Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[rowmag]

So now we know that the power station is built on solid geology not alluvium. 'Mudstone' should be read as stone rather than mud. The buildings are not going to slide into the sea, as someone suggested a great many posts ago.

The significant detail about how permeable the rock immediately below the reactors buildings is to the movement of groundwater and potentially radioactive cooling water still eludes us.

Do the N values provide any indirect hints? I don't know how to interpret how they are displayed in the figure, but in the text it mentions that the lower layers typically have N=40 or greater. (I know N is a soil hardness measure, not a permeability one, but could naively imagine that a high N value suggests low permeability, absent cracks.)

 

[Bioengineer01]

RPV
All the media talk about % fuel melt is meaningless. The questions that should be asked are: where did the fuel go? and, what can be done about it?

Completely agree, the question I have is, whether anybody in the forum knows if it is true that this is something that TEPCO could be measuring to understand if the Corium is in the ground. And I know that we can't know if they are doing it or not, I am just curious if you think that this is something that could be done if they wanted to: "There are sensitive sensors all around the grounds listening for underground activity, as well as satellite based imagery used to locate bunkers and tunnels that can image the ground density. 1300C material generates pressure underground that alters the density of the ground, and these changes can be detected and visualized"

 

[elektrownik]

Here are some interesting plots, some of them show hight temperature >2500C, from where they take those data ? http://www.kantei.go.jp/jp/topics/2011/pdf/app-chap04-1.pdf

 

[etudiant]

I have also been struggling to understand at a macro level the order of magnitude of the release into the Pacific Ocean and can't find enough data to even guesstimate it. Very frustrating. My opinion and that of my colleagues is that the largest release has been and still is happening to the Ocean. Also, we all suspect that there is a continuous flow of isotopes to the ground water and from the ground water to the Ocean. The tell me that in most cases ground water in coastal sites flows to the Ocean. None of us has any information of deep water wells in the region and how they are interconnected, although we are certain that the information is out there.

The initial airborne release estimates from ZAMG in Austria, based on CTBT monitoring data, was about 10% of the total Chernobyl output of cesium and iodine per hour. Given that we now know the cores were seriously damaged quite early, those estimates seem at least as reasonable as the later downward revisions, which were never formally documented afaik.
We can hope that the bulk of the waterborne contamination is still within the site, simply because the level of Lake Fukushima is showing no signs of decline. Information as to the actual level of activity of that water is scarce, apart from the few samples taken during the efforts to halt ocean leakage. It might be useful to take those measures. extrapolate to the current volume and compare to the total in the reactors before the accident.

 

[jlduh]

The amount of water in question is 3000 tons, in the DaiNi basement. Airborne contamination is pretty unlikely. Moreover, the tsunami flooding was with clean sea water.
So the contamination was locally sourced.
Is not cesium an indicator that some fuel elements have leaked?
Afaik, DaiNi was rated as INES 3 after the tsunami, saved by one outside power line, but no lasting damage was reported then.

Article from NHK on Daini contaminated water:

http://www3.nhk.or.jp/daily/english/08_30.html

The Tokyo Electric Power Company is studying a plan to decontaminate seawater pooled at the Fukushima Daini nuclear power plant and discharge it into the sea.

TEPCO says about 3,000 cubic meters of radioactive seawater has been stagnant in the basement of the plant's reactor and turbine buildings since being hit by a tsunami following the March 11th earthquake.

The utility says the concentration of radioactive cesium in the water is 30 times the permissible limit, but that it contains no other radioactive materials exceeding the safety limits.

I remember every member on this forum that (we discussed about this a long time ago but I'm not sure everybody noted it) Tepco released the information on its website that they were "preparing to vent" at N°1 DAINI reactor after "increase of pressure in the reactor containment possibly due to coolant leakage" (that was March 12):

http://www.tepco.co.jp/en/press/corp-com/release/11031104-e.html


http://www.tepco.co.jp/en/press/corp-com/release/11031218-e.html

At 6:08PM, we announced the increase in reactor containment vessel
pressure, assumed to be due to leakage of reactor coolant. However, we do
not believe there is leakage of reactor coolant in the containment vessel
at this moment.
- At 5:22AM, the temperature of the suppression chamber exceeded 100
degrees. As the reactor pressure suppression function was lost, at 5:22AM,
it was determined that a specific incident stipulated in article 15,
clause 1 has occurred.
- We decided to prepare implementing measures to reduce the pressure of
the reactor containment vessel (partial discharge of air containing
radioactive materials) in order to fully secure safety. This preparation
work started at around 9:43am.

They didn't do it, but this probably shows that something happened there. These 3000 tons of water with Cs at a level 30 times the allowed limit could be an other signal of this, to be confirmed...

 

[Astronuc]

Here are some interesting plots, some of them show hight temperature >2500C, from where they take those data ? http://www.kantei.go.jp/jp/topics/2011/pdf/app-chap04-1.pdf

Ostensibly, those are the results of calculations made with the MAAP code. The maximum temperature is about 2800C, the melting point of UO₂.

From the English version

In addition, in order to supplement this limited information, TEPCO carried out analysis and evaluation of reactor situation of Unit 1,Unit 2 and Unit 3 using MAAP, which is a Severe Accident Analysis Code, based on gained operating records and parameters. The results were reported to NISA on May 23. NISA carried out a crosscheck by using other severe Accident Analysis Code, MELCOR in order to cross-check for validation of TEPCO’s analysis with the assistance of Incorporated Administrative Agency Japan Nuclear Energy Safety Organization in order to confirm the adequacy of the analysis and evaluation concerned by using MELCOR, another severe accident analysis code. The report of analysis and evaluation conducted by Tokyo Electric Power Company is shown in Appended Reference IV-1, and analytic results by crosscheck are shown in Appended Reference IV-2.

 

[rowmag]

Another link from the excellent ex-skf blog.

Circumstantial evidence that Fukushima Dai-ichi containment broke after the earthquake but before the tsunami:

http://www.yomiuri.co.jp/science/news/20110608-OYT1T00583.htm?from=top

http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=ja&tl=en&u=http%3A%2F%2Fwww.yomiuri.co.jp%2Fscience%2Fnews%2F20110608-OYT1T00583.htm%3Ffrom%3Dtop

Apparently there's Cesium in the water found in the basements at Fukushima Dai-ni. TEPCO says that water came in when the tsunami happened.

So they are saying there is cobalt-60 in the water, apparently from rusted piping (at Daini itself, seems to be implied). Plus there is cesium-137 and -134 that they think might have flown in from Daiichi some time in the past 3 months.

Have they reported any previous measurements made on this water?

 

[SteveElbows]

I did not claim it reached Dai-ni via water, nor does the article. That would be impossible, in the time given (an hour elapsed between quake and tsunami).

I got confused because you said 'Circumstantial evidence that Fukushima Dai-ichi containment broke after the earthquake but before the tsunami' so I thought you were implying that the stuff must have gotten into sea before tsunami. Did you actually mean that the stuff could of traveled by air before the tsunami, and was then carried inside the building by the tsunami?

 

[zapperzero]

So they are saying there is cobalt-60 in the water, apparently from rusted piping (at Daini itself, seems to be implied). Plus there is cesium-137 and -134 that they think might have flown in from Daiichi some time in the past 3 months.

Have they reported any previous measurements made on this water?

No. They have not. Also, "sometime in the past months" is highly disingenuous. That water is in a god damn basement. No way it could have gotten contaminated after it got into the basement, unless Dai-ni was/is in much, much deeper trouble than we were ever told.

 

[zapperzero]

I got confused because you said 'Circumstantial evidence that Fukushima Dai-ichi containment broke after the earthquake but before the tsunami' so I thought you were implying that the stuff must have gotten into sea before tsunami. Did you actually mean that the stuff could of traveled by air before the tsunami, and was then carried inside the building by the tsunami?

Yes that's what I am saying. I am saying it MUST have happened like that, because those basements are not open to the outside air normally. It's only ten kilometers or so as the crow flies. A gentle breeze would have had more than enough time.

 

[elektrownik]

And is this interesting: http://www.tepco.co.jp/en/news/110311/images/110608_06_2.pdf ?

 

[zapperzero]

And is this interesting: http://www.tepco.co.jp/en/news/110311/images/110608_06_2.pdf ?

Only if they exhausted stuff. I don't think they do, in normal operation. Do they?

 

[elektrownik]

Only if they exhausted stuff. I don't think they do, in normal operation. Do they?

Here is more:

At 4:00 pm on June 7, air leak was found at the weld zone of unit 4's main
emission duct by TEPCO employee. (10cm×3cm 2 places ). Radioactive
materials in the air were below measurable limits.
We will implement the repair work and check similar points soon. No outlier
at main emission monitor and monitoring post was detected. No radiation
effect is found outside.

 

[NUCENG]

Only if they exhausted stuff. I don't think they do, in normal operation. Do they?

BWRs boil water in the reactor. Small amounts of "tramp" uranium on fuel assemblies add fission products to steam and corrosion and activation products are also present. Gaseous wastes are removed from the condensers by air ejectors. The air ejector output stream is pocessed in the offgas system building to allow time for the short lived products to decay. Then the remainder is exhausted through the common offgas stack for an elevated release to maximize dispersion. At Fukushima Daiichi the offgas stack is common to plants 1-4 and is south of unit 4.

 

[zapperzero]

BWRs boil water in the reactor. Small amounts of "tramp" uranium on fuel assemblies add fission products to steam and corrosion and activation products are also present. Gaseous wastes are removed from the condensers by air ejectors. The air ejector output stream is pocessed in the offgas system building to allow time for the short lived products to decay. Then the remainder is exhausted through the common offgas stack for an elevated release to maximize dispersion. At Fukushima the offgas stack is common to plants 1-4 and is south of unit 4.

Thanks a lot for the explanation.

 

[etudiant]

BWRs boil water in the reactor. Small amounts of "tramp" uranium on fuel assemblies add fission products to steam and corrosion and activation products are also present. Gaseous wastes are removed from the condensers by air ejectors. The air ejector output stream is pocessed in the offgas system building to allow time for the short lived products to decay. Then the remainder is exhausted through the common offgas stack for an elevated release to maximize dispersion. At Fukushima Daiichi the offgas stack is common to plants 1-4 and is south of unit 4.

Thank you for the explanation.
Would these emissions be a plausible explanation for the cesium contamination in the sea water pooled in the basement?
I'm having a difficult time quantifying the scale of that problem, as contamination 30x the standard for release no longer sounds very threatening. Is this in line with some fuel rod breach or some steam leak from the turbines or what?

 

[Bioengineer01]

Excellent, finally a document that sheds some significant light on timing of certain things.

This part of the report to IAEA deals with radioactive release into the environment:

After earthquake, the discharge of radioactive materials became evident early on the morning of March 12 when the air dose rate measured by a monitoring car near MP-6(monitoring post No. 6 in the site of Fukushima Dai-ichi NPS) increased. It can be estimated that there was a leakage of radioactive materials from the PCV and a discharge of such materials to the air, as a slight decrease in the PCV pressure was observed in Unit 1 after an abnormal rise at this point. According to an analytical result, that fuel meltdown had already started.

Dont get me wrong, its not perfect, it doesn't cover everything in great detail but its way better than the complete lack of narrative we've previously had on this subject from official sources. Dont think there's anything for those fascinated by reactor 3 march 20th-23rd events though.

Yes Thanks! And, Yap! this is the perimeter sensor that I remembered reading about and mentioned before

 

[robinson]

If that is not a theoretical question but an assumption that this could have happened, I believe that the logs from reactor 1 SCRAM seem to show that the rods insertion was successful.

It was hypothetical. I was wondering what sort of disaster would occur if about everything went wrong, and how long it would take.

 

[zapperzero]

Thank you for the explanation.
Would these emissions be a plausible explanation for the cesium contamination in the sea water pooled in the basement?
I'm having a difficult time quantifying the scale of that problem, as contamination 30x the standard for release no longer sounds very threatening. Is this in line with some fuel rod breach or some steam leak from the turbines or what?

Water from the coolant circuit should NOT be in the basement, regardless. It circulates between the reactor, the turbine and the condenser. No breach of the coolant loop has been reported for Fukushima Dai-ni.

 

[MadderDoc]

Intriguingly the Report of the Japanese Government
to the IAEA gives off this new bit of information regarding the explosion at unit 3:

"Along with the explosion, the oil for the MG sets for the control of the rotating speed of
recirculation pumps burnt concurrently at the heavily damaged west side of the 4th floor
of reactor building."

I am left wondering how it could possibly have been determined, that a fire was ongoing -- concurrent with the explosion -- in the oil of the recirculation flow control system M/G sets.

 

[jim hardy]

"""It was hypothetical. I was wondering what sort of disaster would occur if about everything went wrong, and how long it would take.""""

failure to "scram"? That was an industry issue in mid 1970's and much analysis was done to answer "What If". I remember the time well. They called it 'Anticipated Transient Without Scram' .

Try google search on ATWS BWR and look for .gov reports from about 1975 to 1981 time frame.

 

[SteveElbows]

Yes that's what I am saying. I am saying it MUST have happened like that, because those basements are not open to the outside air normally. It's only ten kilometers or so as the crow flies. A gentle breeze would have had more than enough time.

Well I don't rule out the other possibility that it traveled by air and then got into the basement via rain & groundwater problems later on.

But to be perfectly honest if I had to bet money on one option right now, I would be very tempted to go with 'slightly damage to at least one Daini reactor'. Things were quite bad there for a number of days even though they were not totally without power. I wait to learn more about the stuff mentioned at the end of one of the report to IAEA documents, which features some Drywell spraying, pressure issues, and some control rod drift alarms.

Or, if there was no such damage and the stuff really came from Daiichi, I really do struggle to believe that it arrived before the tsunami. I know we now have a variety of tales and data to do with stuff escaping much earlier than originally thought, but not that early, a release within the first hour that would show up km away really does not fit very well with the data.

 

[NUCENG]

I don't think so, it makes no sense, I suspect there could be language trouble. All three Tepco
press releases from March 13th from as early as 9am say that "spraying in order to lower pressure level
within the reactor containment vessel has been cancelled', here's the context:

"High Pressure Core Injection System has been automatically shut down and water injection
to the reactor is currently interrupted. We are examining alternative way to inject water.
Also, following the instruction by the government and with fully securing safety, steps to
lowering the pressure of reactor containment vessel has been taken. Spraying in order
to lower pressure level within the reactor containment vessel has been cancelled."

They were spraying containment to condense any steam there and reduce containment pressure. With no power available they were probably using the fire fighting system to do this.

 

[SteveElbows]

I am left wondering how it could possibly have been determined, that a fire was ongoing -- concurrent with the explosion -- in the oil of the recirculation flow control system M/G sets.

If they eyeballed a fire at that location once the initial dust from the explosion died down, they may reach that conclusion.

 

[robinson]

While it was mostly lost at the time, Daini did report a fire and some scary moments after the tsunami and quake.

 

[SteveElbows]

I don't think so, it makes no sense, I suspect there could be language trouble. All three Tepco
press releases from March 13th from as early as 9am say that "spraying in order to lower pressure level
within the reactor containment vessel has been cancelled', here's the context:

"High Pressure Core Injection System has been automatically shut down and water injection
to the reactor is currently interrupted. We are examining alternative way to inject water.
Also, following the instruction by the government and with fully securing safety, steps to
lowering the pressure of reactor containment vessel has been taken. Spraying in order
to lower pressure level within the reactor containment vessel has been cancelled."

Ah but they don't actually say that it was canceled before it began. Its possible they canceled it once it was already in progress, because they were ready to use a different method.

Report to IAEA says spraying onto the PVC began at 07:39. At 08:41 they had opened AO valve, and at 09:08 operation to cause pressure reduction using SRV is mentioned, with a PCV pressure decrease trend noted at 09:20. By 09:25 they start injecting borated water via fire extinguishing line. (from table on page IV-81)

So I think its possible they sprayed the PCV for a short time, while they were waiting to get their valves in order.

The idea that this really happened is also mention on page IV-79 of the same document (http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/chapter_iv-3.pdf)

Regarding the progress of events in the accident at Unit 3, previous analyses showed that the RCIC and HPCI ceased to function, so PCV spraying using fire engines and wet vent operation were carried out.

 

[SteveElbows]

While it was mostly lost at the time, Daini did report a fire and some scary moments after the tsunami and quake.

It wasnt completely lost, it got its own evacuation zone at the time, so I think some people tried to pay attention to it because of that. I certainly followed the early reports, but information was even more limited in early days and of course once it was brought to cold shutdown while Daiichi was busy exploding, the spotlight really shifted.

So I don't think it was off the radar at the time it was having problems, but it has been mostly off the radar ever since, so we never got much sensible discussion about it and very little interesting data.

 

[Bioengineer01]

http://search.japantimes.co.jp/cgi-bin/nn20110606x2.html

Of course the next thing you will hear after any mention of plutonium is that it is lower than the amount from bomb tests, and probably came from old bomb testing.

If only there was some way to find out.



Oh my. From reactor one. Science, it doesn't care about what you believe.

Fukushima 1 doesn't mean Unit 1, but plant number 1 or what we call Fukushima Daiichi

 

[Bioengineer01]

The pressure vessel of reactor 3 was is measuring 181 degrees Celsius at 5:00 am (JST).

Here is the link as reported by TBS News (Japanese): http://news.tbs.co.jp/newseye/tbs_newseye4745702.html

The link reports a NOT FOUND error by the remote server

 

[Bioengineer01]

Apparently they reduced the flow of water from 18 to 11.5 tons per hour in the hope of delaying the trenches from overflowing, as they are running out of options until the water treatment plant is up and running, but the temperature in the reactor appeared to rise as a result.

It also says that they are facing a difficult judgement as to how much cooling water to pump as they try to balance the risk of overheating the reactor vs overflowing the basements - "燃料を冷やすための注水量について難しい判断を迫られることになります".

The article does not say which way TEPCO are leaning, except to point out that to let the reactor get too hot would be a 'dangerous state of affairs'.

If you were TEPCO, what would you do?

Keep it cool and allow overflowing. I can't see how it is not overflowing already a huge rates. The intentional overflow is only a political hazard

 

[Bioengineer01]

What we need is not just a geologist (like me) but a geologist that reads Japanese and can find the data.

A quick scan through the Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety June 2011 http://min.us/mvoVGLP appears silent on the matter of site geology. Maybe I missed it but a search on 'geology' got only one inconsequential result and there were no results on 'mudstone'.

Not for a final pass, but try using google translate as a first pass for searches. Then you can ask one of the Japanese/English Speakers here and in other forums to help

 

[robinson]

Fukushima 1 doesn't mean Unit 1, but plant number 1 or what we call Fukushima Daiichi

Probably. That doesn't answer the real question of course. Where in the plant did that plutonium come from? How did it get there?

Those would be important questions.

 

[StrangeBeauty]

Page IV-96 in the "Japanese Government report to the IAEA" shows an image that labels the large pipes that converge at the vent stack between Units 3 and 4, the "SGTS exhaust pipe junction".

http://www.kantei.go.jp/foreign/kan/topics/201106/iaea_houkokusho_e.html

Perhaps they are thinking that maybe the hydrogen flowed through the connecting pipe (about 200m of pipe all told) while the hydrogen was being produced and accumulating in Unit 3, and before Unit 3 exploded. Agree that it would be impossible for any hydrogen to travel through broken pipe after the explosion.

M&M thank you for the precise page number!

Im pretty convinced they are referring to the smaller pipes. Just look at exactly where they are highlighting the joining of the pipes from reactor 3 & 4, its well underneath the large pipe. Easy to miss because the join is the same shape as the larger pipe, and these other pipes are so small that its hard to see, but the yellow arrows are following the route of the smaller pipes round the outside of reactor 4 so I stick to this view.

Yes, if you zoom way in, it is clearly the smaller pipes below, and the yellow arrows indicate where they travel along the side of the outbuilding of #4. Looking the other way, it appears that going toward #3 they almost immediately go underground. In any case it's difficult to discern whether the pipes are intact or not, but shows that tepco's explanation isn't impossible (from the data we currently have at least). It still seems to me that the explanation of the hydrogen traveling between buildings is rather convoluted.

 

[StrangeBeauty]

It wasnt completely lost, it got its own evacuation zone at the time, so I think some people tried to pay attention to it because of that. I certainly followed the early reports, but information was even more limited in early days and of course once it was brought to cold shutdown while Daiichi was busy exploding, the spotlight really shifted.

So I don't think it was off the radar at the time it was having problems, but it has been mostly off the radar ever since, so we never got much sensible discussion about it and very little interesting data.

Most recent JAIF report on Daini:
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1307247746P.pdf

Of relevant interest within:

Latest Monitor Indication: 1.6μSv/h at 09:00, June 4th at NPS border
Evacuation Area: 3km from NPS(3/12 7:45), 10km from NPS(3/12 17:39), 8km from NPS(4/21)

Appears there is still an 8km evac area around the plant.
Interestingly, units 1,2 and 4 are at INES level 3, while #3 is not any level (no problems).

Side note: it appears they've dropped that format for a new one that only refers to Daiichi:
http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1307518788P.pdf

I too am wondering how the Pu got so far away from Daiichi. The town is approximately WSW from the plant which doesn't fit with wind direction for either the #1 (SE) or #3 (W) explosions (should be an E or ENE wind). Did the #3 explosion propel Pu 1.7 km against the wind?

 

[ascot317]

Which once again points out how unfortunate it is that we are lacking a poster knowledgeable of the subject of geology.

It simply can't be true that the underground rock formations, water tables and streams at the Fukushima site are an unknown.

Somebody did the engineering for that dam.

Cryptome.org posted some Japanese pdfs about the construction of Fukushima Daiichi.

It looks like there is information about the underground rock layers in it.

http://cryptome.org/0004/daiichi-build-01.pdf
http://cryptome.org/0004/daiichi-build-02.pdf