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).