found a sample reported that looked newer than day of earthquake.

A friend was tracking Iodines and thinks to this day something went on around 21 March.
I131 to I 134 would have been nice but they quit reporting most nuclides after DR Veress's article about CL38:
http://lewis.armscontrolwonk.com/files/2011/03/Cause_of_the_high_Cl38_Radioactivity.pdf

Tepco retracted the Cl38 reading as being a mistake.
Which it could very well be, that was discussed with a radiochemist over on the market-ticker forum. He said Cl38 has a pattern similar to some other longer lived stuff and it's a natural mistake to make.

so only TPTB know.

Btw thanks for that link - it is an interesting paper over there at Arxiv, with handy references to old readings.

old jim

 

[benzyme]

Just a thought:

I have been reading this forum for several months - thanks to those that make an effort to keep conversations grounded, developing, and on point. It seems things have leveled off somewhat and many conversations have reached their end. I suggest that this might be a great opportunity for those with a "seasoned" perspective to take an inventory.

I bet many readers would be thankful for some kind of a recap. I could see a reactor by reactor list of 1) what has transpired, 2) the current status, and 3) what lies ahead (building-specific). For some events/sub-events there might be a couple valid positions, etc.

I know this would entail some work, but I also thought some posters might enjoy the project. Maybe it could spark some new discussion. I am not sure what format would work best. If someone has already created this document maybe they could link it for me? While informative, the Wikipedia article isn't really what I'm talking about.

 

[elektrownik]

Why unit 4 sfp is only 2300mm ?

 

[zapperzero]

I bet many readers would be thankful for some kind of a recap. I could see a reactor by reactor list of 1) what has transpired, 2) the current status, and 3) what lies ahead (building-specific). For some events/sub-events there might be a couple valid positions, etc.

I'm sure they would, so get writing.

A detailed timeline would be helpful, to be sure, but the reports we have are so confused and there is so much more data we lack, that it may be way too early.

The Japanese gov't did a huge data dump a couple days ago - all the reports it got from TEPCO in the first month or so, thousands of documents. Maybe something will come out of it, but it's all Japanese, so... it will take a long long while before they become accessible to most of us here, assuming they ever get translated in the first place. Were it not for ex-skf, I wouldn't even know about its existence.

http://www.nisa.meti.go.jp/oshirase/2011/06/230624-2.html