Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[mscharisma]

Cooling has been by spraying, by a flow. It has always been clear that water was disappearing.

Michio Ishikawa was right: http://ex-skf.blogspot.com/2011/04/fukushima-i-nuke-plant-ishikawa-of-jnti.html

Sorry to be so ignorant, but could someone please tell me what Ishikawa might mean by "building a bridgehead"? Many thanks.

 

[zapperzero]

So, as to face wild hypothetical worst-case scenarios, if the one of the cores was on its way to "China" (in some sense taking care of its own long-term waste storage facility), would there be any easily detectable signs for that? How could one tell, apart from plausibility arguments based on reactor sensor readings, that it would not be happening?

Chile, actually. Yes, you'd see either lots of black and gray smoke from burning soil and concrete or a huge steam explosion, possibly followed by same.

 

[jim hardy]

""So I think it's totally possible that during the time Unit 1 was not cooled or not cooled appropriate, the whole core could've molten down and failed the pressure vessel. ""

that requires that the pressure sensors were lying too, in the direction of high?

Which is not impossible, but speculative at this point? Their sense elements are built to measure hundreds of psi not just a few psi. I too am anxiously awaiting reports of their condition.

 

[rowmag]

So, as to face wild hypothetical worst-case scenarios, if the one of the cores was on its way to "China" (in some sense taking care of its own long-term waste storage facility), would there be any easily detectable signs for that? How could one tell, apart from plausibility arguments based on reactor sensor readings, that it would not be happening?

I wonder if flowing through holes in the RPV and landing in the containment vessel might not actually make the core easier to cool. Less "water entombment" depth in the containment vessel needed, for one thing...

Late-night thought.

 

[PietKuip]

Sorry to be so ignorant, but could someone please tell me what Ishikawa might mean by "building a bridgehead"? Many thanks.

Figurative speach, a war metaphor.

The first thing that is needed is "intelligence" (in war terms) - information about the status of the reactors. Two months after the tsunami, we still discover that the "enemy" has been capable of deception with regard to water levels etcetera.

 

[pdObq]

Oops, missed that. From the floor to the bittom of the crane support girders is 24 ft (7.3 m). The shroud would be light enough that the would use the secondary hook on the RB crane. Depending on the size of the lifting ring it might be close. There is also plenty of room on the refueling floor for a purpose built crane to do the lift if the RB crane is too low. The bottom of the roofing girders is about 40 feet above the floor (12.2 m).

NUCENG, thanks for your detailed answers. So, from what you wrote it seems most likely to me that they brought the core shroud in through the refueling tunnel/entrace. It seems to involve fewer complications to use the existing building features than to construct new openings in the building. Also, no such round hole in the roof can be seen in unit 4. Further, a square hole would probably have been easier to cut into the roof than a round one.

Follow-up question (just curious): Do we know what was the status of the core shroud replacement in unit 4?

Also, NUCENG, with all your inside knowledge, would you mind commenting on my question about why the SFPs in these type of BWRs are apparently not covered with concrete shield plugs during normal operation, which I had already brought up twice in this thread, but no one has picked up on it yet?

 

[clancy688]

that requires that the pressure sensors were lying too, in the direction of high?

They must have. Water in Unit 1 has been disappearing. TEPCO keeps pumping and pumping and today they discover that it's 1 m below the fuel bottom.
Either there are low lying leaks in both RPV and containment through which the water escapes and the pressure sensors are sending bogus data, or some kind of magic is letting that water disappear.
Water leak AND rising pressure together is impossible. But water leakage has been confirmed, so the pressure readings must be wrong.

 

[NUCENG]

Chile, actually. Yes, you'd see either lots of black and gray smoke from burning soil and concrete or a huge steam explosion, possibly followed by same.

First the corium needs to melt through the vessel lower head or cause failures in the CRDM penetrations. Then depending on how that happens the corium will melt through the drywell shell and start to interact with concrete. This will release significant amounts of carbon dioxide, carbon monoxide, hydrogen gas, and tellurium. The signature of corium concrete is significantly different from the previous releases. There may be steam explosions if there is sufficient water, but if the release from the vessel is in drips rather than a sudden significant release of liquid corium the steam release may not be explosive.

 

[SteveElbows]

Why can't they say more specifically which one they are talking about. The one of the refuelling tunnel/entrance on the SW corner? That would be most likely from their plan, I guess.

I read a press report that stated very specifically that this door was between the reactor building and the turbine building. Unfortunately I do not recall where I read it, but it seemed to make sense at the time.

 

[mscharisma]

Figurative speach, a war metaphor.

The first thing that is needed is "intelligence" (in war terms) - information about the status of the reactors. Two months after the tsunami, we still discover that the "enemy" has been capable of deception with regard to water levels etcetera.

I assumed that, but since I completely lack technical knowledge (although I'm learning thanks to everyone posting here), I wanted to make sure it's not a term referring to something technical. Many thanks.

 

[M. Bachmeier]

Thank You !

For what its worth, your welcome.

I've always felt that science is an evolving art in the process of understanding and sometimes a single incident can force that understanding to take large and uncomfortable leaps.

If you search this thread for the word "impossible", you might be surprised how many times the contextual assertion has been negated.

 

[pdObq]

I read a press report that stated very specifically that this door was between the reactor building and the turbine building. Unfortunately I do not recall where I read it, but it seemed to make sense at the time.

Yes, the door you are referring to was the "airlock" later called "double door" they opened during the May-8th-mystery-possible-readiation-release event. There was a pdf posted as an attachment by someone many posts back with quite detailed information on what TEPCO plans to do to get the cooling of unit 1 back to work. From that one could see that in a second step they will have to open the door in the SW corner, which they called "big equipment hatch" back then.

I guess one always has to double check what they are talking about or try to infer from the context.

 

[AntonL]

I don't think that "200 GJ" figure is about "melt through" but rather "melt down" - the energy needed to totally transform a normal core into corium. .

Thanks for that correction - I will edit the post accordingly.

 

[MadderDoc]

Chile, actually. Yes, you'd see either lots of black and gray smoke from burning soil and concrete or a huge steam explosion, possibly followed by same.

That sounds a bit like the history of unit 3.

 

[|Fred]

thx MadderDoc, I don't have time to finish that now.. but I'm in the process of doing this

[PLAIN]http://i.min.us/jlgANw.jpg

grr.. i got one color wrong.. on the right picture "the reconstructed thing..

 

[yakiniku]

Any sources of infos?

This link mentions 34 中性子計装管 "neutron instrumentation pipes". Sorry I don't know how to translate this properly and whether it is relevant to your calculations. Maybe someone can translate it better and shed more light on the relevancy.

http://headlines.yahoo.co.jp/hl?a=20110512-00001114-yom-sci

 

[pdObq]

First the corium needs to melt through the vessel lower head or cause failures in the CRDM penetrations. Then depending on how that happens the corium will melt through the drywell shell and start to interact with concrete. This will release significant amounts of carbon dioxide, carbon monoxide, hydrogen gas, and tellurium. The signature of corium concrete is significantly different from the previous releases. There may be steam explosions if there is sufficient water, but if the release from the vessel is in drips rather than a sudden significant release of liquid corium the steam release may not be explosive.

Thanks. In terms of the signature being different from current observations, do you mean different isotopes/nucleides of tellurium should be seen? Haven't there been some traces of tellurium seen in some samples a while ago? I guess the production of CO2, CO and H2 won't be a strong signature unless they measure the full make-up of the air around and inside the reactor buildings (not considering pressure created from that... high pressure readings despite water disappearing, hmmm...), so isotopes would be the strongest, clear signature?

 

[pdObq]

That sounds a bit like the history of unit 3.

Damn, you are right ... :

 

[NUCENG]

NUCENG, thanks for your detailed answers. So, from what you wrote it seems most likely to me that they brought the core shroud in through the refueling tunnel/entrace. It seems to involve fewer complications to use the existing building features than to construct new openings in the building. Also, no such round hole in the roof can be seen in unit 4. Further, a square hole would probably have been easier to cut into the roof than a round one.

Follow-up question (just curious): Do we know what was the status of the core shroud replacement in unit 4?

Also, NUCENG, with all your inside knowledge, would you mind commenting on my question about why the SFPs in these type of BWRs are apparently not covered with concrete shield plugs during normal operation, which I had already brought up twice in this thread, but no one has picked up on it yet?

I haven't seen any reports other than the reason they did a full core offload at Unit 4 was to support the shroud replacement. The reactor was shutdown in October so by March they could have had quite some time to offload the core and get started.

I will see what I can find about SFP design.

 

[Borek]

That sounds a bit like the history of unit 3.

From what I remember (early Astronuc posts) emissions of dust from corium melting through the concrete have easy to detect combination of isotopes, my understanding is this was not observed so far.

 

[M. Bachmeier]

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.

 

[Zallia]

http://www.telegraph.co.uk/news/wor...9502/Nuclear-meltdown-at-Fukushima-plant.html

Didn't see this posted...

 

[mrcurious]

Why can't they say more specifically which one they are talking about. The one of the refuelling tunnel/entrance on the SW corner? That would be most likely from their plan, I guess.

I believe it was the double door between the reactor building and the turbine building.

 

[SredniVashtar]

Sorry if this is old news, just read about it on the BBC website:
http://www.bbc.co.uk/news/world-asia-pacific-13374153

Setbacks at Japan nuclear plant

[...] a spokesman for the power giant said when a faulty gauge had been repaired, it showed water levels in the pressure vessel 5m (16ft) below the level needed to cover fuel rods.
"All the fuel is unprotected at this point and the water levels are below that," said Junichi Matsumoto.
[...] "However temperatures in the reactor pressure vessel have cooled to 100 to 120 degrees so we have come to the conclusion that the fuel mass... is actually not at the proper levels but somewhat below that or even possibly at the bottom of the vessel."
He said there was likely to be a large leak in the pressure vessel, possibly caused by the fallen fuel.
"As for a meltdown, it is certain that it has crumbled and the fuel is located at the bottom (of the vessel)," he added.​

Is this new news (at least from the 'official' point of view) or is it something already well known?

(I see now that Zallia posted the news two messages before mine :-/ )

 

[mrcurious]

Based on this new information from #1, can anyone explain the supposed pressure drop when tepco began filling the PCV and subsequent decision to slow the water fill so as not to create a possible explosive situation where the pressure inside was lower than outside causing oxygen to be introduced in the PVC?

 

[AntonL]

Based on this new information from #1, can anyone explain the supposed pressure drop when tepco began filling the PCV and subsequent decision to slow the water fill so as not to create a possible explosive situation where the pressure inside was lower than outside causing oxygen to be introduced in the PVC?

Theater, Tepco demonstration that they are on top of the situation, but every good suspense thrillers has intriguing turns, this is just one of them.

Sorrry, one of the many Fukushima mysteries that we are not going to solve.

 

[zapperzero]

Sorrry, one of the many Fukushima mysteries that we are not going to solve.

FWIW, I do have a theory: There is core on the RPV floor, producing a massive amount of steam. Water is escaping, through cracks below the corium level. Steam stays in the RPV, under some pressure. When you introduce more water, the steam cools down so the pressure drops.

It's stupid, but it's all I could come up with (I'm having a long day).

 

[jim hardy]

out of synch message here... to unlurk
you mentioned you were curious about a reported radiation increase at time of u-3 mishap?

here's logsheet of readings taken (by hand?), from a 'monitoring car' (with handheld instruments?) according to note at top of page. i guess with so much chaos and no electric power they had to resort to manual data collection? All things considered i'd say they did a good job.

http://www.tepco.co.jp/en/nu/monitoring/11031401a.pdf

Anyhow, i hope the datasheet is of interest to you and this is not a repeat.

 

[unlurk]

message to unlurk

Thanks for the followup.

That isn't any help although that data is interesting in itself.

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

The data at the link you gave was the readings at different locations around the plant. The spike of gamma radiation I assume would have maxed out their instrument and when they reset or re-caled it and tried again everything would have been normal again.

 

[clancy688]

http://www.telegraph.co.uk/news/wor...9502/Nuclear-meltdown-at-Fukushima-plant.html

Didn't see this posted...

Engineers from the Tokyo Electric Power company (Tepco) entered the No.1 reactor at the end of last week for the first time and saw the top five feet or so of the core's 13ft-long fuel rods had been exposed to the air and melted down.

That's a good laugh. TEPCO went into a nuclear plant which suffered a meltdown only two months ago, unscrewed the RPV cap, looked into it, saw the mess, screwed it back on and reported what they saw.