Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[swl]

It takes a mixture of hydrogen and oxygen to be explosive. One or the other but not both doesn't give you an explosive mixture.

This reminds me of all the concern during the Three Mile Island accident concerning the "hydrogen bubble". The concern is that it was going to explode and breach the system piping.

Rationality reigned again when it was realized that there was no oxygen in the system to make an explosive mixture...

An excellent example of why it is important to maintain integrity of containment. (Edit: With the compromised containment, it is possible that air, with oxygen, can enter the containment.)

Many here in Japan are now wondering if we should expect another explosion soon, and if so, how it will effect the spread of contamination. Experts?

 

[elektrownik]

An excellent example of why it is important to maintain integrity of containment.

Many here in Japan are now wondering if we should expect another explosion soon, and if so, how it will effect the spread of contamination. Experts?

I don't think that there is much hydrogene in RPV/Drywell/Torus, it could be in some pipes, all RPVs are at atmospheric pressure so hydrogene shouldn't accumulate there, also there is stable cooling now, to ignite it would need heat source, corium is good cooled I think, so there shouldn't be any new explosion... Sorry for bad language

 

[tsutsuji]

New video released by TEPCO on the status of the measuring instruments.

http://www.youtube.com/AtomicPowerReview

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110917_02-j.pdf The slides shown in the above video.

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110924_03-j.pdf series of pictures of units 5 and 6.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110924_01-e.pdf situation of upper part of unit 2.
http://www.tepco.co.jp/en/news/110311/images/110924_01.zip video of upper part of unit 2. (taken 17 September 2011)

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110924_02-e.pdf situation of upper part of unit 3.
http://www.tepco.co.jp/en/news/110311/images/110924_02.zip video of upper part of unit 3. (taken 24 September 2011)

 

[imandylite]

Reactor unit 3 latest vids from crane

https://www.youtube.com/watch?v=pkg_bkpeW5o

 

[imandylite]

reactor unit 2 latest vid through the side hole in the wall

https://www.youtube.com/watch?v=9YDleun8oz8

 

[SteveElbows]

If only those videos had existed months ago when we were somewhat plagued by dramatic theories about the state of reactor 3.

Although to be honest, the detail that we can see in the new video is mostly just a clearer view of what we were able to see from much poorer videos in the past. We see the edge of one set of concrete circular reactor well top caps, and we see some steam escaping from one edge of the removable concrete wall that is between the reactor well and the dryer pit. This same detail was visible on the old video that was shot from a helicopter, but its good to see it more clearly, and interesting to see what is still being emitted from this region.

The reactor 2 video is very frustrating, could they not have managed to get the camera to point downwards just a little more? Mind you I expect the pink shielding barriers would still have obscured the view of the floor above the reactor well. But it is interesting to note steam escaping from that direction.

 

[CaptD]

NEW Fukushima Disaster TEPCO Video of Reactor Unit 3 destroyed top floor, Well and SFP 24 Sept 11
http://australiancannonball.com/2011/09/24/new-fukushima-disaster-tepco-video-of-reactor-unit-3-destroyed-top-floor-well-and-sfp-24-sept-11/

Hopes this help figure out just what is going on in Fukushima!

 

[NUCENG]

The term "cold shutdown" essentially means "not boiling".

It does NOT mean "ambient temperature". Normally a power plant never gets down to ambient temperatures even during a refueling outage.

The usage of the term is customary and proper and not propaganda.

Dr. Gregory Greenman
Physicist

Actually in US GE BWRs, Standard Technical Specifications define the mode called "Cold Shutdown" as the Reactor Temperature less than 200 degrees Fahrenheit, the mode switch in "Shutdown" and all RPV head bolts fully tensioned.

In the current condition of the Fukushima plants I would not say the plants have achieved "Cold Shutdown in a legal sense because:

• Mode switch may be in shutdown, but Reactor Core subcritical reactivity cannot be guaranteed.
  
• The physical condition and accuracy of thermocouples measuring reactor temperatures is unknown.
  
• RPV damage may have occurred making the condition of the RPV head bolts (assuring the coolant system integrity) meaningless.

Since the Unit 4 RPV Head is removed and the core is located in the spent fuel pool, that unit is in Refuelling Mode.

Once core degradation started and the geometric integrity of the core was altered the normal meaning of shutdown went out the window. I think that Japan and TEPCO need to be careful using terms that can be misunderstood.

edit: That said, no boiling is progress.

 

[Susudake]

The term "cold shutdown" essentially means "not boiling".

It does NOT mean "ambient temperature". Normally a power plant never gets down to ambient temperatures even during a refueling outage.

The usage of the term is customary and proper and not propaganda.

Dr. Gregory Greenman
Physicist

Perhaps I didn't put the question well, but this doesn't completely answer my question. The "Cold" part of "cold shutdown" would seem to refer to the radioactive material, be it in fuel rods or now in the form of corium, not boiling water any more, thus no more radioactive steam being produced; if the material is still in a normal configuration, i.e. fuel pellets in rods, then that would seem to merit the word shutdown, since it can now be removed to a spent fuel pond etc.

But if you have corium, the composition of such is not in a completely controllable state (that is at least theoretically re-criticality is possible, and you can't handle/move it like fuel rods in assemblies), and that corium has gotten out of at least one layer of containment, then using the term "cold shutdown" sounds euphemistic at beast, or even propagandistic.

So your saying this customary term is not propaganda (which is kind of stating the obvious) doesn't seem to apply in this case.

My understanding is they don't even have the technology at present to remove the corium from where ever it will have flowed to by the time they do develop that technology--I was one report saying it was 10 years out, but who knows, could be 2 years, could be 20? So again referring to any of these reactors as being in "cold shutdown" seems rather...inaccurate, to say the least.

Let me re-emphasize that the thrust of my question is whether the corium in these reactors being at 99 deg. C puts those reactors in a shutdown state, or even is a big step along that path, or is relatively insignificant considering the overall situation. I'm seeking a sense of how big or small a step that is. If the temp. reaching that point is relatively insignificant, then the accuracy of using the term shutdown to describe it can be better determined; whether it's propaganda is another matter, perhaps best debated on the other thread (or completely elsewhere).

Edit: I see nuceng already addressed, mostly, my question.

 

[tsutsuji]

We see the edge of one set of concrete circular reactor well top caps, and we see some steam escaping from one edge of the removable concrete wall that is between the reactor well and the dryer pit.

That dark area from where the steam is escaping is, roughly speaking, dove-tail shaped. Is it a gap or filled with a gasket or something to prevent water from leaking between reactor well and dryer pit ?

 

[CaptD]

Nuceng

I think your statement is right on target:
"Once core degradation started and the geometric integrity oif the core was altered the normal meaning of shutdown went out the window. I thing that Japan and TEPCO accudentr need to be careful using termsthat can be misunderstood"

By "mincing or SPINNING" words they are doing the Japanese and scientists World Wide a dis-service!

 

[SteveElbows]

That dark area from where the steam is escaping is, roughly speaking, dove-tail shaped. Is it a gap or filled with a gasket or something to prevent water from leaking between reactor well and dryer pit ?

Id say it is more finger/box joint shaped than dove-tail.

I don't know exactly how it is supposed to look normally, though I am tending to assume that the visible gap is larger than it should be. I suppose one possibility is that the non-removeable floor/wall that it is supposed to interconnect with has been displaced somewhat to the west, especially given to the damage to that section of the building. But it might just be a gasket failure, it seems the industry is not exactly falling over itself to share that level of detail with the masses.

 

[SteveElbows]

Nuceng

I think your statement is right on target:
"Once core degradation started and the geometric integrity oif the core was altered the normal meaning of shutdown went out the window. I thing that Japan and TEPCO accudentr need to be careful using termsthat can be misunderstood"

By "mincing or SPINNING" words they are doing the Japanese and scientists World Wide a dis-service!

It wouldn't matter so much if the media had been better. I think perhaps the media are a bit cautious of the cold shutdown stuff because they are tending to write it inside speech marks, slightly implying that it isn't exactly cold-shutdown in the very routine sense of the term. And plenty of media still casts a less-rosy picture of the situation as they talk about things like the reactors 'still billowing out radiation'. But at the same time they do not go completely nuts about the way the Japanese are portraying the situation. Will just have to wait and see what happens if/when the Japanese decide to use this 'cold shutdown' stuff to relax evacuations. Spinning seems understandable, but if they try to use that spin to expose people to unforgivable risk, then we need to shout more about this stuff.

 

[mscharisma]

The term "cold shutdown" essentially means "not boiling".

It does NOT mean "ambient temperature". Normally a power plant never gets down to ambient temperatures even during a refueling outage.

The usage of the term is customary and proper and not propaganda.

Dr. Gregory Greenman
Physicist

As a non-technical person, I can of course not contribute to the technical arguments for or against the use of the term, but is it merely a technical question? While the reaching of a certain temperature may be the determining factor when a reactor is considered to be successfully shut down and in a cold shutdown state, the term also implies operation per procedure to get to that point, followed by subsequent handling per protocol. Since this is obviously nowhere near what's going on at Daiichi, I personally find the use of the term in that context highly misleading (to say the least), regardless of any temperature measurements.

 

[alpi]

If the temperatures in the empty spaces inside the containments (or around the corium) is brought down to less than 100 degrees I guess there would not be any radioactive steams escaping from the containments, since the driving force is gone. That sounds like good progress, whatever it is called.

 

[NUCENG]

It wouldn't matter so much if the media had been better. I think perhaps the media are a bit cautious of the cold shutdown stuff because they are tending to write it inside speech marks, slightly implying that it isn't exactly cold-shutdown in the very routine sense of the term. And plenty of media still casts a less-rosy picture of the situation as they talk about things like the reactors 'still billowing out radiation'. But at the same time they do not go completely nuts about the way the Japanese are portraying the situation. Will just have to wait and see what happens if/when the Japanese decide to use this 'cold shutdown' stuff to relax evacuations. Spinning seems understandable, but if they try to use that spin to expose people to unforgivable risk, then we need to shout more about this stuff.

A couple of points:

Media are not experts that would understand the nuances of terms like cold shutdown. It may not even be deliberate by TEPCO and or the regulators. Many of the "experts" have shown clearly sloppy use of terms like this, (probably even me). Add in the language difference and communication becomes even more inexact. Let's be fair and clarify what we can, when we can.

The Japanese erection of building enclosures will reduce the continuing release of radiation. There is still likely to be some continuing release offsite from the facility due to leaks, rain, disturbance of debris during cleanup, etc.Continuing to cool the core remnants and cleaning up the cooling water will reduce potentiol for future releases.

By the time defuelling begins, the use of water submergence for shielding will help reduce exposure for workers. I am certain there will be instrumentation to monitor neutron radiation that could signal approach to recriticality during fuel extraction, transportation and storage. Shutdown margin may be further enhanced by neutron absorbers like Boron. Extracted material will be sampled, analyzed, and controlled to prevent bringing material into a more dense geometry.

Finally, the decision to relax evacuation requirements is not likely to be affected by the term we use for the condition of fuel inside the plant. It will be based on risk to citizens from releases that have already occurred. TMI2 was defuelled in the middle of a populated area without long term disruption of the area. Fukushima damaged fuel removal will be more difficult and possibly more risky but it is, in my opinion, feasible. If that is not the case, then extending evacuation or entombment remain options.

We will not see a quick end to this. Every step the Japanese take will need to be carefully planned, analyzed, tested, critiqued, executed, monitored, verified, and reviewed. It will be slow and expensive. At least I hope so, because if not, the risk will be increased.

 

[SteveElbows]

Finally, the decision to relax evacuation requirements is not likely to be affected by the term we use for the condition of fuel inside the plant. It will be based on risk to citizens from releases that have already occurred.

Well that's how it should be, but I think many of the concerns about the 'cold shutdown' term stem from the fact that some of the reporting from Japan suggests that the authorities are leading people to believe that reaching certain milestones on the roadmap will make a difference to evacuation zones etc. I hope sanity prevails, but I can't blame people for being a bit concerned about how this will pan out, there have been some worrying signs but this is the wrong thread to explore this point further.

I've been looking at the reactor temperatures again, following on from my posts of a few days ago where I was interested in rising suppression chamber temperatures at reactor 2. Those measurements have continued to slowly rise, although many other temperatures have now fallen quite a bit due to the additional water injection rate. RPV Bottom part is taking its time in coming down below 100 degrees C, but its getting closer. I am not sure if it will actually get there without further increases to the water rate though.

The very tiny increase in reactor 3 suppression chamber temperature that I noted did not amount to anything, it has not followed the pattern that I noted had happened to reactor 2 in September.

The CAMS data that I was trying to use to enhance the picture of what's been happening at reactor 2 has proven to be too erratic to be of very much use. The B sensor for the reactor 2 suppression chamber is quite erratic, and has been in the past, so I can't put too much weight on it. The A sensor has mostly continued to inch higher, but as with the temperature we aren't talking about a very dramatic rise.

 

[rowmag]

Well that's how it should be, but I think many of the concerns about the 'cold shutdown' term stem from the fact that some of the reporting from Japan suggests that the authorities are leading people to believe that reaching certain milestones on the roadmap will make a difference to evacuation zones etc.

I think "cold shutdown" means that evacuation zones will be determined only by contamination levels, not by proximity to the plant. So some areas it will be possible to move back into. This seems to be the current stance of the government, at least. (And I note that Kan was castigated for insensitivity for remarking early on that some of the evacuation areas would remain uninhabitable even after the immediate crisis passed. But further discussion of that aspect should probably go to the political thread or the "government performance" thread.)

 

[CaptD]

mscharisma I agree with you 100%, using that term implies that things are "back to normal" which is nowhere near the truth! As others have said the cleanup will be a very long and costly process even without the public's distrust of TEPCO's news releases!

Fukushima disaster: residents may never return to radiation-hit homes
Japanese government will admit for first time that radiation levels will be too high to allow many evacuees to return home
http://www.guardian.co.uk/world/2011/aug/22/japan-nuclear-disaster-radiation-levels

 

[etudiant]

The recent TEPCO videos from reactors 2 and 3 show ongoing steam puffs.
While the videos did not make the association, it seems likely that the ongoing emissions of 200 million Bq/hr are concentrated in those puffs.
Surely it is better to allow these relatively modest emissions to continue than to attempt to seal them into a containment. The most likely outcome of this containment approach is to make the reactors entirely inaccessible, because of lethal radiation levels. What is the rationale for this?

 

[SteveElbows]

Sorry if this has been linked already:

http://www.meti.go.jp/english/earthquake/nuclear/iaea/iaea_110911.html"

(English)

Fascinating yet very time-consuming to get through! I've not managed all of it yet but have read enough to offer initial comment.

I recommend the mammoth chapter 2 document for anybody interested in lots of detail about the following:

Earthquake & Tsunami stuff in depth

The various problems with venting at various reactors

Lots of detail about spent fuel pools, including estimated decay heat, water levels over time and comprehensive tables showing different water spraying/pumping operations.

Quite a bit of detail about what happened at the other 3 nuclear plants that were somewhat affected by the earthquake/tsunami, more detail than I have seen in the past.

Some interesting detail about radioactive release estimates, including a graph that includes timing of various venting operations, explosions etc. As we might expect, there is significant repetition of stuff we have already sen in the past, but this attempt is clearer in places and has new details here and there, so I found it worthwhile to at least skim it.

 

[SteveElbows]

The recent TEPCO videos from reactors 2 and 3 show ongoing steam puffs.
While the videos did not make the association, it seems likely that the ongoing emissions of 200 million Bq/hr are concentrated in those puffs.
Surely it is better to allow these relatively modest emissions to continue than to attempt to seal them into a containment. The most likely outcome of this containment approach is to make the reactors entirely inaccessible, because of lethal radiation levels. What is the rationale for this?

Im pretty sure they intend to filter the air in buildings once they have provided some new form of secondary containment.

I do not have complete confidence in TEPCOs measurements of what is escaping from buildings into the air, especially having seen those videos, but a more accurate picture will be obtained by providing new secondary containment.

The updated roadmap from a few days back goes into more detail about the detail of the estimated current release rate:

・ The current release rate for both Unit 1 and 2 is estimated at approx. 0.04 billion Bq/h using dust concentration at the upper parts of the reactor buildings. The rate for Unit3 is now being re-estimated.
・ The current total release rate is estimated at approx. 0.13 billion Bq/h using dust concentration at the sea area, and there might be little effect of radioactive materials that released previously.
・ Therefore, the current total release rate is assessed at 0.2 billion Bq/h, which is 1/4,000,000 of that at the time of the accident.

From page 13 of http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110920e3.pdf

 

[LabratSR]

Im pretty sure they intend to filter the air in buildings once they have provided some new form of secondary containment

Notable is the ductwork in the corner posts of the frame.

http://www.tepco.co.jp/en/news/110311/images/110917_02.jpg

 

[LabratSR]

Photo dump by TEPCO - Units 5 and 6

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110924_04-e.pdf

Full size here

http://www.tepco.co.jp/en/news/110311/index-e.html

 

[CaptD]

The recent TEPCO videos from reactors 2 and 3 show ongoing steam puffs.
While the videos did not make the association, it seems likely that the ongoing emissions of 200 million Bq/hr are concentrated in those puffs.
Surely it is better to allow these relatively modest emissions to continue than to attempt to seal them into a containment. The most likely outcome of this containment approach is to make the reactors entirely inaccessible, because of lethal radiation levels. What is the rationale for this?

The containment is to me, just a "coverup" that will keep prying eyes from seeing what is going on inside the containment! Without drawing "rolling eyes" from anyone here, I still believe that TEPCO has The Japanese Gov't. over a barrel because of something like a secret nuclear Lab under the complex and that is why TEPCO has a free hand to do whatever it wants and the Gov't. must "bow" to them...
Read with GRAINS of salt: http://gizadeathstar.com/2011/09/fukushima-theories-the-nuclear-weapon-hypothesis-again/

I cannot believe that TEPCO does not have "something" over the Japanese Regulators that gives them such a "free" hand to do whatever they want!

 

[etudiant]

Im pretty sure they intend to filter the air in buildings once they have provided some new form of secondary containment.

TEPCO has made its intention to do that very clear.
How they plan to do this effectively is what puzzles me. The building cover is flat plastic sheeting, so any pressure differential in the structure must be minimal. I don't see how that allows for any flow to develop to gather the various leaks and emissions into a filter. It seems equally likely that the structure inside of the cover will get covered with condensed emissions, which would greatly complicate any future work.

 

[NUCENG]

The containment is to me, just a "coverup" that will keep prying eyes from seeing what is going on inside the containment! Without drawing "rolling eyes" from anyone here, I still believe that TEPCO has The Japanese Gov't. over a barrel because of something like a secret nuclear Lab under the complex and that is why TEPCO has a free hand to do whatever it wants and the Gov't. must "bow" to them...
Read with GRAINS of salt: http://gizadeathstar.com/2011/09/fukushima-theories-the-nuclear-weapon-hypothesis-again/

I cannot believe that TEPCO does not have "something" over the Japanese Regulators that gives them such a "free" hand to do whatever they want!

I have bookmarked that site. It looks to have a LOT of entertainment value. But I have to ask what you are trying to say in this post? Steam explosions have been discussed here as a mode of damage and this has not been ruled out. The nuclear weapon theory would need to address the time sequence of explosions/damage and would seem to require more than one. You suggest a secret nuclear lab, but don't explain how that could be supported or disproved. You imply that the Japanese government is "over a barrel, but I can't imagine how you came to that idea. Negligence, incompetence, or even the Japanese industry/government cultural power inversion seem much more likely.

There is "out of the box" thinking, but that site is not even in the Milky Way galaxy.
Unsupported conspiracy theories are not allowed on this forum, but I am fascinated by the kind of imagination it took to write that post or provide that link. I hope the mentors give you a chance to try to explain.

 

[tsutsuji]

SARRY line A was used for the first time on 23 September:

9 / 23 16:53 We activated second cesium adsorption facility (System A and System B). At 17:03, the flow rate achieved steady state (approx. 40 m³)
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110923_03-e.pdf

Then on 24 September:

*At approx. 8:30 pm on September 24, the second Cesium adsorption facility
of water treatment facility has automatically shut down. Investigations
are now underway. Water treatment by Cesium adsorption facility is
continuing. As there are sufficient treated water stored in the tank,
there is no impact on the water injection into the reactors.
http://www.tepco.co.jp/en/press/corp-com/release/11092502-e.html

So it seems that both lines A and B of SARRY are down. The Kurion system is running. The status of the Areva system is unclear.

 

[zapperzero]

Photo dump by TEPCO - Units 5 and 6

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110924_04-e.pdf

Full size here

http://www.tepco.co.jp/en/news/110311/index-e.html

Very good stuff

reactor pedestal and control rod actuators
http://www.tepco.co.jp/en/news/110311/images/110924_05.jpg
yes, that is a pipe hung from the doorjamb with baling wire and scotch tape

nice views of the overhead cranes
http://www.tepco.co.jp/en/news/110311/images/110924_03.jpg
http://www.tepco.co.jp/en/news/110311/images/110924_21.jpg
those beams are massive! (take the operator cab for reference)

 

[tsutsuji]

Im pretty sure they intend to filter the air in buildings once they have provided some new form of secondary containment.

TEPCO has made its intention to do that very clear.
How they plan to do this effectively is what puzzles me. The building cover is flat plastic sheeting, so any pressure differential in the structure must be minimal. I don't see how that allows for any flow to develop to gather the various leaks and emissions into a filter. It seems equally likely that the structure inside of the cover will get covered with condensed emissions, which would greatly complicate any future work.

It seems that some of those problems were addressed in Tepco's report to the NISA in June:

The humidity inside of the cover will increase due to the evaporation from the spent fuel pool, but 40,000m3/h will be concurrently replaced with air from outside. Since the ventilation amount is larger tha[n] the evaporation amount from the pool, it is not supposed that the temperature inside of the reactor building will significantly increase.

page 6 http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110624e15.pdf

According to the same document, the cover fabric can withstand a pressure of 30 cm of snow. My understanding is that the air blowers must be powerful enough to compensate the loss of pressure caused by the filters, but that does not mean that the vacuum inside the structure must be intense (significantly intense compared to a 30 cm snow pressure). As the report to NISA does not even mention the pressure caused by the vacuum, it is probably because it is negligible compared to snow and wind.