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Japan Earthquake: nuclear plants

by gmax137
Tags: earthquake, japan, nuclear
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rowmag
#7435
May16-11, 05:37 AM
P: 209
Quote Quote by Rive View Post
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
#7436
May16-11, 05:43 AM
P: 56
Quote Quote by razzz View Post
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
#7437
May16-11, 05:49 AM
P: 468
Quote Quote by rowmag View Post
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
#7438
May16-11, 05:50 AM
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P: 23,402
Quote Quote by rowmag View Post
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
#7439
May16-11, 05:59 AM
P: 355
Quote Quote by rowmag View Post
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
#7440
May16-11, 06:00 AM
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P: 494
Quote Quote by MadderDoc View Post
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
#7441
May16-11, 06:08 AM
P: 1,042
Quote Quote by jlduh View Post
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
#7442
May16-11, 06:10 AM
Sci Advisor
P: 916
Quote Quote by SteveElbows View Post
There are only a few images from the period after 3 blew but before 4 went up.

I dont 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
#7443
May16-11, 06:17 AM
PF Gold
P: 1,220
Quote Quote by Borek View Post
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/storie...burning-issues
jlduh
#7444
May16-11, 06:24 AM
P: 468
For those interested, i just posted here:

http://www.physicsforums.com/showpos...&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/adamcurti..._for_atom.html
Rive
#7445
May16-11, 06:26 AM
P: 355
Quote Quote by jlduh View Post
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
#7446
May16-11, 06:29 AM
P: 468
Quote Quote by tsutsuji View Post
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...ushima-daiichi

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

http://www.nuc.berkeley.edu/courses/...F%20format.pdf SEE PAGE 6/30)
zapperzero
#7447
May16-11, 06:43 AM
P: 1,042
Quote Quote by jlduh View Post
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
#7448
May16-11, 06:44 AM
P: 108
Quote Quote by Dmytry View Post
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.

Quote Quote by Dmytry View Post
.... 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
#7449
May16-11, 06:53 AM
P: 34
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
#7450
May16-11, 06:57 AM
Admin
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P: 21,827
Quote Quote by tsutsuji View Post
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/storie...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
#7451
May16-11, 06:58 AM
P: 34
Insufficient decontamination of workers and lack of adherence to related rules is being described in this article:
http://mdn.mainichi.jp/mdnnews/news/...na014000c.html
zapperzero
#7452
May16-11, 07:07 AM
P: 1,042
Quote Quote by swl View Post
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?).


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