Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[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.

 

[michael200]

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.

In my reply to your earlier comment, which in my opinion you were jumping to the conclusion that the finding of a high dose source on the site somehow "proved" that fuel fragments/corium had somehow ejected onto the site, I was attempting to point out that there are other possibilities for the source of the radioactive material. Where in the plant this material came from is pure speculation (other than it came from somewhere in plant buildings that are blown up!). The radioactive source could have become embedded in the reported "piece of concrete" due to the explosion of the Unit 1, 3 or 4 reactor buildings.

 

[|Fred]

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.

Come on.. this had nothing to do with Tepco or JapGov but everything to do with media/press/ CGI

 

[rowmag]

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"

i agree with Borek.

As a person living within the plume from Fukushima Daiichi (though outside the evacuation zone), I would like to thank Borek for keeping the focus here on facts. I want to hear technical opinions from experts like NUCENG and Astronuc and everyone else who bring different areas of expertise and intelligent questions to the table. I am not interested in human factors analysis (to put it nicely). I want to know what is landing in my yard, and what I can expect to see landing there in the future. For the first, I can look at local monitors, but for the second I want to understand what has happened, and how it is likely to evolve and be dealt with.

So let me say thanks to this forum, which has the most intelligent discussion of this issue that I have found on the net.

 

[Jorge Stolfi]

Pretty good, Jorge, although I would dispute that fig_un1_pools_and_walls.png shows the correct layout of the pools. There has been no confirmation that the smallest pool in the picture actually exists separately from the SFP in any of the reactor buildings.

Thanks. Indeed the ony blueprints I have are those two vertical cuts shown. They do not (and should not) show the smaller pool. They do not even tell the width of the SFP on the south side, nor that of the "drier separator storage pool" on the north side. I got those widths, as well as the existence of the smaller pool, from another perspective cut that was posted here previously. However this latter drawing does not seem to be specific to Fukushima Daiichi #1. For instance, the internals seem to be mirrored E--W, and the service floor wall steelwork does not match that of the blueprints.

I was going to do a large-scale plant layout in 3D until I saw someone beat me to it. http://www.turbosquid.com/3d-models/c4d-nuclear-power-plant-fukushima/594020
I downloaded some of the jpegs from that page and saw many inaccuracies.

Indeed, for example the drywell walls in their Unit #1 (?) model seem too thick. The sources I have say that the RPV walls are 15 cm thick, and the drywell/torus walls between 2.5 and 3 cm thick. Is that correct? (It would be trivial to fix that in the POV-Ray model.)

By the way, "15 cm of solid steel" sounds like a lot, but I was surprised to see how thin the RPV walls look at those plot scales, compared to the bulk of the fuel.

 

[Joe Neubarth]

Pretty good, Jorge, although I would dispute that fig_un1_pools_and_walls.png shows the correct layout of the pools. There has been no confirmation that the smallest pool in the picture actually exists separately from the SFP in any of the reactor buildings.

I was going to do a large-scale plant layout in 3D until I saw someone beat me to it.
http://www.turbosquid.com/3d-models/c4d-nuclear-power-plant-fukushima/594020
I downloaded some of the jpegs from that page and saw many inaccuracies. The overall work is good, but not precise enough for my liking. The guy even duplicated the paint scheme on the side of the buildings! For that price, I would expect near perfection, and even if everything was perfect I don't think I would pay $299 for the model

The first thing I saw when I looked at that was the Effluent discharge is all wrong.

 

[triumph61]

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)...

Here is a Picture of the Map

 

[|Fred]

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.

yes of course but is was not what I was did not understood. On the other hand

one beta particle for tritium is 5.7 keV. For phosphorus-32 one beta particle is 1700 keV

I did not understood that the electron issue from a beta decay could be of different energy.
And it kind of screws my understanding of radiation damage..
Shouldn't there be a relation between the energy of the electron and the damage generated and there of different Sivert for each isotope?

 

[Dmytry]

yes of course but is was not what I was did not understood. On the other hand I did not understood that the electron issue from a beta decay could be of different energy.
And it kind of screws my understanding of radiation damage..
Shouldn't there be a relation between the energy of the electron and the damage generated and there of different Sivert for each isotope?

Well, it depends to where the isotope ends up in the body and how long it stays.
When you know concentration - e.g. German boar with 40 000 Bq/kg of Cs-137 (Chernobyl related) pretty much everywhere in the body, ignoring the radiation that leaves the boar, we get:
http://www.wolframalpha.com/input/?i=40000+bq/kg+*1.17+MeV+in+microgray/hour
i.e. assuming quality factor of 1.0 that is 27 microsieverts/hour (background is around 0.3). Look up definition of Sievert. There are different quality factors for different tissues and types of radiation.
The dose rate from environmental concentration heavily depends to diet etc. Above-mentioned boar eats mushrooms.

 

[GJBRKS]

yes of course but is was not what I was did not understood. On the other hand


I did not understood that the electron issue from a beta decay could be of different energy.
And it kind of screws my understanding of radiation damage..
Shouldn't there be a relation between the energy of the electron and the damage generated and there of different Sivert for each isotope?

You are right that each isotope exhibits a different characteristic ,

http://www.radprocalculator.com/Gamma.aspx

calculators like these let you select them individually (this is for gamma)

 

[MadderDoc]

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

On the Tepco hand out page at:
http://www.tepco.co.jp/en/news/110311/index-e.html
there are separate photos of the control rooms of unit 3, and 4, and also the photo you are discussing -- according to Tepco the 'Control room for Unit 3 and 4'.

The three photos can be compared, and it can be verified, that the control panel design in the right part of the photo of the 'control room for unit 3 and 4' perfectly matches the control panel design found shown in the individual photo of the control room of unit 3, and -- despite the darkness of it -- that the control panel design in the left side of the photo appears to match the one shown for the control room of unit 4.

 

[michael200]

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

What sort of things accumulate in precipitators? Co 60? Can someone tell us more about "radwaste buildings" please? Does contamination from the radwaste building fit with these early measurements? (see attached)

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

The U3 radwaste building would correspond to the radiation levels of 60 and 35 msv/hr. the radwaste building is to the left of the U3 reactor building.

 

[Krikkosnack]

http://energheia.bambooz.info/index.php?option=com_k2&view=itemlist&task=date&month=4&year=2011&lang=it"

http://www.rchoetzlein.com/theory/?p=171"

 

[RealWing]

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.



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.

I've been a Shift Manager in a multi unit control room at the Bruce A NPP in Ontario, Canada. This design has the control panels for all 4 units in a circle. From an incident or upset perspective, I certainly liked this design from a command and control point of view. I could walk into the MCR and very quickly assess the impact on my 4 unit plant. We had a minimum complemet of operators on each unit and if we had excess - then they can quickly assist on the unit in trouble.

Are there cons - absolutely. There is additional distractions when a unit is in outage and some common mode issues - but these can be safely managed.

 

[MadderDoc]

<..>the radwaste building is to the left of the U3 reactor building.

How do you know this is a radwaste building?

 

[Krikkosnack]

The U3 radwaste building would correspond to the radiation levels of 60 and 35 msv/hr. the radwaste building is to the left of the U3 reactor building.

near the unit of building3... look to one of the trajectories colored in yellow on the post https://www.physicsforums.com/showpost.php?p=3256828&postcount=4350". goes directly on it..

 

[etudiant]

Is there any experience with TEPCOs efforts to stabilize the dust and small debris around the site by spraying a binder on the surface?
Afaik, it is common to spray oil on dirt roads in rural areas to keep the dust down, but here there is a good prospect for severe rains and possible storms as well. So does it all get washed into the sea?

 

[jlduh]

AS we have some operational knowledge here on the forum, let me ask some questions about the control rooms, to clarify the "cons" which in my mind are just not limited to distractions between shifts (even if this can be a factor, and has be a con in the example of TMI):

1) could you precisely locate the control rooms for the various reactors at Daichi plant, on a map or on a picture (position and at which floor)?

2) what kind of protections (mechanical and radiological mainly) do they normally have: resistance to explosions (thickness of concrete, etc.), shielding to some level of ambient radiations, resistance to water flooding, type of air filtering, etc.

My questions relates to the fact that in my mind, the problem with one common control room is that this is the opposite of some kind of redundancy principle in case of accident, because in this case there is "concentration" of the equipement: if one rooms becomes damaged or no more usable because of high radiations inside, how can you still continue to drive the second reactor even if it is undamaged in itself? This also lies to an other question: can a reactor be put in cold stop, and MAINTAINED -in the time, but how long?- in safe cold stop without any single operator acting on it?

At Tchernobyl, and this always amazed me to say the least, they continued even during the accident or soon after to operate the adjacent reactors: first because they HAD to do it for safety reasons (I read somewhere that they feared by the way that they could lose the control of those ones if the radiations or damages were still increasing after some possible new secondary explosions), and then because they continued to produce electricity with them on this Tchernobyl plant, until 2000 when international pressures (and fundings) pushed the russian to stop all the reactors at the Tchernobyl plant.

So my question relates to this simple consideration: in case of a common room, does it mean an increased risk for losing control over a second reactor in case the first one creates conditions where the working (ambient radiations) and operational conditions (damages) are no more possible in the shared control room?

 

[ascot317]

Is there any experience with TEPCOs efforts to stabilize the dust and small debris around the site by spraying a binder on the surface?
Afaik, it is common to spray oil on dirt roads in rural areas to keep the dust down, but here there is a good prospect for severe rains and possible storms as well. So does it all get washed into the sea?

They've done this, see this https://www.physicsforums.com/showpost.php?p=3262956&postcount=4696".

@jlduh, normally there should be an emergency control room (not sure if the term is proper in English, not a native speaker) for each reactor, which is heavily shielded (like a bunker, including air filters) and somewhat remote and allows full control over the reactor (given you have power). I assume this is where the plant operators went after leaving the main control rooms. I don't know the internal layout of Fukushima, so I can't locate it for you or tell you about how it is built.

 

[NUCENG]

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...



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.

Understanding the equivalence methodology may be aided by reviewing FGR11 and FGR12 at the following link.

http://www.epa.gov/radiation/federal/techdocs.html#report12

 

[jlduh]

Some more information on the debris map, confirming that the reactor 3 area and the area close to the main building office are still (like the beginning) the worst ones from radioactive standpoint:

http://www3.nhk.or.jp/daily/english/24_17.html