Japan Earthquake: Nuclear Plants at Fukushima Daiichi

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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.
  • #5,281
Sorry it is not easy to write in English.
Is only an thaught of me.
The Fuel is unloaded from RPV in SFP. The Gates are closed. THe RPV is empty of Water because some Service is doing in the RPV. The Earthqake (or Explosion of Unit3) dameged the Gate between RPV - SFP. The Gate has a high of~5m. The Water goes from SFP to RPV till the lowest Point of the Gate. The Fuel is overheating. etc...
If the RPV is in Service, perhaps there are Pipes open. So the Water can be floded in the Reaktor Building.
On the Thermo Pictures you can see that the temperatur is the same in RPV and SFP but not in the Equipment Pool! So the Gate RPV - E-Pool is in order.
 
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  • #5,282
jlduh said:
Well at least they envisionned the difficulty if it could happen. But finally considered the probability to happen insignificant. Period.

I'm very surprised to see how risks assessment can be done without really taking into account domino effects. The only serious explosion that could destroy the pool is the one of a tornado missile... Well, well.
Well IMO two issues with that doc are:
1: minor problem: degradation of boron absorber material (such as boral) is not addressed. (actually major problem, but it totally pales in comparison with #2)
2: the risk estimate (used in cost benefit analysis) is entirely meaningless. First of all, it addresses only a few low probability scenarios, and secondarily -
Even a small uncertainty in the completeness of understanding of geophysics results in much, much higher risk than one in 700 000 reactor years. Same for even a small distrust (1% risk of corruption) for the data acquisition and simulation in the presence of strong commercial incentive. Historical evidence points at a non-negligible rate of failure for data acquisition or scenario simulation in presence of commercial incentive in favour of the failure.

Furthermore even a single failed "resolution" by NRC is a strong evidence in favour of assigning relatively high probability to "incorrect resolution" scenario (relatively to the risks as estimated), thus rendering the low probabilities stated in resolutions entirely moot and unusable for the cost/benefit analysis. NRC resolutions have to be sampled randomly and carefully reviewed, to estimate the failure rate of NRC's risk analysis. Then the obtained failure rate should be added to any failure frequency indicated in NRC report. That may still be too conservative as it does not address the possibility that more severe issues with larger potential source terms can have higher probability of failure of risk estimate by NRC.
Every real world number is ±something, and every number has probability of being grossly incorrect. I do not see this addressed in the risk analysis.
 
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  • #5,283
Nobody came TEPCO & government english press conference.
 

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  • #5,284
Astronuc said:
What is the source and context of the text? Unit 4 was undergoing service in the Reactor Pressure Vessel, so the whole core had been off-loaded to the SFP. It appears from the text that the RPV was empty in order to perform whatever servicing was going on. It is possible that the gates were damaged in the earthquake, and that they were leaking water from the SFP and Equipment Pool. That's been an unknown. Ideally, the should have been flooding the RPV and cavity, in addition to the SFP.

With respect, I believe the text is the words of triumph61, subjected to Google translation from triumph61's native language.

triumph61 appears to me to be saying that since core shroud replacement was in progress, the reactor was likely not flooded at the time of the earthquake -- while the SFP and the equipment pool had to be. Further, that due to service work being done on the PV one cannot exclude that the PV has had openings made through it, meaning it would not be able to hold a water level above the height of such openings.

In the event something has happened to the gate between the SFP and reactor, water level in the pool would tend to become critically low, any excess water put in the SFP would overflow into the PV, and the PV might overflow further down into the building, the spillage eventually finding its way to the basement.
 
  • #5,285
UNECCS said:
Nobody came TEPCO & government english press conference.

Yeah, there were only two guys who came last time. I guess the info given out at these press conferences is leaving more than seats empty.
 
  • #5,286
Features of the unit 3 explosion
0.0 - 0.4 | a detonation with a flash of fire from SE corner
0.4 - 3.5 | an expulsion of water/water vapor from center/SE of building
0.4 - 6.4 | a high buoyancy airmass rises vertically, dark and debris-filled eventually reaching a height of 500+ m

This goes back to the previous question: the building implodes a fraction of a second before the detonation, the hypothetical explanation for that which makes the most sense to me thus far is that the oxygen inside the building is being consumed by the ignition of the hydrogen

And then this part from Dimytri

Moreover, if the fire becomes oxygen-starved (quite probable for a fire located in the bottom of a pit such as this), the hot zirconium would rob oxygen from the uranium dioxide fuel, forming a liquid mixture of metallic uranium, zirconium, oxidized zirconium, and dissolved uranium dioxide. This would cause a release of fission products from the fuel matrix quite comparable to that of molten fuel

What is it that detonated in the Spent Fuel Pool #3? Would the oxygen in the building being consumed by combustion have any effect on a molten mixture in the bottom of the pool?
 
  • #5,287
Danuta said:
Yeah, there were only two guys who came last time. I guess the info given out at these press conferences is leaving more than seats empty.

Well if they take questions, we need the contact addresses of those two to send them questions to ask
 
  • #5,288
Oak Ridge National Lab analyzed a Station Blackout (SBO) at Browns Ferry (BWR4, Mark1) back in 1981.

http://www.ornl.gov/info/reports/1981/3445600211884.pdf

While this is 30 years old (I assume both their modeling and modifications to the plant have improved the scenario), it paints an unpretty picture of the realities Tepco faced. In regards to the loss of injection sources caused by VDC exhaustion:

"results predict core uncovery 62 minutes after the beginning of boiloff, followed by the inception of core melting 53 minutes later. The model provides that the melted core slumps down to the bottom of the reactor vessel and this results in a predicted failure of the reactor vessel bottom head at approximately three hours after injection capability is lost."

I haven't had time to get through the whole document, but the summary is eye opening itself and has already cleared up a few of my questions. One thing that comes to mind is the explosive venting of Unit 2's Torus:

"the operator loses manual control of the SRVs. The long term result is that a single SRV will continually open into the PSP. The local fluid temperature will monotonically rise, resulting in pressurization of the torus and possible condensation oscillations. The potential exists for rupture of the torus due to overpressure coupled with violent pressure oscillations."

Or was it hydrogen? Interesting nonetheless.
 
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  • #5,291
Curium said:
Features of the unit 3 explosion
This goes back to the previous question: the building implodes a fraction of a second before the detonation, the hypothetical explanation for that which makes the most sense to me thus far is that the oxygen inside the building is being consumed by the ignition of the hydrogen

I have seen no evidence of an initial implosion. The video frames of the unscathed building appear to me to be dead steady right up to the first frame showing a flash & an explosion.
That an implosion could be produced by ignition of hydrogen in air also does not make sense from a theoretical standpoint. True, in the chemical reaction during hydrogen combustion in air, 3 molecules will be consumed for each 2 molecules created, which looked at in isolation at equilibrium would lead to a pressure drop which theoretically could get as high as 20 kPa, but I am pretty sure these buildings would not implode under such minor suction. And that's disregarding that the process is highly exothermic so that the two molecules created will come out of the process with much more kinetic energy than the three molecules consumed, yielding initially a high net increase in pressure.

And then this part from Dimytri
What is it that detonated in the Spent Fuel Pool #3? Would the oxygen in the building being consumed by combustion have any effect on a molten mixture in the bottom of the pool?

I don't think anything detonated in the SFP as such, and even if something did detonate somewhere, as something obviously did, that could hardly
deprive anything of oxygen for very long, seeing that a detonation inside these buildings blows out walls, letting in lots of fresh air..
 
  • #5,292
Some notes about the water level/radiation in the unit 4 basement:

http://search.japantimes.co.jp/cgi-bin/nn20110329a1.html
According to this source the level of water was +80 cm in the unit 4's turbine building. (dated March 29)

http://english.kyodonews.jp/news/2011/03/81375.html
According to this source the level of radiation was less than in unit 1, 2 and 3. (dated March 28)

http://www.world-nuclear-news.org/RS_Contaminated_pools_to_the_drained_2703111.html
The radiation in the unit 1 turbine building was 60 mSv/h. (dated March 27)

So the conclusion is that around 27th - 29th of March the water level in the unit 4's turbine building was +80 cm and radiation less than 60 mSv/h.

http://www.asahi.com/english/TKY201104190193.html
In this source they are saying that level of water was +500 cm and radiation 100 mSv/h in the basement of the building housing the unit 4 reactor. (dated 20th of April)

To me it's unclear if they are talking about the same spot.

If so the conclusion is that during March 27th/29th - April 20th the water level has risen from +80 cm to +500 cm and radiation from < 60 mSv/h to 100 mSv/h.

Any other interpretations?
 
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  • #5,293
~kujala~ said:
<..>
So the conclusion is that around 27th - 29th of March the water level in the unit 4's turbine building was +80 cm and radiation less than 60 mSv/h.

http://www.asahi.com/english/TKY201104190193.html
In this source they are saying that level of water was +500 cm and radiation 100 mSv/h in the basement of the building housing the unit 4 reactor. (dated 20th of April)

To me it's unclear if they are talking about the same spot.

They aren't, the turbine building and the reactor building are two different buildings.
 
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  • #5,294
MadderDoc said:
To me it's unclear if they are talking about the same spot.

They aren't, the turbine building and the reactor building are two different buildings.

Okay, immediately after mensioning "the basement of the building housing" (unit 4) the reporter starts talking about unit 1 - 3's turbine buildings' basements. I had this feeling that the reported might have made a mistake and was really talking about the same buildings. Any chance of mistake here?

Officials of the Nuclear and Industrial Safety Agency (NISA) said April 18 that a pool of water about five meters deep had been found in the basement of the building housing the No. 4 reactor.

Radiation levels as high as 100 millisieverts per hour were detected on the water's surface.

About 54,000 tons of radiation-contaminated water also sits in the basements of the turbine buildings for the No. 1 to No. 3 reactors.
 
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  • #5,295
A message to Jorge Stolfi: as you spent a good time in the modelization of the buildings and reviewed some of the drawings available, if you have a chance to modelize also the turbine buildings maybe you could do a rough estimate of the volume that can be contained in the basements of the turbine buildings (so below the level of the platform ground)? Of course this volume depends on the heights, the length and width of these buildings, but the general layout of the rooms, the thickness of the walls and of course the volume occupied by the machinery is also a factor for the final estimate (for this we can evaluate it by a certain percentage, based on experience of some people on this forum maybe?).

It would be interesting to know what is the water containment capacity in thousands of m3 of these buildings (even a rough estimate).

The fact that these basements are below the ground at least help to somewhat contain the flow of cooling water (highly contaminated) to avoid a direct reject into the see (but anyway this containment cannot be perfect, and we already know it is clearly leaking as there is a fair contamination in the sub drains, probably also in the ground water and so probably also in the discharge flow of phreatic groundwater into the sea).
 
  • #5,296
~kujala~ said:
Okay, immediately after mensioning "the basement of the building housing" (unit 4) the reporter starts talking about unit 1 - 3's turbine buildings' basements. I had this feeling that the reported might have made a mistake and was really talking about the same buildings. Any chance of mistake here?

http://www.foxbusiness.com/industries/2011/04/18/japan-nuclear-agency-reactor-building-4s-basement-filled-meters-water/

"It was the first time that the agency released the extent of flooding in any of the reactor buildings. The flooding situation in the Nos. 1-3 reactor buildings is not known, Nishiyama said.<..> Nishiyama also said the basement of the turbine building of the No. 4 reactor also has about a meter of water."
 
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  • #5,297
MadderDoc said:
triumph61 appears to me to be saying that since core shroud replacement was in progress, the reactor was likely not flooded at the time of the earthquake

According to TEPCO, it was:
http://www.yomiuri.co.jp/feature/20110316-866921/news/20110428-OYT1T00663.htm

(Repeat of link from my post a couple of pages back in this thread.)

Add: See following post by clancy688 for link to English version (without diagram) of the same article.
 
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  • #5,298
http://www.yomiuri.co.jp/dy/national/T110428006723.htm

A hydrogen gas explosion at the No. 4 reactor of the Fukushima No. 1 nuclear power plant on March 15 may have helped prevent spent fuel rods from melting down by causing a flow of water into the pool the rods are stored in, according to research by Tokyo Electric Power Co.

It seems that shocks from the explosion damaged a water gate and caused water to flow into the pool from a neighboring part of the facility, TEPCO said.

Wow. Just wow. They and every city in the surrounding prefectures were indeed SAVED by the explosion of the reactor building. Apparently god has a somehow twisted sense of humor...
 
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  • #5,299
rowmag said:
According to TEPCO, it was:
http://www.yomiuri.co.jp/feature/20110316-866921/news/20110428-OYT1T00663.htm

(Repeat of link from my post a couple of pages back in this thread.)

Indeed, Tepco's having the theory, that water may have overflowed from the reactor cavity into the SFP after an explosion damaged the gate certainly implies that Tepco must know the cavity to be water-filled at the time of explosion. The theory seems to be fed by a suspicion that water fed to the SFP now overflows back into the reactor. One cannot have it both ways, I think, unless the same explosion which so very fortunately damaged the gate such that a disastrous fire could be averted, unfortunately also made the reactor leak. Good news/bad news.

Here's a link to Yomiuri's English translation of the original article:
http://www.yomiuri.co.jp/dy/national/T110428006723.htm
 
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  • #5,300
Toshiba web page describing what happens during a core shroud replacement.

http://www.toshiba.co.jp/nuclearenergy/english/maintenance/replace/shroud03.htm

Initially the RPV is filled with water. In later stages, the RPV is empty. It sounds like a milling machine works underwater and takes off metal at some point to reduce the radiation. The shavings are then removed to the equipment pool. That may explain the thermal images we saw that implied the reactor well was hot.

http://www.irpa.net/irpa10/cdrom/00584.pdf

Further describes the chemical and mechanical decontamination at Unit 2 when its core shroud was replaced years ago.

What I don't understand is if it's possible to decontaminate the inside of a reactor this way, why is it necessary to put decommissioned reactors into SAFSTOR mode for decades? Why not just decontaminate them, cut them up into pieces, and dispose of them?
 
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  • #5,301
Discovery Channel Special on Japan's Nuclear Crisis TONIGHT - 10:00pm eastern April 28, 2011 http://dsc.discovery.com/tv-schedules/special.html?paid=1.14144.26383.0.0
 
  • #5,302
AtomicWombat said:
The radiation measurment rose after the start of N2 injection. N2 injection will do 2 things 1) stir up the contents of wherever it's being injected; and 2) create void space.

Void space in the water will reduce shielding from the radiation sources. Stirring could spread the radiation around.

All this is speculation. I don't even know whether the N2 is injected into the RPV or dry-well.

This could be the source of high radiation increase fresh water and the Oxygen 16 to Nitrogen 16 activation via fast neutrons. Though short lived the resultant gama from its decay is very strong.

Radioisotope 16N is the dominant radionuclide in the coolant of pressurized water reactors or boiling water reactors during normal operation. It is produced from 16O (in water) via (n,p) reaction. It has a short half-life of about 7.1 s, but during its decay back to 16O produces high-energy gamma radiation (5 to 7 MeV).
 
  • #5,303
MiceAndMen said:
Toshiba web page describing what happens during a core shroud replacement.

http://www.toshiba.co.jp/nuclearenergy/english/maintenance/replace/shroud03.htm

Initially the RPV is filled with water. In later stages, the RPV is empty. It sounds like a milling machine works underwater and takes off metal at some point to reduce the radiation. The shavings are then removed to the equipment pool. That may explain the thermal images we saw that implied the reactor well was hot.

http://www.irpa.net/irpa10/cdrom/00584.pdf

Further describes the chemical and mechanical decontamination at Unit 2 when its core shroud was replaced years ago.

What I don't understand is if it's possible to decontaminate the inside of a reactor this way, why is it necessary to put decommissioned reactors into SAFSTOR mode for decades? Why not just decontaminate them, cut them up into pieces, and dispose of them?

Decontamination of the RPV interior surface just removed radioactive surface corrosion/wear particles adhered to it. The RPV is still irradiated/radioactive and shielding is still needed for workers on the support platform.
 
  • #5,304
This how it's supposed to work -

http://www.world-nuclear-news.org/RS_Browns_Ferry_hit_by_major_storms_2804112.html

TVA said it had never experienced anything like the passage of several storm systems through its 80,000 square mile service area. Each one caused more damage to transmission lines until over 100 transmission elements were knocked out and some 677,000 homes left without power.

The three boiling water reactors at TVA's Browns Ferry nuclear power plant in Alabama shut down automatically with cooling systems powered by "a combination of offsite transmission and on-site diesel generators." However, the shutdown was notified as an 'unusual event' to the Nuclear Regulatory Commission "when the normal and alternate power supplies for essential equipment were unavailable for more than 15 minutes." TVA stressed that "safety systems performed well."
They have one line intact, and their 8 EDGs are available.
 
  • #5,305
jlduh said:
A message to Jorge Stolfi: as you spent a good time in the modelization of the buildings and reviewed some of the drawings available, if you have a chance to modelize also the turbine buildings maybe you could do a rough estimate of the volume that can be contained in the basements of the turbine buildings (so below the level of the platform ground)? .

For that one would need diagrams of the turbine building, with reliable dimensions and/or scale. It was already so hard to get those reactor blueprints, and they are still missing many important details...

Moreover I will be rather busy until next week. Anyway, if you manage to get the blueprints, computing the rom volumes by hand is much easier than modeling them with POV-Ray (which in fact does not have a 'volume' function).
 
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  • #5,306
Reno Deano said:
Decontamination of the RPV interior surface just removed radioactive surface corrosion/wear particles adhered to it. The RPV is still irradiated/radioactive and shielding is still needed for workers on the support platform.

Thanks, I see that now. Even though the workers were able to work without respirators, they still needed a bunch of lead shielding before they could go inside.
 
  • #5,308
LabratSR said:
Discovery Channel Special on Japan's Nuclear Crisis TONIGHT - 10:00pm eastern April 28, 2011 http://dsc.discovery.com/tv-schedules/special.html?paid=1.14144.26383.0.0

I would rate it 4/10 based on the fact that I watched it with someone who has not been following the situation as closely as I have, and she was more confused about the entire situation after watching it than she was before.

I saw some photos that I don't recall seeing yet anywhere else. Other than that... meh. It served up the "Fukushima 50" as heroes and perpetuated the myth of workers cutting a hole in the side of Unit 2 after Unit 3 exploded. It did pose a few unanswered and insightful questions about the future of the entire area around the plant.

About a third of it dealt with the general devastation left behind by the earthquake and tsunami. That part was actually interesting, even though it was obviously influenced by the presence of a young and attractive American woman who was up the coast trying to save the whales. She was touched that some of the Japanese people they encountered offered her and her companions food to eat on their treacherous hike away from the coast in search of a ride to the airport.

They had comments from Lochbaum and a few others. Thankfully they did not talk to Gundersen. The show as a whole was not a scientific look into the problems at Fukushima Daiichi. It was more of a "human interest" piece so typical of American television. The message at the end was, "They will eventually get it sorted out."

Better than nothing I guess. If you didn't see it you didn't miss much.
 
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  • #5,309
Due to my diligence in following this topic I spotted many mistakes made in the broadcast.
 
  • #5,310
A few new photos - debris clean-up operation, T-hawk, robots, salvage in exclusion zone:

http://cryptome.org/eyeball/daiichi-npp13/daiichi-photos13.htm"
 
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