Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[MadderDoc]

Unit 3 explosion (was Re: Japan Earthquake: nuclear plants)

I think the suggested concentration differences are not necessary to explain the result.

Something is necessary to explain the particular damages of the SE corner of the roof.

 

[Uagrepus]

Based on the remnants of U4 top section, the double fireballs IMHO are most likely originated from between north/south wall and roof, and not necessarily from the corners.

I agree, that the leaking containment in the middle between north and south wall was most likely the origin of large amounts of hydrogen and steam in Unit3 and makes the difference to Unit4. But if hydrogen leaks from there, we get automatically concentration gradients, because the concrete plug is not in the center of the building the three or more leakage beams might have been directed.

From looking at the earliest initial frames I suggest this timeline of the combustion:

1.) There is already H2 in the building on several floors. ("chemical hydrogen bomb building")
2.) Around the concrete-lid beams of H2 and steam escape directed to the service floor.
3.) Somewhere in the building H2 ignites.
4.) The roof begins to collapse and parts of the west-wall are blown away on several floors (no fireballs/flames there, H2 explodes with an excess of O2 inside the building)
5.) While the roof is collapsing, the high-concentrated H2 in the east half of the upper floor combusts in a fireball, now having contact to enough fresh air outside the building.
6.) A steam explosion/flash boil over the SFP is triggered (unsure, unconfirmed).

Just a hypothesis, not more.

 

[MadderDoc]

I agree, that the leaking containment in the middle between north and south wall was most likely the origin of large amounts of hydrogen and steam in Unit3 and makes the difference to Unit4. But if hydrogen leaks from there, we get automatically concentration gradients, because the concrete plug is not in the center of the building the three or more leakage beams might have been directed.

From looking at the earliest initial frames I suggest this timeline of the combustion:

1.) There is already H2 in the building on several floors. ("chemical hydrogen bomb building")
2.) Around the concrete-lid beams of H2 and steam escape directed to the service floor.
3.) Somewhere in the building H2 ignites.
4.) The roof begins to collapse and parts of the west-wall are blown away on several floors (no fireballs/flames there, H2 explodes with an excess of O2 inside the building)
5.) While the roof is collapsing, the high-concentrated H2 in the east half of the upper floor combusts in a fireball, now having contact to enough fresh air outside the building.
6.) A steam explosion/flash boil over the SFP is triggered (unsure, unconfirmed).

Ad 2-3. Hydrogen jets are prone to autoignition and detonation speed flame front propagation at ignition.
Ad 4. It is unlikely that the west-wall, as regards the concrete pillars were blown away by an explosion,considering how orderly they fell. More likely the concrete pillars were left temporarily standing while the panels were blown away, only to tumble to the ground in good order, in connection with the total collapse of the roof.
Ad 5. An ignited hydrogen jet directed at the SE corner inside the building could have caused the special damage to the roof structure there, initiated the collapse of the roof, and provided for the escape of the hydrogen seen burning outside the building.
Ad 6. Providing special conditions for an eruption of steam and water from the SFP adds complexity unnecessarily. Steam and water would erupt from the PCV in the heels of hydrogen by physical necessity due to the pressure drop, if 2) is initiated by a sudden development of a PCV leak.

An additional assumption would seem to be needed for the final touch, namely that the SE corner was hit by roof covering fragments that had been lifted to great heights by the mushroom cloud forming eruption.

 

[Rive]

Something is necessary to explain the particular damages of the SE corner of the roof.

All I'm telling is that on the south and north side of the buildings the top of the wall is not fixed to roof beams, so:
- in case of an internal explosion the connection between the N/S wall top and the roof would be the first to give up (and release the last breaths of a fireball)
- without the pull of the roof beams the columns of N/S walls would most likely break and fall almost immediately.

Sorry, I don't have enough time to completely walk this around, so I'm just trying to add some pieces :-(

 

[MadderDoc]

Thanks for the link. Does anyone know what the vertical orange "thing" in the unprocessed image is? The processed image doesn't have such an artifact. What kind of processing is done anyway? Adjustment for the distance of the radiation source from the camera?

It is also not clear to me what is going on there. However they appear to be able to combine measurements to produce a 3D representation of the air dose rate in the building. With that in hand they would be able to subtract from 2D measurements of surfaces, the fraction of gamma that is received from the air , such as to be able to discern gamma emitting surfaces more clearly through the air contamination 'fog'.

The vertical orange thing otoh, clearly an artefact, but would not seem to be explainable by air dose. It might be a camera error, at the edges of the field, which can also be corrected for, by combining measurements from the rotating camera.

 

[Rive]

1.) There is already H2 in the building on several floors. ("chemical hydrogen bomb building")
2.) Around the concrete-lid beams of H2 and steam escape directed to the service floor.
3.) Somewhere in the building H2 ignites.
4.) The roof begins to collapse and parts of the west-wall are blown away on several floors (no fireballs/flames there, H2 explodes with an excess of O2 inside the building)
5.) While the roof is collapsing, the high-concentrated H2 in the east half of the upper floor combusts in a fireball, now having contact to enough fresh air outside the building.
6.) A steam explosion/flash boil over the SFP is triggered (unsure, unconfirmed).

Just a hypothesis, not more.

Point two would match nicely with the maybe-starting of events at frame -2. Overpressure building up fast inside the building might be enough to explain some unexpected, but less dramatic changes on the webcam picture.

For point five: if there is a continuous leakage then you can give all the H2 on the upper/lower floors to the initial blast and still there will be enough 'new' Hydrogen/steam for the mushroom. And such kind of flame would give you that kind of constant heat what the blast can't (source of the heat marks on the roof components?).

 

[MadderDoc]

All I'm telling is that on the south and north side of the buildings the top of the wall is not fixed to roof beams, so:
- in case of an internal explosion the connection between the N/S wall top and the roof would be the first to give up (and release the last breaths of a fireball)
- without the pull of the roof beams the columns of N/S walls would most likely break and fall almost immediately.

Sorry, I don't have enough time to completely walk this around, so I'm just trying to add some pieces :-(

Indeed the north wall at least would have seemed to have been blown out quite early complete with pillars, wall panels, dragging the north part of the roof construction with it. judge this from the way parts of it ended up outer face up on top of the RW building and leaving beams pointing upwards in the remains of the roof on top of the building. Apparently the northern edge of the roof construction was fixed better to the wall, than it was to the rest of the roof construction. Assumedly the same holds true for the south end. The SW corner of the roof construction does seem to have been fractured in much the same manner as seen along the north wall, while of course the SE corner is different.

 

[MadderDoc]

Point two would match nicely with the maybe-starting of events at frame -2. Overpressure building up fast inside the building might be enough to explain some unexpected, but less dramatic changes on the webcam picture.

For point five: if there is a continuous leakage then you can give all the H2 on the upper/lower floors to the initial blast and still there will be enough 'new' Hydrogen/steam for the mushroom. And such kind of flame would give you that kind of constant heat what the blast can't (source of the heat marks on the roof components?).

The PCV is a limited source of hydrogen. Its content would be enough for a decent temporary flare and the explosion of the building, but you wouldn't be able to build the mushroom cloud on the basis of the amount of steam that could be produced by it's emptying itself of hydrogen, and its combustion. However, likely the water in the PCV would be flash boiling once the hydrogen pressure were to be relieved, which would make up for a massive temporary source of steam.

 

[MadderDoc]

Good view, best seen so far, of the SE corner of Unit 3, from recent press package:
http://photo.tepco.co.jp/library/120528_01/120528_35.jpg

 

[Yamanote]

Many new photos and videos:

http://photo.tepco.co.jp/en/index-e.html

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120528/0945_4gouki.html In July, Tepco will remove two fuel assemblies from unit 4's spent fuel pool as a test. These two fuel assemblies will be two of the 204 unused fuel assemblies stored in the pool. Tepco has to check how much these fuel assemblies were damaged by the seawater. In comparison with the spent fuel assemblies, the unused fuel assemblies are comparatively less dangerous to remove.

http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02z.pdf Check of soundness of new fuel (unirradiated fuel) in unit 4 spent fuel: This a document from the 6th mid-long term government-Tepco meeting held on 28 May 2012, with details about the removal of unused fuel, and the concerns about corrosion.

http://www.tepco.co.jp/en/press/corp-com/release/2012/1204777_1870.html "Receipt of [NISA] instruction document regarding the seismic safety evaluation of Unit 4 at Fukushima Daiichi Nuclear Power Station"

http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02j.pdf Endoscope mission into unit 1's PCV scheduled in the last ten days of August and the first 10 or 20 days of September 2012 (document from the 6th mid-long term government-Tepco meeting held on 28 May 2012). On page 4/8 you can see the two types of cameras that they are going to use. One of them can be tilted and will be used above the grating. The other camera is going to go below the grating.

 

[Uagrepus]

Overpressure building up fast inside the building might be enough to explain some unexpected, but less dramatic changes on the webcam picture.

Yes, there seems to be a slight expansion of the building in frame #-4 to #-1 due to overpressure (by the leakage?). The next plausible step suggested MadderDoc: "Hydrogen jets are prone to autoignition[...]". In the next frame #0 (after autoignition?) the building contracts on the upper floor (by eaten up oxygen 2H2+O2->2H2O?). Roof parts sucked-in/collapsing? The roof panels found around the SFP could be also from this early implosion. The later fireball from above had another downward component onto the panels.

In #0 and #1 we see the beginning of the expansion phase IMHO, when everything heats up by the H2/O2-reaction, and devastions as in your szenario happen:

More likely the concrete pillars were left temporarily standing while the panels were blown away, only to tumble to the ground in good order, in connection with the total collapse of the roof.

And such kind of flame would give you that kind of constant heat what the blast can't (source of the heat marks on the roof components?).

However, likely the water in the PCV would be flash boiling once the hydrogen pressure were to be relieved, which would make up for a massive temporary source of steam.

Good points, but its hard for me to imagine, that this huge mushroom cloud has its source in three or four of these tight leaks in the gate area:

 

[MadderDoc]

<..>its hard for me to imagine, that this huge mushroom cloud has its source in three or four of these tight leaks in the gate area:

I'd say that the source of the huge mushroom cloud is the huge vertically rising eruption cloud that was initially formed over the building. Expressed like that it becomes clear that a considerable explosive expansion is involved, through a restricted opening pointing generally up. In short, there is vertical thrust. When we first see the initial eruption cloud it has an ascent rate of impressive 75 m/s (unlike the mushroom cloud which emerges from the top of the eruption cloud at about 5 seconds after the blast; the continued rise of the mushroom cloud is at a more leisurely yet still impressive pace of about 20 m/s.

It is difficult to imagine the scale of things in these reactor buildings. I still can only abstractly grasp that the house I am sitting in, including the annex out in the back could be put into that equipment pool, and it wouldn't even be a tight fit.. The 'tight leak' the steam is apparently escaping from in that photo is a gap of about 0.2 x 1 meter. Now I am not at all sure this gap was not produced by the erupting steam, rather than pre-existed it to allow it to escape, however in any case this ultimately ends out in a question of mass flow. We would be looking at in the order of magnitude 100 tons of liquid water 'wanting' to come out and expand into 100000 cubic meters of steam. This is heavy stuff, a considerable work force. We would need it to escape over a brief span of time, say 2 seconds. Assuming 5 'tight leaks', that would be an opening of 1 square meter, and a mass flow through that opening of about 50 tons/second.

 

[Uagrepus]

[...] huge vertically rising eruption cloud that was initially formed over the building.

"Over the building" is not easy to locate in an exploding building, but there might be the key. The explosion kinetics changed IMHO in the moment, when most of the roof was open from the first implosion/explosion more or less inside the building. The two fireballs SE and NE mark the first explosion-events in this transition from inner to outer space on top of the building. While these events happened, most likely the eruption of hydrogen and steam from the PCV continued. Eventually being dispersed from the shockwaves around the eruption cloud rises and explodes (now surrounded by and mixed with enough air) over the structures formerly known as roof.

 

[MadderDoc]

"Over the building" is not easy to locate in an exploding building, but there might be the key. The explosion kinetics changed IMHO in the moment, when most of the roof was open from the first implosion/explosion more or less inside the building. The two fireballs SE and NE mark the first explosion-events in this transition from inner to outer space on top of the building. While these events happened, most likely the eruption of hydrogen and steam from the PCV continued. Eventually being dispersed from the shockwaves around the eruption cloud rises and explodes (now surrounded by and mixed with enough air) over the structures formerly known as roof.

Yes, alright, over the building is not too precise. In this animation, three small red dots are overlayed to mark the direction to the visible NW, SW, and SE corner of the building, thus roughly outlining the confines of the original building when things get messy in the images.

Frame 0 is the first frame which unambiguously shows damage to the building. I think it is safe to assume that between frame -1 and frame 0, an explosive combustion of hydrogen occurred inside the building. In frame 1 we see hydrogen apparently combusting outside the confines of the building, in white hot intensity. As regards the direction to this visual flame, it could be from either the south or the east wall of the SE corner. The three-lobed shape of the flame would indicate to me that it is from the east wall. The condensed combustion gases from this flame is, I believe, what we see eventually develop into a notably _whitish_ 'wart' in frame no 35, to the right bottom downwind side of the developing central eruption cloud. It would seem to me most likely from the observation, that between frame 0 and frame 1, hydrogen escaped from the building from its SE corner in an upwards easterly direction and burned there, outside the confines of the building.

Seeing hydrogen could escape from the building, it would seem to be implied there is hydrogen in it, so either hydrogen is burning still inside the building during frame 0-1, or frame 1 could represent a flash back to re-ignite hydrogen inside a oxygen starved building, now being fed air through openings in the roof.

 

[Yamanote]

...

Thanks for the news tsutsuji-san, quite interesting!

 

[tsutsuji]

The 6th mid long term meeting was held yesterday: http://www.meti.go.jp/earthquake/nuclear/20120528_02.html

The 5th meeting (23 April 2012) : https://www.physicsforums.com/showpost.php?p=3881074&postcount=12979

The 4th meeting (28 March 2012) : https://www.physicsforums.com/showpost.php?p=3838108&postcount=12764

The 3rd meeting (27 February 2012) has been translated into English on Tepco's website : http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/conference-e.html

28 May 2012 government-Tokyo Electric mid and long term response committee, steering committee (6th meeting)

http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02a.pdf Agenda
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02b.pdf Participants

Document 1
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02c.pdf Abstract of the proceedings of 5th steering committee meeting

Document 2: Plant status
Document 2-1: Plant status
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02d.pdf Plant parameters
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02e.pdf Accumulated water storage status

Document 3 Study and execution of each special plan

3-1 Cooling by closed loop water injection
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02f.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02g.pdf Summer season countermeasures for the reactor water injection equipments [page 3/5: unit 2's reactor temperature is expected to reach 65°C in July when the weather is the hottest]
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02h.pdf Results of the surveys on location concerning the environment improvement for the purpose of installing alternative thermometers in unit 2's RPV.
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02j.pdf Execution of internal survey into unit 1 primary containment vessel (PCV) [endoscope mission in August-September 2012]
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02k.pdf Results of the survey into unit 3's TIP room in reactor building first floor

3-2 Treatment of accumulated water
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02m.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02n.pdf Subdrain purification test report (report No. 1)3-3 Countermeasures to reduce environmental radiations
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02p.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02q.pdf Management of debris, cut down trees, generated by the response to the accident
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02r.pdf Status of the preparatory works of the soil-covered temporary storage facility
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02s.pdf Countermeasures against fire for the cut down trees
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02t.pdf Consequences on water quality of the covering of the sea floor in the harbour
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02u.pdf Results of evaluation of additional releases from reactor building's primary containment vessels

3-4 Improvement of working conditions
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02p.pdf Schedule

3-5 Countermeasures for spent fuels pools
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02w.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02x.pdf Debris removal work, reactor building top part, unit 3
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02y.pdf Debris removal work, reactor building top part, unit 4
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02z.pdf Check of soundness of new fuel (unirradiated fuel) in unit 4 spent fuel pool
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02aa.pdf Results of inspection aimed at checking the soundness of Fukushima Daiichi unit 4's reactor building

3-6 Preparations for fuel debris removal
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02bb.pdf Schedule [a robot mission into unit 3's torus room is scheduled for the last 10 days of June]
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02cc.pdf Results of survey by robots into unit 1's reactor building: "development of remote controlled decontamination techniques inside buildings"

3-7 treatment and disposal of radioactive waste
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02dd.pdf Schedule

Document 4
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02ee.pdf roadmap progress (abstract)

28 May 2012 government-Tokyo Electric mid and long term response committee, technical development progress headquarters (6th meeting) (http://www.meti.go.jp/earthquake/nuclear/20120528_01.html )

http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01a.pdf Agenda

Document 1
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01b.pdf Abstract of the proceedings of 5th meeting

Document 2
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01c.pdf Fiscal 2012 research and development plan (draft)

Spent fuel pool countermeasures working team

Document 2-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01d.pdf Evaluation of long term soundess of the fuel assemblies removed from spent fuel pools (Fiscal 2012 and general plan)

Fuel debris removal preparation working team

Document 2-2-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01e.pdf Development of remote controlled decontamination techniques inside buildings (Fiscal 2012 and general plan)
Document 2-2-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01f.pdf Development of techniques to determine the leakage points inside PCVs (Fiscal 2012 and general plan)
Document 2-2-3 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01g.pdf Development of techniques to repair PCVs (Fiscal 2012 and general plan)
Document 2-2-4 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01h.pdf Development of techniques to survey inside PCVs (Fiscal 2012 and general plan)
Document 2-2-5 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01j.pdf Development of techniques to assess the soundness of RPVs/PCVs (Fiscal 2012 and general plan)
Document 2-2-6 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01k.pdf Development of techniques to manage debris criticality (Fiscal 2012 and general plan)
Document 2-2-7 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01m.pdf Grasping the status inside reactors by the upgrading of accident progression analysis techniques (Fiscal 2012 and general plan)
Document 2-2-8 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01n.pdf Characterization by using mock-up debris and development of debris treatment techniques (Fiscal 2012 and general plan)
Document 2-2-9 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01p.pdf Building of material accountancy for fuel debris (Fiscal 2012 and general plan)

Treatment and disposal of radioactive waste working team

Document 2-3-1 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01q.pdf Development of treatment and disposal techniques for the secondary waste products generated by the contaminated water treatment (Fiscal 2012 and general plan)
Document 2-3-2 http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01r.pdf Development of treatment and disposal techniques for radioactive waste (Fiscal 2012 and general plan)

Document 3
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01s.pdf Result of the public appeal for a technical catalogue in relation with the machinery and equipments used in the preparation of the fuel debris removal, toward the decommissionning process of Fukushima Daiichi units 1,2,3 and 4 (Tokyo Electric Power Company)

Document 4
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01t.pdf Status of the study of the conseption of research basic points

Attachment: http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_01u.pdf Symposium on machinery and equipments toward the decommissionning process of Fukushima Daiichi [held by the Japan Society of Mechanical Engineers on 27 May 2012][page 2: 2012 IEEE International Conference on Robotics and Automation (ICRA 2012) Symposium on Robotic Solutions Toward Nuclear Decommission May 18 (Friday), 2012 in Saint Paul, USA]

 

[Uagrepus]

As regards the direction to this visual flame, it could be from either the south or the east wall of the SE corner.

I would vote for 2 east and 1 south, forming the "three-lobed shape of the flame":

Most of the roof-panels in the SE-corner of U3 are oriented east-west and many were thrown to the turbine-building following this direction.

 

[MadderDoc]

I would vote for 2 east and 1 south, forming the "three-lobed shape of the flame":

http://i49.tinypic.com/104l3cl.png

Most of the roof-panels in the SE-corner of U3 are oriented east-west and many were thrown to the turbine-building following this direction.

Agreed. From about frame 4, destruction of the south wall appears to have progressed to let the flame burn more generally out through the top of that wall. During frame 0-4, there seems to be no discontinuity in the exploding motion in the rest of the building that is set going in frame 0. From about frame 5 the fuel supply for the flame seems to be gradually cut of, while the development of the eruption cloud center is taking over the scene. Concurrently with this change material seems to start being ejected from a lower part (likely 4th floor) of the west wall.

 

[tsutsuji]

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120526_01-e.pdf Accumulated water in unit 3 Radiation Waste Underground Storage Facility Building: "Accumulated water amount is approx. 610m3 in the entire building (including the unchecked areas). The property of the accumulated water is assumed to be either groundwater or rainwater".

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120529_03-e.pdf Plant Status of Fukushima Daiichi Nuclear Power Station, May 29, 2012:

May 28, 2012: The following Unit 2 PCV thermometers (monitored in accordance with Article 138 of the Technical Specification) indicated significant temperature changes (stepwise increase/decrease in temperature). Upon our temperature trend evaluation, we found that these temperature changes may have been caused by abnormality with the thermometers. On May 29, direct resistance measurement was done on these thermometers, and reliability evaluation will also be done. According to the radioactivity density of short half-life nuclides, there is no possibility of re-criticality.

- RETURN AIR DRYWELL COOLER (TE-16-114A) [Monitored] 58.0℃→64.7℃
- RETURN AIR DRYWELL COOLER (TE-16-114D) [Monitored] 43.7℃→47.6℃
- SUPPLY AIR D/W COOLER HVH 2-16A (TE-16-114F #1) [Reference] 41.0℃→35.0℃
- SUPPLY AIR D/W COOLER HVH 2-16C (TE-16-114H #1) [Monitored] 52.1℃→48.2℃
(Above data was acquired from 5:00 PM to 11:00 PM on May 28)

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120529_02-e.pdf Temperature inside the PCV of Unit 2, Fukushima Daiichi NPS (6 hour data)

 

[MadderDoc]

Most video footage of the explosion which have been or remain still available have been quite unfortunately re-sampled and re-compressed from an original 50Hz interlaced TV recording, to e.g. the commonly found 29.968fps on youtube. Unavoidably such a conversion produces horrible artefacts, and comes with loss and blending of the original information.

From a short lineage recording of an original TV broadcast, it has been possible to produce this http://www.gyldengrisgaard.eu/fuku_docs/unit3cloud50fps/ . Since the original is 50 Hz interlaced, utilising both fields yields a temporal resolution of 50 fps, or 20 milliseconds per frame. You won't find this better anywhere else on internet :-)

Those of you who have taken special interest in the explosion will note particularly the extra temporal resolution at around the time of the first signs of something happening with the building.

 

[triumph61]

New interesting Photos

Reaktor Cap Unit
http://photo.tepco.co.jp/library/120528_01/120528_34.jpg

http://photo.tepco.co.jp/en/date/2012/201205-e/120528_01e.html

 

[tsutsuji]

The 6th mid long term meeting was held yesterday: http://www.meti.go.jp/earthquake/nuclear/20120528_02.html

28 May 2012 government-Tokyo Electric mid and long term response committee, steering committee (6th meeting)


http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02j.pdf Execution of internal survey into unit 1 primary containment vessel (PCV) [endoscope mission in August-September 2012]

Translation:

1/8

2/8

3/8

 

[tsutsuji]

Translation:
4/8

5/8

6/8

 

[tsutsuji]

Translation:
7/8

8/8

 

[Joffan]

Thanks very much for the translation Tsutsuji. I'd still prefer one of these snake robots doing the inspection work.

 

[Rive]

Translation:

Very thanks for the translation.

What do you think, would it worth to contact them somehow for suggesting a lights-off time during the survey? Based on some cherenkov (background) lights the cam might be able to pick up more details even in 'rainy' environment than with the small LEDs on the camera.

 

[tsutsuji]

Thanks very much for the translation Tsutsuji. I'd still prefer one of these snake robots doing the inspection work.

They did not talk specifically about a snake bot, but in the March report they were open about "self propulsion of the extremity" in case the conventional endoscope technique is not workable for the insertion of the alternative thermometers at unit 2 :

(3) mechanism for the inserted thermocouple, etc. (features to be developped)
* As the stroke is long, insertion might not be possible by pushing force only

Study of insertion mechanism
* Reducing the candidates to a short list, the features are checked in mock-up tests (it is possible that universal products won't pass the tests)
* Insertion resistance control method when insertion is performed in accordance with the pipe (it is necessary to feel elbows, orifices)

Solutions to (3)
* testing of the characteristics of materials and machinery ; suitability checking with mock-up
* If suitable materials and machinery don't exist, it is necessary to develop new ones as follows:
⇒self propulsion of the extremity (a new development is necessary, but as the diameter is small, it is difficult)
⇒self adjustment of the extremity (development of a mechanism to change the direction of the extremity so that the insertion is performed in accordance with an elbow, etc.)
⇒auxiliary mechanisms (study of insertion auxiliary methods using compressed gas, compressed water, etc.)

however, the mock-up tests performed last month showed that the conventional endoscope technique is likely to be OK or nearly OK.

Can radio waves penetrate through the PCV wall ? If not, the snake would still need a cable to send data and to receive control signals.

 

[Joffan]

Can radio waves penetrate through the PCV wall ? If not, the snake would still need a cable to send data and to receive control signals.

The snake robot shown was on an umbilical - probably for power, data, and pull-back. They'd probably need to protect the edges of any drilled holes.

 

[Astronuc]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120528/0945_4gouki.html In July, Tepco will remove two fuel assemblies from unit 4's spent fuel pool as a test. These two fuel assemblies will be two of the 204 unused fuel assemblies stored in the pool. Tepco has to check how much these fuel assemblies were damaged by the seawater. In comparison with the spent fuel assemblies, the unused fuel assemblies are comparatively less dangerous to remove.

http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02z.pdf Check of soundness of new fuel (unirradiated fuel) in unit 4 spent fuel: This a document from the 6th mid-long term government-Tepco meeting held on 28 May 2012, with details about the removal of unused fuel, and the concerns about corrosion.

Fresh fuel would not be dangerous itself - I've handled fresh fuel (even pellets) with gloves - however, the surfaces would be contaminated with whatever radionuclides were deposited from any fuel that failed in the pool (or from whatever fission products were released to the spent fuel pool) during the accident.

Ordinarily, damaged fresh fuel is often returned to the manufacturer (in this case, after decontamination) and defueled. The UO₂ is recycled and the Zircaloy is scrapped. It could be remelted and recycled if the impurities are less than ASTM spec.

 

[MadderDoc]

<..>
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02z.pdf Check of soundness of new fuel (unirradiated fuel) in unit 4 spent fuel pool<..>

I wonder what kind of sick paranoia has led to the blocking out of the rack number in the photo on page 5 of that document.
(It is rack number 26, if someone should want to know.)

 

[tsutsuji]

The 6th mid long term meeting was held yesterday: http://www.meti.go.jp/earthquake/nuclear/20120528_02.html

28 May 2012 government-Tokyo Electric mid and long term response committee, steering committee (6th meeting)
...

3-5 Countermeasures for spent fuels pools
http://www.meti.go.jp/earthquake/nuclear/pdf/120528/120528_02z.pdf Check of soundness of new fuel (unirradiated fuel) in unit 4 spent fuel pool

Translation:

1/8

2/8

3/8

 

[tsutsuji]

Translation:

4/8

5/8

6/8

 

[tsutsuji]

Translation:

7/8

8/8

 

[westfield]

They are from the west wall of the pool, 4th floor, the same wall section which the recent announcement is showing a lower portion of in a sharp angle, the photo bottom right in
http://2.bp.blogspot.com/-e4hpgfA9W...jMc2lWo/s1600/fukushimareactor4SFPMay25-7.JPG

(The photos are from the original survey of Unit 4 damages done in Nov. 2011, source:
http://photo.tepco.co.jp/en/date/2011/201111-e/111110_01e.html)

Perhaps I'm being too finiky but the images from 2011 don't quite show the "west wall" of the SFP as such.

The 2011 images cover the areas marked in green here.