Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[clancy688]

Um... very silly question which just plopped into my mind:

There were hydrogen explosions in Units 1 to 3, hydrogen was generated after zircalloy reacted with hot steam. To prevent explosions inside the RPV and to lower the internal pressure, hydrogen was vented. This vented hydrogen exploded then inside the reactor buildings.

The thing I don't geet: Why ended the relieved hydrogen up in the reactor buildings? If I would've to construct an emergency venting system at a nuclear power plant, I would make sure that the vented gas lands outside the buildings and dilutes in the air.
So why did they vent into the building?

The only possible explanation coming to my mind is rupturing of the relieve valves due to high pressure...

 

[michael200]

Clancy688
That's the multibillion dollar question.

 

[elektrownik]

Clancy688
That's the multibillion dollar question.

And I know answer: yes, all bwr reactors after TMI were upgraded with additional venting system but it need power, no one expect that at one time reactor can lost 3 power lines and backup generators... no power no venting

 

[Joe Neubarth]

Um... very silly question which just plopped into my mind:

There were hydrogen explosions in Units 1 to 3, hydrogen was generated after zircalloy reacted with hot steam. To prevent explosions inside the RPV and to lower the internal pressure, hydrogen was vented. This vented hydrogen exploded then inside the reactor buildings.

The thing I don't geet: Why ended the relieved hydrogen up in the reactor buildings? If I would've to construct an emergency venting system at a nuclear power plant, I would make sure that the vented gas lands outside the buildings and dilutes in the air.
So why did they vent into the building?

The only possible explanation coming to my mind is rupturing of the relieve valves due to high pressure...

Last I heard they had an electrical operated shut off valve that failed shut. It needed electricity to open, and there was no electricity. Nobody has explained why that valve was in the system when the worst case scenario would have it that the reactor plant lost electricity. That, of course would result in overheating of the core and the necessary venting. Unfortunately if the valve is shut because of a loss of electricity, YOU ARE ROYALLY SCREWED.

 

[I_P]

Um... very silly question which just plopped into my mind:

There were hydrogen explosions in Units 1 to 3, hydrogen was generated after zircalloy reacted with hot steam. To prevent explosions inside the RPV and to lower the internal pressure, hydrogen was vented. This vented hydrogen exploded then inside the reactor buildings.

The thing I don't get: Why ended the relieved hydrogen up in the reactor buildings? If I would've to construct an emergency venting system at a nuclear power plant, I would make sure that the vented gas lands outside the buildings and dilutes in the air.
So why did they vent into the building?

The only possible explanation coming to my mind is rupturing of the relieve valves due to high pressure...

This has been a point of discussion elsewhere, and perhaps here as well. The consensus in other discussions was that there should not be a design path to vent into the building and what occurred was not intended or expected. Failure of valves, structure, or perhaps the failure of seals due to over-pressure are possibilities for allowing H2 to vent inside the building.

 

[NUCENG]

Um... very silly question which just plopped into my mind:

There were hydrogen explosions in Units 1 to 3, hydrogen was generated after zircalloy reacted with hot steam. To prevent explosions inside the RPV and to lower the internal pressure, hydrogen was vented. This vented hydrogen exploded then inside the reactor buildings.

The thing I don't geet: Why ended the relieved hydrogen up in the reactor buildings? If I would've to construct an emergency venting system at a nuclear power plant, I would make sure that the vented gas lands outside the buildings and dilutes in the air.
So why did they vent into the building?

The only possible explanation coming to my mind is rupturing of the relieve valves due to high pressure...

It has been reported that the plants had installed hardened wetwell vent systems to be used to vent the containment from the suppression pool airspace to the offgas stack outside the building. In the case of uniit one the containment pressure was more than 2 times the design limit before they started to vent. Containment may already have been leaking or the overpressure could have caused leaks in the vent piping inside the building. About 1 hour after completing the venting unit 1 exploded. The system was not designed to vent into the building, but something must have leaked.

 

[ascot317]

Um... very silly question which just plopped into my mind:

There were hydrogen explosions in Units 1 to 3, hydrogen was generated after zircalloy reacted with hot steam. To prevent explosions inside the RPV and to lower the internal pressure, hydrogen was vented. This vented hydrogen exploded then inside the reactor buildings.

The thing I don't geet: Why ended the relieved hydrogen up in the reactor buildings? If I would've to construct an emergency venting system at a nuclear power plant, I would make sure that the vented gas lands outside the buildings and dilutes in the air.
So why did they vent into the building?

The only possible explanation coming to my mind is rupturing of the relieve valves due to high pressure...

Page 117 and following deals with various venting related issues
http://www.galcit.caltech.edu/~jeshep/fukushima/ShepherdFukushima9April2011.pdf

even more interesting to read:
http://www.osti.gov/bridge/servlets/purl/6980202-feK1wp/6980202.pdf

"THE ROLE OF BWR SECONDARY CONTAINMENTS IN SEVERE ACCIDENT MITIGATION:
ISSUES AND INSIGH1S FROM RECENT ANALYSES"

 

[MadderDoc]

This photo I believe was taken on the 11th or the 12th of March 2011:
[PLAIN]http://mw2.google.com/mw-panoramio/photos/medium/49439865.jpg

To state the obvious, this is before unit 4 blew up :-)

However, first question:
what, if not the existence of a hole in the east wall, to the south, low and below the service floor, could explain what we are seeing there?

Second question: The east wall appears to be divided into vertical sections, a broad one in the middle, somewhat narrower sections to the right and left of that, and again, to the right and left of those sections, two even narrower sections towards the ends of the wall. What produces this appearance?

 

[Caniche]

I would like astronuc to awnser that one, but it seems it has more to do with the way you present the numbers.

Most curious . Perhaps someone could offer a plausible explanation for the enormous discrepancies in the emissions figures?

I131 - NISA estimate total emissions to 12/4/2011 = 130,000 TBq
NSC = 150,000 TBq
CTBT network analysis estimate total emission to 15/3/2011 = 400,000 TBq

Likewise for

C137 - NISA = 6100 TBq to 12/4
NSC = 1200 TBq t0 12/4
CTBT = 33,000 TBq to 15/3

Also would I be correct in my assumption that whilst the Japanese statistics for TOTAL emissions would suggest combined airborne/seawater contamination the figures produced by analysis of CTBT data would be limited to airborne emissions?

 

[Sabbatia]

I'm just a CPA that has a strong interest in science and has been lurking here...but I do have a question. How did they vent the units without power? Was there a manual way to do it that was still operational?

 

[Jorge Stolfi]

I would dispute that fig_un1_pools_and_walls.png shows the correct layout of the pools. There has been no confirmation that the smallest pool in the picture actually exists separately from the SFP in any of the reactor buildings.

Indeed. I found a blueprint of the service floor layout, supposedly of units #2--#5, in this page

http://fukushimafaq.wikispaces.com/3D+and+Autocad+Rendering+%26+Analysis

and a fisheye view of #4's service floor:

http://www.houseoffoust.com/fukushima/possibles.html
http://www.houseoffoust.com/fukushima/reactor4_insideplain.jpg

As others have observed, the layout of #2--#5 seems to be very different from that of #1. There is no separate pool for cask loading between the service pools and the elevator, and the N-S arrangement seems reversed, with SFP and elevator near the South wall. Presumably the the function of the cask-loading pool is performed by a small enclosure within the spent-fuel pool (square on the outside, round inside), at its NW corner.

Now if only I had the vertical cross-section blueprints of one of the 2--4 buildings

 

[biffvernon]

This photo I believe was taken on the 11th or the 12th of March 2011:
[PLAIN]http://mw2.google.com/mw-panoramio/photos/medium/49439865.jpg

To state the obvious, this is before unit 4 blew up :-)

However, first question:
what, if not the existence of a hole in the east wall, to the south, low and below the service floor, could explain what we are seeing there?

Second question: The east wall appears to be divided into vertical sections, a broad one in the middle, somewhat narrower sections to the right and left of that, and again, to the right and left of those sections, two even narrower sections towards the ends of the wall. What produces this appearance?

2nd question: those lines were there before March 11th. See: [PLAIN]http://img.ibtimes.com/www/data/images/full/2011/03/15/74732-tokyo-electric-power-co-s-fukushima-daiichi-nuclear-plant-no-4-reactor.jpg

Don't know about 1st question.

 

[Jorge Stolfi]

This photo I believe was taken on the 11th or the 12th of March 2011:
[PLAIN]http://mw2.google.com/mw-panoramio/photos/medium/49439865.jpg
what, if not the existence of a hole in the east wall, to the south, low and below the service floor, could explain what we are seeing there?

Indeed. Curiously the "hole" is not visible in the post-explosion photos; apparently it was covered by debris.

Second question: The east wall appears to be divided into vertical sections, a broad one in the middle, somewhat narrower sections to the right and left of that, and again, to the right and left of those sections, two even narrower sections towards the ends of the wall. What produces this appearance?

Perhaps they are lightning rod conduits, or rainwater drainage pipes. According to the #1 blueprints, the roof is slanted by 30cm in the E-W direction (although in #1 the East is lower). They seem to follow the main concrete pillars of the building, but offset to one side or the other, rather than down the pillar's midline.

 

[triumph61]

This photo I believe was taken on the 11th or the 12th of March 2011:
[PLAIN]http://mw2.google.com/mw-panoramio/photos/medium/49439865.jpg

To state the obvious, this is before unit 4 blew up :-)

However, first question:
what, if not the existence of a hole in the east wall, to the south, low and below the service floor, could explain what we are seeing there?

Second question: The east wall appears to be divided into vertical sections, a broad one in the middle, somewhat narrower sections to the right and left of that, and again, to the right and left of those sections, two even narrower sections towards the ends of the wall. What produces this appearance?

can you give us the Source of the Foto (Original)

 

[Astronuc]

So has there been 150 times as much radioactivity released?

150 times as much as what?

According to the files in this thread - https://www.physicsforums.com/showthread.php?t=493058 - safety authorities are estimating that the release of Cs/I from Fukushima is about an order magnitude less than the release from Chernobyl. Chernobyl was one core, but Fukushima has three damaged cores, or four if one considers the off-loaded fuel from Unit 4.

 

[MadderDoc]

can you give us the Source of the Foto (Original)

My source: http://www.panoramio.com/photo/49439865

[PLAIN]http://mw2.google.com/mw-panoramio/photos/medium/49439865.jpg

 

[NUCENG]

And I know answer: yes, all bwr reactors after TMI were upgraded with additional venting system but it need power, no one expect that at one time reactor can lost 3 power lines and backup generators... no power no venting

At least at Unit 1 they manually operated the hardened vent valve. The worker who performed that task received a significant dose that was reported in TEPCO Press Releases. Since that was well after batteries would have been drained I assume they also vented units 2 and 3 manually.

The WSJ article posted by MSCHARISMA describes the fact that the venting was manual.

 

[clancy688]

Nice, that was probably the right question to ask - so many answers. :)

even more interesting to read:
http://www.osti.gov/bridge/servlets/purl/6980202-feK1wp/6980202.pdf

"THE ROLE OF BWR SECONDARY CONTAINMENTS IN SEVERE ACCIDENT MITIGATION:
ISSUES AND INSIGH1S FROM RECENT ANALYSES"

Indeed, very interesting:

Containment- Venting: Existing BWRs employ primary containuent venting systems
to provide the venting c apabi l i ty necessary for containment ine r t ing prior to
reactor s t a r t up and de - ine r t ing prior to personnel entry i n to the primary
containment. Most exi s t ing plant emergency operating procedures c a ll for
containment venning when containment pressure reaches or exceeds ths design
value (48 to €J psig or 331 to 414 kPa gauge) . 35-37 Failure of the vent system
ducting is l i k e ly under the se circumstances, since the systems were not
designed for such pressure d i f f e r e n t i a l s. Such ducting f a i l u r es would allow
the vented material to discharge directly into the reactor building, flooding
the building with steam and combustible gases, and e f f e c t I've ly eliminating
further access to the secondary containment. Backfitting of dedicated "hard"
vent systems (which employ high-pressure ducting throughout the ent i re system
but no f i l t e r s) has been suggested as one mechanism for improving vent
r e l i a b i l i t y. It should also be noted t h a t, exi s t ing containment venting
systems would not be functional during s t a t i on blackout sequences. Power
(d. c. or a . c. or di r e ct human manipulation) is required for vent valve
operation.

So the longer they waited, the more they increased the possibility of an explosion? Ouch...

But that's only Unit 1. As for Unit 2, the venting was apparently successfull - an explosion only occurred in the wetwell (torus). But what went wrong with Unit 3? Same failure as Unit 1? Does anybody know how high the core pressure was when they vented Unit 3?

Also would I be correct in my assumption that whilst the Japanese statistics for TOTAL emissions would suggest combined airborne/seawater contamination the figures produced by analysis of CTBT data would be limited to airborne emissions?

Nope, it's not total emissions, the japanese statistics are airborne as well:

http://www.nisa.meti.go.jp/english/files/en20110412-4.pdf

[...]Nuclear and Industrial Safety Agency
(NISA) estimated the total amount of discharged radioactive materials
from the reactors of Fukushima Dai-ichi NPS to the air[...]

Outflow to the sea:

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110421e2.pdf

 

[Dmytry]

Um... very silly question which just plopped into my mind:

There were hydrogen explosions in Units 1 to 3, hydrogen was generated after zircalloy reacted with hot steam. To prevent explosions inside the RPV and to lower the internal pressure, hydrogen was vented. This vented hydrogen exploded then inside the reactor buildings.

The thing I don't geet: Why ended the relieved hydrogen up in the reactor buildings? If I would've to construct an emergency venting system at a nuclear power plant, I would make sure that the vented gas lands outside the buildings and dilutes in the air.
So why did they vent into the building?

The only possible explanation coming to my mind is rupturing of the relieve valves due to high pressure...

They vented very late.

 

[triumph61]

My source: http://www.panoramio.com/photo/49439865

[PLAIN]http://mw2.google.com/mw-panoramio/photos/medium/49439865.jpg[/QUOTE]

Thank you.
Sorry.. it´s look like a fake.

 

[|Fred]

Indeed. I found a blueprint of the service floor layout, supposedly of units #2--#5, in this page
and a fisheye view of #4's service floor:

wiki is filled with unreliable data..
I posted the fish eye picture here with source it is not from #4 but from #5 (the one on the extreme north of the plant)
And the service floor BP linked on the webpage was posted here originaly few dozen pages down and is not from Fukushima.

 

[MadderDoc]

Indeed. Curiously the "hole" is not visible in the post-explosion photos; apparently it was covered by debris.

Actually the hole (if that is what we see on this photo from March 12th) is also present in the post-explosion photos, it just appears to have grown larger, to now include the whole of that particular wall panel (the panel at row 3,column 1 of the east wall). See attachments.

Perhaps they are lightning rod conduits, or rainwater drainage pipes. According to the #1 blueprints, the roof is slanted by 30cm in the E-W direction (although in #1 the East is lower). They seem to follow the main concrete pillars of the building, but offset to one side or the other, rather than down the pillar's midline.

By looking at the paint pattern of the still hanging on wall panels (row 1, column 3 and 4), I've been able to determine that the apparent vertical ridges of the center section closely follows pillar 3 and 5 of the wall structure, whereas the outer ridges towards the ends divide the panels at the ends of the wall. The apparent hole appears to include the bottom half of the involved wall panel, from the south end and in, as far north as up to the ridge dividing the panel.

I have looked through the early satelite photos, they all view the east face of the building in a rather sharp angle, however there are none of those photos I would say negate the presence of a hole, if anything they support the notion, that 'there is something there'. See attachment.

 

[|Fred]

150 times as much as what?
.

as much as they posted before , before "converting Bequerel from cesium to Bequerel from iodine equivalent"

 

[elektrownik]

At least at Unit 1 they manually operated the hardened vent valve. The worker who performed that task received a significant dose that was reported in TEPCO Press Releases. Since that was well after batteries would have been drained I assume they also vented units 2 and 3 manually.

The WSJ article posted by MSCHARISMA describes the fact that the venting was manual.

Yes but you can't vent only manualy with holes, maybe they open vent valve but this wouldn't remove much hydrogene, there is another system for that but i t need power to work, you can see it on some pictures of bwr reactors for example in usa, but it is like venting system in normal buildings, it need power to pump off hydrogene from reactor hall...

 

[MadderDoc]

Re the image at http://www.panoramio.com/photo/49439865

Thank you.
Sorry.. it´s look like a fake.

Which indications do you see, that it is a fake?

 

[clancy688]

as much as they posted before , before "converting Bequerel from cesium to Bequerel from iodine equivalent"

Yeah... if I understand correctly, the previous numbers were 0.69 Tbq/h I131 and 0.14 TBq/h C137 (forgive me for mistakes, I'm reciting those numbers from my memory). They just added those two numbers and got 0.83 TBq escaping activity per hour.
That's not wrong... that's the activity you can measure. But if you want to tell people how bad that activity is (for example 1000 TBq Krypton-85 per hour would pose no real threat), you convert it into I131 equivalence.

They didn't do that with those numbers and have done that afterwards - but the number they got the second time wasn't per hour, but per day.

Before conversion:

0.69 TBq/h + 0.14 TBq/h = 0.83 TBq/h
0.83 TBq/h * 24h = 19.92 TBq/d

After conversion:

0.69 TBq/h * 1 + 0.14 TBq/h * 40 = 6.29 TBq/h
6.29 TBq/h * 24h = 150.96 TBq/d

The released activity didn't change at all. They only changed the math. It shows you now, that those 20 TBq of I131 and C137 which are escaping per day are as dangerous as 150 TBq I131.

If the number is stable then that's a radioactivity release on Three Mile Island Scale every four days. And a radioactivity release on Chernobyl scale every 110 years.

 

[triumph61]

Re the image at http://www.panoramio.com/photo/49439865



Which indications do you see, that it is a fake?

The Foto is too small 40kb to see if it is real. It is made before B3 Explosion (no debrid on the Roof) No one says that soneone has made a hole in the Building or an Explosion before B3.
sorry in English ist is difficult to explain.

 

[htf]

At least at Unit 1 they manually operated the hardened vent valve. The worker who performed that task received a significant dose that was reported in TEPCO Press Releases. Since that was well after batteries would have been drained I assume they also vented units 2 and 3 manually.

I am thinking about the security concept. Did I get this right:

- venting of the RPV is possible from a remote location or happens automatically even without power.

- venting of the containment requires electrical power. In case of a station blackout someone has to enter the recator building an manually open a valve?

So the security concept is based on the fact that you find somebody stupid enough to do that? Somebody who knows that he will receive a high dose of radiation and may be torn to pieces by a hydrogen explosion? Guess what I would have done in such a situation...

 

[biffvernon]

No one says that soneone has made a hole in the Building

I guess the building must have a door - even a pretty big door to get equipment in and out. But that 'hole' does seem a long way above ground level and there's no sign of it in the earlier picture:

[PLAIN]http://img.ibtimes.com/www/data/images/full/2011/03/15/74732-tokyo-electric-power-co-s-fukushima-daiichi-nuclear-plant-no-4-reactor.jpg

 

[triumph61]

I guess the building must have a door - even a pretty big door to get equipment in and out.

it is on the other side