Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[GJBRKS]

This chunk was emitting 900 mSv per hour. Workers received 3.17 mSV getting it into a container. This thing was DANGEROUS. It hasn"t been lost. They know where it is.

They were trying to clear debris near the switchyard, probably so they can continue restoring power to equipment that still may be operable and can help stabilize the plant. Our wishes for more information pale in importance to what they are trying to do. With junk like this lying around these people are risking their lives. Give them a break.

Perspective, please!

We got the info that this could not have been volatile iodine or cesium , so the explosions have ejected highly radioactive content , from core or spent fuel pool.

As the NRC has stated before

 

[Samy24]

This chunk was emitting 900 mSv per hour. Workers received 3.17 mSV getting it into a container. This thing was DANGEROUS. It hasn"t been lost. They know where it is.

They were trying to clear debris near the switchyard, probably so they can continue restoring power to equipment that still may be operable and can help stabilize the plant. Our wishes for more information pale in importance to what they are trying to do. With junk like this lying around these people are risking their lives. Give them a break.

Perspective, please!

I'm quite sure you misunderstood me. I do not want to engage any worker at the site. Most of them do likely know at what danger they are even if TEPCO told them there is no health risk.
So what do you mean with "Perspective, please" (English is not my native language)

We want to analyse what this piece is and where it is from. Normaly concrete is not radioactive in a "normal" power plant. That's it.

 

[ascot317]

[...]That is why one has robots.[...]

Problem is, they lack highly specialised robots for this sort of work, or even an onsite lab. And this is not going to change anytime soon.
Even if they wanted to, they can't, unless they finally decide to accept foreign help.
So, there's only more of this to come, people being accidently exposed by pieces of "something" lying around. 900mSv/h by concrete is so weird, wherever this came from, there is likely something even more active, rather close. Will Tepco finally admit that things got out of control?

 

[dh87]

"the concrete block has been stored safely in a container with other debris"

Don't they want to know what it is?

Concrete does not get this radioactive by neutron activation.
It seems to me there must have been some corium on this piece.

So where is the rest?

I think that vaporized Cs or CsI could be deposited on concrete at very high levels. The numbers provided are hard to interpret without a distance and without isotopic composition.

If this were all I-131, and it were a point source, and they measured it from 10 cm, I calculate that it would correspond to 4.5 Curies of I-131 (based on 1mCi of I-131 giving 2.2 R/hr at 1 cm from here: http://www.stanford.edu/dept/EHS/prod/researchlab/radlaser/RSDS_sheets/I-131_Inorganic.pdf).

 

[mscharisma]

...
This forum is interesting and informative. If we can all keep the rhetoric down and respect each other we will have a much better chance of making this forum useful. We’ve already seen one thread shutdown, we all lose when that happens. You seem to see things so clearly, but you lose any chance of persuasion when you belittle others or call them stupid, or liars. Come on in, the water is fine, even if it glows in the dark. Peace?

Bravo! I wish more people on this planet would think the way you do. Very well said.

 

[NUCENG]

We got the info that this could not have been volatile iodine or cesium , so the explosions have ejected highly radioactive content , from core or spent fuel pool.

As the NRC has stated before

My apologies if I stepped on your toes. I saw PietKuip ask "Don't they want to know what it is?" And in fact they probably do not care. That guy on the loader or crane and the technician monitoring radiation know that concrete is dangerous and in their way. They are working with dose limits and if they spend time studying a particular piece of debris they will soon be useless because they will be at their limits. These workers are trying to get the job done. They may never be able to return to their homes. When the site is stabilized they may be unemployed. Put yourself in their place. There is radioactivity in the air water and soil. There is sharp metal and debris all over the place. There is more debris hanging perilously over head. It could be corium, it could be a piece of spent fuel blown out of a fuel pool. It may be a hot piece of Cesium or irradiated steel, or a spec of cobalt-60.

It seems that there are more and more people on this site that really believe TEPCO is lying about everything. That was reinforced today when the government of Japan took over the PR communications role. We'll have to wait and see if that improves anything. I am also sensitive to a tendency to project the distrust and contempt on the workers, and I may have over-reacted if that wasn't what you and Piet were saying.

 

[Jorge Stolfi]

Has anyone heard an official explanation for the <1 atm pressures ?

Perhaps, but I am not aware of it.

My guess is that at some point the RPV had steam in its top part, water below, water in the drywell, and a leak between the two somewhere below the water line. As water was pumped into the RPV, some of the steam condensed, and the water lvel inside the RPV rose above that in the drywell.

But I do not know where the sensors are actually placed, so I would not bet a cent on this.

[..] the sensors are encased by condensed salt deposits.

AFAIK no active electronics are working anywhere near the reactor. I guess that the "pressure sensors" are merely tubes that extend from the reactor/containment (possibly through some sort of membrane that transmits pressure but not gas) to mechanical meters, located where they can be safely read (perhaps at the fire extinguisher line inlet -- anyone knows where that is?)

Ditto for the CAMS radiation meters --- AFAIK they are pipes that suck air samples from the reactor and take them to an external radiation counters. And I suppose that the temperature sensors are just thermocouples or temperature-sensitive resistors, each with two wires leading out of the reactor.

Can anyone confirm this?

 

[GJBRKS]

My apologies if I stepped on your toes. I saw PietKuip ask "Don't they want to know what it is?" And in fact they probably do not care. That guy on the loader or crane and the technician monitoring radiation know that concrete is dangerous and in their way. They are working with dose limits and if they spend time studying a particular piece of debris they will soon be useless because they will be at their limits. These workers are trying to get the job done. They may never be able to return to their homes. When the site is stabilized they may be unemployed. Put yourself in their place. There is radioactivity in the air water and soil. There is sharp metal and debris all over the place. There is more debris hanging perilously over head. It could be corium, it could be a piece of spent fuel blown out of a fuel pool. It may be a hot piece of Cesium or irradiated steel, or a spec of cobalt-60.

It seems that there are more and more people on this site that really believe TEPCO is lying about everything. That was reinforced today when the government of Japan took over the PR communications role. We'll have to wait and see if that improves anything. I am also sensitive to a tendency to project the distrust and contempt on the workers, and I may have over-reacted if that wasn't what you and Piet were saying.

I feel your concern towards the workers and I share your sentiments in this.
I don't think Piet meant to imply more than his own interest into this new piece of information.
You are probably right that this is not the first such an amount of debris that had to be handled to safety.
I guess I was somehow surprised by the amount of detail on this news item.

 

[NUCENG]

I'm quite sure you misunderstood me. I do not want to engage any worker at the site. Most of them do likely know at what danger they are even if TEPCO told them there is no health risk.
So what do you mean with "Perspective, please" (English is not my native language)

We want to analyse what this piece is and where it is from. Normaly concrete is not radioactive in a "normal" power plant. That's it.

Perspective is assigning importance only to the most important things. This thread and a lot of the media have focused attention on the nuclear disaster. But over a thousand Japanese were killed in the original earthquake and more than 20,000 were killed in the tsunami. The three deaths at Fukushima were due to earthquake and tsunami.

We have been debating what might have been done to prevent the accident. But that is hindsight - taking credit for knowledge of what did happen, where the only real accomplishment would have been figuring out what could happen before it did.

The easy answers are usually wrong. That is what I mean by perspective. Please don't apologize for your knowledge of English, it is my native language and sometimes I can't figure out what to say or how to say it.

I was stationed in Japan in the US military for three years. I wish there was more that I could do to help them out. They may have made some mistakes. Some of them may have deliberately lied. Hey, they are human. And right now they really don't need criticism as much as they need support.

 

[PietKuip]

My apologies if I stepped on your toes. I saw PietKuip ask "Don't they want to know what it is?" And in fact they probably do not care. That guy on the loader or crane and the technician monitoring radiation know that concrete is dangerous and in their way. They are working with dose limits and if they spend time studying a particular piece of debris they will soon be useless because they will be at their limits. These workers are trying to get the job done. They may never be able to return to their homes. When the site is stabilized they may be unemployed. Put yourself in their place. There is radioactivity in the air water and soil. There is sharp metal and debris all over the place. There is more debris hanging perilously over head. It could be corium, it could be a piece of spent fuel blown out of a fuel pool. It may be a hot piece of Cesium or irradiated steel, or a spec of cobalt-60.

It seems that there are more and more people on this site that really believe TEPCO is lying about everything. That was reinforced today when the government of Japan took over the PR communications role. We'll have to wait and see if that improves anything. I am also sensitive to a tendency to project the distrust and contempt on the workers, and I may have over-reacted if that wasn't what you and Piet were saying.

What I was trying to say is that Tepco should want to know what the debris is. The workers should have been instructed to leave material alone that is making their < 1000 mSv/h dose meters almost go off scale. Such stuff should not be handled by humans.

I pity the workers. I have contempt for the Tepco upper management. They even cut the wages of the workers, because the Fukushima Daiichi plant is not making a profit.

 

[GJBRKS]

AFAIK no active electronics are working anywhere near the reactor. I guess that the "pressure sensors" are merely tubes that extend from the reactor/containment (possibly through some sort of membrane that transmits pressure but not gas) to mechanical meters, located where they can be safely read (perhaps at the fire extinguisher line inlet -- anyone knows where that is?)

In that case it might be that the 'calibrated' side of the membrane has been compromised by an overpressure , reducing the readings of the 'inner' side's pressure ...
Thanks for that update

 

[Samy24]

Perspective is assigning importance only to the most important things. This thread and a lot of the media have focused attention on the nuclear disaster. But over a thousand Japanese were killed in the original earthquake and more than 20,000 were killed in the tsunami. The three deaths at Fukushima were due to earthquake and tsunami.

We have been debating what might have been done to prevent the accident. But that is hindsight - taking credit for knowledge of what did happen, where the only real accomplishment would have been figuring out what could happen before it did.

The easy answers are usually wrong. That is what I mean by perspective. Please don't apologize for your knowledge of English, it is my native language and sometimes I can't figure out what to say or how to say it.

I was stationed in Japan in the US military for three years. I wish there was more that I could do to help them out. They may have made some mistakes. Some of them may have deliberately lied. Hey, they are human. And right now they really don't need criticism as much as they need support.

No problem I'm not so sensetive about a good discussion.

If you delete all the speculation in this thread, only half a dozend posts would be left :)

If you permit a more private question? You mentioned in one of your posts that you were exposed to about 75 mSv. Was this by an accident? Normally workers should not get that dose.

 

[NUCENG]

What I was trying to say is that Tepco should want to know what the debris is. The workers should have been instructed to leave material alone that is making their < 1000 mSv/h dose meters almost go off scale. Such stuff should not be handled by humans.

I pity the workers. I have contempt for the Tepco upper management. They even cut the wages of the workers, because the Fukushima Daiichi plant is not making a profit.

You are right. I would also like to know what it is. I overreacted and apologize for thinking you were criticizing the workers. Normally I edit my posts offline and have a chance to tone them down before I send them. I should go back to that routine.

The Wall Street Journal had a front page story today that Operators wanting to start depressurizing the Unit 1 containment before it overpressurized had to get permission from TEPCO management and they had to get high level government permission. Maybe it isn't TEPCO management to blame, but a culture in Japan which discourages individial initiative and decision-making.

 

[MadderDoc]

Below is the recorded sprayings to the spent fuel pool of unit 4 (data from Tepco press releases). The intensity of topping the pool appears to have increased lately. Similar data regarding the other SFPs can be found at:
http://www.gyldengrisgaard.dk/fuku_docs/fuku_sfp_sprayings.html

SFP4:
Concrete pump 23 April 2011 12:30-?
Concrete pump 22 April 2011 17:52-23:53
Concrete pump 21 April 2011 17:14-21:20
Concrete pump 20 April 2011 17:08-20:31
Concrete pump 19 April 2011 10:17-11:35
Concrete pump 17 April 2011 17:39-21:22
Concrete pump 15 April 2011 14:30-18:29
Concrete pump 13 April 2011 00:30-06:57
Concrete pump 9 April 2011 17:07-19:24
Concrete pump 7 April 2011 18:23-19:40
Concrete pump 5 April 2011 17:35-18:22
Concrete pump 3 April 2011 17:14-22:16
Concrete pump 1 April 2011 08:28-14:14
Concrete pump 30 March 2011 14:04-18:33
Concrete pump 27 March 2011 16:55-19:25
Injection of seawater through FPCFS 25 March 2011 06:05-10:20
Concrete pump 25 March 2011 19:05-22:07
Concrete pump 24 March 2011 14:35-17:30
Concrete pump 23 March 2011 10:00-13:00
Concrete pump 22 March 2011 17:20-20:30
Water spray by the Self Defence Force 21 March 2011 06:37-08:41
Water spray by the Self Defence Force 20 March 2011 08:21-09:40
Water spray by the Self Defence Force 20 March 2011 18:45-19:45
Explosion at unit 4 15 March 2011 06:00 appr.
Temperature in pool is 84 C 14 March 2011 04:08

 

[PietKuip]

Perspective is assigning importance only to the most important things. This thread and a lot of the media have focused attention on the nuclear disaster. But over a thousand Japanese were killed in the original earthquake and more than 20,000 were killed in the tsunami. The three deaths at Fukushima were due to earthquake and tsunami.

That is because this thread is not about drowning in tsunamis, or about civil engineering to diminish the impact of tsunamis.

The nuclear accident has made the coastal part of the prefecture unsuitable for habitation and agriculture. It has exposed many Japanese to increased levels of radiation. I have not seen any estimates yet of man-Sieverts, but I guess that calculations will show at least hundreds of deaths. As a comparison: Chernobyl is calculated to have given 5 000 man-Sievert in Sweden alone. Multiply that by 0.02 and it will give you an estimate of the number of Chernobyl casualties in Sweden.

 

[NUCENG]

No problem I'm not so sensetive about a good discussion.

If you delete all the speculation in this thread, only half a dozend posts would be left :)

If you permit a more private question? You mentioned in one of your posts that you were exposed to about 75 mSv. Was this by an accident? Normally workers should not get that dose.

The first submarine I was on had had an air accident which involved inadvertently adding a lot of air under pressure into the reactor while it was shutdown. I reported aboard shortly after that accident happened. There was no damage to the core or equipment but the air caused a significant pH transient which reeleased a lot of corrosion products from the walls of the vessel and piping and some of the oxide from the outside of the core. A lot of that contamination collected in the plants ion exchanger resin. Much of my exposure was during routine inspections and maintenace near the ion exchanger over a three year period. We had to deal with that until the submarine went into refueling and the ion exchanger resin was changed out.

 

[NUCENG]

They had been offered help from e.g. France and Germany, which they rejected. That and the problems that follow this decision can surely be critisized.
The local tech guys are surely doing everything they can within their capabilities (or even more), but I'm not so sure about the management. In Japan, pride plays a huge role. Imagine yourself in the role of a crisis manager (and I guess you're qualified to do that), would you have rejected the offer of such a highly specialised company like KHG?
People aren't so much worked up about the possibility of Tepco not telling the truth, they're more upset about them doing "stupid things" due to other reasons.
Incompetence, pride etc.

Either Tepco has, so far, released everything they know (which wouldn't be much), or they're holding things back.

Look at the little things we know and how much speculation this results in. Tepco could provide more information. They're not. This is making the industry look very bad.

OK let's look at this in terms of trying to influence someone into accepting help. I can walk up to you and say, "You are to stupid to do this right and you are lying if you disagree. I am here to help so go stand in the corner and stay out of my way." Should I exppect you to let me help you?

Alternatively I can say, "I know you are up to your neck in alligators, so I'll be brief. I have this alligator proof dredger. You can use it and Ill train your people to operate it. Here are the specs. Check it out when you have a chance. Let me know if there is anything else you need and I'll try to find it."

Is there valid criticism for TEPCO and Japanese ministries? YES. Is now the time to rub their nose in it? In my opinion, NO. Does that mean you are wrong? NO. It just means that I think there will be time for this after we drain the swamp.

 

[RealWing]

You are right. I would also like to know what it is. I overreacted and apologize for thinking you were criticizing the workers. Normally I edit my posts offline and have a chance to tone them down before I send them. I should go back to that routine.

The Wall Street Journal had a front page story today that Operators wanting to start depressurizing the Unit 1 containment before it overpressurized had to get permission from TEPCO management and they had to get high level government permission. Maybe it isn't TEPCO management to blame, but a culture in Japan which discourages individial initiative and decision-making.

I wondered about the approval hierarhy back when it ruptured. I don't know the US Regs, but in Canada in an post-accident event where you have to start a radioactive release to control pressure - it requires government approval. The utility does not have the authority to do this.
In this case, depressurizing meant they would have to release radioactivity to the environment at the same time and thus seemed to require higher level approvals? Due to compromized communications and maybe LTA emergency preparedness - it simply took too long to get approval?

If so, it would have been incredibly difficult to be the plant operators/managers sitting there watching the pressure rise waiting for the @#$%^ approval to come through!

 

[dh87]

If the pool becomes acidic Iodine gas will re-evolve and be released to the atmosphere. In other words it is not likely to go very far.

The concern that the water will become acidic has been raised several times in this thread, because acidic pH's would speed the oxidation of iodide to iodine, which is fairly volatile. If the water is acidic, the biggest problem may be dissolution of the concrete used to build almost everything at the reactor. Some people have also said that the use of seawater (pH around 8.0) will prevent this from happening.

First, I doubt that seawater is sufficiently buffered to prevent pH changes if there are acid- or base-generating reactions. Second, the chemistry suggests that there should be much more concern about very high pH than about low pH. One of the principal reactions that's occurred is oxidation of Zr by water, releasing hydrogen. ZrO2 is not very soluble in water. (In contrast, metallic Cs undergoes the same reaction with water, making Cs2O. Cs2O reacts with water, making CsOH, which is a powerful base.) ZrO2 could react with chloride in the water, making ZrCl4, which is soluble, and releasing hydroxide, raising the pH a lot. I suspect that this reaction was a much more serious issue when temperatures in the reactors were higher four weeks ago.

 

[tsutsuji]

Such stuff should not be handled by humans.

According to http://www.asahi.com/national/update/0423/TKY201104230396.html , after the discovery, the personnel was reduced to one man who used a "heavy machine" to take the radioactive debris to the container.

Perhaps that "heavy machine" is the "remote-controlled rubble removing equipment" shown on http://cryptome.org/eyeball/daiichi-npp6/daiichi-photos6.htm

 

[Samy24]

According to http://www.asahi.com/national/update/0423/TKY201104230396.html , after the discovery, the personnel was reduced to one man who used a "heavy machine" to take the radioactive debris to the container.

Perhaps that "heavy machine" is the "remote-controlled rubble removing equipment" shown on http://cryptome.org/eyeball/daiichi-npp6/daiichi-photos6.htm

NHK TEPCO says the workers were exposed to 3.17 millisieverts of radiation during the clean-up and the concrete block has been stored safely in a container with other debris.

If they take 3.17 mSv by using a "remote-controlled rubble removing equipment" the radiation in that area must be enormous.

 

[tsutsuji]

NHK TEPCO says the workers were exposed to 3.17 millisieverts of radiation during the clean-up and the concrete block has been stored safely in a container with other debris.

If they take 3.17 mSv by using a "remote-controlled rubble removing equipment" the radiation in that area must be enormous.

My guess is that they took 3.17 mSv before finding the debris.

 

[|Fred]

I have not seen any estimates yet of man-Sieverts.

There was 172,000 people in the 30 km evaluation zone, considering nearly all were in a 20 km zone and the rest was ask to stay indoors, considering current projection (by NNSA) for radiation dose for people not indoors not evacuated and staying or coming back for a year in the 30Km zone in currently around 20mSv .

Hopefully, according to current knowledge there should not be additional death due to ionization in the general population

 

[mscharisma]

I wondered about the approval hierarhy back when it ruptured. I don't know the US Regs, but in Canada in an post-accident event where you have to start a radioactive release to control pressure - it requires government approval. The utility does not have the authority to do this.
In this case, depressurizing meant they would have to release radioactivity to the environment at the same time and thus seemed to require higher level approvals? Due to compromized communications and maybe LTA emergency preparedness - it simply took too long to get approval?

If so, it would have been incredibly difficult to be the plant operators/managers sitting there watching the pressure rise waiting for the @#$%^ approval to come through!

The Wall Street Journal article addressing hierarchy/protocol for venting in Japan and in the US can be accessed here:
http://online.wsj.com/article/SB10001424052748703922504576273234110896182.html?KEYWORDS=fukushima

 

[MadderDoc]

Since April 1st Tepco has conducted sprayings to bind radioactive dust in certain problem areas. The efforts have been concentrated on the mountainsides behind the two buildings 'across the street' from unit 3 (the Common Spent Fuel Pool (CSFP) and the Medium Voltage Switchyard (MSV) respectively), and to the area around the Central Radwaste Treatment Facility (CHWTF), situated to the south of unit 4. (see attached annotated map)

21 April 2011: 1300 m² mountain side at the CSFP
21 April 2011: 5100 m² mountainside at MVS
20 April 2011: 1900 m² around the CHWTF
18 April 2011: 1200 m² at the CHWTF
17 April 2011: ? m² at the CHWTF
16 April 2011: 1800 m² mountainside at the CSFP
15 April 2011: 1900 m² mountainside at the CSFP
13 April 2011: 1600 m² mountainside at the CSFP
11 April 2011: 1200 m² mountainside at the CSFP
8 April 2011: 680 m² mountainside at the CSFP
5 April 2011: 550 m² east and south mountainside at the CSFP
1 April 2011: 500 m² mountainside at the CSFP

 

[RealWing]

Really? From what I've heard of German reactors, the operating manuals are to be obeyed, and when operator manual tells you to do something - e.g. to vent - it would take government approval not to vent. The automatic pressure relief valves surely don't ask for approval.

The operating manuals in this case are the Emergency Operating Procedures. They specifically tell you to get Gov't approval to vent. When we get that approval, we vent. So yes, I agree - follow procedures.

At our reactors in Ontario, Canada, we have a huge Vacuum Building (VB) that is kept under vacuum at all times and connected to each reactor. If a major rupture occurs, the steam etc is automatically sucked into the VB and doused with water which condenses the steam. This is all passive and no power is needed. At some point after that, the pressure inside our containment structure will approach atmospheric and venting will be required - primarily to ensure that all the radioactive material goes out through a monitored, hardened and filtered vent, instead of leaking out through unmonitored pathways in the containment structure.

 

[GJBRKS]

A friend in Japan tells me the officials are very reluctant to accept foreign help because of pride. They rather build their own robots. It surely is an insult for a pride high-tech-nation like Japan, who's relying so much on nuclear power and doesn't have their own robots to deal with such a crisis. Things are quite a bit different in Japan. If you haven't been there yet, it's worth a long trip (well... pack your dosimeter...).

Let's be carefull in assuming Japan doesn't accept help just to make a point :

- The Japanese government has expressed thanks to the USA for their crisis teams
- The French Areva will supervise the construction of a water decontamination site by a UK firm
- German concrete pump trucks are being flown in using a Russian Antonov
- American robots have surveyed the plants
- A Russian decontamination vessel is being transported to the site.
- An American barge has been used to store contaminated pump water
- The NRC has been doing crisis recommendations that up to now are being followed to the letter
( http://cryptome.org/0003/daiichi-assess.pdf : read the advised steps , and see that's exactly what TEPCO does or plans to do)

I'd say it is even particularly important for the government to show they are working with the USA , in order to prevent a popular backlash towards the ( after all) American imported technology

 

[PietKuip]

There was 172,000 people in the 30 km evaluation zone, considering nearly all were in a 20 km zone and the rest was ask to stay indoors, considering current projection (by NNSA) for radiation dose for people not indoors not evacuated and staying or coming back for a year in the 30Km zone in currently around 20mSv .

Hopefully, according to current knowledge there should not be additional death due to ionization in the general population

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.

 

[I_P]

My apologies if I stepped on your toes. I saw PietKuip ask "Don't they want to know what it is?" And in fact they probably do not care. That guy on the loader or crane and the technician monitoring radiation know that concrete is dangerous and in their way. They are working with dose limits and if they spend time studying a particular piece of debris they will soon be useless because they will be at their limits. These workers are trying to get the job done. They may never be able to return to their homes. When the site is stabilized they may be unemployed. Put yourself in their place. There is radioactivity in the air water and soil. There is sharp metal and debris all over the place. There is more debris hanging perilously over head. It could be corium, it could be a piece of spent fuel blown out of a fuel pool. It may be a hot piece of Cesium or irradiated steel, or a spec of cobalt-60.

It seems that there are more and more people on this site that really believe TEPCO is lying about everything. That was reinforced today when the government of Japan took over the PR communications role. We'll have to wait and see if that improves anything. I am also sensitive to a tendency to project the distrust and contempt on the workers, and I may have over-reacted if that wasn't what you and Piet were saying.

NUCENG, I truly appreciate your posts and those of others who have posted here with specific industry knowledge and/or perspective. It helps keep the discussion on track and informative. That said let me respond in a general way to you as a representative of your profession. Nothing personal intended or implied.

The death toll from the quake and tsunami is around 30,000 people. The exact figure is still climbing as it has been hard to determine the number of missing given the scale of destruction. Who knows how many will die when LA or San Fransisco or Lisbon or Tokyo (etc.) is shaken by another 'big one'. Human nature and behavior intersecting with natural forces that manifest sporadically, unpredictably (regarding the precise time of an event, not necessarily it's probability) and with great force - many types of examples come to mind here. However, this is quite a different matter from the accident at Fukushima.

The attitude of the staff and management at TEPCO was that such an accident was impossible and no preparations had been made or consideration given to the possibility. Training and equipment to deal with a serious accident was not implemented or acquired, one of the rationals being that to pursue such matters would show insecurity or fear and call into question the safety of nuclear plants.

The historical and scientific knowledge about tsunamis was not properly considered given the known risks to plants on the coast. It was stated that unit 1 was constructed with an 'off the shelf' plan from GE that wasn't modified to suit the site specific risks because the engineers were not familiar enough with plant design to confidently recommend changes to it. Once the first unit was built the following units were added using the same basic format, incorporating the same site-based flaws. This was not corrected later because of cost, and as above, because the major changes required would have been acknowledgment that the original design wasn't safe.

When the accident occurred (first couple of days) the site technicians were left on their own to do the best they could while upper management was MIA. There was a fundamental misunderstanding of the seriousness of the situation (one shared by many in the nuclear power industry around the world) that resulted in hesitation to take necessary steps. TEPCO balked at venting, because of liability issues most likely, as well as the use of seawater for cooling because of concerns for their investment.

When it became clear that venting was necessary TEPCO made no attempt to re-establish the network of radiation monitors around the site perimeter that were disabled from lack of power. This violation of public responsibility and trust meant that it was impossible to adequately assess/measure risk to the public during the critical first week of the accident.

There was no system put in place to monitor conditions at the plant, given that it was too dangerous for workers on-site to do this, resulting in confusion over how the situation was progressing/deteriorating.

Offers of outside help and equipment were refused despite the fact that TEPCO lacked adequate equipment and trained personnel.

Plant workers were neither adequately trained nor equipped for safely and effectively carrying out their duties.

All of the above has led to confusion, misinformation, and an ad-hoc response that exacerbated an already terrible situation, unnecessarily endangered public safety and the safety of those tasked with working on the site. TEPCO in particular deserves neither the benefit of the doubt nor public trust. The government response, as the steward of the public interest, has not effectively mitigated TEPCO's failures. After all this the public will be asked to foot the bill for damage and cleanup and to suffer the various risks and ramifications of the accident for decades to come. [That said, there is also public responsibility in a democracy to make sure that public officials are doing their jobs, and consumers who rely on/expect 24hr electricity should understand that this requires acceptance of some risks and costs.]

 

[Samy24]

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.

We will never know. Even 1000 deaths will statistically never be visible. Till today most people belief only 47 man were killed in the Chernobyl accident

 

[Borek]

To all: please stop discussing politics, management and other things unrelated to the technical aspects of the Fukushima situation. Fell free to discuss these things in separate threads, but not here.

 

[clancy688]

Concrete does not get this radioactive by neutron activation.
It seems to me there must have been some corium on this piece.

So where is the rest?

Hm... I don't think that's the problem here. I'd rather ask "How did it get there?"

NHK World wrote "has been found near the reactor". So it's outside the reactor. And considering its classification as "concrete fragment", it has most likely been ejected from either Unit 3 or Unit 4.
But if there really is Corium embedded in this piece, then I have absolutely no idea how it was able to leave the reactors. Corium is flowing down, not up. But the explosions happened on top of the RPVs. Far above of the reactor fuel rods. Maybe there has been Corium. But it should be impossible for it to get ejected.

I know that TCups has a theory about the explosion at Unit 3. It's thousands of posts away, but if I remember correctly, he assumes that the Unit 3 explosion breached the SFP, boiled the water away and ejected the fuel handling machine - probably with fuel rods.
So perhaps a little chunk of fuel elements landed on a rubble part, got hot and fused with it, forming the dangerous concrete block?

What would happen, if a fuel rod would be ejected from the SFP and totally broken apart by the force of the explosion, so that all uranium pellets impact individually on site? Would they heat up and melt through the surface?

An NRC paper stated that there was highly radioactive rubble which was bulldozed over - possible fuel pellets?

 

[Caniche]

To all: please stop discussing politics, management and other things unrelated to the technical aspects of the Fukushima situation. Fell free to discuss these things in separate threads, but not here.

Which threads do you recommend?
Bit of an artificial divided though when politics dictates the bottom line and management decides cost/benefit and both control the data presentation that creates the technical pea-souper that appears here. Given those circumstances I would like to express heartfelt thanks to all those who endeavour to provide honest interpretations from restricted information,much appreciated

 

[etudiant]

The earlier reports of very contaminated material found between reactors 3 and 4 together with todays find indicate that solid pieces of nuclear material have been released, not solely gaseous or liquid emissions.
Is there any plausible source other than the SFPs, as TCups has suggested?
What are the implications if material from the SPFs is found scattered around the site?
Is there a scanning radiation meter instrument available that could survey the site and pick out radioactive hot spots similarly to the way an IR camera highlights heat leaks?

 

[MJRacer]

The earlier reports of very contaminated material found between reactors 3 and 4 together with todays find indicate that solid pieces of nuclear material have been released, not solely gaseous or liquid emissions.
Is there any plausible source other than the SFPs, as TCups has suggested?
What are the implications if material from the SPFs is found scattered around the site?
Is there a scanning radiation meter instrument available that could survey the site and pick out radioactive hot spots similarly to the way an IR camera highlights heat leaks?

X-ray film?