Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[NUCENG]

I've been looking for the photo evidence of a second explosion at unit 3 and haven't found anything conclusive, yet. But I have some other information that tends to bring more doubt of a big hydrogen explosion in the Unit 4 SFP.

Some here have expressed a lot of doubt about TEPCO's information. Since I am using their data, not everyone will agree.

They have described damage to fuel in the Unit 4 SFP as minor. Their samples indicated concentrations of I-131 at 220 Bq/cm^3 and Cs-137 at 93 Bq/cm^3. I took the conservative assumprion that the core just offloaded was the only contributor yo that radioactivity. assumed only a release of 5% for gap release. In a volume of the size of the SFP absent any dilution, but accounting for 30 days of decay would produce activities for CS and I in the range of 1E6 Bq/cm^3. You would have to feed and bleed for a full turnover of SFP volume 16 or 17 times to reach the measured concentrations. If their sample is correct, fuel damage was minor as they claim.

 

[TCups]

I've been looking for the photo evidence of a second explosion at unit 3 and haven't found anything conclusive, yet. But I have some other information that tends to bring more doubt of a big hydrogen explosion in the Unit 4 SFP.

Some here have expressed a lot of doubt about TEPCO's information. Since I am using their data, not everyone will agree.

They have described damage to fuel in the Unit 4 SFP as minor. Their samples indicated concentrations of I-131 at 220 Bq/cm^3 and Cs-137 at 93 Bq/cm^3. I took the conservative assumprion that the core just offloaded was the only contributor yo that radioactivity. assumed only a release of 5% for gap release. In a volume of the size of the SFP absent any dilution, but accounting for 30 days of decay would produce activities for CS and I in the range of 1E6 Bq/cm^3. You would have to feed and bleed for a full turnover of SFP volume 16 or 17 times to reach the measured concentrations. If their sample is correct, fuel damage was minor as they claim.

Yes, but doesn't TEPCO also report the damage at Bldg 4 as a "hydrogen explosion"?

 

[MadderDoc]

Well whaddya know . . .
Nullpunkt may be right. The damage to the northeast corner of Bldg 4 does look like an impact from something that fell on it. That would explain the north wall collapsing inward, except . . . what fell on it? <..>

Isn't the simple answer: Parts of the roof.

There must have been an explosion inside the building, including in the upper floor, everyone would agree. Both the walls, and the roof must have been affected by that explosion. The wall pillars and panels must have been pushed outward by it, the roof however must have been blown upwards.

So, in the moment after the explosion we have had a weakened pillar and wallpanels structure still standing below, and -- 100s of tons of roof in the air some distance above it.

What goes up must come down, so the roof did, and some of it incidentally on top of the north wall. And since the wall had already been buckled outward by the explosion, the next powerful hit from above could leave it only even more collapsed, and even further pushed outward.

 

[NUCENG]

Yes, but doesn't TEPCO also report the damage at Bldg 4 as a "hydrogen explosion"?

Yes, in their initial reports they called it hydrogen.


Here was their first release:

Press Release (Mar 15,2011)
Damage to the Unit 4 Nuclear Reactor Building at Fukushima Dai-ichi Nuclear Power Station


At approximately 6:00am, a loud explosion was heard from within the
power station. Afterwards, it was confirmed that the 4th floor rooftop
area of the Unit 4 Nuclear Reactor Building had sustained damage.

World Nuclear News :

17MARCH
The explosion at unit 4 is thought to have been from a build-up of hydrogen in the area near the used nuclear fuel pond. It severely damaged the building, as well as that of adjacent unit 3, with which it shares a central control room.

So they were saying that there was some simultaneous damage to both Unit 3 and Unit 4.

But now the damage to fuel in the SFP on Unit 4 does not seem to support that scenario.

It keeps bringing me back to a second explosion in Unit 3.

I can't prove it, but I haven't seen anything that fits better.

 

[elektrownik]

What about this strange idea ?
[PLAIN]http://img864.imageshack.us/img864/770/7d39a2e665024e3f8856f31.jpg

 

[TCups]

RE: MECHANISM OF DAMAGE TO BLDG 4 (AND PROBABLY BLDG 3 ALSO)

Nullpunkt has it right. A careful look at the reasonably intact roof of Bldg 1 and the girder structure of Bldg 4 shows that the roof is in "patchwork" square segments that vary slightly in their shades of gray. The same patchwork is present on the north surface of the portion of the roof that fell into Bldg 4. Looking carefully, I believe an explosion (perhaps steam?) over the SFP 4 could have neatly peeled the roof off the building like the lid off a sardine can. Once the south end of the roof was lifted sufficiently high, the north end slid into the top of the building like a giant knife. It looks like a large slab of the roof was involved. A small portion of the roof has also impacted over the southeast corner of Bldg 4 doing structural damage there as well.

And PS: There is a second green crane or some type of machine inside the service floor of the north end of Bldg 4 clearly seen through the second open panel from the right.

And that said, I think all of the damage at Bldg 3 has to be re-assessed in terms of not the FHM going ballistic (perhaps portions did, perhaps not), but instead, the entire roof itself slicing down in a similar fashion on the north end of Bldg 3 as well.

Good call Nulpunkt!

 

[clancy688]

Um, there's something I just spotted about Unit 4...

Sat-Image of March 16th, Unit 4 is already destroyed but the roof is still covered:

http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichi2_march16_2011_dg.jpg

Sat-Image of March 17th, the cover on Unit 4s roof is gone:

http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichirec_march17_2011_dg.jpg

 

[GJBRKS]

Um, there's something I just spotted about Unit 4...

Sat-Image of March 16th, Unit 4 is already destroyed but the roof is still covered:

http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichi2_march16_2011_dg.jpg

Sat-Image of March 17th, the cover on Unit 4s roof is gone:

http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichirec_march17_2011_dg.jpg

(Very OT , but if you would have seen just this picture 1 year ago without further info ,you would not have believed this could happen...I'm still amazed ...)

 

[bytepirate]

Yes, in their initial reports they called it hydrogen.


Here was their first release:

Press Release (Mar 15,2011)
Damage to the Unit 4 Nuclear Reactor Building at Fukushima Dai-ichi Nuclear Power Station


At approximately 6:00am, a loud explosion was heard from within the
power station. Afterwards, it was confirmed that the 4th floor rooftop
area of the Unit 4 Nuclear Reactor Building had sustained damage.

World Nuclear News :

17MARCH
The explosion at unit 4 is thought to have been from a build-up of hydrogen in the area near the used nuclear fuel pond. It severely damaged the building, as well as that of adjacent unit 3, with which it shares a central control room.

So they were saying that there was some simultaneous damage to both Unit 3 and Unit 4.

But now the damage to fuel in the SFP on Unit 4 does not seem to support that scenario.

It keeps bringing me back to a second explosion in Unit 3.

I can't prove it, but I haven't seen anything that fits better.

something else is very hard to explain:
if the hydrogen was produced by a zircaloy reaction, this means the assemblies must have been exposed to the air. right?
but there was no water added to the pool until 4 days after the explosion.
actually, they put big efforts to spray water on the #3 SFP, before they started with #4.

questions to be answered (find my answers in {}):
- was fuel in #4 exposed? {no}
- if not: could enough hydrogen have been produced (radiation decomposition, steam)? {no}
- if yes: why was the fuel covered after the explosion (why did TEPCO obviously did not worry about exposed fuel, + #4 was [only] INES 3 rated after the explosion [weak evidence though]) {i have posted a thesis on this before, but it is too weird to be true}

if the reason for the destruction of #4 was *not* hydrogen:
- could #4 has been damaged by an explosion in #3? {no}
- as no damage to #4 has been observed: was there a second explosion in #3? {no}
- if yes, what kind of explosion in #3 could have an impact on #4 as observed (must have been very directed, no damage to #2...)? {no}
- what else could have exploded in #4? {nothing}

if all my answers are correct, unit 4 has not exploded at all...

 

[clancy688]

if all my answers are correct, unit 4 has not exploded at all...

In conclusion, since 200 pages we have only found evidence / clues why Unit 4 couldn't have exploded, and not a single one to support a big explosion.
And yet, Unit 4 is totally in ruins. It's truly a mystery... ^^;

 

[TCups]

(Very OT , but if you would have seen just this picture 1 year ago without further info ,you would not have believed this could happen...I'm still amazed ...)

Odd lighting, for sure, and really poor resolution, but I believe the damage was already done. The photos are at different angles (about 45 deg vs 90 deg overhead), but I believe I can see the larger pieces of debris on the roof (small arrows), the X structure of the roof girders (rectangle), the inward bowing of the north wall, and the odd angle at the northeast corner (long arrow), even so.

 

[Jorge Stolfi]

Isn't the simple answer: Parts of the roof..

Checking some pics:

http://cryptome.org/eyeball/daiichi-npp/pict10.jpg
http://cryptome.org/eyeball/daiichi-npp/pict12.jpg
http://cryptome.org/eyeball/daiichi-npp/pict13.jpg
http://cryptome.org/eyeball/daiichi-npp/pict46.jpg

Your explanation seems to be the only viable one if there was no late explosion in #3. However, I understand that the roof truss of #4 (still largely intact) was covered with narrow sheet metal strips (plenty of them around, some of them still in place) and then with a layer of tar/concrete. Your theory seems to require a continuous layer of thick sheet metal (or something that looks very much like it), covering at least a large fraction of the roof. There seems to be no such layer in unit #3 or its debris.

The object in question seems quite heavy and hard, since it bent several thick steel beams without itself shattering or crumpling. Would a concrete sheet behave that way? It also seems to have a couple of shallow grooves or ridges parallel to its topmost edge.

It could be an exploded boiler or tank from the lower level of #3, perhaps? Or a piece of #3's drywell dome?

On the other hand, I can believe that such a large piece of debris, falling sideways onto the roof truss, could have pulled the steel beams down, and they in turn could have pulled the concrete beam inwards.

 

[Jorge Stolfi]

Sat-Image of March 16th, Unit 4 is already destroyed but the roof is still covered:
http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichi2_march16_2011_dg.jpg

I think that the roof is already gone in this picture, but the roof's metal skeleton looks like a continuous cover because of the low elevation of the camera and low image resolution,

EDIT: ON second look, I am not so sure. It does seem that the roof tarmac is still there, but the mysterious "metal sheet" is already stuck into it.

EDIT2: On third look, it may be an illusion allright. In http://cryptome.org/eyeball/daiichi-npp/pict10.jpg" , taken with the same camera angle, the truss beams are closely spaced and cover the roof completely. With low resolution it would seem a continuous roof.

 

[TCups]

Checking some pics:

http://cryptome.org/eyeball/daiichi-npp/pict10.jpg
http://cryptome.org/eyeball/daiichi-npp/pict12.jpg
http://cryptome.org/eyeball/daiichi-npp/pict13.jpg
http://cryptome.org/eyeball/daiichi-npp/pict46.jpg

Your explanation seems to be the only viable one if there was no late explosion in #3. However, I understand that the roof truss of #4 (still largely intact) was covered with narrow sheet metal strips (plenty of them around, some of them still in place) and then with a layer of tar/concrete. Your theory seems to require a continuous layer of thick sheet metal (or something that looks very much like it), covering at least a large fraction of the roof. There seems to be no such layer in unit #3 or its debris.

The object in question seems quite heavy and hard, since it bent several thick steel beams without itself shattering or crumpling. Would a concrete sheet behave that way? It also seems to have a couple of shallow grooves or ridges parallel to its topmost edge.

It could be an exploded boiler or tank from the lower level of #3, perhaps? Or a piece of #3's drywell dome?

On the other hand, I can believe that such a large piece of debris, falling sideways onto the roof truss, could have pulled the steel beams down, and they in turn could have pulled the concrete beam inwards.

The object is heavy -- yes, hard -- no. Isn't the flat roofing structure of most commercial roofs is something like corrugated metal with a thick layer of tar and pea gravel sprayed onto the metal substrate to form a heavy, watertight roof slab? Someone here must know commercial roofing, but I am betting the roof was fairly flexible, but heavy. And if the mass of the whole roof were lifted, peeled upwards largely intact and put in motion by a pressure wave from the explosion and then gravity, then that slab of roofing would have plenty enough mass and kinetic energy to do some serious damage IMO.

 

[cphoenix]

something else is very hard to explain:

("If it was hydrogen" edited out by cphoenix)

if the reason for the destruction of #4 was *not* hydrogen:
- could #4 has been damaged by an explosion in #3? {no}
- as no damage to #4 has been observed: was there a second explosion in #3? {no}
- if yes, what kind of explosion in #3 could have an impact on #4 as observed (must have been very directed, no damage to #2...)? {no}
- what else could have exploded in #4? {nothing}

if all my answers are correct, unit 4 has not exploded at all...

I've already explained how something could have exploded in #4. The water in the spent fuel pool could have had up to 1/10 kiloton of explosive force, simply from being superheated under 2 atm of pressure - the pressure under 40 feet of water. 1E10 grams in the pool, 4 J/g/C, 25 C over 1-atm boiling point... once you do the math, it's clear that if even a small fraction of the pool's volume were unable to cool by convection, the resulting burp of steam could easily take out the building.

BTW, my alias is looking more cryptic to me all the time, and that wasn't my intention. I'm Chris Phoenix, and my email is my alias at gmail.com. Nice to meet you all.

 

[GJBRKS]

something else is very hard to explain:
if the hydrogen was produced by a zircaloy reaction, this means the assemblies must have been exposed to the air. right?
but there was no water added to the pool until 4 days after the explosion.
actually, they put big efforts to spray water on the #3 SFP, before they started with #4.

questions to be answered (find my answers in {}):
- was fuel in #4 exposed? {no}
- if not: could enough hydrogen have been produced (radiation decomposition, steam)? {no}
- if yes: why was the fuel covered after the explosion (why did TEPCO obviously did not worry about exposed fuel, + #4 was [only] INES 3 rated after the explosion [weak evidence though]) {i have posted a thesis on this before, but it is too weird to be true}

if the reason for the destruction of #4 was *not* hydrogen:
- could #4 has been damaged by an explosion in #3? {no}
- as no damage to #4 has been observed: was there a second explosion in #3? {no}
- if yes, what kind of explosion in #3 could have an impact on #4 as observed (must have been very directed, no damage to #2...)? {no}
- what else could have exploded in #4? {nothing}

if all my answers are correct, unit 4 has not exploded at all...

Cryptome.org has an assesment from the NRC where they say the fuel in the #4 SFP might have been partially uncovered , producing hydrogen :

http://cryptome.org/0003/daiichi-assess.pdf

 

[|Fred]

OK, but I meant what do you think about something having fallen into the northeast corner of the roof of Building 4?

I know I hadn't formulated answers to your question yet.
I like to speculate when I have some form of intimate conviction, and right now I do not and I'm not sure I clearly grasp the things that I'm seeing.

There is a second green crane or some type of machine inside the service floor of the north end of Bldg 4 clearly seen through the second open panel from the right.

I though I made this point 18 days ago and a fact two days ago :p

Once the south end of the roof was lifted sufficiently high, the north end slid into the top of the building like a giant knife.

Could you please clarify this , I don't picture it right

Odd lighting, for sure, and really poor resolution, but I believe the damage was already done. ...

agreed

simply from being superheated

how do you suggest this happens?, why wouldn't the watter just boil

 

[MiceAndMen]

Here are two more Oyster Creek drawings. One PDF shows a schematic depiction of drywall penetrations and the other shows the PCV. The second one is not too clear, but it's informative nevertheless.

View attachment Oyster Creek Dwg DW Pen.pdf
View attachment Oyster Creek Dwg PCV.pdf

I also attached a PNG that shows the general layout of the refueling level of the Susquehanna I reactor in Pennsylvania USA. There are 2 reactors at Susquehanna and they are located in the same building, mirror images of each other. They share a common cask storage pit that lies between their individual SFPs. They are BWR Mark II designs.

The interesting thing about the Susquehanna reactors is their refueling openings above the drywells are octagonal in shape instead of round. There are pictures around that show openings like this, such as this one at the nuclear tourist website:

http://www.nucleartourist.com/images/rflg-fl1.jpg

Have we seen definite information that says whether the refueling cavity openings at the Fukushima Dai-ichi reactors are round or octagonal (or some other shape)?

 

[MadderDoc]

The vertical position of the fuel handling machine of unit 4 appears to me to be about right, judged from the apparent spatial relationship between the hockey stick, the overhead crane, its rails, and the concrete pillars (taking into account that the hockey stick has been distally somewhat bent, see attachment)

 

[Jorge Stolfi]

The vertical position of the fuel handling machine of unit 4 appears to me to be about right, judged from the apparent spatial relationship between the hockey stick, the overhead crane, its rails, and the concrete pillars (taking into account that the hockey stick has been distally somewhat bent, see attachment)

Indeed. By the way, the "hockey stick" is not bent. Look closer.

However this seems to be the other end of the machine, which has a taller structure rising above the hockey sticks.

 

[bytepirate]

I've already explained how something could have exploded in #4. The water in the spent fuel pool could have had up to 1/10 kiloton of explosive force, simply from being superheated under 2 atm of pressure - the pressure under 40 feet of water. 1E10 grams in the pool, 4 J/g/C, 25 C over 1-atm boiling point... once you do the math, it's clear that if even a small fraction of the pool's volume were unable to cool by convection, the resulting burp of steam could easily take out the building.

BTW, my alias is looking more cryptic to me all the time, and that wasn't my intention. I'm Chris Phoenix, and my email is my alias at gmail.com. Nice to meet you all.

might be an explanation.
but:
- just a gut feeling: i wonder if convection is neglectible (2 bar pressure, 120°C at the bottom - geysers usually have much higher values.)
-would there be water left in the pool after the explosion?
-could a geyser-like event be responsible for the observerd damage (especially the massive damage *below* the top of the pool, actually quite far away from the pool)

anyway, i will put this in my list of possible reasons. a very small list...

 

[|Fred]

the lower part of the crane is (should be) about 2.5 m above the floor , it is not at present. The lower part or the crane is may be 70 cm above the floor.
I suspect the hockey stick to be slightly bent


edit: no I was using the crane from reactor 3 for reference and not the one on unit 4, I believe you are about right, the fhm crane is probably about where it should and no more than 1 m bellow where it should be

 

[bytepirate]

Cryptome.org has an assesment from the NRC where they say the fuel in the #4 SFP might have been partially uncovered , producing hydrogen :

http://cryptome.org/0003/daiichi-assess.pdf

it looks, as if they do basically the same as we do: speculation based on sparse information...

 

[TCups]

@Fred

I thought I made this point (about a third crane) 18 days ago and a fact two days ago :p

You did indeed, verbally as I recall. If you referenced the picture showing the third crane, I missed it. But 18 days ago, I hadn't seen the FHM or part of it still in the SFP3, and 2 days ago, I did see the FHM, or part of it still in the SFP3. Today, I finally did see inside Bldg 4 and visibly verified the presence third crane. I am a visual sort of person. But no matter. That issue is settled in my mind for now.

Could you please clarify this , I don't picture it right

I will try to draw you a picture or maybe even an animation, but it will have to be later. The roof was likely a big slab of asphalt or asphalt like material - a thick, somewhat flexible slab. Imagine it lifting up first over the southeast corner of SFP4, then, still attached at the north end, peeling back from south to north and billowing upward like a sail catching the wind, then, the weight of the large slab collapsing the north wall inward, and finally the south end collapsing vertically on top of the north end of the slab.

 

[|Fred]

I had made a nice picture for you

Considering the states of the unit 3, I 'm just suggesting it as I can not really prove it, apart from an analogy to unit 4 who feature 3 cranes [PLAIN]http://k.min.us/ikzpLE.jpg.
I'm not nulling out that the FHM from the SFP was partialy moved to the north either.

 

[jmelson]

Um, there's something I just spotted about Unit 4...

Sat-Image of March 16th, Unit 4 is already destroyed but the roof is still covered:

http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichi2_march16_2011_dg.jpg

Sat-Image of March 17th, the cover on Unit 4s roof is gone:

http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichirec_march17_2011_dg.jpg

Very different view and different sun angle. I'm not sure you can conclusively state there is a difference. Yes, I agree, it APPEARS different, but it could be a trick of the illumination and view.

Jon

 

[jmelson]

I've already explained how something could have exploded in #4. The water in the spent fuel pool could have had up to 1/10 kiloton of explosive force, simply from being superheated under 2 atm of pressure - the pressure under 40 feet of water. 1E10 grams in the pool, 4 J/g/C, 25 C over 1-atm boiling point... once you do the math, it's clear that if even a small fraction of the pool's volume were unable to cool by convection, the resulting burp of steam could easily take out the building.

BTW, my alias is looking more cryptic to me all the time, and that wasn't my intention. I'm Chris Phoenix, and my email is my alias at gmail.com. Nice to meet you all.

40 feet of water has a static head of 17.3 PSI, just over 1 ATM. And, of course, that is only the bottom of the pool, the mid-level would be half that. So, the amount of energy that could be stored there is a lot less than you give numbers for.

Without some mechanism to force the water to remain still and not convect, I just don't see how this can happen. A very messy boiling mess is quite possible when the active cooling fails, but great superheating and then explosive vaporisation just defies logic. But, maybe with superpure water, it is possible. Not sure how pure the water was after the earthquake.

Jon

 

[jmelson]

might be an explanation.
but:
- just a gut feeling: i wonder if convection is neglectible (2 bar pressure, 120°C at the bottom - geysers usually have much higher values.)
-would there be water left in the pool after the explosion?
-could a geyser-like event be responsible for the observerd damage (especially the massive damage *below* the top of the pool, actually quite far away from the pool)

anyway, i will put this in my list of possible reasons. a very small list...

If the SFP did flash to steam, it would likely have been an unmistakable event, with a HUGE steam cloud, and water splashed over the entire facility. Anyone outside would have had horrible scalding, and probably anyone in the building at the time, also. The water everywhere would have taken a couple hours to evaporate. So, I think a massive flashing of tons of water to steam would have been clearly different from what we did see, and therefore that isn't what happened.

Also, this would have removed a bunch of the water in the pool, although maybe not completely emptied it, if this stratification theory is possible (I don't believe it is). So, then there WOULD have been major damage to the fuel in the pool, which they say is not so.

Jon

 

[Jorge Stolfi]

Without some mechanism to force the water to remain still and not convect, I just don't see how this can happen.

After re-racking, the fuel assemblies are packed tight against each other into crates (each containing perhaps 7x7 assembles), and these are packed tight too. That is essentially a 4m thick fairly solid slab of metal, weighting several thousand tons. Water circulation is still possible through the fuel assemblies, in the space between the rods. There is some space below the layer of assemblies and along the walls of the pools.

I do not know whether convection through such long and narrow channels would be effective without external circulation pumps; http://www.irss-usa.org/pages/documents/11_1Alvarez.pdf" seems to address this question but its estimates seem rather crude,

Does someone know the disposition of cooling water pipes in the SPF? I recall a SFP model shown on NHK which showed two round pipes. One entered near the top of the wall, horizontally, made a 90 turn and continued down for a short distance. The other pipe entered vertically through the bottom, near the wall; went all the way up, then made an U-turn and went back almost to the bottom, siphon-like. I couldn't figure out which was in and which was out.

if that SPF model was correct, then perhaps the earthquake (which included strong and lasting horizontal shaking) shook loose the entire pack of fuel assemblies, which snapped the second pipe and perhaps created a leak through the pool's bottom. It may also have bent the supports that kept the fuel away from the bottom, causing it to settle and thus cutting off convection.

 

[MadderDoc]

Indeed. By the way, the "hockey stick" is not bent. Look closer.

However this seems to be the other end of the machine, which has a taller structure rising above the hockey sticks.

It is actually the same hockey stick, just seen from the opposite (reactor) side, see attachments. I've looked and looked, it still looks bent to me. But perhaps it's the perspectives fooling me.

 

[gmax137]

...

I do not know whether convection through such long and narrow channels would be effective without external circulation pumps; http://www.irss-usa.org/pages/documents/11_1Alvarez.pdf" seems to address this question but its estimates seem rather crude,...

Yes, natural circulation through the assemblies is sufficient to remove the decay heat. I have seen such calculations for PWR fuel and I'm pretty certain that it is true for BWR fuel as well. In fact, in the typical design, the SFP cooling system removes heat from the bulk fluid while the assemblies are cooled by natural circulation (in other words, the cooling loop flow is not 'pumped' through the assemblies at all).

 

[MadderDoc]

<..> 2 days ago, I did see the FHM, or part of it still in the SFP3.

Did you? Perhaps I have been missing something. I am not saying they are not there, just haven't seen any photos of FHM parts in the SFP3. In fact I haven't seen any photos looking into the SFP3.

 

[MiceAndMen]

Oyster Creek Blueprints

Upon further review there are direct-download links for the Oyster Creek blueprint drawings. These 4 PDFs are part of a document titled, "Revision 12 to Updated FSAR for Oyster Creek Nuclear Generating Station". These are publicly available documents hosted on an NRC website. Below each document link I listed a few pages that I found particularly interesting, but there is a lot more information than that contained in these files.

http://adamswebsearch2.nrc.gov/IDMWS/ViewDocByAccession.asp?AccessionNumber=ML011270077" (70 pp)

• 42 Main Stack
• 49 Drywell Cooling

http://adamswebsearch2.nrc.gov/IDMWS/ViewDocByAccession.asp?AccessionNumber=ML011270243" (82 pp)

• 06 Site Plan Showing Intake and Discharge Tunnels
• 31 Containment Spray System
• 35-38 Refueling Floor Plan and Details
• 59 Drywell Penetrations
• 72-74 Drywell Diagrams

http://adamswebsearch2.nrc.gov/IDMWS/ViewDocByAccession.asp?AccessionNumber=ML011270300" (58 pp)

• 04 Symbols and Legend
• 05 Spent Fuel Cask Safe Load Path
• 08-09 Reactor Bldg Floor & Equipment Drains
• 20-28 Reactor Bldg General Arrangement Plan & Elevation

http://adamswebsearch2.nrc.gov/IDMWS/ViewDocByAccession.asp?AccessionNumber=ML011270286" (31 pp)

• 02 Drywell and Torus Vacuum Relief System
• 19-20 Radwaste Cask Safe Load Path

One can access these PDFs and the other parts of the FSAR at the NRC's Web-based ADAMS search page as follows:

1. Go to the main ADAMS site at http://wba.nrc.gov:8080/ves/
2. Select the Advanced Search tab
3. In the search box put "Accession_Number:ML011270* $titleyster" without the quotes
4. Press the Search button and wait

You should get 8 results including the 4 PDF files above.

I've done a lot of searching there over the past few weeks and have been unable to find any other reactor building drawings or blueprints (except for 2 minor PDFs regarding the Susquehanna NPP). If anyone finds any please share them here. Drawings help to visualize the insides of these reactor buildings, even if they are not 100% exactly the same as the Fukushima Daiichi designs.

 

[MadderDoc]

Have we seen definite information that says whether the refueling cavity openings at the Fukushima Dai-ichi reactors are round or octagonal (or some other shape)?

Attached is a photo of Daiichi unit 1 in operation, it is definitely octagonal. I have seen no similar photos from the other units, however, for unit 4, I've seen pictures with the cavity open, and apparent kinks in the railing circle, suggesting a 'not round' shape

 

[MiceAndMen]

Attached is a photo of Daiichi unit 1 in operation, it is definitely octagonal. I have seen no similar photos from the other units, however, for unit 4, I've seen pictures with the cavity open, and apparent kinks in the railing circle, suggesting a 'not round' shape

That photo is part of the "Inside the BWR Power Plant" page at the Nuclear Tourist website http://www.nucleartourist.com/areas/bwr-in1.htm

Under the section "Refueling activities" the last picture link "Refueling floor during operation (120K)" is that same exact photograph. At the top of the page it says,

The following photos and graphics illustrate the equipment representative of the BWR plant. Contributors include CP&L, TVA, General Electric, KKN, Niagara Mohawk, and Detroit Edison.

I'm not sure that photograph really is from the Fukushima Daiichi plant.