Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[tsutsuji]

[The NISA] is asking TEPCO to secure new storage sites to which the contaminated water can be quickly transferred,
http://www3.nhk.or.jp/daily/english/01_24.html

The water levels as of May 31st 7 AM JST reported on http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110531_01-j.pdf (as of May 19th 7 AM JST http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110519_03-j.pdf ) are :

unit 2 trench : OP + 3606 mm (OP + 3240 mm : May 19th 7 AM)
unit 3 trench : OP + 3706 mm (OP + 3360 mm : May 19th 7 AM)

unit 2 : (3606-3240)/(31-19)=30.5 mm/day
unit 3 : (3706-3360)/(31-19)=28.8 mm/day

The ground level near the pits is OP + 4000 mm : http://www.tepco.co.jp/nu/fukushima-np/f1/images/f1-sv-20110323-j.pdf

So how many days are left until this level is reached ?

unit 2 : (4000-3606)/30.5=12.9 days ~ June 13th
unit 3 : (4000-3706)/28.8=10.2 days ~ June 10th

It was reported that work was undergone to fill the pits with concrete, but is it enough ?

Accumulated water maps have been released : http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110530_04-e.pdf

Water level in the basement of unit 1 reactor building has decreased by 6 mm between May 31st 5 PM and June 1st 7 AM, making people wonder where that water has gone : http://www3.nhk.or.jp/news/html/20110601/t10013249251000.html

 

[Rive]

Any idea of what this could indicate, ads this is not the first time?

IMO the main feedwater line is broken and the core has no cooling now.

Maybe it's possible to calculate a raw core weight by the temperature rising rate and the calculated decay heat. At least if the result has no sense we will know that there is something else happening inside.

 

[elektrownik]

What ? Unit 6 reactor building is floded ? How ?? I understand turbine building from tsunami, but reactor building ?
And 2m of water in unit 6 turbine building... But how, unit 5 turbine building is not so floaded like 6...



http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110531e19.pdf <- radiation data from unit 4 and 2 sfp

 

[tsutsuji]

What ? Unit 6 reactor building is floded ? How ?? I understand turbine building from tsunami, but reactor building ?
And 2m of water in unit 6 turbine building... But how, unit 5 turbine building is not so floaded like 6...

Yes, this is surprising. See also the discussion we had a few days ago :

Unit #6 is leaking also:

http://www.nisa.meti.go.jp/english/files/en20110519-1-2.pdf

Explanation #1: RPV is leaking.
Explanation #2: SFP is leaking.
Explanation #3: Waterproof systems are not working and groundwater is leaking into the reactor building.

The greatest danger lies in the explanation #3. If it's happening in the unit #6 it can also happen in the units #1 - #5. It water can come in it can also go out.

What about #4 : Unit 6 hit and flooded by a tsunami ?

The water levels have been rising in (5 and) 6.

The company says water levels are also rising in the Number 5 and 6 turbine buildings.

http://www3.nhk.or.jp/daily/english/21_03.html

 

[~kujala~]

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110531e19.pdf <- radiation data from unit 4 and 2 sfp

Thanks, it seems that they have again made corrections. This time to unit #4 and #2 SFP samples taken on April 12th and 16th. I am going here through #4 SFP values:

The original values were (April 12th):
I-131: 220 Bq/cm3 -> 220 000 Bq/l
Cs-134: 88 Bq/cm3 -> 88 000 Bq/l
cs-137: 93 Bq/cm3 -> 93 000 Bq/l

The corrected values are:
I-131: 130 000 Bq/l
Cs-134: 130 000 Bq/l
Cs-137: 140 000 Bq/l

The comparison of all samples taken in Bq/l:
Isotope: April 12th - April 29th - May 7th
I-131: 130 000 - 27 000 - 16 000
Cs-134: 130 000 - 49 000 - 56 000
Cs-137: 140 000 - 55 000 - 67 000

The values for Cs-134 and Cs-137 on May 7th are now 43 % and 48 % from the maximum values. I am eagerly waiting for them to take new samples from unit #4 SFP and also sample the unit #1 SFP.

 

[AntonL]

What ? Unit 6 reactor building is floded ? How ?? I understand turbine building from tsunami, but reactor building ?
And 2m of water in unit 6 turbine building... But how, unit 5 turbine building is not so floaded like 6...

If you followed the accodent very closely you might have remembered that when unit 6 basement water was discovered for the first time that TEPCO attributed this to groundwater penetrating the building.

 

[Jorge Stolfi]

I have updated again my plots of reactor parameters Fukushima Daiichi units #1--#3:
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html

As I mentioned last time, I have added many data points from these TEPCo documents,
titled "Parameters for water and pressure Fukushima Daiichi Unit 1 (revised)":
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_1u.pdf
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_2u.pdf
http://www.tepco.co.jp/nu/fukushima-np/f1/images/syusei_level_pr_data_3u.pdf

Today's version corrects several data errors (mine and TEPCo's), fixes a few broken links in the HTML pages, and adds a few more data. It now includes data from all NISA press releases "プラント関連パラメータ" ("Plant-Related Parameters") except for 129 to 134 (may 8 to 11), coming soon.

Besides the isolated errors above and the erratic behavior of several instruments, there are some disconcerting details in this data. For one thing, the absolute RPV pressures in unit #3, both the "A" and "B" readings, have been negative for a few days already. (The "A" reading is reported as minus 0.136 MPa relative to atmospheric pressure of about 0.101 MPa). So if you need to suck up a perfect vacuum, talk to TEPCo.

Moreover, there is no sign of the recalibration of the water level indicators of unit #1, that TEPCo has annouced a week or two ago. That recalibration supposedly showed that the water level was actually below minus 4.5 meters; but the NISA releases still give the incorrect number (minus 1.7 meters for #1).

On the other hand, one interesting thing that shows up in the new data is a spike in the unit #3 RPV pressure, just past midnight of apr/21. According to that data, in a few hours the pressure shoot up from 0.2 MPa (abs) to 11.6 MPa (abs) -- over the RPV's maximum design pressure -- then fell to nearly zero (abs; actually minus 0.500 MPa gauge, which should be minus 0.401 MPa absolute!), then recovered to about 0.150 MPa (abs), all in a few hours. The "black smoke" from unit #3 started soon thereafter. This jolt was missing from my previous plots because the data in the NISA releases happened to be measured before the up-spike (apr/20 16:00 = 0.254 MPa), halfway between the up- and down-spikes (apr/21 04:00 = 0.303 MPa) and after the down-spike (apr/21 12:15 = 0.142 MPa).

 

[AntonL]

High levels of strontium detected at Fukushima

http://www3.nhk.or.jp/daily/english/01_h01.html]Tokyo[/PLAIN] Electric Power Company says it took soil samples on May 9th at 3 locations about 500 meters from the No.1 and No.2 reactors and analyzed them.

The utility detected up to 480 becquerels of radioactive strontium 90 per kilogram of soil. That's about 100 times higher than the maximum reading recorded in Fukushima Prefecture following atmospheric nuclear tests carried out by foreign countries during the Cold War era.

TEPCO reported detecting 2,800 becquerels of strontium 89 per kilogram of soil at the same location.

 

[elektrownik]

If you followed the accodent very closely you might have remembered that when unit 6 basement water was discovered for the first time that TEPCO attributed this to groundwater penetrating the building.

This is TEPCO BS on 99%, because:
Unit 1,2,3 are floding by water which is injected to cool down cores
Unit 1,2,3 water level and % of floded reactor building parts is not so big like in unit 6
Unit 5 which is not far from unit 6 is not so heavy flooded
How so much ground water can enter reactor building which should be sealed ?
How any system of unit 6 can work if reactor and turbine building are flooded ?

 

[elektrownik]

Moreover, there is no sign of the recalibration of the water level indicators of unit #1, that TEPCo has annouced a week or two ago. That recalibration supposedly showed that the water level was actually below minus 4.5 meters; but the NISA releases still give the incorrect number (minus 1.7 meters for #1).

It is there, under the A sensor column in table you can see "DS" (Down scale) and this mean -5m or more from top of fuel

 

[jlduh]

What ? Unit 6 reactor building is floded ? How ?? I understand turbine building from tsunami, but reactor building ?
And 2m of water in unit 6 turbine building... But how, unit 5 turbine building is not so floaded like 6...



http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110531e19.pdf <- radiation data from unit 4 and 2 sfp

You are very right, this is amazing...

Until now we heard that Tepco was pumping some water out of TURBINE building of N°5 and 6, an operation that whas explained to be already conducted as routine before the tsunami but stopped because of the tsunami, and then started again. We concluded that these T/B must haven been under groundwater and that they were obliged to pump to keep them dry, and that maybe this has to be increased because of groundwater increased level due to tsunami (this was an hypothesis). So normally, nothing really bad...

But on this map, it appears that there is water also in basements of reactors buildings N°5 and N°6, in areas that are important for safety because that's were a lot of the alternate cooling systems are! (I remember that N°5 and N°6 were stopped for maintenance if not wrong... fortunately! otherwise they couldn't probably maintain this cooling over time switching between SFP and reactor...)

This is typically some "Tepco language": if you look at Units 1 to 6, the documents indicate each and every time T/B which is Turbine Building, but they show maps for T/B AND R/B.


Then when they indicate that there is "100m3 total in T/B" for N°5 and "4000m3 in T/B" for N°6, what do we have to understand?

Until now we understood something very stupid: "4000m3 in T/B" was meaning for us, stupid guys with no Tepco language knowledge, that this water was in... Turbine Building of course! But in fact, where is it? It shows R/B and T/B, but with this title: "Accumulated water map in Unit X T/B"!

Let's play dices to decide what to interpret...

The big question is really to know how this water got there, in an area that is CRITICAL for safety control of the reactors :

A) If this water comes from the tsunami, this is very scary, because this means that there could have been a problem with cooling system failure even without power black out, due to flooded equipement in R/B.

B) If this water doesn't come from tsunami, then where does it come from? From underground water? This is scary again with safety equipements here. From reactor leaking??? Was it damaged during earthquake as a matter of fact?

Is it related to what we mentionned some weeks ago already in the parameters for Unit 5 and 6, where the water levels are always varying in the core?

Personnaly i still think this can be explained by the alternate system for cooling which if i understand well has to be switched between two things, SFP and reactor (correct me if wrong), creating this pattern with teeth in Temps, and also possibly explaining water level variation by more or less evaporation inside the core. But maybe this intrusion of water in R/B is an explanation why some cooling systems are not fully operational?

Again, this raises a lot of questions and mysteries. This is not what i would call a "normal" cold shutdown.

This brings also the questions of general safety, even "beyond design basis" which is the nice way engineers use to describe mess they didn't anticipate... We were talking about placing some critical equipement at a suffcient height to avoid flooding, but what about these electrical systems that are it seems now in R/B rooms with substantial level of water in them (and they pumped already good volumes!). What are they going to do to change the design to avoid flooding possibilities of these areas?

I've found surprising, to say the least, one image released by Tepco some weeks ago, showing many many tanks to store the "basement" water close to N°5 and N°6: huuuuhhh, so many tanks? If i find it I'll post it...

I think there is a new mystery in this Daichi plant, with these N°5 and N°6 reactors, where I suspect there is more than assumed. AGAIN.

 

[elektrownik]

This is not possible ground water can't flood Reactor building so quick look on unit 1,2,3 thay are flooded but not so much, but this flooding is due water which is injected to cores not from ground water, reactor building should be sealed, this is REACTOR building not swimming pool, ground water could leak to building but not in this amount or maybe earthquake create cracks in reactor 6 building ? this could increase flooding speed

Interesting page 9 is for upper part, not torus part, which also should be flooded, it should be 4000m3 in R/B not T/B, and T/B is 9500m3 so there is 13500m3 of water in T/B and R/B for unit 6
And unit 5 T/B and R/B is only 300m3 ?!
13500/300=45 times more water in unit 6 than in unit 5...
15200m3 for unit 4 T/B and R/B

Wait there is something wrong, unit 4 T/B is 100% flooded with 1m of water and they say that it is 9600m3, unit 2 is flooded only in 3 places with 1,2m and 13000m3 ?

 

[Gary7]

Bloomberg is reporting radiation of 5 million becquerels of Cesium 137 per square meter 25 kilometers away from the Fukushima Plant. 5 million per square meter... hmmm. I think somebody got some zeroes mixed up.

From Bloomberg:
Soil samples showed one site with radiation from Cesium-137 exceeding 5 million becquerels per square meter about 25 kilometers to the northwest of the Fukushima plant, according to Kawata’s study.

http://www.bloomberg.com/news/2011-05-30/japan-risks-chernobyl-like-dead-zone-as-fukushima-soil-radiation-soars.html

 

[clancy688]

I don't think so. During the course of the accident, there were several reports of Cs137 ground contamination in the magnitude of 10^6.

 

[SteveElbows]

IMO the main feedwater line is broken and the core has no cooling now.

Maybe it's possible to calculate a raw core weight by the temperature rising rate and the calculated decay heat. At least if the result has no sense we will know that there is something else happening inside.

If that were the case then how do you explain their ability to bring the last large leap in temperatures under control during may? Especially as they did this by switching from fire extinguisher line to feedwater line, and pumping at a higher rate using both lines for a while.

In any case the recent increases in temperature have not been so dramatic and consistent across many sensors, and TEPCO are still gradually reducing the flow rate through the feedwater line (now down to 11.5 m3/h from a peak of 13.5m3/h).

So at this point although I think reactor 3 temperatures should be kept a close eye on, and further things may well happen, I don't see a big story here yet. Especially as RPV bellows seal temperature has spiked to a high value in the past without other temperatures following.

 

[jlduh]

Bloomberg is reporting radiation of 5 million becquerels of Cesium 137 per square meter 25 kilometers away from the Fukushima Plant. 5 million per square meter... hmmm. I think somebody got some zeroes mixed up.

From Bloomberg:
Soil samples showed one site with radiation from Cesium-137 exceeding 5 million becquerels per square meter about 25 kilometers to the northwest of the Fukushima plant, according to Kawata’s study.

http://www.bloomberg.com/news/2011-05-30/japan-risks-chernobyl-like-dead-zone-as-fukushima-soil-radiation-soars.html

Hummm, returning there within 3 years from now, when we see how the situation at the plant is "stabilized" right now, this is interesting dream...

Love also the "nature park" around Tchernobyl. Words are great and cheap.

 

[~kujala~]

reactor building should be sealed, this is REACTOR building not swimming pool, ground water could leak to building but not in this amount or maybe earthquake create cracks in reactor 6 building ? this could increase flooding speed

Waterproof systems are not bullet-proof, in fact they are quite fragile and can become damaged even by aging.
The concrete itself is not water-proof but it slows significantly the flow of water.
Waterproof systems are usually build inside the buildings, so you have first the layer of concrete and then on top of it is the actual waterproof system.
An earthquake can easily damage the waterproof systems, they can even be damaged completely without the earthquake, just by "becoming old".
But is it possible that the earthquake could also have made a crack in the concrete? Then you could have a big leak, because water could go right through the concrete + the waterproof system. There would be nothing between.
What I am foreseeing, the concrete is still okay but the waterproof systems have failed. In this case there is a flow of water from inside/out or outside/in but the concrete will slow down the flow of water. For how much, I don't know.

To me the unit #6 seems to act like there is a flow of water outside in. Groundwater level is high and when they pump water out, new water is coming in. If this would be true, this would basically continue as long as the groundwater levels start decreasing. There is already tsunami waters and now they have new rain...

 

[jlduh]

So at this point although I think reactor 3 temperatures should be kept a close eye on, and further things may well happen, I don't see a big story here yet. Especially as RPV bellows seal temperature has spiked to a high value in the past without other temperatures following.

Humm, personnaly i see some visual global correlation between temps on this graphic, don't you?

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11053106_temp_data_3u-e.pdf

The last large increase in temps was i think stopped when they injected boron (or MORE boron?) in N°3, at least it has been discussed about that here.

Is it possible that, assuming some local re-criticalities, the level of boron could explain these varitions of temps and heat? Is boron consumpted, or maybe diluted by rainwater?

This is just an hypothesis to try to understand the specific pattern of this N°3 reactor concerning temps.

 

[Gary7]

It just strikes me as odd since the opening paragraph talks about 1.48 million becquerels, and then the article almost casually tosses in the 5 million becquerels 25 kms away from the plant. I couldn't find anything in Japanese that mentions this reading. I sent the reporters a query to see if the numbers were accurate. Will see what they have to say.

Now back to your regular programming.

 

[clancy688]

It just strikes me as odd since the opening paragraph talks about 1.48 million becquerels, and then the article almost casually tosses in the 5 million becquerels 25 kms away from the plant. I couldn't find anything in Japanese that mentions this reading. I sent the reporters a query to see if the numbers were accurate. Will see what they have to say.

http://www.irsn.fr/FR/Actualites_pr...valuation_Dosimetrique_Fukushima_16052011.pdf

Page 13 and following.

Up to 30 million Bq/m².Edit: I nearly got an heart attack when I saw that Borek replied to the thread - I suddenly realized that contamination hasn't anything to with technical issues and thus fits better to the contamination & consequences thread... ^^;
So I feared I'd get a rebuke again. Luckily I got spared this time. But it's still better to outsource these topics into the contamination thread.

 

[Borek]

Love also the "nature park" around Tchernobyl. Words are great and cheap.

If you stick to facts, this is one of the best places for animals in Europe:

http://www.nsrl.ttu.edu/chornobyl/wildlifepreserve.htm

See also:

http://news.bbc.co.uk/2/hi/europe/4923342.stm

 

[MiceAndMen]

IAEA loses all credibility today.

Japan’s response to the nuclear accident has been exemplary, particularly illustrated by the dedicated, determined and expert staff working under exceptional circumstances.

http://www.bloomberg.com/news/2011-06-01/iaea-says-japan-underestimated-risk-to-nuclear-plants-from-tsunami-quakes.html

When the IAEA team arrived at Fukushima last week, I had no doubt at all that they would give their blessing to the ongoing recovery work there. It is a difficult task and some credit is in order.

But I had no idea they would rubber-stamp their approval of simply everything TEPCO and the Japanese nuclear regulators have done to date. So I guess now we can look forward to the pictures of Mike Weightman posing on the megafloat later in the week.

It's mind-boggling that they have virtually no criticism whatsoever to level at the way the situation has been handled thus far.

 

[Bodge]

The NRC, IRSN, Greenpeace and the IAEA have all reported readings ~5,000,000 Beq/m2.

I first noticed this on 24th March: see https://www.physicsforums.com/showpost.php?p=3207934&postcount=1075"

At the beginning of May, the NRC released this:

also see:
http://maps.google.com/maps/ms?ie=U...581055&spn=0.761327,1.647949&z=9&source=embed

 

[elektrownik]

IAEA loses all...

In this case I don't want to know what wouldn't be "exemplary"

 

[yakiniku]

If you stick to facts, this is one of the best places for animals in Europe:

Any place left alone by humans is probably good for animals. It doesn't mean that the animals are unaffected by the contamination at Chernobyl:

http://www.publications.parliament.uk/pa/cm200910/cmselect/cmenergy/memo/nps/uc7402.htm

Animal studies in areas near the Chernobyl accident show increased levels of chromosome abnormalities and foetal deaths even after 22 generations. This has been attributed to transgenerational genomic instability effects.

 

[SteveElbows]

Humm, personnaly i see some visual global correlation between temps on this graphic, don't you?

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11053106_temp_data_3u-e.pdf

The last large increase in temps was i think stopped when they injected boron (or MORE boron?) in N°3, at least it has been discussed about that here.

Yes, many of the temps correlate, I was just pointing out that 'RPV Bellows air' had a big spike in temperature in April, during which time most other temps did not rise dramatically, so I do not like to pay attention to this temperature on its own.

Certainly I would not dream of describing the temperature situation at reactor 3 as stable, and there have been some signs of increasing temperatures in recent days. But its not clear that these will keep on climbing, so its too early for me to declare that temperatures at 3 are going crazy again. But I think its safe to say that these temperatures are not as low as TEPCO would like, and the pattern at reactor 3 is quite different to reactors 1 & 2.

As for the explanation for these events, I am just not sure. As I've said previously, injection of boron was done at same time as they were rapidly increasing water flow rates, so I find it hard to judge what was responsible for getting the temperatures somewhat under control in may.

 

[MiceAndMen]

In this case I don't want to know what wouldn't be "exemplary"

Exemplary conduct would have started with being honest about the data they had from day 1, and a good followup would have been a "roadmap" plan not rooted in fantasy. Look at the IAEA's mission statement: http://www.iaea.org/About/mission.html

develops nuclear safety standards and, based on these standards, promotes the achievement and maintenance of high levels of safety in applications of nuclear energy, as well as the protection of human health and the environment against ionizing radiation;

With their statements in the Bloomberg article cited earlier, they are promoting imaginary achievements in Japan. I'll leave the rest for the other thread.

 

[jlduh]

If you stick to facts, this is one of the best places for animals in Europe:

http://www.nsrl.ttu.edu/chornobyl/wildlifepreserve.htm

See also:

http://news.bbc.co.uk/2/hi/europe/4923342.stm

I you stick to facts Borek, many animals live much better where there is no human

So in a sense, we could call nature park every place where human had to leave because of industrial mess for example, but this can become a kind of novlang, don't you think? Don't want to argue on this subject on this thread, but as you answered me, let say that I'm just a little bored of greenswashing speak to wash dirty stuff. You know that words are describing more than facts very often (this was an article in a newspaper). That's why they are so powerful...

 

[zapperzero]

Here we are again, discussing politics. Nature of the animal, it seems. To all those who commented on the IAEA report: for my sins, I am quite familiar with the kind of language used. Here's my analysis, feel free to discuss:

https://www.physicsforums.com/showpost.php?p=3332836&postcount=219

EDIT: also see the post above...

 

[Jorge Stolfi]

Yes, many of the temps correlate, I was just pointing out that 'RPV Bellows air' had a big spike in temperature in April, during which time most other temps did not rise dramatically, so I do not like to pay attention to this temperature on its own.

How could the temperature near the top of the drywell be highter than the temperatures measured on the RPV? Two hypotheses that I can think of:

* There is a leak from the drywel near that place, say through the diaphragm/bellows into the refueling space above, or through a broken pipe into the gap between drywell and concrete. As the hot hydrogen-rich steam comes in contact with the air, the hydrogen burns (with an invisible flame) heating up the drywell wall.

* The temperature inside the RPV is actually much higher than what the RPV sensors show, as the RPV wall is being cooled from the outside by water leaking from the injection pipes. But there is a relatively small leak near the top that blows hot steam from inside the RPV into the top region of the drywell, heating it locally.

Of course you can explain anything with the magic words "instrument malfunction". But it is hard to see how a thermocouple could give a reading just a few tens of degrees higher than the correct value. I would expect it to either drop to zero volts (if the wires are severed) or give a lower-than-correct voltage (if the insulation of the wires is compromised).

 

[NUCENG]

Here we are again, discussing politics. Nature of the animal, it seems. To all those who commented on the IAEA report: for my sins, I am quite familiar with the kind of language used. Here's my analysis, feel free to discuss:

https://www.physicsforums.com/showpost.php?p=3332836&postcount=219

EDIT: also see the post above...

Maybe it wasn't all a rosy picture.

http://www.google.com/hostednews/afp/article/ALeqM5iuTRMDEJRz--IfEm_cg_iFlvNQGg?docId=CNG.9e4977e7a1dedbfd01785d2d4b7cb668.791

Here is the summary report:

http://www.nisa.meti.go.jp/english/files/en20110601-1.pdf

 

[biggerten]

How could the temperature near the top of the drywell be highter than the temperatures measured on the RPV? Two hypotheses that I can think of:

* There is a leak from the drywel near that place, say through the diaphragm/bellows into the refueling space above, or through a broken pipe into the gap between drywell and concrete. As the hot hydrogen-rich steam comes in contact with the air, the hydrogen burns (with an invisible flame) heating up the drywell wall.

* The temperature inside the RPV is actually much higher than what the RPV sensors show, as the RPV wall is being cooled from the outside by water leaking from the injection pipes. But there is a relatively small leak near the top that blows hot steam from inside the RPV into the top region of the drywell, heating it locally.

Of course you can explain anything with the magic words "instrument malfunction". But it is hard to see how a thermocouple could give a reading just a few tens of degrees higher than the correct value. I would expect it to either drop to zero volts (if the wires are severed) or give a lower-than-correct voltage (if the insulation of the wires is compromised).

Since thermocouples require good connections, I can see corrosion introducing offset quite easily. High temperatures, saltwater, steam, oh, I can see error possibilities indeed.

 

[~kujala~]

A nice article in allthingsnuclear about spent fuel pools:

http://allthingsnuclear.org/
(Fission Stories #42: Air Error)

When workers manipulate valves on reactor systems, a second worker must verify the proper configuration is achieved. Valves on spent fuel pool systems don’t require checking.

Instruments monitoring key parameters on reactor systems require backups to ensure the parameters are monitored 24/7. Instruments monitoring key parameters in the spent fuel pools neither require backups nor even to be working themselves.

If we continue to treat irradiated fuel in spent fuel pools so cavalierly, we risk someday having lots of dead cavaliers.

 

[Bandit127]

[URL]http://www.tepco.co.jp/en/news/110311/images/110601_01.jpg[/URL]

I presume this is the heat exchanger for the Unit 2 SFP. Again, ingenuity at work and good to see.

The larger diameter pipes will be bringing in coolant (probably seawater) in an open loop and this will cool the heat exchanger. The smaller pipes will be a closed loop system that circulates clean(er) water around the fuel pool, thus removing heat to the heat exchanger.

As others have suggested, they seem to be taking advantage of pre existing piping for the closed loop part.

It doesn't look great and may not survive another tsunami but it is good engineering given the circumstances and it is a good example of how we are going to engineer our way out of this situation.

In time more elegant and robust solutions will be found, but right now this is (in my opinion) perfect.

Well done the guys and girls at the front line for a big step in the right direction.

 

[etudiant]

The well informed site Atomic Power Review here suggests these are absorption towers for cleaning some of the water.
http://atomicpowerreview.blogspot.com/2011/06/fukushima-daiichi-update-june-1st.html

Not sure which is right, but had thought that the absorption was just one part of a series of process steps,
so this may indeed be a heat exchanger.
Can anyone tell for sure?