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.

 

[NUCENG]

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?

Control rods are used individually in BWRs to adjust core reactivity as fuel is fissioned. It allows operators to shape the power density in a core to use as much of the loaded uranium as possible. If unlatched during operation a control rod will drift into the core due to reactor pressure.

PWRs use banked rod controls but also use the solution of boron in the water to adjust reactivity.

BWRs don't used boron during operation because the boiling water might result in plating out boron.

 

[jensjakob]

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.

Money... Liabilities... We are talking extreme big business here, not just Fukushima or TEPCO are on stake - but the whole NPP industry.

I am not a doom-sayer or anti- nor pro-nuke, just working for the factual truth.

 

[NUCENG]

Nuceng, the containment has been filled with water.

I thought so, and even said so here on the forum but Astronuc indicated that he hadn't seen that report. I went back and couldn't find a clear statement of that from TEPCO. Did you find a source confirming they did containment flooding?

 

[NUCENG]

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.

I can only guess with the rest of you. Neutron rediation is a little more difficult to detect because it isn't a charged ion. But plants have detectors. With all the IAEA, UN, and foreign support on the ground it would take more than TEPCO to hush that up.

 

[artax]

some interesting stuff here with analysis of one of the heli flyover videos by a Japanes Prof.
The 'GOOD NEWS' stated towards the end of this is just embarassing and SO Japanese!



It seems to me they need to build a new sea wall around the discharge to sea outlet pipes, leaving a big isolated lake of sea water, and then simply set up massive 5 inch or so pipes supported by the turbine building roof to all the 4 reactors, then just circulate the water so it's not going out to sea.
Probably though the sea wall construction would be a 3 month massive civil engineering project!

 

[|Fred]

I thought so, and even said so here on the forum but Astronuc indicated that he hadn't seen that report. I went back and couldn't find a clear statement of that from TEPCO. Did you find a source confirming they did containment flooding?

I know ;à)
I think I did , may be you missed my post ... It's a bit hard to follow since the document published by the JAIF, language is pretty missleading as It seems toi me that they states present situation rather that timelined action

in unit 1 the pressure of the core was dropped from 7MPa to 0.8MPa within 12 hours of the accident as a consequence (i think) the pressure of the containment raised from 0.1MPa to 0.8MPa (this lead to leak from the top of the containment vessel) and likely the first blash.

We know that on the 15th http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300171089P.pdf Sea water injection to Containment Vessel unit 1 was "Done"

some time betwen the the 16th and the 17th it was decided to inject water on unit 3
(continuing)(to be decided)(to be decided)
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300273535P.pdf
(continuing)(to be decided)(continuing)
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300322727P.pdf


If I'm to trust the jaif document with a grain of interpretation

1 and 3 containment are filled with water not 2.. unit 2 is the only one with a secondary containment structure almost fully standing..co incidence?

 

[artax]

There's a good video on youtube called inside the sarcophagous. They were pretty concerned about the contents reforming a shape that was 'critical' at chernobyl months after the accident, and went inside to investigate exactly where all the fuel had gone. When they finally saw inside the core it was empty!

 

[AntonL]

I hope I am not double posting -The same photos with a bit more detail

Unit 2 also had quite a blast in the basement area - look at the roof of the 1 story structure on North side of the reactor building (left hand side)

Tepco always reported explosion by Torus with possible Torus damage, but it was quite a bang judging from the photo and No.2 has the highest contaminated water in basement.

(AP Photo/AIR PHOTO SERVICE) MANDATORY CREDIT
Unit 3 & 4 in next post

 

[AntonL]

and here Units 3 & 4 (AP Photo/AIR PHOTO SERVICE) MANDATORY CREDIT

 

[artax]

There's a lot of debris on that 1 storey building, so the damage is likely to be from the number 1 blast?
However there is a strange line down one side of unit 2, the side with the agping hole venting steam, anyone else noticed that?

 

[AntonL]

Questions and comment from within Japan
be interesting to get hold of GE report being referenced

When reading the below remember that the reactors had 1 hour precooling and rest heat generation would have been reduced to [STRIKE]50 to 65%[/STRIKE] 30% of the values so the times shown below could be tripled or more (1 hour cooling) (Edit: I must check exact times and revise later)

Primary total loss of power, safety regulations intended to make the U.S. 30 years ago.

16 hours 39 minutes 31 March 2011
Print

　For the same type of reactor Fukushima Daiichi Nuclear Power Station TEPCO, 1981 - U.S. research institutions in 1982, conducted a simulation of all power is lost, report to the U.S. Nuclear Regulatory Commission (NRC) submitted had been found. Exposure of the calculated fuel, hydrogen generation, and melt the fuel scenario similar to the course of this incident. Although the use of NRC safety regulations which, as Japan did not expect such as early recovery and power lines.

　This simulation is modeled on a nuclear reactor Brownsferry, conducted by the U.S. Oak Ridge National Laboratory. The output of approximately 110 million kilowatts, Fukushima Daiichi nuclear power plant - a General Electric as the No. 5 (GE) of boiling water mark "I" is the furnace.

　Fukushima Daiichi nuclear power plant like this, "the loss of emergency diesel generator and an external AC power, battery operated emergency" and assume that, the battery time available, the health of an emergency cooling system calculated separately and in some cases.

　If available, 4 hours battery, 5 hours after the start of a power failure "exposed" fuel, after 5.5 hours, "the fuel reached at 485, may also occur Hydrogen", after six hours, "the molten fuel (meltdown) start ", after seven hours," the lower the pressure vessel is damaged, "eight hours after" damage containment "that the results came out.

　In a separate calculation of the institute was available for 6 hours, 8 hours after exposure "fuel", 10 hours after the "start meltdown", 13 hours after "damage containment" was.

　Meanwhile, Fukushima Daiichi, the loss of power from an external source during earthquakes, but switched to diesel generators for emergency stops and the generator about an hour after the tsunami, the power supply as Battery DC emergency to. Conditions were simulated in the same condition as at this time.

　8 hour battery is available, unlike the simulation, but is almost the same sequence of events occurred. Also, the calculation is adopted, the Fukushima Daiichi nuclear power plant containment may already have lost their sanity.

　GE's Sato Akira consultant nuclear has been involved for years in maintaining boiling water affiliated with the "simulation is good enough at this time. Whether that is handed down the findings of these past power company just do not know "he said.

　Meanwhile, in Japan itself, assuming all power is lost, has been neglected.

　Nuclear Safety Commission in 1990, when the design review guidelines for determining the safety of nuclear power, "the long-term loss of all AC power source, power lines or recovery (again) because the facility is expected to AC power for emergency repairs There is no need to consider, "the idea that. But in reality, the earthquake and tsunami unusable in an emergency diesel generator power line also.

　Matsuura Shiyouzi Chairman Department of Nuclear Safety Research Association (Director, NSC yuan) is "a bad situation and that everything was good to think about unwritten. Meteorite (Inseki) and hit, and anything ask, can cope with dry, it's impossible, "he said. (Ichiro Matsuo, 磨 Komiyama Makoto)

Asahi Top Com

 

[Astronuc]

The human side of this event:

Workers Give Glimpse of Japan’s Nuclear Crisis
http://www.nytimes.com/2011/03/31/world/asia/31workers.html

A manager from the Tokyo Electric Power Company explained how the Fukushima Daiichi nuclear plant had been slammed by a mammoth tsunami and rocked by hydrogen explosions and had become highly radioactive. Some workers wept.
. . . .
Hundreds of firefighters, Self-Defense Forces and workers from Tokyo Electric Power convened at the sports training center, arguing long and loudly about how best to restore cooling systems and prevent nuclear fuel from overheating. Complicating matters, a lack of phone service meant that they had little input from upper management.

“There were so many ideas, the meeting turned into a panic,” said one longtime Tokyo Electric veteran present that day. He made the comments in an interview with The New York Times, one of several interviews that provided a rare glimpse of the crisis as the company’s workers experienced it. “There were serious arguments between the various sections about whether to go, how to use electrical lines, which facilities to use and so on.”
. . . .
In the interviews and in some e-mail and published blog items, several line workers expressed frustration at the slow pace of the recovery efforts, sometimes conflicting orders from their bosses and unavoidable hurdles like damaged roads. In many cases, the line workers want the public to know that they feel remorse for the nuclear crisis, but also that they are trying their best to fix it.

“My town is gone,” wrote a worker named Emiko Ueno, in an email obtained by The Times. “My parents are still missing. I still cannot get in the area because of the evacuation order. I still have to work in such a mental state. This is my limit.”
. . . .

Company management still wants to keep tight control on the flow of information from the company to the public (and government).

On March 14, workers were told that the assignment was dangerous and that they could opt out. Few did. Many workers felt duty-bound to go to Fukushima, particularly those with families who were directly affected by the earthquake and tsunami.

As was mentioned much of the infrastructure in the area was knocked out.

The local roads were slower going because parts of some streets had literally disappeared.

 

[artax]

That really brings it home doesn't it.

don't know if these are of any interest

http://photos.oregonlive.com/4450/gallery/fukushima_aerials/index.html

well this one is:-

http://photos.oregonlive.com/oregonian/2011/03/aerial_9.html

 

[NUCENG]

I know ;à)
I think I did , may be you missed my post ... It's a bit hard to follow since the document published by the JAIF, language is pretty missleading as It seems toi me that they states present situation rather that timelined action

in unit 1 the pressure of the core was dropped from 7MPa to 0.8MPa within 12 hours of the accident as a consequence (i think) the pressure of the containment raised from 0.1MPa to 0.8MPa (this lead to leak from the top of the containment vessel) and likely the first blash.

We know that on the 15th http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300171089P.pdf Sea water injection to Containment Vessel unit 1 was "Done"

some time betwen the the 16th and the 17th it was decided to inject water on unit 3
(continuing)(to be decided)(to be decided)
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300273535P.pdf
(continuing)(to be decided)(continuing)
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1300322727P.pdf


If I'm to trust the jaif document with a grain of interpretation

1 and 3 containment are filled with water not 2.. unit 2 is the only one with a secondary containment structure almost fully standing..co incidence?

That's it! I remember the words "containment vessel" were in some press release, and interpreted that as containment flood. Thanks.

During initial stages after loss of cooling they would have controlled pressure by using safety relief valves to vent steam from the reactor vessel to the suppression pool where the steam would be quenched and the suppression pool would heat up. RCIC is a steam/battery supported system and would be used to add water to the vessel. Once the battery was exhausted, trouble begins. They still would have vented steam to the suppression pool until it reaced its temperature limit or began to boil. It would no longer be able to condense steam if boiling occurred and the drywell and contaiment pressure would rise. Before that reached design limits, operators would want to vent pressure to prevent major failure of the containment. They would write off the core to protect the containment and the public. SRVs would have moved hydrogen to the airspace of the torus/suppression pool. Venting would then release this into systems outside the primary designed to filter and release through the stack. That would increase the dispersion of radioactivity compared to a near ground release. US BWRs have a hardened vent capable of handling these pressures. If indeed the containment system reached 0.8 MPa it may have been over its design pressure and it may have leaked past the contaiment cap onto the refuel floor. These two cases may have some impact on where detonations ocurred.

There are blowout panels in the reactor building sides on the refuel floor. That may explain the two openings in the Unit 2 siding. They are primarily designed to vent steam line breaks, not hydrogen explosions.

 

[|Fred]

I remember reading from Jaif or Nisa (I unfortunately can not find the link again), the legislative paper regulating exceptional procedures in case of nuclear disaster and the raise on legal maximum radiation dose allow worker to conduct operation.
I clearly recall that although limit is raised from 20 or 50mSv/y to above 200, work commitment has to be voluntary.

Does it ring bells to similar legislation in the US ?


edit:
Sea water injection to core =>Done
Sea water injection to Containment Vessel =>Done
there are two lines implying they are two different things , do we agree that the "drywell" has been flood in 1 and 3 ?