Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[jlduh]

nothing outstanding or surprising. the clueless are promptly learning that a: the radioactivity is distributed in spots, and VERY much in spots (several orders of magnitude difference between hotspot and area around it) and b: the poorly done monitoring misses those spots. Then they will learn that c: even good monitoring will miss many of those spots.
On to food testing when they will 'discover' that a good chunk of radioactivity is in samples hundreds times above limit, which are rare, and aren't stopped effectively by traditional random sampling.

Well, again what you describe has a name and has been proved by experience at Tchernobyl: contamination in leopards spots.

I repost this map of Tchernobyl contaminated zones (Cs-137) because it is very informative about real life contamination transportation and redeposition:

http://www.netimago.com/image_200655.html I would like to know what could be the reasons why this phenomenon wouldn't apply for the Fukushima plant, looking at how things evolve at the reactors?

My feeling is that we start to see appearing, through the various infos and measurements released in the press, that kind of hot spots (first towards North west axis, then recently towards south west axis, maybe including Tokyo), even at high distances from the plant (and much further than the 30 kms zone), and that's why some governors get angry because of lack of fine "tuning data" to identify these spots and decide what to do (see my post here:

https://www.physicsforums.com/showpost.php?p=3304552&postcount=141 )

Then how do deal with that kind of hot spots, that's all the question. 1) Expanding the evacuation zone in a circular manner with increased radius around most of the hotspots is a solution... more easily done in Ukraine than in Japan due to population density, i admit! 2) Do a real fine tuning based on reliable and updated data. But even this could lead in the future to much more evacuations if hotspots multiply...

The other question is, can this second fine tuning be done in a timely and reliable manner?

And as you said, can statistical sampling on food detect properly the consequences of these hotspots, which are probably like fractals shapes: from macro hotspots to very local hotspots because of local redeposition conditions and concentrations? Japan has lots of mountains which also create a much more complex redeposition pattern scenario than on flat lands i think, because of local geography/meteorology which are characteristics of mountains areas.

 

[tsutsuji]

Yes, the article is real. I obtained a copy of yesterday's Asahi Shimbum from a neighbor.

The article is on page 5 from the 15th May. I've scanned the full article for those who are interested.

Thanks. At the end of the article, it is mentioned that these results will be communicated at http://www.icas2011.com/ on May 24th (1). I guess the press will be more talkative about them from that date on.

(1) The program for "S22) Urgent Symposium Analytical Sciences Facing Radioactive Pollutions" is available at http://www.icas2011.com/program/program_list.html#24PS22 ; See also http://www.icas2011.com/program/program_list.html#23pB2 for May 23rd

 

[rowmag]

Radiolysis applies only on molecules with covalent bonds. NaCl has ionic bonds - as it solved it becomes a mix of separated Na+ and Cl- ions immediately.

Thank you. So mostly a mess to clean up, then, from getting seawater in a reactor, and not necessarily a corrosion concern?

 

[biffvernon]

Mudstone is a second class bedrock. If exposed, it would erode rather rapidly compared to say, granite.

The word 'mudstone' by itself doesn't tell us much. It just means that once upon a time it was a muddy, i.e. fine-grained, sediment. Without further qualification it doesn't say anything about hardness, strength or resistance to weathering and erosion. Mudstones with a silica-rich matrix, subjected to relatively high pressures and temperatures millions of years ago, can be almost as strong as granite and certainly good enough for building power stations upon. Others might not be. Any sort of mudstone is likely to be pretty impermeable to water, at least before being fractured by earthquakes.

 

[jlduh]

Thank you. So mostly a mess to clean up, then, from getting seawater in a reactor, and not necessarily a corrosion concern?

Well again, even if this a slightly different subject from the Daichi plant, I have a hard time understanding how seawater can enter so easily (i say "easily" just because it just happened...) into a BWR reactor. But I understand that unlike a PWR, in a BWR there is no real secondary circuit (i mean closed loop), so the steam is condensed into water in the condenser (which is cooled by seawater if my understanding is ok) and goes back into the reactor right?

So any leak between the two (the sea water/the steam or condensed water) can theoretically (and practially in this case) lead to either seawater entering the reactor or contaminated water going back to the sea?

I would be surprised if this Hamaoka event was the first in BWR history with that kind of problem. Any knowledge on that?

If i rely on what has been said for Daichi reactors, it seems that the experts have very few data on the effects of seawater inside BWR reactors. And by a very surprising collision of events, we just learn that 500 tons of seawater has probably enter one of the reactors of Hamaoka plant during cold shutdown procedure!

Can someone confirm if this seawater actually entered the reactor (I mean the pressure vessel)? Or is it somewhere else?

If it's the case, and as i said yesterday, it seems god is recently playing dices in the nuclear game and wins much more than calculated by experts, don't you think?

 

[Borek]

Thank you. So mostly a mess to clean up, then, from getting seawater in a reactor, and not necessarily a corrosion concern?

Corrosion in salty water is in general much faster than in fresh water, so it can be a problem - but not because of the radiolysis.

 

[Rive]

Thank you. So mostly a mess to clean up, then, from getting seawater in a reactor, and not necessarily a corrosion concern?

Cl- ions are always a primary corrosion concern, but radiolysis is not relevant in this case: Cl- ions are present in saltwater by default.

 

[TCups]

No, certainly not. I am just saying that the simplest explanation that is consistent with the evidence is not consistent with the claim of anyones seeing the ignition. You can uphold the claim only by adding more assumptions to the explanation, however these assumptions would seem to be added, not to make the explanation consistent with the evidence, but to make it consistent with this extraneous claim.

The observations I make are these: the southeast corner of Building 3 three (roof and south wall) visibly expands, blows out, and ejects a relatively small white puff of gas laterally, which almost immediately turns to a somewhat larger, self-consuming orange fireball.

This is followed temporally by the more generalized explosion of the entire upper portion of the building and a rising column of dense gas, apparently steam and smoke, directly over the spent fuel pool (as in pool of hot water) -- a column of smoke with a large amount of "lift", and an appearance consistent with a littoral explosion.

The post-mortem images of Building 3 seem to confirm both localized thermal and mechanical damages at the southeast corner, over the SFP as well as more generalized lateral and vertical blast damages, consistent with those observations.

A large increase in measured radiation accompanied the explosion(s), perhaps consistent with explosive venting of the primary containment, or some portion of the contents of the spent fuel pool, or some combination of both.

Time does not permit me to again append the supporting visual images as I must be off to work just now. Perhaps I can do so in an "edit" at a pater time, or perhaps the content of several thousand preceding posts will suffice.

Therefor, please, I ask, do excuse any extraneous or inaccurate claims I have made or implied in my perhaps deeply flawed and sometimes incoherent attempts to arrive at a "simple" explanation to a complex set of events. If "ignition" is the incorrect term for a white puff of gas turning fiery orange, then I stand humbly corrected. Thank you for your patience and thoughtful critique in any case.

 

[zapperzero]

The other question is, can this second fine tuning be done in a timely and reliable manner?

Even if it could, you're much better off drawing a line around areas with hotspots, because the hotspots move all the time. Bio-accumulation sucks. The water cycle blows.

Yes, even radioactive badgers.
http://chornobyl.in.ua/en/badger-meles-meles.html

 

[NUCENG]

There are only a few images from the period after 3 blew but before 4 went up.

I don't think the resolution is high enough to be 100% sure, but it looks to me like there was already debris fallen onto the pipe in the place where it is later shown to be broken. And I think its always been a pretty likely bet that it was falling walls of reactor 3 that caused the damage.

Thanks for finding those. They don't look conclusive to me whether the pipe was damaged or not. I'll keep looking.

 

[tsutsuji]

Corrosion in salty water is in general much faster than in fresh water, so it can be a problem - but not because of the radiolysis.

In an article dated March 25th dealing with Fukushima Daiichi seawater corrosion issues, Euan Mearns made the following quote :

In this earlier post I quoted TOD commenter donshan who spoke authoritatively on corrosion issues:

" I do question the use of seawater cooling. I hope the Japanese have considered the danger they have created by introducing oxygenated seawater into this stainless steel piping and pressure vessel at boiling temperatures. These stainless steels are extremely susceptible to chloride stress corrosion cracking:

Since residual weld stresses and tensile stress in piping, valves, control tubing, etc. are always present, Standard Operating Reactor water quality standards require keeping chlorides at parts per billion levels. Seawater has about 3.5% or 35 grams per liter of salinity! (i.e. 35,000,000 parts per billion)

I have no way of knowing how many days they have before a stainless steel component suddenly cracks, but if it were me, I would be advocating an emergency program to get pure deionzied cooling water back into this stainless steel system ASAP. In laboratory tests in boiling chlorides, cracking of stainless in tensile stress can occur within days- they have at most a few months if they keep boiling sea water in this system and yet another disaster occurs."
http://www.energybulletin.net/stories/2011-03-25/fukushima-dai-ichi-status-and-slow-burning-issues

 

[jlduh]

For those interested, i just posted here:

https://www.physicsforums.com/showpost.php?p=3304672&postcount=142

this link to a documentary made by Adam Curtis (many film for the BBC) on the intesresting history of BWR reactors...

Direct link to the page here: http://www.bbc.co.uk/blogs/adamcurtis/2011/03/a_is_for_atom.html

 

[Rive]

Then how do deal with that kind of hot spots, that's all the question. 1) Expanding the evacuation zone in a circular manner with increased radius around most of the hotspots is a solution... more easily done in Ukraine than in Japan due to population density, i admit! 2) Do a real fine tuning based on reliable and updated data. But even this could lead in the future to much more evacuations if hotspots multiply...

The other question is, can this second fine tuning be done in a timely and reliable manner?

Second-hand information: cesium has a habit to travel with water and easily deposited in the top soil. So: hot spots on top soil will be formed around every rain-, waste-, interrogation-pipes, ducts, canals. Roads, roof-drainings. This works like a kind of 'enrichment', so such hot spots will appear in less contaminated areas too.

Such hot spots can be neutralized by replacing/removing of top soil. But they might reappear later.

So: evacuations are not practical as most of Japan might be affected up to various levels. They must do regular checks and frequent soil-replacement.

I hope they can develop some really effective soil-decontamination process. They will need it.

 

[jlduh]

In an article dated March 25th dealing with Fukushima Daiichi seawater corrosion issues, Euan Mearns made the following quote :

I found, on a different but somewhat related topic concerning the Daichi reactors, this article (and the links at the bottom of the page) informative about the effects of radiations on aging process of materials:

http://www.lucaswhitefieldhixson.com/accelerated-aging-effects-radiation-materials-fukushima-daiichi

One of the most impressive is the huge increase of thermal expansion effects of irradiated steel:

http://www.nuc.berkeley.edu/courses/classes/NE-220/Introduction%20PDF%20format.pdf SEE PAGE 6/30)

 

[zapperzero]

Can someone confirm if this seawater actually entered the reactor (I mean the pressure vessel)? Or is it somewhere else?

If it's the case, and as i said yesterday, it seems god is recently playing dices in the nuclear game and wins much more than calculated by experts, don't you think?

It is most certainly in the reactor, at least part of it. You see, these reactors only have ONE cooling loop. The water is heated in the pressure vessel, becomes steam which drives a turbine and is then cooled in a condenser, later to be pumped back into the reactor. The condenser itself is cooled with seawater. The seawater is pumped into the condenser, chills the pipes through which coolant flows and goes out back into the sea. Some of the seawater found its way into the coolant loop.

The 400 ton figure is suspect to me. In my mind's eye, I can see them measuring concentration of salts in the coolant loop and saying "oh that's the equivalent of about 400 tons of seawater". No need to tell you how many things may be wrong with that, no?

Also highly suspect is the lack of any mention of radioactive releases into the sea. There should be all sorts of interesting activation products in that condenser, I can't believe that water was going into the coolant loop, but not out again... The reactor (or at least the steam condensation chamber) would have been flooded right sharpish.

Or perhaps that's what happened? They detected the hole by abnormally high water level somewhere?

Those playing dice are the penny-pinchers who defer maintenance and write bogus safety analyses, not the gods.

 

[swl]

Covering the pools to protect them from roof falling down?
Come on, the pool is on the top floor! The cover that has no risk of failing in, combined with instruments to ensure that cooling water level is correct, etc...

So there might not be so much value in having a cover on the pool. I doubt the prompt criticality thing is legitimate concern, but I'm no physicist. I'm not sure what a cover is going to do to protect the spent fuel from terrorist attack either.

... it'd quickly be much cheaper not to have the spent fuel pool be on top floor next to the reactor in first place, eliminating entirely the risk of cascading failure from reactor to spent fuel pool. But the cascading failures were never considered in the risk assessments (which is imo a case of utter incompetence), hence the pool is found next to reactor, on top floor.

I'm guess the fuel pool is located there out of necessity. They can't get the hot fuel out any other way. The location near the reactor allows refueling without removing the fuel from the boric acid. Otherwise there would be an extended shutdown while waiting for the spent fuel to 'cool down.'

 

[ernal_student]

http://ziphilia.net/bbs.cgi/economy/1304793715/detailview#A_DEFAULT

I have used this link to check the Japanese text.

It is not a document from TEPCO (maybe nobody has ever claimed that it was, but I want to mention this just to make sure there are no misunderstandings).

The text is a critical (no, condemning) description of how TEPCO, 40 years ago, after realizing that the weak clay and sandstone in the upper 25m of the building site would have made it necessary to drive foundations as far down as the layer of relatively firm mudstone (泥岩層) below, removed the top portion of the building site, which made for easier access to cooling water and loading facilities for fuel easier. The current design is based on the assumption that a tsunami would at most have a height of 5.7m. The included drawing is self-explanatory.

Respectfully submitted for your consideration, but it seems that none of this is new information or a revelation.

 

[Astronuc]

In an article dated March 25th dealing with Fukushima Daiichi seawater corrosion issues, Euan Mearns made the following quote :

In this earlier post I quoted TOD commenter donshan who spoke authoritatively on corrosion issues:

" I do question the use of seawater cooling. I hope the Japanese have considered the danger they have created by introducing oxygenated seawater into this stainless steel piping and pressure vessel at boiling temperatures. These stainless steels are extremely susceptible to chloride stress corrosion cracking:

Since residual weld stresses and tensile stress in piping, valves, control tubing, etc. are always present, Standard Operating Reactor water quality standards require keeping chlorides at parts per billion levels. Seawater has about 3.5% or 35 grams per liter of salinity! (i.e. 35,000,000 parts per billion)

I have no way of knowing how many days they have before a stainless steel component suddenly cracks, but if it were me, I would be advocating an emergency program to get pure deionzied cooling water back into this stainless steel system ASAP. In laboratory tests in boiling chlorides, cracking of stainless in tensile stress can occur within days- they have at most a few months if they keep boiling sea water in this system and yet another disaster occurs."
http://www.energybulletin.net/stories/2011-03-25/fukushima-dai-ichi-status-and-slow-burning-issues

That is the concern. Basically introducing seawater into the cores probably lead to some damage by corrosion, and even if they had successully cooled the reactor cores, they would have had to decommission the fuel, control rods and core internals. Stainless steel 304 would suffer pitting corrosion and stress corrosion cracking. Zircaloy-2 would be normally resistant to seawater unless there was a fair amount of ferric chloride formed in the cooling water, in which case, Zircaloy would corrode. It is suspected that the seawater did enhance the corrosion of Zircaloy and consequential hydrogen production. However, unit 1 exploded before they introduced seawater, whereas unit 3 exploded after introduction of seawater.

There have been a couple of BWRs with saltwater intrusion. One through some low pressure turbine blades through the condenser which then allowed saline river water to enter the reactor. The salt content was very low (perhaps a few thousand ppm), but the reactor was a reduced power and quickly shutdown. I believe they flushed the system and restarted after they removed the low pressure turbine stage. I don't remember the details of the other since it happened more than 20 years ago.

 

[ernal_student]

Insufficient decontamination of workers and lack of adherence to related rules is being described in this article:
http://mdn.mainichi.jp/mdnnews/news/20110514p2a00m0na014000c.html

 

[zapperzero]

I'm guess the fuel pool is located there out of necessity. They can't get the hot fuel out any other way. The location near the reactor allows refueling without removing the fuel from the boric acid. Otherwise there would be an extended shutdown while waiting for the spent fuel to 'cool down.'

So, we now have two facts:
1. having a spent fuel pool on the topmost floor is stupid risky and
2. it is unavoidable in this reactor design.

The conclusion must be that this reactor design is stupid risky. Which means they all should have been scrapped a long time ago or at least not allowed to go on operating past their design lives (but I'm politicizing again, aren't I? At which point does engineering fact become subject to political debate?).

 

[swl]

On to food testing when they will 'discover' that a good chunk of radioactivity is in samples hundreds times above limit, which are rare, and aren't stopped effectively by traditional random sampling.

Good point. I live near Fukushima and I'm wondering if there is any way I can test for radiation on my own. My spouse and I are particularly concerned about the health of our young children.

We want to know if we can test food, water, ground surfaces and background radiation on our own, or if we can only trust the government to keep us safe.

 

[AntonL]

To contribute to the mud stone / bed rock discussion, I would imagine the the soil beneath the NPP to be very much the same as that what has been evacuated from the mountan, and judging by the steep unprotected slopes it is a fairly solid geological structure, no soil with bolders but a tending towards a homogeneous structure. So ground water leakage would be slow in cracks and layers within this mud stone massif I presume.

 

[Astronuc]

So there might not be so much value in having a cover on the pool. I doubt the prompt criticality thing is legitimate concern, but I'm no physicist. I'm not sure what a cover is going to do to protect the spent fuel from terrorist attack either.

A cover would only serve to keep foreign material or debris out of the pool. The Mk I containment is really to keep the weather/storms/high winds away from the reactor service floor.

I'm guess the fuel pool is located there out of necessity. They can't get the hot fuel out any other way. The location near the reactor allows refueling without removing the fuel from the boric acid. Otherwise there would be an extended shutdown while waiting for the spent fuel to 'cool down.'

Irradiated fuel must be moved under water in order to protect the workers from radation. That is the main reason for the location of the spent fuel pool. The Mk III containment design has the SFP in a separate building and an improved containment structure.

The spent fuel pools are normally cooled. They must accommodate a full core offload which would have significant decay heat compared to fuel which has been permanently discharged.

 

[AntonL]

If you run a windows XP operating system you can simulate and watch the plant parameters unfolding. Download for free PCTRAN pre-configured for Fukushima, or other reactor types, from this site http://www.microsimtech.com/ (It does not work for Vista and above!)

(I think Tepco might have used this for their latest unit 1 meltdown simulation.)

Hers are the studies for unit 1 and 3

http://www.microsimtech.com/Fukushima.html
http://www.microsimtech.com/downloads/Fuku3.htm

and SFP-4 simulation
http://www.microsimtech.com/downloads/Fuku4.html
however it has a mistake, they assumed the unloaded core to be 15 days old instead of 90+days (unit 4 was shut down end November If my memory serves me right)

 

[default.user]

Good point. I live near Fukushima and I'm wondering if there is any way I can test for radiation on my own. My spouse and I are particularly concerned about the health of our young children.

We want to know if we can test food, water, ground surfaces and background radiation on our own, or if we can only trust the government to keep us safe.

Establishes purchasing groups, and tests everything that counts as food.
We did that in Germany in 1986.
The state will not help.
You need an expensive instrument. This can be paid only in communities.
Draws conclusions from the measurements.

regards from germany and sorry my bad english.

 

[Astronuc]

Good point. I live near Fukushima and I'm wondering if there is any way I can test for radiation on my own. My spouse and I are particularly concerned about the health of our young children.

We want to know if we can test food, water, ground surfaces and background radiation on our own, or if we can only trust the government to keep us safe.

One would need to have a Geiger counter with which one could monitor radioactivity, but it will not indicate which isotopes. To discern which isotopes are present requires a gamma spectrometer, which might be available at some universities. Gamma spectrometers are rather expensive.

http://en.wikipedia.org/wiki/Gamma_spectroscopy

One must also have experience in using a gamma spectrometer including how to set it up, calibrate it and use it. A Na-I type would be sufficient.

 

[default.user]

Maybe this site can bring some help.
Calibrated regularly leave.

http://www.chetan.homepage.t-online.de/sonstig/ram63.htm

 

[rowmag]

Well again, even if this a slightly different subject from the Daichi plant, I have a hard time understanding how seawater can enter so easily (i say "easily" just because it just happened...) into a BWR reactor. But I understand that unlike a PWR, in a BWR there is no real secondary circuit (i mean closed loop), so the steam is condensed into water in the condenser (which is cooled by seawater if my understanding is ok) and goes back into the reactor right?

So any leak between the two (the sea water/the steam or condensed water) can theoretically (and practially in this case) lead to either seawater entering the reactor or contaminated water going back to the sea?

This article from Asahi gives an explanation of how the leakage could be one-way:

http://www.asahi.com/special/10005/NGY201105150003.html

According to the article, the seawater is used to cool steam. So a leak in the barrier would lead to water going into the steam side, but not vice versa. The article includes a speculative leakage path sketch:

They mention that the leak was detected by noticing a rise in saline concentration in the re-condensed water. Then they switched to a different cooling system. No explanation of where the 400 ton estimate came from.

 

[jlduh]

So, we now have two facts:
1. having a spent fuel pool on the topmost floor is stupid risky and
2. it is unavoidable in this reactor design.

The conclusion must be that this reactor design is stupid risky. Which means they all should have been scrapped a long time ago or at least not allowed to go on operating past their design lives (but I'm politicizing again, aren't I? At which point does engineering fact become subject to political debate?).

That's also one of the main subjects the documentary from Adam Curtis cited above is considering:

https://www.physicsforums.com/showpost.php?p=3304718&postcount=7448

 

[etudiant]

Good point. I live near Fukushima and I'm wondering if there is any way I can test for radiation on my own. My spouse and I are particularly concerned about the health of our young children.

We want to know if we can test food, water, ground surfaces and background radiation on our own, or if we can only trust the government to keep us safe.

Default_user has it entirely right.
This is not a problem that is effectively addressed at the individual family level, because even if you check the food with a geiger counter, it gives no insight regarding the outside exposure levels.
This is very much a community issue, particularly as the contamination will be patchy, with local hot spots, something the central government with its need for simple measures cannot easily adapt to.
There may be a role for the central government to help localities to add monitoring equipment, but the real work will have to be done locally, to make sure playgrounds and public sites are adequately clean.
The food supply will inescapably be more radioactive than before. Expect maximum permissible levels to be raised, perhaps substantially. Unless Japan is willing to import much more of its food and to shut down farming in a large part of Honshu, the margin of safety will be less.

 

[jim hardy]

Rowmag

that's a nice graphiic you put up to show how seawater gets in.

I used to work in a power plant.
For non power plant folks,
The box under the turbine where the color fades from pink (steam) to blue(water) is the "Condenser".
Of course that's because it condenses the steam coming out of the turbine back into water so you can pump it back into the boiler, in this case a reactor.
It's a lot of water - in my plant we boiled water at the rate of a residential swimming pool every twenty seconds. (~ten million pounds per hour)
The condenser is a huge sealed shoebox affair box maybe twenty feet square by forty or fifty feet long. Thousands of tubes traverse its length , seawater is pumped through the tubes to carry away the latent heat of condensing steam in the box.

I have been in condensers to pick the seaweed and dead eels out of the tubes - when a lot of them get plugged you got to manually clean 'em out. Stinky job.

Well, if even one of those tubes develops a crack or pinhole it'll let seawater into the shoebox where the steam is condensing.
That shows up almost immediately on analyzers that sample the water on its way back to boiler. There are ion exchange type purifiers in that pipe to take care of a small leak, but it's something you monitor for and shut down right away to fix. Men go in, find the leaky tube and plug it at both ends.

If a turbine throws a blade it can sling it down into the tubes and cut a lot of them and that's a LOT bigger leak than usual.

not showing off here, just trying to help non-boiler folks get a handle on what it means.

old jim

 

[etudiant]

Rowmag

that's a nice graphiic you put up to show how seawater gets in.

I used to work in a power plant.
For non power plant folks,
The box under the turbine where the color fades from pink (steam) to blue(water) is the "Condenser".
Of course that's because it condenses the steam coming out of the turbine back into water so you can pump it back into the boiler, in this case a reactor.
It's a lot of water - in my plant we boiled water at the rate of a residential swimming pool every twenty seconds. (~ten million pounds per hour)
The condenser is a huge sealed shoebox affair box maybe twenty feet square by forty or fifty feet long. Thousands of tubes traverse its length , seawater is pumped through the tubes to carry away the latent heat of condensing steam in the box.

I have been in condensers to pick the seaweed and dead eels out of the tubes - when a lot of them get plugged you got to manually clean 'em out. Stinky job.

Well, if even one of those tubes develops a crack or pinhole it'll let seawater into the shoebox where the steam is condensing.
That shows up almost immediately on analyzers that sample the water on its way back to boiler. There are ion exchange type purifiers in that pipe to take care of a small leak, but it's something you monitor for and shut down right away to fix. Men go in, find the leaky tube and plug it at both ends.

If a turbine throws a blade it can sling it down into the tubes and cut a lot of them and that's a LOT bigger leak than usual.

not showing off here, just trying to help non-boiler folks get a handle on what it means.

old jim

Weird, the sea water is just pumped in as is?
Is there a reason that there is no prefilter to keep the eels and seaweed out other than cost?

 

[Jorge Stolfi]

Thanks for finding those. They don't look conclusive to me whether the pipe was damaged or not. I'll keep looking.

IIRC, a previous poster observed that the big venting exhaust pipes of each reactor are separate all the way to the tower tops. So if TEPCO's (?) theory is correct, the "gas treatment system" that supposedly carried hydrogen from #3 to #4 must be something else. Perhaps a system to remove the normal (small) amounts of hydrogen from the steam in the primary cooling loop?

While it seems evident that the explosion happened also in the 4th and perhaps 3rd floor of #4, one should note that the only place in #4 where the main concrete pilars were competely blasted away was on the 5th (service) floor, on the east side of the south wall, right next to the spent-fuel pool. That is rather remarkable because the fuel handling machine and the overhead crane should have protected that corner. Also also the pillars that were snapped away were more closely spaced there and included one extra-wide pillar (which, at lower levels, provides support for the SFP wall and FHM rail).

Finally the bending of the "hockey sticks" on the east side of the FHM could be explained by the latter being briefly lifted by the explosion and hitting the crane rail support on the nearby pillar.

Thus I would wait a little more before buying TEPCO's explanation. The underwater video of the #4 SFP may exclude criticality and an explosion *in* the pool, but in my head it does not yet exclude the SFP as the source of the hydrogen.

If the water level got low enough for the zirconium to get over 800C, but water was restored to the SFP before the zirconium tubes punctured, would the racks or the assembly heads show visible damage?

 

[jim hardy]

"Weird, the sea water is just pumped in as is?
Is there a reason that there is no prefilter to keep the eels and seaweed out other than cost?"

There are screens to act as strainers with maybe 1/2 inch mesh ahead of the big seawater pumps. They get 99% of the stuff. The seaweed in our area was long leafy grass which when it turns sideways oops edit make that endways can get through the screen.

The screens are an endless belt driven by a motor so the stuff comes up, gets washed off them and the screen continues on around on its track.
The doggone eels for some reason want to swim downstream not into the current and a lot of them get around the screens by the track, or squeeze through.
The fish are smarter - they come in near the screens to catch shrimp and then go on their way. Big fish come into eat the little ones - it's an interesting nature show there. And good fishing.

It's a lot of seawater - we had eight seawater pumps each about 175,000 gpm if i remember right.

old jim

 

[elektrownik]

Tepco released many important data: http://www.tepco.co.jp/nu/fukushima-np/