Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[SteveElbows]

Doh. Taken from the end of June 15th TEPCO status update...

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110615_02-e.pdf

At approximately 11:05 am on June 16, we confirmed that one employee from a partner company was smoking without a full mask when he was assembling a crane at the shallow draft quay as preparation work for an installation of a cover for the reactor building of Unit 1. Each density of radioactive materials of particulate and iodine in the air at the site was below measurable limit.
Today as a result of dose evaluation for the employee internal exposure dose was 0.13 mSv and external exposure dose was 0.24 mSv.

 

[clancy688]

Doh. Taken from the end of June 15th TEPCO status update...

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110615_02-e.pdf

He probably wants to make sure that cigarettes won't be the thing which kills him. (We need to check on him over the next fifty years. If he dies of cancer, I'll submit the request for a Darwin Award. :D )

 

[Atomfritz]

But how does all that make it necessary for a second explosion to have happened? There's any number of structures in there that could have shaped the hydrogen blast.

Isn't there a doubt that not only two explosions happened?
It seems so obvious that there were multiple explosions.

Just look at this http://www.tepco.co.jp/en/news/110311/images/110611_05.jpg" from floor 4 of RB#4. (please open in a separate tab, big size!)
Look at the 480V distribution you see in the lower right.

You immediately see that there is something wrong with it.
For example. the covers are blown off. Apparently from the inside!

But - as an electr(on)ics engineer will recognize immediately, the whole thing does not look like an usual electric explosion, It just looks different.

The electric parts do not show the usual damage that happens when a panel blows up due shorts etc. There is no typical sooting that you are used to see in such cases, for example. Cable damage is not recognizable, except for some possible overheating of the white line, but that has probably been at a former occasion and not at this incident, as the corrective measures indicate.

As said above, the protection sheets of the electric distribution appear to have been blown off from inward. The typical bending you can expect in case of external explosion damage is totally missing. In fact, the bending you can see indicates an internal explosion.

So it seemed completely obvious to me that this deformation of the distribution box was due to a secondary, tertiary etc. hydrogen explosion.

Somebody mentioned this picture several pages ago in this thread and asked for comments.
I didn't answer, because I thought that this would be obvious even for a dumbass like me that there have been multiple explosions.
And to me, this picture does not prove much except just that there were multiple explosions...

Can be there any doubt that there was a chain-reaction of explosions?

 

[maddog1964]

Afaik, all larger fabric covered structures are either largely self supported, by increased internal air pressure, or they use a very robust reenforced membrane, with tensioner webbing incorporated into the fabric.
None use flat panels of fabric, which have no strength against perpendicular loads, nor do they use a right angle based framework, because that is just an invitation for eddies and turbulence creating stresses at odd angles, which the poly skin is not well suited for.
The flat frame structure is surely the easiest to put up, especially as there is not enough room to accommodate individual bubbles because the reactors are so close together. Also, a light framework that is easy to erect and is without big foundations probably cannot support much more than a film wall. TEPCO does say the building is temporary, which it is perhaps even more so than might be wished.
Imho, it will at least give TEPCO a dry run to see what the problems posed by a closed containment will be,
but otherwise it seems impractical.

I appreciate you imput and suggestion as I also see many foceable problems, but what I also see on the thread is very detailed summaries as to what will not work and why, but very few answers to the problems. That would lead me to believe that the answers are not quite as simple and the time required to perform them such. So what are the solutions and what time frame is required to perform them. I do have thougths on the process but do not suggest them as I do not have enought site information to understand what all is involved. But I also do not suggest what won't work.

It would be nice to see some solutions offered to as what would work and how to approch it. There maybe a thread that is all ready disscusing this, if so could you please direct me. I do not know how to navigate this forum, usually just read.

 

[biffvernon]

As said above, the protection sheets of the electric distribution appear to have been blown off from inward. The typical bending you can expect in case of external explosion damage is totally missing. In fact, the bending you can see indicates an internal explosion.

So the hydrogen explosion had to start somewhere. Maybe a spark inside your electrical distribution box?

 

[Borek]

So the hydrogen explosion had to start somewhere. Maybe a spark inside your electrical distribution box?

There was no electricity at the site at the time of explosion, that's why reactors went out of control.

 

[etudiant]

I appreciate you imput and suggestion as I also see many foceable problems, but what I also see on the thread is very detailed summaries as to what will not work and why, but very few answers to the problems. That would lead me to believe that the answers are not quite as simple and the time required to perform them such. So what are the solutions and what time frame is required to perform them. I do have thougths on the process but do not suggest them as I do not have enought site information to understand what all is involved. But I also do not suggest what won't work.

It would be nice to see some solutions offered to as what would work and how to approch it. There maybe a thread that is all ready disscusing this, if so could you please direct me. I do not know how to navigate this forum, usually just read.

The site is so crowded and compromised that the whole thing is a proverbial 'can of worms'.
For that, the only solution is a bigger can, one large enough to cover all 4 reactors.
The Chernobyl sarcophagus replacement, sort of a shed on tracks that gets moved over the reactors, seems the most plausible approach, but that is not a 2011 or even 2012 solution.
It may be worth starting a thread on this specific topic, as it poses very interesting issues.

 

[Quim]

Isn't there a doubt that not only two explosions happened?
It seems so obvious that there were multiple explosions.

Just look at this http://www.tepco.co.jp/en/news/110311/images/110611_05.jpg" from floor 4 of RB#4. (please open in a separate tab, big size!)
Look at the 480V distribution you see in the lower right.

You immediately see that there is something wrong with it.
For example. the covers are blown off. Apparently from the inside!

But - as an electr(on)ics engineer will recognize immediately, the whole thing does not look like an usual electric explosion, It just looks different.

The electric parts do not show the usual damage that happens when a panel blows up due shorts etc. There is no typical sooting that you are used to see in such cases, for example. Cable damage is not recognizable, except for some possible overheating of the white line, but that has probably been at a former occasion and not at this incident, as the corrective measures indicate.

As said above, the protection sheets of the electric distribution appear to have been blown off from inward. The typical bending you can expect in case of external explosion damage is totally missing. In fact, the bending you can see indicates an internal explosion.

So it seemed completely obvious to me that this deformation of the distribution box was due to a secondary, tertiary etc. hydrogen explosion.

Somebody mentioned this picture several pages ago in this thread and asked for comments.
I didn't answer, because I thought that this would be obvious even for a dumbass like me that there have been multiple explosions.
And to me, this picture does not prove much except just that there were multiple explosions...

Can be there any doubt that there was a chain-reaction of explosions?

How did this conversation jump from unit 3 to unit 4?

This string started out with me hypothesizing that there had to have been two explosions in the unit 3 event. Now the discussion is apparently about unit 4, but I can't see where the unit 4 subject was introduced.

BTW
The vertical blast at unit 3 was definitely not "hot air rising": the concrete chunks which are seen falling out of the cloud didn't just levitate themselves up there.

 

[Bandit127]

Looks like we will have closed loop cooling of Unit 3's SFP by the end of June. http://www.tepco.co.jp/en/press/corp-com/release/11061511-e.html"

I understand 'flow glass' to mean a visual flow indicator.

The 'hot' side will have desalination but no other clean up installed, so it will remain radiologically hot. Deoxidised make up water will be added along with 'chemicals' to prevent corrosion.

Remote observation will be installed so the operation of the plant can be monitored from the anti earthquake buliding.

They expect the temperature to decrese to 65°C after 1.6 days. Despite the latest data that I can find being a repeat of data taken on May 8th (from http://www.nisa.meti.go.jp/english/press/2011/06/en20110615-3-2.pdf" ) this implies a precise knowledge of the current temperature.

Another step in the right direction anyway. Good.

 

[Atomfritz]

So the hydrogen explosion had to start somewhere. Maybe a spark inside your electrical distribution box?

There was no electricity at the site at the time of explosion, that's why reactors went out of control.

Yes, there was no electricity at that time.
Not inconsistent with the observation of nothing what suggests an electrical explosion.
But - the outward bending of the electric box suggests that there was an -at least secondary- explosion.
In fact, the photo evidence quite excludes that the electric distribution was the source of the explosion chain. Just look the paint remains, this shows that the panel must have exploded after some other (way bigger) explosion in the room.
But, consider how much time hydrogen had time to accumulate in various rooms that were quite well isolated together.
So I think we might have to deal with several explosions in very short sequence.

How did this conversation jump from unit 3 to unit 4?

This string started out with me hypothesizing that there had to have been two explosions in the unit 3 event. Now the discussion is apparently about unit 4, but I can't see where the unit 4 subject was introduced.

I think there is no basic difference between #3 and #4.
Many (almost) closed/insulated rooms that had sufficient time to build up different explosive H concentrations.
Just the explosion daisy chain was different.
So we can look at #4 and learn.

The vertical blast at unit 3 was definitely not "hot air rising": the concrete chunks which are seen falling out of the cloud didn't just levitate themselves up there.

I agree with you. The thing I just wonder about is what explosion was directed upwards. Explosion number what?

 

[jmelson]

So the hydrogen explosion had to start somewhere. Maybe a spark inside your electrical distribution box?

The power had been off for hours. I'm guessing that the only power was DC to relay systems and safety-critical valve acutators. But, if lots of hydrogen is wafting around, it would tend to get inside all spaces that were not hermetically sealed, and an external explosion could then also trigger an explosion inside these spaces.

Jon

 

[MadderDoc]

Is there any real chance at a meltdown or is that just the typical media hype?

Meltdown does not have a distinct definition but I think fuzzy as this concept may be a good case can be made that there is no reason to worry about a meltdown since the dreadful has already happened.

 

[Quim]

The thing I just wonder about is what explosion was directed upwards. Explosion number what?

I don't understand your confusion.
Unit 3 exploded the day before unit 4, so there should be no confusion there.

 

[NUCENG]

No, it just means the tent will be on fire twice a week.

If not, maybe the mystery of smoke fog or water vapor will be solved. Fog doesn't make a good ignition source.

 

[Atomfritz]

I don't understand your confusion.
Unit 3 exploded the day before unit 4, so there should be no confusion there.

You don't understand me.

We have no video evidence of the rb#4 explosion.
But does this mean that it was less spectacular than the #3 one?
And, does this really matter?

#1, #3 and #4 only hicced.
But #2 did more... it burped... it even... maybe sh*t. (please excuse the graphic language ;), I just got inspired by the japanese Nuclear Boy ).
Shouldn't we more look into what really happens/happened there in this so-little-mentioned reactor #2?

 

[Quim]

You don't understand me.

I sure don't understand you.
You posted this question which was about unit#3.

I agree with you. The thing I just wonder about is what explosion was directed upwards. Explosion number what?

Now you are jumping to #4 then #2.

We have no video evidence of the rb#4 explosion.
But does this mean that it was less spectacular than the #3 one?
And, does this really matter?
#1, #3 and #4 only hicced.
But #2 did more... it burped... it even... maybe sh*t. (please excuse the graphic language ;), I just got inspired by the japanese Nuclear Boy ).
Shouldn't we more look into what really happens/happened there in this so-little-mentioned reactor #2?

I don't detect a coherent thought train in all that. Are you trying to obfuscate the issues?

 

[Atomfritz]

I sure don't understand you.
You posted this question which was about unit#3.

Now you are jumping to #4 then #2.

I don't detect a coherent thought train in all that. Are you trying to obfuscate the issues?

Is it really relevant to care about what explosion sequence causes what effects?
Isn't this more a fireworker's topic?

Doesn't this discussion about kaboom effects distract from the real problem, to understand what happened at reactor #2 so that there a containment breach occurred?

Isn't it more important to learn what was the cause of this breach and the releases, to be able to avoid such in future?

 

[Quim]

Is it really relevant to care about what explosion sequence causes what effects?
Isn't this more a fireworker's topic?

Doesn't this discussion about kaboom effects distract from the real problem, to understand what happened at reactor #2 so that there a containment breach occurred?

Isn't it more important to learn what was the cause of this breach and the releases, to be able to avoid such in future?

So you were trying to obfuscate the issue.
That's what I thought.

IMO finding the source of the vectored explosion of the #3 unit is one of the most interesting details of the Fukushima event(s.)

And how do you propose to investigate the source of the explosion in unit 2 when you have no visual information whatsoever and Tepco is laying down a fogscreen about events there?

 

[clancy688]

And how do you propose to investigate the source of the explosion in unit 2 when you have no visual information whatsoever and Tepco is laying down a fogscreen about events there?

C137 release data for Units 1, 2 and 3:

Unit 1: 5.9E14
Unit 2: 1.4E16
Unit 3: 7.1E14

Official report, attachement IV-2, page 7.

The contamination outside the plant is nearly entirely the fault of Unit 2. Unit 1 and 3 may have been eyecandy, but Unit 2 is the real headache.

 

[Quim]

The contamination outside the plant is nearly entirely the fault of Unit 2.

Not as long as the Pacific Ocean lies outside of the plant.
You do realize that this is just a fluke result of wind direction don't you?

 

[Ms Music]

People in Seattle got on average 5 hot particles per day for the month of April, 2011.
(acc. to Arnie Gundersen, Fairewinds Associates)
Question: What's the known effect of around 5 hot particles a day? The most I can find is the following, indicating a "big" risk of leukemias and cancer - from a study done in the 70s:

http://www.nuc.berkeley.edu/node/4459

Or, anyone with nuclear plant experience know anything about hot particles and what their effects might be?

Many thanks.

This is what has been recorded in Seattle since March.

http://www.doh.wa.gov/Topics/japan/monitor-history.htm


I personally am more concerned about the two flights I took, and the full body scans to make sure I wasn't hiding anything in my bra.

 

[Quim]

This is what has been recorded in Seattle since March.

I agree with you about the distant contamination via the jet stream etc.

But lately I am becoming more and more concerned about how much junk is being dumped in the Pacific.

The major portion of the "local" contaminants went out over the ocean.

Then there is the water release, and I don't trust TEPCO to not be dumping radioactive liquids in the ocean on an ongoing basis.

From what we have learned about the geology of the site recently, all the radioactive material which finds its way into the groundwater or runoff water finds its way into the Pacific.

I am growing uncomfortable with this idea. I think there should be somebody there monitoring TEPCO.

 

[swl]

I guess I have to say it again. If you contain the buildings, it allows you to filter the venting instead of letting it drift down wind. That is justification enough. As to hiding what is going on iside a containment "tent," don't you think by now that we already know something bad happened there? If offsite dose rates decline or increase isn't that good enough to tell whether their efforts are working?

All excellent points. Could you please post a link describing the HVAC system they'll be using? I'm curious how they expect to control RH/condensation and temperature while preventing escape of contamination.

 

[Ms Music]

But lately I am becoming more and more concerned about how much junk is being dumped in the Pacific.

I think I read in the last day or two that they have detected trace amounts of radiation in whales off Japan?

 

[MadderDoc]

C137 release data for Units 1, 2 and 3:

Unit 1: 5.9E14
Unit 2: 1.4E16
Unit 3: 7.1E14
Official report, attachement IV-2, page 7.

The contamination outside the plant is nearly entirely the fault of Unit 2. Unit 1 and 3 may have been eyecandy, but Unit 2 is the real headache.

Those figures appear to be the results of a modelling attempt based on a selected subset of possible scenarios, and not based on actual release measurements. You cannot base such a strong statement on that.

 

[Jorge Stolfi]

It seems so obvious that there were multiple explosions. Just look at this http://www.tepco.co.jp/en/news/110311/images/110611_05.jpg" from floor 4 of RB#4. (please open in a separate tab, big size!) Look at the 480V distribution you see in the lower right. [...] Can be there any doubt that there was a chain-reaction of explosions?

Perhaps. But (as old jim observed) the hydrogen probably had enough time to penetrate the electrical boxes. Even if the H2 inside the box and that in the room exploded at the same time, I would expect the box walls and doors to be pushed outwards.

Also, could there have been pressure pulses traveling down the cable conduits from another floor, ahead or behind the main explosion shockwave in the room? The route of the latter (say, from the service floor and through the fuel elevator well) may have been longer or shorter than the route through the electrical pipes.

 

[MadderDoc]

I have posted my theory about the Unit 3 explosion(s) in the "What caused the big explosion at fuku reactor three" thread here;
https://www.physicsforums.com/showpost.php?p=3358847&postcount=104

I was prompted to post this theory by the TEPCO Unit 3 video recently linked on this forum.
Video is at:
http://www.tepco.co.jp/en/news/110311/images/110615_01.zip

Please review and give your opinion at the other thread.

.

The other thread has been locked by a moderator with reference to your posting, so I won't be able to comment any further there until that thread has eventually been unlocked. (Taking it to this thread would seem not right, unless the moderator of this thread specifically would allow it.)

 

[razzz]

Woods Hole https://www.whoi.edu/page.do?pid=68736" link is very good reading (all days) albeit premature on results.

 

[Jorge Stolfi]

My little theory about Unit 2: Molten corium in the primary containment failed the walls to the torus room and/or second floor in the eastern side of the reactor building which resulted in a sudden depressurization and a hydrogen explosion bursting into the turbine building, thus connecting the primary containment of Unit 2 directly with the outside.

It seems unlikely to me that the corium could reach the torus directly. There is a partial concrete barrier inside the drywell, below the RPV (the hollow RPV pedestal), that should constrain the corium to fall at the bottom of the drywell, even if it squirted sideways out from the RPV.

Moreover, the vent discharge galleries that connect the drywell to the torus start a foot or two above the drywell floor (in the #1 blueprints at least, may not be true for #2--#4); so it should take a lot of corium to overflow that barrier.

My guess is that the damage was caused simply by a pressure surge in the primary containment (drywell+galleries+torus, which are basically a single cavity), above the maximum design pressure of ~600 kPa (~6 bar); and the weakest spot (the one that burst) happened to be somewhere in its lower portion.

 

[Jorge Stolfi]

The basement rock of granite type material starts about 800 meters below the power plant and is overlain by the Tomioka Formation of Late Miocene/Early Pliocene sedimentary rocks upon which the the plant is built. ... Now will somebody please tell me that these do not represent any kind of earthquake hazard.

My impression from this thread is this:

* The rock below the reactors is solid enough to support them during any earthquake, even the 3/11 one. Given their "floating box", bottom-heavy construction, I cannot see any significant risk of them collapsing, cracking, or even tilting just because that rock is "not strong enough".

* There is some risk of the reactor buildings cracking if the underlying rock itself cracks and the two sides move relative to each other, as in a fault. Photos of such "mini-faults" on the ground near the reactors have been posted here, so perhaps this scenario has already happened. However, the floating box construction seems to give some protection against that possibility. Also, such fault-like cracks presumably start deep underground, so they should occur with the same relative displacement and same probability, no matter what the rock type.

* The type of rock matters for issues related to underground water (such as leaks into or out of the building). However, the underground water flow at Fukushima Daiichi seems to be slow and directed towards the ocean. So any leakage through that route should not spread inland, and should be small compared to the oceanic contamination that has already occurred.

* The type of rock has a major influence on the amplitude (and hence acceleration) of the ground motion during an earthquake. However there is no need to speculate about this point, since TEPCo very early on published the maximum ground acceleration registered in each building during the 3/11 earthquake (and, IIRC, some of those numbers were well above the values assumed in the plant's design).

Does this make sense?

 

[Quim]

It seems unlikely to me that the corium could reach the torus directly.

I'll chime in with agreement on that. After all that's why GE used a torus for the blow down pool.

My guess is that the damage was caused simply by a pressure surge in the primary containment

Agree here too, this is one of the few things we know about unit #2, although there was a hydrogen explosion, the containment held but developed some leaks apparently.

The odd thing about unit two is that it somehow found enough oxygen inside the primary containment to create a significant explosion.

I have looked into what I believe the environment in #3 was like just before it blew and from what I surmise, it was Hydrogen rich and steam laden but it had to have been very very short of oxygen or it also would have gone off inside containment, (this is probably similar in unit one, but I haven't looked into the data there in detail yet.)

Where did unit #2 get the oxygen from?

 

[Jorge Stolfi]

He probably wants to make sure that cigarettes won't be the thing which kills him. (We need to check on him over the next fifty years. If he dies of cancer, I'll submit the request for a Darwin Award. :D )

Sorry if this straddles off-topic, but... I have seen several reports that many of those people are not professional nuclear workers, but instead people from all walks of life who have been trained only to do specific tasks. I would not be surprised if it turns out that they do not know what a sievert is, or the difference between alpha, beta, and gamma, or that the smoke that he inhales from the cigarette is just as dangerous as the surrounding air.

So that poor worker's lapse may not be entirely his fault.

 

[Most Curious]

Hopefully someone here with first hand knowledge of similar plants will confirm or disprove my thoughts.

There are many piping and electrical penetrations into the drywell and probably some into the torus as well. I am assuming those penetrations are sealed with a flexable material that has a maximum temperature limit, hence the maximum temp. rating of containment. May we assume that with no power, therefore no cooling of containment with a VERY hot reactor inside that most or all of those penetration seals were cooked early on? If so, movement of air into and out of containment would occur by convection if pressure reached atmospheric..

 

[LabratSR]

Hopefully someone here with first hand knowledge of similar plants will confirm or disprove my thoughts.

There are many piping and electrical penetrations into the drywell and probably some into the torus as well. I am assuming those penetrations are sealed with a flexable material that has a maximum temperature limit, hence the maximum temp. rating of containment. May we assume that with no power, therefore no cooling of containment with a VERY hot reactor inside that most or all of those penetration seals were cooked early on? If so, movement of air into and out of containment would occur by convection if pressure reached atmospheric..

Enjoy. CEPA = Containment Electrical Penetration Assembly

http://www.osti.gov/bridge/servlets/purl/5338909-FPWlHy/5338909.pdf

 

[Quim]

My impression from this thread is this:

* The rock below the reactors is solid enough to support them during any earthquake, even the 3/11 one. Given their "floating box", bottom-heavy construction, I cannot see any significant risk of them collapsing, cracking, or even tilting just because that rock is "not strong enough".

* There is some risk of the reactor buildings cracking if the underlying rock itself cracks and the two sides move relative to each other, as in a fault. Photos of such "mini-faults" on the ground near the reactors have been posted here, so perhaps this scenario has already happened. However, the floating box construction seems to give some protection against that possibility. Also, such fault-like cracks presumably start deep underground, so they should occur with the same relative displacement and same probability, no matter what the rock type.

* The type of rock matters for issues related to underground water (such as leaks into or out of the building). However, the underground water flow at Fukushima Daiichi seems to be slow and directed towards the ocean. So any leakage through that route should not spread inland, and should be small compared to the oceanic contamination that has already occurred.

* The type of rock has a major influence on the amplitude (and hence acceleration) of the ground motion during an earthquake. However there is no need to speculate about this point, since TEPCo very early on published the maximum ground acceleration registered in each building during the 3/11 earthquake (and, IIRC, some of those numbers were well above the values assumed in the plant's design).

Does this make sense?

Yes it does, and there is also the porosity issue with the rock under Fukushima.

I've been interested in the geology of the site too, but not because I think the structures are in a mechanically unstable condition, I don't see any problems there. It would have been nice to have the foundation linked with solid granite - that would minimize shake for several reasons. But I can't fault the placement of the site on those grounds.

Where my interests lie are in the drainage and underground water paths. At first I was concerned that this accident could contaminate the groundwater over a huge area of the island with tragic result, but it turns out that that is not the case.

The mountains just to the west have an established runoff pattern which is not the worst of all possible alternatives. This rock has a substantial degree of permeability. The water flow is in a steady and slow passage to the ocean through the rock underlying Fukushima.

So the Japanese groundwater is safe.

 

[jim hardy]

Tyrol and Madderdoc

if you've not already read it - this may help with your hydrogen inquiry.

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/25/028/25028788.pdf

Hydrogen Problems Related to Reactor Accidents
A.Bujor

you may not need to condense the steam, see around p 12.

old jim

 

[a|F]

My little theory about Unit 2: Molten corium in the primary containment failed the walls to the torus room and/or second floor in the eastern side of the reactor building which resulted in a sudden depressurization and a hydrogen explosion bursting into the turbine building, thus connecting the primary containment of Unit 2 directly with the outside.

You lack understanding of the interrelationship between the reactor, drywell, and torus. As far as #2's explosion, I'll stick with this, sourced multiple times in this thread:

"it is realistically assumed that without operator action, reactor vessel pressure control over the long term would be by repeated cycling of the same relief valve.* Because of the high steam mass flux into the suppression pool bay in which the discharging T-quencher is located, significant thermal stratification would be expected. MARCH computations show that the difference between the local and average suppression pool temperatures can be estimated to increase from about 5°C at the beginning of the transient to about 40°C 100 minutes later. This means that the suppression pool would lose its condensation effectiveness; the resulting pressure loads from the SRV discharge of steam and noncondensibles would rapidly increase, leading to a possible rupture of the wetwell which could occur before the overtemperature-induced failure of the drywell."

http://www.ornl.gov/info/reports/1981/3445600211884.pdf

 

[clancy688]

It seems unlikely to me that the corium could reach the torus directly. There is a partial concrete barrier inside the drywell, below the RPV (the hollow RPV pedestal), that should constrain the corium to fall at the bottom of the drywell, even if it squirted sideways out from the RPV.

I posted an old american study of Mark-I containments in my thread which concludes that exactly that may be on of the highest likely happenings in case of meltdowns.

Those figures appear to be the results of a modelling attempt based on a selected subset of possible scenarios, and not based on actual release measurements. You cannot base such a strong statement on that.

Still it isn't the first time that something's claiming that Unit 2 is entirely at fault. I remember such rumours spreading out since March.


And why don't why outsource everything regarding Unit 2 in the news thread? Whether my train of thought may be faulty or not, the thread is there now, let's use it.

 

[Orcas George]

It would be nice to see some solutions offered to as what would work and how to approch it. There maybe a thread that is all ready disscusing this, if so could you please direct me. I do not know how to navigate this forum, usually just read.

If the idea is to contain it, I would first think of containing a smaller area. Every foot that you add to a structure increases its complexity and I think there is some sort of exponential law on sail area. Wrapping a four(?) story building in a typhoon zone is a very ambitious project, making that wrapping air-tight is unheard of, and constructing it all by remote control is a fantasy in my opinion. I can imagine creating a lightweight shell out of sections made of modern FRP composites (kevlar, carbon) but I cannot imagine how to make the sections airtight.

The right answer is to get the hot spots cooled below boiling point using a closed loop system. I would have imagined that they would use the very large portable industrial cooling systems (container sized and larger) that you can rent to respond to industrial emergencies, but there must be some reason that makes that unworkable. It seems like you could drop a bunch of loops with good old-fashioned freon (and then out to an air-cooled refrigerator). Who knows, perhaps freon does something nasty when it is irradiated.

 

[tyroman]

Tyrol and Madderdoc

if you've not already read it - this may help with your hydrogen inquiry.

http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/25/028/25028788.pdf



you may not need to condense the steam, see around p 12.

old jim

Thanks old jim,

Yes I am familiar with the "Flammability and detonation limits" diagram on page 12 of your link.

I first saw it on page 7 of 42 of a document linked at Homer Simpson's post:
https://www.physicsforums.com/showpost.php?p=3231637&postcount=2996

The document:
http://canteach.candu.org/library/20044507.pdf
contained the same "flammability limits curve" I refer to in the "theory" I have been chastized for posting in the Joe Neubarth thread which was established to air "theories" and speculation about "What caused the big explosion at fuku reactor three".

Until that issue is settled, I will defer further comment...

.

 

[NUCENG]

Good explanation, thanks!

One thing I don't understand about theormocouples is why the bimetal wires are usually extended all the way to the voltmeter. Why couldn't they be extended only to some cooler place nearby (such as just outside the concrete enclosure), and then have the signal be carried by copper wires to the meter? That would result in lower resistance for the signal and reduced risk of electrochemical effects along the way.

Or is that in fact how it is done?


Thanks for the compliments and for the thorough analysis. As for them being "open", there is a continuum between having a small leak and being wide open, so it may not be a simple yes/no question. Also, for a small leak, the degree of opening may be sensitive to pressure, temperature, flooding, clogging, etc., and so may vary erratically with time.


Thanks! I think I saw mention of it in this forum, but hadn't the time to check it out then.

Thanks again. I am tempted to include those readings in my plots too, but first one question: do they reflect the conditions inside the reactor, or only of the external contamination? In other words, are those gammas and neutrons mostly created by fission and decay inside the reactor's concrete enclosure? If so, does the spent fuel in the SFP contribute to those readings?

Thanks, that is important information.

As for the temperature sensors, I have seen several diagrams showing their approximate location on the RPV, drywell and torus; but I still miss the key details. Namely, where precisely are the RPV temperature measured: on the outside surface of the RPV, or embedded into its wall? If the former, woud the reading be affected by the drywell atmosphere or by water leaks above the sensor? How far is the "water nozzle" temperature sensor from the nozzles and their feedpipes? And so on...

These details are important, for example, to analyze the pressure x temperature plots. The red boiling curve in those plots is relevant only if the temperature and pressure are measured at the same spot in the fluid. Barring gauge malfunctions, the pressure must be indeed that of the fluid at the gauge's intake point, which should be valid for the bulk space inside (except for the hydrostatic pressure gradient in the liquid-filled part). On the other hand, if the temperature is measured on the outside of a 15 cm thick wall, or even embedded into it, it will be some value intermediate between the temperatures of the two fluids in immediate contact with the wall. Thus, one can easily have superheated steam inside the RPV with a temperature reading well below the boiling curve, or (less likely) liquid water inside with a temperature reading well above the boiling curve.

If you are still looking for thermocouple locations try this:
http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/measuring_positions-e.pdf

 

[Quim]

If the idea is to contain it, I would first think of containing a smaller area.

I agree completely with you on that.

The right answer is to get the hot spots cooled below boiling point using a closed loop system.

But this is an impossibility. The foundations are cracked and leaking. Radiation laden water is being fed into the porous rock below and will spread, and it will end up in the ocean. It is in our best interests to keep the contaminated area minimal.
IMO Trying to pour water on the corium piles is a fools errand.

Here is the profile of the site that was drawn for us by tonio, who responded to the request for geological information (post #9285.)
[PLAIN]http://img30.imageshack.us/img30/5323/geoprofile.png

We need to keep that plume as small as possible.

The piles are now only generating a megawatt of heat each or less.
Its time to let the piles reach a heat equilibrium with their environment.
TEPCO needs to pour sand (or whatever they think will mix with the corium and dilute it further) in with the water.

Then stop watering it.

IMO

 

[zapperzero]

TEPCO needs to pour sand (or whatever they think will mix with the corium and dilute it further) in with the water.
IMO

Leaving aside the rather obvious problems with pumping sand through already-stressed pipes that were designed for ultra-pure water.

How do you propose the mixing would occur? The likeliest scenario is that the molten corium is now covered in a solid crust, due to having been cooled constantly and being a rather poor conductor of heat in the first place...

 

[~kujala~]

I started a new thread for geological issues:

https://www.physicsforums.com/showthread.php?t=507369

 

[NUCENG]

All excellent points. Could you please post a link describing the HVAC system they'll be using? I'm curious how they expect to control RH/condensation and temperature while preventing escape of contamination.

I just downloaded a bunch of stuff related to the erection of the containments and will see if they discuss the filtration system. In filtration of humid air they would probably use an approach similar to the SBGT system which first passes the stream through a heater that lowers relative humidity, then through a HEPA filter to remove particulates and finally through activated charcoal to remove gaseous and ionic radioactivity.

 

[NUCENG]

I started a new thread for geological issues:

https://www.physicsforums.com/showthread.php?t=507369

Just a suggestion cross post a ling to the new thread on the Earth Forum. They have been very responsive to my question about mudstone.

 

[SteveElbows]

I have little inclination to engage in any science based discussions of the Fukushima events external to this thread.

Oh, I am just about to respond to things you and Quim said here about reactor 2, but I'm doing it in the other thread.

 

[MadderDoc]

Isn't there a doubt that not only two explosions happened?
It seems so obvious that there were multiple explosions.

Just look at this http://www.tepco.co.jp/en/news/110311/images/110611_05.jpg" from floor 4 of RB#4. (please open in a separate tab, big size!)
<..> to me, this picture does not prove much except just that there were multiple explosions...

Can be there any doubt that there was a chain-reaction of explosions?

It stands to reason that a hydrogen explosion in a complex physical system like the Fukushima reactor building no 4 may very well not be uniform throughout the building and all of its crevices. It is a matter of language use whether one will label this natural 'graininess' as multiple explosions. When, in relation to another unit, thoughts have been raised regarding 'two explosions' I think that is referring to something else, namely the possibility of two interacting, but physically different mechanisms of explosive force.

 

[SteveElbows]

Looks like the new plan to provide unit 4 fuel pool cooling involves a pretty basic solution, attaching the end of a hose to some railings on the refuelling bridge.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110616_03-e.pdf

Also the levels of Cs-134 and Cs-137 measured at reactor 2 building are not exactly plummeting since they opened the doors and did some filtering & ventilation:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110616_01-e.pdf

 

[SteveElbows]

Also the levels of Cs-134 and Cs-137 measured at reactor 2 building are not exactly plummeting since they opened the doors and did some filtering & ventilation:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110616_01-e.pdf

Oops I probably shouldn't have mentioned opened doors, since that's the next stage:

http://www3.nhk.or.jp/daily/english/16_23.html

Any ideas how they are able to give such positive numbers in that press article? Am I reading the graph wrong or are they using out of date info?