Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[TCups]

REGARDING THE EXPLOSION & WRECKAGE AT UNIT 3

Still wondering if anyone else thinks this is more like a jet of steam venting than a more diffuse cloud of steam rising from a pool of hot water.

If the orientation is correct as per jensjakob's observation, post #576, could this jet of steam be from the region of the "cattle chute" transfer channel between the SPF to the left and the region of the reactor vessel on the right?

Very interesting in light of minerva's post #588 regarding the pump and seal failure on the gate as a potential source for leakage of the fuel in the SFP.

Could water leakage from the SFP into the reactor containment contribute to a steam explosion upward out of the reactor containment, from around the outside of the reactor vessel, and if not blowing the plug, then perhaps blowing out the gates on the chute? Might it then also blow out a good portion of what was in the SFP as well as the the roof over the SFP, leaving a residual venting steam leak from the gate region, but leaving the reactor vessel intact?

What else might have resulted in the very different, vertical blast dynamic at unit 3 if the reactor vessel is still intact and venting steam?

Whatever blew vertical should have at least blown a hole through the roof, if not blowing the roof off completely, as well as blowing the side panels outward. The only obvious candidate for a hole in the roof looks, after the subsequent collapse, to be over the region of the SFP. Could a sidewise and upward blast out of the gate and upward out of the SFP blown out 3 walls with the wall opposite the pool and reactor gate being spared, then collapsing inward, together with what was left of the roof?

It looks like at least two layers of steel girders have collapsed over the region of the reactor at unit three. One is a portion of the roof, I believe. The other is diagonally oriented with respect to the roof girders and appears to be part of the upper wall structure over the reactor area, but if so, it appears to me it would have had to have fallen inward rather than being blasted outward.

What is the significance of two fuel cask transfer trucks out back of unit 3? Were they likely to have been uploading or downloading fuel?

So many questions. So few answers.

 

[swimmer]

An observation, the US media seems to have "moved on" to the Libyan and other issues, there are no followup or current stories edit: (Google News, 9: 45 EST) regarding containment/cleanup status of the crippled reactors in Japan. I guess I should not be surprised, but I find it odd to say the least, considering the long term implications of this disaster for Japan and the world.

Rhody...

Rhody, and anyone else interested, CNN has been continuously streaming NHK World TV online with interpreters translating audio into English live. This evening (Japan time) there was a detailed report on state of affairs in all 6 plants at Fukushima Daiichi. I only caught the end of it but NHK usually repeats these during the night. (I'll post a link as soon as I find a video of it, I can only give a summary here). Apparently TEPCO is working hard and making progress but this situation is a long way from stabilized. I am impressed with NHK, calm reporting, experts giving proper information, clear explanations of all the courses of action and risks involved. They had the big model of the entire facility showing some progress on getting power supply from outside to plant no1 and no3 as well as a big model of a single plant. They emptied a bottle of blue water into a SFP and pointed out the pipework needing to be able to circulate this water to clarify the cooling function, lots of technical information explained very swiftly and effectively. But even for a curious amateur like me, it was a lot to take in. It's also sobering news. Workers are apparently having to work with flaslights in the dark in high levels of radiation, there are cooling problems with reactors no1,2,3 and 4. Unfortunately, they're now having trouble getting water inside plant no2 because the exterior walls are still intact. The mind boggles. Reactor no 4 seems to be especially worrying.

[PLAIN]http://img683.imageshack.us/img683/9301/nhk2011032021301.png

[PLAIN]http://img153.imageshack.us/img153/2687/nhk2011032021302.png

[PLAIN]http://img688.imageshack.us/img688/9691/nhk2011032021303.png

[PLAIN]http://img705.imageshack.us/img705/2025/nhk2011032021304.png

Also, NHK reported minutes ago a brief TEPCO press conference: IR images taken at altitude 900m have shown that all fuel rods are below 100°C. Official added that cooling effort needs to be continued. No IR images were shown

All these despatches are missing exposure data.

 

[swimmer]

Also, NHK reported minutes ago a brief TEPCO press conference: IR images taken at altitude 900m have shown that all fuel rods are below 100°C. Official added that cooling effort needs to be continued. No IR images were shown

All these despatches are missing exposure data.

I forgot to add: There was NO mention of IR readings of any of the reactors.

 

[2ndResponder]

On the question of viewing the damage... Given the radiation, both human beings and electronics are not good ideas, and even moving parts may be iffy. What do you think of this idea:
* Platform -- suspend a lighter-than-air balloon over the site, tethered to 3 very long cables on ground-based winches, so that by altering their lengths the position of the balloon can be changed. ( I think the US uses single-cable tethered balloons to view parts of the gulf coast already.)

* Viewing mechanism: Use a large diameter lens to focus light down to a fiber-optic cable, 400 meters in length (or whatever is required), to a ground-based image intensifier.

Would that work? All the moving parts and electronics are ground-based and can be shielded with heavy materials.

 

[Astronuc]

I read some pretty harsh comments on TEPCO and the 'operators'.

Bear in mind that the folks at the plant have family and homes in the area of the plant, so besides themselves, they have a significant personal stake in minimizing the consequences of the Fukushima event. Depending of where they live, I wonder if any lost homes or family members in the tsunami. I can't imagine having to stay on site and keeping one's mind on the emergency, while trying to find out if one's family is OK, and perhaps not hearing for hours or days.

With respect to surveillance, systems already exist, both mobile robotics and small submersible camera systems, that can be placed in units. They could also use reflector telescopes from a distance, and small radio-controlled helicopters, balloons or booms/cranes to hold cameras at distance.

The biggest impediment will be the debris from the collapsed structures that will have to be removed. At some point, new systems systems will have to be in place to remove the plug and heavy equipment.

 

[AntonL]

It is reported that 40 tonnes of sea water have been pumped into the spent fuel pool of reactor unit 2.

NHK also reports of very high radioactive debris lying around reactors 3 and 4.

A military tank (as in war) will now be deployed to bulldoze the area and shift this debris, the thick armor plating hopefully shielding the operator from the radiation.

 

[Astronuc]

REGARDING THE EXPLOSION & WRECKAGE AT UNIT 3

Still wondering if anyone else thinks this is more like a jet of steam venting than a more diffuse cloud of steam rising from a pool of hot water.

We need more details, or a direct observation, otherwise we can only speculate.

One possibility would be a leak somewhere - perhaps a valve. Perhaps the leak is bypassing the plug near the transfer canal. But that is pure speculation.

Could there be cracks/leaks in the primary containment?

 

[rhody]

There is no more detail!

Please read in full content, I started with:
Now I must be careful in italics below is just my imagination and speculation and not reality:
(I now have highlighted this in original post)

I was just imagining what resources and options that disaster management had - I repeat just imagination

As such, to my knowledge, No such proposal as Rhody mentions was made to Mrs Clinton !

AntonL,

I understand and apologize, imagination is a wonderful thing, it comes up with amazing insight and creative solutions to what at first can be believed are impossible problems. I retract my statement about the briefing and advisement for Secretary of State Clinton... but it is certainly within the realm of possibility, hats off to your imagination.

I will leave it up to you, but if you want to delete the original speculation I will remove my response to it to make sure nothing can be misinterpreted, your call.
I will check back for your reply...

Rhody... sheepish... crawls slowly under a rock...

 

[swimmer]

In case CNN has stopped NHK live stream (it seems so), go to:
"[URL
[/URL]
or
http://www3.nhk.or.jp/nhkworld/index.html"

They're bringing in a tank to clear debris, big problems with getting water and power inside plant no2. Not even light inside. So we're not the only ones 'in the dark', we're only luckier than the TEPCO workers.

 

[AntonL]

I will leave it up to you, but if you want to delete the original speculation I will remove my response to it to make sure nothing can be misinterpreted, your call.
I will check back for your reply...

please check my original post now pointing out in bold red letters that what follows is just my imagination - I would leave it because a hydrogen explosion in unit 4 seems so unlikely if SFP is full and had apparently with enough water after explosion according to TEPCO statements.

 

[romillyh]

Just a plea to all contributing to this excellent thread to pls keep posting until we are through this and situation is stabilized with some confidence. The combination of expertise, sheer detail, and sharp questions is my reality check. Thanks especially to Astronuc, of course, but also to e.g. TCups for sticking to guns -- as well as others who reason knowledgeably for or against various speculations. And to swimmer for the NHK links. It's all most helpful.

Brief background: Am using info here and elsewhere to try to help 3 families in Tokyo decide what moves to make, if any. One father has already moved his family (wife & 2 kids) down to Ehime prefecture on Shikoku, a decision he made early on before input from me. He's desperate to move them out of the country altogether, but can't. Another with family I haven't heard from since 14th, so I assume he's also left Tokyo and can't get to a computer. The third is teacher of a well-known young pianist who has 3 recitals imminent in Japan and then another at the Japan Festival in New York April 3rd, so they have little option but to stay with the pianos in Tokyo!

A cousin of mine plus (Japanese) family fled Japan Tuesday on a flight booked last year. They are so relieved to be out. Ironically they were worried about the predicted Great Tokai quake, supposed to be coming in the south. This quake in the north was apparently quite unexpected.

So, please keep posting. It's potentially a lifeline, and much appreciated.

 

[TCups]

We need more details, or a direct observation, otherwise we can only speculate.

One possibility would be a leak somewhere - perhaps a valve. Perhaps the leak is bypassing the plug near the transfer canal. But that is pure speculation.

Could there be cracks/leaks in the primary containment?

Astronuc:

The larger point is that steam is being generated somewhere and at unit 3, that steam's source is almost certainly the reactor. All reports seem to indicate that the reactor vessel at 3, while it may be damaged, isn't melted down such that the melted core contents went through the bottom of the reactor vessel and into the pool of water below, resulting in a "champaign cork" explosion, ejecting the plug.

So if I proceed from the assumption, which seem reasonable, that the reactor vessel and plug are intact, I am still left with two fundamental questions: why was the blast at 3 so large and so vertical compared to units 1 & 4? What mechanism might be responsible.

The pictures suggest structural damage to the roof over the region of the SFP, and that the deep pool may (and I stress may) have been the source of the vertical component of the explosion. I must assume that the explosion was a combination of H2 (coming from the reactor, not the fuel in the SPF) and steam. The transfer chute seems to be a possible connection.

Here is a hypothetical question or two for which you may have an answer: If a portion of the cooling water in the SFP leaked through the transfer chute after the seals on the gates of the chute failed, then where does the leaked water go? What if any consequence might that have other than lowering the level of water in the pool faster than evaporation?

 

[swimmer]

In case CNN has stopped NHK live stream (it seems so), go to:
"[URL
[/URL]
or
http://www3.nhk.or.jp/nhkworld/index.html"

NHK now broadcasting the status report I mentioned earlier.

 

[Naty1]

Drinking water sample reading in Tokyo:

"The sample contained 1.5 becquerals per kg of iodine 131, well below the tolerable limit for food and drink of 300 becquerals per kg, the government added."

(I lost the news report..)

Anybody know what a typical reading was in Tokyo water BEFORE all the nuclear "meltdown" hype?

 

[swimmer]

Drinking water sample reading in Tokyo:

"The sample contained 1.5 becquerals per kg of iodine 131, well below the tolerable limit for food and drink of 300 becquerals per kg, the government added."

(I lost the news report..)

Anybody know what a typical reading was in Tokyo water BEFORE all the nuclear "meltdown" hype?

From what I remember (have to check) this was the first time ever that radioactive iodine was detected in tap water Edit: in tap water in Tokyo since testing began in 1990. (Before = 0)

 

[swimmer]

Drinking water sample reading in Tokyo:

"The sample contained 1.5 becquerals per kg of iodine 131, well below the tolerable limit for food and drink of 300 becquerals per kg, the government added."

(I lost the news report..)

Anybody know what a typical reading was in Tokyo water BEFORE all the nuclear "meltdown" hype?

Can't find Tokyo detection records. The 'detected for the first time since testing began in 1990' is apparently in Gunma. Read here:
http://mdn.mainichi.jp/mdnnews/news/20110320p2g00m0dm023000c.html"
http://english.kyodonews.jp/news/2011/03/79683.html"

Whatever the levels before, the most recent data matter most. My advice would be: stay away from the tap water.

 

[AntonL]

Drinking water sample reading in Tokyo:

"The sample contained 1.5 becquerals per kg of iodine 131, well below the tolerable limit for food and drink of 300 becquerals per kg, the government added."

I would like to see the officials face when asking him to drink a litre of water with 300 becquerals per kg. (I would feel very uncomfortable like longterm Russian roulette.)

In Canada 6 Bq/L are allowed, check http://www.env.gov.nl.ca/env/waterres/regulations/policies/water_quality.html"

In summary the Canadian limits are and we know that 1L = 1kg
Cesium-134 7 Bq/L
Cesium-137 10 Bq/L
Iodine-125 10 Bq/L
Iodine-131 6 Bq/L
Molydenum-99 70 Bq/L
Strontium-90 5 Bq/L
Tritium 7,000 Bq/L

 

[Maxion]

Heh 1 Bq is nothing. Your own body is "radioactive" to the amount of thousands of Bq.

The water is NOT dangerous.

 

[Astronuc]

Just a plea to all contributing to this excellent thread to pls keep posting until we are through this and situation is stabilized with some confidence. The combination of expertise, sheer detail, and sharp questions is my reality check. Thanks especially to Astronuc, of course, but also to e.g. TCups for sticking to guns -- as well as others who reason knowledgeably for or against various speculations. And to swimmer for the NHK links. It's all most helpful.

Brief background: Am using info here and elsewhere to try to help 3 families in Tokyo decide what moves to make, if any. One father has already moved his family (wife & 2 kids) down to Ehime prefecture on Shikoku, a decision he made early on before input from me. He's desperate to move them out of the country altogether, but can't. Another with family I haven't heard from since 14th, so I assume he's also left Tokyo and can't get to a computer. The third is teacher of a well-known young pianist who has 3 recitals imminent in Japan and then another at the Japan Festival in New York April 3rd, so they have little option but to stay with the pianos in Tokyo!

A cousin of mine plus (Japanese) family fled Japan Tuesday on a flight booked last year. They are so relieved to be out. Ironically they were worried about the predicted Great Tokai quake, supposed to be coming in the south. This quake in the north was apparently quite unexpected.

So, please keep posting. It's potentially a lifeline, and much appreciated.

I'm hoping to go to Fukushima Daiichi, or as close as allowed, as soon as feasible.

 

[TCups]

On the live feed, it was just confirmed that there were high-level radioactive debris on the ground around unit 4 hampering the efforts to spray water on the reactors and SFP. Tanks with bulldozer blades are to be used to clear the debris to make access possible. If the reactor cores are intact and the radiation released was only from vented steam, I wouldn't expect high-level debris requiring shielded metal tanks to remove them to be necessary. This sounds more like the contents of the SFPs may be scattered about, does it not?

What other high level debris might be scattered by explosions that spared the reactor cores other than spent fuel rods?

 

[AntonL]

Heh 1 Bq is nothing. Your own body is "radioactive" to the amount of thousands of Bq.

Yes evenly distributed over your 80 Kg and not concentrated at one spot in your pancreas!

 

[2ndResponder]

It is reported that 40 tonnes of sea water have been pumped into the spent fuel pool of reactor unit 2.

NHK also reports of very high radioactive debris lying around reactors 3 and 4.

A military tank (as in war) will now be deployed to bulldoze the area and shift this debris, the thick armor plating hopefully shielding the operator from the radiation.

What's with the "hopefully shielding"?

In the large scale of things it's a small percent, but I still don't understand why machines with humans inside them are being used instead of remotely-operated equipment. Are people that much cheaper than robots? Or, to be totally financial, are people (after health care and burial costs) that much cheaper than robots? Or are there simply no such robots -- in which case, isn't it a "lesson learned" that it's time to fund development of them?

 

[swimmer]

Heh 1 Bq is nothing. Your own body is "radioactive" to the amount of thousands of Bq.

The water is NOT dangerous.

Correct, the water itself is safe.

The radioactive isotope I-131 in your water is dangerous, especially in low doses.

http://en.wikipedia.org/wiki/Iodine-131"

 

[2ndResponder]

On a very pragmatic incident management angle, lack of a ready supply of affordable, disposable (if need-be) remotely-controlled eyes and hands seems very likely to have contributed to an otherwise needless delay in determining what's going on. That's both dangerous and, in the long-run, probably much more expensive than the servo-robots would be.

 

[swimmer]

I'm hoping to go to Fukushima Daiichi, or as close as allowed, as soon as feasible.

Wow, really? To assist?

 

[Astronuc]

Wow, really? To assist?

I'm anxious to analyze the cores and fuel behavior, and fuel from SFPs.

 

[AntonL]

I'm hoping to go to Fukushima Daiichi, or as close as allowed, as soon as feasible.

Your luggage will be very heavy with radiation free food and bottled water

Fukushima residence have been advised not to drink tap water!

 

[TCups]

On the live feed, it was just confirmed that there were high-level radioactive debris on the ground around unit 4 hampering the efforts to spray water on the reactors and SFP. Tanks with bulldozer blades are to be used to clear the debris to make access possible. If the reactor cores are intact and the radiation released was only from vented steam, I wouldn't expect high-level debris requiring shielded metal tanks to remove them to be necessary. This sounds more like the contents of the SFPs may be scattered about, does it not?

What other high level debris might be scattered by explosions that spared the reactor cores other than spent fuel rods?

The helicopter fly over spent a lot of time looking at this debris field and at something on the top of this building. Curious.

What sort of blast might scatter spent fuel rods out of a SFP? One venting through the channel between the SFP and the reactor containment?

Astronuc: I hope you make it -- God speed and take care. Be sure to take a laptop and check in with us. Anyone else from your team likely to make the trip?

 

[swimmer]

I'm anxious to analyze the cores and fuel behavior, and fuel from SFPs.

I can imagine. Also, to me it seems quite an overwhelming amount of cores and fuel rods to study. Lots of work to be done, lots of benefit to be gained from those willing and able to do the work.

 

[Reno Deano]

How does Iodine get into tap water so quickly? Most drinking water system facilities have been shut down by the earthquake and Tsunami. Also, most domestic drinking water supplies are a relatively closed system with many types of filtration systems, including final carbon beds, which would filter out the Iodine. Sounds fishy to me. Everyone probably went to bottled water following the Tsunami and destruction.

 

[M. Bachmeier]

How does Iodine get into tap water so quickly? Most drinking water system facilities have been shut down by the earthquake and Tsunami. Also, most domestic drinking water supplies are a relatively closed system with carbon adsorbers, which would filter out the Iodine. Sounds fishy to me. Everyone probably went to bottled water following the Tsunami and destruction.

It makes you wonder if the samples were contaminated during testing?

 

[Reno Deano]

The helicopter fly over spent a lot of time looking at this debris field and at something on the top of this building. Curious.

What sort of blast might scatter spent fuel rods out of a SFP? One venting through the channel between the SFP and the reactor containment?

Astronuc: I hope you make it -- God speed and take care. Be sure to take a laptop and check in with us. Anyone else from your team likely to make the trip?

Since the blast was not likely below the spent fuel pool (pool structure would mitigate the blast force), the spent fuel elements due to their weight would not be ejected from the racks which are a tight fix due to seismic considerations.

 

[MadRocketSci2]

So you're going to take a bunch of half-starved, injured, freezing refugees and tell them not to drink the water because there is a remote possibility that they might get cancer someday if the levels of radioactives detected were 300 times what they are? This is the kind of insanity about radiation that is going to get more people hurt than the disaster ever will.

There might be other good reasons not to drink the water (quite a lot of things broke during the quake and the tsunami - there's probably all sorts of chemical stuff washing around. Radiation though?

1 Bq is 1 decay per second. I wouldn't be surprised to see 1 Bq/kg in natural sources - we have radon in basements on the east coast. There are 10^26 atoms in a typical kg of material. 1 Bq is nothing. Your body has 4kBq going on in it all the time.

 

[swimmer]

So you're going to take a bunch of half-starved, injured, freezing refugees and tell them not to drink the water because there is a remote possibility that they might get cancer someday if the levels of radioactives detected were 300 times what they are? This is the kind of insanity about radiation that is going to get more people hurt than the disaster ever will.

There might be other good reasons not to drink the water (quite a lot of things broke during the quake and the tsunami - there's probably all sorts of chemical stuff washing around. Radiation though?

1 Bq is 1 decay per second. I wouldn't be surprised to see 1 Bq/kg in natural sources - we have radon in basements on the east coast. There are 10^26 atoms in a typical kg of material. 1 Bq is nothing. Your body has 4kBq going on in it all the time.

Regarding tap water and I-131, this is the equation that works for me:

Reading up on science + common sense + friends in Tokyo & Japan + given a choice = avoid tap water.

 

[Maxion]

Regarding tap water and I-131, this is the equation that works for me:

Reading up on science + common sense + friends in Tokyo & Japan + given a choice = avoid tap water.

I would ask for a refund of my education and common sense if that is your opinion. I-131 is absorbed by the thyroid, if there are large levels of I-131 running around the common thing to do is to fill your thyroid with non-radioactive iodine which prohibits the uptake of radioactive iodine. Besides I-131 has a half-life of roughly 8 days so it is quite quickly gone.

Irrational fear of radiation is something that will really hurt our civilization.

 

[TCups]

DEBUNK THE UNIT 3 BLAST SCENARIO PLEASE

Since the blast was not likely below the spent fuel pool (pool structure would mitigate the blast force), the spent fuel elements due to their weight would not be ejected from the racks which are a tight fix due to seismic considerations.

OK, understand, but I am not sure that the blast force can be mitigated as easily.

Looking for those more learned than me to debunk this hypothesis of the blast mechanism at Unit 3, which I have put together from what I have gleaned at this website.

SCHEMATIC:

(1) An overheating reactor core results in damaged fuel rods, oxidization, and reaction of steam + zirconium accumulating in the reactor containment vessel. Due to increased pressure and heat in the reactor vessel, hydrogen gas is vented into the primary containment vessel, but that increased pressure eventually compromises the seals at the drywell head.

see: http://allthingsnuclear.org/post/3940804083/possible-cause-of-reactor-building-explosions

(2) Hydrogen gas under pressure can now leak into the refueling cavity, and perhaps into the upper building structure either around the concrete shield plug or the gate between the refueling cavity and the spent fuel pool.

(3) The seals on the gate to the spent fuel pool are pneumatic and pressure in the seals is maintained by electric pump. If the electricity fails, the seals could fail allowing both water from the SFP to leak into the refueling cavity, and H2 gas to leak out.

see: http://allthingsnuclear.org/post/3964225685/possible-source-of-leaks-at-spent-fuel-pools-at

(4) An explosion arising from the pressurized hydrogen + steam within the primary containment, but leaking into the upper building, might find the path of least resistance as a blow-out through the gate with damaged seals and chute, and finally, into the SFP. The SPF, would tend to direct a large portion of the blast from the containment upward, and could potentially scatter high level radioactive debris -- if not all of the fuel rods, then perhaps fragments of the damaged fuel rods, many of which may be visible within the damaged upper portion of unit 3, in the area of the blast near the SFP, as seen on the helicopter fly by. Additional hydrogen gas accumulated in the upper building structure would also explode, blowing out the walls of the upper building -- a 1-2 punch. Steam from the primary reactor containment could now vent through the blast defect in the transfer chute.

see:
http://1.bp.blogspot.com/-5gGV59tdlt0/TX2J7O4F1rI/AAAAAAAABkM/FIfqa-RMJNQ/s400/reactor3.JPG

 

[Maxion]

(2) Hydrogen gas under pressure can now leak into the refueling cavity, and perhaps into the upper building structure either around the concrete shield plug or the gate between the refueling cavity and the spent fuel pool.

(3) The seals on the gate to the spent fuel pool are pneumatic and pressure in the seals is maintained by electric pump. If the electricity fails, the seals could fail allowing both water from the SFP to leak into the refueling cavity, and H2 gas to leak out.

see: http://allthingsnuclear.org/post/3964225685/possible-source-of-leaks-at-spent-fuel-pools-at

(4) An explosion arising from the pressurized hydrogen + steam within the primary containment, but leaking into the upper building, might find the path of least resistance as a blow-out through the gate with damaged seals and chute, and finally, into the SFP. The SPF, would tend to direct a large portion of the blast from the containment upward, and could potentially scatter high level radioactive debris -- if not all of the fuel rods, then perhaps fragments of the damaged fuel rods, many of which may be visible in the area of the blast in Unit 3 as seen on the helicopter fly by. Additional hydrogen gas accumulated in the upper building structure would also explode, blowing out the walls of the upper building -- a 1-2 punch. Steam from the primary reactor containment could now vent through the blast defect in the transfer chute.

see:
http://1.bp.blogspot.com/-5gGV59tdlt0/TX2J7O4F1rI/AAAAAAAABkM/FIfqa-RMJNQ/s400/reactor3.JPG

IANANE (I am not a nuclear engineer) but isn't the SFP, canal and drywell head submerged under water constantly?

If that is the casen for the hydrogen to explode it would first have to seep through the concrete plug and into the containment building. Then it would rise to the roof and the highest concentration of hydrogen would be at roof level, not floor.

Here's a cross section of a BWR MK 1 design (I think?) posted earlier. ( http://media.tumblr.com/tumblr_li9czl6f4v1qbnrqd.jpg )

 

[TCups]

IANANE (I am not a nuclear engineer) but isn't the SFP, canal and drywell head submerged under water constantly?

Unless a portion of the water is boiled off or leaks off or both. The transfer chute is not as deep as the entire well, though.

If that is the casen for the hydrogen to explode it would first have to seep through the concrete plug and into the containment building. Then it would rise to the roof and the highest concentration of hydrogen would be at roof level, not floor.

Unless, of course, the explosion ORIGINATED in the primary containment, where the pressurized hydrogen gas and most of the really hot stuff that might cause an explosion are most likely to be. The unpressurized hydrogen gas that had leaked into the upper building ignited as a secondary explosion after the high-pressure explosion below.

Here's a cross section of a BWR MK 1 design (I think?) posted earlier. ( http://media.tumblr.com/tumblr_li9czl6f4v1qbnrqd.jpg )

I will study it and comment if appropriate. I hope IANANE means "I am not a network engineer" and wasn't intended to be INNANE. I am not a network engineer, either.

Addendum: sorry, I initially posted the wrong pic under "SCHEMATIC" -- I apparently made that correction while you were typing. I have annotated the same diagram you supplied.

Give me your best shot. I am just struggling to figure this out and can use any feedback or alternative hypothesis.

 

[AntonL]

What sort of blast might scatter spent fuel rods out of a SFP? One venting through the channel between the SFP and the reactor containment?

I have been toying with this problem for some time. I tried to imagine the explosion dynamics at the explosion centre and the SPF being at the explosion centre. I put my ideas here for test and discussion.

Idea 1:
a. Let's assume a hydrogen explosion, H2 and O2 combine generate enormous heat and water, the blast shock wave spreads out accelerating the atmosphere away from the explosion centre, thus leaving a vacuum
b. The explosion is immediately followed by an implosion at the explosion centre.
c. Now assume a boiling SFP, and if the vacuum does exist the water in the SFP will momentary super-boil as during the low pressure phase of the explosion huge amounts of steam generate where it is hottest, right by the fuel, ejecting or propelling water fuel rods into the air.

Idea 2:
Assume water is boiling in SFP. Its volume is a combination of liquid volume and steam volume. The steam bubbles in the water allow the water to be compressed like a sponge and the explosion will compress the water, a shock wave is established in the pool and the re-condensing of the steam in suspension due to the higher pressure causing the water to collapse. This shock wave soon will have the opposite effect and a decompression will take place which will stretch or lower the pressure of the water and water will again expand as the steam bubbles are produced. Once the water is accelerated vertically this movement is sustained by the water being immediately replaced by steam. Again super-boiling could take place causing the ejection as in c above.

Idea 3: combination of 1 and 2

Above might describe what TCups calls "what sort of blast"

I do not know if this was discussed earlier, Look at the video of the explosion of reactor 1
http://www.youtube.com/watch?v=TZ6lurStTvU&feature=related"
The very first frames 0 to 2 seconds of the video and repeated later at 40 to 42 seconds. At the beginning of explosion a vertical column of I do not know what is rising at great speed and then quickly disappearing into nothing. Can someone please explain this vertical column that then disappears. What makes it even more intriguing from satellite pictures it seems that the roof of reactor 1 has collapsed as one piece as no visible roof or building structure is visible. Now if you continue watching the video you will note something black/dark lifting in the explosion cloud and then falling back to ground. If that something dark is the roof and then lands right back from where it came from I conclude that it got sucked back lending weight to idea 1 above.

 

[TCups]

I have been toying with this problem for some time. I tried to imagine the explosion dynamics at the explosion centre and the SPF being at the explosion centre. I put my ideas here for test and discussion.

Above might describe what TCups calls "what sort of blast"

I do not know if this was discussed earlier, Look at the video of the explosion of reactor 1
http://www.youtube.com/watch?v=TZ6lurStTvU&feature=related"
The very first frames 0 to 2 seconds of the video and repeated later at 40 to 42 seconds. At the beginning of explosion a vertical column of I do not know what is rising at great speed and then quickly disappearing into nothing. Can someone please explain this vertical column that then disappears. What makes it even more intriguing from satellite pictures it seems that the roof of reactor 1 has collapsed as one piece as no visible roof or building structure is visible. Now if you continue watching the video you will note something black/dark lifting in the explosion cloud and then falling back to ground. If that something dark is the roof and then lands right back from where it came from I conclude that it got sucked back lending weight to idea 1 above.

The 0-2 sec is a shock wave, perhaps a reflected shock wave, traveling upward, ahead of the debris and smoke. The force of the actual explosion at unit one blasts most of the building outward, consistent with origin of the explosion from within the top floor. There isn't much in the way of concrete and dust to blast skyward in that scenario.

 

[TCups]

UNIT 3 EXPLOSION

Video here:


Unlike the explosion at Unit 1, the Unit 3 explosion starts with a fireball blasting upward and to the right -- not with the whole top floor of the building blowing outward.

. . . which fits with my proposed mechanism.

 

[jensjakob]

TCups - I think that we together are hitting bulls eye.

 

[TCups]

TCups - I think that we together are hitting bulls eye.

Well, there does definitely seem to be some part of the bull involved -- not yet sure whether it is the eye or not. But until someone proves me wrong, my working hypotheis is that it was hydrogen in the reactor containment that exploded first, probably venting upward and outward through the transfer chute then the SFP. And I believe there will be many bits of very nasty stuff blasted out as a consequence.

 

[Maxion]

Well, there does definitely seem to be some part of the bull involved -- not yet sure whether it is the eye or not. But until someone proves me wrong, my working hypotheis is that it was hydrogen in the reactor containment that exploded first, probably venting upward and outward through the transfer chute then the SFP. And I believe there will be many bits of very nasty stuff blasted out as a consequence.

Going back to my limited knowledge of BWR reactors, the primary containment is supposed to be filled with an internt gas and therefor hydrogen in the primary containment shouldn't be able to explode.

IMO if the explosion didn't occur in the containment building then it occurred in the refueling cavity if it wasn't under water.

 

[AntonL]

DEBUNK THE UNIT 3 BLAST SCENARIO PLEASESCHEMATIC:

(2) Hydrogen gas under pressure can now leak into the refueling cavity, and perhaps into the upper building structure either around the concrete shield plug or the gate between the refueling cavity and the spent fuel pool.

I would imagine that the concrete plugs are not airtight nor is it circular as we would imagine a plug to be. Concrete has a specific gravity of 2.5 I would imagine the plug to be an array of concrete beams sized to be of manageable weight for the overhead crane to handle. They would be impossible to be made air tight. They just provide a floor and possibly radiation shielding. Primary containment ends with the steel dome labelled Steel Containment Vessel

[PLAIN]http://nei.cachefly.net/static/images/BWR_illustration.jpg

 

[curious11]

Fascinating analysis and discussions on here.
The containment explosion hypothesis seems a likely explanation for the multiple explosions heard during the reactor 3 event. ie pop 1 being the pressure vessel, pop2 being the primary containment, and then pop 3 being the unpressurised hydrogen in the roof void. Although I would not have expected such large durations between each pop, and there are no visible signs of 3 independent explosions.

To add another area of curiousity, has anyone considered what the grey area that appears to have emanated from reactor 3?

http://patrick.reformstudios.com/p.jpg

 

[TCups]

I would imagine that the concrete plugs are not airtight nor is it circular as we would imagine a plug to be. Concrete has a specific gravity of 2.5 I would imagine the plug to be an array of concrete beams sized to be of manageable weight for the overhead crane to handle.

[PLAIN]http://nei.cachefly.net/static/images/BWR_illustration.jpg[/QUOTE]

Yes, in one of the pictures, the plug looks octagonal. So perhaps a portion of the plug blew out.

[PLAIN]http://i306.photobucket.com/albums/nn270/tcups/5596b43d.jpg

Still, the primary explosion is extremely powerful, and it is upward and to the right, consistent with the visible damage in the close ups. Hydrogen is lighter than any other inert gas and would rise to the top. The seal of the transfer chute (and therefore the primary containment) may have leaked. And did I read that the oxidation reaction with zirconium and steam produced hydrogen and oxygen? Someone correct me if I am wrong please.

 

[Maxion]

Y
The seal of the transfer chute (and therefore the primary containment) may have leaked. And did I read that the oxidation reaction with zirconium and steam produced hydrogen and oxygen? Someone correct me if I am wrong please.

No, the seal of the primary containment is the cap of the steel containment vessel. There should be no pressure proof anything above that. I'm not sure where you're getting this seal of the transfer chute from, that seal is most likely no more secure than the concrete plug.

 

[jensjakob]

@TCups:
Hints at Drywell Head leaks:
http://www.nrc.gov/reading-rm/doc-collections/gen-comm/bulletins/1978/bl78009.html

 

[jensjakob]

Quote: "Results indicate failure of the drywell head seals due to the extremely hot atmospheric conditions extant in the drywell"

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V4D-4810V35-3B&_user=10&_coverDate=08%2F31%2F1990&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_searchStrId=1686158130&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=65af6e45103124c71a4ec4249f9e5577&searchtype=a