Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[dh87]

10,000,000 Curies?! Really? The equivalent radioactivity of ten thousand kilograms of radium?! Ten metric tonnes?!

Well, yes. TEPCO says 3.7e+17 Bq, and there's 3.7e+10 Bq/Ci. Radium 226, on which the unit is based, has a 1600-year half-life, resulting in that large mass that you quote (since becquerels and curies are both units of decays per unit time). If you calculate for I-131, you'll get a much smaller mass.

The number that TEPCO announced doesn't appear to include the radioactivity that's in the 70,000,000 liters of water sloshing around the reactors, nor the 100,000 Curies (4,700 TBq) that has already been released into the Pacific Ocean.

 

[tyroman]

From Cainnech's post #4653:
https://www.physicsforums.com/showpost.php?p=3262389&postcount=4653

"TEPCO suspects that the water leaked from the RPV is leaking through the cracks in the wall that separates the Reactor 3 turbine building and the Reactor 4 turbine building."

Could the features I have noted in the photos below possibly be evidence of the size of the "cracks" between the two turbine buildings? Does anyone know where these central control rooms are located?

From:
http://cryptome.org/eyeball/daiichi-npp3/daiichi-photos3.htm
See: pic41.jpg [EDIT: sixth photo from top]
Caption of above:
"In this photo released by Tokyo Electric Power Co., the central control room of Unit 3 is pictured after lights went on while that of Unit 4, left side, is still dark at the Fukushima Dai-ichi nuclear power plant in Okumamachi, northern Japan Tuesday, March 22, 2011. (Tokyo Electric Power Co. via Kyodo News)"

If my annotations on pict41[zoom].JPG are correct, there has been a significant dislocation caused by the quake.

.

 

[PietKuip]

Just because high dose material has been found on the site is not surprising. The destroyed building next to the unit 3 reactor building is the radwaste building. Also I would not be suprised if the u3 and u4 fuel pool demineralizers were damaged in the explosions. Radioactive does not mean fuel is flung around the site. It doesn't take a lot of co60 to provide a 1 sievert source.

I do not know what fragments of demineralizers might look like, but I would be surprised if it could be described as pieces of concrete.

This is not something that would be lying about. If it is a normal part of the plant, it would be shielded by a lot of concrete, steel, or lead.

It might also be something that radioactive cesium or iodine vapors had sublimated on, or that a radioactive liquid had evaporated from, after the earthquake before the explosion.

So there are several possibilties. Maybe they did find out what it was - they moved it a day after it had been found.

 

[|Fred]

What might be a reasonable estimate of the extra dose in Tokyo? I think 1 mSv might be a reasonable order of magnitude (about a year of 0.1 microSievert per hour, on average). With 10^7 people that gives 10^4 man-Sievert, about 100 deaths.

If I understood the couple of paper I read, right (UNSCEAR). Sources, Effects, and Risks Of Ionizing Radiation, BEIR, ircrp, EPA 402-R-93-084, and envhper00536-0363.
Basicaly we have a measured risk factor from one shoot ionization >0.1 Sv <1Sv between 0.11 et 0.06 % for adults. When it comes to over time rather that one shoot either we arbitrary reset the counter every year or we apply a damping factor and the risk factor is dropped to 0.05 to 0.02. (doing so we diverge already from the LNT)

But this is still for >0.1 Sv <1Sv dose , as for extra the 1mSv/year we don't know as we rather have data suggesting it won't make a difference.

 

[|Fred]

I was going to do a large-scale plant layout in 3D until I saw someone beat me to it.

that's impressive 3d skills

Japan admits daily radioactive release from Fukushima many times higher than previously announced — Nuclear commission blames calculation error

It was my understanding that when you were talking of Becquerel one should always specify isotope, If I understood right INES requested(converting cesium amount into iodine equivalent).
This will give a bigger number alright but this has nothing to do with calculation error but only with the difference of half live between the cesium and iodine.

I'm I failing somewhere ? Is the press making something hudge out tomatoe/tomatoe

ps: what I do not understand is why the need to convert converting cesium amount into iodine equivalent.. regardless of the cesium or iodine 1 Becquerel will produce the same amount of ionization energy wouldn't it?

 

[razzz]

Don't know if these have been mentioned:

"The government is considering building an underground barrier near the Fukushima No. 1 nuclear power plant to prevent radioactive material from spreading far from the plant via soil and groundwater, a senior government official said."

Reactor 1 already half-entombed with water:
"At a press conference held Friday, TEPCO said it believed pressure suppression pools at the bottom of the No. 1 reactor's containment vessel were full of water, and that the top section of the containment vessel was about half full. Under normal circumstances, the pressure suppression pools are about 50 percent full with water."

http://www.yomiuri.co.jp/dy/national/20110423dy01.htm

What a logistics nightmare that would be. This site was chosen for it's bedrock almost an outcropping which means the foundations were poured on stable rock and not sand or organic soils. If they didn't prepare the bedrock by actually blasting or jack-hammering to level an area before laying forms and pouring concrete directly on bedrock then they filled on top of the bedrock with smaller rocks to make level a pad for pouring a monolithic floating building(s).

Now they want to dig back down to bedrock and pour concrete footings (walls) directly attached to bedrock in some form or fashion for a watertight perimeter/barrier around all four units. If the original geological reports showed little or no fractures in the bedrock then it might be possible provided you can deal with contaminated ground and seawater entering the excavation until you can get a clean prepared surface to pour concrete on or into. Might even drill into bedrock for anchoring down and/or notching to place a proper water barrier.

At least might be done in a suitable working environment away from 3 cores and one pond if contaminated water can be kept under control by de-watering (more pumping into the ocean). Not as desperate a plan as dropping seawater from choppers. Securing SFP 4 still takes precedences the way I see it. Unit 1 seems to at least hold water, 2 & 3 can only be flooded while waiting for consistent water levels and cool downs. Either the water levels go up or the fuel rods meltdown to form a happy medium (steam versus water cooling).

For now I would think higher liquid and ground contamination readings in the event of water encasement lessening the air contamination.

 

[clancy688]

Well, yes. TEPCO says 3.7e+17 Bq, and there's 3.7e+10 Bq/Ci.

That number is already converted into I131-equivalence. The actual, measurable activity is 1.4e+17 Bq.
But that's still 40% of 10.000.000 Curie.

@tsutsuji
Your leaving of this forum / discussion really is a pity. I always liked to read your posts, they were well structured and you always had good sources at hand.

 

[MiceAndMen]

From Cainnech's post #4653:
https://www.physicsforums.com/showpost.php?p=3262389&postcount=4653

"TEPCO suspects that the water leaked from the RPV is leaking through the cracks in the wall that separates the Reactor 3 turbine building and the Reactor 4 turbine building."

Could the features I have noted in the photos below possibly be evidence of the size of the "cracks" between the two turbine buildings? Does anyone know where these central control rooms are located?

From:
http://cryptome.org/eyeball/daiichi-npp3/daiichi-photos3.htm
See: pic41.jpg [EDIT: sixth photo from top]
Caption of above:
"In this photo released by Tokyo Electric Power Co., the central control room of Unit 3 is pictured after lights went on while that of Unit 4, left side, is still dark at the Fukushima Dai-ichi nuclear power plant in Okumamachi, northern Japan Tuesday, March 22, 2011. (Tokyo Electric Power Co. via Kyodo News)"

If my annotations on pict41[zoom].JPG are correct, there has been a significant dislocation caused by the quake.

.

I doubt very much that the control centers for 2 reactors would share the same physical space. One wouldn't want the situation of one reactor to distract the operators of another. The caption on that photo is probably incorrect.

Having said that, the floor does look dislocated. It could be due to structural damage from the earthquake, or simply part of a raised floor that collapsed. Many mainframe computer rooms have raised floors with space underneath for cables. It wouldn't surprise me if NPP control room floors are similar. In any case, as I said above, I find it highly unlikely that 2 control rooms would be adjacent to each other in a single enclosed space. There are no great building layout plans or diagrams that show where the individual control rooms are for each reactor that I have seen.

 

[kujala]

A couple of notes from this good document:
http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/f12np-gaiyou_e.pdf

1. Page 22: "Treatment of sub-drainage water after being pumped up"
So this is really all TEPCO can do about the underground water. They must pump it up from the unit 1 - 4's sub-drainage pits and handle it.
But please note this only concerns the water that has been accumulated in the sub-drainage pits.
I guess the contaminated water from the plant may find some routes below the level where the sub-drainage systems are working. And below that level you cannot really do anything.
And there is also a massive load of tsunami waters in the area which has affected the groundwater levels. What happens to the sub-drainage systems if there is "too much" water for them to handle? Anybody knows?
I am really amazed by the fact that TEPCO has been so quiet about the level of water in the unit 1 - 4's sub-drainage pits and also that they have not stated when they are going to empty them.

BTW, on the 5th of April they emptied 1 500 tons of water from the unit 5 - 6's sub-drain pits to the sea, according to IAEA. This water was low-level contaminated:
http://varasto.kerrostalo.huone.net/salaojat_1.png

2. Page 28: A really cool picture about how far the tsunami waters traveled in the Daiichi and Daini plants.

 

[|Fred]

I doubt very much that the control centers for 2 reactors would share the same physical space. .

they do , you can google it out :)

"photo shows the control room for the No.3 and No.4 reactors at the quake-hit Fukushima Daiichi Nuclear Power Station in Fukushima Prefecture at 11:28 p.m. on March 22, 2011. Lighting has been restored in the right side of the control room serving the No.3 reactor, while the left side remained dark for the No. 4 reactor. (Photo provided by Tokyo Electric Power Co.)(Kyodo)"

 

[dh87]

It was my understanding that when you were talking of Becquerel one should always specify isotope, If I understood right INES requested(converting cesium amount into iodine equivalent).
This will give a bigger number alright but this has nothing to do with calculation error but only with the difference of half live between the cesium and iodine.

I'm I failing somewhere ? Is the press making something hudge out tomatoe/tomatoe

ps: what I do not understand is why the need to convert converting cesium amount into iodine equivalent.. regardless of the cesium or iodine 1 Becquerel will produce the same amount of ionization energy wouldn't it?

Not exactly. A Bq is one decay per second of whatever is decaying. For tritium, one decay is one beta particle with an energy of 5.7 keV. For phosphorus-32 (chosen because it's simple), one decay is a beta particle with an energy of 1700 keV. These are very different amounts of ionization energy per decay and have vastly different biological effects. Cs-137 and I-131 are similar in total decay energy (around 1000 keV), but the pathways are complicated with branches and betas and gammas. I'm not sure how to compare them.

 

[MiceAndMen]

they do , you can google it out :)

"photo shows the control room for the No.3 and No.4 reactors at the quake-hit Fukushima Daiichi Nuclear Power Station in Fukushima Prefecture at 11:28 p.m. on March 22, 2011. Lighting has been restored in the right side of the control room serving the No.3 reactor, while the left side remained dark for the No. 4 reactor. (Photo provided by Tokyo Electric Power Co.)(Kyodo)"

Interesting if true, but the dark side of the room on the left looks nothing like the right side. Look at the ceiling, there is no symmetry whatsoever. Furthermore, reactor #4 trailed behind #3 in construction and operation by 1.5 years. One would have to show more than a single photo to make be believe it is true. Always happy to be proven wrong

 

[Dmytry]

I doubt very much that the control centers for 2 reactors would share the same physical space. One wouldn't want the situation of one reactor to distract the operators of another. The caption on that photo is probably incorrect.

Why so? It would make commercial sense; during normal operation it would allow same number of trained staff to run 2 reactors rather than one. Sure, during a disaster that is not very good, but during normal operation that reduces staffing requirements.

 

[MiceAndMen]

Why so? It would make commercial sense; during normal operation it would allow same number of trained staff to run 2 reactors rather than one. Sure, during a disaster that is not very good, but during normal operation that reduces staffing requirements.

It does not make safety sense.
http://www.nrc.gov/reactors/operating/ops-experience/control-room/ml013100014.pdf

Releases of hazardous chemicals can result in the control room becoming uninhabitable.

Do you really think an operator would risk having to abandon control operations for 2 reactors because 1 had a problem? I sure don't. It would be madness.

Edit: OK, I guess it does happen.

http://books.google.com/books?id=XI...=reactors share "single control room"&f=false

If I was in charge, it would be prohibited. I think it's a really dumb idea, and if regulators agree to an arrangement such as that, then the regulators IMO need to be replaced.

 

[clancy688]

It was my understanding that when you were talking of Becquerel one should always specify isotope, If I understood right INES requested(converting cesium amount into iodine equivalent).
This will give a bigger number alright but this has nothing to do with calculation error but only with the difference of half live between the cesium and iodine.

I'm I failing somewhere ? Is the press making something hudge out tomatoe/tomatoe

Yeah, you're right. If I understand the press reports correctly, there are releases of 0.69 TBq I131 and 0.14 TBq C137. That's the measurable activity. So all in all, you have 0.83 trillion decays per second, most of it I131. Telling that there are releases of <1 TBq/h is not wrong. If you convert it into equivalence, you'll get 6.4 TBq/h... in my opinion there's no mistake.
I get the impression that soon there will be some chaos regarding actual activity or I131-equivalence activity in the media.
They should just report I131 and C137 separately...

ps: what I do not understand is why the need to convert converting cesium amount into iodine equivalent.. regardless of the cesium or iodine 1 Becquerel will produce the same amount of ionization energy wouldn't it?

The conversion is used to get a standard of how dangerous an isotope is. Krypton-85 for example emits beta particles and has a half time of 10 years, plus there's much of it inside a nuclear reactor. But it isn't very dangerous because it has a very, very fast biological half life and stays in the atmosphere without contaminating anything.

Then we have I131 and C137. If there's a mass of I131 with an activity of 1000 Bq and a mass of C137 with an activity of 1000 Bq, then both are equally dangerous. But after a year there's virtually 0 Bq of that I131 left, so it's not dangerous anymore. But the 1000 Bq mass of C137 has still an activity of nearly 1000 Bq - because it has a half time of 30 years. And because there are MUCH more atoms released as for I131.

Basically, converting activity into an equivalence is done to express the danger of an isotope over a large timeframe - while the activity in Bq only describes the danger during the exact second of the measurement.

 

[Dmytry]

Not exactly. A Bq is one decay per second of whatever is decaying. For tritium, one decay is one beta particle with an energy of 5.7 keV. For phosphorus-32 (chosen because it's simple), one decay is a beta particle with an energy of 1700 keV. These are very different amounts of ionization energy per decay and have vastly different biological effects. Cs-137 and I-131 are similar in total decay energy (around 1000 keV), but the pathways are complicated with branches and betas and gammas. I'm not sure how to compare them.

same Bq amount of Cs-137 is 1360 times more atoms than I-131 , so in a long timespan, it is a lot more decay energy. E.g. over 30 years it is 680 times more energy.

It does not make safety sense.
http://www.nrc.gov/reactors/operating/ops-experience/control-room/ml013100014.pdfDo you really think an operator would risk having to abandon control operations for 2 reactors because 1 had a problem? I sure don't. It would be madness.

Totally and wholeheartedly agreed. But look, it's exactly what happened there. Spent fuel in pool in #4 somehow got uncovered (official version is that it was a hydrogen explosion, which requires fuel to overheat) as they had trouble enough with 3 reactors.

Edit: OK, I guess it does happen.

http://books.google.com/books?id=XI...=reactors share "single control room"&f=false

If I was in charge, it would be prohibited. I think it's a really dumb idea, and if regulators agree to an arrangement such as that, then the regulators IMO need to be replaced.

Well, if something makes commercial for-profit sense, it can be expected to happen. I don't know how exactly nuclear industry got some reputation to be different. The null hypothesis should have been that it's just like everything else but with a fairly small profit margin hence lower tolerance of operational inefficiencies such as that. Of course there is regulation but the efficacy of regulation is unclear; the number of reactors worldwide is small enough as to preclude empirical evaluation of safety.

 

[AntonL]

in continuation of https://www.physicsforums.com/showthread.php?p=3259145", Jiji press reports
http://jen.jiji.com/jc/eng?g=eco&k=2011042400085"
As of October 2010, there were some 4,000 cows, 30,000 pigs, 630,000 chickens and 100 horses in the off-limits zone.

 

[MiceAndMen]

Well, if something makes commercial for-profit sense, it can be expected to happen. I don't know how exactly nuclear industry got some reputation to be different. The null hypothesis should have been that it's just like everything else but with a fairly small profit margin hence lower tolerance of operational inefficiencies such as that. Of course there is regulation but the efficacy of regulation is unclear; the number of reactors worldwide is small enough as to preclude empirical evaluation of safety.

True enough, Dmytry.

I was searching for more information on shared control rooms and found some really disturbing data re. modernizing them with touch screens and Windows. I had to stop reading. Radiation-hardened microprocessor systems are used in spacecraft , but their cost is orders of magnitude beyond commercial off-the-shelf systems. I shudder to think about NPPs controlled by off-the-shelf hardware and software. In fly-by-wire aircraft, there is a mechanical override system to drop the landing gear if the electronics fail. Do I trust GE/Hitachi/Toshiba/etc. to build in the same safety margins for NPP control systems? No.

NPP safety systems and design could fill an entire separate thread.

 

[AntonL]

Fukushima crisis initially categorized as 'incident,' not accident

Officials of the Nuclear and Industrial Safety Agency (NISA) initially did not believe that events at the Fukushima No. 1 nuclear power plant after the March 11 Great East Japan Earthquake were serious enough to be categorized as an accident...

http://www.asahi.com/english/TKY201104230229.html

 

[Dmytry]

True enough, Dmytry.

I was searching for more information on shared control rooms and found some really disturbing data re. modernizing them with touch screens and Windows. I had to stop reading. Radiation-hardened microprocessor systems are used in spacecraft , but their cost is orders of magnitude beyond commercial off-the-shelf systems. I shudder to think about NPPs controlled by off-the-shelf hardware and software. In fly-by-wire aircraft, there is a mechanical override system to drop the landing gear if the electronics fail. Do I trust GE/Hitachi/Toshiba/etc. to build in the same safety margins for NPP control systems? No.

NPP safety systems and design could fill an entire separate thread.

Well, airplanes got higher profit margin. Even then, critical airplane software is also not so great, especially in the military.
Some navigation or clock related bug took out all the avionics in f22 when crossing international date line, for example. After the crash, it could not be resolved with reset switch, and the planes barely made it back to US.
Off the shelf software may have higher number of bugs per line, but it is engineered to mitigate effects of such bugs (f/e bug in messenger won't bring your web browser down, or vice versa). Be careful what you ask for. Windows and other off the shelf software may well end up being a lot safer than some homebrew systems. The userbase of critical safety rate software - such as avionics - is more vendor locked, meaning that the negative effects of the glitches on the profit are less significant and there exist a higher threshold under which bugs have virtually no effect on the profit. Furthermore, the tolerance to security vulnerabilities is much, much lower. A nuclear power plant using windows would probably be getting infected with some regular malware long before it would get infected by something like stuxnet. You would have some warning at least, even though it won't help if you ignore it.

 

[MiceAndMen]

By way of example, here is why I take everything released by NHK, TEPCO, and the Japanese government with a large grain of salt.

http://www3.nhk.or.jp/daily/english/24_12.html

If you believe that video, then you also believe the SFP at Unit 4 is on the North side of the building. We know that to be false.

 

[MadderDoc]

<..> Can someone tell us more about "radwaste buildings" please?

http://i306.photobucket.com/albums/nn270/tcups/4000d390.png

The Centralized Radiation Waste Treatment Facility is the complex of buildings to the south of unit 4. It is separated from the area around unit 4 by a road leading to the sea. The treatment facility has 4 main buildings: the Process
Main Building, the Miscellaneous Solid Waste Volume Reduction Treatment Building, the On-site Bunker Building, and the Incineration Workshop Building. You will see on photos, that the buildings of the treatment facility is intricately connected to the southernmost exhaust stack of the plant.

According to plans, the highly contaminated water from the turbine building of unit 2, including the famous trench, is to be pumped to the Process Main Building of the treatment facility (since that building has the largest capacity for storage). I suppose the Process Main building is the large building to the seaside of the complex.

Transfer of the contaminated water via hoses involves crossing two roads, the road between unit 2 and 3, and the road between unit 4 and the treatment facility. It also involves passing _through_ turbine building 3 and 4 (for the purpose, a hole has been made in the walls between the two turbine buildings).

 

[htf]

Well, airplanes got higher profit margin.

Do they? I don't think so. Compare the prices for electrical power in France and Germany. They are much higher in Germany. Without taxes 1 kWh costs in Germany ~14 Cent and in France 9 Cent. The difference is attributed to the higher percentage of nuclear power in France. So running a NPP must be quite profitable - for the power companies.

In fly-by-wire aircraft, there is a mechanical override system to drop the landing gear if the electronics fail.

That doesn't help much if the overall design has a single point of failure. There was an incident with a British Eurofighter where the nose landing gear could not be dropped. The reason was a ill designed locking mechanism and manufacturing problems. The emergency release mechanism didn't work because it was just an other way to actuate the locking mechanism which was blocked.

Safety is a difficult issue and you cannot reduce it to mechanics vs electronics.

 

[gmax137]

Some multi-unit sites have shared control rooms, some don't. There are pros and cons to each approach. Pro: It may be helpful to know firsthand what is going on with the other unit, some plant equipment may be shared between the units (eg, security, non-nuclear water treatment, etc.). Con: potential single point vulnerability affecting both units, potential distractions, etc. Most of the sites try to minimize the cons. For example, when one unit is down for an outage there is more activity (as maintenance crews request systems to be realigned for their work) -- nowadays this is usually re-located to another room to prevent it from distracting the operators on the boards.

Why so? It would make commercial sense; during normal operation it would allow same number of trained staff to run 2 reactors rather than one. Sure, during a disaster that is not very good, but during normal operation that reduces staffing requirements.

This simply isn't the way it's done, at least in the plants I been to. The individual operators are assigned to one unit or the other, a two-unit control room has twice the operators as a one unit facility. And if you haven't been inside one of these control rooms you may have misconceptions as to what they are like. They are run with an essentially military protocol; they are quiet, organized, regimented places. Many (most?) of the operators are ex-navy reactor operators. At least that's how it is in the ones I've been to.

 

[Dmytry]

Do they? I don't think so. Compare the prices for electrical power in France and Germany. They are much higher in Germany. Without taxes 1 kWh costs in Germany ~14 Cent and in France 9 Cent. The difference is attributed to the higher percentage of nuclear power in France. So running a NPP must be quite profitable - for the power companies. That doesn't help much if the overall design has a single point of failure. There was an incident with a British Eurofighter where the nose landing gear could not be dropped. The reason was a ill designed locking mechanism and manufacturing problems. The emergency release mechanism didn't work because it was just an other way to actuate the locking mechanism which was blocked.

Safety is a difficult issue and you cannot reduce it to mechanics vs electronics.

Well according to most estimates nuclear is more expensive:
http://en.wikipedia.org/wiki/File:Nuke,_coal,_gas_generating_costs.png
mechanics: totally agreed. Consider those triple or however many times redundant control rod insertion mechanisms. Core shroud fails and all of them may get stuck. There are inspections to safeguard against this:
http://www2.jnes.go.jp/atom-db/en/trouble/ines_special/measure01.htm
The inspection records for core shroud were faked in the past; there is a huge short term commercial incentive to fake maintenance records.

gmax137: well, I would think there are big cultural differences between countries. There is a clear commercial incentive to try to cut down the spendings. It is of course off topic for this thread, but the economical/business considerations seem to ultimately determine cost/safety tradeoff of the plant. By careful scheduling you can probably cut down the personnel 1.5x at least, and that's the way it would be done if it was something less dangerous - and similarly it is the way it would be done if nuclear was seen as very safe and automatic systems as infallible.

 

[jlduh]

Well, after SFP with no other containment than water at the top floor just above the reactors, i discover that info: ONE control room for TWO reactors!

Great stuff from safety standpoint, really, in my own opinion.

Tsutsuji really a pity if you leave the forum because you brought some good stuff and you can translate from japanese to english which is very valuable. I appreciated much the site you linked on the simulation in ocean dispersion, so don't be too upset about what happened to your post (even if a small message in MP is always a good thing to explain the why, i got one from Borek 3 weeks ago for a similar reason and everything went fine).

That's a good opportunity to remember everyone that this message of Borek 3 weeks ago lead me to create a new thread on the more "political aspects" of the accident, it's here:

https://www.physicsforums.com/showthread.php?t=486089So feel free to feed it with your reflexions and infos.

Now, it is obvious that as i mentioned, "pure facts" without opinions are almost impossible to achieve on this Fukushima subject, essentially because most of the materials we get is released from essentially one single source (Tepco) which proved several times to be either fuzzy, incomplete or wrong (not to say thay can also be communication politics)... Plus "science without conscience is..." , and i agree, and can be acceped also i think by many here. The problem is more when things turn into too personal disputes on specific matters, then i understand moderation action: some control rods need to be inserted time to time in order to avoid chain reactions

Just a precision concerning the highly contaminated debris found and measured: that's the first time they talk aout one clearly measured but it's not the first time the presence of highly contaminated debris scattered around is revealed, that was said in one of the articles i cited on the "more political thread":

http://english.kyodonews.jp/news/2011/03/82005.html

From one worker there:

Within the plant's premises, rubble with highly radioactive materials was scattered after hydrogen explosions at reactor building in the days after the quake. ''If they are removed soon by heavy machinery, work will be a lot easier but the operator (of the machines) will inevitably be exposed to radiation,'' the man said.

Some more on this, just released, with a Tepco map of various debris on site:

http://www3.nhk.or.jp/daily/english/24_08.html

VERY UNFORTUNATELY, the maps is quickly shown and i didn't find this map on Tepco site (until now)...

 

[AntonL]

http://www3.nhk.or.jp/daily/english/24_12.html"

TEPCO initially planned to install tanks with a capacity of 27,000 tons by the end of May. However, the company is now planning to construct 31,400 tons of storage capacity by early June.

In addition, the company plans to add tanks with a total capacity of 20,000 tons every month from June to December in case the water filtration and cooling systems cannot start operating on schedule in June.

Is this the first admission of Tepco that secondary cooling system is not or never going to work and "feed and bleed" will continue

 

[clancy688]

Well, after SFP with no other containment than water at the top floor just above the reactors, i discover that info: ONE control room for TWO reactors!

The Czech can top that. One reactor building for two reactors (without a containment):

http://en.wikipedia.org/wiki/Dukovany_Nuclear_Power_Station

 

[Dmytry]

Well, after SFP with no other containment than water at the top floor just above the reactors, i discover that info: ONE control room for TWO reactors!

Great stuff from safety standpoint, really.

you forgot to mention spent fuel pool re-racking and reliance on boral sheets to prevent criticality after re-racking.
Here you can read more about what boral is:
http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0933/sec3/196.html
Rest assured it is very safe, because, even though it was found to be bulging in an unexpected way, to the point of mechanical interference (aka **** getting stuck requiring force to move), they found clipping the corners prevents the bulging, and they had done a study which shows that unexpected bulging is not dangerous. Furthermore, of course, being submerged under water, boral won't melt. And they calculated it not to interfere with convection too much; during normal operation, there's no debris falling into the spent fuel pool blocking the flow on top of fuel assemblies, so it is all safe. Be assured that a few hundreds engineers have reviewed this, and have found it to be a safety neutral upgrade.
Also, check that out:
http://www.klimaatkeuze.nl/wise/monitor/574/5441

 

[Krikkosnack]

Fukushima crisis initially categorized as 'incident,' not accident

Officials of the Nuclear and Industrial Safety Agency (NISA) initially did not believe that events at the Fukushima No. 1 nuclear power plant after the March 11 Great East Japan Earthquake were serious enough to be categorized as an accident...

http://www.asahi.com/english/TKY201104230229.html

This is the first notations of tepco...
http://energheia.bambooz.info/index.php?option=com_content&view=article&id=108&Itemid=99&lang=it"

http://energheia.bambooz.info/index.php?option=com_content&view=article&id=119&Itemid=99&lang=it"

[As I explained earlier, feel free to discuss other matters in different threads, you can start them either in Nuclear Engineering or Politics & World Affairs subforums.

It is not about censorship, it is about keeping some order in the discussion. Putting everything into one thread means mess.

i agree with Borek.