Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[unlurk]

I suggest that the exact water level in Unit 1 is actually somewhere between "1m below the fuel rods" and the water table. Tepco cannot be more precise than this, and I don't think we can be either.

My thoughts exactly!

Nope, the Torus is a torus (doughnut shaped) specifically to avoid ever having a load of corium deposited in it and its water contents.

 

[rmattila]

TEPCO is pumping at 6 m³/h water for weeks now. And yet they discovered yesterday that the actual water level is 1m below the fuel rods. That must mean that there's some kind of big leak in the RPV, leading right into the containment.

One thing I've mentioned a couple of times and still find difficult to comprehend is that

• Feedwater lines have been used to feed water to the reactors. I am not familiar with the internals of the GE BWRs, but I suppose the feedwater distributors must be located above the downcomer, as is the case with ASEA BWR:s.
• In GE BWR:s, when the core level falls below 4 feet, the downcomer and core region become two separated volumes, and the water may enter from the downcomer to the core only if its level in the downcomer is higher than -4 feet, i.e. above the tops of the jet pump diffusor pipes.
• It has for a long time been suspected (by NRC and others) that the main circulation pump seals have failed, creating a leakage path out from the downcomer.

In addition, I tried to get confirmation on the hypothesis that the level measurement actually measures the water level in the downcomer volume, not in the core volume: https://www.physicsforums.com/showthread.php?t=485505

Put together, these items suggest there is a possibility that the water pumped into the reactor may never reach the core region, or at least the amount reaching the core may be insufficiently low. I remember asking (message #3244), whether it would be possible to inject water through the control rod piping, thus ascertaining that it reaches the proper location instead of leaking directly out from the downcomer, but no reports of such an action has been reported.

I still keep wondering, how the sufficiency of feedwater has been ascertained, taking into account the uncertainties listed above, and whether the actions reported give a full picture of what's been going on in the reactors during the past 2 months. Surely they must know their plants and take items such as those listed above into consideration, if they were relevant..?

 

[elektrownik]

I remember that they found radioactive ground water first under and around unit 1, this can be hint.

 

[razzz]

Does anyone hear have any knowledge about the (pre-satellite) sound detection devices used to detect nuclear testing.

I watched a documentary some time ago, which explained how specific frequencies indicated nuclear as opposed to conventional explosions.

Been unable to find a source on the internet that specifies what frequencies and other specifics are needed to make such a determination.

And yes, it may have bearing on the discussion here.

Any help or reference to link is most welcome.

http://books.google.com/books?id=sg...vices used to detect nuclear testing&f=false"

 

[WhoWee]

Does anyone hear have any knowledge about the (pre-satellite) sound detection devices used to detect nuclear testing.

I watched a documentary some time ago, which explained how specific frequencies indicated nuclear as opposed to conventional explosions.

Been unable to find a source on the internet that specifies what frequencies and other specifics are needed to make such a determination.

And yes, it may have bearing on the discussion here.

Any help or reference to link is most welcome.

(my bold)
How does this have a bearing on the discussion here?

 

[Rive]

Corium penetrated the RPV. So why shouldn't it be possible for it to penetrate the concrete of the containment bottom as well?

https://www.physicsforums.com/showpost.php?p=3297927&postcount=6864"

It cannot be ruled out that some corium escaped (if it was cooled down without reaching concrete and closed the hole where it escaped), but not enough to interact with concrete.

 

[jlduh]

Water leakage.

TEPCO is pumping at 6 m³/h water for weeks now. And yet they discovered yesterday that the actual water level is 1m below the fuel rods. That must mean that there's some kind of big leak in the RPV, leading right into the containment.
But now there's a problem as well - TEPCO reported that there's not enough water in the containment (hence drywell) to make up for all the water which disappeared. I rule water release by steam out since we haven't seen ANY pictures of steam erupting from Unit 1.
So every day pretty big amounts of water simply disappeared from Unit 1. As for Units 2 and 3, the water was found in the basement, or in the turbine building, or in some pits...
But not for Unit 1. That leaves, at least in my opinion, only one possible way left - down. A hole right through the containment going deep into the ground. And there's only one thing in a nuclear reactor which could create such a hole.

Well, i can tell you that if corium makes a hole in concrete (which is pretty thick at the base) or if it contacted rocks or soil with some water in it, you would have seen it with a lot of gases and steam if there is any water (and there is anyway).

Corium doesn't make a hole quietly without any external effects.

At a much bigger scale (but much less radioactive!) you can get an idea of the result of lava + water (here snow), this was the eruption of sicilian Etna in April, the big steam volutes are generated when the lava flowing on the slopes contacted the snow (kind of phreatomagmatic reaction but at the surface):

http://www.flickr.com/photos/etnaboris/5610119646/

 

[PietKuip]

What I am wondering about is a short spike of gamma radiation which occurred that morning.

My source for this radiation spike is a quote from Kazuma Yokota, a 39-year-old inspector from Japan’s Nuclear Industrial and Safety Agency in the press.
"He shuttled between the offsite and the Dai-Ichi bunker. When the No. 3 reactor housing exploded on the morning of March 14, levels inside the bunker jumped as much as 12-fold, he said, checking dates and times in a pocket diary. "

http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

 

[Luca Bevil]

It has been written that water pumped must have gone somewhere for unit 1.

now I seem to remeber that the 3 radiated workers were working in fact in turbine 1 building and rad levels were not as severe as later found in turbine building 2.

apart from that all contaminted water estimates I've read about did not seem to be making #1 exclusion.

On the other hand we know that no water has been found on the ground floor, not nearly enough is in teh containment vessel...

drywessel and wetvessel (thorus) are connected by steam reliaf pipes .. could be leaking from somewhere around junctions among those pipes and thorus at a level below ground floor but high enough to find its way toward turbine building 1 ?

 

[Borek]

To all: please stay on topic. If you want to discuss Chernobyl start other thread.

 

[clancy688]

45% Corium on its way through or somewhere in the ground below Unit 1 (since there's a major leakage of water from the Containment which we DON'T see - that leaves, at least in my opinion, only the "down" direction as path for the water)

Okay, you're right, I'm wrong. No Corium through the containment probably.

But we all agree that there probably IS Corium in the containment?

 

[BrentLidgard]

First off, there are no more fuel rods.

What is obvious to me is that the water they have pumped in has found its own way(s) out to the ground and the ocean. There are any number of cracks in the foundation and flooring (due to the quake and the aftershocks) of the #3 building but it would be an amazing stroke of bad luck to have one of those cracks to be located directly under the corium.

I don't see any reason to consider that likely, and certainly not probable.

If this is the case, and I am not disagreeing with you at all, why can't the do like they did at Chernobyl and drill through the concrete under the reactor and look for the corium, or are they too afraid to? Or is it just too early to put forth that effort when they really aren't sure what the condidtion of the bottom of the reactor is?

 

[|Fred]

correct me if I'm wrong might but they drilled a hole in Chernobyl to prevent a reaction corium / watter. Not just to have a look.

 

[clancy688]

correct me if I'm wrong might but they drilled a hole in Chernobyl to prevent a reaction corium / watter. Not just to have a look.

That's how I remember it, too. A lake of cooling water arised directly below the corium in the basement.
They feared that the Corium could drop on the lake and create a massive steam explosion which would distribute the reactor, the debris and the core all over the plant vicinity.
Such an explosion would've been way worse than the explosion which destroyed the reactor and spread nuclear materials.

 

[LabratSR]

TEPCO doesn't believe pressure vessel penetrated by molten core. 2nd from last paragraph.

http://search.japantimes.co.jp/cgi-bin/nn20110512x1.html EDIT: I should have included the word "bottom" in the post. "TEPCO doesn't believe pressure vessel bottom penetrated by molten core"

 

[BrentLidgard]

correct me if I'm wrong might but they drilled a hole in Chernobyl to prevent a reaction corium / watter. Not just to have a look.

According to one of the NOVA documentaries they drilled through the wall of the reactor looking for the corium and all they found was graphite and the control rods and no corium. I know it isn't a good thing as of now to breach the reactor itself for obvious reasons, but I am wondering if any of the techniques that were done at Chernobyl could be applied here. As it was stated earlier, thinking out of the box is needed because of the current situation.

 

[clancy688]

TEPCO doesn't believe pressure vessel penetrated by molten core. 2nd from last paragraph.

http://search.japantimes.co.jp/cgi-bin/nn20110512x1.html

That's contradictory to a Kyodo News report:

http://english.kyodonews.jp/news/2011/05/90715.html

Tokyo Electric Power Co., the operator of the crippled Fukushima Daiichi nuclear power plant, revealed Thursday that holes had been created by melted nuclear fuel at the bottom of the No. 1 reactor's pressure vessel.

The company said it has found multiple holes adding up to several centimeters in welded piping. Earlier in the day, it said the amount of water inside the troubled reactor was unexpectedly low -- not enough to cover the nuclear fuel -- hinting that a large part of the fuel melted after being fully exposed.

Edit: New post by EX-SKF - TEPCO press conference regarding holes in the RPV:

According to TEPCO, 8 tons/hour water is being poured into the RPV to cool the fuel. The cumulative amount of water that's been poured exceeds 10,000 cubic meters (tons). On finding the water level inside the RPV was at most 4 meters from the bottom of the RPV. TEPCO calculated the damage to the RPV from the amount of water that's leaked from the RPV, and came up with a possibility of a hole a few centimeters in diameter.

http://ex-skf.blogspot.com/2011/05/tepco-few-centimeter-diameter-hole-at.html And Part 2 of an earlier press conference:

Whether it is a "meltdown":

"We don't believe it is so-called "China Syndrome", where the melted fuels go through the bottom of the RPV, through the bottom of Containment Vessel and the reactor building's foundation. We think the fuel rods, even though they don't retain the original shape any more, remain inside the RPV and are being cooled."

[...]

Possibility that the RPV temperature is low because the melted/collapsed fuel rods have dropped through the bottom of the RPV:

"We cannot deny that possibility."

http://ex-skf.blogspot.com/2011/05/from-tepcos-presser-on-may-12-part-2-we.html

 

[jlduh]

correct me if I'm wrong might but they drilled a hole in Chernobyl to prevent a reaction corium / watter. Not just to have a look.

First they pumped the water (coming from the firefighters who intervened first because of the graphite fire) out of the basement because they were afraid of a big phreatomagmatic explosion when the corium would fall from top room after having eaten the concrete. Then they drilled this tunnel below the basement to install a cooling room (but it was never installed and they filled it with concrete) below the corium. The fear was double:

- that the corium contaminates the big water table below the plant, and then the river, which then goes thousand of kms further with many people around using this water. The contamination would have been spread over very large distance through the water table and the river.

- that the corium again creates a big phreatomagmatic explosion reaching the water table. Some said that the explosion could have released in the air enough contamination for creating conditions incompatible with life for a big part of Europe... In fact i never clarified if this calculation (they were talking about 2 to 5 megatons if i remember well) was assuming just a huge phreatomagnatic explosion or a nuclear explosion (with recriticality in water?), this part of the story is quite fuzzy. Anyway it didn't happen as the corium ended its move in the concrete.

So no, they were not making a tunnel to find the corium ;o)

 

[jlduh]

TEPCO doesn't believe pressure vessel penetrated by molten core. 2nd from last paragraph.

http://search.japantimes.co.jp/cgi-bin/nn20110512x1.html

note also this

Matsumoto also said that, considering the situation with the No. 1 reactor, the water level data from reactors 2 and 3 may not be credible.

 

[tsutsuji]

Video news reports providing a small insight into Areva's water decontamination process

http://www.industrie.com/it/energie/fukushima-comment-areva-va-decontaminer-l-eau.11458 (French)

http://www.youtube.com/watch?v=jvOwzZSH9gI　 (TBS news) (Japanese)

http://www.tv-asahi.co.jp/ann/news/web/html/210511015.html (Japanese)

http://v.youku.com/v_show/id_XMjYyNTcxMDcy.html (NHK, English)

 

[jim hardy]

To Unlurk

Re that semi useless link i gave you-

yes, that tabulation is frustrating because they only took readings every five minutes. And they were roving between measuring points. I assume the gap from 6:30 to 8 AM was shift change.

If one focuses on main gate only it shows a jump in gamma, 36 minutes after explosion it was 10X higher(50 usv) than the 6:30 AM reading(5usv), and lasted less than an hour,,,,

and something caused the guys in the car to go back to main gate and hang out there for an hour before returning to MP's north and west of plant... reckon anything went on besides lunch break?

So all it does is confirm a tenfold increase in readings was seen way out at main gate about time of explosion which cross checks with your report of twelvefold increase in the bunker about same time.
Main gate is ~1km west of plant so indeed they were probably indeed gamma rays as reported because the wind was logged as westerly blowing cloud away from main gate..

too bad all we have is manual readings.

dont mean to beat a dead horse here , just establish it as a defensible data point for you.

 

[jlduh]

According to one of the NOVA documentaries they drilled through the wall of the reactor looking for the corium and all they found was graphite and the control rods and no corium. I know it isn't a good thing as of now to breach the reactor itself for obvious reasons, but I am wondering if any of the techniques that were done at Chernobyl could be applied here. As it was stated earlier, thinking out of the box is needed because of the current situation.

ah ok sorry, you talk about this (small) hole not the big one under the mess! Yes you are right, they finally drilled a hole to check what was inside. There was no real containment at Tchernobyl so i guess drilling the hole was not so difficult. At some point if they really don't know what is going on inside, and if the containment is already breached and at atmospheric pressure, they could try to have a look inside above water level (which is unknown!) with some specialized camera, but it's pretty dark and pretty hot inside, maybe with steam... So they need to provide also some light, and antifog lights! But remember also that the containment is not empty, there are many pipes and stuff inside, so not so easy to see something in these conditions...

 

[Dmytry]

all that drilling and underground 'mining' was very difficult and extremely expensive, and was done very quick. Really, if you look at timeline, or if you look at the vehicle graveyard, you see just how insanely expensive it was. There's no way TEPCO could afford it.

 

[~kujala~]

I think Kyodo News made a mistake concerning holes. When reading all articles this is quite obvious. TEPCO has announced that holes are a possibility whereas Kyodo News made it look like a fact. It's a canard.

 

[LabratSR]

Concerning Corium at Chernobyl and the problems they may face at Fukushima. Somewhat disproves the possibility of China Syndromes under the reactors.

A very good video on the search for the core but you'll have to deal with commercials throughout.

http://www.dailymotion.com/video/xgrtsg_inside-chernobyl-s-sarcophagus_tech

 

[bytepirate]

Interesting analysis. And that "100.0" reading, was not that a code for "off scale"?

unlikely, as there are greater values reported later

 

[unlurk]

I have a question for the forum physicists.

There has been allusions to a view that the material in a SFP cannot go critical.

Why would anybody make this claim?

The fuel which was in the #3 SFP was powering a reactor just before the time it was taken out of the core; on top of that, there were new rods in the inventory in the pool at the time of the explosion on March 14th.

The fuel rods could have been broken up and squished into about any configuration imaginable by the shockwave from the hydrogen explosion hitting the wall of the fuel pond.

Is there an actual physicist posting here who will come to the support of those who claim that a criticality in SFP 3 was an impossibility?

If so, will you show us the math which gives this proof?

 

[jlduh]

Contamination of seawater again on the rising side:

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110512e13.pdf

http://www3.nhk.or.jp/daily/english/13_02.html

More contamination on the grass in towns outside of the evacuation zone:

http://www3.nhk.or.jp/daily/english/13_01.html

3,480 becquerels of radioactive cesium were detected in one kilogram of pasture grass collected on May 5th in Nikko City, Tochigi Prefecture. The figure exceeds the state limit of 300 becquerels. Also, at two different locations in Nasushiobara City, 3,600 becquerels and 860 becquerels of radioactive cesium respectively were detected in one kilogram of pasture grass collected on May 3rd.

Tochigi Prefecture requested farmers in the area where the radioactive substance was detected not to feed pasture grass to livestock.

NOTE THAT NIKKO CITY IS AT AROUND 170 kms FROM THE PLANT (SOUTH WEST) which is quite far... the other one is at around 100 kms same direction.

http://maps.google.com/maps?f=q&sou...8424,140.542603&spn=2.548084,6.696167&t=h&z=8

 

[bytepirate]

Evidence of Earthquake Susceptibility of the Reactors


Evidence 1
On 7th April there was a reported 7.1 (some say 7.4) north of Fukushima that also shook Tokyo. http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc0002ksa.php

...

Evidence 2
On May 1^st, 11.48AM A 4.8 earthquake struck 9.5km from Fuskushima NPP
http://neic.usgs.gov/neis/bulletin/neic_kjal.html

after that the temperature in the reactor 3 rose, something changed!

I believe two earthquake events and two changes from the steady state reactor parameters is proof enough to make the statement that the damaged Fukushima reactors are susceptible to Earth quakes, and is a very worrying thought for trying to get fukushima under control.

agreed for the big one, that also caused a short blackout + evacuation.
the 4.8 might be only coincidence.

list of all quakes in radius 25 km:
CAT YEAR MO DA ORIG TIME LAT LONG DEP MAGNITUDE IEM DTSVNWG DIST

PDE-Q 2011 03 11 073018.45 37.44 141.20 49 6.0 mbGS ... ... 14
PDE-Q 2011 03 11 083109.26 37.47 141.18 37 6.0 mbGS 5.. ... 13
PDE-Q 2011 03 11 084056.14 37.45 140.98 39 5.9 mbGS 7.. ... 5
PDE-Q 2011 03 11 173047.41 37.38 141.14 23 5.0 mbGS 5.. ... 10
PDE-Q 2011 03 11 213421.78 37.39 141.30 14 4.9 mbGS 5.. ... 23
PDE-Q 2011 03 11 231156.79 37.27 140.91 45 4.5 mbGS 5.. ... 20
PDE-Q 2011 03 12 011355.31 37.40 141.28 25 4.7 mbGS 5.. ... 22
PDE-Q 2011 03 12 025236.97 37.21 141.02 36 4.9 mbGS 4.. ... 24
PDE-Q 2011 03 12 025625.57 37.25 141.11 39 4.6 mbGS ... ... 20
PDE-Q 2011 03 12 120408.81 37.37 141.29 46 4.2 mbGS ... ... 23
PDE-Q 2011 03 12 131543.76 37.26 141.18 56 6.2 MwGCMT 3FM ... 22
PDE-Q 2011 03 12 180917.46 37.33 141.27 54 4.6 mbGS 5.. ... 23
PDE-Q 2011 03 14 061832.30 37.45 141.23 35 5.3 mbGS 5.. ... 17
PDE-Q 2011 03 14 183536.73 37.36 141.26 1 4.6 mbGS ... ... 21
PDE-Q 2011 03 15 160338.42 37.35 141.28 35 4.4 mbGS ... ... 23
PDE-Q 2011 03 16 135406.53 37.42 141.23 35 4.8 mbGS 4.. ... 17
PDE-Q 2011 03 17 183811.46 37.23 141.06 41 4.8 mbGS ... ... 21
PDE-Q 2011 03 18 055759.16 37.47 141.09 64 4.4 mbGS ... ... 7
PDE-Q 2011 03 20 195421.32 37.28 140.91 33 4.8 mbGS ... ... 19
PDE-Q 2011 03 20 234317.27 37.21 141.04 53 4.3 mbGS 4.. ... 24
PDE-Q 2011 03 29 070500.24 37.50 141.22 46 4.8 mbGS 4.. ... 18
PDE-Q 2011 04 11 045147.04 37.50 141.23 41 5.0 mbGS ... ... 19
PDE-Q 2011 04 14 235023.71 37.28 140.95 90 4.8 mbGS ... ... 16
PDE-Q 2011 04 17 071252.24 37.52 141.21 54 4.5 mbGS ... ... 19
PDE-Q 2011 04 22 152519.80 37.22 140.98 35 5.2 MwGCMT ..M ... 22
PDE-Q 2011 04 26 040150.66 37.30 141.18 29 4.9 mbGS ... ... 18
PDE-Q 2011 04 30 054701.41 37.39 141.19 34 4.7 mbGS ... ... 14
PDE-Q 2011 05 01 024845.97 37.42 141.15 26 4.6 mbGS ... ... 9

and those wit a magnitude >6 in a 150km radius:
PDE-Q 2011 03 11 055431.94 37.71 141.18 32 6.3 mbGS ... ... 34
PDE-Q 2011 03 11 055807.49 37.62 142.15 50 6.3 mbGS ... ... 101
PDE-Q 2011 03 11 060039.30 38.10 142.49 40 6.2 mbGS ... ... 148
PDE-Q 2011 03 11 060720.88 36.42 141.88 32 6.4 mbGS ... ... 134
PDE-Q 2011 03 11 061301.04 37.21 141.60 40 6.2 mbGS ... ... 55
PDE-Q 2011 03 11 061540.92 36.27 141.11 48 7.9 MwUCMT 8FM ... 127
PDE-Q 2011 03 11 071458.82 36.59 141.82 24 6.3 mbGS 5.. ... 116
PDE-Q 2011 03 11 072812.36 36.82 141.82 28 6.1 mbGS ... ... 96
PDE-Q 2011 03 11 073018.45 37.44 141.20 49 6.0 mbGS ... ... 14
PDE-Q 2011 03 11 081207.26 36.57 141.49 39 6.2 mbGS 5.. ... 102
PDE-Q 2011 03 11 081924.38 36.17 141.56 6 6.5 mbGS 5F. ... 147
PDE-Q 2011 03 11 083109.26 37.47 141.18 37 6.0 mbGS 5.. ... 13
PDE-Q 2011 03 11 152008.19 36.40 141.86 52 6.0 mbGS ... ... 135
PDE-Q 2011 03 12 014715.40 37.59 142.65 20 6.5 MwGS ..M ... 143
PDE-Q 2011 03 12 131543.76 37.26 141.18 56 6.2 MwGCMT 3FM ... 22
PDE-Q 2011 03 12 232448.78 38.05 141.72 15 6.1 MwGS 6.M ... 91
PDE-Q 2011 03 14 061235.40 37.78 142.46 10 6.1 MwGCMT 5.M ... 131
PDE-Q 2011 03 15 132756.63 37.58 142.24 28 6.1 MwGCMT ..M ... 107
PDE-Q 2011 03 22 091906.29 37.33 141.79 31 6.3 MwGCMT ..M ... 67
PDE-Q 2011 03 27 222358.60 38.40 142.10 17 6.2 MwGCMT ..M ... 143
PDE-Q 2011 03 29 105433.30 37.42 142.26 15 6.1 MwUCMT ..M ... 108
PDE-Q 2011 04 07 143243.28 38.28 141.57 42 7.1 MwUCMT ..M ... 105
PDE-Q 2011 04 11 081612.77 36.99 140.41 11 6.6 MwUCMT ..M ... 73
PDE-Q 2011 04 12 050742.28 37.11 140.58 10 6.0 MwGCMT ..M ... 53

obtained here: http://earthquake.usgs.gov/earthquakes/eqarchives/epic/epic_circ.php
location of plant: Latitude: 37.423N Longitude: 141.033E

i quote the result here, as the website often does not give correct results...

local values would be more useful, but there seem to be none available.

 

[Caniche]

What I am wondering about is a short spike of gamma radiation which occurred that morning.

What I am wondering is what effect a burst of Gamma radiation would have on a stockpile of new and spent fuel rods ? Any whizzkids know the projected results? surely it must have been modeled given 7 reactors and sfp's in close proximity? I mean risk assessment and all that.

 

[Caniche]

Contamination of seawater again on the rising side:

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110512e13.pdf

http://www3.nhk.or.jp/daily/english/13_02.html

More contamination on the grass in towns outside of the evacuation zone:

http://www3.nhk.or.jp/daily/english/13_01.html



NOTE THAT NIKKO CITY IS AT AROUND 170 kms FROM THE PLANT (SOUTH WEST) which is quite far... the other one is at around 100 kms same direction.

http://maps.google.com/maps?f=q&sou...8424,140.542603&spn=2.548084,6.696167&t=h&z=8

Could that be why Naoto Kan has chosen this precise period to talk about the need to maintain central administrative functions and the possible need to relocate the capital city?

 

[unlurk]

My source for this radiation spike is a quote from Kazuma Yokota,
http://www.bloomberg.com/news/2011-04-25/japan-s-terrifying-day-saw-unprecedented-exposed-fuel-rods.html

Thanks for the link, I was looking for that one.

 

[mrcurious]

http://www3.nhk.or.jp/daily/english/13_03.html"

No.1 reactor is in a "meltdown" state

Salient comments;

"Tokyo Electric Power Company says the No.1 reactor at the Fukushima Daiichi nuclear power plant is believed to be in a state of "meltdown"."

"But it suspects the meltdown created a hole or holes in the bottom of the reactor causing water to leak into the containment vessel."

"It also suspects the water is leaking into the reactor building."

Friday, May 13, 2011 05:21 +0900 (JST)

 

[MiceAndMen]

The pathway for hydrogen from the RPV to the primary containment through the drywell cap seal, into the upper primary containment and then into the upper floor has been the likely scenario since the beginning, as was the presence of a large amount of leaked hydrogen in the upper building. I agree that concrete slabs would not be hydrogen tight, and, that neither would a failed seal on either of the transfer gates. What I don't see is why a lifting force on the concrete slabs would reinforce the strength of the underlying tongue-in groove arrangement of the concentric segments of the upper primary containment. Further, a slow leak of hydrogen is entirely a different thing from a large explosion originating in the drywell. I am no expert here, but if the pressure within the primary containment suddenly reached explosive levels, then it would seem that that explosion will tend to first vent through, and then, literally destroy the weakest part of the containment.

Overpressure in the drywell would first be vented to the torus, which is one reason why I can't accept (yet) that the cap would unseat and release gas before other primary containment failure. Proceeding further, even if the cap did unseat and release gas, as soon as enough was released the internal pressure would drop below the threshold needed and the seal would be re-established. Not sure about the time for that to happen, though, and how much gas would need to be released to reduce the pressure far enough.

What if the weakest part of the cavity above the cap was the path to the equipment pool? There would be no hydrostatic pressure at all on the other side of that barrier if the pool was empty.

Will respond more after digesting the rest (and dinner!).

 

[unlurk]

Could that be why Naoto Kan has chosen this precise period to talk about the need to maintain central administrative functions and the possible need to relocate the capital city?

Why would there be a need to relocate Tokyo?
I see nothing remotely threatening that city.

Tokyo is seldom downwind from Fukushima.