Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[dezzert]

Has there been anything published on the effects of salt water cooling for a disintegrating core?

Thanks Rive and etudiant. To add to the above, another question, what is the effect of salt in the R3 and R4 SFPs. The photos don't show much, but there would have to be some if Tepco's analysis of no leaks in the pools is correct, and steaming is the sole lose of water during the period they were using seawater. And this salt wouldn't have reached it's melting point.

 

[LabratSR]

Atomic Power Review update on some testing done by TEPCO.

http://atomicpowerreview.blogspot.com/2011/09/fukushima-daiichi-reactor-update.html

 

[CaptD]

WSJ: Tepco needs to find ways to prevent new nuclear reactions — May happen if fuel not adequately cooled — “Containme*nt vessels are largely empty of water” after leakage -Sept.14,2*011
http://ene*news.com/w*sj-tepco-f*ind-ways-p*revent-new*-nuclear-r*eactions-c*ould-happe*n-fuel-ade*quately-co*oled-conta*inment-ves*sels-large*ly-empty-w*ater
snip
[...] The most difficult challenge facing Tepco is how to plug leakages in the primary containmen*t structures [...]

The primary containmen*t vessels, the main shield against radiation leaks, and the reactor buildings that house them, have been damaged [...]

The leakage means that the containmen*t vessels are largely empty of water [...]

Tepco also needs to find ways to prevent any new nuclear reaction, which could happen if the fuel is not adequately cooled during the entire process.

 

[SteveElbows]

Any thoughts on why the temperatures measured at reactor 2 suppression chamber have been creeping slowly upwards?

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11091912_temp_data_2u-e.pdf

 

[Shinjukusam]

Any thoughts on why the temperatures measured at reactor 2 suppression chamber have been creeping slowly upwards?

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11091912_temp_data_2u-e.pdf

Just a thought, but they did change the delivery method of water in that reactor late last week. Possibly the suppression chamber is getting less water than before.

 

[Rive]

Possibly the suppression chamber is getting less water than before.

The suppression chamber has no heat generation of its own: so if its temperature is rising then it gets more heat (from the core).

 

[Shinjukusam]

The suppression chamber has no heat generation of its own: so if its temperature is rising then it gets more heat (from the core).

Well, what I meant was that if the injection vector has changed than that area may be getting a different flow, hence being affected differently.

 

[Azby]

If this was already posted and I missed it, my apologies.
An interesting report on the accident co authored by one of the designers of RPV of Unit 3.

TECHNICAL REPORT: FUKUSHIMA ACCIDENT SUMMARY (AUG. 19, 2011)
Association for the Study of Failure

http://www.shippai.org/images/html/news559/FukuAccSummary110819Final.pdf

 

[SteveElbows]

Well, what I meant was that if the injection vector has changed than that area may be getting a different flow, hence being affected differently.

Well I've been looking at the data. Suppression Chamber temperatures stopped declining, and started to slowly rise, around August 31st. This was just a few days after the sudden leap in recorded RPV Bellows temperature, which was mentioned on this thread, with an official explanation that it was probably an instrument malfunction.

The pace of the suppression chamber temperature rise appears to have increased as September has gone on, with quicker climbs in recent days. Reactor Suppression Chamber Gas temperatures have also gone up a few degrees in recent days.

And then I looked at the CAMS data for the first time in months. Drywell CAMS A has been falling more quickly in recent days, and both S/C CAMS A and CAMS B have risen. In the case of the B readings, its risen by almost 1 Sv/h in the last 6 days.

I need to look at slightly older data and do some graphs in order to firm up my impression of the data, but I find this stuff interesting.

 

[LabratSR]

If this was already posted and I missed it, my apologies.
An interesting report on the accident co authored by one of the designers of RPV of Unit 3.

TECHNICAL REPORT: FUKUSHIMA ACCIDENT SUMMARY (AUG. 19, 2011)
Association for the Study of Failure

http://www.shippai.org/images/html/news559/FukuAccSummary110819Final.pdf

Interesting. Thanks!

 

[Caniche]

If this was already posted and I missed it, my apologies.
An interesting report on the accident co authored by one of the designers of RPV of Unit 3.

TECHNICAL REPORT: FUKUSHIMA ACCIDENT SUMMARY (AUG. 19, 2011)
Association for the Study of Failure

http://www.shippai.org/images/html/news559/FukuAccSummary110819Final.pdf

"the situätion with the spent fuel is not clear". Oh Oh

 

[clancy688]

http://www.shippai.org/images/html/news559/FukuAccSummary110819Final.pdf

Interesting statements about Unit 1 on March 12th:

02:45: RPV pressure decreased from 7.0MPa to 0.95MPa, on the other hand, PCV pressure increased to 0.95Mpa. This means that RPV broke, and its pressure dropped to the same with PCV.
Where did the RPV Break?
Very high radiation was observed in the TIP (Traversing In-core Prove) room of F1 (Figure 7). Oak Ridge National Laboratory (ORNL) reported that the instrument guide tube is the weakest point at the bottom of RPV [6]. So, we estimate that several instrument guide tubes were broken, and some portions of fuel pellets fell down to the bottom of PCV through these holes. Small portions of fuel pellets reached the 1st floor of the reactor building. That is, PCV was also broken.

08:30: 3 months later, Government released a very important piece of information. At 08:30 of March 12th, Te(Tellurium)-132 and its daughter Iodine-132 were observed 7km away from Fukushima reactors. Vaporizing temperature of Te is about 988deg.-C, and this was an evidence that the temperature of fuel pellets reached over 1,000deg.-C. The reason why the Government did not immediately open this information is not clear. If this news was open on March 12th, the following remedies might have been better, or at least we could have recognized the status of the reactors correctly.

Haha. Anyone remembers the government spokesperson who told the press at March 12th that the government was suspecting a meltdown? The government didn't use him again for statements and denied any meltdowns.

 

[joewein]

The suppression chamber has no heat generation of its own: so if its temperature is rising then it gets more heat (from the core).

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.

Well I've been looking at the data. Suppression Chamber temperatures stopped declining, and started to slowly rise, around August 31st. This was just a few days after the sudden leap in recorded RPV Bellows temperature, which was mentioned on this thread, with an official explanation that it was probably an instrument malfunction.

The pace of the suppression chamber temperature rise appears to have increased as September has gone on, with quicker climbs in recent days. Reactor Suppression Chamber Gas temperatures have also gone up a few degrees in recent days.

And then I looked at the CAMS data for the first time in months. Drywell CAMS A has been falling more quickly in recent days, and both S/C CAMS A and CAMS B have risen. In the case of the B readings, its risen by almost 1 Sv/h in the last 6 days.

I need to look at slightly older data and do some graphs in order to firm up my impression of the data, but I find this stuff interesting.

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.

 

[westfield]

If this was already posted and I missed it, my apologies.
An interesting report on the accident co authored by one of the designers of RPV of Unit 3.

TECHNICAL REPORT: FUKUSHIMA ACCIDENT SUMMARY (AUG. 19, 2011)
Association for the Study of Failure

http://www.shippai.org/images/html/news559/FukuAccSummary110819Final.pdf

It's unfortunate that the authors contradict themselves regarding the EDG locations and then still get it wrong. Also unfortunate that some of the claims don't have sources listed - like "Very high radiation was observed in the TIP (Traversing In-core Prove) room of F1 ". I'm not saying it's not true but with no source it makes the document hard work.

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. (Regarding that subject, can anyone say why hydrogen from the supplies in the turbine building has not been brought up as a possibility as the source for the Unit 4 RB hydrogen? Not enough stored there? It would seem a slightly more plausible path as opposed to a path from Unit #3)

Also the authors apparently not understanding the major construction difference between the upper part of the RB of Unit 1 and all the other RB's is not indicating a good general knowledge of the Fukushima daichi plant. They state Unit 1's walls as concrete. They also seem to not understand the function of blowout panels, instead implying that ALL the walls are designed to blow out. Yes, they certainly should have talked to a GE engineer as they state.

There are other problems with statements in the document but to be fair there are problems with the grammar in the document so some information seems to have not come across very well. If it was rewritten with all sources listed and theories clearly demarked then it would read a lot more credibly.

Thanks for the link.

EDIT: Another Quote from the document "Another cause is the small size of hydrogen gas molecules. They can easily penetrate PCV walls. "
Is that true? On that basis how can we keep hydrogen in ANY container?

Can someone clarify that? Perhaps they meant via seals, penetrations etc, not directly through the PCV wall?

 

[westfield]

Interesting statements about Unit 1 on March 12th:





Haha. Anyone remembers the government spokesperson who told the press at March 12th that the government was suspecting a meltdown? The government didn't use him again for statements and denied any meltdowns.

Did the government actually deny there may be meltdown\s at that period of time?, I can't remember any denials but it was a while back.

Also, I don't see the quoted authors point, so what if the government\tepco had released that information on the 12th March, why would issuing a press release have changed TEPCO's immediate strategy in dealing with the disaster?

 

[zapperzero]

Can someone clarify that? Perhaps they meant via seals, penetrations etc, not directly through the PCV wall?

Dunno what they meant, but hydrogen does indeed diffuse through just about anything you'd care to name, steel included. I doubt very much that this had any effect, though. There are myriad faster possible paths.

 

[tsutsuji]

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".

 

[tsutsuji]

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.

I would like to know their source too. This "retracting the next day" story reminds me another story about the unit 1 explosion analysis. On 4 June the Asahi had a story of hydrogen flowing backwards from the exhaust stack into unit 1 reactor building : http://www.asahi.com/national/update/0603/TKY201106030574.html then on the next day, on 5 June, the Asahi reported that Tepco had found that one of the concerned valves was built to close automatically if electric power is lost, so that the possibility that it was open is "extremely low" : http://www.asahi.com/special/10005/TKY201106040552.html

The hydrogen flow from unit 3 to unit 4 theory was stated in the Japanese government to IAEA report in June, and again in late August when Tepco analysed the radiations of the filters : "Result of Radioactive Dose Measurement at Unit 4 Emergency Gas Treatment System in Fukushima Daiichi Nuclear Power Station": http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110827_02-e.pdf (27 August).

http://www.shippai.org/images/html/news559/FukuAccSummary110819Final.pdf "It is difficult to determine what happened in F4 from the above contradicting observations, but it is likely that there was some kind of dry-out and failure with the fuel". Dry-out is refuted by Tepco's September report :

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.

http://www.asahi.com/national/update/0914/TKY201109140511.html 14 September: A Tokyo university research team has presented an analysis supporting the view that hydrogen produced in unit 4 spent fuel pool is one of the causes of the explosion. It does not demolish Tepco's theory that hydrogen flowed from unit 3 to unit 4, but it checks how much hydrogen from the pool might have contributed to the explosion. They mocked up the reactor building with an iron box, put boiling water in it and exposed it to radiations. Pushed by the steam pressure, hydrogen concentrates against the wall and exceeds explosive concentration level. Until now, Tepco has explained unit 4's explosion as resulting of hydrogen flowing backwards during the venting of unit 3.

 

[CaptD]

To: tsutsuji RE Your Post 11267
The link (translation) only describes general conditions, do you have a better link that describes the leakage you mention? Yours is the first I've seen to quantify the amount of leakage, which I've been thinking is "Massive" but nowhere as large as "from 200 to 500 tons"! Great Post! Thanks!

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!

 

[rmattila]

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!

The leak is inwards (=from groundwater to the buildings), not outwards.

 

[CaptD]

The leak is inwards (=from groundwater to the buildings), not outwards.

2 Questions:

1. If the leakage is "Inward", then where is all the ocean pollution coming from?
2. 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.

BTW: That would be a real "gusher" especially since all of the "cooling water being injected, would serve to raise the water level inside the reactor containment building.

Perhaps a new crack caused by the Quake?

Thanks

 

[CaptD]

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

 

[tsutsuji]

2 Questions:

1. If the leakage is "Inward", then where is all the ocean pollution coming from?

This was last discussed in the other thread at https://www.physicsforums.com/showpost.php?p=3491491&postcount=288

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.

The water level in basements is supposed to be lower than the ground water level in nearby ground, so that the ground water seems to flow downward, not upward. If deep enough, a basement, like a well, naturally fills with water.

 

[SteveElbows]

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

That CAMS sensor for reactor 1 has been fluctuating wildly for many months now, so the spikes are not interesting. The other drywall CAMS sensor for reactor 1 broke completely a few months back so its even less easy to ascertain what's happening on that front.

Pressure readings have not fluctuated much for ages either, so I don't think that data deserves an exclamation mark.

 

[HowlerMonkey]

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.

 

[SteveElbows]

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.

Cheers for this response, these were the kinds of things I was wondering about.

Given that the change in temperature trends that I commented on started well before alternative spraying started at reactor 2, I have been looking for other possibilities. I note that they have sometimes had to adjust the water flow rate in recent month or so, because its fallen lower than they intended, so I suppose its possible that fluctuations in this could lead to a similar disturbance & relocation of material or changes in water/steam flows.Or perhaps some other thing else caused some kind of change around the end of August, perhaps an earthquake or some other work. I suppose I should also consider whether the nature of the water being injected has changed, e.g. is it warmer than it used to be, but in that case I would expect to see similar trends at the other reactors.

My main reason for interest in this stuff is that since reactor 2 was blamed for around 90% of the total radioactive release, it is of most interest to me. Given the likely location of the explosion there, and a report that suggested that some corium that escaped the reactor vessel could well find its way down to the basement that the suppression chamber lives in, I am interested in what's going on down there. And since I haven't seen similar temperature trends before (most rises being of the spike variety rather than a gradual climb), I thought I may as well draw attention to it.

I should probably also consider the possibility that the data we have about the suppression chamber may actually reflect changes to the conditions in the basement rather than the suppression chamber directly. e.g. If more core entered the basement, we would expect suppression chamber to be affected?

 

[Rive]

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.

Regarding the second option: IMHO it's possible to give a rough estimate about the amount of core still within the shroud through the dT/dt rate (torus capacity) and the remanent heat.

 

[SteveElbows]

Perhaps I should think more about the possibility that the water being injected is now following a path that means some of it is picking up more heat before ending up draining down into the suppression chamber, so warmer water is entering the suppression chamber, rather than being warmed more once it reaches that location?

There are very tentative signs that suppression chamber temps at reactor 3 might just have started to nudge up, but its many days too soon to make this claim seriously, and all of the rises I have been talking about are small, so I don't want to overstate my point.

Anyway as regards reactor 3 the other temperatures are surely more interesting right now, seeing what they are able to achieve with really quite high rates of water injection via the CS system at the moment. Its made quite a large difference so far, and recently they are placing even more emphasis on the pseudo-'cold shutdown' achievement that they always harp on about. So they would probably like to be able to have this flow rate on a sustained basis in order to produce numbers that look comfortably below 100 degrees C, but with the water treatment facilities as trouble-prone as they are, its likely not the easiest of balancing acts to get right.

 

[joewein]

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.

True, but it's going to be a slow process if the current pattern of water treatment doesn't change.

If the basements were drained by pumps as far as possible, there would be little salt left there. However, as long as the goal remains only not to let the basements overflow, with say 20,000 tons left sitting there and maybe 200 tons pumped out of each unit per day, as much as would be reinjected for cooling or leaking in from ground water, then it would merely be diluted by 1% per day. Since 0.99 ^ 69 = 0.5, the salt content would drop by half in a little over 2 months, or to a quarter in a little under 5 months.

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.

For spent fuel pools they will have no choice but go for gradual dilution, because complete drainage followed by refilling is not an option.

 

[robinson]

If they drain the basements, what will keep the melted fuel from catching on fire?

 

[Astronuc]

If they drain the basements, what will keep the melted fuel from catching on fire?

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.

 

[Most Curious]

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.

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??

 

[zapperzero]

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.

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.

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.

I think what I am trying to show here is that in the absence of hard data, you are naturally biased towards optimism. Not that I think it is a bad bias to have, mind you.

So, I think your remark needs qualification:

If the fuel has never reached temperatures high enough to become reduced to metal form then it

would be mostly oxide, or hydrated oxides, which don't burn.

.
But of course, we do not have enough information to support OR definitively deny. So we speculate.

 

[zapperzero]

If more core entered the basement, we would expect suppression chamber to be affected?

If there's core on the floor (which is still a rather big if), I cannot see how it would go anywhere other than straight down, rather than flowing outwards (and upwards, I think?) to the S/C.

 

[MiceAndMen]

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.