Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Astronuc]

Actually their retraction never states that they did not detect I-134. It merely states the levels stated were for a different isotope, Co-56.

Yes - I notice that. The significance depends on the relative activities of I-134 and Co-56, and how they correct the activity from the time of measurement back to the time the sample was taken. The I-134 activity should decrease at a great rate. If they corrected the Co-56 activity using the I-134 decay rate, then they would have determined a much greater activity for I-134 than actually existed.

Ideally, by sampling one hour or so later, they can then do the decay for I-134 and Co-56 and adjust accordingly and correctly.

 

[Borek]

Here is a simulation of the Sanriku tsunami earthquake of 1896 i was talking about (height 36m), the wave is simulated 10 minutes after the earthquake:

This is not entirely just - in general Japan has no earthquake safe places.

 

[epistememe]

Here is an excellent lecture on reactor physics from KITP.

http://online.itp.ucsb.edu/online/plecture/bmonreal11/rm/flashtv.html

 

[|Fred]

2.9 trillion becquerels I-134 per liter! => assuming the fission stopped on the 14th that would be some thing in the range of 2.9*10^9= N *(0.5)^((27-14)*24))
2,419*10^103 atom of I-134 just for this liter (some one clever should be able to calculate the weight of that)
well that's 4.14*10^81 kg
which is about 13 orders of magnitude heavier than the entire universe
perhaps you miscalculated?

You'll find my calculation below , It rather show that there was no way this iodine was original fission product before scram (point I was tring to make but without the final touch calculating the mass )

I-134 has a Half life of 50 minutes I round it up to 60 minutes.. between the scram and the measurement 13 days ( 13*24) =312 Halflife
They said there was 2.9 x 10^9 Becquerels of I-134 in that liter meaning there was 2.9 10^9 atom of I-134

Number of iodine at scram = 2.9 x 10^9 x 2^312

 

[ivars]

http://www.tepco.co.jp/cc/press/betu11_j/images/110327o.pdf

Tepco's new numbers. On a different forum, TH1960 writes: "The first column is "ayamari" - mistaken. "

Tepco's new numbers does not include neither I-134 nor Co-56. However, every isotope below I-131 has increased in activity by 30-50% in last 12 hours.

 

[Joe Neubarth]

Concerning the tsunami assessment problem relative to nuclear installations AND their safety devices like EDG, I would like to know more about how was designed the tsunami model made by TEPCO "according to JSCE method published in 2002"? They are saying they are modelling the "highest possible tsunami" but this doesn't sounds easily understandable taking account some basic facts...

http://www.netimago.com/image_182963.html
http://www.jnes.go.jp/seismic-symposium10/presentationdata/3_sessionB/B-11.pdf

In particular, are they taking into account the fact that a specific type of tsunamis, called "Tsunamis earthquakes", can happen and create huge waves even if the magnitude of the source earthquake is not that big, because of some specific conditions (with slow rupture at the fault and many other complex parameters)?

http://www.scidev.net/fr/latin-america-and-caribbean/news/un-mod-le-simple-pourrait-pr-voir-les-rares-s-ismes-provoquant-des-tsunamis-.html
http://www.eri.u-tokyo.ac.jp/seno/Papers/2002GL014868.pdf

The record 36m high tsunami at Sanriku (1896) is believed to be a tsunami of that type (tsunami earthquake), and Sanriku have been a place of huge tsunamis even if earthquakes were not so big than the current one:

1896 (magnitude 7,2 / wave height 36m): http://en.wikipedia.org/wiki/1896_Meiji-Sanriku_earthquake



1933 (magnitude 8,4 / wave height 28m): http://en.wikipedia.org/wiki/1933_Sanriku_earthquake

If some people on the forum are knowledgeable on these subjects and methods please don't hesitate to bring some infos. Putting the EDG at a certain height which is safe seems good sense but what has to be this certain height? How all this stuff is really elaborated? Should be reviewed quickly as i feel many nuke plants are not so far from the ocean... and not so far from Sanriku either!

Knowing the potential for hundred foot Tsunamis, the engineers for Fukushima placed the Emergency Diesel Generators in a position where they could be flooded with water. There is no excuse for that. All you can do is scratch your head and wonder, "Why?" This entire crisis would not have occurred if the generators were able to provide power to the plant as they were designed to do in an emergency.

Anybody who has ever walked along the sea shore knows that when a wave washes ashore the in rushing water can (because of inertia) go higher up the shore than the initial wave height. With consideration given to the the likelyhood of a Tsunami, the only place to put the Emergency Generators would be high up the hill.

 

[rhody]

As a former NPP manager, I've been closely following this event from the beginning, but just found this forum yesterday. I've been trying to put myself in their shoes to better understand what they are dealing with.
I would fully expect that they are doing their best to limit doses to workers ALARA - even in these very stressful circumstances. They would not be irresponsibly simply ordering someone to go and get a sample. They would do their best to use long handled sampling, different routes etc and HP briefings to minimize dose.

RealWing,

Since you a a former Nuclear Power Plant (NPP) manager, do you or did you use virtual simulator(s) which would show various parts of the reactor, where samples would be taken (under normal circumstances) for training purposes, and in this case general knowledge ? Using terms such as http://www.google.com/url?sa=t&sour...q431mjUA&sig2=Jkr2XAn9Jec3DGUZVjZ0MA&cad=rja", "as low as reasonably achieveable", threw me for a second, but with google, not for long. Screen shots of various parts of the structures involved would greatly aid those attempting to prepare and rehearse the difficult tasks that lie ahead. Are these tools available to those closest to the crisis ? I realize you may or may not know but I thought I would put this out there in case someone following this thread can answer the question. The people addressing the crisis need all the tools they can afford themselves of, and to add the pressure of the world watching them, I can't even begin to imagine what they are going through as they analyze and face each new challenge.

Rhody...

 

[M. Bachmeier]

Questions:

1) Does the cooling (power transfer) system for the core of a Mark I have a series of automatic cut-off valves that would stop a leak from (in large quantities) coming from pipes in that system?

2) Assuming (1) does the presences of large quantities of water (that appear to come from core containment) lead to the conclusion that core containment has been breached? (significant cracks)

3) (1), (2) x reactor #1, or 2, or 3, or all?

 

[KateB]

The chart of nuclides indicates that electron capture is the predominant mode of decay for Co-56. Nevertheless, I expect they are looking for characteristic gammas (gamma spectroscopy) with which to identify the radionuclides.

Decay gammas are generally discrete, as opposed to beta decay which represents a continuum of beta (and antineutrino) energies.

Odd. This site reports Co-56 decay as positron:
http://www.periodictable.com/Isotopes/027.56/index2.p.full.dm.prod.html

While the chart of nuclides does indeed report electron capture as mode of decay:
http://www.nndc.bnl.gov/chart/decaysearchdirect.jsp?nuc=56CO&unc=nds

I guess the .gov site wins. But I wonder at the discrepancy...

 

[KateB]

Yes - I notice that. The significance depends on the relative activities of I-134 and Co-56, and how they correct the activity from the time of measurement back to the time the sample was taken. The I-134 activity should decrease at a great rate. If they corrected the Co-56 activity using the I-134 decay rate, then they would have determined a much greater activity for I-134 than actually existed.

Ideally, by sampling one hour or so later, they can then do the decay for I-134 and Co-56 and adjust accordingly and correctly.

So basically, it's possible that the initial readings were a conglomeration of I-134 and Co-56, and only after a second reading when decay energies had transitioned,were they able to discern between the two?

 

[jlduh]

Anecdotally, I do have a friend who makes his living servicing large generators and bringing in temporary generators in emergency situations. I haven't spoken to him recently, but I believe I remember him complaining about all the different interface types that were involved in "hooking up" an emergency generator if power were needed quickly. Not always an easy task.

I read somewhere that at Daichi when they were trying to connect temporary power generators after the accident they got cable problems, should try to find some sources for this info...

 

[Astronuc]

So basically, it's possible that the initial readings were a conglomeration of I-134 and Co-56, and only after a second reading when decay energies had transitioned,were they able to discern between the two?

The longer half-lived decaying Co-56 would not decrease in activity as much. To discern between mixed isotopes, one has to let the shorter-lived isotope to decay over a reasonable time period - e.g., one-half life or several half-lives, depending on how significant the difference in half-lives and how urgently one needs the results.

This is the method to count the set of delayed neutron precursors which have half-lives on the order of seconds up to 55 seconds. There are 6 major groups.

 

[Astronuc]

Odd. This site reports Co-56 decay as positron:
http://www.periodictable.com/Isotopes/027.56/index2.p.full.dm.prod.html

While the chart of nuclides does indeed report electron capture as mode of decay:
http://www.nndc.bnl.gov/chart/decaysearchdirect.jsp?nuc=56CO&unc=nds

I guess the .gov site wins. But I wonder at the discrepancy...

I'd go with the government site (Brookhaven National Lab and the NNDC (which I think is the National Nuclear Data Center)).

See also - http://wwwndc.jaea.go.jp/cgi-bin/nuclinfo2010?27,56

Decay mode     Half-life 
  EC           77.233 D 27

 

[KateB]

I'd go with the government site (Brookhaven National Lab and the NNDC (which I think is the National Nuclear Data Center)).

See also - http://wwwndc.jaea.go.jp/cgi-bin/nuclinfo2010?27,56

Decay mode     Half-life 
  EC           77.233 D 27

I think I figured it out. I am assuming that B+ emission was the forebearer (as they would have the same outcome) I looked and you need a 1.022 or more MeV change between Co-56 and the daughter for positron (which there isn't), any less is electron capture. Thanks for being my sounding board :)

 

[AntonL]

http://www.tepco.co.jp/cc/press/betu11_j/images/110327o.pdf

Tepco's new numbers. On a different forum, TH1960 writes: "The first column is "ayamari" - mistaken. "

So they simply deleted Co-56, Ag-108m & I-134
retested the same sample 18 hours later and
Tc-99m increased from 8.7E04 to 4.8E05 a factor 5
Again a mistaken reading -
give me some time and I will work out the lifetime what they are measuring

The second sample has no trace of Tc-99m

 

[PietKuip]

So they simply deleted Co-56, Ag-108m & I-134
retested the same sample 18 hours later and
Tc-99m increased from 8.7E04 to 4.8E05 a factor 5
Again a mistaken reading -
give me some time and I will work out the lifetime what they are measuring

The second sample has no trace of Tc-99m

The second column is a revised analysis of the same gamma spectrum. Suddenly the total activity is two orders of magnitude lower. It should be impossible to reconcile both analyses with the same total count rate of their sample...

But they measured that spectrum 10 hours after it had been taken. I agree, those levels of I-134 were impossible in a sample that was so old. Maybe they extrapolated small signals back to the time of sampling, multiplying "noise peaks" with 65000 ??

The third columns is from a new spectrum of the same sample. The fourth column is from a new sample.

 

[jlduh]

Joe Neubarth:

Anybody who has ever walked along the sea shore knows that when a wave washes ashore the in rushing water can (because of inertia) go higher up the shore than the initial wave height.

Yep, this leads to the difference between the "run up" and the "wave height", this schematics is self explanatory:

http://www.netimago.com/image_183063.html

Interesting also, it seems the highest run up the 11th March has reached more than 23 meters at Ofunato. And also of interest it has been almost 15 meters at Onagawa port, (don't know at Onagawa nuclear plant). You can see this in the document below, and observe that the variations are large over local configurations on the coast (one can then ask what kind of accuracy limits we can get from the models used to calculate safety risks...).

http://sendai.hmdc.harvard.edu/portal/other_distro/PARI_Field_Survey_02.pdf

 

[83729780]

something to keep an eye on: pressure in RPV #1 is rising once again:

Reactor pressure
(A) 0.374MPaG, (B) 0.416MPaG (27th 09:00)

http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1301226468P.pdf

compare to:

(A) 0.365MPaG, (B) 0.389MPaG (26th 21:00)

(A) 0.351MPaG, (B) 0.380MPaG (26th 13:00)

(A) 0.376MPaG, (B) 0.360MPaG (26th 09:30)

(A) 0.353MPaG, (B) 0.360MPaG (26th 05:00)

(A) 0.338MPaG, (B) 0.338MPaG (25th 18:30)

why?

 

[RealWing]

RealWing,

Since you a a former Nuclear Power Plant (NPP) manager, do you or did you use virtual simulator(s) which would show various parts of the reactor, where samples would be taken (under normal circumstances) for training purposes, and in this case general knowledge ? Using terms such as http://www.google.com/url?sa=t&sour...q431mjUA&sig2=Jkr2XAn9Jec3DGUZVjZ0MA&cad=rja", "as low as reasonably achieveable", threw me for a second, but with google, not for long. Screen shots of various parts of the structures involved would greatly aid those attempting to prepare and rehearse the difficult tasks that lie ahead. Are these tools available to those closest to the crisis ? I realize you may or may not know but I thought I would put this out there in case someone following this thread can answer the question. The people addressing the crisis need all the tools they can afford themselves of, and to add the pressure of the world watching them, I can't even begin to imagine what they are going through as they analyze and face each new challenge.

Rhody...

We didnt have virtual simulators for this. We had pre-designated normal and emergency sampling points and operators and chem techs were obviously trained and qualified on these. This was all assuming events that were "design basis events" and in later years for some analyzed "beyond design basis events". What is occurring in Japan is outside of any analyzed event
Many plants had made virtual plant tour videos of normally inaccessible parts of the plant (eg in a BWR, many areas in the turbine building are inacessible or have restricted access when the plant is operating) for work planning and modification purposes. I do not know if the Japanese utilities had these or not. (It has been many years since I've been in a Japanese reactor!)

 

[Reno Deano]

Spent fuel pools contain things other than intact fuel bundles: damages fuel rods, highly irradiated RPV QC coupons, used incore detectors, irradiated reactor internals, etc., and most plants store their Pu-Be neutron calibration sources on the spent fuel pool deck or the turbine building for ease of calibrating instruments at various distances. All of these (except the Pu-Be shielded source) could be sources of various radionuclides.

 

[AntonL]

OffTopic: Political fallout in Germany

In today's two German by-election the Green Party had huge gains
4.6% --> 15.4%
11.7% --> 24.2%

 

[rmattila]

I apologize for taking up a topic already discussed thoroughly on this thread, but there's one thing I've been trying to find an answer to, thus far with no success:

As far as I understand, the US plants with Mark I containments were at some point of time refitted with what is called a "hardened venting", mentioned e.g. http://www.scribd.com/doc/51291366/Report-BWR-Mark-I-Containment-03192011-2 , page 10). Would anyone have any idea, whether the plants in Fukushima Dai-ichi had anything equivalent, or was the venting of containment steam attempted e.g. through pipe lines designed just for changing the atmosphere from air to nitrogen under normal pressure/temperature conditions?

 

[rhody]

We didnt have virtual simulators for this. We had pre-designated normal and emergency sampling points and operators and chem techs were obviously trained and qualified on these. This was all assuming events that were "design basis events" and in later years for some analyzed "beyond design basis events". What is occurring in Japan is outside of any analyzed event
Many plants had made virtual plant tour videos of normally inaccessible parts of the plant (eg in a BWR, many areas in the turbine building are inacessible or have restricted access when the plant is operating) for work planning and modification purposes. I do not know if the Japanese utilities had these or not. (It has been many years since I've been in a Japanese reactor!)

Thanks RealWing,

As you stated, "outside of any analyzed event" must be really frustrating for you, Astronuc and other experts in this thread. One would hope, but not expect the general public to understand. I never am failed to be amazed at critical moments in history, the Apollo 13 rescue effort comes to mind, how the best minds can improvise solutions to seemingly impossible situations. I hope history repeats itself here. I hope that all necessary expertise will be brought to bear to relieve the short term crisis and to come up with a long term solution.

Rhody...

 

[KateB]

Regarding the TC-99m sample and the apparent practice of extrapolating back to the time of the sampling as indicated in TEPCO explanation

Using a 1/2 live of 6.02 hours
8.7E04 -- 10h --> 5.57E04
4.8E05 -- 28h --> 1.19E04

assuming that 5.57E04 and 1.19E04 are the actual lab readings
then one can calculate a half life of 11.34 hours

1.057E06 --- 10h --> 5.57E04 -- 18h --> 1.19E04

What isotope has an half life of 11.34 hours ?

could it just be variance in the samples? I am also wondering about the Ba-140. It increased in the new testing, and I wonder if the size is within a normal margin of variability? Ba-140 is a direct fission yield, as far as I understand.

 

[|Fred]

Spent fuel pools contain things other than intact fuel bundles: damages fuel rods, highly irradiated RPV QC coupons, used incore detectors, irradiated reactor internals, etc., and most plants store their Pu-Be neutron calibration sources on the spent fuel pool deck or the turbine building for ease of calibration instruments at various distances. All of these (except the Pu-Be shielded source) could be sources of various radionuclides.

Thank you for this input, that gives some insight on non purely theoretical fact

 

[timeasterday]

Some video taken Sunday: http://peevee.tv/v/84w992

A few screen grabs from the video here: http://mainichi.jp/select/jiken/graph/20110327_2/

 

[RealWing]

It is maybe useful to go back to the TMI event, which is the only large scale partial core melt due to lack of cooling. It does give some insight into how rapidly the core can start slumping/melting and the reactivity effects. (TMI was a PWR, but core response would be generally similar to a BWR)
For example, some quotes from the Vessel Investigation Report http://library.iit.edu/govdocs/resources/NUREGCR6197part02.pdf

"PHASE 2 (100-174 minutes)
During this period, interactions between melted cladding and structural materials resulted in eutectic material flowing down through the central region of the core until it reached the liquid/steam interface where it solidified, forming the lower supporting crust. Analysis revealed that the lower crust was a Zr-Ag-In-Fe-Ni metallic mixture.5 Zircaloy cladding and Inconel grid spacers most likely formed the first eutectics. Stainless steel control rod cladding would melt when temperatures exceeded 1,427°C. The cladding may also have been breached due to interactions between the stainless steel cladding and molten zircaloy, since the materials form relatively low temperature eutectics. After cladding failure, molten Ag-In-Cd control material with a melting temperature of 827°C would flow down into the crust. Increased fuel rod temperatures would eventually lead to fuel melting.

Phase 4 (224 to 226 minutes)Some control material and quenched, fuel-bearing ceramic material apparently relocated to the lower head prior to 224 minutes. However, the majority of the ceramic material that was deposited on the lower head relocated from the core to the lower head beginning 224 minutes after reactor scram. Debris relocation was completed in approximately 120 seconds. The relocation was substantiated by a sharp increase in pressure and by the increase in SRM count rate"

Note the 120 seconds time frame and the increase in the "SRM count rate" The SRM is the Source Rate Monitor which is a low range fission counting device. This indicates that there was an increase in the fissioning process, (but it was nowhere near going critical.)

There has been several posts about the possibility that the reactor could achieve criticality again and my assessment is that it is possible although unlikely. If the fuel geometry is in the right configuration with some water as moderator and with insufficient poison in the water (eg boron) or the absence of control rod blades, then it could go prompt critical. That is why they are doing whatever they can to ensure boron is being added to any coolant going into the core.

The worst case event is for one (or more) reactors going critical without any control on the power increase. Having said that, BWR's -as designed- are inherently stable (ie as power increases, reactivity decreases), however I have no idea how they behave if the core geometry changes due to melting of the fuel pencils.

 

[83729780]

Some video taken Sunday: http://peevee.tv/v/84w992

I hope 3:45 to 3:47 settles the corium vs. insulation debate (even though the footage is from #3).

 

[havemercy]

I hope 3:45 to 3:47 settles the corium vs. insulation debate (even though the footage is from #3).

Could you explain that please ? (ok, thanks for the response below ;)

 

[Astronuc]

I apologize for taking up a topic already discussed thoroughly on this thread, but there's one thing I've been trying to find an answer to, thus far with no success:

As far as I understand, the US plants with Mark I containments were at some point of time refitted with what is called a "hardened venting", mentioned e.g. http://www.scribd.com/doc/51291366/Report-BWR-Mark-I-Containment-03192011-2 , page 10). Would anyone have any idea, whether the plants in Fukushima Dai-ichi had anything equivalent, or was the venting of containment steam attempted e.g. through pipe lines designed just for changing the atmosphere from air to nitrogen under normal pressure/temperature conditions?

My understanding is that Mk I do not have hydrogen recombiners - and I don't know if any have been retrofitted. I believe Mk II and Mk III do.

 

[warren_c]

I just want to thank every one who has contributed to this thread especially the PF mentors and those who have worked in the industry. I have learned a lot from all of your knowledge and I appreciate that most of the discussion has been fact based.

Thank you all. I wish the best for Japan and hope they get the situation under control soon.

 

[RealWing]

My understanding is that Mk I do not have hydrogen recombiners - and I don't know if any have been retrofitted. I believe Mk II and Mk III do.

I believe you are correct- The realtively small MK-I containment systems rely on nitrogen inerting to ensure there is a low risk of H2 explosions and the NRC accepted this in the 1980's. Powered H2 recombiners may still have been retrofitted, but withiout any power - they did nothing.

 

[Astronuc]

I think there is nitrogen in the drywell, but not on the reactor floor.

At Fukushima, it was not by design that the H₂ went into the volume above the reactor building floor. Apparently the venting system duct work (or somewhere else) ruptured/leaked. The H₂ and steam should have gone up the stack.

The point to be emphsized here is that the event is well BEYOND design basis - the combined effects of earthquake and tsunami (greater than design), the station blackout, and then the injection of seawater and boric acid.

You bet other plants are now looking at DBE and combined effects of natural phenomena, and their EOPs.

TVA is already looking at their units from a worst scenario.
http://www.bloomberg.com/news/2011-03-25/tva-plans-more-catastrophic-scenarios-after-japan-official-says.html

 

[Ivan Seeking]

They were just hit by another quake, about a 6.5, with a [small] Tsunami warning that affects the plant. Hopefully this won't make things worse.

 

[RealWing]

I think there is nitrogen in the drywell, but not on the reactor floor.

At Fukushima, it was not by design that the H₂ went into the volume above the reactor building floor. Apparently the venting system duct work (or somewhere else) ruptured/leaked. The H₂ and steam should have gone up the stack.

The point to be emphsized here is that the event is well BEYOND design basis - the combined effects of earthquake and tsunami (greater than design), the station blackout, and then the injection of seawater and boric acid.

You bet other plants are now looking at DBE and combined effects of natural phenomena, and their EOPs.

TVA is already looking at their units from a worst scenario.
http://www.bloomberg.com/news/2011-03-25/tva-plans-more-catastrophic-scenarios-after-japan-official-says.html

Both the dry well and wet well are interted with N2 - but not the reactor floor.

Agree about DBE events and the already analyzed beyond DBE events- we need to rethink this whole issue - particularly for older reactors. The new "advanced" reactor designs have what appears to be several passive cooling systems that do not rely on any power.

Just like TMI and Chernobyl - unfortunately it takes an tragic event such as this one to make all us engineers and plant operators look hard at the lessons-learned and act on them.