Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[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

 

[SteveElbows]

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.

I don't think you are reading the chart wrong,but due to a lack of official narrative about air release events past the first week, I cannot really tell you what happened on that day, but I do intend to look into it further again sometime. It was the even higher magnitude release estimated for a time on March 15th that got most of my attention when I first found this document.

As for the number not rising significantly anymore, using computer translation of that NSC document I am fairly sure their estimated total releases covers the entire period shown in that graph, so their figure of 630,000 TBq covers the includes the end of March figure you mention. Actually this document also shows that they slightly revised upwards their calculation for total release of Caesium. Using INES conversion I think the new NSC-calculated total release for period up to 6th April was 670,000 TBq. Crucially I don't think any high magnitude releases beyond the dates covered by this report have been mentioned, so I believe your point that later daily releases don't make very much difference to the estimated total is still valid.

 

[SteveElbows]

The CTBTO monitoring is back.

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

I believe we still need to check for other factors which could cause spikes in such data. For example weather.

 

[clancy688]

I am fairly sure their estimated total releases covers the entire period shown in that graph, so their figure of 630,000 TBq covers the includes the end of March figure you mention. Actually this document also shows that they slightly revised upwards their calculation for total release of Caesium. Using INES conversion I think the new NSC-calculated total release for period up to 6th April was 670,000 TBq. Crucially I don't think any high magnitude releases beyond the dates covered by this report have been mentioned, so I believe your point that later daily releases don't make very much difference to the estimated total is still valid.

Well, there's a problem. On page 4 there's another chart showing exact values and time periods. I used it to calculate the whole C137 release (no time for I131, maybe tomorrow). Released Cesium (per hour) is (Release Rate / (1 + I/C Ratio)).
But I'm coming 2000 TBq short. NSC's estimate was a release of 12.000 TBq C137. I only get 10.000 using their numbers.
Oh, and the exact C137 release for March 30th-31st would be 1900 TBq (unconverted) or 75.000 TBq (converted).

 

[Bioengineer01]

I don't think you are reading the chart wrong,but due to a lack of official narrative about air release events past the first week, I cannot really tell you what happened on that day, but I do intend to look into it further again sometime. It was the even higher magnitude release estimated for a time on March 15th that got most of my attention when I first found this document.

As for the number not rising significantly anymore, using computer translation of that NSC document I am fairly sure their estimated total releases covers the entire period shown in that graph, so their figure of 630,000 TBq covers the includes the end of March figure you mention. Actually this document also shows that they slightly revised upwards their calculation for total release of Caesium. Using INES conversion I think the new NSC-calculated total release for period up to 6th April was 670,000 TBq. Crucially I don't think any high magnitude releases beyond the dates covered by this report have been mentioned, so I believe your point that later daily releases don't make very much difference to the estimated total is still valid.

Did you guys look at the way the releases acknowledged by TEPCO in the document you mentioned are reflected in the CTBTO charts, posted before? Is it reasonable to back extrapolate from that and take a rough guess at newer non-reported releases at later dates from the peaks in the graphs? Am I making sense?

 

[LabratSR]

I haven't seen this posted yet, sorry if it has been.

English Version of Timeline Released.

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110618e15.pdf

 

[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).

http://mainichi.jp/select/jiken/news/20110701k0000e040075000c.html the reason of the trouble was a mistake in the control of the water level in a tank. Although the water level must be set at 3% above the bottom when the facility is stopped and 30% when it is running, the facility had been started with the level still set at 3%.

http://www.nikkei.com/news/headline...19595E2E3E2E2E58DE2E3E2E5E0E2E3E39790E0E2E2E2 : from 1 July to 4 July, Tepco will be installing a new water tank whose purpose is to centralise the two water routes (the route from the filtrate tank, and the route from the water purification facility) that take water to the reactors. The new tank will have a 1000 ton capacity. On 1 July the cooling is switched back to the filtrate water tank. The new "buffer tank" is shown on the diagram at http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110701_02-j.pdf . At the same time, the PVC hoses will be changed to steel pipes.

 

[MiceAndMen]

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

Hallelujah we finally have an official TEPCO diagram for the refueling floor at unit 4. Very interesting pictures. How very strange to see the reactor well open to the sun and sky looking like a large swimming pool.

 

[joewein]

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

I find they show the exact opposite.

If fresh I-131 was produced by fission and released then one would expect levels to come back to the same levels in the first chart after every fission event, more or less. The fact that both the valleys and peaks of the iodine curves drift down in line with logarithmic decay indicates that no fresh I-131 is being produced. The ups and downs are probably mostly driven by weather conditions, such as changes in wind directions, rain, etc.

The second argument against ongoing fission is that the ratio of iodine to cesium is shifting just the way one would expect from decay. Cesium has been holding almost steady (with some random ups and downs) since later March, while iodine keeps falling (also with some ups and downs). That's precisely what one would expect in the absence of ongoing fission, given the different half lives (Cs-134: 2 y; Cs-137: 30 y; I-131: 8 d). If there were fresh releases from ongoing fission, the cesium and iodine curves would look a lot more alike than they do.

 

[joewein]

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

Hallelujah we finally have an official TEPCO diagram for the refueling floor at unit 4. Very interesting pictures. How very strange to see the reactor well open to the sun and sky looking like a large swimming pool.

I am attaching horizontal views of Fukushima 1 unit 1, looking north and looking west. Units 2-5 are somewhat different, but it should still be a useful reference.

 

[causeceleb]

how can there be no new Iodine-131 when there is
800 tons of corium laying about all over the place
at Fukushima Daiichi?