Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Astronuc]

Nobody has tackled this question. Reasoned speculation would be fine!

I don't believe there is evidence of a 'large' (not quantified) steam explosion in any of the units. I would expect a big plume of steam if that were the case.

IF (and for now that's a BIG IF) there was a sufficient melting - I think it would dribble down into the water, so it would drop in, get quenched with steam blanketing the melt, which would prevent rapid heat transfer to the surrounding water.

If anyone has seen lava from Kilauea in the ocean - it's doesn't explode. It just oozes and bubbles.

If the water activity rises, it probably means more fuel is exposed. That does not necessarily require melting, but rather could be accomplished by simply oxidation and/or fracturing of the Zircaloy-2 cladding. This is a rather slow process.

Whatever is happening has been happening over two weeks - going on three weeks now. So far - It has been a slow process!

 

[Pheesh]

what other scenarios could explain 18sv/hr in the secondary containment besides the core melting through the floor of the primary? Does this imply the core has gone critical, or not necessarily so?

 

[Joe Neubarth]

what other scenarios could explain 18sv/hr in the secondary containment besides the core melting through the floor of the primary? Does this imply the core has gone critical, or not necessarily so?

Well, the one machine that they are using to measure the 18 Sieverts could be faulty.

 

[Astronuc]

what other scenarios could explain 18sv/hr in the secondary containment besides the core melting through the floor of the primary? Does this imply the core has gone critical, or not necessarily so?

S/C = Suppression Chamber. If there is water there and it came from the RPV, then I would expect dissolution of exposed fuel - IF the activity is due to fission products.

If one only measures activity, that doesn't necessarily tell one what isotopes are causing the activity. One needs to perform radioassays, e.g., gamma spectroscopy, and key on certain elements.

If one detects very short-lived radionuclides, with half-lives of seconds, then that would indicate a recent criticality event based on the fact that they haven't yet decayed away. I don't think we're seeing that.

If there is water in the base of the RPV - there is no melting. That's straightforward physics. If there has been water in the base of the RPV since March 12, there has been no melting through the RPV.

Well, the one machine that they are using to measure the 18 Sieverts could be faulty.

That's a possibility. There is also the possibility of accumulation of radioactive source near the detector.



BTW - （English version） Readings at Monitoring Post out of 20 Km Zone of Fukushima Dai-ichi NPP
http://www.mext.go.jp/english/radioactivity_level/detail/1304082.htm

 

[AtomicWombat]

http://www.reuters.com/article/2011/03/30/us-japan-nuclear-iaea-idUSTRE72T5JR20110330"

(Reuters) - Radiation measured at a village 40 km from Japan's crippled nuclear plant exceeded a criterion for evacuation, the U.N. nuclear watchdog said on Wednesday, the latest sign of widening consequences from the crisis.

The finding could increase pressure on Japan's government to extend the exclusion zone beyond 20 km (12 miles) around the Fukushima power plant, which has leaked radioactive particles since it was hit by a huge earthquake and tsunami on March 11.

Criticized for weak leadership during Japan's worst crisis since World War Two, Prime Minister Naoto Kan has said he is considering enlarging the evacuation area to force 130,000 people to move, in addition to 70,000 already displaced.

"The first assessment indicates that one of the IAEA operational criteria for evacuation is exceeded in Iitate village," Denis Flory, a deputy director general of the International Atomic Energy Agency (IAEA), said.

"We have advised (Japan) to carefully assess the situation and they have indicated that it is already under assessment," he told a news conference.

Greenpeace this week said it had confirmed radiation levels in this village northwest of the plant high enough to evacuate. But Japan's nuclear safety agency on Monday rebuffed a call by the environmental group to widen the evacuation zone.

There are nearly 2 million people with 80 km of Fukushima Daiichi. I can understand the reluctance to evacuate. On the other hand that is a lot of people potentially at risk.

 

[Bodge]

Cs-137 - 3.7 megabecquerels / m^2 @ 25km NW of plant.

http://blogs.nature.com/news/thegreatbeyond/2011/03/fukushima_update_against_the_o_1.html

http://www.iaea.org/newscenter/news/tsunamiupdate01.html

It is a disgrace to not evacuate from these areas.

I can understand not evacuating in the 1st week of the crisis, but not evacuating now is nothing short of criminal.

edit, also 25 Mbec/m^2 of I-131 - has everyone been issued KI tablets at these distances?

 

[AtomicWombat]

Nobody has tackled this question. Reasoned speculation would be fine!

I strongly suspect that the explosion of the R3 building originated within the primary containment, given its highly directional nature (upwards). (I can't see evidence for this in R1 or R2.)

I originally believed this was due to fuel melting through to a flooded drywell creating a steam explosion plus a violent reaction of super-hot zirconium with water. I've posted my thoughts previously including estimates of the "impulse pressure" required to lift the reactor plug segments to a height of about 500 metres - seen in the video of the explosion. This pressure estimate was ~ 3 times the design pressure for the reactor. But these are still speculative calculations.

The radiation contamination figures do not seem to bear this out. The most contaminated water leakage is from reactor 2.

So I concede it is possible that a steam explosion in the wet or dry well may be the origin of the explosion in R3, without a catastrophic rupture of the reactor vessel (RV). I still have not worked out a mechanism.

Also, Arnie Gundersen's suggestion that the main leakage in reactor 2 is from leaking seals on the control rod drive mechanism may give a direct route to the outside, assuming the pipe breakages are in the secondary containment. So it's possible that the situation in reactor 3 is more dire, but that transfer of radioactive material is better contained. This is just hand-waving so I'll stop now.

 

[Astronuc]

Cs-137 - 3.7 megabecquerels / m^2 @ 25km NW of plant.

http://blogs.nature.com/news/thegreatbeyond/2011/03/fukushima_update_against_the_o_1.html

http://www.iaea.org/newscenter/news/tsunamiupdate01.html

It is a disgrace to not evacuate from these areas.

I can understand not evacuating in the 1st week of the crisis, but not evacuating now is nothing short of criminal.

edit, also 25 Mbec/m^2 of I-131 - has everyone been issued KI tablets at these distances?

I believe they started moving people out two weeks ago.

From the IEAE site

The second team made additional measurements at distances of 32 to 62 km, at directions North to Northwest from the Fukushima nuclear power plant. At these locations, the dose rates ranged from 0.5 to 6.8 microsievert per hour. At the same locations, results of beta-gamma contamination measurements ranged from 0.05 to 0.45 Megabecquerel per square metre.

Based on measurements of I-131 and Cs-137 in soil, sampled from 18 to 26 March in 9 municipalities at distances of 25 to 58 km from the Fukushima Nuclear Power Plant, the total deposition of iodine-131 and cesium-137 has been calculated. The results indicate a pronounced spatial variability of the total deposition of iodine-131 and cesium-137. The average total deposition determined at these locations for iodine-131 range from 0.2 to 25 Megabecquerel per square metre and for cesium-137 from 0.02-3.7 Megabecquerel per square metre. The highest values were found in a relatively small area in the Northwest from the Fukushima Nuclear Power Plant. First assessment indicates that one of the IAEA operational criteria for evacuation is exceeded in Iitate village. We advised the counterpart to carefully access the situation. They indicated that they are already assessing.

As far as food contamination is concerned, 35 samples taken from 25-29 March, and reported on 29 March, for various vegetables, fruit (strawberry), seafood, pork and unprocessed raw milk in nine prefectures (Chiba, Gunma, Ibaraki, Kanagawa, Nagano, Niigata, Saitama, Tochigi and Yamagata), stated that results for iodine-131, caesium-134 and caesium-137 were either not detected or were below the regulation values set by the Japanese authorities.

. . . .

1 MBq = 27 uCi.

I'm not minimizing this very serious situation.

http://www.new.ans.org/pi/resources/dosechart/msv.php

0.3 mSv = typical background in US, vs 61 mSv based on 1 year at 7 uSv/hr. It is certainly higher (200x) than background, but I don't believe someone would stay at the same exposure for all of 1 year.

I expect people in that area have been evacuated. Certain places do have higher activity than one should be exposed to on an ongoing basis.

 

[AtomicWombat]

Cs-137 - 3.7 megabecquerels / m^2 @ 25km NW of plant.

http://blogs.nature.com/news/thegreatbeyond/2011/03/fukushima_update_against_the_o_1.html

http://www.iaea.org/newscenter/news/tsunamiupdate01.html

It is a disgrace to not evacuate from these areas.

I can understand not evacuating in the 1st week of the crisis, but not evacuating now is nothing short of criminal.

edit, also 25 Mbec/m^2 of I-131 - has everyone been issued KI tablets at these distances?

From the UCS site:

http://allthingsnuclear.org/post/4213197648/iaea-confirms-very-high-levels-of-contamination-far"

The full text:

"Today the IAEA has finally confirmed what some analysts have suspected for days: that the concentration per area of long-lived cesium-137 (Cs-137) is extremely high as far as tens of kilometers from the release site at Fukushima Dai-Ichi, and in fact would trigger compulsory evacuation under IAEA guidelines.

The IAEA is reporting that measured soil concentrations of Cs-137 as far away as Iitate Village, 40 kilometers northwest of Fukushima-Dai-Ichi, correspond to deposition levels of up to 3.7 megabecquerels per square meter (MBq/sq. m). This is far higher than previous IAEA reports of values of Cs-137 deposition, and comparable to the total beta-gamma measurements reported previously by IAEA and mentioned on this blog.

This should be compared with the deposition level that triggered compulsory relocation in the aftermath of the Chernobyl accident: the level set in 1990 by the Soviet Union was 1.48 MBq/sq. m.

Thus, it is now abundantly clear that Japanese authorities were negligent in restricting the emergency evacuation zone to only 20 kilometers from the release site."

 

[Bodge]

Thanks for all your replies Astronuc, much appreciated.

re. soil contamination in the areas where the hourly dose rate is shown to be highest, we have no way of knowing how much dust could be ingested by people and their pets.

I certainly wouldn't want to keep a dog that was digging in that dirt!

"Japan has ordered those within a 20 km radius from the plant to leave and is encouraging those living in a 20-30 km ring to do the same, and if they don't, to stay inside."

The NRC weren't kidding on the 17th when they recommended a 50km ring.

 

[Reno Deano]

Wrong!

With water being boiled by a 4.3MW heater at a rate of 6m3/hour, and the fuel rods being about 4metres tall and the upper 1.7 to 2 metres being above water, steam is escaping at some fantastic rate at any outlets above the water level.

If the top was intact and the leak at the bottom then no water would be in the vessel

You must always consider all facts before making a decision.

The dry well will hold water and leak it, as was being proven by flooding it. More than likely there is almost equal water in the dry well as in the RPV. You just have to keep adding more water due to size of the Dry Well and Primary containment area. If there was only a exit avenue above the Guide Plate then they would have succeeded in flooding the RPV long ago.

 

[M. Bachmeier]

Has the subject of Sodium Pentaborate been brought up?

http://www.ceradyneboron.com/products/nuclear-power/chemistry/enriched-sodium-pentaborate/

Was Fukushima Daiichi equipped with such systems and if not why?

 

[AntonL]

KYODO 11:16 31 March
NEWS ADVISORY: Radioactive iodine 4,385 times legal limit found in seawater near plant

 

[M. Bachmeier]

NHK (world live) just reported radioactive iodine 4485 times normal in sea water by plant. (EDIT not 44185, sorry... AntonL got there before me)

 

[Astronuc]

Has the subject of Sodium Pentaborate been brought up?

http://www.ceradyneboron.com/products/nuclear-power/chemistry/enriched-sodium-pentaborate/

Was Fukushima Daiichi equipped with such systems and if not why?

I would expect that it is equipped with the Standby Liquid Control System.

See - http://pbadupws.nrc.gov/docs/ML0210/ML021080117.pdf (page 8, Sec. 3.7.3 Recriticality Concerns, or search for pentaborate)

See also - IDENTIFICATION AND ASSESSMENT OF BWR IN-VESSEL SEVERE ACCIDENT MITIGATION STRATEGIES
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/24/072/24072657.pdf
6. REFLOOD WITH BORATED WATER

 

[M. Bachmeier]

I would expect that it is equipped with the Standby Liquid Control System.

See - http://pbadupws.nrc.gov/docs/ML0210/ML021080117.pdf (page 8, Sec. 3.7.3 Recriticality Concerns, or search for pentaborate)

See also - IDENTIFICATION AND ASSESSMENT OF BWR IN-VESSEL SEVERE ACCIDENT MITIGATION STRATEGIES
http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/24/072/24072657.pdf
6. REFLOOD WITH BORATED WATER

Thank you Astronuc.

So if the system had been used preemptively, would it likely have helped? And, once backup power was lost the option was no longer available?

"The PNL study5 provides the estimate that a boron-10 concentration of between 700 and 1000 ppm would be required within the vessel to preclude criticality once control blade melting had occurred. This is much greater than the concentration (about 225 ppm) attainable by injection of the entire contents of the SLCS tank."


"Furthermore, the dominant loss-of-injection accident sequence is station blackout, and without means for mechanical stirring or heating of the injection source, the ability to form the poison solution under accident conditions becomes of prime importance. Hence the need for the alternate chemical form."

 

[Astronuc]

I would expect that the system was employed as soon as they lost power or the EDGs, but I don't know.

At the moment, I don't know the details, so I can't answer. Hopefully, we'll learn the details in time.

 

[Joe Neubarth]

Thank you Astronuc.

So if the system had been used preemptively, would it likely have helped? And, once backup power was lost the option was no longer available?

"The PNL study5 provides the estimate that a boron-10 concentration of between 700 and 1000 ppm would be required within the vessel to preclude criticality once control blade melting had occurred. This is much greater than the concentration (about 225 ppm) attainable by injection of the entire contents of the SLCS tank."


"Furthermore, the dominant loss-of-injection accident sequence is station blackout, and without means for mechanical stirring or heating of the injection source, the ability to form the poison solution under accident conditions becomes of prime importance. Hence the need for the alternate chemical form."

Aren't these the same people who followed up the sea water injection with the Boric Acid injection. And then they wonder why they have seen one reactor appear to go somewhat critical after it had its rods fully inserted on March Eleventh. Could the IAEC be wrong?

 

[NUCENG]

I'll comment later to the last few questions.

Meanwhile, based on a paper I just received, there are about 63 elements in the set of fission products of LWR fuel. Some are in extremely minute quantities.

The key elements of interest are:

U, Pu, (Np, Am, Cm)=f(BU) = fuel and transuranic elements (not fission products)

fission products:
Zr, Xe, Mo, Ce, Ru, Nd
Sr, Cs, Ba, La, Y, Tc, Pr
Rb, Te, Pd, I, Rh

Some are more significant radiologically or mobility-wise (Xe, Kr, I, Cs, . . . )

more later

One thing to remember, the normal list of fission products and decay chains will only tell part of the story. There is a lot of very high energy radiation. We are probably seeing ongoing neutron activation, actibation similar to cosmic radiation in the upper atmosphere and who knows what kind af ionization and chemical interactions. We have talked of the zirconium water interatction. There are going to be a lot of strange effects. Has anybody come up with an explanation of the Cl-38 in early isotope reports?

 

[AntonL]

The sea water samples with highest radiation levels are taken 330 metres south - the yellow line is 330 metres according to google.

 

[NUCENG]

Joe:

I looked very carefully at the earlier frames from the helicopter fly over as well as the satellite images. These are the two largest pieces of debris I could identify that were obviously out of place (arrows). I take them to be pieces of the roof of one of the buildings, perhaps from the large vertical blast at Bldg 3. Who knows?

Image from DigitalGlobe.com with my annotation.

http://i306.photobucket.com/albums/nn270/tcups/LgDebris.png

The lower of the two arrows points to a white object that looks like the missing cover or roof of the row of storage areas just to the right. It looks like stacks of barrels, probably of packaged industrial or low level waste. It was moved closer to the plant buildings and may have been moved by tsunami backflow. Has anybody seen how much of the site was covered in the upflow?

 

[|Fred]

I strongly suspect that the explosion of the R3 building originated within the primary containment

Did you take into account that the concrete Pressure containment vessel is filled with nitrogen in order to prevent such explosion.

 

[AtomicWombat]

Did you take into account that the concrete Pressure containment vessel is filled with nitrogen in order to prevent such explosion.

Yes. A steam explosion can occur without air being present:
http://en.wikipedia.org/wiki/Steam_explosion"

And at high enough temperature (>1700 Celsius) zirconium also reacts explosively with steam producing hydrogen without the need for air.
Zr + 2H2O -> ZrO2 + 2H2

Of course once hydrogen escapes the containment it can also explode in air.

 

[NUCENG]

http://www.fairewinds.com/content/what-we-do"

Opnion of update on Fukushima by a Nuclear scientist. From the site-how water may have leaked outside containment, into trenches:

http://fairewinds.com/sites/default/files/bwr-crd5.jpg

The "70 or 80" of rods that are damaged are fuel rods. The diaqgram you included is of the control rod drive system. Any leakage from there will be into the bottom of the dryell (primary containment) It still takes a breach of that to direct release to the sea.

 

[razzz]

On another board some guy said one of the diesel backup generators was moved 30' by the flow but didn't quote a source. I have no idea where the generators are/were positioned.
From http://www.skynews.com.au/japan/article.aspx?id=591895&vId="

'Now we estimate the height at more than 14 metres. We have found traces of the tsunami at such elevations,' TEPCO spokesman Naoki Tsunoda said, adding that the wave was 14 metres high when it passed through the plant's parking area.

A tsunami can surge to an elevation higher than its height at the time when it hits shore, Japanese media noted.

The stricken plant's twin complex, some 10km to the south, was also hit by the tsunami but received less extensive damage.

An unidentified subcontract worker at the Fukushima No. 2 plant told public broadcaster NHK that he evacuated to a hill immediately after the quake crushed an embankment and broke the arm of a crane at his plant.

'There was a backwash which left the seabed clearly seen some 200 metres offshore from the beach,' he said.

'Then the tsunami approached all at once and surged onto the plant.

'The tsunami cleared high above the dyke and came rushing down to wash away one parked car after another. I was very scared,' he said.

The plants were designed to withstand earthquakes of magnitudes up to 8.0 and tsunami waves of up to 5.7 metres at the No. 1 plant and 5.2 metres at the No. 2

 

[NUCENG]

REACTOR ACCESS FLOOR LAYOUT?


Can anyone here add to or correct anything I may have wrong here, please. These are annotated images from drone fly over posted earlier by Fred with what I "think" may be the layout of the reactor access level floors. As can be seen, this will substantially affect how the remainder of the damages might be interpreted.

Blue Rectangle = Pools
Orange Ovals, Circles = Dry Well Cap and approximate positon of Dry Well Plug on floor
Red Rectangle = Building Footprint
Green Rectangle = Lift Shaft

Important points that I am not certain about some basic layout aspects:
1) Are the floor layouts exactly the same in the two buildings?
2) Is there indeed a smaller pool off the side of the SFP between the SFP and Lift Shaft?

Note that the Dry Well Cap has been removed from Reactor 4 but (I believe) would still be in place on Reactor 3. I use it as a relative gauge of the size of where the footprint of the Dry Well Plug would have to be on the floor. Thanks.

ADDENDUM:

I add the "Oyster Creek" Reactor Diagram referenced in several earlier posts.

http://i306.photobucket.com/albums/nn270/tcups/Oyster-Creek-reactor.gif

1. BWR layouts out the refuel floors are pretty much standard. The confuiguration you describe is the same as the BWR where I worked.
2. Yes. The cask Pool is an area for loading fuel casks for transfer to reprocessing plants, other storage areas (Fukushima has a common fuel pool storage area), or to other storage such as the dry fuel storage facilities at many US plants. The pool opposite the fuel pool across the containment plug is used to store the reactor vessel head under water when it is open for refueling.

 

[|Fred]

Yes. A steam explosion can occur without air being present:
http://en.wikipedia.org/wiki/Steam_explosion"

And at high enough temperature (>1700 Celsius) zirconium also reacts explosively with steam producing hydrogen without the need for air.
Zr + 2H2O -> ZrO2 + 2H2

Of course once hydrogen escapes the containment it can also explode in air.

Picture from the R3 blasht show an orange reaction on the south wall of reactor 3 above the fuel pool, this suggest I think that the ignition of the blast toke place there and likely involved something beside Hidrogene. does Zr02 burn orange ?

 

[Bez999]

I wonder if anybody can answer the question why the control rod arrangements appear to be such a complicated construction with individual drives for each rod (as it would appear to be from the diagrams I have seen). Am I correct in assuming that the control rods are pushed up hydraulically, and if so, isn't that a tricky arrangement when power is lost, or hydraulics damaged, such as in an earthquake. Also, how does one know whether the control rods have been engaged completely?
Wouldn't a design be more logical where the entire core is pushed up from a grid of control rods that is fixed lower in the vessel, i.e. where loss of power would result in stopping the reaction as a result of gravity?
Is it perhaps the case that control rods are adjusted individually during normal operation, i.e. that they may be inserted at individually different levels, and if so, what type of instrumentation is available to monitor that?

 

[Gilles]

Picture from the R3 blasht show an orange reaction on the south wall of reactor 3 above the fuel pool, this suggest I think that the ignition of the blast toke place there and likely involved something beside Hidrogene. does Zr02 burn orange ?

actually Na emits a well-known orange resonance line, you can get it with a small crystal of salt in a flame - that may just be the salt contained in some droplets of sea water that gave this color to the explosion.

 

[NUCENG]

We are hearing of meltdowns, breaches of the reactors and flooded containment and cracked sides and this and that. If any or all of this is true, the reactor level could be determined by the leaks in the vessel structure and the containment structure. We know that the water they are pumping in is ending up in the turbine room structures so we know it is getting there some way and some how.

Unfortunately inside those damage buildings is a big concrete primary containment shaped like a light bulb with socket end up. This structure prevents direct vision of the reactor vessel so if the vessel or piping were damaged we couldn't see it. The water level of a BWR is measured indirectly by differential pressure and depends on keeping a reference leg full. A partially full reference leg fives a false high level reading. American plants have keep-fill systems. Don't know about Japan.

It might be possible to see a leak from containment damage, but that is probably very high radiation around there. It also could be easy to miss a leak if it is only releasing gas. The primary containmentcan be accessed by an air lock or an equipment hatch, but with rad levels so high would be useless as it would be suicide.

Right now the strategy is pumping water into cool fuel and arrest melting. We know fuel has been damaged. We know only cooling can stabilize it. Until then specific water levels are items of curiosity, not necessity. Containment pressure and temperatures are much more important. If containment pressure is different from atmospheriic pressure it is doing its job. Even if containment is leaking it would be far worse if the containment is lost.

And the fuel in the fuel pools has NO containment with the roof blown off. Even if pumping water into those pools is spilling through leaks and contaminating the land and sea close to the plant I would continue doing this to avoid the results of a fuel pool fire, if that hasn't already happened.

 

[NUCENG]

http://www.scribd.com/doc/50775386/Areva-Fukushima-la-licence-d-exportation-de-MOX

Notice "Reload fuel for Reactor 1,2,3,4,5".
~35 tons of Uranium dioxide.

Will it be possible to research whether the plan was to reload #4 with MOX?

Only Fukushima Daichi Unit #3 was announced for MOX.

 

[|Fred]

Nuceng, the containment has been filled with water.

 

[NUCENG]

what other scenarios could explain 18sv/hr in the secondary containment besides the core melting through the floor of the primary? Does this imply the core has gone critical, or not necessarily so?

Criticality would be evidence by neutrons. No statement of such from on scene. Corium is capable of melting without being critical. Sort of like a self-heating steel slag. Again, that would be interacting with a lot of other materials which would add their own signature to the radiation.

 

[NUCENG]

Has the subject of Sodium Pentaborate been brought up?

http://www.ceradyneboron.com/products/nuclear-power/chemistry/enriched-sodium-pentaborate/

Was Fukushima Daiichi equipped with such systems and if not why?

BWR plants have Standby Liquid Control Systems (SBLC or SLC) to inject boron into a reactor if it is not shutdown by control rods the Anticipated Transient Without SCRAM or ATWS. In US Plants using Emergency Operating Procedures the system is also used when core damage begins based on readiation readings. Don't know if Japan uses the same procedures, but they would have something similar. Once fuel is damaged you no longer have confidence in the core geometry that keeps reactor subcritical with control rods so you inject Boron to help control reactivity. Reportedly operators at Fukushima have been spraying and injecting boron since early in the accident.

 

[PietKuip]

Criticality would be evidence by neutrons. No statement of such from on scene.

They are not looking for such evidence. The IAEA seems to be guessing in the same way as we: http://www.bloomberg.com/news/2011-03-30/record-high-levels-of-radiation-found-in-sea-near-crippled-nuclear-reactor.html

Tepco is just feeding the IAEA with the same reams of numbers they give us. But one needs to get some non-routine measerents, some firm data about whether the fuel is (intermittently) critical or not. If decent neutron detectors are not available, there are low-tech methods, like dangling wedding bands in suspected places: the gold will become radioactive if there is a neutron flux. Or one could use the manganese in ordinary batteries.

This is not difficult. I cannot understand how the key information about possible chain reactions is still a question more than two weeks after the accident.