westfield said:Can someone clarify that? Perhaps they meant via seals, penetrations etc, not directly through the PCV wall?
westfield said:Ditto for the authors stating that TEPCO backpeddaled from the May 15th press release regarding Unit #4 Hydrogen coming from Unit 3 via SGTS. The authors state that the next day TEPCO retracted the theory because because it found closed valves would preclude that possibility. Again, I'm not implying its not true, just where is the source.
tsutsuji said:http://www.nikkei.com/news/category...39797E3E2E2E2;at=DGXZZO0195165008122009000000 This is the first time Tepco is providing the government with a report gathering details on the accident. Concerning the cores, it repeats previous statements. Concerning spent fuel pools, it says "it can be thought that the fuel was not exposed above the water level". At unit 4, pool temperature rose up to 90°C and water level decreased to 1.5 m above fuel.
CaptD said:Question: Where is this leakage going, into the ground water table or almost immediately into the Pacific? I'm guessing that most is going into the Pacific!
2 Questions:rmattila said:The leak is inwards (=from groundwater to the buildings), not outwards.
CaptD said:2 Questions:
1. If the leakage is "Inward", then where is all the ocean pollution coming from?
CaptD said:I have a hard time imagining that much water flowing upward into the building from ground level, without some outside "change" in the geology of the landfill and or underlying ground,
like a new "crack" caused by the Big Quake.
CaptD said:Latest chart info 9/20/11:
http://atmc.jp/plant/rad/
Sept 19th Reactor 1 spiked 411 Sieverts.
Sept 20th Reactor 1 currently 192 Sieverts.
+
This chart shows #1 RPV pressure almost constant for last six days!
http://translate.google.com/translate?hl=en&sl=&tl=en&u=http%3A%2F%2Fatmc.jp%2Fplant%2Frad%2F
joewein said:That is not quite true: Since the RPV was vented into the S/C, the nuclear soup in there should have received a fair amount of fission products that give off decay heat. Nuclear decay, wherever it takes place in the buildings, is the only heat source around there. It's hard to say how much of the radioactive inventory is still in the core, how much is in the S/C and how much is in the flooded basements. The 4 Sv/h spot in unit 1 near where steam rises up from the S/C suggests to me that the S/C does still put out a lot of decay heat.
If the S/C temp goes up, it would suggest one of two things to me:
1) More radio-nuclides were washed out from the RPV by the added core spray water flow and that water somehow drained into the S/C at the bottom, increasing decay heat output there.
2) The added core spray resulted in more steam production (instead of conduction via the hot RPV metal), more steam condensation in the dry well and a larger flow of still hot condensate from there down into the S/C.
If that data is reliable and D/W radioactivity decreases while S/C radioactivity goes up, perhaps it means that fission products are getting flushed into the S/C, as per the first of my 2 theories.
In unit 2 the S/C is supposed to have ruptured. If radioactivity gets washed into the S/C from the RPV or D/W there's a good chance it will leak from there into the basements. In the best case it will eventually end up in the cesium sludge filters of the Areva/Kurion and SARRY plants. In the worst case it will end up in the soil or ocean.
joewein said:If the S/C temp goes up, it would suggest one of two things to me:
1) More radio-nuclides were washed out from the RPV by the added core spray water flow and that water somehow drained into the S/C at the bottom, increasing decay heat output there.
2) The added core spray resulted in more steam production (instead of conduction via the hot RPV metal), more steam condensation in the dry well and a larger flow of still hot condensate from there down into the S/C.
HowlerMonkey said:I would think any salt that accumulated during the seawater pumping would eventually hitch a ride on the now fresh water that is being pumped through leaving little or no salt in the reactors.
The fuel would be mostly oxide, or hydrated oxides, which don't burn. Besides, it has not been determined that there is molten fuel outside of the pressure vessels.robinson said:If they drain the basements, what will keep the melted fuel from catching on fire?
joewein said:True, but it's going to be a slow process if the current pattern of water treatment doesn't change.
I guess eventually, when the water treatment plants work well enough they will go for complete drainage of the basements, at least once, because that will make the desalination much more efficient.
Astronuc said:At the moment, I don't see a 'real' chance of a meltdown. It is a worst case scenario, which is what licensing space is all about.
Astronuc said:At the time of the explosion, the wind was apparently moving toward the northeast, so any vapor would be carried out to sea.
However, I understand that the building where the explosion has occurred is not associated with containment, but I have not been able to verify this.
Astronuc said:I doubt the fuel will melt - but it might break into pieces - which will be trapped by the channels and bottom tie plate. The control rods may still be intact.
.Astronuc said:would be mostly oxide, or hydrated oxides, which don't burn.
SteveElbows said:If more core entered the basement, we would expect suppression chamber to be affected?
robinson said:If they drain the basements, what will keep the melted fuel from catching on fire?
Most Curious said:Not sure I understand you. If filtered, desalinated water is being pumped into the RPV, what difference does it make about basement water?? I assume salt removal from the RPV (where we assume a lot was deposited) is what is desired??
tsutsuji said:http://www3.nhk.or.jp/news/genpatsu-fukushima/20110920/index.html Because the contaminated water level in buildings is not decreasing as quickly as the water treatment flow rate suggests, Tepco has calculated an estimate of the amount of ground water leaking every day into the buildings: from 200 to 500 tons. Tepco's thought is to keep the water level in buildings just below the ground water level. The NISA says "It is necessary that the long term contaminated water treatment plan takes into account the ground water leak rate. The amount of ground water changes with seasons, and we want to evaluate this".
MiceAndMen said:I think there are a few people who have an erroneous mental image of where these so-called "basements" are under the reactor buildings (not talking about the turbine or other support buildings here, only the reactor buildings proper).
Once again, there are not excavated underground rooms or chambers directly underneath the RB structures enclosing the primary containment vessels. There is nothing directly under those except concrete and Earth (and possibly a layer of sand directly under the bottom of the steel shell).
The supression chamber encircles each PCV and sits in an annular excavation of sorts. Other than this circular cut-out that contains the SC and its supporting structures and equipment, there is no other "basement" to speak of.
With this in mind, it is impossible for corium that may have flowed (or dropped) out of the RPV to migrate downward and into the torus excavation. The drywell's vent pipe arrangement would not permit that to happen.
I apologize for the tone, but all this talk about corium eating its way through the lower extremities of the drywell and somehow ending up "in the basement" makes absolutely zero sense according to my understanding of the physical layout of the reactor buildings. It could go into the concrete substrate underneath the PCV, or into the Earth beyond the structural foundations of the buildings... but there is no basement direcly under the drywells.
Should the liner fail near the drywell floor elevation, the most probable sites for blowdown entry into the secondary containment are the reactor building basement torus room and the second floor of the reactor building (Exhibit 2). The transport path for the blowdown is the gap between the drywell shell and the surrounding reactor building concrete, and the annular gaps surrounding the drywell vent pipes and penetra- tions. These gaps provide a 145 ft2 (13.5 m2) flow path into the torus room and a 135 ft2 (12.6 m2) flow path into the second floor of the reactor building. Since elevated drywell pressures and temperatures result in swelling of the drywell liner and a reduction in the gap between the liner and the reactor building concrete (Exhibit 3), it appears that the etfective flow path area for drywell blowdown would be limited by the actual size of the drywell shell rupture or the available space between the liner and the surrounding concrete
But the IF statement is incorrect.zapperzero said:So, I think your remark needs qualification:
If the fuel has never reached temperatures high enough to become reduced to metal form then itBut of course, we do not have enough information to support OR definitively deny. So we speculate.Astronuc said:would be mostly oxide, or hydrated oxides, which don't burn.
The paper mentions "a wide range of hypothetical core melt scenarios." It does not address plausibility or possibility. The group is charged with considering hypothetical, often worst-case, scenarios - no matter how implausible they might be. It would be like an automotive engineer crash testing a car at 200 or 300 mph, when the top speed would be 120 mph due to engine limitations and drag.SteveElbows said:OK I'm going to go one better, with a report that explores the possibility of molten core penetrating the drywell.
http://www.osti.gov/bridge/servlets/purl/6250306-2XRtiq/6250306.pdf
What becomes clear when reading this document, is that the possibility they are exploring is not about the core traveling downwards from the pedestal area, but what happens if there is enough of it, at sufficient temperatures, to travel outwards, reach a steel wall and melt through it pretty quickly.
As they point out, there are a good number of factors which can prevent this theoretical scenario from happening, e.g. if the temp isn't high enough or there isn't enough of it to reach the wall, or if it travels downwards through concrete quite quickly then there won't be enough of it left higher up to reach the steel walls. But at the time this report was written many years ago, it sounds like this was a new scenario that hadn't been properly considered before, and they decided it was plausible enough to add it to the list of possible failure modes (some of the others are mentioned in the report).
joewein said:I see your point. Yes, if we're talking about the salt in the RPV, it doesn't matter one bit whether the basements are drained completely or not. My point was about the larger volume of salt in the 100,000t or so of water in the basements. I am concerned about that because of metal corrosion and because of effects it may have on the concrete of the structure.
For the RPV, if water injected into the core leaks out via either the presumably damaged recirculation pump seals or through damage to the RPV bottom from melting fuel, then the salt probably has already been flushed out. Only if the RPV bottom was completely intact and the cooling water boiled off before it reached a level high enough to leak via the pumps or other pipes should there still be significant amounts of salt in the RPV.
The minimum flow of 3.8 m3 per hour (units 1 and 2 in recent months) amounts to 90 t of water a day, which could dissolve about 30 t of salt per day (assuming none of it boiled off). It's been about 180 days of fresh water cooling so far, so even if the vast majority of the cooling water had escaped as steam rather than liquid the rest should have been enough to flush out the accumulated salt.