Japan Earthquake: nuclear plants

SteveElbows

Sorry but that photo is a pretty poor analysis, the objects in the photo are a poor correlation for the circular items of the fuel handling bridge.

People did spend a lot of time looking at a variety of photos around reactor 3 for signs of the refuelling bridge. No useful conclusions were formed, other than being able to say that its not intact above the pool like reactor 4's is.

Some bits of it could be in the pool, but its also quite possible that it was ejected from the reactor building. And not necessarily dramatically either, it may have blown out in such a way that it did not travel high into the sky, but rather toppled south and fell to the ground between reactors 3 & 4, and area where quite radioactive debris was detected and dealt with later. And we know from the level of information given out over the course of the disaster that they were unlikely to bother telling the public the detail of what the debris consisted of. People were also interested in the hole in the roof of reactor 3 turbine building.

Given the size of the explosion at reactor 3 building, Im really not sure that we could expect to learn anything useful from the final resting spot of the refuelling bridge anyway.

SteveElbows

The way that the SPF water level is measured is one of the weaknesses that the disaster revealed. Even at the best of times it seems that such information was not easily obtained without actually being on the refuelling floor. And its more often obtained by looking for signs that the pool has overflowed into the skimmer surge tank, rather than measuring the water level directly.

As for how it came to run out of water, the decay heat of the fuel causing it to boil away is the main area of focus. Obviously if the pool lost integrity and leaked then this would be another way that water level could be lost, but even if the pool remains intact the water is still lost at quite a high rate once the pool reaches a certain temperature.

SteveElbows

I need some help with some relatively short Japanese documents that were released in October but were written in the days following the disaster.

Specifically these two documents that are to do with neutron detection, can you give me an overview of what they say?

http://www.jnes.go.jp/content/000119688.pdf

http://www.jnes.go.jp/content/000119689.pdf

Also this one which mentions drywall vent pipe & pits:

http://www.jnes.go.jp/content/000119681.pdf

jim hardy

I remember those days well.

I felt at the time the pool level was getting low and there was significant "shine" up through the little water left, and backscatter down was reason for high readings near building. They got the "elephant" there just in time and readings came down as they watered the pool.

Also if i recall correctly there was what looked to me like the missing crane near top of the debris pile on N side of Unit-3, itself pretty well covered by rubble.

Not to turn this thread back into the Unit 3 explosion thread.
Just my 2 cents worth of memories from last year.
I think it's safe to presume the explosion caused some leaks that lowered level. Sloshing during quake probably put contaminated water in basement early on.
I am not ready to make a strong claim whether fuel got uncovered, though I think it didnt.
Someplace there's radionuclide analysis of SFP water and that was my basis for that.

Still waiting on that Nova show.

SteveElbows

No, that device got plenty of attention here, its the carousel thats used for retensioning the bolts of the reactor or containment cap (I forget which at this precise moment in time).

SteveElbows

Looks like the temperature sensor for reactor 2 RPV Supporting skirt upper part has started to fluctuate more in the last few days:

http://www.tepco.co.jp/en/nu/fukushi..._data_2u-e.pdf

Seems they are going to send a remote camera vehicle into spent fuel pool of reactor 4 to look at the debris, and they are also considering moving the control rods from the fuel pool to the reactor at some future point when they start to tackle the fuel in that pool.:

http://www.tepco.co.jp/en/nu/fukushi...20312_01-e.pdf

r-j

This may qualify as a dumb question, but I must ask. It's been almost a year since the explosion of building three. From what I read, it seems there is no information about the state of the spent fuel storage pool that used to be inside the containment building.

Is that true?

A related question. If there is no evidence of the condition, is there any scientific reason not to snake a camera in there and look at it?

Which brings up another question. Could the condition of fuel pond be verified in any other way?

NUCENG

You may be right, but look at what you said.

"it is, must be, all gamma, because that's all the military cares about." I'm not sure that assumption is true based on my military service. Do we know what type of dosimetry they had on the helicopter?

"Look at that anemic plume of steam," Water vapor (steam) is not radiation. A radiation plume does not have to be visible to be deadly. In fact gas releases are likely to be invisible,

"if it was, people on the ground would have been getting it too" Depending on wind speed, direction, and atmosppheric stability and the temperature of the released plume, people on site at ground level may not have been as exposed. If it was shine from the SFP or the drymell the surrounding concrete and debris could have provided shielding to personnel at ground level.

"The reactor well cap was not displaced, that we know of." Exactly!

Are these alternative explanations true or false? I don't know, but they illustrate that your conclusions include inherent assumptions that we cannot yet verify. That is the best service this forum has provided - allowing ideas to be introduced and hypotheses to be tested.

tsutsuji

Thanks for your reply. Were there SFP temperature readings available at that time ?

duccio

4 Sv/hr 100 meters above reactor 3, should we take this reading seriously? Maybe right on top of exhaust stack during dry venting, but it's two orders of magnitude higher than the other readings taken 100 meters from the building

SteveElbows

Not during the time that they most needed such readings. They had to resort to using infra-red camera from a helicopter to estimate the pool temperatures during the week that they were most concerned about the pools.

For example with unit 4 pool they had a temperature reading of 84 degrees C around March 14th, but after that they did not get another proper temperature reading from that pool for a very long time.

SteveElbows

Thats not the case. There has not been any fascinating new information about reactor 3 pool for ages, but there was information supplied ages ago.

They did some analysis of the water to see what levels of various radioactive substances were in it.

They also stuck a camera into it and published the video, probably about 10 months ago now. Unlike the video of the pool at reactor 4, its very hard to see anything useful in this video, because the pool has lots of debris in it.

http://www.youtube.com/watch?v=OMpGVfU2jtI

zapperzero

Nope. We don't know. We probably won't ever find out. What do you think is more likely to have been used, internally mounted AN-VDR 2 that is standard JSDF gear or some sort of scout setup with an external probe?

So you're thinking clouds of Iodine? Why would it take a different path than the water vapor?

Yeah you're right.

Yep. The decrease in dose rates after water was poured provides circumstantial evidence of this.

I'd hate to call them conclusions. More like hypotheses. But yes, I like to believe that what we're doing here is useful

Rive

Even some parts of the top concrete plug were spotted under the rubble. So physical displacement can be excluded.

However: as we learnt from case of U2 both the equipment hatch plug and the top concrete plug/containment cap likely released pressure: and in case of U3 steady steam plumes were spotted on the early videos around the reactor well. It's not known if they were from the RPV or the drywell, but possibly they can explain some wild radiation readings.

Ps.: U3 RPV is which is on atmospheric pressure, am I right?

IMHO yes. There was those steam plumes... And in those early days there was also the more mobile Iodine with the Cesium... I wonder if the birds were checked for contamination afterwards.

clancy688

We can certainly say that at least the JSDF did take those readings seriously. You only try your luck in filling the SFPs with dropped water from high altitude fly-overs if there's something so absolutely nasty in the air above the reactors that even hovering (and thus enormously improving your aim) for a couple of seconds is out of the question.

clancy688

Unit 4 Spent Fuel Pool:

http://ajw.asahi.com/article/0311dis...AJ201203080066 "Fukushima No. 4 reactor saved by upgrade mishap"

According to the article, there was no separator gate in place between the Spent Fuel Pool and the Reactor Well, allowing for 1000 additional tons of water to flow to the SFP. Was that fact already known?

zapperzero

News to me. Although the possibility of water flowing INTO reactor well has been discussed iirc.