Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[shogun338]

Japan’s Reactors Still ‘Not Stable,’ U.S. Regulator Says ---The situation is “not stable” and will remain so until “that kind of situation would be handled in a predictable manner,” he said.

Mr. Jaczko also offered a new theory about the cause of the explosions that destroyed the secondary containment structures of several of the reactors. The prevailing theory has been that hydrogen gas was created when the reactor cores overheated and filled with steam instead of water; the steam reacts with the metal, which turns into a powder and then gives off hydrogen.

The Tokyo Electric Power Company, which operates the nuclear plant, intended to vent the excess steam as well as the hydrogen outside of the plant, but experts have suggested that when operators tried this, the vents ruptured, allowing the hydrogen to enter the secondary containments.

But Mr. Jaczko said Tuesday that the explosions in the secondary containments might have been caused by hydrogen created in the spent-fuel pools within those containments.

If true, that would mean that the introduction of hardened vents at reactors at nuclear plants in the United States — cited as an improvement that would prevent such an explosion from happening — would not in fact make any difference. Wow! It sounds like there just guessing like a lot of us here . Well Unit 4 exploded sky high and was in cold shutdown so I think his spent fuel pool guess might be right :) The way Unit 3 exploded I think there was more to it than just the spent fuel pool . http://www.nytimes.com/2011/04/13/world/asia/13safety.html?_r=1

 

[NUCENG]

Professor Magdi Ragheb provides the following analysis :



Put together with http://www.asahi.com/english/TKY201104060126.html , Mr Ragheb's figure is probably a closer description for Fukushima Daini (No 2), where the diesel are inside the reactor building, rather than for Fukushima Daiichi (No 1), although none of them are ABWRs.

Issues I have with Prof Ragheb's paper:

1. Implies that RHR only required for a few days. If so there should be no need to cool fuel pools.
2. Uses ABWR to conclude diesels were on upper floor. Japanese reports indicate diesels were in TB basement.
3. Implies that seawater injection was initially used to refill the suppression pool. Initially was injected to RPV after depressurization to make up for boil-off and depressurization via SRVs.
4. Figure 19 shows fuel pool not Figure 20 as indicated in Captions.

It is interesting, but not perfect.

 

[Cire]

But Mr. Jaczko said Tuesday that the explosions in the secondary containments might have been caused by hydrogen created in the spent-fuel pools within those containments.

If true, that would mean that the introduction of hardened vents at reactors at nuclear plants in the United States — cited as an improvement that would prevent such an explosion from happening — would not in fact make any difference.

The hardened vents would make a difference when venting the drywell or RPV. It just wouldn't have an effect on the spent pools.

I suspect you'll see additional steps taken to detect and mitigate hydrogen build up in tertiary containment areas real soon. The mentality previous to fukushima was to never allow any radiation to escape. I suspect that will change to never allow any radiation to escape unless the result of continued containment is your facility explodes.

Venting should be through scrubbers, re-combiners (PARS), and into external containment facilities. I'd like to see the PARS and scrubbers external to the containment since the PARS can reach very high temperatures.

 

[AntonL]

A very nice powerpoint (.ppsx) presentation

Disaster at Fukushima Daiichi: How Did It Happen?
DOWNLOAD: http://www.ucsusa.org/assets/documents/nuclear_power/Fukushima-Tragedy.ppsx"
The boiling water reactors at the Fukushima Daiichi nuclear power plant on the northeast
coast of Japan are equipped with an elaborate set of systems designed to ensure that
cooling of the fuel in the reactor core and spent fuel pool is maintained in the event of an
accident or shutdown. Tragically, these systems proved unequal to the damage inflicted by
the earthquake and tsunami that struck Japan on March 11, 2011.

In this Powerpoint slideshow presentation, David Lochbaum, Director of the UCS Nuclear
Safety Project, explains in detail how the Fukushima reactors worked under normal
conditions, and then describes how the events of March 11 crippled their safety systems,
resulting in extensive fuel damage and a "tragedy of unprecedented scale."

 

[AntonL]

NHK reports http://www3.nhk.or.jp/daily/english/13_05.html"

 

[SredniVashtar]

NHK reports http://www3.nhk.or.jp/daily/english/13_05.html"

"The ministry says the amount found is extremely low and will not have a negative health impact even if a person ingested one kilogram of the contaminated soil."

Now, that would be a bizarre way to take strontium, would it not?
Beside, eating a kg of dirt could have a definite negative health impact. :-)

On a more serious note, I wonder what a kg of soil mean: did they scrape the surface, or did they dig in depth? Are there internationally shared protocols on how to proceed to sample the soil?

 

[rasherz]

"The science ministry says radiation levels in seawater off the coast of Fukushima Prefecture are the highest since it began monitoring them about 3 weeks ago." NHK news

Could there be another leak from the recent aftershocks?

 

[Krikkosnack]

I want to know where all the Strontium is.

Are TEPCO only testing for certain isotopes?

GOOOOOOOOOOODDD MOOOOORRNING TEPCO...
they answer to you...
Japan's science ministry says small amounts of radioactive strontium have been detected in soil and plants outside the 30-kilometer zone around the Fukushima plant where the government has advised people to stay indoors...It found 3.3 to 32 becquerels of strontium 90 per kilogram of soil in samples taken from 3 locations in Namie Town and Iitate Village, 30 kilometers from the plant.An extremely small amount of strontium was also found in plants taken from Motomiya City, Ono Town and Otama and Nishigo Villages. The areas are 40 to 80 kilometers from the Fukushima plant.

 

[AtomicWombat]

Long-term, for future designs - Assuming catastrophic loss of coolant/cooling ability, is there any way of designing a reactor to melt-safe?

Using a http://en.wikipedia.org/wiki/Thorium_fission" has the potential to bypass many of the disadvantages of uranium and MOX based fuels; in particular thorium is more abundant; has superior physical, chemical properties and even fuel properties (neutron cross section); produces far smaller quantaties of the transuranic waste products (a reduced radioactive waste problem); and is much harder to incorporate into a nuclear weapons fuel cycle. This last reason may be why it has been neglected as a nuclear fuel so far.

Currently only India appears to have an active research program in Thorium reactors.

Natural thorium has only trace amounts of spontaneously fissionable material and has to be enriched with some fissile material or provided with a neutron source to sustain a reaction. This second approach is the basis for the use of an http://en.wikipedia.org/wiki/Energy_amplifier#Principle_and_feasibility" Once the accelerator goes off (e.g. due to loss of power), fission stops.

I am unsure about the decay heat associated with thorium fusion and whether it could be managed passively.

I do wonder though, if thorium was widely used in nuclear reactors with uranium in an ever smaller niche, would the nuclear industry have such a PR problem?

 

[Krikkosnack]

@Krikkosnack and PietKuip

Alpha radiation - positive charged helium nucleus traveling at high speed
Beta Radiation - negative charged electron traveling at high speed
Gamma Radiation - electromagnetic waves

http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html

from the link above...
Beta particles are just electrons from the nucleus, the term "beta particle" being an historical term used in the early description of radioactivity. The high energy electrons have greater range of penetration than alpha particles, but still much less than gamma rays. The radiation hazard from betas is greatest if they are ingested.

so is it possible to say that beta particle derived from plutonium and uranium are indistinguish from normal "electricity in the air"? and therefore unmeasurable?

 

[AtomicWombat]

The possibility to re-inject the contaminated water should also be considered as the amount of waste water can be reduced.

The problem is that any equipment used to handle the water (pumps, pipes etc) will rapidly become highly radioactive especially if the water is reinjected.

The radioactive contaminants must be removed and stored prior to reinjecting the water. It's a very tricky problem.

 

[jpquantin]

Does anyone has information about the evacuation criteria used in Japan ??

According to this http://www.mext.go.jp/english/topics/__icsFiles/afieldfile/2011/03/18/1303717_01_1.pdf" from NISA, the maximal "normally accepted" annual dose coming from the background would be 2,800 (average natural dose) + 1,000 (max public dose) = 3,800 microSieverts per year.

Taken by day, this is 10.42 microSievert, and for an 8 hours exposure outside this would be 1.31 microSivert per hour max.

At this rate, Fukushima city should be evacuated, as well as many other cities in a radius of 60 km, north-east from the plant (latest readings http://www.mext.go.jp/component/english/__icsFiles/afieldfile/2011/04/13/1304852_04121900_1.pdf" .

It seems they apply a much higher max dose rate per year, or other criterias ?

 

[Borek]

so is it possible to say that beta particle derived from plutonium and uranium are indistinguish from normal "electricity in the air"? and therefore unmeasurable?

No idea what you mean. There is no such thing as "electricity in the air", I guess what you are aiming at is the fact that electrons - bound to molecules - are abundant in the air. However, electrons that form beta radiation are not bound, they have high kinetic energy, so they behave differently, which means they can be detected, just using different detectors.

 

[jpquantin]

Found this situation update http://www.cea.fr/le_cea/crise_nucleaire_au_japon_questions_reponses-54623" (Apr. 12 1:30PM GMT).

(Google translated)
[...]
TEPCO continues the injection of nitrogen for inerting the containment despite the finding of a steady pressure of 2 bar, while initial estimates predicted a gradual increase up to 2.5 times the atmospheric pressure during the operation, leaving to assume the existence of a leak.
[...]
No significant change in dose rate since the previous update on the situation. On 10 April, remotely controlled construction equipments began to be used on site to remove the rubble. TEPCO has also used a remotely controlled helicopter to measure the dose rate close to the reactors 1-4. This rate was several hundred mSv per hour (mSv / h) / between reactors 2 and 3, and west of building 3.
[...]

 

[Krikkosnack]

Does anyone has information about the evacuation criteria used in Japan ??

According to this http://www.mext.go.jp/english/topics/__icsFiles/afieldfile/2011/03/18/1303717_01_1.pdf" from NISA, the maximal "normally accepted" annual dose coming from the background would be 2,800 (average natural dose) + 1,000 (max public dose) = 3,800 microSieverts per year.

mumble ... mumble
3.000 microSieverts per year?
http://www.meti.go.jp/english/earthquake/nuclear/pdf/20110412_radioactivity.pdf

http://energheia.bambooz.info/index.php?option=com_content&view=article&id=132%3Aradiation-dosage-chart&catid=51%3Acharts&Itemid=82&lang=it

 

[TCups]

Wow. Nice work.

Where did that video come from? I've looked at a lot of stuff in the last month, and I'm quite sure I haven't seen that.
(Even if I had, I doubt I would've caught that, without your pointing it out.)

So, that's superb confirmation of TCups' theory from a week or two back, right?
(At least, the part about the FHM 3 being blown sky-high, flipping over once or twice, and plummeting onto the North side of the wreckage of R3.)

Do I have that right?

Way to go.

If the "ballistic FHM" observation is correct (as I have believed for some time), then, more important, are the conclusions that must follow:

1) by the principle of differential pressure which would be required to lift the crane vertically, the primary force came upward, from the spent fuel pool and the propellant was vaporized water -- steam -- rather than hydrogen gas in the upper portion of the building.

2) SFP3 is the most likely source of the scattered fuel rods

3) there had to be multiple components to the blast at Bldg 3 -- at least two, more likely 3

4) the evidence that the concrete plug over the primary containment for RPV3 is largely intact and probably still in place is strongly reinforced.

Was the last of the three booms on the original video of the explosion of Unit 3 the sound of the crash or something else?

How about it, M. Bachmeier? What have you been able to tease out of the soundtrack analysis? Is it real or is it Memorex?

 

[AtomicWombat]

- drywell radiation sensor in Unit 1 seems to be gone, after topping 100 Sv/h and then falling back at ~70. Is 100 Sv/h the maximum level it can measure? Was it fried by higher radiation levels? And is there any connection between this failure, higher drywell radiation and rising core pressure?

Some related questions.

Where are the drywell and torus radiation sensors? Would they be robust to the what has occurred so far? Can the radiation measurements be relied upon?

It has also occurred to me that the drywell is now flooded, so to some extent radiation measurements there will be attenuated by the water. Nitrogen bubbling - assuming this occurred from below - would have temporarily reduced this attenuation by decreasing the path length through water. This off course assumes that the water is not the greatest source of radiation in the dry well.

 

[AtomicWombat]

I know they also have more important things at hand than my need for information at the moment but they are as sparse with words as I am. Still, I prefer that they be accurate in their information than just provide me with volume of it.

It concerns me that the inability to approach many areas of the facilities will lessen the information available to reconstruct events in detail and lower the value of lessons learned. As bad as this is I want to see the maximum value of wisdom extracted from it.

There is a bigger issue at stake here. TEPCO insist on managing this issue in-house and the limited information is just one symptom of this. If as complete as possible picture of the situation could be published widely and innovative solutions invited, I'm sure some truly clever suggestions would emerge that may well resolve this crisis much more rapidly, with much less financial and human cost.

 

[htf]

There is something I don't understand. Here is the course of actions after the station blackout (I don't know how trustable the author is).

http://www.yomiuri.co.jp/dy/national/T110411004567.htm
http://www.yomiuri.co.jp/dy/national/T110412006319.htm

There is confusing information regarding the emergency valve. One report says that TEPCO was not able to open the valves. Eventually the government ordered TEPCO to open them. The other report says that TEPCO was reluctant to do so, because they were afraid of the consequences (contamination of the plant or worse and hence financial loss for the company). Therefore they were looking for a more favourable solution thereby loosing valuable time.

I found some documents that say that a GE MARK-I reactor has a emergency valve that will open automatically but a simulation (performed in the 1980s) of a station blackout showed that it would be beneficial to open it manually in the early stages of such an accident.

Can anybody explain the story with the valves?

 

[jpquantin]

mumble ... mumble
3.000 microSieverts per year?
http://www.meti.go.jp/english/earthquake/nuclear/pdf/20110412_radioactivity.pdf

http://energheia.bambooz.info/index.php?option=com_content&view=article&id=132%3Aradiation-dosage-chart&catid=51%3Acharts&Itemid=82&lang=it

Later found http://energy.gov/news/documents/040711__AMS_Data_April_7__v3.pptx" .

Here they say the EPA recommendation is to take "protective actions" above 1000 mRem over 4 days. As 1 mRem = 10 microSieverts, this is 10 000 microSieverts over 4 days.

Which is, for 24 hours exposure this time (no action taken) a level of 104.1 microSieverts per hour.

Another manner to find a limit is through estimated annual dose. Here if we take max annual exposure of workers in nuclear industry, this is 50 000 microS per year, which is an average 5.71 microSieverts per hour (again 24 hours a day), which is well below the EPA protective actions figure.

Still dit not find info from Japan regulation about "protective actions" over that (in English).

 

[jpquantin]

It has also occurred to me that the drywell is now flooded, so to some extent radiation measurements there will be attenuated by the water.

How can you say that drywell in reactor 1 is flooded ? If so, wouldn't pressure in the suppression chamber be higher than drywell one, as they communicate ? (sand filter) (and assuming reading are trustable).

 

[AntonL]

Was the last of the three booms on the original video of the explosion of Unit 3 the sound of the crash or something else?

In my opinion all three booms, sampled, processed, synthesized, electronic mix, etc to give bollywood effect, probably the tv network sent it out in surround sound for added effect.

 

[AtomicWombat]

is there any explanation for the explosion and the fires in #4, that works *without* massive fuel damage?
in this document: http://www.vgb.org/vgbmultimedia/News/Fukushimav15VGB.pdf the core damage of #1 is estimated to 60-80%, derived from the production of hydrogen necessary to blow away the top of the building.
#4 looks even worse...
in the same document, the time for dry-out of #4 SFP is estimated 10 days. the explosion was much earlier.
if that explosion was a hydrogen explosion (what else?), then it should be a save assumption, that the pool has a leak.
if the pool has a leak, then every new (even small) quake could make it larger.
if it is possible to get the fuel out there, i would put all my efforts in it, if i were tepco.

i would really appreciate a rebuttal of my 'analysis'.

I don't know how much zirconium is present in the SFP (or the cores), but I can say this. The estimated mass of hydrogen for a 4% lower flammability limit in 8000 m^3 is WRONG. The authors of that document have either made a simple error or are ignorant of basic physical chemistry. They state that 4% H2 in 8000m^3 corrsponds to 320 kg H2. They've clearly mixed units. Whilst http://en.wikipedia.org/wiki/Air#Density_and_mass" is only about 0.09 kg/m^3. I.e. 0.09 kg of H2 at STP will occupy the same volume as 1.2 kg air.

So to reach the 4% lower flammability limit in 8000 m^3 requires only 0.04*8000*0.09 ~ 29 kg of hydrogen. So a much smaller amount of zirconium oxidation is required (about 660 kg). I suspect this is a small fraction of the total zirconium in the SFP.

 

[AtomicWombat]

Failure pressure and operating pressure are two completely different things. 10x operating pressure would not fail the RPV. It would fail the support plumbing and interconnects but not the pressure vessel.

For example, the Trieste, the deepest diving vessel ever made had a 5" thick steel pressure vessel. It was "rated" for 110MPA! That's ~16,000 PSI. That's the rated pressure, not the failure pressure. The RPV's in the plant are over an inch thicker then this example.

Re: Comparison of Trieste and RPV, wall thickness: Does this not require the dimension of the vessel ? a 10 meter vessel will require thicker walls than a 1 meter vessel ?

This is well known in pressure vessel design. The original calclation was to illustrate the violence of explosion.

In no way did the hydrogen explosion overpressure the reactor vessel, or for that matter the steam pressure inside overpressure the vessel.

Neither you nor I know that. There are reports of a large crack in its side.

If corium breached the bottom of a pressurized vessel the water vapor and gasses and whatever else wanted too would be ejected at near supersonic velocities producing a massive impulse on the RPV. If the RPV had no water or vapor and was depressurized when the melt occurred, then that would be a very different scenario. I haven't seen anyone argue the RPV was dry and unpressurized.

I had considered this "rocket effect" for the cause of this explosion, but RPV number 3 was http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/plot-un3-full.png" prior to the explosion.

 

[AtomicWombat]

I finally found ( I think) something identifiable from the fuel handling machine of unit 3, so now would like a second opinion.

The image of the object (which I think is the upper platform of the fhm) is a frame from the video at:
http://www.youtube.com/user/modchannel#p/a/u/2/gWzPU5fgThA

I have attached the captured frame in somewhat higher definition, as well as the Aug 2010 photo confirmed to be the FHM of unit 3.

Wow, excellent work. I'm still trying to work out how the parts correspond, but I'm amazed how similar the colours are.

 

[AtomicWombat]

O dear i found an instant counterexample.. a balloon. The skin gets thinner as I blow it up. But I suspect steel is not like rubber...

So: am i right in respect to steel ? a 10 meter spherical steel vessel requires a thicker wall than a 1 meter spherical steel vessel to hold a given pressure ?

I suspect it has to do with yield points and ductile flow and such

See:
http://en.wikipedia.org/wiki/Pressure_vessel#Scaling_of_stress_in_walls_of_vessel"

"The normal (tensile) stress in the walls of the container is proportional to the pressure and radius of the vessel and inversely proportional to the thickness of the walls."

In simple terms, for the same pressure, wall thickess is proportional to radius. Doubling pressure requires doubling wall thickness or halving radius of vessel.

 

[bytepirate]

I don't know how much zirconium is present in the SFP (or the cores), but I can say this. The estimated mass of hydrogen for a 4% lower flammability limit in 8000 m^3 is WRONG. The authors of that document have either made a simple error or are ignorant of basic physical chemistry. They state that 4% H2 in 8000m^3 corrsponds to 320 kg H2. They've clearly mixed units. Whilst http://en.wikipedia.org/wiki/Air#Density_and_mass" is only about 0.09 kg/m^3. I.e. 0.09 kg of H2 at STP will occupy the same volume as 1.2 kg air.

So to reach the 4% lower flammability limit in 8000 m^3 requires only 0.04*8000*0.09 ~ 29 kg of hydrogen. So a much smaller amount of zirconium oxidation is required (about 660 kg). I suspect this is a small fraction of the total zirconium in the SFP.

good point. but as 320 is 4% of 8000, i assume its just a 'typo' (kg for m³) and the rest of their calculations is not affected.

EDIT: on pages 41/42 they contradict themselves...

 

[AtomicWombat]

The 1986 disaster at the Chernobyl power plant in Ukraine spewed debris as high as 9 kilometers into the air and released radiation 200 times the volume of the combined bombings of Hiroshima and Nagasaki in 1945, according to a 2006 report commissioned by Europe’s Green Party. http://www.bloomberg.com/news/2011-04-12/taiwan-halts-plans-to-build-atomic-reactors-after-japan-crisis.html

Hiroshima and Nagasaki were "airbursts". It probably sound trite, but airbursts are remarkable clean, in that local fallout is realatively small, often allowing people to immediately rebuild and live at the site immediately after the blast. Most radiation damage is from the initial exposure to the blast.

Surface burst nuclear weapons will produce much higher levels of local fallout.

For this reason and others the comparison of nuclear blasts and reactor accidents is misleading.

http://www.fas.org/nuke/intro/nuke/effects.htm"

 

[NUCENG]

Hiroshima and Nagasaki were "airbursts". It probably sound trite, but airbursts are remarkable clean, in that local fallout is realatively small, often allowing people to immediately rebuild and live at the site immediately after the blast. Most radiation damage is from the initial exposure to the blast.

Surface burst nuclear weapons will produce much higher levels of local fallout.

For this reason and others the comparison of nuclear blasts and reactor accidents is misleading.

http://www.fas.org/nuke/intro/nuke/effects.htm"

I've heard that the first nuclear weapons were crude and overly designed to be sure they reached a critical mass. They were not as efficient as modern weapons. There must have been excess plutonium for that very reason. Or are you saying that there wouldn't be any plutonium left from local fallout? A ground level detonation might be dirtier but would the amount of plutonium be affected since it probably wouldn't come from the ground?

 

[AntonL]

http://english.kyodonews.jp/news/2011/04/85259.html"

TOKYO, April 13, Kyodo

Some of the spent nuclear fuel rods stored in the No. 4 reactor building of the crisis-hit Fukushima Daiichi power plant were confirmed to be damaged, but most of them are believed to be in sound condition, plant operator Tokyo Electric Power Co. said Wednesday.

The firm known as TEPCO said its analysis of a 400-milliliter water sample taken Tuesday from the No. 4 unit's spent nuclear fuel pool revealed the damage to some fuel rods in such a pool for the first time, as it detected higher-than-usual levels of radioactive iodine-131, cesium-134 and cesium-137.

Asahi in their text quote 220 Bq/cm³

What are higher than usual I-131 doing in the SPF of unit 4 - Unit 4 was last operational on 30 November 2010.? The obvious question is SPF 4 sub-critical? We now need to see the results.

Asahi in their text quote 220 Bq/cm³

 

[tsutsuji]

A research team from Kyoto, Hiroshima, Kokugakuin, Nihon universities presents its "Interim Report on Radiation Survey in Iitate Village area conducted on March 28th and 29th" : http://www.rri.kyoto-u.ac.jp/NSRG/seminar/No110/Iitate-interim-report110404.pdf. It includes a gamma ray radionuclide analysis of soil samples.

 

[Krikkosnack]

A research team from Kyoto, Hiroshima, Kokugakuin, Nihon universities presents its "Interim Report on Radiation Survey in Iitate Village area conducted on March 28th and 29th" : http://www.rri.kyoto-u.ac.jp/NSRG/seminar/No110/Iitate-interim-report110404.pdf. It includes a gamma ray radionuclide analysis of soil samples.

thanks, good job.. i was searching this report

 

[PietKuip]

http://english.kyodonews.jp/news/2011/04/85259.html"

What are higher than usual I-131 doing in the SPF of unit 4 - Unit 4 was last operational on 30 November 2010.? The obvious question is SPF 4 sub-critical?

That was 16 half-lives ago. Should have declined by a factor of 65k.

We now need to see the results.

 

[Dmytry]

That was 16 half-lives ago. Should have declined by a factor of 65k.

Simply gone critical after it was damaged then covered by water. Nothing really outstanding, http://www.johnstonsarchive.net/nuclear/radcrit.html" are common.

 

[clancy688]

http://english.kyodonews.jp/news/2011/04/85259.html"

Probably a dumb question, but people are saying, that there are no dumb questions:

The roof of Unit 4 is totally collapsed, so the fuel pool is basically open to the atmosphere. So what do higher levels of iodine and caesium prove? These particles could have come from Units 1-3 and just dropped into the pool...