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Japan Earthquake: nuclear plants

by gmax137
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Atomfritz
#10657
Jul18-11, 05:16 PM
P: 74
Quote Quote by Joe Neubarth View Post
Tokyo govt finds iodine-131 levels up to quadruple cesium levels in water reclamation centers.
July 18th, 2011 at 07:35 AM


Measurements of radioactivity in sewage treatment, etc., Sewer Authority (Tokyo), July 15, 2011:
http://translate.google.com/translat...i/infn0533.htm
Maybe just a "spelling mistake" - the long-term iodine measurements after emissions usually regard I-129 (halftime 15 mill yrs).

Quote Quote by tsutsuji View Post
See also the diagram released by Kepko showing the accumulator that broke down at Ohi NPP : http://www.kepco.co.jp/pressre/2011/...0716_1j_01.pdf (ぼう酸水=borated water ; 窒素=nitrogen ; 弁=valve ; 蓄圧タンク= accumulator ; 水位計=water level gauge ; 圧力計=pressure gauge)
Thanks!
This makes me feel understand the differences of Xinhua and Spiegel report, both seem correct to me even if the first impression looks quite different.

Quote Quote by Gary7 View Post
Regarding the "roof", the Tepco press release for today says:

As precaution against rain for the exposed top section of the turbine building for Reactor #3, construction of a temporary roof was begun at 8:30am (July 18th).
The article Tsutsuji quoted says that only the biggest hole in T/B roof is 11x14 meters and there are others. On the satellite photos these holes seem soo small!
And that they appear to have set up some kind of harbor near units 5+6, this seems very sensible. They are really doing much much work, without any kamikaze like in Russia.

I well understand that they want to get the holes closed before the tsunami comes. Could else be like waterfall sinks.
And, the rain decontaminating the roofs so probably will just conveniently flow into the ocean. Nice!
joewein
#10658
Jul18-11, 10:06 PM
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Quote Quote by Atomfritz View Post
Maybe just a "spelling mistake" - the long-term iodine measurements after emissions usually regard I-129 (halftime 15 mill yrs).
I have never seen I-129 mentioned in Tokyo water-related data.

The numbers for levels in drinking water published by the city only listed I-131, Cs-134 and Cs-137:
http://monitoring.tokyo-eiken.go.jp/...past_data.html

Same for most seawater figures released.

With its long half life it probably doesn't contribute a lot of becquerels relative to its weight, so I don't think a mixup with it would explain those becquerel figures.


Given that I-131 levels in early April where an order of a magnitude higher than cesium levels, they should have reached parity around early May. By July 4-5 when the water sludge was measured, another 8 half lives of I-131 should have passed, so I-131 should be two orders of a magnitude below cesium.


If in this particular source they were at similar levels, one would assume chemical reasons for that, i.e. cesium didn't precipitate with the mud as much iodine did. Cesium salts should be highly soluble (similar to potassium salts) and it would never occur in elementary form outside the lab. Iodine does have insoluble salts (such as silver iodide) and in elementary form is not particularly water soluble.
tsutsuji
#10659
Jul19-11, 02:26 AM
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http://www3.nhk.or.jp/news/html/2011...286881000.html With the purpose of recovering the 50 m/hour flow rate from the decline to 37 m/hour, the water treatment facility had been shut down on the morning of 15 July to make repairs such as bleeding air and changing hoses for ones with lesser resistance, and a 39 m/hour flow rate had been achieved. However on the morning of 18 July the flow rate had dropped to 37 m/hour again. Tepco admits that it ignores the cause of the problem.

http://www3.nhk.or.jp/news/genpatsu-...25_kangae.html The expectation that the government would define more precisely today what is meant by the "cold shutdown" that should lead to a lifting of the 20 km range no-entry zone has been deceived. The definition provided by the government today remains vague, saying the RPV bottom temperature must be around 100C and human exposure to radiation must be largely curbed. This is far from a concrete definition of radioactive substances and radiation dose limits.

http://mainichi.jp/select/weathernew...40126000c.html The exposure of two workers who repaired the big hole on unit 3 turbine building roof yesterday passed 10 mSv, with a maximum of 12 mSv. Today the plan is to repair one 5 m x 2 m oval-shaped hole and a number of skylights blown up by the explosion, and to install sandbags preventing water to flow into a gutter whose down pipe is damaged.
joewein
#10660
Jul19-11, 03:53 AM
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We have discussed the video in which Arnie Gundersen spotted what looked like a single "handle" for a fuel assembly in the debris-filled unit 3 pool.

I just noticed a picture of the same pool from probably the refueling last year on this page. Look for the picture labeled "Reactor 3 refueling - mox in top left corner".



If the black items are fuel assemblies then many are quite spread out over the pool, instead of in largely complete rows as in unit 4.
Joe Neubarth
#10661
Jul19-11, 07:54 AM
P: 238
I would think that spreading them out would be a prudent thing to do. I expect that the holding racks are very secure, but a more uniform distribution of weight would just make sense.
Joe Neubarth
#10662
Jul19-11, 07:57 AM
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Quote Quote by robinson View Post
It may mean the amount of Iodine that was released was far higher than was reported.
I think many of us suspect that, simply because of the manner of revealing information that TEPCO established very early on.
tsutsuji
#10663
Jul19-11, 08:58 AM
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http://mainichi.jp/select/today/news...10100000c.html This is a report from tonight's Tepco-government joint press conference. Tepco estimated the radiation emitted from 20 June 2011 to 28 June 2011 : 1,000,000,000 Bq/hour. This is 2,000,000 times less than the estimate for 15 March 2011. It amounts to a maximum yearly exposure of 1.7 mSv on the premises of the plant. A NISA official, Mr Hiroshi Yamagata said the goal for "step 2" (january 2012) is to achieve curbing the radiological emission inside the plant below the legal limit of 1 mSv per year.

http://www.tepco.co.jp/en/press/corp...1071905-e.html Tepco publishes the progress status of the "roadmap". Items marked with red ink on http://www.tepco.co.jp/en/press/corp...s/110719e5.pdf are announcements of new tasks added on the roadmap. For comparison, here is the progress status that was published on 17 June : http://www.tepco.co.jp/en/press/corp...1061702-e.html

http://www.nikkei.com/news/headline/...E3E2E2E2E2E2E2 Before building the cover structure at units 3 and 4, the removal of debris has priority. (Judging from what is written in http://www.tepco.co.jp/en/press/corp...s/110719e5.pdf what is meant here seems to be the debris located on the top floors of reactor buildings 3 and 4)

http://www.jiji.com/jc/zc?k=201107/2011071600400 (from the 16 July Tepco press conference) The present water treatment system has 4 km long pipes and a lot of troubles. When the end of the treatment of accumulated water in turbine buildings will become clear, they will switch to another system with short pipes. Moreover, they will increase the injection rate and bring reactor water temperature well below 100C. Tepco is proceeding with the basic design of the ground water shielding wall.
Joe Neubarth
#10664
Jul19-11, 09:33 AM
P: 238
Quote Quote by joewein View Post
I have never seen I-129 mentioned in Tokyo water-related data.

The numbers for levels in drinking water published by the city only listed I-131, Cs-134 and Cs-137:
http://monitoring.tokyo-eiken.go.jp/...past_data.html

Same for most seawater figures released.

With its long half life it probably doesn't contribute a lot of becquerels relative to its weight, so I don't think a mixup with it would explain those becquerel figures.


Given that I-131 levels in early April where an order of a magnitude higher than cesium levels, they should have reached parity around early May. By July 4-5 when the water sludge was measured, another 8 half lives of I-131 should have passed, so I-131 should be two orders of a magnitude below cesium.


If in this particular source they were at similar levels, one would assume chemical reasons for that, i.e. cesium didn't precipitate with the mud as much iodine did. Cesium salts should be highly soluble (similar to potassium salts) and it would never occur in elementary form outside the lab. Iodine does have insoluble salts (such as silver iodide) and in elementary form is not particularly water soluble.
I thought that they were identifying the radioactive emitters by the energy level of the radiation detected therefrom.
tanyaeasley
#10665
Jul19-11, 09:51 AM
P: 3
Quote Quote by joewein View Post
We have discussed the video in which Arnie Gundersen spotted what looked like a single "handle" for a fuel assembly in the debris-filled unit 3 pool.

I just noticed a picture of the same pool from probably the refueling last year on this page. Look for the picture labeled "Reactor 3 refueling - mox in top left corner".



If the black items are fuel assemblies then many are quite spread out over the pool, instead of in largely complete rows as in unit 4.
According to my husband, who is in the nuclear industry and carried out a WANO inspection of a different Japanese nuke plant in December, the silvery square topped slots are the ones holding spent fuel assemblies. (Seen in upper left and upper right of photo.)
NUCENG
#10666
Jul19-11, 02:15 PM
Sci Advisor
P: 916
Quote Quote by westerly View Post
A question just popped into my mind.

Where could the oxygen for the hydrogen/oxygen reaction in unit two have come from?
If the overpressure/overtemperature of the containment caused a failure in the soppression chamber (torus) the oxygen was in the torus room. (This is my best guess).

If containment failure was at penetrations or PCV flange leakage the oxygen was in the air outside the containment. If the fuel pool was a source of hydrogen then the oxygen was in the air in the building. Once a breach occured and the containment was depressurized oxygen would be able to enter the containment. But that would probably have meant a second deflagration/detonation. The relatively smaller damage to the reactor building of unit two may mean the hydrogen burn did not propogate back into containment. (Total speculation, but possible).
NUCENG
#10667
Jul19-11, 03:06 PM
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P: 916
Quote Quote by Joe Neubarth View Post
Iodine 131 Four months after Reactor Three Blew???? One hundred and twenty some days after Reactor Three Building blew, and they are still finding I-131 ?????????

This is very frightening. As previously stated, Iodine-131 being very radioactive has a rapid half life. Every week or so half of it is gone. After 80 days it should be almost impossible to detect. Yet, here we are FOUR months after the BIG Detonation of Reactor Three and we are still seeing large amounts of Iodine 131 in water samples.

Am I wrong or should this not be happening???

Tokyo govt finds iodine-131 levels up to quadruple cesium levels in water reclamation centers.
July 18th, 2011 at 07:35 AM


Measurements of radioactivity in sewage treatment, etc., Sewer Authority (Tokyo), July 15, 2011:
http://translate.google.com/translat...i/infn0533.htm
It appears that you are seeing the results of a separation process that is skewing the results. The Iodine is soluble and is in the "sludge dewatering" which is the water remaining after the sludge is removed. Most of the Cs is in the sludge which has been separated. Since it isn't clear how much sludge is in how much water, I'm not sure how to interpret the relative magnitudes of the isotopes. If we had volumetric or mass concentrations of sludge and water it would make a calculation possible.

They say the dose rate readings were measured at 1 meter, but is it one meter from what?
NUCENG
#10668
Jul19-11, 03:18 PM
Sci Advisor
P: 916
Quote Quote by tanyaeasley View Post
According to my husband, who is in the nuclear industry and carried out a WANO inspection of a different Japanese nuke plant in December, the silvery square topped slots are the ones holding spent fuel assemblies. (Seen in upper left and upper right of photo.)
I believe you are seeing new non MOX-fuel in the upper right and new MOX fuel in the upper left. Spent fuel is darkened by thin layers of oxide and that explains the difference of the fuel distributed in the racks. Discharged fuel after five or six years isn't as bright and shiny as new.

Replacement batch sizes are generally a quarter to a third of the bundles and thae number of new MOX and non-MOX assemblies is a good chunk of the expected reload batch size.

32 MOX
64 Non MOX
96 total bundles

Unit 3 has 548 bundles in a full core.
benzyme
#10669
Jul19-11, 07:53 PM
P: 5
I read a quote from one of the farmers with contaminated hay, who said that because of the distance (150 km) and wind direction after the hydrogen explosions, he didn't think there was any risk. I was just wondering what some of you would reply to him? Would most of that contamination have been from unit 1 explosion (I think wind blew n/nw) or just steady accumulation over a few weeks/months?
joewein
#10670
Jul19-11, 08:29 PM
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P: 192
Quote Quote by Joe Neubarth View Post
I thought that they were identifying the radioactive emitters by the energy level of the radiation detected therefrom.
Yes, they are. They are not likely to confuse I-131 with I-129 from that. It almost certainly really is I-131, but for reasons discussed above the cesium got separated somewhere along the sludge and water processing path in the sewage treatment plant.

The ratio detected is unlikely to be a directly linked to nuclear decay of the respective isotopes. Somebody cherry-picked the data pointing out that in Minamitama Water Reclamation Center the I-131 was 4 times the Cs-134 level (66 vs 15 Bq/kg). At two sites I-131 was below detection level while cesium was > 100 Bq/kg. The ratios are all over the place, but "iodine at 4 times cesium levels in July" gets more attention than vice versa.
joewein
#10671
Jul19-11, 10:02 PM
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P: 192
Quote Quote by benzyme View Post
I read a quote from one of the farmers with contaminated hay, who said that because of the distance (150 km) and wind direction after the hydrogen explosions, he didn't think there was any risk. I was just wondering what some of you would reply to him? Would most of that contamination have been from unit 1 explosion (I think wind blew n/nw) or just steady accumulation over a few weeks/months?
There were two major plumes over land, from what I recall from documentaries I've seen.

The first one was travelling South over Ibaraki down to Chiba, then sweeping over the Kanto plain, touching as far south-west as Kanagawa and Shizuoka, and west into Tochigi and eastern parts of Gunma. This was the first spike registered in Tokyo. I think that was after the unit 1 venting and explosion. That's why tea in Shizuoka and Kangawa has been reaching levels beyond legal limits for food and why drinking water levels for babies and infants were briefly exceeded in Tokyo. This plume reached areas about 300 km from the plant.

The second plume headed mostly Northwest towards Fukushima City and dumping most of its contents within about 50 km, between Iitate and the plant itself, but somewhat lower concentrations reached areas to the West like Koriyama and Fukushima city further North West. The second plume coincided with the suppression chamber explosion in unit 2 and the hydrogen blast in unit 3. The most severely contaminated areas were hit by this one.

Almost certainly the bulk of the radioactive release happened during the first two weeks, especially during the containment venting operations and hydrogen explosions and before seawater injections brought temperatures down again.

The fallout pattern depends far less on proximity than on rain and snow fall on the particular day, as the precipitation extracts the radioactive load and deposits it on the ground. This was already the experience after the Chernobyl disaster: Contamination did not decrease linearly with distance, but you were truly unfortunate to see rain during those days. There is a lot of dairy farming in the picturesque alpine region of Allgu, to the South West of Munich, Germany (1300 km from Chernobyl), but the government had to dispose of the milk there, because they ended up with a lot more I-131 than areas closer to the East that didn't have rain in late April 1986.
joewein
#10672
Jul19-11, 11:57 PM
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P: 192
どうもありがとう for posting, as always!
Quote Quote by tsutsuji View Post
http://mainichi.jp/select/today/news...10100000c.html This is a report from tonight's Tepco-government joint press conference. Tepco estimated the radiation emitted from 20 June 2011 to 28 June 2011 : 1,000,000,000 Bq/hour. This is 2,000,000 times less than the estimate for 15 March 2011. It amounts to a maximum yearly exposure of 1.7 mSv on the premises of the plant. A NISA official, Mr Hiroshi Yamagata said the goal for "step 2" (january 2012) is to achieve curbing the radiological emission inside the plant below the legal limit of 1 mSv per year.
This way of converting the ongoing hourly release into an annual dose doesn't make any sense to me. It's like saying, if you borrow x amount of money every month, you will pay y amount of interest every year, as if it didn't matter how much you were already in debt or how many years you continued this.

Release or no release, there are already radioactive substances on the ground that produces background radiation, year after year. Maybe the rain will gradually wash out some of it and Cs-134 will decay with a half life of 2 years, but it won't go away quickly like the I-131.

A goal of 1 mSv/y (presumably on top of natural sources, not including them) seems very ambitious even outside the wrecked reactor building, let alone inside them.

EDIT: TEPCO regularly measures radiation at about 10 points mostly along the periphery of the plant. The official radiation readings published today (7/20) range from about 10 microsievert per hour at MP1 to 350 microsievert per hour south of the main building, near where the webcam stands. That's an annualized dose of 87 mSv to 3 Sv per year.



Sure, you can get that down to 1 mSv per year, by not staying at the plant for more than a couple of hours a year...

EDIT 2: With this helpful Survey map of Fukushima Daiichi Nuclear Power Station you can avoid hotspots of several 100 mSv/h around the reactor blocks, staying in zones with "only" 0.2-10 mSv/h.

Quote Quote by tsutsuji View Post
http://www.nikkei.com/news/headline/...E3E2E2E2E2E2E2 Before building the cover structure at units 3 and 4, the removal of debris has priority. (Judging from what is written in http://www.tepco.co.jp/en/press/corp...s/110719e5.pdf what is meant here seems to be the debris located on the top floors of reactor buildings 3 and 4)
I think this will have to include partly demolishing reinforced concrete portions of both unit 3 and 4 that are in danger of collapsing, which would destroy the polyester tent. Given the significant radiation levels at least in the unit 3 pool, I think its 5F/CRF area will need remote operated machinery for cleanup. Unit 3 should be the most challenging of the units for cover construction.
tsutsuji
#10673
Jul20-11, 03:58 AM
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Quote Quote by joewein View Post

A goal of 1 mSv/y (presumably on top of natural sources, not including them) seems very ambitious even outside the wrecked reactor building, let alone inside them.
Sorry, I made a mistake. The measured 1.7 mSv and the 1 mSv goal mentioned in the Mainichi article apply to the site boundary, not to inside the site.

Excluding the effect of already released radioactive materials, evaluation of exposure doses at the site boundary using the current release rate (approximately one billion Bq/hour) showed that the maximum exposure dose is 1.7 mSv/year.
http://www.tepco.co.jp/en/press/corp...s/110719e6.pdf
http://mainichi.jp/select/opinion/cl...40043000c.html The present US-French-Japan water treatment system is a desperate effort with a durability of one year. Although repairing the containment vessel is indispensable, Tepco removed it from the schedule, because preventing accumulated water from overflowing has priority. The water treatment system is the plant's "safety net". Tepco added the study of the full-fledged water treatment system in "step 2" of the roadmap. At present this full fledged system is a clean slate. The person in charge at Tepco said it must be based on simple design with short pipes. Large sections of the 4 km pipes at the present water treatment system don't pass the country's earthquake safety standards. Pr. Koji Okamoto of Tokyo university said it is possible to achieve cold shut-down ahead of schedule, if the closed loop cooling system proceeds smoothly. The next system should be based on learning the lessons from the present system and combining Japanese technology with few troubles.

http://mainichi.jp/select/jiken/news...40105000c.html The removal of fuel from pools will not start sooner than 3 years from now. The removal of fuel from reactors, not before 10 years from now. At Three Mile Island it took 10 years to remove the fuel from only one reactor. In comparison, Fukushima Daiichi has 3 accidented reactors, collapsed reactor buildings, serious reactor damage and radiological pollution. There are 1496 fuel assemblies in reactors and 3108 in pools, among which 2724 are spent fuel. Because there are few damages to the fuel assemblies in the pools, moving them to the common fuel pool is being considered. In normal time fuel is reprocessed at Rokkasho, Aomori prefecture, but the damaged fuel cannot be removed with usual equipment. Remote-controlled equipments to cut and transport melted fuel are necessary. Minister Goshi Hosono said the final disposal site must be located outside Fukushima prefecture. The Nuclear Safety Commission is forming an expert committee to study those questions. As it is difficult to do this with Japanese technology alone, cooperation from abroad is indispensable.

http://sankei.jp.msn.com/affairs/new...3030016-n1.htm At 5 AM, 20 July, unit 1 RPV bottom temperature passed below 100C, with 98.9 C. However the accuracy of the temperature measurement is questioned.

http://headlines.yahoo.co.jp/videone...00058-jnn-soci A new video acquired by JNN, showing the tanks storing the low-contaminated water from units 5 and 6, and a site being prepared to store the highly radioactive debris. The storing must go on as long as ground water seeps into units 5 and 6.
joewein
#10674
Jul20-11, 05:10 AM
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Quote Quote by tsutsuji View Post
Sorry, I made a mistake. The measured 1.7 mSv and the 1 mSv goal mentioned in the Mainichi article apply to the site boundary, not to inside the site.
Thanks for the correction, tsutsuji.

Again, checking the TEPCO map of the monitoring posts against Google Maps, it seems MP1-MP8 are all at most 150 m from the site boundary. For scale on this map, it's about 1200 m from the north side of the breakwaters to the south side, or about 3600 m from the northern tip of the plant site to the southern tip.

About 100 / 120 microsieverts / hour at MP-7 / MP-8 some 150 m inside the fence is 1700 / 2000 times the level we have in Tokyo right now (0.058 microsieverts / hour). That's 870-1000 mSv per year. I find it hard to believe it should be 1.7 mSv just the other side of the fence. The wind that contaminated MP-7 and MP-8 would not have cared too much about that fence...


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