Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Barneysee]

On June 1 the remain decay heat output in unit 1 was 3.7 MW while in units 2 and 3 it was 6.3 MW, which is 0.26% of thermal output at shutdown. Over the next 8 months that will go down to 0.21% of thermal output at shutdown, so it's essentially steady now (http://mitnse.com/2011/03/16/what-is-decay-heat/" ), since most of the iodine-131 and other shortlived isotopes are largely gone.

Joe, the data you use to estimate the current heat output assumes that there was no leakage of nuclides as has happened at Fukushima.

The actual current heat output should be considerably less than those figures.
From your source:

"This data is not produced from measured data on the actual reactors at Fukushima, but from using a well established model that is routinely used to estimate decay heat from shutdown reactors.

#9044 Jorge Stolfi

once the fuel is completely molten, the radioactive elements that remain in the liquid corium will produce 30% of the decay heat power that would be produced by the intact fuel;
the other 70% of the decay heat power is due to more volatile elements that will end up elsewhere.

 

[joewein]

Thanks for pointing that out. I had forgotten about that...

So assuming the cores completely melted in all three units, the current heat output of the cores should be more like 1.2 MW in unit 1 and 2.1 MW in units 2 and 3.

The balance of 2.5 MW in unit 1 and 4.2 MW in units 2 and 3 should mostly be in the leaked water, on RPV and containment walls and around pipes, wherever evaporated volatile isotopes could condensate or get leached out.

Does anybody remember how many curies of Cs-134 and Cs-137 were leaked into the atmosphere according to NISA estimates?

 

[MiceAndMen]

According to GE they are actually a Type T Thermocouples with a 350C upper limit. They are magnetically attached which is another big problem. Does anyone know of a magnet that still works when heated over 1000C? Only the thermocouples on the RPV head are attached mechanically.

What document is that from?

There is a lot that is unknown about thermal properties during a core melt event.

http://www.tec-sim.de/images/stories/lecturenotes-late-in-vessel-phenomena.pdf

On page 16 of that document:

Though in the TMI-2 accident no external cooling was available, the vessel wall did not experience any noteworthy thermal attack in contradiction to what all simulations predict to date. The thermal attack on the vessel wall was limited to a hot spot in which the internal vessel wall reached temperatures of ~1100°C in a region of approximately 0.5 meter width, which was rapidly cooled after approximately 1/2 hour.

There is the distinct possibility that molten material relocated out of the RPV without necessarily requiring the entire bottom head to fail. There's also the possibility that such a magnetically attached thermocouple became "no longer attached" to the vessel at some point.

 

[Barneysee]

So assuming the cores completely melted in all three units, the current heat output of the cores should be more like 1.2 MW in unit 1 and 2.1 MW in units 2 and 3.

Considering the tens of thousands of gallons of water which have washed through the containment, those numbers would be an unlikely to achieve upper limit.

But with the good comes the bad - more from Jorge:

On the other hand the corium will contain many long-lived isotopes....

While the contribution of an element to the heat production rate is inversely proportional to its half-life (among other things), its potential for health damage is largely independent of it, at least for lifetimes up to a decade or two. So, while the corium keeps 30% of the decay heat production, it may include a larger fraction of the total health damage potentia of the original fuel.

Thus the decay from this point will be at a slower rate due to the predominance of long-lived isotopes.

In effect, we are now at the same point a plant which had a normal shutdown would have been - several decades later.

 

[htf]

They are magnetically attached which is another big problem. Does anyone know of a magnet that still works when heated over 1000C?

Cobalt would be a Candidate (T_c ~ 1400K). This is the material with the highest Curie temperature I know of.

 

[Cire]

Cobalt would be a Candidate (T_c ~ 1400K). This is the material with the highest Curie temperature I know of.

Do you use a magnet that can withstand those temperatures when the sensor itself is only designed to measure 350C? It seems like that would be prudent to do so.

I'll have to do some more research and see if I can identify the magnetic material used.

Omega sells several type of magnetic thermocouples. The only note I could find stated "Magnet Will Retain 90% of Its Pull at 370°C (700°F)"

 

[tsutsuji]

http://www.nikkei.com/news/category...E1E2E2E68DE3E1E2E5E0E2E3E39790E0E2E2E2;at=ALL Tepco will install a new mainly-Toshiba-made backup system using zeolite for the water treatment facility, setting August as the target date. In addition to the present reverse osmosis desalination system, evaporation-enrichment systems will be installed in August and in October. Unit 4's SFP cooling system will be started in the last decade of July. Unit 1's SFP cooling system in the first decade of August.

http://www.meti.go.jp/press/2011/07/20110711008/20110711008-1.pdf This is a formal NISA request requiring Tepco to write a report about its plans concerning the safety of the SFP cooling systems for unit 1 and unit 4, reminding Tepco the deadline of July 17th as part of the "step one" of the "roadmap".

http://www.tepco.co.jp/cc/press/11071309-j.html (not yet translated into English) Tepco's report on the SFP cooling systems for unit 1 and unit 4, as a reply to the above NISA request.

http://www.tepco.co.jp/en/press/corp-com/release/11071109-e.html Tepco's report on the safety of the nitrogen injection at unit 3.

http://www.tepco.co.jp/en/press/corp-com/release/11071212-e.html this press release is simply called "Water leakage in the reactor building (non-controlled area)". It turns out it is not in Fukushima Daiichi but in Kashiwazaki-Kariwa unit 5.

http://www.tepco.co.jp/cc/press/11071302-j.html (not yet translated into English) This is the second installment of the "Study regarding current seismic safety and reinforcement of reactor buildings at Fukushima Daiichi Nuclear Power Station" and it is about unit 3. The first installment, published on 28 May, was about unit 1 and unit 4 : http://www.tepco.co.jp/en/press/corp-com/release/11052801-e.html

Do you remember the figure page 78 of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110525_01-e.pdf (a slideshow on the "Effects of the Earthquake and Tsunami on the Fukushima Daiichi and Daini Nuclear Power Stations" published in May) showing "Installation of a Backup RHRS pump" to provide sea water cooling for unit 5 or unit 6 ? Whenever I was looking at that picture, I had the painful feeling that the hose would break on the sharp edge of the water intake bank. The artist who drew the picture was not wrong. This is really what happened on 3 July and you probably still have the "hose turned into a fountain" picture released on that day : http://www.tepco.co.jp/en/news/110311/images/110703_1.jpg in your mind. Here is a follow-up :

On July 3, the leakage of seawater at one of outlet piping in residual
heat removal system was detected at Unit5. Though we made countermeasures
to protect the pipe from concrete block corner, same piping condition was
found at the other place in the investigation. From the viewpoint of
preventive maintenance, we stopped residual heat removal system at 6:30
am on 13 July (outside temporary seawater cooling pumps stopped at 6:44
am) and replaced piping.
http://www.tepco.co.jp/en/press/corp-com/release/11071301-e.html

And, as usual, another leak today. Where ? At the water treatment facility of course :

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110713_01-j.pdf (page 1) Flushing was started at 11:00 AM on 13 July. While flushing was being performed, a leak was found near the coupling part of a chemical injection line at the coagulation-sedimentation facility at 01:07 PM. But it is a different location from the leak that occurred on July 10th and July 12th. Flushing has been stopped and the leak is being investigated.

http://www.nikkei.com/news/headline...19595E3E1E2E2848DE3E1E2E5E0E2E3E39F9FEAE2E2E2 the leaked volume is 5 l. Another PVC fitting is being changed for a stainless steel one. The target utilization rate of the facility is lowered from 80% to 70% for July. However 90% is set as the target for August. With an 80% rate, it would become impossible to reach the goal of treating all the 200,000 tons within this year.

http://www.asahi.com/national/update/0713/TKY201107130512.html the utilization rate for the week from 6 July to 12 July was 73%, which is 3 points lower than the 76% achieved a week earlier.

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110713_01-j.pdf (page 2) At around 01:00 PM, the portable monitoring post at the main gate was displaying a zero value. After checking there was nothing abnormal there, the power supply at the seismic-isolated building was restarted at 02:55 PM, which restored a normal value.

 

[clancy688]

Does anybody remember how many curies of Cs-134 and Cs-137 were leaked into the atmosphere according to NISA estimates?

Cs-134: 1.8E16 Bq, ~486.000 Curie
Cs-137: 1.5E16 Bq, ~405.000 Curie

Source: http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/attach_04_2.pdf

 

[NUCENG]

Cobalt would be a Candidate (T_c ~ 1400K). This is the material with the highest Curie temperature I know of.

Nuclear plants have tried to eliminate use of cobalt due to neutron activation to Co60 which is a high energy gamma dose source.

 

[htf]

Do you use a magnet that can withstand those temperatures when the sensor itself is only designed to measure 350C? It seems like that would be prudent to do so.

I don't think so, either. Obviously the designers of the reactors thought: "The RPV won't go beyond 350°C because it must not. If it does a failing temperature sensor is the least problem."

 

[tsutsuji]

Responding to a message of the Science Council of Japan, and with the purpose of learning the lessons from Japan, the French Académie des Sciences is publishing a report on the seismic and nuclear events in Japan. The first 2 parts on the earthquake and on the nuclear accident were published on 28 June with a number of attachments at http://www.academie-sciences.fr/activite/rapport/rads0611.htm . A third part on the medical consequences is not ready yet.

It is written in French, but an English translation is provided for the main text. Here is an excerpt :

The Japanese seismologists responsible for the forecast were convinced that the probability of an earthquake occurring could be calculated in a rational manner, using the definition of characteristic earthquakes for each region. The forecast map, therefore, had not made any provision for an earthquake of magnitude higher than 7.5 in the area closest to the continent and 8.2 closer to the trench. The Tohoku earthquake had a magnitude of 9.0-9.1. On the basis of this forecast, the tsunamis accompanying the earthquakes were not predicted to exceed 4 to 5 metres on reaching the coast. The Tohoku triggered tsunami measured between 15 to 20 metres. The Fukushima nuclear power station site had been built to protect the infrastructures from tsunamis less than 5.7m in height upon reaching the coastline, whereas this tsunami just off the reactor sites measured 14 m with respect to the sea’s normal level.

The main error made by the Japanese specialists was to consider that the past century of seismic events was representative of the continuous, ongoing subduction process. It is, however, known that subduction zones can produce earthquakes equal to or higher than magnitude 9, with lateral movements in excess of 20 to 30 metres, due to stress accumulated over several centuries, i.e., a much longer period than the Japanese specialists had used for their forecasts. The fact that major earthquakes, magnitude 7.5 to 8 had relieved part of the elastic deformation did not preclude that a megathrust earthquake could follow, and indeed this was the case on March 11, 2011. The seismic energy dissipated over the past century only represents 20% of the energy represented by the progressive dip of the Pacific plate sliding under the Japanese archipelago.

(...)

The geological and historic records show that very big tsunamis had hit the Tohoku coastline in years 1611 and 869, and the residual traces are much greater than those left by the earthquakes over the past century (although the lesser magnitude earthquake that occurred in 1896 did produce some really impressive damage)! The cycle for major tsunamis occurring lies between 500 and 1,000 years.

The building of a dense GPS network (30 km between stations) following the Kobe earthquake in 1995 allows scientists to demonstrate that the elastic deformation observed in Japan as a result of the progressing Pacific Plate corresponded to a slip rate close to 80 mm/year, i.e., almost 100% of the subduction rate and not 20% as had been conjectured.

(...)

The Tohoku earthquake serves to show that any forecast based on recent data proves inadequate. We must therefore take both historic and geological data into account if we wish to characterise seismicity over a span of at least several centuries, better still over several millenniums.

pages 10-11 http://www.academie-sciences.fr/en/rads0611_en.pdf

 

[HowlerMonkey]

I'm not sure the engineers of 40 years ago had the tools we are using to critique their reasoning.

 

[Barneysee]

I'm not sure the engineers of 40 years ago had the tools we are using to critique their reasoning.

While they wouldn't have known of the 2004 Indonesian tsunami, the story about big tsunami in Alaska would have been in their local newspapers.

Tsunamis are a well known feature of the Pacific rim, especially Japan.

October 1707 an 8.4 earthquake and tsunami 25.7 meters high hit the Kochi Prefecture

April 1771 earthquake magnitude 7.4 near Okinawa - tsunami is thought to have killed about 12,000 people, the highest seawater runup on Ishigaki Island, range between 30 meters and 85.4 meters.

Nov 1854 The Ansei Quake on the south coast of Japan, was actually 3 quakes, two magnitude 8.4 quakes and a 7.4 quake. The first on near what is today Aichi Prefecture and Shizuoka Prefecture with tsunami. maximum wave of 28 meters at Kochi, Japan, the earthquake and tsunami killed 3,000 people.

June 1896 earthquake in northeastern Honshu - tsunami reached a height of 100 feet, 1896 (magnitude 7,2 / wave height 36m)

September 1923 The Great Kanto Earthquake - eastern Japan devastated Tokyo, Yokohama and the surrounding areas, caused tsunamis with waves reaching 12 meters.

1933 (magnitude 8,4 / wave height 28m): http://en.wikipedia.org/wiki/1933_Sanriku_earthquake

1964 in Alaska (at the time Fukushima was being designed) Mag 9.2, tsunami 27-foot (8.2 m)

The waves produced by the 2004 Indonesian tsunami were (27m) high and killed 230,000 people, that seems a fair warning to the current generation.

I agree that we should let bygones be bygones, but let's not make excuses for bad decisions.

 

[htf]

I'm not sure the engineers of 40 years ago had the tools we are using to critique their reasoning.

I don't think that's the reason. Attitude towards safety has changed dramatically over the last decades. I have an professional circular hand saw from my father, solid carpenter quality form the 60's but you have to be very carefully not to amputate your fingers. This does tell us something about the accepted risk >40 years ago.

 

[NUCENG]

NRC Task Force Report is now available

http://pbadupws.nrc.gov/docs/ML1118/ML111861807.pdf

 

[Atomfritz]

These costs may be so large that industry is forced to shift to smaller reactors that fail somewhat more gracefully, because no country can afford these consequences.

The ability to fail gracefully indeed should be the main development interest of the nuclear industry imho.
Nothing else will be able to generate acceptance in local populations for building new NPP.

According to GE they are actually a Type T Thermocouples with a 350C upper limit. They are magnetically attached which is another big problem. Does anyone know of a magnet that still works when heated over 1000C?
[...]
I'll have to do some more research and see if I can identify the magnetic material used.

Omega sells several type of magnetic thermocouples. The only note I could find stated "Magnet Will Retain 90% of Its Pull at 370°C (700°F)"

At least this provides us with dependable information that the temperatures never reached some Curie temperature (which one remains the question).
(Edit: At least if we assume that the thermocouples are not dangling in thin air now...)

I'm not sure the engineers of 40 years ago had the tools we are using to critique their reasoning.

I disagree.
Traditional practice in German and Austrian construction trade is to dimension flood protection for nuclear plants, hydro dams etc after the highest flood you could possibly expect in the course of 10000 years. We even have a word consisting of three composite words for this: "http://de.wikipedia.org/wiki/Bemessungshochwasser" ".

The Japanese know from their ancients the height of former tsunamis. (Remember the stone monuments already mentioned several times in this thread.)
So they had the advantage of having authentic first-hand data.
But the warning stones of the ancients were - simply ignored!

 

[Dotini]

The Japanese know from their ancients the height of former tsunamis. (Remember the stone monuments already mentioned several times in this thread.)
So they had the advantage of having authentic first-hand data.
But the warning stones of the ancients were - simply ignored!

Well and clearly stated. Bears repetition until the brutal lesson sinks in.

Respectfully submitted,
Steve

 

[swl]

I'm not sure the engineers of 40 years ago had the tools we are using to critique their reasoning.

Even if we are to (falsely) assume that the engineers could not have known of these geological risks when the plant was designed, that does not exonerate the nuclear industry of it's failure to correct the problems over the past 40 years. If the industry operates under the assumption that mistakes made in the past may be ignored because the plant was designed long ago, then the industry is doomed to repeat failures like Fukushima, Chernobyl and TMI.

They cold have shut the plant down for safety upgrades at any time over the past 40 years, but the nuclear industry chose to leave it running 'til 40 minutes before the tsunami hit.

Now they feed our school children with beef containing >3,000 Bq/kg of Cesium supplementation.

 

[biffvernon]

Traditional practice in German and Austrian construction trade is to dimension flood protection for nuclear plants, hydro dams etc after the highest flood you could possibly expect in the course of 10000 years. We even have a word consisting of three composite words for this: "http://de.wikipedia.org/wiki/Bemessungshochwasser" ".

That's interesting. The position of the Torness nuclear power station in eastern Scotland, and other British coastal reactors, did not take account of the Storegga Slide, which caused a large tsunami in about 6100BC.

 

[tsutsuji]

Since NISA has evaluated the injection way we reported as being valid and
the preparation for the injection has been completed, we will conduct the
injection of nitrogen to the reactor containment vessel of Unit 3 from
around 8 pm today.
http://www.tepco.co.jp/en/press/corp-com/release/11071402-e.html

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110714_01-e.pdf section view of the PVC fitting connecting the chemical line with the contaminated water pipe at the Areva system. It shows the one that failed yesterday, but if my understanding is correct, this drawing can also apply to the one that failed on 10 July.

http://www.asahi.com/national/update/0714/TKY201107140324.html the repair at the Areva facility is difficult because of the 100~150 mSv/h radiation. The repairing method needs to be studied again.

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110714_03-j.pdf(page 1) the repair at the Areva facility was completed at 12:07 PM, 14 July. (page 2) the monitoring post at the main gate was displaying a zero value again on 13 July 10:00 PM. The data receiver at the seismic-isolated building will be repaired or changed.

http://news24.jp/articles/2011/07/14/07186434.html and http://news.tbs.co.jp/newseye/tbs_newseye4775950.html ( ) The new water treatment facility, called "Sally" left Yokohama Port this morning. Its start is planned for next month. Sally is made by Toshiba, IHI and US company Shaw. Its decontamination factor is up to one million. According to Toshiba, it can be used as a backup of the Kurion-Areva system.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110714/0720_3_118nin.html Tepco is unable to check for radiation exposure 118 workers who worked in April, and 14 workers who worked in March at Fukushima Daiichi, because their whereabouts are unknown.

About Tokai NPP:

[Japan Atomic Power Company] says some parts were also found missing from a device that injects coolant into the reactor. It also discovered cracks in equipment attached to the upper parts of the reactor.

July 13, 2011 http://www3.nhk.or.jp/daily/english/13_38.html

The [NISA] found that the level of quake-resistance of the electrical equipment at Tokai Daini nuclear power plant in Ibaraki Prefecture was below the standard set by power companies.

July 08, 2011 http://www3.nhk.or.jp/daily/english/08_01.html

http://mytown.asahi.com/ibaraki/news.php?k_id=08000001107090002 At 7:40 AM, 8 July, at Tokai NPP, a worker passed the 2 mSv / day limit while working at the removal of a control rod actuator. With the addition of the other tasks he performed on that day, his total exposure reached 3.3 mSv for that day. The reasons were: 1) forgetting to install the thick radiation shield . 2) forgetting to check the presence of that thick shield 3) While trying to fasten a thin shield with tape, he came too close to the radiation source. It is the first time ever that a worker passes a radiation limit in this plant.

http://www.asahi.com/special/10005/TKY201105110471.html (article dated 15 May 2011 about the sequence of events in March) Although Onagawa NPP achieved cold shut down at around 01:00 AM on 12 March, it took 3 and a half days to achieve cold shut down at Tokai NPP. At 02:00 AM on 12 March the pressure was 58 atmospheres, and it reached 60 atmospheres at 03:00 AM. Injecting water and operating valves, they managed to prevent that the fuel rods emerge out of water, but the water level had a 70 cm variation. Offsite power was restored in the morning of 14 March, and cold shutdown was achieved in the following night. This is more than twice the normal duration to achieve cold shutdown.

 

[clancy688]

That's interesting. The position of the Torness nuclear power station in eastern Scotland, and other British coastal reactors, did not take account of the Storegga Slide, which caused a large tsunami in about 6100BC.

I don't know when the Storegga Slide was discovered, but it hasn't been so long afaik. Perhaps the plants were built before they knew of the Slide.

P.S.
In the novel "The Swarm" by Frank Schätzing, a devastating Storegga slide is triggered, wrecking all european north sea coasts and inundiating several NPPs, thus disabling the cooling systems and leading to beyond design basis accidents. One character is even commenting on how stupid it was to build NPP cooling systems on sea level. ;) (The novel is from mid 2004)

 

[biggerten]

That's interesting. The position of the Torness nuclear power station in eastern Scotland, and other British coastal reactors, did not take account of the Storegga Slide, which caused a large tsunami in about 6100BC.

"The Storegga Slide occurred 8200 years ago and was the last megaslide in this region where similar slides have occurred with intervals of approximately 100 ky since the onset of continental shelf glaciations at 0.5 Ma."

"The Storegga Slide (Fig. 1) is one of the largest submarine slides discovered, and has been known since the 1970s"

from "Explaining the Storegga Slide", http://www.ig.uit.no/geo3128/02-Bryn_etal_MPG_2005.pdf

Interesting stuff, what one can learn.

On a side note, if I may, I'd like to thank tsutsuji for keeping us up to date. I really, really, appreciate it.

 

[Barneysee]

It is four months to the day since Unit three blew up.

And there is some recent progress in the #3 thread.
https://www.physicsforums.com/showthread.php?t=505630&page=24

 

[tsutsuji]

http://www.asahi.com/national/update/0714/TKY201107140324.html (same link as yesterday, but it was updated) For the repair under the 100~150 mSv/h radiation at the Areva facility on 14 July, they created a 10 people team, each one working no longer than 2 minutes. A test run was started at 3 PM and the facility was started again at 6 PM.

http://www3.nhk.or.jp/news/html/20110715/t10014229731000.html The water treatment facility was stopped again at 5 AM on 15 July in order to investigate the reason why the flow decreased to 37 ton/hour instead of the expected 50 ton/hour. The first 100 m³ of nitrogen have been successfully injected into unit 3.

http://www.jiji.com/jc/c?g=soc_30&k=2011071500409 It is suspected that the flow drop at the water treatment facility is due to air trapped in the pipes. The water spray at unit 2's SFP cooling system is broken down. SFP 2's temperature has risen to 40°C. Tepco has updated a control panel in order to enable the installation of the new Toshiba-IHI-Shaw water treatment system.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110714_06-e.pdf Diagram, pictures, details of the new Toshiba-IHI-Shaw (SARRY) water treatment system.

http://www.tepco.co.jp/en/press/corp-com/release/11071501-e.html [Main Gate monitoring post] "at 6:15 pm on July 14, we replaced with alternative portable monitoring post and was restored. We also confirmed monitoring data was at the same level as before the equipment failure."

http://www.tepco.co.jp/cc/press/11071507-j.html The valve on the line bringing water from the filtrate tank to unit 2 SFP cooling secondary circuit was closed. At 11:47 they opened the valve and the SFP2 cooling system was started again. A test run of unit 5 main RHR B system sea water pump was started at 10:16 AM. The water treatment facility was started again at 02:21 PM

http://www.nikkei.com/news/headline...19481E3E7E2E1868DE3E7E2E5E0E2E3E39797E0E2E2E2 During the water treatment facility shutdown this morning they bleeded air from the pipes and changed some hoses, but the flow had little improved, being still a little below 40 ton/hour after the facility was started again this afternoon.

http://www.yomiuri.co.jp/science/news/20110715-OYT1T00969.htm Tepco is taking 570 tons of fresh water from the river to raise the water level in the fresh water tank. No water had been taken in the river for two weeks. Yomiuri says this is due to the water treatment facility's poor performance, but I am not sure I understand. Have they really run out of stored decontaminated water ? On 12 July, they had 4563 m³ in the desalinated water receiving tank, according to http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110713e10.pdf . If the 3 reactors together need 400 m³ every day, this was enough to cover more than 11 days.

 

[swl]

http://www3.nhk.or.jp/news/html/20110715/t10014229731000.html The first 100 m³ of nitrogen have been successfully injected into unit 3.

Does this mean that they have now evacuated an additional 100 cubic meters of contaminated gas from the reactor?

Does anyone know the flow rate? Also, at this [STRIKE]late stage[/STRIKE] not so early stage in the accident, is hydrogen production likely to remain problematic? As far as I can tell, there should be little trouble of hydrogen collecting within the reactor 3 building. Are they just trying to keep oxygen out of the (mostly empty?) RPV?

Also google tranlates the above to read "According to TEPCO, significant changes in the amount of external radiation that is observed." But my elementary knowledge of the written language seems to indicate that "東京電力によりますと、外部の放射線の量に目立った変化は見られないということです。" means Tepco says they have not been able to detect a change in the external radiation levels. I don't have access to my lovely (carbon) translator at the moment, so I'm not sure...

 

[tsutsuji]

Does this mean that they have now evacuated an additional 100 cubic meters of contaminated gas from the reactor?

Does the following answer your question ?

[Regarding the injection of nitrogen to the reactor containment vessel of Unit 3](2) Environment impact due to radioactive material released from the PCV by the injection

The radioactive material does not newly shift to the vapor phase part of the PCV by the injection of nitrogen. Thus the amount of vapor per a certain period released from the PCV increases due to the injection of nitrogen and the steamy condensation prevention effect, however there is not a possibility that the nitrogen injection affects the surrounding environment.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110711e11.pdf

Does anyone know the flow rate?

http://www.nikkei.com/news/category...39797E3E2E2E2;at=DGXZZO0195165008122009000000 14 m³/h of nitrogen will be injected into unit 3

For the google translation problem you mentioned, try this link : http://translate.google.com/#ja|en|外部の放射線の量に目立った変化は見られない

 

[Barneysee]

Does this mean that they have now evacuated an additional 100 cubic meters of contaminated gas from the reactor?

LOL

is hydrogen production likely to remain problematic?

It probably remains a possibility that an OX/H reaction could still go bang ala unit 2. If it did, TEPCO would sure look foolish.

I think I would be pumping nitrogen too if I were them.

 

[joewein]

is hydrogen production likely to remain problematic? As far as I can tell, there should be little trouble of hydrogen collecting within the reactor 3 building. Are they just trying to keep oxygen out of the (mostly empty?) RPV?

The talk about nitrogen injection started as soon as they got cooling water flow going again and especially after they formulated their plan of bringing all three reactors to "cold shutdown" (whatever that means for reactors as wrecked as that). If the temperature drops below boiling, as per definition of cold shutdown, then there is no steam pressure that would keep external oxygen out, so they were concerned about any lingering hydrogen from the zirconium reaction mixing with air, with the containments having lost air tightness. If the cooling water condensates steam in the containment, it could create a vacuum that sucks in air.

I am not sure how much of that hydrogen could be left by now. A lot of cooling water must have boiled into steam and displaced hydrogen, diluting it further and further.

On the other hand, as long as there are both high levels of radioactivity and water in the plant, hydrogen + oxygen production of from radiolysis of water remains possible, especially if it's hot enough (at least in places) for the gases to escape with steam from boiling liquid before they have a chance of recombining.

Injecting nitrogen is the safe thing to do if you can't be sure about how much hydrogen is remaining or is yet to be produced from radiation.

 

[tsutsuji]

http://news.xinhuanet.com/english2010/world/2011-07/16/c_13988710.htm "Japan's Kansai Electric Power Co. said on Saturday it planned to manually shut down the No.1 reactor at its Ohi nuclear power plant in western Japan's Fukui Prefecture due to technical glitches with its cooling system"

http://sankei.jp.msn.com/affairs/news/110716/dst11071612160010-n1.htm Tepco announced the safety measures against the Typhoon No. 6 at Fukushima Daiichi. The megafloat filling operation will be stopped. Big swell being expected, hoses will be removed and equipments will be tightened with ropes. Roof sheets will be installed on turbine buildings, and sandbags will be installed around buildings to stop rain water.

http://www3.nhk.or.jp/news/html/20110716/t10014253181000.html Tepco has announced its plans for the July 2011 - January 2012 "step 2" of the roadmap. It was not expected to go beyond studying a ground water shielding wall, but it was decided to step up the pace and to start building the wall as part of "step 2". It is also planning improvements at the water treatment facility such as shortening or reinforcing the 4 km long pipes. A middle term schedule will be announced on 19 July. It is already known that the building of solid containment structures for reactors and the removal of fuel from the spent fuel pools will take about 3 years.

http://sankei.jp.msn.com/affairs/news/110716/dst11071611560009-n1.htm Two reasons are suspected for the decrease of the water treatment facility flow rate to 37 ton/hour instead of the expected 50 ton/hour : air trapped in pipes and foreign bodies. After bleeding air from pipes yesterday, the flow increased to 39 ton/ hour. Tepco keeps investigating.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110716_01-e.pdf Diagrams showing "Countermeasures against Decline in Flow Rate".

 

[Bandit127]

A new video (18.2 Mb) is available from Tepco's site from a 'quince' robot in Unit 2.

Towards the bottom of the video are windowed video feeds:
Left pane = wide angle overhead view of the robot.
Centre pane = rear facing
Right pane = front facing

At the top are some other bits & pieces, including temperature (centre). I don't know if the 2nd from the left is radiation, temperature, or what.

http://www.tepco.co.jp/en/news/110311/images/110716_01.zip"

 

[tsutsuji]

http://elpub.wdcb.ru/journals/rjes/v12/2011ES000503/2011ES000503.pdf (I.N. Tikhonov, "2011 Mega-earthquake on 11 March 2011 in Japan and aftershock process dynamics' development", Russian Journal of Earth Sciences, written in April 2011, published in May 2011) Choosing to focus on the earthquakes with a magnitude greater than 7.6, this article provides on page 4 two simple maps of the historical seismic data in North-East Japan in support of the view that "the existence of a seismic gap at the length of ~ 800 km was retrospectively revealed, located to the south of 39°N and filled recently with aftershocks of the mega-earthquake".

Left pane = wide angle overhead view of the robot.

There is also a small screen below that one. It is marked with 水位計リール　"water level gauge reel".

I don't know if the 2nd from the left is radiation, temperature, or what.

The word "dose" can be read. The figures are consistent with the values in milisievert/hour provided at http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110711_04-e.pdf which also maps the robot trajectory inside the reactor building.

The analysis of the air samples taken by the robot are available on http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110711_03-e.pdf . It shows that the air can't be breathed.

A video showing the outer view of quince during a test was provided in June : http://www.tepco.co.jp/en/news/110311/images/110620_25.zip (4.6 Mb).

 

[Bandit127]

http://elpub.wdcb.ru/journals/rjes/v12/2011ES000503/2011ES000503.pdf (I.N. Tikhonov, "2011 Mega-earthquake on 11 March 2011 in Japan and aftershock process dynamics' development", Russian Journal of Earth Sciences, written in April 2011, published in May 2011) Choosing to focus on the earthquakes with a magnitude greater than 7.6, this article provides on page 4 two simple maps of the historical seismic data in North-East Japan in support of the view that "the existence of a seismic gap at the length of ~ 800 km was retrospectively revealed, located to the south of 39°N and filled recently with aftershocks of the mega-earthquake".



There is also a small screen below that one. It is marked with 水位計リール　"water level gauge reel".



The word "dose" can be read. The figures are consistent with the values in milisievert/hour provided at http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110711_04-e.pdf which also maps the robot trajectory inside the reactor building.

A video showing the outer view of quince during a test was provided in June : http://www.tepco.co.jp/en/news/110311/images/110620_25.zip (4.6 Mb).

I have to use Google and I hope it makes sense.

我々の知識への貢献は、測定を超えた価値を持っていま

Thank you Tsutsuji for all your posts.

Jim

 

[Atomfritz]

The talk about nitrogen injection started as soon as they got cooling water flow going again and especially after they formulated their plan of bringing all three reactors to "cold shutdown" (whatever that means for reactors as wrecked as that). If the temperature drops below boiling, as per definition of cold shutdown, then there is no steam pressure that would keep external oxygen out, so they were concerned about any lingering hydrogen from the zirconium reaction mixing with air, with the containments having lost air tightness. If the cooling water condensates steam in the containment, it could create a vacuum that sucks in air.

I am not sure how much of that hydrogen could be left by now. A lot of cooling water must have boiled into steam and displaced hydrogen, diluting it further and further.

On the other hand, as long as there are both high levels of radioactivity and water in the plant, hydrogen + oxygen production of from radiolysis of water remains possible, especially if it's hot enough (at least in places) for the gases to escape with steam from boiling liquid before they have a chance of recombining.

Injecting nitrogen is the safe thing to do if you can't be sure about how much hydrogen is remaining or is yet to be produced from radiation.

There was already much sub-atmospheric pressure. Just see Jorge Stolfi's great diagrams.
To me it looks not much different from that what happens when you let a kettle with a bit of water cool down after boiling.
In fact this makes me somewhat optimistic that there is probably no big danger of melt-through. Tepco probably just wants to make sure that there is insufficient oxygen so that the reactors don't poop again.

http://news.xinhuanet.com/english2010/world/2011-07/16/c_13988710.htm "Japan's Kansai Electric Power Co. said on Saturday it planned to manually shut down the No.1 reactor at its Ohi nuclear power plant in western Japan's Fukui Prefecture due to technical glitches with its cooling system"

http://www.spiegel.de/wissenschaft/technik/0,1518,774825,00.html" Dunno what is correct.

url]http://sankei.jp.msn.com/affairs/news/110716/dst11071612160010-n1.htm[/URL] Tepco announced the safety measures against the Typhoon No. 6 at Fukushima Daiichi. The megafloat filling operation will be stopped. Big swell being expected, hoses will be removed and equipments will be tightened with ropes. Roof sheets will be installed on turbine buildings, and sandbags will be installed around buildings to stop rain water.

Sand bags just for rain?!? Sounds more like some flooding. How much liters per sq.m. is normal in Japan?!?

http://sankei.jp.msn.com/affairs/news/110716/dst11071611560009-n1.htm[/URL] Two reasons are suspected for the decrease of the water treatment facility flow rate to 37 ton/hour instead of the expected 50 ton/hour : air trapped in pipes and foreign bodies. After bleeding air from pipes yesterday, the flow increased to 39 ton/ hour. Tepco keeps investigating.

Just my 2 ct.: When scaling up from liters (La Hague) to cubic meters (Fukushima Daiichi) they forgot to include "Luftabscheider" (don't know english word, sorry. These devices keep tubes and such free from air and gases, preventing them from clogging. Can anyone please tell how this is called in english? -thanks!)

 

[Barneysee]

Deaerator (removes the air)

 

[joewein]

Sand bags just for rain?!? Sounds more like some flooding. How much liters per sq.m. is normal in Japan?!?

Here's a rainfall map from a typhoon two months ago:

http://www.nasa.gov/images/content/555707main_20110602_Songda-TRMM_full.jpg

As you can see, some areas got in excess of 100 mm during that one storm (i.e. 100 l per m²), two months' worth of rainfall in Germany. Landslides during typhoons are quite common in Japan.

 

[turi]

- At 11:40 am on July 17, the Clean up Water System of Unit 2 has been
restored.
* Clean up Water System (CUW): system to remove impurities in reactor
water and maintain the water quality; The system is also used to
control reactor water level by discharging redundant water from the
reactor during a regular inspection or reactor shutdown.

http://www.tepco.co.jp/en/press/corp-com/release/11071708-e.html"
Interesting. Is the Clean up Water System now being used for the spent fuel pond? I can't really see them using it for cooling the reactor as such.

 

[Atomfritz]

Thanks all for the info!

...in excess of 100 mm during that one storm (i.e. 100 l per m²)

This really worries me.
At least, if there such "rains" are regular, I no longer wonder why the roof of Unit 3 so quickly looked like having been cleaned with a big water hose.
I could imagine if such masses of water are going to splash down through the staircases into the lower floors, the radiation measures done recently could be obsolete soon again.

(image taken from http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110717_01-e.pdf")

I am really surprised of this sudden "appearance" of a roof for Unit 3.
Is Tepco ahead of their "official" roadmap, or did they just realize that they do not want big rainwater streams in the reactor buildings?

 

[Caniche]

(image taken from http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110717_01-e.pdf")

Very comforting ,all neat and tidy no detritus not even a stray roof spar. Bit worried about the lack of blue goo that keeps down the wind blown poison though, thought they'd sprayed all over the site a dozen times just to be sure.Maybe its a projected image like estate agents use

 

[tsutsuji]

I am really surprised of this sudden "appearance" of a roof for Unit 3.
Is Tepco ahead of their "official" roadmap, or did they just realize that they do not want big rainwater streams in the reactor buildings?

I think Tepco is merely showing the roof sheets before installing them on a roof, saying the sheets on the picture are intended for unit 3.

Judging by the greenish color of the reactor building in the background, this must be reactor No.5 or No. 6. (You can compare the bluish color of reactors 1~4 with the greenish color of reactors 5~6 on http://cryptome.org/eyeball/daiichi-npp2/pict55.jpg ). I think the background of http://www.tepco.co.jp/en/news/110311/images/110717_1.jpg (or http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110717_01-e.pdf ) is, from left to right : the Futaba and Yonomori power lines, unit 5 reactor building and unit 5 turbine building.

The rain from typhoon 6 has not started pouring. If typhoon 6 ever comes to Fukushima, it will be after it reaches Tokyo, and it is not expected in Tokyo before July 20th : see http://www3.nhk.or.jp/news/html/20110717/t10014272451000.html

http://www.tepco.co.jp/en/press/corp-com/release/11071708-e.html"
Interesting. Is the Clean up Water System now being used for the spent fuel pond? I can't really see them using it for cooling the reactor as such.

This news is about the other plant, Fukushima Daini, located a few kilometers south from Fukushima Daiichi.

 

[turi]

"Interesting. Is the Clean up Water System now being used for the spent fuel pond? I can't really see them using it for cooling the reactor as such."
This news is about the other plant, Fukushima Daini, located a few kilometers south from Fukushima Daiichi.

Right. Sorry for the mixup. And thanks for all your posts, they're very informative.

 

[Gary7]

Regarding the "roof", the Tepco press release for today says:

As precaution against rain for the exposed top section of the turbine building for Reactor #3, construction of a temporary roof was begun at 8:30am (July 18th).

(original Japanese) ７月18 日午前８時30 分、３号機タービン建屋屋上開口部の雨水対策として仮屋根の取り付け作業を開始しました。

Also mentions a worker who was injured in a fall from an electric pole/pylon today, and was transported to hospital via helicopter.

http://www.tepco.co.jp/nu/f1-np/press_f1/2011/htmldata/bi1632-j.pdf

 

[tsutsuji]

http://www.spiegel.de/wissenschaft/technik/0,1518,774825,00.html" Dunno what is correct.

I think both are correct :

The functions of the ECCS accumulators are to supply water to the
reactor vessel during the blowdown phase of a loss of coolant accident
(LOCA), to provide inventory to help accomplish the refill phase that
follows thereafter, and to provide Reactor Coolant System (RCS) makeup
for a small break LOCA.
(...)
The accumulators are pressure vessels partially filled with borated water
and pressurized with nitrogen gas.
http://pbadupws.nrc.gov/docs/ML0916/ML091671716.pdf

See also the diagram released by Kepko showing the accumulator that broke down at Ohi NPP : http://www.kepco.co.jp/pressre/2011/__icsFiles/afieldfile/2011/07/16/0716_1j_01.pdf (ぼう酸水=borated water ; 窒素=nitrogen ; 弁=valve ; 蓄圧タンク= accumulator ; 水位計=water level gauge ;　圧力計=pressure gauge)

Here is Kepko's 16 July press release :

About the manual shutdown of Ohi NPP unit 1 (decline of pressure at accumulator C)

Ohi NPP unit 1 (pressurized water reactor, nominal output 1,175,000 kW, nominal thermal power 3,423,000 kW) was undergoing a test run as part of inspection No.24 when the "high/low pressure, accumulator※ C" alarm was issued, at 10:46 PM, 15 July 2011.

When we checked the pressure gauge, instead of the normal 4.60 MPa, the pressure was 3.65 MPa, which is below the safety limit of 4.04 MPa. For this reason, we started bringing nitrogen using the nitrogen supply line at 11:20 PM and at 11:45 PM the pressure had risen back to 4.09 MPa, satisfying the 4.04 safety standard.

The supply of nitrogen was completed at 12:38 AM, today, and a visual inspection of the accumulator and nearby valves was undertaken, but no abnormality was observed. The pressure was stabilized at 4.08 MPa.

As we prioritize safety, in order to inspect the causes of the pressure decline and to implement countermeasures, we decided to start decreasing the output at around 1 PM today, and at around 9 PM we shut down the reactor.

This event is not causing radiological consequence to the environment.

※ Accumulator : Accumulators are tanks storing borated water. Each of the 4 primary cooling systems is installed with one. During a loss of coolant or other accident, when the pressure in a primary cooling system drops lower than the pressure of the nitrogen-pressurized accumulator, borated water flows into that primary cooling system.About the manual shutdown of Ohi NPP unit 1 :
http://www.kepco.co.jp/pressre/2011/__icsFiles/afieldfile/2011/07/16/0716_1j_01.pdf (pdf 28.6 KB)

Source : http://www.kepco.co.jp/pressre/2011/0716-1j.html (my translation)

About Fukushima Daiichi NPP :

http://www.yomiuri.co.jp/science/news/20110718-OYT1T00495.htm there is more than one hole in the roof of unit 3 turbine building. The largest is 14 x 11 m wide. The repair is made with 3 steel sheets of 5 x 16 m each. While this repair is done today, the other holes will be repaired tomorrow. What is feared is that if too much rain water pours through the holes, the water accumulated in the turbine building might overflow and leak into the sea.

http://www.asahi.com/special/10005/TKY201107170417.html this is an assessment of the "step 1" of the roadmap. The following are marked with the "〇" (completed) symbol :

〇 closed loop reactor cooling
〇 starting the water treatment facility
〇 nitrogen injection
〇 SFP cooling (implemented in advance at units 2 & 3)

Then we have the "△" (under execution) symbol

△ reinforcement of unit 4 against earthquakes
△ hyperthermia prevention
△ assessment of the radiological status of the environment
△ removing debris

Then the "×" (execution impossible)

× repair the containment vessels (the locations of the damages are not even known)

It is expected that the government will announce tomorrow that they will start to study the lifting of some of the evacuation-prepared areas, based on the prerequisite that the nitrogen injection prevents hydrogen explosions and that new radiological emissions are curbed at a low level.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110718/0805_suiryou.html On 17 July afternoon, Tepco changed the pump that injects water into both unit 1 and unit 2 reactors. Its maximum flow rate is 20 m³/hour. On the morning of 17 July, the flow rate injected into unit 1 declined to about 3 m³/hour instead of the expected 3.8 m³/hour, ringing an alarm. The flow rate had to be ajusted again to 3.8 m³/hour. While nothing similar happened on the unit 2 line, it is the third time this sort of trouble happens at unit 1. For that reason it is believed that there is dirt in the piping to unit 1.

 

[Joe Neubarth]

Iodine 131 Four months after Reactor Three Blew? One hundred and twenty some days after Reactor Three Building blew, and they are still finding I-131 ?

This is very frightening. As previously stated, Iodine-131 being very radioactive has a rapid half life. Every week or so half of it is gone. After 80 days it should be almost impossible to detect. Yet, here we are FOUR months after the BIG Detonation of Reactor Three and we are still seeing large amounts of Iodine 131 in water samples.

Am I wrong or should this not be happening?

Tokyo gov’t finds iodine-131 levels up to quadruple cesium levels in water reclamation centers.
July 18th, 2011 at 07:35 AM


Measurements of radioactivity in sewage treatment, etc., Sewer Authority (Tokyo), July 15, 2011:
http://translate.google.com/translate?act=url&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=ja&tl=en&u=http://www.gesui.metro.tokyo.jp/oshi/infn0533.htm

 

[robinson]

It may mean the amount of Iodine that was released was far higher than was reported.

 

[Atomfritz]

Tokyo gov’t finds iodine-131 levels up to quadruple cesium levels in water reclamation centers.
July 18th, 2011 at 07:35 AM


Measurements of radioactivity in sewage treatment, etc., Sewer Authority (Tokyo), July 15, 2011:
http://translate.google.com/translate?act=url&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=ja&tl=en&u=http://www.gesui.metro.tokyo.jp/oshi/infn0533.htm

Maybe just a "spelling mistake" - the long-term iodine measurements after emissions usually regard I-129 (halftime 15 mill yrs).

See also the diagram released by Kepko showing the accumulator that broke down at Ohi NPP : http://www.kepco.co.jp/pressre/2011/__icsFiles/afieldfile/2011/07/16/0716_1j_01.pdf (ぼう酸水=borated water ; 窒素=nitrogen ; 弁=valve ; 蓄圧タンク= accumulator ; 水位計=water level gauge ;　圧力計=pressure gauge)

Thanks!
This makes me feel understand the differences of Xinhua and Spiegel report, both seem correct to me even if the first impression looks quite different.

Regarding the "roof", the Tepco press release for today says:

As precaution against rain for the exposed top section of the turbine building for Reactor #3, construction of a temporary roof was begun at 8:30am (July 18th).

The article Tsutsuji quoted says that only the biggest hole in T/B roof is 11x14 meters and there are others. On the satellite photos these holes seem soo small!
And that they appear to have set up some kind of harbor near units 5+6, this seems very sensible. They are really doing much much work, without any kamikaze like in Russia.

I well understand that they want to get the holes closed before the tsunami comes. Could else be like waterfall sinks.
And, the rain decontaminating the roofs so probably will just conveniently flow into the ocean. Nice!

 

[joewein]

Maybe just a "spelling mistake" - the long-term iodine measurements after emissions usually regard I-129 (halftime 15 mill yrs).

I have never seen I-129 mentioned in Tokyo water-related data.

The numbers for levels in drinking water published by the city only listed I-131, Cs-134 and Cs-137:
http://monitoring.tokyo-eiken.go.jp/monitoring/w-past_data.html

Same for most seawater figures released.

With its long half life it probably doesn't contribute a lot of becquerels relative to its weight, so I don't think a mixup with it would explain those becquerel figures.


Given that I-131 levels in early April where an order of a magnitude higher than cesium levels, they should have reached parity around early May. By July 4-5 when the water sludge was measured, another 8 half lives of I-131 should have passed, so I-131 should be two orders of a magnitude below cesium.


If in this particular source they were at similar levels, one would assume chemical reasons for that, i.e. cesium didn't precipitate with the mud as much iodine did. Cesium salts should be highly soluble (similar to potassium salts) and it would never occur in elementary form outside the lab. Iodine does have insoluble salts (such as silver iodide) and in elementary form is not particularly water soluble.

 

[tsutsuji]

http://www3.nhk.or.jp/news/html/20110719/t10014286881000.html With the purpose of recovering the 50 m³/hour flow rate from the decline to 37 m³/hour, the water treatment facility had been shut down on the morning of 15 July to make repairs such as bleeding air and changing hoses for ones with lesser resistance, and a 39 m³/hour flow rate had been achieved. However on the morning of 18 July the flow rate had dropped to 37 m³/hour again. Tepco admits that it ignores the cause of the problem.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110719/0625_kangae.html The expectation that the government would define more precisely today what is meant by the "cold shutdown" that should lead to a lifting of the 20 km range no-entry zone has been deceived. The definition provided by the government today remains vague, saying the RPV bottom temperature must be around 100°C and human exposure to radiation must be largely curbed. This is far from a concrete definition of radioactive substances and radiation dose limits.

http://mainichi.jp/select/weathernews/news/20110719ddm003040126000c.html The exposure of two workers who repaired the big hole on unit 3 turbine building roof yesterday passed 10 mSv, with a maximum of 12 mSv. Today the plan is to repair one 5 m x 2 m oval-shaped hole and a number of skylights blown up by the explosion, and to install sandbags preventing water to flow into a gutter whose down pipe is damaged.

 

[joewein]

We have discussed the video in which Arnie Gundersen spotted what looked like a single "handle" for a fuel assembly in the debris-filled unit 3 pool.

I just noticed a picture of the same pool from probably the refueling last year on this page. Look for the picture labeled "Reactor 3 refueling - mox in top left corner".

http://www.houseoffoust.com/fukushima/tepco_pics/R3_mox_upperleft.jpg

If the black items are fuel assemblies then many are quite spread out over the pool, instead of in largely complete rows as in unit 4.

 

[Joe Neubarth]

I would think that spreading them out would be a prudent thing to do. I expect that the holding racks are very secure, but a more uniform distribution of weight would just make sense.

 

[Joe Neubarth]

It may mean the amount of Iodine that was released was far higher than was reported.

I think many of us suspect that, simply because of the manner of revealing information that TEPCO established very early on.