- #9,906
robinson
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A diagram of what the Fukushima reactor buildings/design actually look like would be really helpful. Or rather, what they used to look like. I know for a fact none of the one published yet are totally accurate.
Thank you joewein. If that is the skimmer tank, the indicated position confuses me. As I had made for myself a mental map of the set up, excess water would leave through openings at top edge of the pool, to be collected in surge tank(s) placed under deck on one or on either side of the fuel transfer chute.joewein said:I believe that's the skimmer tank. Every SFP has one.
To prevent any possibility of the pool draining from a ruptured pipe or from siphoning, there is no pipe connected to the bottom of the pool. Instead the water circulation system uses the skimmer tank such that when cold water gets added to the main pool it raises the level until it overflows into the skimmer tank, from where it is pumped into the heat exchanger (and from there back into the main pool).
SteveElbows said:Looks like the new plan to provide unit 4 fuel pool cooling involves a pretty basic solution, attaching the end of a hose to some railings on the refuelling bridge.
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110616_03-e.pdf
biggerten said:I'm sure they will, but just so it's said, I hope they have check valves installed so that the 'solution' does not become a siphon and drain the pool should a failure occur....
Were designed to operate safely for 40 years?zapperzero said:were designed for ultra-pure water.
zapperzero, I think you have provided some of the best descriptions of the condition of the corium - this was also yours:The likeliest scenario is that the molten corium is now covered in a solid crust, due to having been cooled constantly and being a rather poor conductor of heat in the first place...
I imagine that "crust" to be fairly thick already.zapperzero said:he corium does not exist in beautiful isolation anyway Lots of things could be sending neutrons back into the corium. The steel. The water. The miscellaneous stuff that's IN the water. The crust around the corium, which is of uncertain composition and density.
etudiant said:Is this just the first step?
Was not the plan to restore the cooling of the pool by recirculating its water through a heat exchanger?
Thus far, nothing is indicated beyond a simple replacement of the pumper vehicle. Has there been any detail on the rest of the installation, including the heat exchanger and the tap from the skimmer pool?
Quim said:Were designed to operate safely for 40 years?
Quim said:I imagine that "crust" to be fairly thick already.
I think it is if you consider particles which land on top of the corium pile(s) to be part of that crust. (Could it be that the salt from the early saltwater injections is now providing a beneficial contribution to the "crust" surrounding the corium?)Jorge Stolfi said:It is not obvious that the crust will get thicker with time.
The corium is not just hot, it is generating heat continuously. To a first approximation the crust thickness should be constant, defined by an equlibrium between the power generated by the radioactivity inside it and the power absorbed by the boiling of water outside it.
However, the boiling water may be slowly eroding the oxides in the crust, so it may even be getting thinner with time. And if it were to get dry, it would probably melt completely, perhaps in a matter of minutes.
Ms Music said:Is the presence of corium a fact?
Those readings are not from inside the reactor pressure vessel (RPV) but from the primary containment (the bulb-shaped "drywell" and the donut-shaped "surge suppression chamber") . In normal conditions, those spaces may not be "clean" but (AFAIK) may have to be entered occasionally by people for repairs. Moreover the air/steam/whatever in them may have to be vented to the atmosphere. Thus it makes sense to use sieverts to measure the contamination of the gas in the primary containment.robinson said:Can someone remind me why radioactivity inside a reactor is displayed in human dose units?
Since the power failed, only a handful of analog instruments have been working, sort of. The CAMS meters are pipes that take a sample of the air in the containment and bring it to some location further out in the building, where its radiactivity is evaluated by some automatic equipment. The CAMS meters were obviously not meant to diagnose meltdowns, but they are the only info we have about the radioactivity inside the primary containment.robinson said:And how can they know, without a detailed analysis of the different sources, what the Sieverts would even be? You have to multiply by different units to get Sieverts. Wouldn't they want to know the actual level of radioactivity in there?
clancy688 said:Did anyone notice the abnormal behavior of the Unit 1 Drywell Radiation sensor?
Jorge Stolfi said:In normal conditions, those spaces may not be "clean" but (AFAIK) may have to be entered occasionally by people for repairs.
Jorge Stolfi said:Since the power failed, only a handful of analog instruments have been working, sort of. The CAMS meters are pipes that take a sample of the air in the containment and bring it to some location further out in the building, where its radiactivity is evaluated by some automatic equipment. The CAMS meters were obviously not meant to diagnose meltdowns, but they are the only info we have about the radioactivity inside the primary containment.
SteveElbows said:But yes, I think its better to presume that CAMS is more useful for detecting much smaller amounts of damage that could occur under a situation much less dire than what happened at Fukushima.
MadderDoc said:One could say the concrete pump method used so far is also pretty basic. and then there is the KISS principle. The alternative sfp injection there presented is of course not in principle different than using the concrete pump and it should work just as well. As a practical matter it would mean less obstruction for the ongoing work at the south face of the building to null the need to have the concrete pump around.
As an aside (see attachment) -- there is a square structure indicated in the drawing at what would be the east side of the unit 4 pool. I wondered if there is any significance to that depictured detail, as regards how the unit 4 pool set up is or is to be actually configurated. (The sketch could of course be of a generic pool and not refer in such specifics to the unit 4 pool.)
I think the confinement will be complete once they stop pouring water on it. I believe that once the corium reaches temperature equilibrium with its surroundings, a dry region will be created around it after the last of the water evaporates off the region which remains above 100 C.razzz said:Not that it will be complete confinement since groundwater flows at will to corium unless the entire site is de-watered like, forever more.
SteveElbows said:They used CAMS to try to estimate percentage core damage early on, and I don't think the numbers generated were well regarded by people at the time.
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110427e19.pdf
If these percentages referred to amount of fuel that's ended up in containment, rather than the percentage of fuel that was damaged, then maybe I could buy into the numbers a bit. But yes, I think its better to presume that CAMS is more useful for detecting much smaller amounts of damage that could occur under a situation much less dire than what happened at Fukushima.
MadderDoc said:I wonder if anyone here has been able to identify where this photo was taken?
http://www.tepco.co.jp/en/news/110311/images/110611_05.jpg
In the Tepco handout page the photo has this mysterious caption which does not really make any sense:
"Side Part of Skid of Water Treatment Facility of Fukushima Daiichi Nuclear Power Station
(pictured on June 9, 2011)
Pictured at South Side on 4th floor of Unit 4 Reactor Building"
biggerten said:I hope they have check valves installed so that the 'solution' does not become a siphon and drain the pool should a failure occur....
biggerten said:I'm sure they will, but just so it's said, I hope they have check valves installed so that the 'solution' does not become a siphon and drain the pool should a failure occur....
westfield said:At first the pattern of the sun shining in there made me think the photo is facing west (ie the photographer has basically turned 90 degrees to his right after taking http://www.tepco.co.jp/en/news/110311/images/110611_04.jpg" shot ) but so far I havn't found a match from the outside.
But then there is an "I" beam rail up at the ceiling with a chain block at the end of it which appears as though it mayt extend outside the building, which made me think of the green scaffolding that was set up on the eastern side of Unit 4 before all this happened. However, I thought that was one level down. But if it is facing east that would mean the sunlight is shining in from a northerly angle which doesn't seem right does it?
CaptD said:New question for PF Newbie
On this thread;
http://www.huffingtonpost.com/2011/...ment-radiaton-estimate-doubles-_n_871887.html (which now has over 6100 comments)
See comment today at 7:27, 3:47 and 9:39
☆ A number of us have been discussing what is causing the chart to look like this:
...We have two different ideas: http://atmc.jp/plant/rad/?n=1
clancy688 said:Yes. According to TEPCO and NISA, the fuel rods in Units 1-3 melted down, probably totally. Corium is a mixture out of control rods, fuel cladding, fuel elements, and, in case the reactor was breached, steel and concrete. Basically everything which mixed with the molten fuel.
But since there's molten fuel present, there's also corium.
MadderDoc said:My best idea is that the numbers in the press article might be a -- perhaps somewhat positively skewed -- representation of data as it looked a few days ago, maybe when a Tepco application was made to authorities -- I imagine opening the reactor building to the environment would be one of those things that the utility would need official permission to do.
It seems clear from the Tepco press releases, that the full data set you reference includes the time for initiation of the air purification, quote Tepco,
"-We installed local exhausters and started to operate them at 12:42 pm on
June 11 in order to improve the working environment inside Reactor
Building of Unit 2."
and the full dataset then does not seem to support that there has been a reduction of the Cs isotopes over the period of operation so far, nor that the reduction of I-131 has had the magnitude expressed in the press article.