Japan Earthquake: Nuclear Plants at Fukushima Daiichi

AI Thread Summary
The Fukushima Daiichi nuclear plant is facing significant challenges following the earthquake, with reports indicating that reactor pressure has reached dangerous levels, potentially 2.1 times capacity. TEPCO has lost control of pressure at a second unit, raising concerns about safety and management accountability. The reactor is currently off but continues to produce decay heat, necessitating cooling to prevent a meltdown. There are conflicting reports about an explosion, with indications that it may have originated from a buildup of hydrogen around the containment vessel. The situation remains serious, and TEPCO plans to flood the containment vessel with seawater as a cooling measure.
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Engineering news on Phys.org
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OT:
Please take opportunity to vote for tsutsuji on this https://www.physicsforums.com/showthread.php?t=656505.
Thanks!

P.S.:
You also could vote for Jim Hardy. But, I believe that Old Jim probably will be okay with tsutsuji being elected...
 
  • #13,803
http://www.tepco.co.jp/index-j.html At 17:18 on 7 December an intensity 4 [JMA scale] earthquake occurred on the Hamadori region (the coastal region) of Fukushima prefecture.

Fukushima Daiichi : concerning all monitoring post values, units 1,2,3,4,5,6 plant parameters, reactor water injection facilities, accumulated water transportation facilities, water treatment equipments, no abnormality was found. Personnel injury was not reported. The largest acceleration was the one measured at unit 6 with 26.2 gal (horizontal direction).Fukushima Daini : maximum value 26.0 gal (vertical direction).

http://www.jiji.com/jc/c?g=soc_30&k=2012120700686 A 1 m high tsunami was measured at Ishinomaki (Miyagi prefecture) at 18:02 on 7 December 2012. The workers at Fukushima Daiichi have taken shelter in elevated places away from the sea.
 
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  • #13,804
Thanks Tepconium... indeed that's so.
 
  • #13,805
The 12th mid & long term meeting was held on 3 December 2012: http://www.meti.go.jp/earthquake/nuclear/20121203_02.html

1) Previous related topics:

12th meeting English roadmap http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/images/m121203-e.pdf

The 11th meeting (22 October 2012) https://www.physicsforums.com/showpost.php?p=4127659&postcount=13788

11th meeting English roadmap : http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/images/t121022_01-e.pdf and http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/images/m121022-e.pdf

The 10th meeting (24 September 2012) https://www.physicsforums.com/showpost.php?p=4096335&postcount=13735

The 9th meeting (27 August 2012) https://www.physicsforums.com/showpost.php?p=4051034&postcount=13635

The 8th meeting (30 July 2012) https://www.physicsforums.com/showpost.php?p=4020743&postcount=13588

The 7th meeting (25 June 2012) https://www.physicsforums.com/showpost.php?p=3979794&postcount=13512

The 6th meeting (25 May 2012) : https://www.physicsforums.com/showpost.php?p=3933442&postcount=13399

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) was translated into English on Tepco's website : http://www.tepco.co.jp/en/nu/fukushima-np/roadmap/conference-e.html

2) Translation:

3 December 2012 government-Tokyo Electric mid and long term response committee, steering committee (11th meeting)

http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02a.pdf Agenda
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02b.pdf Participants

Document 1
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02c.pdf Abstract of the proceedings of 11th steering committee meeting

Document 2: Plant status
Document 2-1: Plant status
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02d.pdf Plant parameters
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_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/121203/121203_02f.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02g.pdf Condensate Storage Tank (CST) water injection (into reactor) system installation work : scope and schedule revisions
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02h.pdf Results of nitrogen injection into unit 1 suppression chamber
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02j.pdf Results of checking the status of unit 3 PCV gas management system ducts
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02k.pdf Change of pressure-resistant hoses into polyethylene ones

3-2 Treatment of accumulated water
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02m.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02n.pdf Ground water bypass implementation status
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02p.pdf Responses toward the start of the multinuclide removal facility (ALPS)'s hot test

3-3 Countermeasures to reduce environmental radiations
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02q.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02r.pdf Countermeasures to reduce harbour seawater concentrations (November)
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02s.pdf Reduction of harbour seawater concentrations (survey plan)
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02t.pdf Silt fence replacement work in front of unit 3 screen chamber
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02u.pdf Results of evaluation of additional releases from reactor buildings

3-4 Improvement of working conditions
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02v.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02w.pdf Fiscal 2012 heatstroke prevention countermeasure implementation status
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02x.pdf Infectious disease prevention and contagion prevention countermeasures
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02y.pdf Questionnaire survey on the actual labour conditions
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02z.pdf Entrance and departure management facilities completion schedule change

3-5 Countermeasures for spent fuels pools
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02aa.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02bb.pdf Spent fuel pool countermeasure schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02cc.pdf Debris removal work, reactor building top part, unit 3
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02dd.pdf Debris removal work, reactor building top part, unit 4
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02ee.pdf Schedule of fuel removal from unit 4 spent fuel pool
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02ff.pdf Outline of cover structure for unit 3 fuel removal
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02gg.pdf Results of periodical inspection for the purpose of checking the soundness of unit 4 reactor building
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02hh.pdf Unit 1 operation floor re-inspection results

3-6 Preparations for fuel debris removal
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02jj.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02kk.pdf Plan to inspect the surroundings of unit 2 vent pipe lower parts

3-7 Treatment and disposal of radioactive waste
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02mm.pdf Schedule
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02nn.pdf Debris, cut down trees management status
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02pp.pdf progress status of temporary storage by means of covering with soil

Document 4
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02qq.pdf Program decided within the implementation plan specified by the Special Nuclear Power Facility status

Document 5
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02rr.pdf Mid and long term roadmap progress status (abstract)

Document 6
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02ss.pdf Mid and long term roadmap progress status and future problems

Document 7
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_02tt.pdf Mid and long term roadmap seminar (to be held in Fukushima City on 19 December 2012)

3 December 2012 government-Tokyo Electric mid and long term response committee, technical development progress headquarters (11th meeting) ( http://www.meti.go.jp/earthquake/nuclear/20121203_03.html )

http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_03a.pdf Agenda

Document 1
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_03b.pdf Abstract of proceedings of 10th meeting (draft)

Document 2-1
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_03c.pdf Fiscal 2013 research and development plan (draft)
Document 2-2
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_03d.pdf Fiscal 2013 executive plan of research and development toward decommissionning of nuclear energy facilities (draft)

Document 3
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_03e.pdf Practical use of national and international knowledge in accident progression analysis (OECD-NEA BSAF project)

Document 4
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_03f.pdf Initiative toward the determination of the research and development plan for treatment and disposal of radioactive waste (draft)

Document 5
http://www.meti.go.jp/earthquake/nuclear/pdf/121203/121203_03g.pdf Invitation to the Fukushima workshop on machinery and equipments, etc. toward the decommissionning (draft) (to be held in Fukushima City on 19 December 2012)
 
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Here's a slide presentation on the explosions of Units 1 and 3 by the Japan Nuclear Energy Safety Organization, presented on September 17, 2012 at the IAEA General Conference:

http://www.aec.go.jp/jicst/NC/sitemap/pdf/P-4.pdf

They opine that the Unit 3 explosion propagated upwards from a hydrogen release on the 1st floor. Apparently the force of the explosion increased significantly over time, doing very little damage to lower floors but growing so strong that by the time it reached the 5th floor it annihilated that top floor.

The slide presentation says:

Major Assumptions:

• In Unit 1, Hydrogen of 400 kg was released to
the top floor (5F) of reactor building (R/B) and
ignited there.

• In Unit 3, Hydrogen of 1000kg was released to
the first floor (1F) of R/B and ignited there.


img_224-Dec.-17-16.05.jpg
 
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  • #13,808
SpunkyMonkey said:
They opine that the Unit 3 explosion propagated upwards from a hydrogen release on the 1st floor. Apparently the force of the explosion increased significantly over time, doing very little damage to lower floors but growing so strong that by the time it reached the 5th floor it annihilated that top floor.

So, they are contending that hydrogen escaped via the equipment hatch, diffused into the entire building, then ignited somehow there, on the bottom floor and managed to only blow out the roof and top floor?

No. There would be crushed piping, debris and such at all levels.

EDIT: in unrelated news I am quite pleased with myself, as their estimate of H2 quantities agrees with my own BOE calcs :D
 
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http://www3.nhk.or.jp/news/genpatsu-fukushima/20121220/index.html On 20 December 2012, the 7 m long, 470 kg heavy steel beam that had fallen into unit 3 SFP in September was lifted out of the pool. Tepco says that the beam was caught with other debris, and was possibly bearing consequences on the debris removal work. The debris removal work was planned to be completed by March 2013, but it is feared that the beam falling event might have caused a delay from the schedule.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_121220_02-e.pdf Debris Removal from the Upper Part of Unit 3 Reactor Building at Fukushima Daiichi Nuclear Power Station: Removal of the Steel Beam Which Fell into the Pool
 
  • #13,810
http://www.tepco.co.jp/nu/fukushima-np/roadmap/conference-j.html The 13th mid-long term meeting was held on 25 December 2012 [but the pdf presentations are not available at http://www.meti.go.jp/earthquake/nuclear/decommissioning.html yet]

http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/m121225_05-j.pdf There is something new about the plan to use the TIP guide tubes for installing alternative thermometers in unit 2. Some work for this was started on 20 December. There is a plan to inject nitrogen into unit 2 suppression chamber like they did at unit 1. There is a High Integrity Container (HIC) falling test. There is some more about the plan to close unit 2's blowout panel. There is something on unit 3's debris removal work.
 
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http://www.japantimes.co.jp/text/nn20130101a3.html

The CMRT, consisting of 33 scientists and engineers, arrived at Yokota Air Base on March 16 from Nellis Air Force Base in Las Vegas and initiated test flights within 12 hours of arriving, according to an NNSA senior official. The CMRT conducted the first round of AMS operations from March 17 to 19, using two U.S. military aircraft.

The AMS flight operations over Fukushima were conducted around 100 times totaling 525 flight hours until the CMRT left Japan on May 28, 2011, an NNSA official said.

It would be really nice if some US citizen could do a FOIA request for those flight records and the test data... I am pretty sure that there are/were reporters lurking in this thread. Perhaps we would then learn more about the timing of radioactive releases.
 
  • #13,812
zapperzero said:
http://www.japantimes.co.jp/text/nn20130101a3.html



It would be really nice if some US citizen could do a FOIA request for those flight records and the test data... I am pretty sure that there are/were reporters lurking in this thread. Perhaps we would then learn more about the timing of radioactive releases.

I'm not a reporter, but I've looked at the NNSA data available here:

http://www.nnsaresponsedata.net/

There's a lot there, maybe what you're looking for. It requires a registration, but that took only about 2 hour to turn around.
 
  • #13,816
Astronuc said:
Better images are available

Actually I was trying to post a video of a Unit 1 walkthrough... don't know what happened to the link.
EDIT: third one down on the right side, same page. Can't be bothered to figure how to link directly to it... I'll put it on Mega or something later.

LATER EDIT:
here it is
 
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  • #13,817
That's the tepco link you were looking for:
http://photo.tepco.co.jp/en/date/2013/201302-e/130207-01e.html

Quite intriguing video from October 18, 2011. Quite a bit of noise. My limited Japanese knowledge picked up things like "xyz milli" presumably being the current mSv/h (or possibly the accumulated dose in mSv, I didn't pay enough attention to the numbers), readings from sensors ("kochira zero desu": "This one is zero"), things like "daijoubu desu ne" (good, ain't it) and "ikimashou, ikimashou" (let's go, let's go) when the radiation alert goes off (I think it goes off because they have reached a preliminarily set maximum accumulated dose as it goes of at a place where they have been before).

Can anyone with more knowledge of Japanese and the daichi reactors shed some light on what they were inspecting up there in unit 1?
 
  • #13,818
turi said:
That's the tepco link you were looking for:
no, it is not. that's a much older video
 
  • #13,819
no, it is not. that's a much older video
Hm, it the same as the one you've uploaded to mega and has been released on February 6 this year.

There's now also a video been released yesterday from the same place but recorded in November 2012. Much better video quality. They even look at some of the same instruments.
http://photo.tepco.co.jp/en/date/2013/201302-e/130215-01e.html
 
  • #13,820
turi said:
Hm, it the same as the one you've uploaded to mega and has been released on February 6 this year.

Okay. I stand corrected. Thanks for the further link.
 
  • #13,821
Will Davis over at Atomic Power Review has updated his site to include a section on the Fukushima accident.

http://atomicpowerreview.blogspot.com/p/fukushima-daiichi-accident-reports.html



One report that caught my eye was the one from Sandia National Labs, which I don't remember seeing before. Apologies if it has been posted here previously.

http://energy.sandia.gov/wp/wp-content/gallery/uploads/Fukushima_SAND2012-6173.pdf
 
  • #13,822
LabratSR said:
Will Davis over at Atomic Power Review has updated his site to include a section on the Fukushima accident.

http://atomicpowerreview.blogspot.com/p/fukushima-daiichi-accident-reports.html



One report that caught my eye was the one from Sandia National Labs, which I don't remember seeing before. Apologies if it has been posted here previously.

http://energy.sandia.gov/wp/wp-content/gallery/uploads/Fukushima_SAND2012-6173.pdf

The conclusions are highly suspect, imho. How can anyone say that a model is accurate when the actual sequence of events remains unknown?
 
  • #13,823
zapperzero said:
The conclusions are highly suspect, imho. How can anyone say that a model is accurate when the actual sequence of events remains unknown?

If you read the Abstract of the Sandia report you will find that the model was developed to validate the MELCOR code and its ability to investigate a severe reactor accident. The results were not presented as a final analysis or truth of what actually happened. As you point out there are many things we don't know about the exact timeline, but the process of scientific inquiry does not require us to know everything to at least try to begin learning what happened. If we knew everything already we wouldn't need to model the accidents.

The models tell us what might have happened. Data from the model can be used to focus investigation where the results don't match the reality. It can be used to at least estimate the conditions to be encountered during cleanup. If they find new data the models can be updated and help refine the story. This will be ongoing for years.

Maybe this will help. The Wright Brothers built an airplane with rudimentary scientific inputs. Today's Aeronautical Engineers have far superior knowledge of why airplanes can fly. And the old story is that all that scientific modelling tells us that a bumblebee shouldn't be able to fly. Luckily, bumblebees can't read.
 
  • #13,824
NUCENG said:
If you read the Abstract of the Sandia report you will find that the model was developed to validate the MELCOR code and its ability to investigate a severe reactor accident. The results were not presented as a final analysis or truth of what actually happened. As you point out there are many things we don't know about the exact timeline, but the process of scientific inquiry does not require us to know everything to at least try to begin learning what happened. If we knew everything already we wouldn't need to model the accidents.

The paper goes on to conclude that MELCOR is one hell of a code and the model as built is an excellent model, because after tweaking the input data some of the simulation results start to resemble plant readings. This is not very good science, I think.
Overall, these results increase confidence in the MELCOR code; establish confidence in the
Fukushima reactor models and spent fuel pool model; and demonstrate that the code and models
are valid for their intended use. They also add more evidence to the existing body of results that,
when taken has a whole, build confidence in the validity of the MELCOR code.
Also, I think we'd still need to model the accidents; I believe that the most important use of models is not forensic, but predictive.

In other, unrelated news the word "radiolysis" is conspicuously absent from this document...
 
  • #13,825
zapperzero said:
In other, unrelated news the word "radiolysis" is conspicuously absent from this document...
Do you have any indication that radiolysis would be a significant source of hydrogen compared to zirconium, steel and B4C steam oxidation? Those three sources are modeled in the analysis.
 
  • #13,826
turi said:
Do you have any indication that radiolysis would be a significant source of hydrogen compared to zirconium, steel and B4C steam oxidation? Those three sources are modeled in the analysis.

Where did the hydrogen in Unit 4 come from? We're told it went into the unit 3 SGTS from the torus room, then instead of going up the stack it traveled through the vent pipe into unit 4, where it exploded... 19 hours after Unit 3 itself went up.

I have provided elsewhere here citations of research into steam radiolysis. Apparently it is much more efficient than water radiolysis. My idea, and it is nothing more than an idea as I obviously can't run experiments of any kind and I don't even have access to the relevant simulation codes, is that localized bubbling on the surface of fuel elements in the spent fuel pool (where water was no longer circulated by pump, only by convection) might have created the conditions for the production of a sufficient amount of hydrogen.
 
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  • #13,828
LabratSR said:
From Atomic Power Review.

Major New Report released by TEPCO.

http://www-pub.iaea.org/iaeameetings/IEM4/30Jan/Suzuki_d.pdf

Took a quick look. The bit about shortening the cooling loops is rather interesting, as is the fact that currently the cooling water is only being scrubbed of cesium.

I kinda stared a little at the picture of workers in street clothes... apparently air dose rates at site boundary (as measured by shielded detectors in decontaminated locations) are a good indicator of the overall contamination level of the site.
 
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  • #13,829
  • #13,830
zapperzero said:
I have provided elsewhere here citations of research into steam radiolysis. Apparently it is much more efficient than water radiolysis. .
But then it would be hydrogen only on the 5th floor.
However, the explosion was also on 4 and 3 floors.
 
  • #13,831
a.ua. said:
But then it would be hydrogen only on the 5th floor.
However, the explosion was also on 4 and 3 floors.

You seem a bit confused. There is no simple way to tell where the hydrogen was and wasn't - you can only see the damage caused by the blast (which does indeed extend downwards as well as outwards).
 
  • #13,832
After taking a closer look at the Sandia National Labs report, I found a link inside it to an information portal established at Idaho National Labs.

https://fukushima.inl.gov/

From there, click the "Public" link and you can get access to other stuff such as this report.

https://fukushima.inl.gov/PDF/FDASIP-Ver-6.pdf
 
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  • #13,833
From the INL portal.


"Enhanced Ex-Vessel Analysis for Fukushima Daiichi Unit 1:
Melt Spreading and Core-Concrete Interaction Analyses with MELTSPREAD and CORQUENCH"

https://fukushima.inl.gov/PDF/MELTSPREAD%20CORQUENCH%20Analysis%201F1%20ORNL_ANL%20Feb2013.pdf
 
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  • #13,836
Joffan said:
Through the faint haze of translation, this seems like an excellent internal response from Tepco.

Excellent, you say. Have you read it? There's a lot of pious noise and nothing BUT reactive measures, based solely on what happened in this particular accident. They are preparing to weather another tsunami, not to improve safety overall. The next accident will again be a surprise that no-one could have predicted. Maybe a crane will make a nest in their new autocatalytic recombiner.

We thought it would have been difficult to explain that the current nuclear power station was completely safe if we had recognized that measures for handling severe accidents were necessary

So now it will be easy to explain that the NPPs are completely safe?
 
  • #13,837
zapperzero said:
Excellent, you say. Have you read it? There's a lot of pious noise and nothing BUT reactive measures, based solely on what happened in this particular accident. They are preparing to weather another tsunami, not to improve safety overall. The next accident will again be a surprise that no-one could have predicted. Maybe a crane will make a nest in their new autocatalytic recombiner.



So now it will be easy to explain that the NPPs are completely safe?


Ok Zap, You have SO honed in on EXACTLY my problem. No two incidents EVER happen the same. They are concentrating on the last accident instead of the NEXT. BULLSEYE.
 
  • #13,838
zapperzero said:
Excellent, you say. Have you read it? There's a lot of pious noise and nothing BUT reactive measures, based solely on what happened in this particular accident. They are preparing to weather another tsunami, not to improve safety overall. The next accident will again be a surprise that no-one could have predicted. Maybe a crane will make a nest in their new autocatalytic recombiner.

Well to be fair, they do divide the response into two parts: "Direct measures based on [...] Accident" and "Measures to structural problems[...]". It's from the latter where one would expect to see changes in the safety culture of the company and new risk assessments. But it would be equally stupid not to learn the direct lessons from the accident. Especially as those direct lessons (spare high pressure pumps, better means to bring in external power and coolant supplies, more resilient power supply, more redundancy in lighting and communication...) can help if something completely different than a tsunami occurs.
 
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  • #13,839
The objective is in simplest terms to move decay heat to a heat sink.

A. The science of that is not so difficult - reliable pumps and reliable power for them.


B. Human nature is complex. To get a committee(or a group of committees) to agree on how to go about achieving A is daunting.

That the TEPCO report speaks to both is positive IMHO.
 
  • #13,840
The NHK has another surprising story, dated 10 March 2013 :

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130310/index.html : As specialists had suggested that part of the water injected by fire-engine had leaked somewhere, the NHK procured by itself the unit 3 piping drawings and conducted a detailed analysis together with some specialists.

As a result, it was found that there is a byroad starting between the fire-engine and the reactor, and there is a possibility that water runs through the byroad and leaks into another device which is not the reactor.

At the end of the byroad, there is a device called "condenser" which is used to generate electricity and transforms steam back into water. Normally, the pump that is located there on the way, is running, so that the water is kept back, so that it does not flow into the condenser.

However, as we tested in an experiment with the help of the specialists, it was found that in the case where the pump is down, the water flows through without stopping, and there is a high probability that the water leaked during the Fukushima accident as all electric power had been lost.

This experiment result is corroborated by a press conference held by Tepco immediately after the accident, where Tepco indicated that at that time, unit 3's condenser was in a full-of-water status which cannot happen in normal time.

Furthermore, when unit 3's water flow generated by fire-engine injection is experimentally reconstructed and when that experimental result in used by specialists in a simulation, they find that 55% of the water volume leaks out instead of being injected into the reactor, and they conclude that this leaked amount is sufficient to explain why the meltdown could not be averted.

On the other hand, they conclude that if the leaked amount had been 25% or less, the meltdown could have been averted.

After the accident, fire-engines have been installed as a safety measure at every nuclear power plant in the country, but more than two years after the accident, what is emerging is that sufficient verifications have not been carried out about how certain it is that the water will enter the reactor.

According to Hosei University visiting professor Hiroshi Miyano, "the job is not finished after fire-pumps are installed, and it is meaningless if one does not check if a sufficient amount of water for cooling the nuclear fuel is coming into the reactor. The verifications made after the accident have not been sufficient."

http://www3.nhk.or.jp/daily/english/20130310_28.html (NHK World English version)
 
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  • #13,841
tsutsuji said:
The NHK has another surprising story, dated 10 March 2013 :

http://www3.nhk.or.jp/news/genpatsu-fukushima/20130310/index.html : As specialists had suggested that part of the water injected by fire-engine had leaked somewhere, the NHK procured by itself the unit 3 piping drawings and conducted a detailed analysis together with some specialists.

As a result, it was found that there is a byroad starting between the fire-engine and the reactor, and there is a possibility that water runs through the byroad and leaks into another device which is not the reactor.

At the end of the byroad, there is a device called "condenser" which is used to generate electricity and transforms steam back into water. Normally, the pump that is located there on the way, is running, so that the water is kept back, so that it does not flow into the condenser.

However, as we tested in an experiment with the help of the specialists, it was found that in the case where the pump is down, the water flows through without stopping, and there is a high probability that the water leaked during the Fukushima accident as all electric power had been lost.

According to Hosei University visiting professor Hiroshi Miyano, "the job is not finished after fire-pumps are installed, and it is meaningless if one does not check if a sufficient amount of water for cooling the nuclear fuel is coming into the reactor. The verifications made after the accident have not been sufficient."

http://www3.nhk.or.jp/daily/english/20130310_28.html (NHK World English version)

Welcome back, Tsutsuji-san, your insightful comments have been missed!

Once again, this report underlines the need for practical training.
Theoretical studies of what happens in the event of a complete power failure may miss major complexities in the real world system that only become apparent when actually exercised.
Is there any program in Japan to actively train operators to deal with such a complete station black-out contingency?
 
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  • #13,842
However, as we tested in an experiment with the help of the specialists, it was found that in the case where the pump is down, the water flows through without stopping, and there is a high probability that the water leaked during the Fukushima accident as all electric power had been lost.

Arrgh !
Usually there's a check valve at a pump discharge to prevent just that from happening..reverse flow when pump is off.
But check valves can stick partway open...

Big disasters are always a string of dominoes , little things individually until something pushes the first one over.
That's how "... the small thngs of the Earth confound the mighty".

Welcome back tsutsuji (finally i spelled it right ! )
 
  • #13,843
zapperzero said:
Excellent, you say. Have you read it? There's a lot of pious noise and nothing BUT reactive measures, based solely on what happened in this particular accident.

Sounds much better than response from almost every other country's nuclear industry, which 95% of the time boils down to "we checked our accident preparedness and it's just fine, we aren't like those stupid Japanese. Nothing needs to be done". Yeah right...
 
  • #13,844
Russian already invested tens of millions $ in the purchase of new mobile devices to transmit power and high-power pumps.
In Ukraine, not so well (we have less money), but the technique is bought .
And the most important exercise and a good knowledge of their own nuclear power plant.
 
  • #13,845
IRSN explaining the accident:



Nothing new, but everything already uncovered neatly packed together with animations. :)
 
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  • #13,846
http://www3.nhk.or.jp/news/genpatsu-fukushima/20130318/index.html an electric power black out happened on 18 March before 7 PM at the seismic isolated building. After checking, it was found that some of the electric systems were down. The water injection into units 1,2,3 is not affected. However, the cooling of SFP 1, 3 and 4 has stopped. SFP temperatures are between 13.7 and 25 °C. Temperature rise is between 0.1 and 0.3 °C per hour, so that it would take at least 4 days to reach 65°C. Tepco is investigating the cause of the black out and intends to proceed to SFP cooling restart work in function of the investigation results. The nuclear power regulation agency said there was some trouble near a cable connected to a high power switchboard. Monitoring post values are stable. Tepco says it is sorry for being late to disclose the information, as a consequence that it took some time to check the situation.
 
  • #13,848
http://www3.nhk.or.jp/news/genpatsu-fukushima/20130319/index.html Unit 1 SFP cooling was recovered on 19 March shortly after 02:00 PM. Unit 4 SFP cooling was recovered by the implementation of measures such as connecting emergency power generators shortly after 04:00 PM.

The other cooling systems are expected to be recovered by 20 March 2013 08:00 AM.

unit 1,3,4 spent fuel pools and the common pool's cooling systems stopped on 18 March after 3 switchboards connecting to the outside electric power were down.

On 19 March the work to recover two of those swichboards was completed and unit 1 SFP cooling could be started again after a 19 hour long stop.

Unit 4 SFP cooling was restarted using a backup power generator used as an alternative to the remaining switchboard.

Unit 3 SFP cooling is expected to be restarted by around 19 March 08:00 PM, after switching to a different switchboard.

The common pool is expected to be restarted by around 20 March 08:00 AM.

As far as could be checked by visual examination, no damage is seen at the swichboards where the problem occurred, and Tepco is still investigating the causes.

SFP 4 temperature rose from 25°C to 30°C before the cooling was started again, so that the 65°C limit set by the regulation was not reached.

Tepco said it apologizes for causing people to worry as a result of these troubles and apologized again for having been about 3 hours late to publicly disclose the trouble.

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2013/images/handouts_130319_02-e.pdf Power Supply Facilities Failure at Fukushima Daiichi Nuclear Power Station [the title says "As of 4:30 PM on March 19", but it is more likely to be as of 3:30 PM, as they don't mention unit 4 SFP secondary system as being recovered]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2013/images/handouts_130319_04-j.pdf unit 4 SFP cooling secondary system was recovered at 16:13 on 19 March.
 
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  • #13,849
Possible cause for the blackout:

A rat may have short-circuited a switchboard.

Tokyo Electric Power Company says it has found burn marks on one of the power distribution boards that stopped working and brought to a halt cooling systems for spent-fuel pools at the damaged Fukushima Daiichi nuclear plant.

A small animal that appeared to be a rat was also found dead near the board. The company suspects the animal touched the terminal of the board and caused a short circuit.

http://www3.nhk.or.jp/daily/english/20130320_28.html

I'm at a loss for words...
 
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  • #13,850
I don't see anything strange about it. Rats exist. They can crawl into all sorts of spaces.
 

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