Japan Earthquake: Nuclear Plants at Fukushima Daiichi

In summary: RCIC consists of a series of pumps, valves, and manifolds that allow coolant to be circulated around the reactor pressure vessel in the event of a loss of the main feedwater supply.In summary, the earthquake and tsunami may have caused a loss of coolant at the Fukushima Daiichi NPP, which could lead to a meltdown. The system for cooling the reactor core is designed to kick in in the event of a loss of feedwater, and fortunately this appears not to have happened yet.
  • #10,186
Here is the report from NHK saying the workers were released from the hospital on the 28th of March. Says the two workers received localized exposures of between 2 to 3 sieverts. There was one other worker with them who was not standing in water at the time. He was in the hospital for observation, but was also sent home due to no apparent exposure and no symptoms.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110328/saishin07.html
 
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Engineering news on Phys.org
  • #10,187
zapperzero said:
Crane's back. 21:30 GMT. Nothing on the TEPCO camera.
View attachment 36675

As seen from the south webcam, the upper part of this large crane appears to have been raised on Jun 23 03:00 GMT (12:00 JST), the lower part of it had been raised about 24 hours earlier.
 
  • #10,188
MadderDoc said:
As seen from the south webcam, the upper part of this large crane appears to have been raised on Jun 23 03:00 GMT (12:00 JST), the lower part of it had been raised about 24 hours earlier.

Thanks. How did you get at this info?
 
  • #10,189
  • #10,190
  • #10,191
http://www3.nhk.or.jp/news/html/20110624/t10013730411000.html : the solution envisioned by Tepco for the water treatment system is to run it even if the radiation rises higher than the 4 mSv/h target value, and to perform a 2 hour long flushing in order to lower the radiation whenever cartridges need to be changed. The problem is that during flushing the system is stopped and this curtails the quantity of water that can be treated over a given unit of time.
 
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  • #10,192
tsutsuji said:
http://www3.nhk.or.jp/news/html/20110624/t10013730411000.html : the solution envisioned by Tepco for the water treatment system is to run it even if the radiation rises higher than the 4 mSv/h target value, and to perform a 2 hour long flushing in order to lower the radiation whenever cartridges need to be changed. The problem is that during flushing the system is stopped and this curtails the quantity of water that can be treated over a given unit of time.

A two hour hiatus does not seem too bad, unless it has to take place several times each day. If memory serves, the initial thought had been a bi weekly change of the filter media, just by pulling the old skids.
Presumably the skids could be changed out very quickly, assuming appropriate water line couplings and skid handling provisions.
Does anyone know how many skid sets are available?
 
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  • #10,193
SteveElbows said:
And a photo of some shielding they have installed to protect workers in this area (an issue I touched on recently here in the discussion about what dose workers would actually receive)

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110623_03-e.pdf

It remembers me a little bit the hi-tech methods from the soviet guys in Chernobyl...
 
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  • #10,194
etudiant said:
A two hour hiatus does not seem too bad, unless it has to take place several times each day. If memory serves, the initial thought had been a bi weekly change of the filter media, just by pulling the old skids.
Presumably the skids could be changed out very quickly, assuming appropriate water line couplings and skid handling provisions.
Does anyone know how many skid sets are available?

According to http://www.nisa.meti.go.jp/english/press/2011/06/en20110615-3.pdf the plan is to treat 230,000 m³ of contaminated water with "about 400" absorption towers during "approximately one year".

The same document also said :

The Cesium adsorption bars must be changed at a rate of 2-4 bars per day; therefore, the shielding facilities will be internal. Even if there is still some processing capacity remaining, the Cesium bars are managed by replacing them when the surface dosage is a maximum of 40mSv/h, and the exposure at the time of replacement is controlled at a maximum of 4mSv/h.
http://www.nisa.meti.go.jp/english/press/2011/06/en20110615-3.pdf

These figures don't appear to be consistent: 2 bars per day during one year makes 2*365=730 bars which is more than 400.

TEPCO is plugging holes in the roofs of the turbine buildings and stacking sandbags to prevent rain water from entering the facility.

(...)

It says it has so far processed around 2,500 tons of radioactive water with the system. On Friday, it began work to desalinate treated water with the aim of recycling it to cool down the overheating reactors.
http://www3.nhk.or.jp/daily/english/24_19.html

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110624_01-e.pdf : a timetable with details on the volumes of contaminated water treated so far at the water treatment facility, with each processing time, flushing time, and test conditions.

http://twitpic.com/5ejt3u : a more detailed map (shown to journalists during the NISA press conference) of the water treatment facility (the reactor is the box in the top left corner. The Toshiba oil removing system is on the left, the Areva system is in the middle, the Kurion system is on the right side, and the Hitachi desalinating facility on the top ; in between the various tanks are shown)

http://sankei.jp.msn.com/region/news/110624/fks11062412310001-n1.htm The T-hawk helicopter drone made an emergency landing on the top of unit 2 reactor building. No smoke or blaze was reported. They plan to rescue it with a crane.

NISA press conference 2011.06.24 11:10 http://www.ustream.tv/recorded/15577343 : it is expected that the original primary circuit at the unit 1 SFP cooling system can be reused instead of creating a new one as was previously thought. Tepco provided a report on the safety issues concerning the cover for unit 1 : http://www.meti.go.jp/press/2011/06/20110624005/20110624005-2.pdf : the roof can bear the weight of 30 cm of snow. The average maximum wind speeds recorded during the past 10 years being 17 m/s, the structure is designed to withstand 25 m/s winds. It is a "C class building" as regards the earthquake safety. 6 air-filtering units with a 10,000m³/h capacity each will be installed, providing a total capacity of 40,000m³/h (4 units are active, 2 spare units are inactive). There will be a nozzle in the roof, that can be used to pour water into the spent fuel pool. Thermometers will measure the air temperature inside the cover. Cameras will watch the spent fuel pool. Radiation sensors and hydrogen sensors will be installed (sensor locations are shown on the figure page 8). The tsunami wall will be completed by the time the cover structure is finished. The cover sheet material respects the relevant fire resistance standard. The roof and panels could be opened for fire-fighting purposes. The walls of the reactor building will be coated with a dust fixating material beforehand. Even if the cover structure collapses, the added weight is not enough to curtail the reactor building's earthquake or wind resistance. The temperature is expected to rise inside the reactor building, and on a case by case basis spot-coolers will be installed. The humidity is not expected to rise because it will be absorbed by the air-filtering system.

http://www.meti.go.jp/earthquake/nuclear/pdf/20110624-2nisa.pdf : original fax sent by plant manager Yoshida to notify nuclear accident as required by law. It is dated 11 March 16:00 by the fax machine. It says: all AC power is lost ; all units 1~5: all diesel generators are out of order. Unit 6: only one diesel generator is safe. Generators tripped because their seawater cooling system was inundated.
 
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  • #10,195
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  • #10,197
SteveElbows said:
Analysis of the spent fuel pool water at reactor 1 is out:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110624_02-e.pdf

Numbers are a fair bit lower than for reactor 3 pool ( http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110510e12.pdf )

But way, way higher than for reactor 4 pool ( http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110509e3.pdf )

Well, it looks like reactor 4 pool is almost "clean". Perhaps due to repeated massive clean water injection through concrete pump? (which would mean most of the cesium/iodine escaped through evaporation).

About unit 1 & 3 pools, is it possible that the contamination would come mainly from fallen debris and/or initial venting operations?
 
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  • #10,200
SteveElbows said:
Analysis of the spent fuel pool water at reactor 1 is out:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110624_02-e.pdf

Numbers are a fair bit lower than for reactor 3 pool ( http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110510e12.pdf )

But way, way higher than for reactor 4 pool ( http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110509e3.pdf )

Comparing it to the water in the basements of the same units:
http://www.tepco.co.jp/cc/press/betu11_j/images/110603a.pdf

the cesium levels in both the unit 1 and unit 3 spent fuel pools are roughly an order of a magnitude lower than in the water in the reactor building basement / turbine hall basement. Perhaps contaminated steam condensed in both the basement and the spent fuel pool, but at higher doses in the basement.
 
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  • #10,201
http://www.asahi.com/national/jiji/JJT201106240113.html although the valves are supposed to be OK this time, the absorption factor at the Kurion facility is not improving (only 1/10). Together with the Areva system, the decontamination factor for the whole facility is OK, but Tepco wants to investigate the problem.

SteveElbows said:
Where it lands is not visible on the video.

A picture has been released : http://www.tepco.co.jp/en/news/110311/images/110624_1.jpg
 
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  • #10,203
T-Hawk Drone crashes into reactor unit 2 whilst sampling airborne nuclides.

I did a quick cut and cleaned things up. Also got a pick of the crash site (not much left of the drone)

https://www.youtube.com/watch?v=WZQ8w6IgFf4
 
  • #10,204
Borek said:
8:34, not 6:34.

Sorry for the confusion, I was talking about the timestamp that TEPCO have at the top of the screen, not the youtube time for this video.

Anyway, as TEPCO mentioned that this incident happened around 7am, I looked at later footage to see if the drone was spotted at any points later on on the video. There are a couple of moments where a dot is briefly visible in the right sort of place quite some minutes later, but as these are fleeting glimpses its not possible to say for sure, and it is not interesting viewing.

Im quite sad that it crashed, as I would like to know more about what is coming out of building 2 these days.
 
  • #10,205
Having seen more details about the temporary cover building for reactor 1, I quite like it.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110624e15.pdf

OK there are a few risks of things going wrong, but it should enable us to get a much better idea of what radioactive substances are still escaping, the opportunity to filter them, and better monitoring of things like the fuel pool.
 
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  • #10,206
SteveElbows said:
Im quite sad that it crashed, as I would like to know more about what is coming out of building 2 these days.

"Matsumoto said (...) a backup drone can take over the mission" : http://www.washingtonpost.com/world/asia-pacific/drone-helicopter-measuring-radiation-at-japanese-nuclear-plant-makes-emergency-landing-on-roof/2011/06/24/AGWDZmiH_story.html

tsutsuji said:
http://www.asahi.com/national/jiji/JJT201106240113.html although the valves are supposed to be OK this time, the absorption factor at the Kurion facility is not improving (only 1/10). Together with the Areva system, the decontamination factor for the whole facility is OK, but Tepco wants to investigate the problem.

and here is the press release with the measurements : http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110624_04-j.pdf
 
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  • #10,207
tsutsuji said:
"Matsumoto said (...) a backup drone can take over the mission" : http://www.washingtonpost.com/world/asia-pacific/drone-helicopter-measuring-radiation-at-japanese-nuclear-plant-makes-emergency-landing-on-roof/2011/06/24/AGWDZmiH_story.html

Aha, I see that article also describes how the Japanese robot has failed on its first mission.

To be honest I am not too shocked at this news, because that robot looks rather fragile to me, like a prototype that is not ready, especially in the video they posted of it which shows it doing the things it has apparently failed to do properly today.

 
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  • #10,208
SteveElbows said:
Having seen more details about the temporary cover building for reactor 1, I quite like it.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110624e15.pdf

OK there are a few risks of things going wrong, but it should enable us to get a much better idea of what radioactive substances are still escaping, the opportunity to filter them, and better monitoring of things like the fuel pool.

I do not agree. The design criteria for the structure is 25m/sec which works out to 55mph -- which I consider wildly optimistic for sheets of plastic blowing in the wind, but which is still far too low.

Considering emergency counter measure as in service period with regard to the calculation of wind pressure we adopted lowering wind velocity in recurrance interval of 10 years. The wind velocity is above the average maximum wind velocity 17m/sec..


They admit that they chose a wind velocity based on what the structure was claimed to support rather than what the actual wind at the site was and then fudge the matter by claiming that the average maximum wind nearby is 17m/sec (38mph) which gives them a good safety margin. Since it is an emergency measure somehow that makes it work. What they don't want to tell you is the maximum recorded wind at the site, which is really what you have to design to. I'm willing to bet it is more than 38mph.

So they are basing their design for a three-story plastic structure on an exposed coastline in a typhoon zone on an assumption that somehow the maximum wind they will ever see is 38mph. Building codes would be much easier if you could build to the average conditions rather than the maximum ones. Heck, I probably wouldn't even need insulation in my house if the codes worked that way!

I do not see anywhere in the report where they calculate the stress on the structure from the difference in air pressure (either positive or negative) due to the air treatment system and the gas expansion from radioalisis.
 
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  • #10,209
SteveElbows said:
Analysis of the spent fuel pool water at reactor 1 is out:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110624_02-e.pdf

Numbers are a fair bit lower than for reactor 3 pool ( http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110510e12.pdf )

But way, way higher than for reactor 4 pool ( http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110509e3.pdf )

Just for a reminder... They also measured the SFP #2 skimmer surge tank (and also corrected the values of April 12th sampling of the unit #4 SFP?):
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110531e19.pdf

I am making here a small comparision for a starter (as Bq/cm3):
Isotope; SFP 1; SFP 2; SFP 3; SFP 4
Cs134; 12,000; 98,000; 140,000; 130
Cs137; 14,000; 93,000; 150,000; 140

I think it's not that simple, it can be many routes of contamination for a single pool and not the same routes for each of them?
Anyway, they didn't spray seawater into the SFP #1 (afaik), so that's one thing to make it easier.
 
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  • #10,210
TEPCO likely failed to vent No. 1 reactor at tsunami-hit nuclear plant

http://mdn.mainichi.jp/mdnnews/news/20110624p2a00m0na011000c.html
 
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  • #10,211
Okay. I'm hesitant to ask this, but what are the significance of these levels which are so "old"? What is the context with respect to today? Why isn't the power curve more steep? Am I unrealistically impatient? An intellectual exercise is great, but do we have enough information in the www to generate answers to basic questions?

I have been seeing really bizarre nuclear apologist rants and I am worried people at large may be slipping into another dimension. Trying to stay grounded.
 
  • #10,212
Orcas George said:
I do not agree. The design criteria for the structure is 25m/sec which works out to 55mph -- which I consider wildly optimistic for sheets of plastic blowing in the wind, but which is still far too low.




They admit that they chose a wind velocity based on what the structure was claimed to support rather than what the actual wind at the site was and then fudge the matter by claiming that the average maximum wind nearby is 17m/sec (38mph) which gives them a good safety margin. Since it is an emergency measure somehow that makes it work. What they don't want to tell you is the maximum recorded wind at the site, which is really what you have to design to. I'm willing to bet it is more than 38mph.

So they are basing their design for a three-story plastic structure on an exposed coastline in a typhoon zone on an assumption that somehow the maximum wind they will ever see is 38mph. Building codes would be much easier if you could build to the average conditions rather than the maximum ones. Heck, I probably wouldn't even need insulation in my house if the codes worked that way!

I do not see anywhere in the report where they calculate the stress on the structure from the difference in air pressure (either positive or negative) due to the air treatment system and the gas expansion from radioalisis.

Agree entirely that a 10 minute average wind speed is pretty useless as a design spec. Gusts do the damage on sails much more frequently than average winds.
They are probably gambling that it will last for a year or so. By then, it should be less of an issue.
Of course, that supposition flies in the face of the stated plan to cover all 4 reactor buildings this way.
In any case, other than the effort diverted, it does not look to cause much harm.
 
  • #10,213
http://www3.nhk.or.jp/daily/english/25_08.html
Interesting:
temperature near the reactor containment vessel is so high that water inside the device's pipes has evaporated.
 
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  • #10,214
Here's how my logic goes...

There should be no debris lying in the SFP #2, should there?

So condensated steam is a good candidate, as well as contaminated seawater. This a positive scenario where one assumes that fuel is still intact.

Is there any ideas how much of the 93,000 - 98,000 Bq/cm3 of Cs137/Cs134 could have come from condensated steam alone?

For the unit #4 SFP the known maximum from contaminated seawater is only 130 - 140 Bq/cm3 (Cs134/Cs137) but for the unit #2 SFP it could be more depending on where the hoses were located. Also some of cesium may have evaporated from the unit #4?

Is there any basis at this point to conclude that the role of contaminated seawater is of no significant importance for the unit #2 and #3 SFP?
 
  • #10,215
Today I keep seeing press stories such as this one that refer to 11000 pages of faxes that TEPCO sent, and that NISA have now published.

http://www3.nhk.or.jp/daily/english/25_01.html

I had considerable trouble finding these documents, but finally managed to find the right page:

http://www.nisa.meti.go.jp/earthquake/plant/plant_index.html

These are faxes so it is not possible for me to translate any of them using computer translation. It is easy enough to read the charts of data, which does not seem to say much that we did not already know, but I wonder if there is anything interesting in some of the notes that are written on some pages.

For example, is there anything interesting in this document which covers stuff sent on March 15th?

http://www.nisa.meti.go.jp/earthquake/plant/1/230617-1-5.pdf
 
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  • #10,216
desertlabs said:
Okay. I'm hesitant to ask this, but what are the significance of these levels which are so "old"? What is the context with respect to today? Why isn't the power curve more steep? Am I unrealistically impatient? An intellectual exercise is great, but do we have enough information in the www to generate answers to basic questions?

I have been seeing really bizarre nuclear apologist rants and I am worried people at large may be slipping into another dimension. Trying to stay grounded.

Not 100% sure what you mean. With a nuclear disaster such as this, we may expect to wait years to learn true answers to some of the biggest questions, and some may never be answered fully.

The pool contamination figures were brought up now because they just published results for reactor 1 pool, and it can be useful to compare these against older results from other pools. Like most of the data we have, it is not enough to form strong conclusions, as several possibilities exist which could explain the results.

Not sure what you mean about power curve, or what nuclear apologist rants you are talking about.
 
  • #10,217
I suppose that the contamination of water in the basements and SFPs is being measured near the surface, is this correct?

But then the measurements will be meaningful only for metals whose salts are generally soluble, like cesium;as well as forr elements with very soluble anions, like the halogens. Most other elements should tend to precipitate out. Since there is little circulation in those spaces, they should accumulate as a layer of sludge (or dirtier water) at the bottom of the liquid.

Is this likely to be happening? Could it become a problem for the decontamination efforts?
 
  • #10,218
There is no doubt the heavy elements are going to be a huge problem.
 
  • #10,219
elektrownik said:
http://www3.nhk.or.jp/daily/english/25_08.html
Interesting:

BWR water level instruments sense differential pressure between a reference leg (which taps off the upper part of the RPV and is filled and held at a constant level by steam condensing in the leg) and a variable leg (which taps off the lower part of the RPV). The article is trying to say that the drywell temperature near the reference leg is so high that the water in the reference leg has either flashed to steam or evaporated out of the reference leg. As a result, the water in the reference leg is gone or much lower than when the instrument was last calibrated. This usually tends to produce an inaccurate, higher than actual water level indication. Depending on the configuration of the instrument runs, it is possible in some BWRs for certain water level instruments to show an increasing RPV water level trend when actual RPV water level is below the variable leg instrument tap. (Not a good thing.) Such was the case with 1F1 where the RPV water level data showed the core partially submerged when actual water level was downscale and probably below the bottom of active fuel. They will likely discover the same thing in 1F2 and 1F3.
 
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  • #10,220
Indeed that's how it works - zero differential means the vessel is full.

that's the nuisance of getting the drywell real hot and quickly depressurizing vessel , the reference leg may empty itself and take out that important indication. With loss of power there was no drywell cooling so it'd begin an asymptotic approach toward vessel temperature in there.
empty reference leg = false high indication = fail unsafe because you'd think you had water.
... only clue would be when you add water and the indicator doesn't respond because true level is below lower tap... and you might logically think from the high meter reading it's above the top tap instead. ever had a gas gage stuck on full?

poor guys trying to figure all this out by flashlight... they showed true grit.

however - it is easy to lose the reference leg by other means.
in this image
http://www.tepco.co.jp/en/news/110311/images/110604_10.jpg
the three blue handles above center gage are the isolation valves, left and right ones go to the vessel taps.
Middle one is the bypass around gage, called 'equalizing valve', and opening it while other two are open let's the reference leg drain into lower tap. Happens to a lot of inexperienced instrument techs. Sequence is important.
Sometimes you'll get a piece of grit in the equalizing valve's seat and it'll leak which drains the reference leg. At operating pressure the condensing steam can keep up with a real small leak in that valve. As reactor cools down(or drywell heats up) it no longer can.




one wonders how they plumbed up the fire trucks to re-flood, and what they used to judge how much water to inject.
AF.mil has some pics of US GI's machining parts for them but the captions aren't definitive enough to know what the parts were for.
 
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