Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[rmattila]

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110526_01-e.pdf"

Those curves seems to be in rather good agreement with the quesstimate I presented earlier in post 5788 on page 362.

 

[tsutsuji]

Switchgear or fuel tanks could have been damaged with the same result as flooding the generator rooms themselves. If it turns out impossible to protect the whole site, protect the essential parts of the site from inundation.

On Mamoru's layout plan for Fukushima Daiichi unit 3 at http://3.bp.blogspot.com/-JaxFid8Qo...AAko/t5TVRl5sb-4/s1600/R3++completa+small.jpg there is a white rectangle a few steps south of Diesel engine 3A called (in Italian) "boccaporto cisterna carburante" (Fuel tank hatch). So, my understanding is that the fuel tanks used by the diesel generators are located there, underground. If they can withstand the pressure from the water during the flooding and if the air intakes are located high enough, these tanks are probably OK.

 

[biffvernon]

What's all this >200Sv/hr in the #1 dry-well about?

http://atmc.jp/plant/rad/?n=1

 

[zapperzero]

1 Bq per 72 hours of I131? We wish! Obviously the reporter dropped a few orders of magnitude.

That was the source used for the simulation.

 

[Rive]

TEPCO admits to having performed dry venting of the No 2 pressure vessel on 15Mar.

I assume "dry venting" indicates that the RPV was vented to atmosphere without traveling through the wet filtration of the torus.

http://search.japantimes.co.jp/cgi-bin/nn20110330a3.html"

As I recall the fuel was already damaged at that time, so...

 

[NUCENG]

Thanks for the details. The question is:

it's possible to protect them (resistant to tsunami may be tougher though?), but was it the case, and is it the case everywhere on a so critical part of the nuke plants?

Also, what about the risks of damaging the impellers/shafts loads during water hammering? The longer an axis is, the weaker it is in case of tsunami hit.

Never really thought about it since the plants I'm familiar with are inland. However looking at the overhead photographs and drawings in the TEPCO handouts it appears that each pump is in a separate well or bay in the intake structure and thus is partially shielded from the insurge and probably completely shielded from runback forces. The impeller, shaft, volute and riser pipes can be mounted and anchored to the walls of the bay or well. How well they are protected I don't know for sure, but the motors look like they were more exposed to the tsunami than the pumps may have been. How well mounted and protected they are from surge effects will determine whether shafts or impellers are subject to damage.

I can't answer the question on how well protected these pumps at all plants. I have been in US plants on the Great Lakes that have to protect against seiche effects which are similar to tsunamis but come from harmonic amplification of waves back and forth across the lake.
These plants have quite detailed analysis to support the design basis wave heights and to demonstrate how vital systems are protected. I think some of their protective walls may be bigger than the seawall at Fukushima Daichi. Other plants are evaluated for river flooding which usually gives some notice and allows for procedure driven preparation to add protection such as sandbagging or installing panels over louvers or other similar actions.

A couple years ago plants in the US Midwest were subjected to a "1000 year flood" and continued to operate with minimal impact other than making the trip to work a little longer to avoid water. At one plant operators had to take a boat to the intake structure for inspection tours and maintenance.
I'm not sure how water hammer is involved in these pumps. Water hammer is the high pressure impact on a system caused when flow is initiated into a voided portion of the system and the void collapses causing the hammer effect. Cavitation and vibration are bigger threats to these centrifugal pumps.

In addition, plants all over the world should be watching the Fukushima event closely for lessons learned.

 

[tsutsuji]

The Incinerator building basement, where the contaminated water from unit 3 had been moved, was suspected of leaking :

Engineers learned that the water level had dropped by 4.8 centimeters over a 20-hour period, meaning some 57 tons of water has been lost.
Thursday, May 26, 2011 19:57 +0900 (JST) http://www3.nhk.or.jp/daily/english/26_34.html

The missing water has finally been found in a tunnel joining two buildings. There has been no leak into the ground water, according to http://mainichi.jp/select/science/news/20110527k0000m040110000c.html

 

[NUCENG]

As I recall the fuel was already damaged at that time, so...

That may explain why the hydrogen explosion in unit 2 was in the torus. Venting from the drywell would have lowered H2 concentration there, but the amount of hydrogen from the tous through the vacuum brakers to the drywell would have been slower to reduce H2 concentration in the torus.

Venting directly from the drywell loses the scrubbing effect of the suppression pool when venting from the torus. So they increased the release to the environment and the public after being reluctant to vent unit 1 at all. I'd sure like to see their reasoning for that. The only thing I can think is that the dry venting may have been done after explosions in units 1 and 3, and they were trying not to repeat that experience again.

 

[~kujala~]

Those curves seems to be in rather good agreement with the quesstimate I presented earlier in post 5788 on page 362.

So it seems.
I took one check point, after 180 days for units 2 & 3, and for TEPCO it's about 1 MW and for your chart it's about 0,9 MW (or something like that):

http://varasto.kerrostalo.huone.net/decay_heat_mattila.png
http://varasto.kerrostalo.huone.net/decay_heat_tepco.png

Perhaps they copied your chart and put it in non-exponential scale to look like brand new?

This ~ 1 MW is also something we have for unit #4 SFP now, if I have understood correctly.

 

[tsutsuji]

TEPCO admits to having performed dry venting of the No 2 pressure vessel on 15Mar.

I assume "dry venting" indicates that the RPV was vented to atmosphere without traveling through the wet filtration of the torus.

http://search.japantimes.co.jp/cgi-bin/nn20110330a3.html"

My understanding of Japan Times' Tepco quoting sentence "Yesterday, we said the dry vent of the No. 2 reactor was done March 16 to 17, but it was the 15th" is that "done" means "attempted", not "performed".

According to the New York Times :

At Reactor No. 2, workers tried to manually open the safety valves, but pressure did not fall inside the reactor, making it unclear whether venting was successful, the records show.

17 May http://www.nytimes.com/2011/05/18/w...pagewanted=2&sq=fukushima valves&st=cse&scp=7

I am not sure if Tepco changed its position since May 17th about how successful these venting attempts have been.

 

[~kujala~]

We have some good news for a while:

it will increase the number of sampling spots for groundwater

http://mdn.mainichi.jp/mdnnews/news/20110526p2g00m0dm079000c.html

If they have sub-drains below waste facilities I am sure these are now included as sampling spots. We'll see.

If there are sub-drains below waste facilities it also means that even if some contaminated water leaks there the sub-drains should take care of it (or at least part of it) and collect it into the sub-drain pits - which later could be emptied.

 

[NUCENG]

With a 16 second half life, I'm guessing the radiation is not coming from the N-16. After all the time that's passed, I'd guess the least bad scenario would be one of the Cs isotopes.
(thread regarding the radioactive pile of rubble, in case anyone is wondering)

Sorry, I should have linked my post to Robinson's post instead of Zapperzero. I was replying to his thought that normal plants were not anywhere near 1 Sv/hr.

During a submarine refueling I witnessed a dribble of water fall onto the floor of the refueling shack while removing a spent fuel assembly into a transfer cask. A Health physicist took a swipe of the spill using a small paper swipe. When he checked the reading it overranged a frisker and so he checked it with another high range detector. It was 75 R/hr or about 0.75 Sv on contact. Apparently that dribble contained a bit of highly activated CRUD. That little piece of paper was a walking high radiation area. It doesn't take much volume to make a lot of radiation depending on the isotope and its half life.

 

[Astronuc]

I have been lurking for a while (this is about the only place on the net where a meaningful discussion takes place) and i figured you guys might be interested in this:

---
A meltdown occurred at one of the reactors at the Fukushima No. 1 Nuclear Power Plant three and a half hours after its cooling system started malfunctioning, according to the result of a simulation using "severe accident" analyzing software developed by the Idaho National Laboratory.

Chris Allison, who had actually developed the analysis and simulation software, ...
---
http://mdn.mainichi.jp/mdnnews/news/20110523p2a00m0na019000c.html

I suspect that the analysis might have been very conservative, and perhaps considered adiabatic conditions, i.e., no heat removal from the fuel. I would like to see Allison's report.

See also - http://www.world-nuclear-news.org/RS_Large_scale_melt_predicted_at_units_2_and_3_2605111.html


Meanwhile, Westinghouse is responding to the event by introducing a mobile emergency SFP cooling system.
http://www.world-nuclear-news.org/RS-New_system_to_keep_fuel_pools_cool-2605117.html

 

[Jorge Stolfi]

Is recriticality possible in corium too? It has no internal cavities for water

AFAIK it is not necessary for the moderator to penetrate the fuel; just surrounding the fuel with moderator should be enough.

To have fission one needs to have a significant fraction of the emitted neutrons slowed down and scattered back to the fissile material. If the fuel is immersed in a large amount of moderator, and there is no absorption, every neutron that leaves it will eventually be scattered back to it, by "drunkard's walk" statistics. (This is the same effect that makes sunlit clouds look white.)

The half-life of a free neutron's is 15 minutes, so decay should not be a significant factor.

I suppose that neutron absorption is the main factor preventing re-criticality. TEPCO has been using boron in the emergency cooling water; the effect should be like that of soot particles making smoke clouds black instead of white. Also the corium itself may (or may not) include neutron-absorbing material from the control rods.

Is this correct?

 

[havemercy]

Hello to all. I'am very sorry if this question has already been asked, but it is quite difficult to read all the posts to check.

Is it possible that the corium, we know TEPCO said has been in the bottom of the reactor vessel, has leaked out in a porous soil, and, with contact with the water in such soil, resulted in a low blast that everybody has interpreted as a replica of 5.6 on Richter scale ?

(Sorry for the english)

Many thanks in advance.

 

[SteveElbows]

resulted in a low blast that everybody has interpreted as a replica of 5.6 on Richter scale ?

When do you think this may have happened?

 

[SteveElbows]

What's all this >200Sv/hr in the #1 dry-well about?

http://atmc.jp/plant/rad/?n=1

This subject seems to keep coming up every day for several days in a row now. Is someone posting scare stories about this data elsewhere on the internet, or is it just that lots of people have been using that atmc website graphs all along and are now wondering why its showing scary stuff?

In any case, this subject has been addressed here multiple times in recent days. Main summary of points:

The atmc website makes some bad errors with what data it uses sometimes, so it is not a good idea to use it as main source. Use TEPCO data instead, which shows 2 x drywell CAMS and 2 x suppression chamber CAMS readings for all reactors.

Main data site index page: http://www.tepco.co.jp/en/nu/fukushima-np/index-e.html

The CAMS readings are part of the pressure & temperature data sheet, so for reactor 1 it is:

http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/11052606_level_pr_data_1u-e.pdf

So yes, one of the sensors is sometimes showing values of 200 or higher. But the other sensor shows much lower values, and TEPCO think the sensor(s) may be damaged because they don't agree with each other, and one of them fluctuates a lot.

Other thing to note is that this is not a new thing, only reason its suddenly being noticed is because TEPCO only started publishing the data for this sensor again recently (around may 17th), after not bothering for many weeks, probably because the readings seemed unreliable.

In conclusion, there are too many unknowns about this data to make any conclusions, and if there is a problem its not a new event, it happened quite a long time ago. I do not think the CAMS data is good enough to be able to use it to reach interesting and firm conclusions about how much of the core fell into the drywell, so there is no point getting excited about the big numbers. All it really tells us is that fuel got damaged, and we know that already.

 

[havemercy]

On April 22 :

According to RBC, the epicenter of the earthquake was located at a depth of 35.8 km at a distance of 74 km from the city of Fukushima, and only 22 km from the nuclear power plant "Fukushima-1. According to the US Geological Survey, tremors were recorded at 19:25 MSK.

http://mysouth.su/2011/04/in-fukushima-prefecture-earthquake-of-magnitude-5-6/

 

[elektrownik]

The problem is that second sensor which show low value can't be correct if any amount of corium is in drywell, this hight value can be corect if corium hit drywell cams sensor... Chernobyl was >300Sv around core, at this time we know on 99% that unit 1 core melted from rpv and damaged drywell

 

[mscharisma]

The Incinerator building basement, where the contaminated water from unit 3 had been moved, was suspected of leaking :

The missing water has finally been found in a tunnel joining two buildings. There has been no leak into the ground water, according to http://mainichi.jp/select/science/news/20110527k0000m040110000c.html

Does this fall into the good or the bad news category? No leak into groundwater is surely good, but there wasn't supposed to be any kind of leak, I assume? What, if anything, does it tell that also the wastewater facility leaks somehow?

 

[Borek]

blast that everybody has interpreted as a replica of 5.6 on Richter scale ?

On April 22 : According to RBC, the epicenter of the earthquake was located at a depth of 35.8 km at a distance of 74 km from the city of Fukushima, and only 22 km from the nuclear power plant "Fukushima-1. According to the US Geological Survey, tremors were recorded at 19:25 MSK.

No idea why you think these things are in any way related. Epicenter was 22 km from the plant, not under reactor building. Besides, there were many quakes in the area since the big one, why this particular one caught your attention?

 

[havemercy]

Because it is the nearest of the plant.

 

[elektrownik]

Because it is the nearest of the plant.

If there would be explosion which would generate 5.6 quake then you wouldn't see reactor buikdings anymore...

 

[clancy688]

In my opinion, ANY steam explosion that triggered a 5.6 magnitude quake would've been a boom that would give the Hiroshima bomb a run for its money...

 

[SteveElbows]

be patient guys my first try at photo well maybe second

Has this been posted?

found it at Cryptome..was taken March 16, and the deck looks a lot worse in later photos.
it's in the zipped file of full size photos and has this name: aerial-2011-3-18-14-50-0.jpg
(editing mine, with MS-Paint, which clobbers the resolution)

you can see the concrete cap not there but i can't tell for sure about the yellow thing on right. In the hi-res it's a maybe.

Would one who knew how to lighten be able to see down into that black hole and tell if yellow containment cap is there?

In my opinion this is one of the classic illusions from the early Fukushima pictures. I remember when I first saw it, it was briefly quite compelling because the apparent chasm was in roughly the right place. But subsequent photos and video destroy the illusion pretty well. See the problem is that with other footage we can get a glimpse of how much the crane & associated debris occupy this area, and we can see how the smoke/steam and lack of light in that part of the building create a range of shadowy unrealities in this part of the building. What looks like a nice well rounded hole appears to me to mostly be darkness and smoke, with perhaps a bit of crane and roof adding to the effect when seen from the angle that footage was taken at.

No footage has emerged that gives us a really clear idea of the exact state of things there, and no really compelling evidence has emerged from that zone, despite many people likely studying such footage a lot due to the frequent debates about whether any part of reactor 3 launched into the air. When combined with what other data tends indicate, lots of people are going to assume that nothing major launched from reactor 3, and it will now take some compelling evidence to convince a lot of people to reconsider this issue. I am not really expecting it to happen, but I'll be ready to eat my words if it does.

I remain very interested in the exact nature of containment damage at reactor 3, so I hope that one day we get a better look at the damaged areas. The closest I have got towards identifying any potential trouble, and getting a look at things I can actually identify at reactor 3 that arent badly obscured, was a picture I posted a while back. Taken from a helicopter video, it shows area where dryer storage pit/pool is joined to area above reactor, where removable concrete wall is in place. Image quality not clear enough to say with any certainty, but it is possible that we can just glimpse the very edge of one set of the semi-circular plugs that sit above the reactor. The only evidence for this in attached photo is thin black line, that may be slightly curved, in area to left of the emerging smoke. This is where top of the dryer pool concrete wall becomes part of the service level floor, and traveling further in that direction we would expect to find reactor plugs making up the next part of the floor. So perhaps this thin line is where the wall ends and the plugs begin. But because of where the crane & its supporting structure has fallen, we can only see a small portion of this service floor area, so I can't be sure of anything.

 

[Borek]

Because it is the nearest of the plant.

At 22 kilometers? Seismographic data are much better than that. If memory serves me well, places where underground nuclear tests were done were located with few hundred meters accuracy.

Edit: according to wikipedia, 5.6 is about 4 kT TNT, about one fourth of Hiroshima bomb, that would be hard to miss.

 

[Bandit127]

If there would be explosion which would generate 5.6 quake then you wouldn't see reactor buikdings anymore...

According to Wikipedia (sorry..) a 5.6 quake is equivalent to 3.8 kilotons of TNT.
http://en.wikipedia.org/wiki/Richter_magnitude_scale"

For a sense of scale - if I recall correctly from previous posts, the explosion of the Unit 3 building was expected to register about 2.2. (Working backwards from the table, I would estimate the equivalent would be about 30 kilogrammes of TNT).

Edit - Oops! Thanks Borek - I must type faster.

 

[havemercy]

Ok, then it is not possible. Thanks.

 

[jim hardy]

Jorge :
""I suppose that neutron absorption is the main factor preventing re-criticality. TEPCO has been using boron in the emergency cooling water; the effect should be like that of soot particles making smoke clouds black instead of white. Also the corium itself may (or may not) include neutron-absorbing material from the control rods.

Is this correct? ""

i'd say so. Without moderator or reflector the neutrons simply keep on going and leave the neighborhood. They can eventually emit an electron and so become a hydrogen nucleus(proton).

"To have fission one needs to have a significant fraction of the emitted neutrons slowed down and scattered back to the fissile material. If the fuel is immersed in a large amount of moderator, and there is no absorption, every neutron that leaves it will eventually be scattered back to it, by "drunkard's walk" statistics. (This is the same effect that makes sunlit clouds look white.) "
well as you said, not every neutron will make it back, some of the 'staggering drunks' fall by the wayside. It takes maybe a dozen collisions with a light nucleus like hydrogen to slow a neutron to the energy favorable for fission, maybe forty with something heavier like sodium. Remember energy in elastic collisions divides in some proportion to masses involved. Each collision stands a chance of inelastic absorbtion without fission so there's some loss by absorbtion.
You need to have about half the neutrons survive moderation to get critical.

Here's a link to a short course - you'll have no trouble with the slides. i may have posted it before, sorry, the senior moments sort of run together anymore.

http://www.if.uidaho.edu/~gunner/ME443-543/LectureNotes/ReactorPhysics.pdf

If the corium contains melted control rods it's probably safe. The addition of melted steel reactor parts could make it safe. The seawater salt is mildly absorbtive.
But its Russian Roulette.

btw i really liked your charts and bragged on them in another forum. Thanks!

old jim

 

[jim hardy]

Thank you Steve Elbows for posting this comment:
""No footage has emerged that gives us a really clear idea of the exact state of things there, and no really compelling evidence has emerged from that zone, despite many people likely studying such footage a lot due to the frequent debates about whether any part of reactor 3 launched into the air. When combined with what other data tends indicate, lots of people are going to assume that nothing major launched from reactor 3, and it will now take some compelling evidence to convince a lot of people to reconsider this issue. I am not really expecting it to happen, but I'll be ready to eat my words if it does...""

That is where I am too. It's an open but doubtful question and the absence of good photos does lend to conspiracy theory. I don't like conspiracy theory and have been looking to dispel it.

To that end i put a couple early photos over on scribd, not wanting to clutter this board with a long essay.
If you have fifteen minutes to kill, and promise to not accuse me here of fearmongering , i welcome your comment at this link, or about it here:
http://www.scribd.com/jim_hardy_9

It's an honest question. I want to rule some things out but the "optical illusions" keep on cropping up.
The link at scribd tells how to get the three high resolution photos you need to see what i see. It just won't show in the low res ones. I would post them if knew how to preserve the hi-res. One of them is from first ten seconds of that helicopter video and requires training your eye to look for it. I want to know if i am seeing what is not there.

i am working on a photobucket album but even photobucket destroys the resolution, you just got to go back to the source. and that's too much to ask of folks in a general audience.



So, happy surfing. Keep up the good work here fellows.