Japan Earthquake: Nuclear Plants at Fukushima Daiichi

nikkkom · Apr 23, 2013

tsutsuji said:

On page 7/7 they say they will survey the existing technologies in Japan and abroad concerning tritium removal. They want to "promptly study" their feasibility.

Tritium removal on this scale (hundreds of thousands of tons of water) and low concentration is impractically costly.

tsutsuji · Apr 25, 2013

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130425/1355_daijin.html From 26 April to 3 May, Japanese Environment vice-minister Fukui will visit Chernobyl and the site at Hanford in the US state of Washington, where plutonium used to be produced, in order to learn about the latest technology and the experience of responding to the populations' needs.

tsutsuji · Apr 27, 2013

LabratSR · Apr 30, 2013

Debris Removal from the Upper Part of Unit 3 Reactor Building

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130422_08-e.pdf

ronaldkr · May 14, 2013

They are rushing it: now they are dismantling the Tepcotent to prepare the unloading of the SFP of unit 1.

This was published under "Photos for press" only:

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130509_07-e.pdf

SteveElbows · May 16, 2013

They are testing nitrogen injection into the reactor 2 suppression chamber.

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130513_08-e.pdf

tsutsuji · May 17, 2013

tsutsuji · May 17, 2013

Fukushima Daiichi decommissioning countermeasure promoting conference, 2nd secretariat meeting, 26 April 2013

http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d130426_01-j.pdf Agenda
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d130426_02-j.pdf Participants

Document 1
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d130426_03-j.pdf Plant status

Document 2
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d130426_04-j.pdf Mid and long term roadmap progress status (summary)

Document 3 : Study and execution of each special plan
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d130426_05-j.pdf (4.38 MB, 181 pages, Japanese)

3-1 Cooling by closed loop water injection
1/181 - 2/181 : Schedule
3/181 - 11/181 : Countermeasures against Unit 2 TIP guide tube obstructing objects and future progression methods

3-2 Treatment of accumulated water
12/181 : Schedule
13/181 - 39/181 : Multinuclide removal facility hot test
40/181 - 65/181 : Ground water bypass progress status and preparations toward start

3-3 Countermeasures to reduce environmental radiations
66/181 : Schedule
67/181 - 72/181 : Results of evaluation of additional releases from reactor buildings
73/181 - 77/181 : Specialist study group for the study of harbour seawater radioactive substance reduction

3-4 Improvement of working conditions
78/181 - 79/181 : Schedule
80/181 : Worker safety securing actions and achievements (2012) and plans (2013)
81/181 : Fiscal 2012 worker safety securing (accident table)
82/181 - 93/181 : Measures to secure fair labour conditions in subcontractor companies (survey results)

3-5 Countermeasures for spent fuels pools
94/181 - 95/181 : Schedule
96/181 : Layout map of working areas of units 3 and 4 top part debris removal work and covering work for the purpose of fuel removal
97/181 : Debris removal work, reactor building top part, unit 3
98/181 : Debris removal work, reactor building top part, unit 4
99/181 : Spent fuel storage status (as of 20 April 2013)
100/181 - 102/181 : Unit 3 reactor building top part debris removal work : equipments for spent fuel pool preservation and skimmer surge tank hatch cover preservation
103/181 - 104/181 : Unit 4 cover for spent fuel removal : steel frame construction work progress status
105/181 - 115/181 : Unit 2 reactor building operating floor gamma camera survey (analysis results report)

3-6 Preparations for fuel debris removal
116/181 - 117/181 : Schedule
118/181 125/181 : Unit 2 torus room survey results
126/181 - 135/181 : Unit 1 reactor building 1st floor personnel airlock room survey results
136/181 - 144/181 : Unit 2 reactor building 1st floor MSIV room survey results
145/181 - 163/181 : Unit 2 PCV internal survey (guide pipe removal)

3-7 Treatment and disposal of radioactive waste
164/181 : Schedule
165/181 : Debris, cut down trees management status
166/181 - 172/181 : Debris, cut down trees radiation reduction progress status
173/181 - 181/181 : Radiation analysis of accumulated water and treated water (interim report)

Document 4
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d130426_06-j.pdf Chronology and response status of "executive plan for reliability improvement countermeasures"

Document 5
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d130426_07-j.pdf Contaminated water leakage from underground tanks and response status

Document 6
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d130426_08-j.pdf IAEA press release provisional translation

Document 7
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d130426_09-j.pdf Public release of technical survey results to expand the technical catalogue for equipment and machinery development for fuel debris removal preparation

tsutsuji · May 18, 2013

tsutsuji said:

Contaminated water treatment countermeasure Committee (2nd meeting), 16 May 2013

3-1 contaminated water quantity reduction response measures

http://www.meti.go.jp/earthquake/nuclear/pdf/130516/130516_01k.pdf (2)

Translation :

Contaminated water quantity reduction countermeasures

1) Waterproofing of penetrations
Suppress by barring the openings or gaps of penetrations of underground trenches or pipes connected to buildings

Problems/feasibility:

Prediction of seepage routes and quantities;
Selection of waterproofing target locations;
Implement worker exposure reduction measures in locations with high radiation (high air dose rates, presence of high concentration contaminated water etc.).

2) Practical use of ground water bypass
Wells are dug on the western side of building which is the ground water flow's upsteam side, and by the forced bypass of the ground water flow to the buildings, the ground water in building vicinity is controlled.

Problems/feasibility:
Accurate control of ground water level in order to prevent in-building accumulated water leakage;
Suitable water quality control.

3) Practical use of subdrain
Ground water level around buildings is lowered by pumping up water from wells in buildings' vicinity.

Problems/feasibility:
Restoring and installing new subdrains in high radiation areas or where the work interferes with other works;
Running the subdrain in ajustment to the pumping out of the accumulated water, under accurate control of ground water level in order to prevent in-building accumulated water leakage;

4) Waterproofing of the gap between buildings
Buildings are set leaving an about 50 mm gap before the neighbouring building's underground wall. Because the penetrating pipes between buildings are concentrated, we waterproof the gap thus suppress ground water seepage.

Problems/feasibility:
Implementing worker exposure reduction measures in high radiation dose areas;
Performing the work where obstacles, such as underground structural parts, are present;
Interference with other works such as fuel removal.

5) Mountain side water insulating wall
By the installation of a water insulating wall such as a slurry wall or a frozen soil wall on the mountain side of the buildings (either on the OP 10 m or on the OP 35 m layer), the ground water flow from the mountain side to the buildings is suppressed and the ground water level in building vicinity is lowered.
By the control of the in-building accumulated water water level in adjustment to the lowered ground water water level, the seepage into buildings is refrained.

Problems/feasibility:
If a mountain side water insulating wall is built, controlling the amount of ground water level reduction in building vicinity is difficult. Especially during the duration of the work, it is feared that the ground water level around building becomes lower than the in-building accumulated water water level, and there is a risk that accumulated water seeps out.

6) Reactor building accumulated water water level control
After waterproofing between reactor building and turbine building (or radioactive waste building), the difference between reactor building accumulated water level and ground water level is reduced so that ground water seepage diminishes. Being located on the mountain side, the surrounding ground water level is higher around the reactor building than around the turbine building. By actively controlling the reactor building's water level and reducing the water level difference, the seepage of ground water is refrained.

The items needed to implement this response are:
- Installation of reactor building water exhaust equipment
- Waterproofing between reactor building and turbine building (or radioactive waste building)
Please note that inter-building waterproofing, while being relevant to reduce contaminated water boundary, is presently being planned as a way to dry up, as part of neighbouring buildings are being removed in order to install the foundation etc. in the case where a containment covering the reactor building is built for the purpose of fuel debris removal etc..

Problems/feasibility:
Reactor building water level control
It is necessary to secure technology to control the reactor building accumulated water level while monitoring the difference with the ground water level.

7) Filling torus room with grout
Penetrations, etc. are waterproofed by injecting grout into torus room (reactor building basement), so that ground water seepage into reactor building is reduced.

The items needed to implement this response are:
- Installation of equipment to take accumulated water from PCV.

Problems/feasibility:
It is necessary to secure waterproofing technology that is effective in stopping seeping water from downstream.

8) Filling building (turbine building) basement with concrete
By filling turbine building basement with concrete, ground water seepage into turbine building is reduced.

Problems/feasibility:
Removal of existing equipments;
Removal of existing equipments such as basement pipes, ducts, etc.
Treatment of accumulated water;
Building basement accumulated water pumping out and treatment.
Radiation reduction;
Reduction of air radiation so that work, such as existing equipment removal, is possible.

9) Polymer enclosure of turbine building basement contaminated water
By enclosing turbine building basement contaminated water with polymer, ground water seepage into turbine building is reduced.
Even if ground water seeps in, it can be converted into water devoid of tritium.

Problems/feasibility:
Remaining existing equipments;
It is impossible to completely absorb the water contained inside existing basement equipments such as pipes, ducts, etc.
It is necessary to check whether absorbed water may come out due to aging, etc..
Securing polymer treatment technology;
It is necessary to secure treatment and disposal after waterproofing

10) Use of PCV fuel debris air-cooling
At present, heat removal of the fuel debris contained in units 1,2,3 reactors and PCVs is done by water cooling by water injection. but in the future, as decay heat diminishes, it is possible to reduce the generation of contaminated water by shifting from water cooling to air cooling.
As additional generation of contaminated water is annulled, contamination reduction can be expected in the buildings where flowing presently occurs (turbine buildings, etc.).

Problems/feasibility:
Securing wind ventilation method;
- For the time being, as the decay heat is high, considerable ventilation power is needed (with the present decay heat, installation is difficult).
- At the earliest, decay heat is expected to become smaller by 2018, but further study is needed so that the air is uniformly blown onto the fuel debris.
Responding to the situation while the fuel is being removed;
- If the PCV has to be filled with water for the purpose of fuel removal, it means that contaminated water has to eventually be generated again, even if temporary air-cooling could be achieved.

11) Practical use of treated water into concrete
When tritiated water is used as concrete mixing water, 180 litre of water can be used per 1 m³ of concrete.
Under the hypothesis where 700,000 tons of tritiated water are used as concrete mixing water, 3,900,000 m³ of concrete have to be made.
If concrete making unit cost is estimated between ¥ 10,000 and ¥ 15,000 per m³, the concrete making spending amounts to about between ¥ 39,000,000,000 and ¥ 58,500,000,000.
Also, if we use crushed contaminated debris as concrete aggregate, it contributes to the global reduction of the total amount of waste. If we use the flyash from Hirono thermal power plant, it can contribute to the reduction of thermal power waste.

Application examples:
Application 1: for the construction of a 60 m wide base, 30 m high gravity type sea-wall covering the area in front of units 1 to 6, about 1,800,000 m³ are needed.
Application 2: If the harbour is filled with concrete, from 1,000,000 to 3,000,000 m³ are needed.
Application 3: If the valleys inside the plant premises are filled with concrete, the usable plant premise area is expanded. From 1,000,000 to 2,000,000 m³.
Application 4: Making concrete blocks, they can be assembled into a 230 m base, 146 m high pyramid, requiring 2,600,000 m³.

Problems/feasibility:
Environmental impact evaluation;
- Evaluation of consequences of tritium eduction after concrete coagulation
- Evaluation of consequences of mixing water vaporisation generated during concrete solidification
Increase of radioactive waste
It is possible that it becomes radioactive waste.

12) Exchange of deep layer ground water and tritiated water (proposal by committee member Maeda)
Exchange tritiated water with deep layer water so that it remains underground for the time until radiation sufficiently decreases by radioactive decay.

Problems/feasibility:
Study to be continued.

13) Manyfold barrier system construction (proposal by committee member Marui)
Construct a manyfold barrier (water insulating wall ?)

Problems/feasibility:
Study to be continued.

14) Building bottom soil freeze (proposal by committee member Maeda)
In addition to frozen soil barrier, the building's bottom is also turned into frozen soil.

Problems/feasibility:
Study to be continued.

15) water insulating wall, water pumping wells, facing, horizontal well combination (proposal by committee member Nishikaki)

(a) Perform assessment to obtain ground layer information
(b) Perform assessment to evaluate the continuity of the layer thought to be a low permeable layer. Check if that layer has about 1.0 E-6 cm/s permeability and 5 m thickness.
(c) If the low-permeable layer can sufficiently prevent the rise of ground water from downstream, the construction of a water-insulating wall near the boundary line can cut the ground water flow from upstream into the contaminated area.
(d) The ground water from above the water-insulating wall should permeate downstream making a detour around the water-insulating wall, but if it flows into the contaminated area by overflowing over the water-insulating wall, wells are dug in those locations in order to prevent upstream water level from rising.
(e) Even if the ground water percolation from upstream is cut, as cutting percolation and flow from rainfalls onto the surface is difficult, a urethane type waterproof layer or asphalt layer is installed in order to reduce percolated flow.
(f) Against ground water leaking upwards from the aquifer below the low-permeable layer, horizontal wells are installed into the lower aquifer in order to reduce ground water pressure.
(g) When the upper aquifer water level drops, there is a possibility that reactor building or turbine building accumulated water flows out, but this is addressed by the installation of a layer that waterproofs the ground around buildings.

Problems/feasibility:
Study to be continued.

zapperzero · May 21, 2013

tsutsuji said:

Translation :

Contaminated water quantity reduction countermeasures
[...]
Study to be continued.

Doesn't sound like there is even one decent geotechnical engineer on this committee, except for maybe that Nishikaki fellow.

Also, I see a revival of the proposal to grout the torus rooms. Not good.

tsutsuji · May 25, 2013

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130524/0430_iaea.html The IAEA released its report on 23 May in conclusion of its last inspection. They provide 17 pieces of advice. In one of them they say that instead of trying to bring the site back to how it was before building the plant, as technological and cost questions are remaining, they advise to to bring proposals as regards the final picture of the site, so that it can feed public discussion on the consequences on the surrounding society and the technical choices. They also advise to discuss the radioactive waste disposal solutions, because they fear that an absence of solution could have a negative impact on the work at the plant. They also advise to study the separation of the decommissioning function and the safety-sensitive equipment operating function. Tepco and the government said the IAEA's remarks would be reflected in next month's planning schedule.

http://www.iaea.org/newscenter/focus/fukushima/missionreport230513.pdf IAEA report (57 pages, English)

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130524/index.html The NRA approved the launching in mid-June of the hot tests of the 2nd and 3rd lines of the multinuclide removal facility (ALPS). At an expert panel meeting on 24 May, Tepco provided a report saying that the hot test of the first line, that was launched at the end of March, is going smoothly. The facility's normal operation should start next autumn. The facility's launching incurred a long delay after it had been found that the waste containers were not strong enough. Each of the 3 lines can process 250 tons per day, while 400 tons of contaminated water are generated every day at Fukushima Daiichi.

tsutsuji · May 25, 2013

The 11th special atomic facility monitoring and assessment group meeting ( http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/20130524.html ), 24 May 2013

http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_99.pdf Agenda
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_01.pdf Start of B and C lines of multinuclide removal facility
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_02.pdf Special atomic facility operation plan review
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_03.pdf Reply to "Risks at Fukushima Daiichi" (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_04.pdf Underground water storage tank leakage accident investigation results and investigation plan (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_05.pdf Answers to questions asked by the experts at the 10th meeting (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_06.pdf Special atomic facility operation plan review status

Reference :
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_07.pdf List of measures required following the special atomic facility designation of Fukushima Daiichi
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_08.pdf Opinions from the experts
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0011_09.pdf Multinuclide facility hot test (Tepco) (10th meeting document 2-1)

tsutsuji · May 25, 2013

The 10th special atomic facility monitoring and assessment group meeting ( http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/20130517.html ), 17 May 2013

http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_99.pdf Agenda
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_01.pdf Operation plan approval
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_02.pdf Multinuclide facility hot test status and future response (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_03.pdf Future progression of multinuclide facility hot test (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_04.pdf Replies to check items from the special atomic facility monitoring and assessment group (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_05.pdf Risk at Fukushima Daiichi
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_06.pdf Revision of the operation plan regarding the installation of premises entrance/exit management system (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_07.pdf Fukushima Daiichi accident analysis study group
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_08.pdf Underground water storage tank leakage accident present status and cause investigation report (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_09.pdf Revision of radiation releases at plant boundary taking into account the direct radiation and skyshine from tanks as a result of transferring the reverse osmosis concentrated water out of the underground tanks (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_10.pdf Replies to check items raised at the 9th meeting (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_11.pdf Maintaining integrity of contaminated water storage tanks (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_12.pdf Additional tank installation plan (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_13.pdf Contaminated water treatment countermeasure Committee study status (Agency for Natural Resources and Energy)

Reference :
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_14.pdf List of measures required following the special atomic facility designation of Fukushima Daiichi
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_15.pdf Partial revision of operation plan (Tepco)
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_16.pdf Opinion submitted by expert after the past meeting

tsutsuji · May 25, 2013

tsutsuji said:

The 10th special atomic facility monitoring and assessment group meeting
http://www.nsr.go.jp/committee/yuushikisya/tokutei_kanshi/data/0010_08.pdf Underground water storage tank leakage accident present status and cause investigation report (Tepco)

I had a look at the last page of this pdf (p. 28/28). I don't understand the details, but basically they want to test two scenarios in laboratory :

a) a crack in the concrete layer causes HDPE sheet break

b) an acute angle part in the concrete layer causes HDPE sheet break

Additional details on the timing of unit 1 IC valves :
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130510_09-e.pdf Progress of Investigation of the Accident and the Emergency Condenser at Unit 1 of Fukushima Daiichi Nuclear Power Station (English)

http://www.meti.go.jp/earthquake/nuclear/20130522_01.html The location where the mock-up facility (to test robots, etc.) is to be constructed was decided by the Countermeasure Promotion Conference on 25 May, after receiving a report on the results of geotechnical survey of candidate sites. The chosen site is in Naraha Town, close to Hirono Interchange, J-Village, and Hirono thermal power plant. (map on http://www.meti.go.jp/earthquake/nuclear/pdf/130522/130522_01c.pdf page 5/10)

http://www.youtube.com/watch?feature=player_detailpage&v=j3Qxf-8-QPw FNN news report on the mock-up facility. They plan to mock-up the torus room. It is planned to start operating in fiscal year 2014.

I_P · May 27, 2013

general questions about the status of accident knowledge

I haven't followed this thread for more than a year now and am curious if a clearer/consensus picture has emerged about the accident.

Is it understood how/why the explosion occurred in unit 4? Was it hydrogen migration through venting systems from unit 3?

Is it understood how much damage occurred before the tsunami? Were safety systems still functional? or were the plants already doomed? (perhaps this still cannot be answered with available information)

Did TEPCO succeed in performing physical/visual inspections of reactors 1,2,&3 to determine the state of the respective cores? Or is the current knowledge based primarily on modeling from available evidence?

I see preparations are underway to remove the spent fuel from the SFPs - I assume it will be stored on site?

What is the status of units 5&6?

etudiant · May 27, 2013

I_P said:

I haven't followed this thread for more than a year now and am curious if a clearer/consensus picture has emerged about the accident.What is the status of units 5&6?

Hi I_P,
You pose good questions without good answers.
Afaik, none of your questions has been clearly addressed, much less answered, in any of the official studies. Indeed, if it were not for the sterling work done by Tsutsuji-san on this site and by the nameless author of the EX-SKF web site, there would be no new information on Fukushima
in the English speaking world.
I believe that that is how the Japanese government, which effectively controls TEPCO since the bailout, prefers to handle matters. It is clear that lots is getting done at Fukushima and money is not really an obstacle, as the documents Tsutsuji-san has found and posted show. It is also clear that there is little interest in answers to your questions. It does not matter to Japan Inc. how these reactors failed in a once in a thousand years situation, as the export business of Japanese reactor know how has resumed. The public focus now is on cleaning up the site, an effort which appears to have all the earmarks of a perpetual project, where billions are spent doing nothing especially useful, much like Hanford in the US.

Units 5 and 6 are in long term standby. I believe they could be returned to service in very short order, as they were undamaged by the tsunami, but the Abe government has not had the will to allow their restart.

nikkkom · May 27, 2013

I_P said:

I haven't followed this thread for more than a year now and am curious if a clearer/consensus picture has emerged about the accident.

Is it understood how/why the explosion occurred in unit 4? Was it hydrogen migration through venting systems from unit 3?

Yes, it was hydrogen.

Is it understood how much damage occurred before the tsunami? Were safety systems still functional? or were the plants already doomed? (perhaps this still cannot be answered with available information)

There are no indications that serious damage occurred prior to tsunami. (If it did, then TEPCO so far managed to hide that evidence).

Did TEPCO succeed in performing physical/visual inspections of reactors 1,2,&3 to determine the state of the respective cores?

No. Even PCVs aren't satisfactorily inspected yet.

What is the status of units 5&6?

Technically they are fine. It will be politically difficult to allow their restart.

I_P · May 28, 2013

Thanks etudiant and nikkkom, I have had a chance to browse the last 50 pages or so and have a better sense of the state of things. Seems that the consensus is that the Unit 4 SFP was never a problem so by default the assumption is that the explosion in that unit was fueled by hydrogen from Unit 3 via the shared vent stack plumbing.

I also noted some discussion suggesting that the elevated radiation levels between March 21st and 23rd were possibly associated with reactor core melting through the pressure vessel - maybe in Unit 3?

http://http://www.ltrr.arizona.edu/~cbaisan/BBTRB/Ibaraki_rad.jpg

{tried to embed an image here - maybe over a size limit...}

zapperzero · May 30, 2013

nikkkom said:

There are no indications that serious damage occurred prior to tsunami. (If it did, then TEPCO so far managed to hide that evidence).

This is not true. There are reports of significant radioactive release(s) before the tsunami.

zapperzero · May 30, 2013

I_P said:

Seems that the consensus is that the Unit 4 SFP was never a problem

I'm not part of that consensus. Water is supposed to be self shielding and so only gamma radiolysis yields are taken into account; no-one has seriously addressed the possibility of localized boiling on the surface of fuel elements which would have increased H2 production as lots of beta radiolysis would also take place.

I_P · May 30, 2013

This paper discusses remelting of the core material following water injection: Analyses of core melt and re-melt in the Fukushima Daiichi nuclear reactors by Fumiya Tanabe, Journal of Nuclear Science and Technology
Volume 49, No. 1, January (2012) pp. 18–36. Has there been modeling of the radioactive releases based on this scenario?

zapperzero - understood. Did they succeed in moving more than the two unused elements from the pool? (I should go back and read Tsutsuji's latest update)

I_P · May 30, 2013

managed a double post. Many aspects will likely remain forever murky/unresolved I am sure.

turi · May 30, 2013

I_P said:

Did they succeed in moving more than the two unused elements from the pool? (I should go back and read Tsutsuji's latest update)

No, they didn't plan to. They've just finished building the steel frame for fuel removal:
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130529_08-e.pdf
Now they will have to install machinery for fuel removel.

zapperzero · May 31, 2013

I_P said:

This paper discusses remelting of the core material following water injection: Analyses of core melt and re-melt in the Fukushima Daiichi nuclear reactors by Fumiya Tanabe, Journal of Nuclear Science and Technology
Volume 49, No. 1, January (2012) pp. 18–36. Has there been modeling of the radioactive releases based on this scenario?)

http://www.tandfonline.com/doi/full/10.1080/18811248.2011.636537#.UahvrJxaeEo

tsutsuji · May 31, 2013

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130530/0510_kiseicho.html The NRA is starting an inspection on 30 May to investigate accident causes. They will go to unit 1 and check the circumstances of a water leak that had been reported by an employee before the tsunami struck, and whose cause remains unknown. Because of radiations, the inspection on unit 1's 4th floor, to be performed by 5 Nuclear Regulation Agency employees on 31 May will be limited to about 10 minutes. On May 1st they held their first meeting and discussed the possibility that earthquake damage took place in a unit 1 cooling system. The purpose of the inspection is to check the validity of the explanation that water from the pool flowed into the air conditioning system, by looking for equipment damage. The second meeting will be held in the beginning of June.http://www3.nhk.or.jp/nhkworld/english/news/20130530_40.html Frozen wall mooted to stop Fukushima groundwater

Panel members made the proposal at a meeting on Thursday. They have discussed new measures against groundwater since April when leaks were found in underground storage pools for contaminated water.

The panel urged plant operator Tokyo Electric Power Company to freeze the ground around the buildings of 4 reactors in order to create a shielding wall.

Panel members said TEPCO should implement the measure by the middle of fiscal 2015.

Members also urged TEPCO to pump up groundwater from surrounding wells and release it into the ocean.

The measures are aimed at gradually reducing the flow of groundwater and stopping it within 8 years.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130530/0510_kiseicho.html But the fishermen are resisting groundwater releases into the Ocean, so that there is no prospect of starting those releases.

tsutsuji · May 31, 2013

Contaminated water treatment countermeasure committee, 3rd meeting, 30 May 2013 ( http://www.meti.go.jp/earthquake/nuclear/20130531_01.html )

http://www.meti.go.jp/earthquake/nuclear/pdf/130531/130531_01a.pdf Agenda
http://www.meti.go.jp/earthquake/nuclear/pdf/130531/130531_01b.pdf Participants
http://www.meti.go.jp/earthquake/nuclear/pdf/130531/130531_01c.pdf Countermeasures to refrain groundwater inflow
http://www.meti.go.jp/earthquake/nuclear/pdf/130531/130531_01d.pdf Views on the Contaminated water treatment countermeasure committee's report (by the NRA)
http://www.meti.go.jp/earthquake/nuclear/pdf/130531/130531_01e.pdf Reference

tsutsuji · May 31, 2013

Fukushima Daiichi accident analysis study group 1st meeting, 1 May 2013 ( http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/20130501.html )

http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/data/0001_99.pdf Agenda
http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/data/0001_01.pdf About the study group
http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/data/0001_02.pdf Future progression method for Fukushima Daiichi accident analysis (draft)
http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/data/0001_03.pdf List of problems needing to be studied as raised by each accident investigation report, etc.
http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/data/0001_04.pdf Unit 1 reactor building water outflow
http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/data/0001_05.pdf Hydrogen source of unit 4 hydrogen explosion

http://www.tepco.co.jp/tepconews/library/movie-01j.html?bcpid=45149870002&bclid=347241149002&bctid=445953600002 Video taken on 28 March 2013 on unit 1's 4th floor (Tepco website)

tsutsuji · May 31, 2013

tsutsuji said:

Fukushima Daiichi accident analysis study group 1st meeting, 1 May 2013
http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/data/0001_04.pdf Unit 1 reactor building water outflow

Page 4 quotes the Diet investigation report, 2-2-4 b), whose English translation is available at: http://warp.da.ndl.go.jp/info:ndljp...nt/uploads/2012/08/NAIIC_Eng_Chapter2_web.pdf page 81/97

b. The cause of the gushing water has yet to be identified

On the fifth floor, the very top of the spent fuel pool was exposed. There is a possibility that the origin of the gushing water was overflow from the spent fuel pool. It is estimated that the pool water was shaken strongly by the earthquake (causing sloshing) and overflowed onto the floor, spilling to the fourth floor.[157] It is possible that the water spilled from the fifth floor to the fourth floor through the opening in the floor, but this contradicts with B’s narrative. He stated that he was standing almost right below the opening and that the water that came gushing through was from his right.

As there are many ventilation openings at the top of the wall of the spent fuel pool, it is possible that the water overflowed into the ventilation openings to the exhaust duct and to the fourth floor.

As stated in 2.2.4 2, the issue of whether the IC piping was damaged by the earthquake movement has been raised numerous times. There is a complex IC piping system on the fourth floor of the nuclear reactor building where the gushing water was witnessed, and part of it extends close to the spot. Thus NAIIC informed TEPCO that, in spite of the risk of being exposed to a certain level of radiation, NAIIC wanted to conduct an on-site inspection of the fourth floor (TEPCO was not told the purpose of the inspection).

Entering the reactor building for inspection is incredibly dangerous, as the interior of the building is pitch dark even in daytime due to the lack of lighting, wreckage from the hydrogen explosion is everywhere, and there are large openings for moving equipment in each floor. TEPCO informed NAIIC that, because accompanying NAIIC members into the building would subject their workers to unnecessary radiation exposure, TEPCO personnel would not enter the building. After much consideration, NAIIC gave up on the idea of investigating the interior of the nuclear reactor building.

So at this point, the only conclusion that NAIIC can come to is that immediately after the earthquake, there was a gush of water near the southern wall of the fourth floor of the nuclear reactor building of Unit 1 that TEPCO and NISA need to thoroughly investigate.

TEPCO must have been aware that there were subcontracted workers working there at the time of the earthquake, and the TEPCO Fukushima Nuclear Accidents Investigation Committee should have immediately interviewed the workers.[158] But workers A and B stated that they had not been interviewed by TEPCO prior to NAIIC’s interview with them about gushing water.[159]

I_P · May 31, 2013

Thanks zapperzero, I had read through the paper but not focused on their look at the radiation releases. I tried to post a jpg above of a set of monitoring data from 3/15-3/24 but it doesn't load up - about 5mb in size. More specifically, I was interested in whether the core re-melt scenario would change the overall estimates of radioactive releases that were done following the accident.

Tsutsuji, thanks for your posts. I am interested in a rough translation of "hydrogen source of unit 4 explosion" and "List of problems needing to be studied as raised by each accident investigation report, etc." if you find the time.

tsutsuji · Jun 3, 2013

I_P said:

I am interested in a rough translation of "hydrogen source of unit 4 explosion" and "List of problems needing to be studied as raised by each accident investigation report, etc." if you find the time.

First of all, I translate the first page of "List of problems needing to be studied as raised by each accident investigation report, etc.". The table on the following pages provides relevant excerpts or summarizes the Diet investigation report (middle column) and Cabinet investigation report (right column).

http://www.nsr.go.jp/committee/yuushikisya/jiko_bunseki/data/0001_03.pdf page 1/16

A) Possibility of earthquake-caused equipment/machinery and piping damage

(1) Possibility of LOCA (except IC piping)
Possibility of small scale LOCA through minute piping cracks
Possibility that unit 1 SR valve did not function

(2) Possibility of IC piping damage
Water outflow inside unit 1 reactor building
Possibility that it was not the noise from the IC
Cause of IC manual shutdown

(3) Possibility of unit 1 DG A damage
Unit 1 system A diesel generator shutdown timing

(4) Earthquake response analysis problem caused by measurement recording
Variations of the plant premises geological characteristics along the north-south direction
The fact that onsite surveys were performed considering that unit 5 is the representative unit
Existence or absence of reinforcement works to enhance earthquake resistance

B) PCV pressure rise

(5) PCV pressure rise
Possibility of earthquake-caused pipe damage and small scale LOCA

(6) Sloshing-caused PCV pressure rise
Possibility of downcomer exposure caused by the shaking of the suppression chamber water surface

C) Hydrogen explosions

(7) Assessment of core-concrete interaction consequences
Possibility of unit 1 core-concrete interaction
Possibility of unit 3 core-concrete interaction

(8) Hydrogen source of unit 4 hydrogen explosion
Hydrogen quantity generated by unit 3 backflow
Hydrogen quantity generated at unit 4 SFP

(9) Hydrogen explosion ignition factors
Possibility of metallic friction, electric fault, etc.

D) Units 1,2,3 machinery and equipment damage

(10) Unit 1 IC loss of function
Valve open/closed status

(11) Unit 2 suppression chamber pressure gauge breakdown
Possibility of PCV damage
Possibility of electric system trouble

(12) Unit 3 RCIC shutdown
Possibility of steam stop valve mechanical component trouble

E) Other

(13) Possibility of unit 3 recriticality
Cause of the hydrogen generation that was confirmed after the hydrogen explosion

(14) PCV damage caused by hydraulic dynamic load
Possibility of damage caused by localized dynamic load generated together with suppression chamber steam releases, etc.

(15) RPV damage locations after tsunami

(16) PCV damage locations after tsunami

nikkkom · Jun 3, 2013

zapperzero said:

This is not true. There are reports of significant radioactive release(s) before the tsunami.

Define "significant".

nikkkom · Jun 3, 2013

zapperzero said:

I'm not part of that consensus. Water is supposed to be self shielding and so only gamma radiolysis yields are taken into account; no-one has seriously addressed the possibility of localized boiling on the surface of fuel elements which would have increased H2 production as lots of beta radiolysis would also take place.

Betas do not penetrate fuel cladding.

zapperzero · Jun 4, 2013

nikkkom said:

Betas do not penetrate fuel cladding.

So, in your considered opinion spent fuel rods do not give off beta?

nikkkom · Jun 4, 2013

zapperzero said:

So, in your considered opinion spent fuel rods do not give off beta?

Spent fuel rods certainly emit beta particles.
Even my desk emits beta particles.
I probably need to run away in terror?

zapperzero · Jun 4, 2013

nikkkom said:

Spent fuel rods certainly emit beta particles.
Even my desk emits beta particles.
I probably need to run away in terror?

You probably need to educate yourself a bit (just how many beta particles? what yields?) and maybe just maybe consider a change of tonality. This one is rather grating.

Japan Earthquake: Nuclear Plants at Fukushima Daiichi

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