Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[jim hardy]

zz wrote: ""...but I do seriously think that there is some corium, based on the high temps still being recorded by the various RPV sensors, much higher than for the other two reactors.""

i guess the giveaway would be how much water it's turning into steam.
But that's a difficult number to know if a lot of what they pump in goes into the basement as water instead of coming out the top as steam.

Were I manning the pumps i'd try to inject just enough water to carry away the expected heat then cut back to the point i had fifty degrees or so of superheat. That'd assure the steam coming out is dry , hence mostly distilled water molecules not water droplets. That'd minimize the amount of little radioactive friends that tag along with the steam.


I'll not attempt a calc here - i work with sliderule and BTU's but the rest of world uses EXCEL and metric system.
As George Gobel said - "Ever feel like the world is a tuxedo and you're a pair of brown shoes?"

 

[tsutsuji]

http://www.yomiuri.co.jp/science/news/20110629-OYT1T00850.htm and http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110629_02-j.pdf : The water treatment facility was stopped at 2:53 PM after an alarm signalling a leak at the site bunker building (1) rang. It had been also stopped for flushing and adsorption tower replacement between 10:45 AM and 2:13 PM. The reason why the alarm rang is under investigation.

(1) the orange box on http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110627_01-e.pdf

http://www.asahi.com/national/jiji/JJT201106290077.html : The facility was started again at 9:15 PM.

 

[clancy688]

Is that correct? All four reactors are still releasing steam to the atmosphere. That steam is water that boiled off in contact with the molten cores and/or SFPs, hence it must not be quite Perrier. Are there any estimates of the amount of radioactivity that is being released that way?

Back in April, the daily emissions were estimated at 154 TBq (after iodine conversion).

http://ex-skf.blogspot.com/2011/04/fukushima-i-nuke-plant-154.html

Since then I've heard of no new estimates for daily discharges. Still I'd take that number only as a "worst case" for June, since better cooling certainly had a positive effect on those discharges.

After 100 days, we're at an additional 15.000 TBq. Compared to the 770.000 TBq, that number is fairly small. It won't change the overall situation.

Saying that the number "won't go up" was a mistake on my behalf, sorry for that. I rather meant that the ongoing releases won't change much since they're very mall compared to the initial first week release.

 

[tonio]

My point is, underground water moves slow enough so that there is no need to deal with it _right now_, when we have much more pressing issues (like continuing releases of radioactive steam, overflowing basements with 1 Sv/h water and such).

Based on what information do you think that? I assume that the part of the plant nearest to the sea is built on a bed of rubble, bulldozed into the sea. Such material tends to be quite permeable. Furthermore, (artificial) preferential pathways into the sea may exist. What I mean to say is that it is well possible that (part of) the contaminated ground water may reach the sea much quicker than you think.

 

[~kujala~]

The information regarding the speed of groundwater flow has come from TEPCO itself:

Underground water flows at a speed of about 5 to 10 centimeters a day, so we have more than a year before it reaches the shore.

http://mdn.mainichi.jp/perspectives/column/archive/news/2011/06/20110620p2a00m0na005000c.html

But I don't know how extensive their investigations regarding the groundwater properties has been.

A couple of years ago they planned a big survey concerning the soil characteristics of Daiichi/Daiini:
http://www.tepco.co.jp/en/press/corp-com/release/betu07_e/images/071105e1.pdf

Groundwater level observation was part of the planned survey. They planned 13 shallow boring holes, depth 10 - 20 m. According to the map some of the shallow boring holes were quite near the sea.

Perhaps this survey also gave TEPCO some information concerning the speed of groundwater flow?

Now that there has been a big earthquake I think they have to re-examine the soil characteristics of Daiichi?

 

[tsutsuji]

http://www.chunichi.co.jp/s/article/2011062990203609.html : On 30 June, Tepco plans to begin transferring the accumulated water from unit 6 into the megafloat barge.

 

[tonio]

A couple of years ago they planned a big survey concerning the soil characteristics of Daiichi/Daiini:
http://www.tepco.co.jp/en/press/corp-com/release/betu07_e/images/071105e1.pdf

Groundwater level observation was part of the planned survey. They planned 13 shallow boring holes, depth 10 - 20 m. According to the map some of the shallow boring holes were quite near the sea.

Perhaps this survey also gave TEPCO some information concerning the speed of groundwater flow?

Now that there has been a big earthquake I think they have to re-examine the soil characteristics of Daiichi?

OK, that's interesting. They indicated that these boreholes are also meant for groundwater level observation, which means that they are probably provided with piezometers. Thus it is simple to assess the slope of the groundwater table. Assuming that they also assessed the borehole profiles (type of soil/rock) and possibly also did some well tests (assessment of permeability), they are also able to assess the ground water flow speed.

On the other hand, as far as I know one or more reactors are provided with ground water extraction systems, in order to keep their basements from flooding with ground water. If this is correct and if they monitored the amount of extraction on a regular basis:
- They have another means to assess the permeability of the soil/bedrock.
- Assessment of the present ground water table (and thus flow speed) is probably unreliable as it is disturbed by these extractions and in a phase of adjustment (i.e. increasing flow speed), probably even if the extractions were halted after the tsunami.
- More important: they are provided with a simple ground water remediation system: use the extractions to withdraw the contaminated groundwater and to lower the ground water table to somewhat below sea level, and you have a simple means to minimize inflow of contaminated groundwater into the sea. On the other hand, extra water purification capacity is then required.

 

[etudiant]

OK, that's interesting. They indicated that these boreholes are also meant for groundwater level observation, which means that they are probably provided with piezometers. Thus it is simple to assess the slope of the groundwater table. Assuming that they also assessed the borehole profiles (type of soil/rock) and possibly also did some well tests (assessment of permeability), they are also able to assess the ground water flow speed.


- More important: they are provided with a simple ground water remediation system: use the extractions to withdraw the contaminated groundwater and to lower the ground water table to somewhat below sea level, and you have a simple means to minimize inflow of contaminated groundwater into the sea. On the other hand, extra water purification capacity is then required.

Perhaps the groundwater is what TEPCO has in mind for the other 125,000 tons of water they plan to treat.
AREVA noted that the plan was to process 250,000 tons of water, even though there is a bit less than half as much in the plant currently.

 

[Luca Bevil]

They have to leep cooling the reactors. That should account for much of the remaining processing tons.

 

[joewein]

TEPCO reports finding Tellurium-129 (Te-129, half life 70 minutes) in early June, writes http://ex-skf.blogspot.com/2011/06/fukushima-i-nuke-plant-radioactive_29.html" :

Then, on page 99 for the test results for the samples taken on June 12:

Te-129 (half-life 70 minutes): 230 becquerels/liter, outside the silt fence in front of the Reactor 4 water intake canal.

Te-129 was also found in the deep seawater 8 kilometers off the coast of Minami-Soma City and Onahama on June 7 (pages 27, 28) and June 9 (page 39) separately.

A substance with more than 20 half lives per day, i.e. where less than 1/1,000,000 remains after one day, found some 80 days after shutdown, up to 40 km south of F1? Oh really?

What's even weirder is that it is identified in samples where *no* I-131 or Cs-134 or Cs-137 was found. Frankly, I have my doubts how reliable those tests are.

 

[jim hardy]

TE129 mas a "metastate" where it can hide out, with a halflife of 33.6 days.

http://environmentalchemistry.com/yogi/periodic/Te-pg2.html#Nuclides about middle of page..

that fooled us on the ticker forum too, a while back.

 

[joewein]

They have to keep cooling the reactors. That should account for much of the remaining processing tons.

The 250,000 figure was until the end of the fiscal year, i.e. 31 March 2012, which is another 9 months. 500 t/d (for cooling) * 270 d = 135,000 t. That's almost exactly the difference between the 250,000 t total and the 121,000 t reported in the buildings and in storage tanks at the moment.

 

[tsutsuji]

http://www.yomiuri.co.jp/science/news/20110629-OYT1T00850.htm and http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110629_02-j.pdf : The water treatment facility was stopped at 2:53 PM after an alarm signalling a leak at the site bunker building (1) rang. It had been also stopped for flushing and adsorption tower replacement between 10:45 AM and 2:13 PM. The reason why the alarm rang is under investigation.

(1) the orange box on http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110627_01-e.pdf

http://www.asahi.com/national/jiji/JJT201106290077.html : The facility was started again at 9:15 PM.

http://mainichi.jp/select/weathernews/news/20110630dde001040018000c.html A first try to start the facility had been made at 6:45 PM, but a spill occurred at the Areva facility as a result of a pump failing to start because it was set on "manual" instead of "automatic". The facility had to be stopped after 9 minutes and it took 2 hours and 20 minutes until it was started again. The spilled water did not leak outside of the building.

 

[MadderDoc]

This map of unit 4 sfp was cropped from a recently posted report, it appears to be based on knowledge I have not previously seen published. I wonder if the figures might signify something to somebody.

 

[tsutsuji]

http://www.chunichi.co.jp/s/article/2011062990203609.html : On 30 June, Tepco plans to begin transferring the accumulated water from unit 6 into the megafloat barge.

http://www.jiji.com/jc/c?g=soc_30&k=2011063000601 mentions water from unit 5 too, while saying that most of the transfer concerns ground water that seeped into unit 6's basement. The amount is 8000 tons, and the transfer will take 3 or 4 months. The radiation is 0.034 Bq/cm³ for each of the 134Cs and 137Cs contaminants, as a result of a zeolite or other purification process. The megafloat starts being used because the temporary storage tanks which had been used until now have become nearly full.

It is the first time that I hear about this "zeolite or other" purification process in the context of unit 5 and unit 6's accumulated water problem.

http://www.tepco.co.jp/en/press/corp-com/release/11062911-e.html a press release about a report to NISA concerning the amounts of contaminated water treated so far at the Kurion-Areva facility, and the processing plans until the end of September.

 

[joewein]

Assuming the diagram is aligned like a map, with North at the top, the top center would be where the gate to the reactor pit is. Does anybody know where the skimmer surge tank is located on that diagram?

I am counting 1330 fuel assemblies giving off some amount of decay heat. One set of fuel elements for units 2-5 is 548. The 10 rows of 2 columns of 3x10 assemblies on the bottom left are 600 of them.

The dark red ones must the the assemblies unloaded after the shutdown on 29 Nov 2010, since these would have decayed the least and would still be giving off most of the heat.

Some of the dark blue ones (same as pool diagram background colour) must be holding the ~200 fresh fuel assemblies that are also supposed to be in the #4 SFP, originally due to be loaded this summer when the shroud replacement was supposed to be finished.

All the blue fields in the 10 3x10 clusters down the middle add up to 200. So these might be fresh ones. That also makes sense because these fuel rods were the next ones due to be loaded into the core, so in the middle they're already aligned with the open reactor pit.

 

[joewein]

http://www.jiji.com/jc/c?g=soc_30&k=2011063000601 mentions water from unit 5 too, while saying that most of the transfer concerns ground water that seeped into unit 6's basement. The amount is 8000 tons, and the transfer will take 3 or 4 months. The radiation is 0.034 Bq/cm³ for each of the 134Cs and 137Cs contaminants, as a result of a zeolite or other purification process. The megafloat starts being used because the temporary storage tanks which had been used until now have become nearly full.

It is the first time that I hear about this "zeolite or other" purification process in the context of unit 5 and unit 6's accumulated water problem

0.034 Bq/cm³ is 34 Bq/l or a total of 68 Bq/l for all cesium. I believe the Japanese legal limit for cesium in drinking water for adults is 200 Bq/l, to put this in perspective.

 

[~kujala~]

- Assessment of the present ground water table (and thus flow speed) is probably unreliable as it is disturbed by these extractions and in a phase of adjustment (i.e. increasing flow speed), probably even if the extractions were halted after the tsunami.

As far as I understand they have so far emptied the unit #5 and #6 sub-drain pits once but have not done it for the units #1 - #4.

The total amount for #5 and #6 was 950 m3 + 373 m3 = 1,323 m3.
http://www.nisa.meti.go.jp/english/press/2011/06/en20110630-1-2.pdf
(page 12 and 13)

Also the groundwater level is probably higher near #5 and #6 because TEPCO had to divert water near #5 and #6 before crisis:

Before the crisis, streams beneath reactors No. 5 and 6 were pumped to divert water, a process that hasn't been conducted since the quake.

http://online.wsj.com/article/SB10001424052748703922504576273930625967622.html

So based on this information I would guess the situation could be quite good actually. The sub-drain water underneath #5 and #6 is low-level contaminated so even if they have more water in the sub-drain pits there it's less contaminated.

The sub-drain water underneath #1 - #4 is more heavily contaminated but there is less water there. I think they must have some kind of mechanism (automatic or manual) to observe the level of water in the sub-drain pits - and because they have not yet emptied the #1 - #4 pits it probably means that those pits are not full yet.

If one calculates that the max capacity of sub-drain pits for a single unit is somewhere near 1,000 tons (based on the 950 tons emptied from the unit #5), there would be max 4,000 tons of contaminated sub-drain water to be emptied from the units #1 - #4.

The situation gets worse if lots of contaminated water from turbine/reactor buildings has been able to go below sub-drain systems. Nobody knows if the sub-drain systems are still functioning as they are supposed to. One could also ask if the sub-drain systems are designed to hold radioactive water. Why are the cesium levels decreasing in the #1 - #4 sub-drain pits? Where has all that cesium gone?

Some clean water from the mountains or clean rainwater could dilute with the contaminated sub-drain water and make the cesium levels go down. But in the case of the #1 - #4 units I think there has been so much contamination at some point that it would be very odd to see the cesium levels to go to N.D. = not detectable?

 

[tsutsuji]

The water levels in unit 1 reactor building basement over a month are provided on

http://www.nisa.meti.go.jp/english/press/2011/06/en20110611-1-5.pdf (28 May -10 June)
http://www.nisa.meti.go.jp/english/press/2011/06/en20110629-1-4.pdf (8-28 June)

Do we have a clear idea why this level is finally stabilizing with oscillations between OP 4300 mm and OP 4600 mm ?

Is this a result of a balance between water leaking in and leaking out ?

Tepco doesn't seem to have plans to process water from unit 1 if you judge by the absence of a hose linking unit 1 to the Kurion-Areva facility on the diagram page 3 of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110627_01-e.pdf

Page 3 of http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110629e13.pdf the 80 m³ mentioned for unit 1 as "change from last report" are small in comparison with other units.

Does it mean that 100% of the 3.5 m³/h injected into unit 1 evaporate into the atmosphere or seep into the ground water ?

How can we explain the difference between unit 1 and unit 2 as regards the quantities of water accumulating in the turbine building basements, while the injected amount in the reactor is the same (3.5 m³/h now) ?

Is the leaking water from unit 1 streaming underground into unit 2's turbine building ?

 

[MadderDoc]

Assuming the diagram is aligned like a map, with North at the top, the top center would be where the gate to the reactor pit is. Does anybody know where the skimmer surge tank is located on that diagram?

Both the published videos from the pool have been shot with a camera positioned at top center of the map, so top of the map is most likely south or west. A huge cylindrical object can be seen in the second video from the pool, it's position is in the lower right corner of the map.
http://gyldengrisgaard.dk/fuku_docs/unit4_sfp_map.gif

 

[sheffters]

Does it mean that 100% of the 3.5 m³/h injected into unit 1 evaporate into the atmosphere or seep into the ground water ?

I assume so, yes. If you look at the reported reactor water levels, they change very little, if you can believe the readings. It's either in the ground or in the air.

If you look at the temps, the reactors are still easily hot enough to evaporate a decent volume of the water, and the rest just leaks out.

http://www.ianbradshaw.co.uk/multimedia/fukushima/tepco.html

I.

 

[MiceAndMen]

This map of unit 4 sfp was cropped from a recently posted report ...

Which recently posted report, please? Later on a few posts you refer to 2 videos of SFP4, do you have links for those also, please? The one with the large cylindrical object I have seen, and I thought that was from the first video we were treated to from SFP4. Was there another one previous to that?

 

[MadderDoc]

Which recently posted report, please? Later on a few posts you refer to 2 videos of SFP4, do you have links for those also, please? The one with the large cylindrical object I have seen, and I thought that was from the first video we were treated to from SFP4. Was there another one previous to that?

The map is from a DOE report which is attached to the end of this NRC testimony
(the link was posted on the Unit 3 thread recently, however perhaps not here on the big thread):

http://pbadupws.nrc.gov/docs/ML1114/ML11147A075.pdf

Yes there was a previous video, dated April 28th, It shows the area corresponding to the upper right corner of the DOE map:
http://www.tepco.co.jp/en/news/110311/images/110428_1.zip
The second video showing most of the remaining and larger part of the pool, including the cylindrical object, dated May 8th:
http://www.tepco.co.jp/en/news/110311/images/110508_2.zip

 

[joewein]

Both the published videos from the pool have been shot with a camera positioned at top center of the map, so top of the map is most likely south or west. A huge cylindrical object can be seen in the second video from the pool, it's position is in the lower right corner of the map.
http://gyldengrisgaard.dk/fuku_docs/unit4_sfp_map.gif

I agree after looking at http://www.youtube.com/watch?v=unvcryGXNv4" (110508). Since the video was probably taken using the "kirin" (giraffe), which is usually parked at the south of unit 4 for easy access to the SFP located at that end of the building, the top of the map most likely is the south side, making the bottom north. The large round object in the bottom right is then at the north west.

The items shown as circles with a cross in them, arranged in their own racks near the camera position (middle top) and near the round object in the chart look like BWR control rods on the video (at 00:32-00:37).

I had not heard of control rods being parked in SFPs, but given how much radiation they are exposed to, it is possible and maybe they are also there as a precaution against criticality. Perhaps the boron becomes saturated with neutrons and needs replacing every now and then, while the steel could become radioactive, hence the underwater storage like the old shroud.

Could the large round object be the skimmer surge tank? The only picture I've seen of its top shows it to be round.

 

[zapperzero]

I had not heard of control rods being parked in SFPs, but given how much radiation they are exposed to, it is possible and maybe they are also there as a precaution against criticality. Perhaps the boron becomes saturated with neutrons and needs replacing every now and then, while the steel could become radioactive, hence the underwater storage like the old shroud.

Those are control blades. Indeed, the boron gets depleted and the steel gets activated.

 

[zapperzero]

Could the large round object be the skimmer surge tank? The only picture I've seen of its top shows it to be round.

That should be the old shroud, I think.

 

[clancy688]

There always is the possibility that TEPCO, NISA and NSC didn't tell the whole truth and the release was significantly bigger than reported.

Hm, they revised the numbers again and at least me didn't notice...

http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/attach_04_2.pdf" of the official reports gives us 840.000 TBq (converted) for the airborne releases of Units 1-3.
But no indication as for which timeframe.

 

[etudiant]

Hm, they revised the numbers again and at least me didn't notice...

http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/attach_04_2.pdf" of the official reports gives us 840.000 TBq (converted) for the airborne releases of Units 1-3.
But no indication as for which timeframe.

They note on P3 that they calculate the total fission products released 'during the term of the analysis', which appears to be about 1 week, judging by the time lines on the charts. Presumably that covers the bulk of the emissions.

 

[SteveElbows]

That should be the old shroud, I think.

A diagram they released as part of the explanation for injecting water into reactor 4 & the storage pit, which I believe is linked to some days ago in this thread, showed a core shroud in the dryer storage pit/pool area, not in the spent fuel pool.

 

[tsutsuji]

The daily Kurion-Areva facility trouble :

http://sankei.jp.msn.com/affairs/news/110630/dst11063022440037-n1.htm (and http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110630_05-e.pdf ) : On 30 June the decontamination facility was stopped for flushing between 10:46 AM and 1:35 PM. The facility was restarted but after one hour it had to stop again because of an alarm signalling that gasses are unable to evacuate through the exhaust stack at the Areva facility.

http://www.nikkei.com/news/headline...19481E1E2E2E19A8DE1E2E2E4E0E2E3E39797E0E2E2E3 The facility started again at 6:50 PM (30 June).

The same http://www.nikkei.com/news/headline...19481E1E2E2E19A8DE1E2E2E4E0E2E3E39797E0E2E2E3 also says that the heat exchanger for unit 3's spent fuel pool has started running at 6:33 PM (30 June).

 

[SteveElbows]

Hm, they revised the numbers again and at least me didn't notice...

http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/attach_04_2.pdf" of the official reports gives us 840.000 TBq (converted) for the airborne releases of Units 1-3.
But no indication as for which timeframe.

I noticed the 840,000 TBq estimate at the time, but I don't think I noticed that it was new, I forgot that the previous adjustment was from 370,000 to 770,000 rather than straight to 840,000. Press reports certainly mention 770,000 but I can't actually work out which document had this figure in.

As for timescales, I became very interested in how these sorts of estimates were done, the estimated timing of the largest releases, and the fact that the analysis which showed emissions by each reactor had reactor 2 as the main culprit. I did not have much joy learning more about NISA estimate methodology, but I had much more success with finding detail of how the NSC did their calculations. NSC are the ones who came out with the 630,000 TBq figure in April, at a time that NISA only estimated 370,000 TBq.

The following document, which I have mentioned at least once before in this thread and which is in Japanese, seems to contain a wealth of information about how they estimate contamination, far more than we usually get. Its from an NSC meeting (meeting 31). Computer translation does not do a perfect job of revealing the details in their full glory, but give it a try and you should at least see what I mean. There are a few tables and charts there too which require almost no translation to understand. And the one on the very last page shows a timeline of release magnitude which really helps to get a sense of the picture they have established when collecting data and doing their analysis of what happened.

http://www.nsc.go.jp/anzen/shidai/genan2011/genan031/siryo4-2.pdf

 

[elektrownik]

I still don't understand why there is only 350mm in unit 4 skimmer surge tank, it was always 4500-6500mm and was changing when they were injecting water from concrede pump, but 2 days ago it started decreasing very quick to 350mm now, also they didnt change anything in pipes, look here: http://www3.nhk.or.jp/daily/english/30_03.html

But TEPCO hasn't been as successful with the No.4 reactor's spent fuel pool. A hydrogen explosion in March damaged water pipes that are connected to it. The company is reviewing its installation plan.

Workers entered the 5th floor of the No.4 reactor building on Wednesday for the first time since the explosion to see if other pipes can be used instead.

 

[SteveElbows]

I still don't understand why there is only 350mm in unit 4 skimmer surge tank, it was always 4500-6500mm and was changing when they were injecting water from concrede pump, but 2 days ago it started decreasing very quick to 350mm now, also they didnt change anything in pipes, look here: http://www3.nhk.or.jp/daily/english/30_03.html

I can think of a few possibilities.

When they used concrete pump trucks, they would go for days without pumping anything, and then pump lots over many days until they saw the skimmer surge level go back up, which is an indication that the pool has been filled to a certain high level that causes overflow to skimmer.

It is possible that now they have a different system, they are injecting water more steadily over time, at a rate that keeps the pool a t a certain level that is high enough, but not so high as to overflow into skimmer tank. Robbed of fresh supplies of water, the skimmer tank eventually reaches lows we have not seen before.

Also possible that they change that state of system that skimmer tank is part of, in a way that causes water to leave the skimmer tank at a faster rate.Unclear whether this has ever been the case at this pool or any of the other reactor pools, but we have seen skimmer levels at some other pools fall to levels that we weren't used to seeing, think this has happened at least once or twice. To put this point another way, there have been times when we see skimmer levels not really changing much at some pools for long lengths of time, and then suddenly decrease quite rapidly for a number of days. Probably easier to spot this phenomenon with a pool such as the one at reactor 1 which has been considered to be far more under control than the one at 4.

 

[elektrownik]

I can think of a few possibilities.

When they used concrete pump trucks, they would go for days without pumping anything, and then pump lots over many days until they saw the skimmer surge level go back up, which is an indication that the pool has been filled to a certain high level that causes overflow to skimmer.

It is possible that now they have a different system, they are injecting water more steadily over time, at a rate that keeps the pool a t a certain level that is high enough, but not so high as to overflow into skimmer tank. Robbed of fresh supplies of water, the skimmer tank eventually reaches lows we have not seen before.

Also possible that they change that state of system that skimmer tank is part of, in a way that causes water to leave the skimmer tank at a faster rate.Unclear whether this has ever been the case at this pool or any of the other reactor pools, but we have seen skimmer levels at some other pools fall to levels that we weren't used to seeing, think this has happened at least once or twice. To put this point another way, there have been times when we see skimmer levels not really changing much at some pools for long lengths of time, and then suddenly decrease quite rapidly for a number of days. Probably easier to spot this phenomenon with a pool such as the one at reactor 1 which has been considered to be far more under control than the one at 4.

But unit 2 skimmer surge tank is ~3000mm
there was no change in water system:

But TEPCO hasn't been as successful with the No.4 reactor's spent fuel pool. A hydrogen explosion in March damaged water pipes that are connected to it. The company is reviewing its installation plan.

and here is plot, sst water level from 6/15 to today:
[PLAIN]http://img714.imageshack.us/img714/6221/erwero.jpg

 

[SteveElbows]

there was no change in water system:

There has been a change. They could not use the system they wanted to due to pipe damage, and an even more recent survey of building reveals that a valve they want to use is covered in debris. However, this has not stopped them from starting up a different temporary solution. They posted a document about this system which we talked about in this thread, and judging from the wording of status updates they have ben using it for a while now.

eg:

http://www.tepco.co.jp/en/press/corp-com/release/11061902-e.html

From 4:05 pm to 7:23 pm on June 18, the injection of fresh water to spent fuel pool of Unit 4 was implemented using temporary water injecting system (hydrazine was also injected from 4:29 pm and completed at 6:33 pm on same day)

However it is unclear to me whether they are now reporting every time they put water in the pool using this method, if they just put it in during brief periods of time, or more continuously. I am a little bit behind reading the status updates but I don't remember hearing anything about this very recently, say within the last 5 days.

edited to add link to document showing this alternative system:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110616_03-e.pdf

 

[elektrownik]

Yes but this new water injection system is almost the same as concrede pump, so this shouldn't act on sst water level
interesting data and photos from today about unit 4:
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110630_03-e.pdf

 

[causeceleb]

Question

TEPCO just published this new data today
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110630e11.pdf

this is what i think it all amounts to:

June 29 at the Main Gate of Fukushima Daiichi
the radiation levels were

2.3 mega becquerels (counts per sec.) per cubic centimeter in the air for Iodine-131

5.0 mega becquerels (counts per sec.) per cubic centimeter in the air for Cesium-134

3.0 mega becquerels (counts per sec.) per cubic centimeter in the air for Cesium-137

is my take on this correct, are my numbers what TEPCO data says?


note, the complete document it here (appendixes at bottom of page)
http://www.tepco.co.jp/en/press/corp-com/release/11063009-e.html

 

[DSamsom]

Question

TEPCO just published this new data today
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110630e11.pdf

this is what i think it all amounts to:

June 29 at the Main Gate of Fukushima Daiichi
the radiation levels were

2.3 mega becquerels (counts per sec.) per cubic centimeter in the air for Iodine-131

5.0 mega becquerels (counts per sec.) per cubic centimeter in the air for Cesium-134

3.0 mega becquerels (counts per sec.) per cubic centimeter in the air for Cesium-137

is my take on this correct, are my numbers what TEPCO data says?


note, the complete document it here (appendixes at bottom of page)
http://www.tepco.co.jp/en/press/corp-com/release/11063009-e.html

I am not sure which document you're referring to but MegaBecquerels (10E6) can't be correct. Radioactivity in the air has been in the order of MicroBecquerels (10E-6) all the time

 

[causeceleb]

I am not sure which document you're referring to but MegaBecquerels (10E6) can't be correct. Radioactivity in the air has been in the order of MicroBecquerels (10E-6) all the time

i'm talking about this document:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110630e11.pdf

so, then, if i change all of my "megas" to "micros" does everything else look right?

 

[causeceleb]

i'm talking about this document:
http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110630e11.pdf

so, then, if i change all of my "megas" to "micros" does everything else look right?

here's the correction:

2.3 micro becquerels (counts per sec.) per cubic centimeter in the air for Iodine-131

9.5 micro becquerels (counts per sec.) per cubic centimeter in the air for Cesium-134

9.3 micro becquerels (counts per sec.) per cubic centimeter in the air for Cesium-137

 

[causeceleb]

but i still don't get it. i thought one becquerel was one disintegration;

how can i have .000003 disintegration (counts per second)

what is a 3 millionth of a disintigration?
what is a 3 millionth of a count per second?

 

[SteveElbows]

I don't know if anybody noticed, but when they were taking readings some distance away from the plant after opening reactor 2 doors, a value in one location was quite a bit higher than before. I thought this may cause them to take more readings, but no other data emerged to show any bad changes as a result of opening reactor 2 building, so I assumed there was some other explanation for this higher reading.

Anyway it seems they investigated reasons why a reading in that locations changed, and reported on their findings:

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110630e3.pdf

Reasons include someone forgetting to send the people doing the testing a detailed map, so they measured 100m away from where previous measurement had been done. And they didnt get out of the car to do reading at night, they just stuck their arm out of the window, which affected the reading quite a bit. Reason given for not getting out of car was 'to reduce the risk of animal encounters etc.'!

 

[Borek]

but i still don't get it. i thought one becquerel was one disintegration;

how can i have .000003 disintegration (counts per second)

What about one disintegration per 300000 seconds per mL?

 

[causeceleb]

here's the correction:

2.3 micro becquerels (counts per sec.) per cubic centimeter in the air for Iodine-131

9.5 micro becquerels (counts per sec.) per cubic centimeter in the air for Cesium-134

9.3 micro becquerels (counts per sec.) per cubic centimeter in the air for Cesium-137

What about one disintegration per 300000 seconds per mL?

then you are saying that TEPCO is saying that there is next to zero radioactivity (these
three isotopes) at the main gate?

 

[clancy688]

but i still don't get it. i thought one becquerel was one disintegration (1 count per sec);
how can i have .000003 of a disintegration (.000003 counts per second)?
what is a 3 millionth of a disintigration?
what is a 3 millionth of a count per second?

It is my understanding that such measurements are taken over a larger area than 1 cm³ and over a bigger timeframe than one second.

So for example you take 1 m³ air and count all disintegrations over a period of twelve hours. Afterwards you recalculate those results into easier to understand numbers, e.g. Bq/cm3.

What you finally get is more or less a disintegration probability. The probability that there'll be a disintegration in one cm³ air is 0.0003% every second.

 

[Borek]

then you are saying that TEPCO is saying that there is next to zero radioactivity (these three isotopes) at the main gate?

No, I am just explaining what the result means.

 

[clancy688]

The following document, which I have mentioned at least once before in this thread and which is in Japanese, seems to contain a wealth of information about how they estimate contamination, far more than we usually get. Its from an NSC meeting (meeting 31). Computer translation does not do a perfect job of revealing the details in their full glory, but give it a try and you should at least see what I mean. There are a few tables and charts there too which require almost no translation to understand. And the one on the very last page shows a timeline of release magnitude which really helps to get a sense of the picture they have established when collecting data and doing their analysis of what happened.

http://www.nsc.go.jp/anzen/shidai/genan2011/genan031/siryo4-2.pdf

Big thanks! The graph is interesting indeed.

There was a MAJOR C137 release going on for at least one day between March 30th and 31st. 100 TBq/h, makes 2400 TBq C137. Converted value: 96.000 TBq, over 10% of the total number. That alone would be sufficient for an INES 7 classification. What happened that day?

Or is this a mistake on my part, did I read the chart wrong?

In case it's real: Then screw my previous comments about airborne releases and the number not rising anymore - in that case, those are wrong of course.

 

[causeceleb]

No, I am just explaining what the result means.

well, i thought 9.5E-06 meant 9.5 times 10 to the minus 6, but
the whole thing just threw me for a loop.
thank you for helping me grab hold of reality :)

 

[SteveElbows]

Yes but this new water injection system is almost the same as concrede pump, so this shouldn't act on sst water level
interesting data and photos from today about unit 4:
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110630_03-e.pdf

Photos are interesting. I am pretty sure that some of the stuff seen is an off-white colour because earlier in June they sprayed the anti-scatter substance onto the roof of reactor 4. This could also be what the gunk around one of the photographed valves is, although I cannot be sure.

Good to see the gate between the fuel pool and the reactor well, good to see the reactor well full of water. I wonder if the water level will stay stable.

Do you care much now about the reported skimmer surge levels? To add to list of possibilities regarding what has changed, I suppose it is possible that gate between fuel pool & reactor well still had a leak, and now they have filled up the reactor well, water is not being lost from fuel pool so quickly, so less filling required? Anyway it seems that I was probably wrong to suggest that maybe they use the new water system on a more continuous basis, since I checked recent status reports and brief injections via this system have been reported in recent days.

Another possibility is that since completion of steel structural support under fuel pool, they feel they have more options available to them, perhaps they were avoiding certain things because of fear of structural failure. For example I don't think they started filling the reactor well & storage pit with water until the first phase of structural support work was done, but this could be a mere co-incidence of timing for all I know.

 

[Bodge]

The CTBTO monitoring is back.

I find the I-131 peaks to be indicative of ongoing fission somewhere on the site.

[PLAIN]http://www.bfs.de/de/ion/imis/ctbto_aktivitaetskonzentrationen_jod.gif
[PLAIN]http://www.bfs.de/de/ion/imis/ctbto_aktivitaetskonzentrationen_caesium.gif