Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Yamanote]

Interesting scenes from TEPCO's video related to ocean monitoring of sea life in 20 km

http://photo.tepco.co.jp/en/date/2012/201203-e/120330-01e.html

If you mean that plant, it's neither Daiichi nor Daini.

 

[MadderDoc]

Um, I just asked myself "What's the point anyway?". As far as I understand, they're simply pouring water on the cores. But there's no closed circuit, so they're NOT pumping the water out. Or am I wrong and there IS some kind of return?
Because if there's not and they are stuffing the lower leaks, the water will simply rise up to the next leak. And then flow out again.

I was asking myself similar questions. It makes sense only, if another outlet for the water fed in is provided. The water balance of the plant is not something I've followed closely, but I do remember reading repeatedly, that some of the water taken out from the current outlets are returned to the reactors. Early in the water clean-up operation, I got the impression that the water taken out from the T/B basements were divided: partly to be sent back to the reactors, partly to be processed by Sarry and stuff, as and if capacity was provided. Currently, my impression is that some of the processed water is being returned to the reactors.

-----------------

On a different note: So they are pouring water on top of the damaged/molten fuel. Several tons an hour, since over a year. And all that water's flowing out into the basement, new water enters the containment, flows out, and so on. For over a year. Doesn't that necessarily mean that every single soluble radioactive particle which isn't still protected by a crust of molten fuel is gone, being distributed in the basement?

It would seem that much of it has been distributed. However I think such a material would be subject to significant erosion, which would give way for continued dissolution.
Yikes :-), now you've got me wondering how the contamination of the water in the R/B basements compares to that of the T/B basements and further downhill.

 

[Tepconium-311]

Currently, my impression is that some of the processed water is being returned to the reactors.

Seems correct.
Every TEPCO Daiichi plant status report contains this passage:

Others
- At around 10:00 am on June 13, 2011, we started the operation of the circulating seawater purification facility installed at the screen area of Unit 2 and 3.
- At 8:00 pm on June 17, 2011, we started operation of Water Treatment Facility against the accumulated water. At 6:00 pm on July 2, we started the circulating injection cooling to inject the water, which was treated by the accumulated water treatment system, to the reactors through the buffer tank.

Simply check latest Tepco News to verify.
However this doesn't exclude other water or additives (boron) potentially being added to cooling water.

Yikes :-), now you've got me wondering how the contamination of the water in the R/B basements compares to that of the T/B basements and further downhill.

Let's praise TEPCO for wise decision to isolate both basements from each other.
(see Tsutsuji's posts on previous page).

 

[tsutsuji]

Or perhaps they think it might affect the water level in the drywell somehow.

I think there are two cases.

A) The leakage point is located lower than the present torus room water level

The leakage rate would depend on the difference of height between the drywell water level and the torus room water level. In this case, lowering the torus room water level would be a bad idea, because the leakage flow rate would increase, and this would affect the water level in the drywell (if the injection rate into RPV is kept constant).

B) The leakage point is located higher than the present torus room water level

The leakage rate would depend on the difference of height between the drywell water level and the leakage point. In this case, lowering the torus room water level would not affect the leakage rate nor the drywell water level.

So I think it would be good to install a water level gauge in the drywell, and perform the torus room drainage with an eye on the water level gauge. If the drywell water level starts decreasing, you know that you are in the wrong case and you must stop what you are doing. At least you learned something : you learned that you are in case A).

You may want to consider the present 60 cm above PCV bottom as a minimum that must be kept. To create a margin, you could increase the RPV injection rate until the drywell water level rises to 70 cm above PCV bottom.

If this water was not badly contaminated, you may have wanted to try to do the opposite: to raise the torus room water level, and see if it affects the drywell water level.

 

[MadderDoc]

<..>
We know for sure the hardened vent system is a totally separate system all the way to the stack. Early on (but post construction of this type of reactor unbelievably) it was found the SGTS would be inadequate and fail inside the RB during a high pressure venting scenario, filling it with steam and gases. So the hardened vent system was a retrofit to address this issue. <..>

Thanks a lot for your input.

I am not sure the hardened vent is a totally separate system at these plants. From what Tepco has said, such retrofits were indeed made to the plants. Also it would seem implied by what Tepco has said, that these vent lines were used for the PCV ventings. However, Tepco has speculated that the Unit 1 PCV vent might have back-flowed into the Unit 1 R/B through its SGTS piping, causing the explosion. And Tepco has more than speculated that Unit3 PCV vent back-flowed into the Unit4 SGTS system. Either of these theories by Tepco implies that the PCV vent lines and the SGTS lines are not separate all the way to the stack, and it would be implied that the SGTS lines were either not protected by back-flow valves (seems to be the case of Unit 1) or the back-flow valve had failed open when power was lost (units 2-4). (All the SGTS systems were presumably operating per automation from shortly after the earthquake, and until power was lost.)

 

[tsutsuji]

http://www.meti.go.jp/earthquake/nuclear/pdf/120328_02m.pdf Scattered debris survey plan (28 March 2012 mid-long term steering committee meeting)

[page 2]

Purpose

To perform a survey, checking whether debris spread by the hydrogen explosions are staying in the electric power plant premises.

Survey method

Explore regions of the premises starting at the center where units 1~4 are located, and going toward monitoring posts MP1~MP8. (As the first 500 m closest from center have already been explored and the debris there have been collected, they are excluded)

[page 3]

Definition of the debris that are the object of the survey

* Shape: solids (building rubble) like small stones or bigger that can be checked by visual observation
* Radioactivity, radiation dose: high radioactivity, high radiation dose objects that depart from background (BG)

Scattered debris determination standard

* When a debris is discovered, it is measured with a surveymeter (Geiger tube, ionization chamber). BG is also measured.
* If the measured value is higher than BG, the object is judged to be a scattered debris.

System

* Leader : 1 person, survey: 4 groups of 3 people (total 13 people)

Draft schedule

* 26 March 2012 ~30 March 2012 (2 April ~ 6 April is reserved in case of rain)

planned exposure

* Below 1 mSv/person.day

[page 4]

Fukushima Daiichi premises general layout map

Recording method
In case building debris scattered material is discovered, the discovery location is marked on a map. [Computing] the distance from units 2 and 3 reactor buildings with the premises layout map CAD system, the maximum scattering distance is measured and a map of the scattering area is generated.

[see also the map on page 4:]
red=plant boundary
yellow=scattered object survey directions
red dots=500 m range where scattering was confirmed

 

[tsutsuji]

http://www.meti.go.jp/earthquake/nuclear/pdf/120328_02x.pdf Results of survey of debris distribution in spent fuel pool, unit 4 (28 March 2012 mid-long term steering committee meeting)

[page 2/8]
1. Survey of debris distribution in unit 4 spent fuel pool
same as http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120312_01-e.pdf page 1

[page 3/8]
2. Outline of survey of debris distribution in unit 4 spent fuel pool
same as http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120312_01-e.pdf page 2

[page 4/8]
3. Result of survey of debris distribution in unit 4 spent fuel pool (19 ~ 21 March)

[page 5/8]
4. Outline of survey of debris at the bottom of unit 4's reactor
same as http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120312_01-e.pdf page 2 except "(if
necessary, we will use ROV)" which was deleted.

[page 6/8]
5. Result of the survey of debris at the bottom of unit 4's reactor
The diagram is the same as the one on http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120312_01-e.pdf page 4

[page 7/8]
6. New transparency check inside unit 4 spent fuel pool (20 March)

1. Checking method
At almost the same location as the last time (9 February), using the same camera, the same wire and marks, the visibility distance is measured.

2. result
Visibility was comparable with that of February 9. Therefore, we conclude that there
has been no change in the degree of transparency.

[The diagram does not require a translation as it is almost the same as the one on http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120210_03-e.pdf except that the man is now standing on the float, the fuel handling machine is not shown, and the spent fuel is not shown.]

[page 8/8]
7. Result of the transparency check inside unit 4 spent fuel pool (20 March)
same as http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120322_02-e.pdf

 

[tsutsuji]

http://www.meti.go.jp/earthquake/nuclear/pdf/120328_02d.pdf plant status (28 March 2012 mid-long term steering committee meeting) [only partial translation]

[page 1/6]
[A table displaying the plant parameters on 26 February and 27 March]

As unit 1, unit 2 and unit 3's PCV temperatures and RPV temperatures are around 25°C ~ 55°C (as of 27 March), there is no significant variation of RPV and PCV parameters such as the released radiation doses, and we judge that the cold shut down status is comprehensively maintained.

In order to maintain the measuring instruments' soundness in the future, while the surveillance with measuring instruments is continuing, a study toward diversification and implementation of alternative temperature surveillance means is under way.

[page 2/6]

[page 6/6]

 

[tsutsuji]

http://weather.goo.ne.jp/earthquake/12040123040.html There was a magnitude 5.9 earthquake off the Fukushima coast on 1 April 2012 at 23:04 JST. JMA seismic intensity scale　"5 minus" was recorded at Tomioka and Naraha, Fukushima prefecture. There is no tsunami risk.

http://www3.nhk.or.jp/news/html/20120401/k10014131781000.html The NISA said that no problem was reported from Fukushima Daiichi or Daini (in consequence of this earthquake). Monitoring post radiations are stable.

 

[hellbet]

Interesting scenes from TEPCO's video related to ocean monitoring of sea life in 20 km

Background plant looks like Hirono Power Plant (Fuel + Coal Plant) which is 10 Km South of Daini and 20 Km South of Daiichi; the 2 largest units on the middle are 1000 MWe and others are 600 MWe.

http://toolserver.org/~geohack/geoh...n&params=37_14_18_N_141_01_04_E_type:landmark

Dark smoke looks quite normal so Doom is off ;)

 

[MadderDoc]

The implementation of the common pipe to the stack from the SGTS and the hardened vent system includes a diving section just before the vent pipe enters the stack. It can be seen as a foo or a feature to have what is essentially a a water trap incorporated in such a system. On one hand it might provide additional scrubbing during a hardened vent procedure -- otoh it might also provide increased back-pressure, and increase the risk of diverting the flow of the vented gases back into the buildings through the SGTS system.

 

[tsutsuji]

http://www.tepco.co.jp/cc/press/betu12_j/images/120402j0101.pdf Report to NISA on units 1 ~ 3 thermometer reliability. (the NISA requested Tepco to write a report once a month) : some of the thermometers not previously evaluated were found to be usable, and some were found to be broken. Some thermometers that were not connected to a digital recorder have been connnected to a digital recorder.

According to the plot on page 126, unit 2's 69 TE-16-114L#2 RPV BELLOWS SEAL AREA, newly connected to a digital recorder (on 8 March 2012) reached 100°C on 19 March 2012. (but it is not marked as "broken"). TE-16-114L#1 is having a similar rising trend, reaching 83°C on 19 March 2012. I will be curious to see if those two are marked "broken" in next month's report.

 

[tsutsuji]

http://www3.nhk.or.jp/news/html/20120403/k10014177241000.html Because strong winds of 18 metres [per second] are expected, outdoor work with cranes is suspended at Fukushima Daiichi on 3 April afternoon. Crane arms have been made shorter. Sheets covering debris have been reinforced with weights and ropes.

 

[biggerten]

http://www3.nhk.or.jp/news/html/20120403/k10014177241000.html Because strong winds of 18 metres [per second] are expected, outdoor work with cranes is suspended at Fukushima Daiichi on 3 April afternoon. Crane arms have been made shorter. Sheets covering debris have been reinforced with weights and ropes.

About 40mph, for those of us counting on our fingers and toes.

 

[tsutsuji]

http://sankei.jp.msn.com/region/news/120403/fks12040320560003-n1.htm Unit 1's cover is designed to withstand winds up to 25 m/s. According to Tepco, in the case of winds stronger than the limit for unit 1's cover, the cover could be totally displaced by the wind and hit the building, but it was designed so that the load would be distributed and the building would not collapse or be damaged.

 

[clancy688]

Isn't that only Beaufort 10?

What's with the occasional typhoon? According to wikipedia, a typhoon's a storm with wind speeds of at least 118 km/h+ - which's 33.8 m/s. Everything below is a "severe tropical storm" or less. So even the weakest typhoon would already overstrain the construction by 35%.

Isn't Japan a country which's being hit by typhoons fairly often? Wasn't there a typhoon hitting Fukushima last year? So how big are the chances for the construction of being exposed to wind speeds it wasn't designed for?

 

[zapperzero]

So how big are the chances for the construction of being exposed to wind speeds it wasn't designed for?

I can't seem to find open-source analysis. Here's an extended abstract of some research paper:
http://ams.confex.com/ams/pdfpapers/137995.pdf

 

[MadderDoc]

Everywhere I read says the complete inventory of noble gases was released from the reactors in the early phase of the accident.

But if so, why does Kr-85 still linger in unit 2?
Recent measurements at inlet of Unit 2 PCV Gas Control System:
28 March 2012 : 73 Bq/cm³
03 April 2012: 97 Bq/cm³

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120404_01-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120329_01-e.pdf

Could it be an effect of continuing fuel damage?

 

[zapperzero]

Could it be an effect of continuing fuel damage?

Well, some small proportion of the fuel fissions spontaneously, no? Same story as with the earlier detection of Iodine and Xenon.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120405/1450_12ton.html At 1:50 AM on 5 April it was found that water was leaking from a pipe connected to the tanks where the water is stored after removing cesium. The leak stopped at 02:20 AM after closing a valve. It is thought that much of the 12 tons of water that leaked and include high concentrated strontium, have flowed to the sea. Tepco is investigating why the pipe junction failed and the quantity that flowed to the sea.

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120405_03-j.pdf diagram, pictures about this leak

 

[Yamanote]

Is there any detailed listing of all the radionuclides and their concentrations in the water from the reactor buildings available? I haven't seen one yet.

 

[MadderDoc]

A comparison of survey photos of the top of fuel racks in the spent fuel pool of unit 4, with the IAEA's map of assembly decay heat activities in the pool strongly suggests that the precipitation that has formed on top of the tie plates has been shaped by the magnitude of the decay heat of each individual assembly. On top of low activity assemblies, a uniform layer appears to have developed, with only few perforations over the water tubes. On higher activity assemblies a similar layer appears to have formed, but it tends to have been cracked up and/or blown away. Here illustrated with the comparison for rack no. 22:

A similar photo mount for rack no 09, and the original IAEA activity map of the racks are attached (as shown in this map, the racks are numbered from 00 upwards, proceeding from the lower left to the upper right).

 

[Cire]

A comparison of survey photos of the top of fuel racks in the spent fuel pool of unit 4, with the IAEA's map of assembly decay heat activities in the pool strongly suggests that the precipitation that has formed on top of the tie plates has been shaped by the magnitude of the decay heat of each individual assembly. On top of low activity assemblies, a uniform layer appears to have developed, with only few perforations over the water tubes. On higher activity assemblies a similar layer appears to have formed, but it tends to have been cracked up and/or blown away. Here illustrated with the comparison for rack no. 22:

A similar photo mount for rack no 09, and the original IAEA activity map of the racks are attached (as shown in this map, the racks are numbered from 00 upwards, proceeding from the lower left to the upper right).

This make sense. Hotter assemblies have induced thermals that carry away the lighter silt that has settled on them.

 

[MadderDoc]

This make sense. Hotter assemblies have induced thermals that carry away the lighter silt that has settled on them.

Yeah. While on the colder assemblies those thermals were weaker, so a layer of silt could well settle on them. Under the hypothesis that what we see is the sole result of preferential sedimentation on colder parts , we would predict the rack frames and the number tags on the racks to be all covered by silt, wouldn't we?

 

[tsutsuji]

A comparison of survey photos of the top of fuel racks in the spent fuel pool of unit 4, with the IAEA's map of assembly decay heat activities in the pool

Hello,

Would you be so kind as to provide links to the source documents where you found the photos and the "IAEA map of assembly" ?

 

[MadderDoc]

Hello,

Would you be so kind as to provide links to the source documents where you found the photos and the "IAEA map of assembly" ?

The photos are cropped frames from the Tepco survey video at

http://tepco.webcdn.stream.ne.jp/www11/tepco/download/120322_01j.zip

The map of assembly activities is cropped from the document "DOE Response to Fukushima Dai-ichi Accident"

which is included in these transcripts from the US DOE ACRS subcommittee on Fukushima May 26 2011 meeting (the map is on page 188 of those transcripts)
http://pbadupws.nrc.gov/docs/ML1114/ML11147A075.pdf

It must have been just my inference from recollection, that DOE had got the information on the Unit 4 SFP heat generation distribution via the IAEA, and I may be totally wrong, sorry. The document itself says nothing about how the data has been sourced. The original source for such detail of information must of course have been Tepco.

 

[tsutsuji]

Thanks. I had guessed the pictures were from Tepco's videos, but I was not aware about that DOE document.

 

[MadderDoc]

New and quite exciting photos from the spent fuel pool of unit 3
http://photo.tepco.co.jp/en/date/2012/201204-e/120413-01e.html
Pictures are taken close to the cask transfer area, they show upright standing fuel racks, and ..
a fine close up view of an end piece from the rail foot of the bridge that carried the fuel handling machine.

(Here seen compared to a Quince photo of the foot of the quite similar FHM bridge of unit 2

 

[SpunkyMonkey]

New and quite exciting photos from the spent fuel pool of unit 3...

Lol. I just came to post a link to that Tepco release. Great identity spot Maddder! More of you're non-stop top-notch analysis!

I seem to recall just a few weeks ago someone here called that the refueling crane simply fell into the pool (it wasn't blown to kingdom come) based on clues in a photo, but that least-extraordinary thesis was not too well received.

Here's a video clip of what clearly appears to be part of the refueling crane, I suspect it's the upper deck of the trolley. It's also the same object I posted previously, suggesting it looks like the trolley deck.

Here's a video expressing skepticism that the Unit-3 fuel pool exploded, which imo is further supported by the release of photos of fuel racks in SFP3. I think the Unit-3 explosion had nothing to do with the fuel pool, and the pool only suffered from in-falling debris.

 

[jim hardy]

I think the Unit-3 explosion had nothing to do with the fuel pool, and the pool only suffered from in-falling debris.

indeed Arnie's pool criticality hypothesis would have steam-cleaned it and scattered the contents. Instead it's gor rebar pointing in.

Yet in the satellite photo 3 minutes post-explosion it looks to be steaming vigorously.

if that's a correct interpretation of photo it got a lot of heat from someplace.

Last spring I calculated ~10^18 neutrons into Keff of 0.95 would make a thousand pounds of steam
but couldn't come up with a path from core to SFP that doesn't go through a few tenth-value thicknesses of concrete...
so another scheme worthy of Wiley Coyote bit the dust.

 

[hellbet]

Nice catch MadderDoc, it was all but evident to identify the FHM Trolley skating. Looks like one find out FHM3... finally.

 

[SteveElbows]

Yet in the satellite photo 3 minutes post-explosion it looks to be steaming vigorously.

if that's a correct interpretation of photo it got a lot of heat from someplace.

Easy for that to be the wrong interpretation of that photo. Release could be from the edges of the reactor well plugs, not the pool.

 

[SteveElbows]

I seem to recall just a few weeks ago someone here called that the refueling crane simply fell into the pool (it wasn't blown to kingdom come) based on clues in a photo, but that least-extraordinary thesis was not too well received.

Thats largely my fault, but that's because I did not consider the round objects in the photo to be a great match for refuelling bridge pulleys. This didn't mean I ruled out the possibility that the refuelling thing was in the pool, I just didn't think the images presented were good enough evidence. Subsequently someone pointed out a related ladder and I did find a good video showing that, so despite my original negativity about the analysis I was not dead against it.

I hope that when we get to see the video things become slightly clearer, but debris of one sort or another in reactor 3 pool is clearly quite a big problem.

 

[Yamanote]

They also did some investigations on the integrity of unit 4:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120413_04-e.pdf

 

[tsutsuji]

They also did some investigations on the integrity of unit 4:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120413_04-e.pdf

Thanks. This is a follow-up of the February measurements. It is good that it is now translated into English.

http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/m120227_05-j.pdf On page 85/94 there are four measurements of the distance between the reactor well water level and the 5th floor's floor in four locations. The measurements show that the floor is horizontal. It looks like the old "unit 4 is leaning" theory is ruled out...

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120413/index.html (survey into unit 3 SFP) the camera was lowered by about 7 m underwater. It was confirmed that part of the fuel handling machine (35 tons) has fallen into the pool. No conspicuous fuel damage was seen on the pictures. As it is dark inside the pool, the photography was not good and only 4 pictures were publicly released. Tepco said "With today's survey we could not understand the details of the situation. We shall perform more surveys so that we can find out the debris distribution and the fuel status, so that we can study a safe fuel removing method."

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120413/1510_teishi.html The nitrogen injection system into units 1,2,3 was suspended this morning for 2 and a half hours shortly after 01:00 AM. It is the 4th time it happens since last month (it previously happened on 12 March, 4 April and 7 April). Tepco is investigating the causes. As a consequence, unit 1's PCV temperature rose by 5°C from 50°C to 55°C from 04:00 AM to 06:00 AM. There was a leak from a joint in unit 4's pool cooling system. 40 liters of water including radioactive substances leaked into the building. Tepco does not know when the pump can be restarted.