From TEPCO's regular press conference at 6PM, April 13, 2012.
The heat exchanger for the Reactor 4 Spent Fuel Pool restarted at 4:04PM.
Temperature as of 5PM was 37.6 degrees Celsius on the water surface.
TEPCO took the photos of Reactor 3's Spent Fuel Pool. One of the photos shows the fuel exchanger (upper right):
Photo No.1 (upper left) was taken from the surface of the water. Matsumoto says the fuel racks are underneath the debris. Photos No.2 (upper right), No.3-1 (lower left), No.3-2 (lower right) shows the pool at 7 meters from the surface. Photos No.2, No.3-1 and No.3-2 were taken from the cask space.
Photo No.3-1 shows the fuel rack, and the fuel handles. Photo No.3-2 is a blow-up of No.3-1.
Matsumoto says the pool didn't look damaged as far as the camera could see.
The video was taken, and TEPCO is currently reviewing the video. It will be made public next week.
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TEPCO FINDS 35-TON MACHINE FALLEN IN FUKUSHIMA NO. 3 SPENT FUEL POOL, Kyodo News, April 13, 2012
Excerpt..."The operator of the crippled Fukushima Daiichi nuclear power plant on Friday found that a 35-ton machine had dropped inside the spent fuel pool of the No. 3 unit, possibly because of a hydrogen explosion that occurred in the early stage of plant's nuclear accident last year.
TEPCO, reported the finding after placing a camera inside the water-filled pool the same day to prepare for removing, as part of the decommissioning process, the nuclear fuel stored there.
One photo showed part of the machine, originally located above the pool and used to insert and remove fuel, appeared to have dropped onto the nuclear fuel storage racks"...
Laprimavera, have you read the full Kyodo News article? I only have the above portion.
Has TEPCO, or any independent analyst, commented on how this will impede the removal of the spent fuel at the No. 3 unit?
JP
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Its good to learn more about this pool.
Lots of debris & equipment having fallen into this pool will certainly complicate efforts to remove the fuel, as does the general poor state of upper floors of reactor 3 building, and the likely radiation levels around parts of these areas.
I tend to assume that they are tackling reactor 4 pool first not just because there is more fuel in that pool, and hotter fuel, but also because it has been much easier to do the initial phases of debris removal and tidying up at reactor 4 than it is at reactor 3. They have been removing some rubble from upper areas of reactor 3 but I assume that progress is slow, and we haven't seen too many high quality images to show what progress they have made at reactor 3.
Assuming that they eventually get the building to a state where they can start to remove debris from the reactor 3 pool itself, I assume this will be a long and tricky mission. They have to worry about the possibility of any of the debris falling back down into the pool if something goes wrong during the removal.
I hope the video will give us a slightly better sense of all the rubble in the pool, but we can already tell that its not good, and that partly why we don't hear too much about their plans for this pool as opposed to reactor 4 pool where the situation is simpler in some ways.
Indeed, the pools are still accessible, in contrast to the cores, which are apparently off limits to mankind.
Sadly the fuel cartridges are shown only sideways, so one cannot see how much circulation they have (think of MadderDoc's recent posts on the PF).
In my impression, especially the lower right photo doesn't support the assumption that the assemblies shown really have become "cold" already.
And, I seem unable to recognize a single fuel handling grip.
Either the magnification is high or the fuel assembly handles have been burnt or wiped away by some other violent action.
And, with the FHM complex in the pool, I doubt that will improve the mechanical stability or even make handling things easier.
Hope they'll release the video soon.
What do you mean about fuel assemblies having become 'cold' already. What sort of cold do you mean, and what assumption? Its safe to assume that there is water in the reactor 3 pool, and they have a system to keep this water at a certain temperature. Temperature and circulation around individual fuel bundles is not known, but I don't see anything in the photo that gives any clues about this, so I don't know what you mean.
One fuel bundle handle is kind of visible in the image, but really the image quality is too poor to say much more than that. Given what we do know about reactor 3 pool, I do not think fuel damage can be ruled out yet, but neither is there much in the way of compelling evidence that fuel there was damaged to a significant extent. W will find out eventually, this is more certain than how much more we will learn about the reactor cores.
Good and important question, elbows.
Imho an assembly has become cold as its outer temperature has decreased as much as it can contain its radioactive contents (fuel+fission decay products). This probably would mean a quite low energy production so that the temperature stays safely below a Zirconium-steam reaction.
Some of the fuel stored in the pools 1-3 is older than 12 years iirc. It won't contribute much to heat, could be stored at open air.
But, the fuel in SFP #4 is different. It's very fresh and hot, and these hot assemblies are packed very densely.
They are not stored in a distributed manner as they should be !
So, if this pool runs out of water, you can expect quite a problem.
Really, the DoE document MadderDoc referenced to is very interesting:
"The map of assembly activities is cropped from the document "DOE Response to Fukushima Dai-ichi Accident" which is included in these transcripts from the US DOE ACRS subcommittee on Fukushima May 26 2011 meeting (the map is on page 188 of those transcripts)
http://pbadupws.nrc.gov/docs/ML1114/ML11147A075.pdf
"
see posts 12812+ here: http://www.physicsforums.com/showthread.php?t=480200&page=801
So I don't really know if, and how much the fuel in units 1-3 really poses a big danger compared to SFP 4.
If about 50 old fuel assemblies smoke off in open air, it won't be much of a problem, if the winds go east, I guess.
All of the fuel pools are dangerous, any of them being empty of water would be very bad news. Reactor 4 pool was considered more dangerous because of how bad the building looked, and because the heat generated by the bundles in this pool was more significant so this pool would be expected to boil dry more quickly than the others. But if any of the other pools somehow got into a bad state, I do not think I would describe them as less dangerous that reactor 4 pool, just less potential to go wrong as quickly.
I mean certainly how hot the fuel is also makes a difference to chances of having a nasty zirconium fire, but thats not the only issue you have to worry about if a pool runs dry or collapses, you also have to worry about the radiation from unshielded fuel, and I believe the other pools would still deliver plenty of horror in this respect if the fuel in them was uncovered. Less than reactor 4s fuel, but still enough to cause complete nightmares on site.
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