Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Dmytry]

I gave my name, and a link to my work pages. Teaching gamma spectrometry to physics students is one of the things I do. I know a bit about the errors that can be made.

http://www.tepco.co.jp/en/press/corp-com/release/11042008-e.html confirms what I said about the database. Their software came with a nuclide library. Short-lived Te-129 had not been listed there as a daughter nuclide of the metastable isomer.

In the re-evalution of their spectra, they looked for the main peaks of Cl-38, and did not see any. See http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110420e11.pdf for the reasons for change.

well ok then I am rather surprised how badly written is the software in question must have been. I am a software developer. This kinda glitch you'd usually test for.
Don't you have to also print out the error range btw? Or the software is so crap it won't give margin of error? When i was studying we had to propagate errors through calculations.

edit: wait, its weird, the data you linked. Note the La-140 at 3.0E2 . They don't think La-140 was a fluke, even though they re-evaluated it, while they do think that Cl-38 was a fluke. even though with compensation for 10 half lifes, Cl-38 must have been at 1.5 E3 which is 5x more than La-140 . I don't know if for some reason one is entirely different part of spectrum from another though.
edit: nope. According to wolframalpha, Cl-38 decays by 4.9MeV beta, while La-140 decays by 3.76 MeV beta. Why is Cl-38 below threshold and La-140 is not?

Also, speaking of criticality detection. They should of simply checked for cs-136 vs cs-137 ratio in SFP4 water, then we could of known for sure if SFP4 was critical or not.

 

[PietKuip]

well ok then I am rather surprised how badly written is the software in question must have been. I am a software developer. This kinda glitch you'd usually test for.
Don't you have to also print out the error range btw?

edit: wait, its weird, the data you linked. Note the La-140 at 3.0E2 . They don't think La-140 was a fluke, while they do think that Cl-38 was a fluke. even though with compensation for 10 half lifes, Cl-38 must have been at 1.5 E3 which is 5x more than La-140 . I don't know if for some reason one is entirely different part of spectrum from another though.

Also, speaking of criticality detection. They should of simply checked for cs-136 vs cs-137 ratio in SFP4 water, then we could of known for sure if SFP4 was critical or not.

I agree that this does not seem to be the most sophisticated software. Anything up to standard should take into account all the peaks, give an error estimate when everything fits with the fingerprint of the nuclide, and ring alarm bells when there are strange discrepancies.

La-140 is likely a daughter of Ba-140 with a halflife of about 13 days.

Yes, it would not be difficult to find unambiguous evidence of criticality (in measurements of fresh samples). Tepco should publish the complete gamma spectra, so that anybody could make their own analysis.

 

[rowmag]

Like Samy24, I also dismissed until now suggestions of recriticality, but ok, if it is something that has to be considered, what would the consequences be? Would it have to be stopped before work could continue? If so, how? If it is on a small-enough scale, could it be worked around somehow?

 

[Dmytry]

I agree that this does not seem to be the most sophisticated software. Anything up to standard should take into account all the peaks, give an error estimate when everything fits with the fingerprint of the nuclide, and ring alarm bells when there are strange discrepancies.

La-140 is likely a daughter of Ba-140 with a halflife of about 13 days.

Yea, but how come they detect La-140 at 1/5 the concentration of Cl-38 . Very scientific approach, review the least convenient things the most. With all respect to technicians i think they need scientists there.

Yes, it would not be difficult to find unambiguous evidence of criticality (in measurements of fresh samples). Tepco should publish the complete gamma spectra, so that anybody could make their own analysis.

Yes. So far it all looks like either
a: they found criticality, but did not tell anyone,
b: they showed no criticality, but did not tell anyone (but they did about reactor #1)
c: they didn't check for criticality.

Given everything, it could be c. Plus, given how much government has flamed them for erring on the side of caution and for publishing incorrect data without review, it looks like they are under pressure not to tell and maybe even not to look as they may be obligated to publish whatever they find.
Plus, some white collar could be just dismissing the criticality all the way (i recall one time one of their officials said that it is hard to imagine re-criticality in shutdown reactor. When responding to either French or IAEA's suggestion to borate water more.)

 

[PietKuip]

Yea, but how come they detect La-140 at 1/5 the concentration of Cl-38 .

Because there is no sign of chlorine-38 in the spectra.

There could not be. Even if Cl-38 (half-life 38 minutes) had been produced by neutron activation in the brine at moderate levels, it should have fallen below detectable concentrations by the time they measured the spectrum ten hours later.

 

[Dmytry]

PietKuip:
ahh, sorry was confused about half life, between I134 and Cl-38 . So it was almost 16 half lifes and thus it'd be 1/65000 of original concentration.
But aren't you stretching "bad software" theory a little too far? Suppose I take a soil sample here, measure it, entering 10 hours as time, would this software give me insane amounts of every short living isotope? How would anyone ship software which fails so much that when you do a test run with stale banana as radiation source, it'd find a lot of short living isotopes?
edit: Though TBH reading about software glitches in critical military systems and such, I've been under impression that a lot of 'certified' software developed using 'formal' development process is very bad in general even though every module is bug-less and meets the specifications.

ahh, here. IAEA says there may be criticality,
TEPCO responds

'The reactors are stopped, so it's hard to imagine re- criticality,' occurring, Tsuyoshi Makigami, a spokesman for the utility, told a news conference today.

http://news.businessweek.com/article.asp?documentKey=1377-aEYAMDQ_BVlo-5TVRB3CR70DGQ7S5OIP73UK3P7

In spent fuel pool(s) especially, I don't understand why one would just dismiss criticality or be highly sceptical of it. There's boral plates between fuel assemblies, to prevent criticality.
http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0933/sec3/196.html
Those boral plates (the lowest melting point of all the things involved) fail, and it will go critical when covered by water. Yet the people here go on with theories that involve failure of a notable percentage of fuel rods and ill-defined 'weird chemistry' keeping out 99.9% of expected caesium, just to avoid highly inconvenient conclusion that the spent fuel pool gone critical.
Some sort of misplaced 'extraordinary claims require extraordinary evidence' while the claims are extraordinarily inconvenient, but not at all scientifically extraordinary.

 

[AntonL]

NHK, Japan's national broadcaster, positioned a TV camera 33 kilometers southwest of the plant, and broadcast the helicopter operation live. At 9:48 a.m. local time a helicopter flying from the west dropped the first load of water almost directly over the No. 3 reactor, though a significant amount spread away from before reaching the target.

http://spectrum.ieee.org/tech-talk/energy/nuclear/helicopters-and-cannons-spray-water-on-japans-unstable-nuclear-plant" Field of view is about the same in this video after appox. 30secs as with the #3 explosion video. A good guess for syncing a sound track.

the videos for the helicopter sprinkling are most likely taken from this location http://watchizu.gsi.go.jp/watchizu.html?b=371307&l=1405230 at an elevation of 750-830 metres and 27 km distant from the NPP and this is not the same location as the videos from the explosions. Using google Earth and maps I cannot find a good location at 33 km distance - possibly the reporters just stated this distance to comply with the 30kM exclusion zone.[PLAIN]http://k.min.us/inr320.JPGThe videos of the explosion, in my opinion, were taken from this point http://watchizu.gsi.go.jp/watchizu.html?b=372016&l=1405540 which is 13km and at an elevation of 582metres. This point also seems to be TV or radio station as a mast and a building is visible on google earth.

Using Google Earth one can draw site lines and check features like the high voltage line towers (vertical lines in the middle of the foreground)
[PLAIN]http://k.min.us/inr1us.JPG

 

[htf]

Teaching gamma spectrometry to physics students is one of the things I do. I know a bit about the errors that can be made.

That's exactly the point. How do you become an expert in gamma spectrometry? Easy! You buy a gamma spectrometer with a fancy software that does the analysis for you. That's the Tepco way. You get away with this approach as long as nothing extraordinary happens. It seems that Tepco's knowledge is limited to normal operation and now they are lost because they are facing a situation that is not described in the manuals. It is not just bad PR we saw from Tepco.

 

[PietKuip]

PietKuip:
ahh, sorry was confused about half life, between I134 and Cl-38 . So it was almost 16 half lifes and thus it'd be 1/65000 of original concentration.
But aren't you stretching "bad software" theory a little too far? Suppose I take a soil sample here, measure it, entering 10 hours as time, would this software give me insane amounts of every short living isotope? How would anyone ship software which fails so much that when you do a test run with stale banana as radiation source, it'd find a lot of short living isotopes?
edit: Though TBH reading about software glitches in critical military systems and such, I've been under impression that a lot of 'certified' software developed using 'formal' development process is very bad in general even though every module is bug-less and meets the specifications.

The software would not do so for all nuclides, as it would give insane results for stuff with millesecond half-lives. That is why their nuclide library includes some parent-daughter relations. But the database did not include this for Te-129, according to the link I gave above.

Before the accident, I would assume that the routine was to measure the gamma spectra on site, within hours. Decay corrections would have been small. But since they lost power, they are sending the samples to a different place. Which takes time, and suddenly corrections for decay become enormous.

And I still think there is an error in the intensities of the re-evaluation: for each Ba-140 decay there is a La-140 decay about 2 hours later; the activity of these two isotopes should be the same, and Tepco's differences are a factor of two or larger.

 

[Dmytry]

The software would not do so for all nuclides, as it would give insane results for stuff with millesecond half-lives. That is why their nuclide library includes some parent-daughter relations. But the database did not include this for Te-129, according to the link I gave above.

Before the accident, I would assume that the routine was to measure the gamma spectra on site, within hours. Decay corrections would have been small. But since they lost power, they are sending the samples to a different place. Which takes time, and suddenly corrections for decay become enormous.

And I still think there is an error in the intensities of the re-evaluation: for each Ba-140 decay there is a La-140 decay about 2 hours later; the activity of these two isotopes should be the same, and Tepco's differences are a factor of two or larger.

well, it was long after the quake... surely they had some generators to have lights, communication, etc?
This is why one has to have something like KHG.
Also, some officials were going from Tokyo to site, and i bet it was not 10 hours either way. Why are those suits that have no clue what so ever and only get in the way are transported around faster than stuff that matters? Doesn't Tokyo have a several dozen labs that can analyse such stuff?
It really is just inexcusable imo if they don't even know if there is criticality or not. I'm kind of inclined to think they themselves don't know and don't want to look.

 

[tsutsuji]

Until now, surveys were conducted outside the 20 km radius, but here's something new :

The science ministry has announced the results of radiation monitoring in areas between one and 21 kilometers from the Fukushima No. 1 nuclear power plant.
http://www.yomiuri.co.jp/dy/national/T110422004001.htm

unfortunately, I can't find the data on http://www.mext.go.jp/a_menu/saigaijohou/syousai/1303726.htm

But there is a map here attached to http://www.yomiuri.co.jp/science/news/20110423-OYT1T00199.htm (red squares show locations above 19 μSv/h).

They poured 200 tons of water into SFP4 on April 22nd and plan for another 140 tons on April 23rd, being careful not to spill water, because extra weight would harm the weak building : http://www3.nhk.or.jp/news/html/20110423/t10015504561000.html http://www3.nhk.or.jp/daily/english/23_12.html

Water is "about half way up the bulb of the dry well" in Reactor No. 1 : http://www3.nhk.or.jp/daily/english/23_05.html

 

[AntonL]

They poured 200 tons of water into SFP4 on April 22nd and plan for another 140 tons on April 23rd, being careful not to spill water, because extra weight would harm the weak building : http://www3.nhk.or.jp/news/html/20110423/t10015504561000.html http://www3.nhk.or.jp/daily/english/23_12.html

To any physicist or engineer it is obvious that SFP4 with an estimated heat load of 2 to 2.4MW is boiling at a rate of about 60-80 tonnes a day - why the bleep tepco cannot say the same, instead they measure the temperature in the furthest corner as close as possible to the wall to show it is 91 degrees and prove that it is not boiling and to state water is lost to evaporation due to the high temperature. I can only think that a boiling radioactive soup is bad PR as it is obvious the amount of contamination carried into the atmosphere is very high. If Tepco really did their job properly then the minimum amount of water would be injected into the pool and have one headache less of what to do with the many tonnes of water spilled every day that needs to stored and decontaminated at high cost. It has been boiling since March the 13th. (https://www.physicsforums.com/showthread.php?p=3244793&highlight=boil#post3244793") instead in the NHK
To loose 140 to 200 tonnes of water per day either means that heat load is higher than estimated or the pool has a leaking.

 

[tsutsuji]

What is not clear is where Friday's 200 tons have gone. "From Saturday, the utility started (...) using a device to monitor (...) the level of cooling water in the pool" ( http://www3.nhk.or.jp/daily/english/23_12.html ) seems to mean that the "device" was not ready on Friday.

Perhaps some amount of the 200 tons were spilled and they found out that they had to do it all over again (with more care and more "devices") on Saturday.

 

[Dmytry]

To any physicist or engineer it is obvious that SFP4 with an estimated heat load of 2 to 2.4MW is boiling at a rate of about 60-80 tonnes a day - why the bleep tepco cannot say the same, instead they measure the temperature in the furthest corner as close as possible to the wall to show it is 91 degrees and prove that it is not boiling and to state water is lost to evaporation due to the high temperature. I can only think that a boiling radioactive soup is bad PR as it is obvious the amount of contamination carried into the atmosphere is very high. If Tepco really did their job properly then the minimum amount of water would be injected into the pool and have one headache less of what to do with the many tonnes of water spilled every day that needs to stored and decontaminated at high cost. It has been boiling since March the 13th. (https://www.physicsforums.com/showthread.php?p=3244793&highlight=boil#post3244793") instead in the NHK
To loose 140 to 200 tonnes of water per day either means that heat load is higher than estimated or the pool has a leaking.

I think it 'probably' gone critical. There was fuel damage, and boal plates would get damaged as well. If boral was damaged, spent fuel can go critical unless water is borated. If it is leaking they can't keep water borated. Leak does not in the slightest exclude criticality, quite to the contrary, if the thing is leaking it means they wouldn't be able to easily do anything about criticality.

I really don't understand this scepticism about criticality, as if it was some sort of extraordinary claim. Extraordinarily bad, yes, but totally ordinary in the scientific sense. Good or bad, criticality is the only theory that had been proposed which explains the facts ("there might be weird chemistry" doesn't count for theory). A very simple theory, very plausible, and best yet easily falsifiable if it is false. Scepticism is good, but not when how sceptical you are is proportional to how inconvenient is the theory. And not when you're unduly sceptical of danger.

I am instead sceptical of the claims that it would not go critical in the event of re-flooding after overheating / fuel damage / temperatures high enough for hydrogen production, which is higher than melting point of aluminium. The claim that it did not go critical is so far is unsubstantiated. It is not shown that boral had not failed, it had not been shown that there's still any shutdown margin. In safety you have to be particularly sceptical of claim that you are safe and everything is good, and default to worst case.

 

[tsutsuji]

The following article http://mainichi.jp/select/today/news/20110424k0000m040046000c.html (in Japanese, written on March 23rd at 7:30 p.m. JST ) has a slightly different story :

On March 21st the water level in SFP4 was 2 metres above the top of the fuel, with a temperature of 91 °C.

Then on March 22nd and March 23rd they poured 140 tons + 140 tons = 280 tons of water. Then the water level rose to 4 metres above the top of the fuel. And the temperature went down to 66 °C.

Until then, they used to pour an average of 70 tons of water into SFP4 every day.

A 30 cm x 30 cm x 5 cm, 900 mSv/h highly radioactive concrete debris was found and removed near Reactor No. 3 on March 21st : http://www.asahi.com/national/update/0423/TKY201104230396.html

They are considering clearing a nearby forest to make space for the water waste tanks : same http://www.asahi.com/national/update/0423/TKY201104230396.html

 

[Dmytry]

tsutsuji: what are the dimensions of spent fuel pool? We could easily check those numbers. What would be interesting, is how much water they pour daily, averaged, not some special days when they pour a lot more or a lot less than usual. Also, what would be interesting - was the fuel uncovered? If the official theory is that building 4 was destroyed by hydrogen explosion of hydrogen originating in spent fuel pool, then fuel had to run dry and overheat to make more hydrogen than usual, and that would damage boral plates. Either way, they should imo presume that it gone critical, and then falsify that hypothesis with direct measurement if it didn't.

 

[Cainnech]

To loose 140 to 200 tonnes of water per day either means that heat load is higher than estimated or the pool has a leaking.

FWIW. There seem to be water in the reactor building and turbine building of reactor 4.

http://www.yomiuri.co.jp/science/news/20110423-OYT1T00357.htm?from=main1 (in Japanese)
http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=ja&tl=en&u=http%3A%2F%2Fwww.yomiuri.co.jp%2Fscience%2Fnews%2F20110423-OYT1T00357.htm%3Ffrom%3Dmain1&act=url (google translation)

Translation according to a Japanese blogger:

Contaminated water with radioactive materials in TEPCO's Fukushima I Nuclear Power Plant Reactor 4 turbine building has risen 20 centimeters in 10 days. There's also 5-meter deep water in the reactor building, estimated to be 4,000 tons, as has been already disclosed by Nuclear and Industrial Safety Agency; this is in addition to the amount of contaminated water from other reactors.

TEPCO has been transporting the contaminated water with high radioactive materials from Reactor 2 [turbine building] to the central waste disposal facility. But the amount that the facility can store safely is likely to be half of what was planned, and there is no clear plan to deal with the contaminated water from other reactors.

According to TEPCO, the water in the Reactor 4 turbine building basement was 0.9 meter (2.95 feet) deep on April 13, and 1.1 meters (3.61 feet) deep as of 6:00PM on April 22. It rose 20 centimeters in about 10 days. In the adjacent Reactor 3, water is being injected at 6.8 tons/hour to cool the Reactor Pressure Vessel (RPV). TEPCO suspects that the water leaked from the RPV is leaking through the cracks in the wall that separates the Reactor 3 turbine building and the Reactor 4 turbine building.

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

 

[AntonL]

On March 21st the water level in SFP4 was 2 metres above the top of the fuel, with a temperature of 91 °C.

Then on March 22nd and March 23rd they poured 140 tons + 140 tons = 280 tons of water. Then the water level rose to 4 metres above the top of the fuel. And the temperature went down to 66 °C.

Until then, they used to pour an average of 70 tons of water into SFP4 every day.

70 tonnes of water per day is roughly the right amount to replace boiled off water and confirms https://www.physicsforums.com/showthread.php?p=3244793&highlight=boil#post3244793"

.. what are the dimensions of spent fuel pool?

Capacity = 1425 m³ http://www.nisa.meti.go.jp/english/files/en20110406-1-1.pdf"

The pool is about 11 metres deep,
so 1 metre level change is 1425/11= 129.5m3 of water

 

[elektrownik]

Contaminated water with radioactive materials in TEPCO's Fukushima I Nuclear Power Plant Reactor 4 turbine building has risen 20 centimeters in 10 days. There's also 5-meter deep water in the reactor building, estimated to be 4,000 tons, as has been already disclosed by Nuclear and Industrial Safety Agency; this is in addition to the amount of contaminated water from other reactors.

It is from tsunami ? I don't think so, reactor building should be water sealed... If the water is not from tsunami then it must be from SFP, but in they injecting 70t/day then 4000:70= 57 days... So is this mean that SFP is leaking ?

 

[elektrownik]

What about rain ?

But how so much rain could get into reactor building ?

 

[tsutsuji]

But how so much rain could get into reactor building ?

Directly through the roof ? But that would account for less than 5 meter. Rainfall was 40 mm in March 2011 in Fukushima city : http://www.data.jma.go.jp/obd/stats/etrn/view/monthly_s3_en.php?block_no=47595&view=13

 

[RealWing]

It is from tsunami ? I don't think so, reactor building should be water sealed... If the water is not from tsunami then it must be from SFP, but in they injecting 70t/day then 4000:70= 57 days... So is this mean that SFP is leaking ?

Some or all of the water in the RB likely came from early helicopter water drops and then later from the fire/concrete trucks spraying water over the pool area. For sure some of this water missed the pool and ran down into the lower floors. No idea how much.

The pool may also be leaking - especially when they keep saying they want to get in and shore up the bottom of the pool. The integrity of the pool must be questionable.

 

[Jorge Stolfi]

I've updated my plots of #Fukushima reactor variables, up to #NISA release 110 (23/apr 15:00).
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html

No big news. They are pumping a little bit less water, and reporting fresh water flow measurements with every release (instead of repeating week-old numbers, as they used to).

Pressure in #1 RPV still rising; temp was decreasing but now rose a bit (109 C).

The two radiation measurements in #2 torus are hugely divergent (0.51 Sv/h falling, 136 Sv/h rising).

Reactor #3 RPV is sucking, really (50 kPa abs). Drywell pressure 1 bar, torus 2 bar. Does that mean the drywell (!) is flooded, up to ~2m above the bottom of the RPV?

 

[Jorge Stolfi]

Some or all of the water in the RB likely came from early helicopter water drops and then later from the fire/concrete trucks spraying water over the pool area. For sure some of this water missed the pool and ran down into the lower floors. No idea how much.

The helicopter dumps may have been 5 tons per trip. IIRC all the truck spraying amounted to a few hundred tons. It seems we are one order of magnitude off.

Tsunami water may have entered trough the fuel loading door at ground level.

Presumably the reactor vessel and cooling loop tanks were still full of water when the earthquake struck. If the explosion damaged the wrong pipes/valves, could that water have drained out to the basement?

Water may have come from other buildings through the cable trenches or other underground routes. I wish TEPCO or NISA measured not only the water being pumped into the reactors but also the amount of water flowing out of the return pipes. "What did you say, 'there are no return pipes'??"

 

[tsutsuji]

I withdraw my earlier comments concerning the meaning of O.P. in altitude measurements.

O.P. means Onahama Port Standard Construction Level and it is related to T.M.S.L. (Tokyo Bay Mean Sea Level) with the relation O.P. + 0 m = T.M.S.L - 0.727 m.

Onahama Port is located 55 km south of the Fukushima Daichi plant.

Source : the following attachment : section view of the turbine building and sea water circuits on page 10 of http://www.pref.fukushima.jp/nuclear/pdf_files/onhaisui-h19houkokusyo.pdf available from http://www.pref.fukushima.jp/nuclear/anzen/onhaisui.html

 

[GJBRKS]

Reactor #3 RPV is sucking, really (50 kPa abs). Drywell pressure 1 bar, torus 2 bar. Does that mean the drywell (!) is flooded, up to ~2m above the bottom of the RPV?

Has anyone heard an official explanation for the <1 atm pressures ?

The only ones besides the sensors being broke that I can think of is that nothing is getting in ,
and the temperature is so high in there that it pushes all gasses out of containment.
Or that the sensors are encased by condensed salt deposits.

 

[NUCENG]

...

for flood, helipad on the roof + connectors there. Just as there are connectors for fire trucks on the first floor, right? (German nuclear power plants have that AFAIK). Also there's RCIC that keeps reactor cooled for a bit of time (hours?).
US plants where I have been DO have ground level connections for external fire pumps to fill spent fuel pools and inject water into the reactor. Right now they also have diesel driven pumps available on site to perform that function or spray down the building. I can see a benefit in having some resources pre-positioned off site where they can’t be damaged in a site specific event. I am not certain the best delivery site is the roof, simply because that may be inaccessible due to damage, fire, or radiation. Perhaps it requires more than one landing site. Every plant already has a helicopter landing area, usually in a parking lot or cleared area. When plants moved employee parking away from buildings post 9/11 it left large paved open areas available for landing equipment.

Not accusing you of lying, really. You may well be a nuclear engineer all right,

"There was also NUCENG who from earlier discussion of role of CsI in the transport of Cs-137 along with I-131, I have assumed was some sort of bystander with no clue how to relate Becquerel to number of atoms and half life (even if it is 10X the Iodine to Caesium in Bq, it is 1/136 or so the Iodine to Caesium in number of atoms coz I-131 has half life 8 days and Cs-137 has half life 30 years). Which would of been totally fine if he was. I don't mind explaining Bq to people outside nuclear industry and how it relates to half life and number of atoms. I don't think everyone has to know how decay works. Then it turns out he's in fact (or claims to be) a nuclear engineer with many years of experience, involved in uprating, and goes on with his ultra arrogant attitude that he knows enough and has nothing to learn. Right, precisely the kind of person I'd trust with uprating.
Really, this forum is such an eye opener."

Those are your words Dmytry. Have I disrespected you, your opinions, or even your arguments? I think most of the posters here would read that and at least think you have a low regard for my input on these forums.

the thing is, I think I misunderstood your attitude about safety especially when it comes to things such as criticality. It appeared as if you have view that it has to be presumed that there is no criticality. Sorry if that is not what you meant and you were simply playing devil's advocate. IMO it has to be presumed that there is criticality if there might be criticality and you don't know. Just like you have to presume there will be criticality if there might be criticality, to avoid criticality accidents, and a lot of criticality accidents look to me like an example of violation of that approach.

There is the problem. You are absolutely wrong about my attitude. I absolutely believe TEPCO and the people on this forum should be looking for evidence of recriticality. But it should not blind us into ignoring other possibilities. Science, Engineering, and Forensic Investigations should be looking for truth, proof of what did happen, not speculation or opinions of what might have happened. That is what I am trying to do here. I have training, information, and experience related to these threads that I will share. I am pro-nuclear. But I respect your right to take the opposite view. Can’t you try to give others on this thread the same respect?

You haven't offered some specific explanation of high iodine levels (highest of everything), yet you say it may be caused by something else. Well it might be, but for start one thing it can't be caused by:
CsI role in transport of Caesium : Caesium Iodide has something around 1360 Bq of iodine for 1 Bq of Caesium, so it cannot be that everywhere we have CsI leaking keeping the Cs to I ratio constant, to propose so is to be unaware of mol to Bq conversion.
Ditto for other caesium+iodine chemical compounds. Once again, I may have misunderstood your point on CsI, not sure why CsI was brought up, in the solution there is no CsI anyway, just the ions, so I thought you were explaining the ratio with CsI leaving the fuel.

Furthermore, there has to be a giant disparity between relative rates of transport of caesium and iodine from fuel into the water for the spent fuel pool #4 and for all the reactors. 3 orders of magnitude. While for 3 other reactors it is same order of magnitude (and same order of magnitude ratio as for Chernobyl i think, and TMI, but someone should check the numbers).
Why would it hit the spot where it is same order of magnitude as other reactors a few weeks ago? Luck?
I have provided an estimate of the total amounts of I-131 and Cs-137 that were available for release. At the time of shutdown on March 11, the core in unit 2 or unit 3 21 different isotopes of I and 20 isotopes of Cs. There was a total of 17.6 kg of I and 230 kg of Cs. In terms of activity that initial source term consisted of 2.8E18 Bq of I and 1,7E14 Bq of Cs.
I provided you with references that describe the chemical makeup of the released I and Cs. 95% of the I released from damaged fuel is released as CsI. I brought that up because that is the predominant chemical form for transport of Iodine. Other forms include Iodine gas, HI and possibly some organic compounds.

If released into air CsI is agglomerative. It forms clumps with other CsI molecules. It can be filtered from air easily. It tends to deposit readily. It is hygroscopic. It likes to jump into the nearest pool. Once there it is in Cs+ and I- ions. If the pool becomes acidic Iodine gas will re-evolve and be released to the atmosphere. In other words it is not likely to go very far.

Even with 95% of Iodine hooking up with Cs, there is still a lot of excess Cs being released. Cs is a reactive metal. Cs readily reacts with many chemicals including water where it forms a strong base CsOH and releases hydrogen gas. It is non-volatile and will not boil off. It will plate out or deposit. As you say, it will have very different transport characteristics from Iodine particulates (CsI) or gasses. If you get that point you will understand why a single measurement at a sample point is very difficult to interpret the I/Cs ratio because Iodine and Cs are not transported the same ways.

I am not sure I understand your reference to 1360 Bq of Iodine per Bq of Cs. If a molecule of CsI is composed of Cs-137 and I-131 the I is more likely to decay first because its half life is about 1688 times shorter. But a CsI molecule may form in any combination of isotopes of I and CS including stable ones. It isn’t luck it is physics and chemistry.

Dmytry, I have provided this information as factually as I can and have explained or posted references where I obtained this information. Check out my post #4632. In this case I cannot provide a definitive counter to passible criticality. I am not convinced, but us devils advocates can be pretty stubborn.

This forum is interesting and informative. If we can all keep the rhetoric down and respect each other we will have a much better chance of making this forum useful. We’ve already seen one thread shutdown, we all lose when that happens. You seem to see things so clearly, but you lose any chance of persuasion when you belittle others or call them stupid, or liars. Come on in, the water is fine, even if it glows in the dark. Peace?

 

[hbjon]

Like Samy24, I also dismissed until now suggestions of recriticality, but ok, if it is something that has to be considered, what would the consequences be? Would it have to be stopped before work could continue? If so, how? If it is on a small-enough scale, could it be worked around somehow?

Does anyone know the feasability of using a fully enclosed dredging machine that is custom built to withstand high temps and can be remotely operated? The goal is to move the fuel into a controlled environment like a tank of heavy borated water, right?

 

[Guest Member]

(NHK) TEPCO: Highly radioactive concrete fragment found

The operator of the damaged Fukushima Daiichi nuclear power plant says that concrete debris emitting a high level of radiation has been found near the Number 3 reactor.

http://www3.nhk.or.jp/daily/english/24_01.html

 

[triumph61]

70 tonnes of water per day is roughly the right amount to replace boiled off water and confirms https://www.physicsforums.com/showthread.php?p=3244793&highlight=boil#post3244793"



Capacity = 1425 m³ http://www.nisa.meti.go.jp/english/files/en20110406-1-1.pdf"

The pool is about 11 metres deep,
so 1 metre level change is 1425/11= 129.5m3 of water

Don´t forget the open Gate to the Reactor. There also a lot of Water.

 

[Samy24]

(NHK) TEPCO: Highly radioactive concrete fragment found

The operator of the damaged Fukushima Daiichi nuclear power plant says that concrete debris emitting a high level of radiation has been found near the Number 3 reactor.

http://www3.nhk.or.jp/daily/english/24_01.html

What inventory has such a high radiation in a power plant?
The size of the plate found was 30x30x5 cm. For fuel assemblies the size does not fit even if they are broken during the explosion of unit 3.

 

[PietKuip]

(NHK) TEPCO: Highly radioactive concrete fragment found

The operator of the damaged Fukushima Daiichi nuclear power plant says that concrete debris emitting a high level of radiation has been found near the Number 3 reactor.

http://www3.nhk.or.jp/daily/english/24_01.html

"the concrete block has been stored safely in a container with other debris"

Don't they want to know what it is?

Concrete does not get this radioactive by neutron activation.
It seems to me there must have been some corium on this piece.

So where is the rest?

 

[Samy24]

"the concrete block has been stored safely in a container with other debris"

Don't they want to know what it is?

Concrete does not get this radioactive by neutron activation.
It seems to me there must have been some corium on this piece.

So where is the rest?

I did not thought about that. You are right, the fragment found could only have a very small piece of radioactive material on the surface.

 

[NUCENG]

I did not thought about that. You are right, the fragment found could only have a very small piece of radioactive material on the surface.

This chunk was emitting 900 mSv per hour. Workers received 3.17 mSV getting it into a container. This thing was DANGEROUS. It hasn"t been lost. They know where it is.

They were trying to clear debris near the switchyard, probably so they can continue restoring power to equipment that still may be operable and can help stabilize the plant. Our wishes for more information pale in importance to what they are trying to do. With junk like this lying around these people are risking their lives. Give them a break.

Perspective, please!

 

[PietKuip]

This chunk was emitting 900 mSv per hour. Workers received 3.17 mSV getting it into a container. This thing was DANGEROUS. It hasn"t been lost. They know where it is.

They were trying to clear debris near the switchyard, probably so they can continue restoring power to equipment that still may be operable and can help stabilize the plant. Our wishes for more information pale in importance to what they are trying to do.

There is more of this lying about. They need to know what it is. That is why one has robots, to look at stuff before a worker would handle it.
http://amptek.com/x123cdte.html" has been on Mars (and it is not expensive). It could have diagnosed what it was, what the dangers of this place are.