Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Jorge Stolfi]

Hey Madder, the chances of a ballistic object landing in that configuration, parallel with anything and just a foot away from a wall,... and not deforming it's shape are quite frankly near zero.

If the object fell in that part of the roof, it probably rolled about until it hit the wall. That would account for its position.

As for deformation, it depends on where it came from and how sturdy it is. For example, in the Air Photo Service pics one can see a large dark gray metal box that was ejected from Unit #3 and was lying on the ground, some 30 meters southwest of the building --- apparently intact.

 

[Rive]

This link shows a basic layout of the level circuit. 2 taps into the vessel connected to a differential pressure (DP) cell and transmitter. http://www.pbnc2010.org.mx/pdfs/technical/tuesday/14.00_ModelingLevelInstrumentation.pdf

The released TEPCO photo shows the techs at a whole panel of DP cells.
I don't think anyone knows for sure where these taps actually sense level in the RPV. Is the bottom tap in the shroud region or acually in the vessel itself (ie below the downcomer)??
It is also not clear if they blew back the sensing lines to make sure they were clear of any obstruction. They also should have pumped water back up to the upper condensate pot to ensure the reference leg was full. Without doing these 2 steps - the readings may still be wrong!

Well, a theoretical question. If it's not possible to trust those DP cells as water level indicators can they be turned to pressure meters of the RPV relative to the atmospheric pressure?

 

[Borek]

big stiff box that 'floats' on the soil/rock below. That way, if the ground cracks, deforms, liquefies, or shakes too much, the building may move or sink a bit but is less likely to crack or collapse.

In particular, I do not see any possibility of their lower levels sinking, tilting or collapsing to any significant extent, even if they were resting on top of soil rather than rock. Thus the tilting of #4 that is supposedly visible in the webcam --- and only there --- can only be an optical illusion or artifact.

The way I see it - if they float as rigid boxes, it is quite possible they can tilt without damage.

 

[rowmag]

ROWMAG, read my updated post as I provide a second english link in the "safety" section:

https://www.physicsforums.com/showpost.php?p=3306751&postcount=7594

Thanks, but the Japanese site does not mirror the English one at all. Really everything has been stripped away and replaced by disaster-related information.

 

[Jorge Stolfi]

The chunk has a very different appearence than on the other pictures I posted, where it looks clearly to be concrete, on this one it's not so clear but the rendering of the picture is bizarre. What is really surprising is the small amount of damages around or under it, like if it was delicately put there!

If it is the chunk I am thinking, then it is clearly one of the service floor wall panels --- some 5-7 meters across but perhaps only 30-40 cm thick. The following picture shows it clearly, and shows that it did bend the metal railings above the pipes. If it came from #4, its position and the lack of damage to the pipes are easy to explain. If it came from #3, it may have hit something else (such as the wall of #4 or of its turbine building) before landing there.

http://www.ic.unicamp.br/~stolfi/EX...isc4/drone/hires/aerial-2011-3-30-1-11-12.jpg
http://www.ic.unicamp.br/~stolfi/EX...isc4/drone/hires/aerial-2011-3-30-0-20-11.jpg

 

[tsutsuji]

IEEE Spectrum interviewed Tsuneo Futami, former superintendent of the plant, from 1997 to 2000 :

second concern is the strength of spent fuel pools’ reinforced concrete. Usually we have to keep the temperature inside the spent fuel pools under 60 degrees Celsius or so. A high temperature decreases the strength of reinforced concrete.
http://spectrum.ieee.org/tech-talk/...ale-of-the-accident-was-beyond-my-imagination

...

thanks

 

[ottomane]

I am following this thread now for a long time and I have to thank you all for the fantastic work done. I learned a lot about reactors and the thinks happening in Fukushima.

During the last days the situation has changed. Many expected this before, but now it is official: R1 and probably also R2 and R3 had full meltdowns with at least the core of R1 burning holes in and/or leaving the RPV (I guess the same must have happened to R2 and R3 too).

http://www.bbc.co.uk/news/world-asia-pacific-13423230"

Based on these news (to TEPCO this must be very old news) I would like to know what you think may happen now. Some things I read today in the net:

1. We may experience a China Syndrone as written by Time.com. Core will explode when hitting ground water soon. Or burns deep into Earth's crust triggering a volcano (wtf! I cannot believe this could happen).
2. The core drops at some day into the 3000t of water in the basement causing an explosion of several megatons distributing the core in a wide area. Maybe Japan (or more) will be inhabitable afterwards.
3. The core will stay in the basement and slowly cool down. H2 explosions are the only threat.
4. What else? What do you think will happen now?

From my understanding of the building design, the "lost" water is not directly located under the RPV and there is a concrete wall which may stop the corium from dropping into the basement. What do you think?

I know this is pure speculation, so please excuse me if this is the wrong place to ask. But finally we got some information we can use to extrapolate potential future scenarios.

 

[gmax137]

Siting plants at higher levels would not help for that aspect of a tsunami. Are power plants designed to handle the lows?

The cooling inlets may fall dry for 15 minutes, due to distant earthquakes that would not scram the reactor. Can a reactor at full power survive that?

Very interesting question.
The heat of vaporization is about 2000 joules/gram. So a 1 gigawatt plant at full cry would need to vaporize 3 gigajoules worth of water every second, or about 1.5 million grams of water, about 1.5 tons worth. The 15 minute dry spell would vaporize 1350 tons of water. That seems a manageable amount, about equal to the water quantity in SFP 4. No idea if the reactors are designed to have that much reserve capacity though.

Yes. Assuming loss of offsite power. Diesels will be tripped if they try to satrt without cooling water which will protect them during the drawdown period. The high pressure DC systems can inject cooling water for long enough for the drawdown period. At Fukushima that is the isolation condenser at unit 1 and the RCIC and HPCI systems at the other plants. If the water returns and the diesels are undamaged from the tsunami they can be started and then the low pressure AC systems will also be available. The Fukushima event made this scenario impossible due to failure to protect safety systems from the tsunami or from flooding.

An important thing to recognize is that the reactor would trip regardless of the distance to the earthquake - if the sea recedes from the intake area, then the large circulating water pumps that push the normal cooling water through the condenser would run dry, the condenser pressure would increase, and the turbine would trip. This loss of load would lead to a direct reactor trip, or if that failed to occur, then an indirect trip on high pressure in the reactor (among others). So, there is no need to boil off the full reactor power for more than a few seconds.

 

[SteveElbows]

Are you talking about the graph page 41/66 of http://www.tepco.co.jp/nu/fukushima-np/plant-data/f1_8_Parameter_graph.pdf ?

3 data are between 8 and 12 MPa, but it is difficult for me to read the date more precisely than sometime between March 18th and March 23rd.

I am interested in any interpretation of what happened at any unit late on March 20th or early in the morning on March 21st, because I am curious about the radioactivity peak recorded in Mito at 6 AM on the morning of March 21st, as in most cities in Eastern Japan on that date, which I believe is also connected to the "don't give tap water to babies" crisis in Tokyo during the following days (http://www.guardian.co.uk/world/2011/mar/23/tokyo-water-unsafe-infants ).

My previous posts on that topic :
https://www.physicsforums.com/showthread.php?p=3258585#post3258585 (with Mito 6 AM March 21st peak attachment)
https://www.physicsforums.com/showthread.php?p=3258806#post3258806 (about the gap in Tepco data)

For what it's worth, I posted about Kenichi Ohmae's somewhat isolated view of black smoke being something serious at https://www.physicsforums.com/showthread.php?p=3229089&highlight=Ohmae#post3229089

You can see the data in table form, where it is easy to read the exact values around March 21st.

However there is a problem. Yesterday Tepcos links to modern graphs, tables of data, and csv files did not just contain very recent data like they normally do, they were much larger and contained data going all the way back to before the 20th march. But today the same links have returned to their normal state, just showing data from recent days in may. So I cannot give you links to this information, maybe someone can reupload the data or find different urls?

Here is my post where I talked to someone about this new data yesterday, but as I said the links in it don't give the info I was talking about anymore :(

https://www.physicsforums.com/showpost.php?p=3305309&postcount=7502

In recent messages here I have been disagreeing with someone else about whether the smoke events of 21st march may be responsible for the increased radiation detected far away just a few hours later. I was blaming the weather. Well, I do not mean to sound so certain about this at all. Its only that I do not want to rule the weather out completely, because I checked messages I posted at a different forum around 19th-20th march to remind myself what was being said then. Stories were already appearing in the press about food and water contamination by the 19th march. And I posted messages with concern about the weather that was coming.

For example on March 19th at 21:53 JST I said on another forum:

I don't like the weather forecast and plume prediction models for the days ahead. It looks like wind is likely to be taking stuff inland and there is also rain for many places, especially on Monday. Will have to wait for newer readings from further afield to see if this shows up, certainly expect it to if any significant quantity of stuff is still escaping into the sky, which seems kinda likely.

Also, when I look at radiation data from the Fukushima plant itself, there had been spikes on dates such as 18th, so we should probably not be looking at the march 21st events in isolation. Its been a while since I looked at the radiation data from this time though, so I will look again soon to see if I have forgotten something.

 

[SteveElbows]

Many expected this before, but now it is official: R1 and probably also R2 and R3 had full meltdowns with at least the core of R1 burning holes in and/or leaving the RPV (I guess the same must have happened to R2 and R3 too).

Based on these news (to TEPCO this must be very old news) I would like to know what you think may happen now. Some things I read today in the net:

1. We may experience a China Syndrone as written by Time.com. Core will explode when hitting ground water soon. Or burns deep into Earth's crust triggering a volcano (wtf! I cannot believe this could happen).
2. The core drops at some day into the 3000t of water in the basement causing an explosion of several megatons distributing the core in a wide area. Maybe Japan (or more) will be inhabitable afterwards.
3. The core will stay in the basement and slowly cool down. H2 explosions are the only threat.
4. What else? What do you think will happen now?

From my understanding of the building design, the "lost" water is not directly located under the RPV and there is a concrete wall which may stop the corium from dropping into the basement. What do you think?

I know this is pure speculation, so please excuse me if this is the wrong place to ask. But finally we got some information we can use to extrapolate potential future scenarios.

If you follow thread for a long time then I am a bit surprised you have not read plenty here about China syndrome and some of the other doomsday core scenarios. The very silly China syndrome is almost universally laughed at, but other things like criticality, and how far the core may already have fallen are still open to debate.

Should also note that meltdown is not a precise technical term, so means different things to different people. Official story is still only at the stage where the fuel has all melted, but still remains in the reactor pressure vessel (even though it has made some holes in it). You are missing the next stage from your list, the core next has to fall into the containment vessel, and then melt through the containment vessel, before it gets to the concrete that you speak of. Until we learn more about how much of the core may have left the reactor pressure vessel, we should not skip ahead to thinking of it being in the basement.

Be especially careful with term 'full meltdown' because to some people full just means all fuel melted, but to others it may imply full meltdown through bottom of reactor vessel & then through drywell containment.

 

[TCups]

Have the recent large volume of new data released by TEPCO shed any further light on the questions of:
1) the possible origin of the explosion of Bldg 3 (ie, origin from the primary containment?), or
2) the nature of the radiation spike resulting from the explosion of Bldg 3 (ie, sudden criticality vs. some other mechanism of apparent littoral explosion in SFP3 with gamma shine)?

Apologies in advance for a busy schedule and relative lack of mental acuity for meaningful interpretation of the large volume of technical data on the reactors that was released. Thanks.

 

[SteveElbows]

What do people think of Tepcos roadmap update then? Several english documents available here:

http://www.tepco.co.jp/en/press/corp-com/release/11051703-e.html

TEPCO have made it sound like progress is going quite well. Spin aside, and to be fair, the documents remind us that there has actually been some real progress in certain areas. I was quite surprised to see that if I have read the document properly, fuel pool 3 has water injected through normal cooling system, for example.

http://www.tepco.co.jp/en/press/corp-com/release/11051703-e.html

Aside from that the main change is what we expected, reactor 1 plan to fill containment with water not yet completely erased from the roadmap, but the recirculation of water plan now takes priority at that reactor.

 

[ottomane]

If you follow thread for a long time then I am a bit surprised you have not read plenty here about China syndrome and some of the other doomsday core scenarios. The very silly China syndrome is almost universally laughed at, but other things like criticality, and how far the core may already have fallen are still open to debate.

I know that the China Syndrome in its basic idea is nonsense, but a core melting through the basement into some meters of Earth can not be ruled out, was my understanding so far.

Should also note that meltdown is not a precise technical term, so means different things to different people. Official story is still only at the stage where the fuel has all melted, but still remains in the reactor pressure vessel (even though it has made some holes in it). You are missing the next stage from your list, the core next has to fall into the containment vessel, and then melt through the containment vessel, before it gets to the concrete that you speak of. Until we learn more about how much of the core may have left the reactor pressure vessel, we should not skip ahead to thinking of it being in the basement.

Be especially careful with term 'full meltdown' because to some people full just means all fuel melted, but to others it may imply full meltdown through bottom of reactor vessel & then through drywell containment.

But: How can the core melt holes into the RPV without falling out afterwards at least partially?

 

[Caniche]

Spiffing .AOK Just as expected

 

[bill-green]

HEllo, Yes, the Russians learned a lot and should have been consulted earlier,... though as I understand it the mechanisms and type of cleanup needed are very different. There's a good vid on YT that says they eventually pumped Liq. N2 into the ground under the reactor,... and the evaporating N2 gas "put the fire out"
The corium there seems to have melted the sand they poured on and it cooled and solidified before reaching water table...
However the Russians had an open reactor, on which to dump sand.
I think not knowing the state of the three CORES here is the main problem... How can you know what to do... I hope modern reactors have a radiation proof camera looking at the state of the core incase this happens again.

Exactly and btw thanks for your reply.

I'm not a nuclear engineer, but read a lot about Chernobyl, after the fukishima accident and how close they/we were (Chernobyl) to an even bigger incident, that eventually transpired.

The whole of northern Europe uninhabitable type of incident. IF the corium core had hit the water table.

They took drastic measures to ensure this didn't happen and were succesful.

Is this type of incident a possible scenario in this case or is there not enough information to conclude.

Thanks

 

[bill-green]

Forgive me I should read the latest posts before posting as my questions have already been asked and somewhat answered
Thanks for all the info here and take care all

 

[MadderDoc]

Have the recent large volume of new data released by TEPCO shed any further light on the questions of:
1) the possible origin of the explosion of Bldg 3 (ie, origin from the primary containment?),

We had reasons to believe that the primary containment was, or got, involved also before we had these additional data, With the extra data we have just more reason to believe so. I do not think data can point to the origin of the explosive event. It remains a possibility that the origin could have been somewhere else, and the excursion from the primary containment was a secondary effect.

or
2) the nature of the radiation spike resulting from the explosion of Bldg 3 (ie, sudden criticality vs. some other mechanism of apparent littoral explosion in SFP3 with gamma shine)?

CAMS readings are absent in the dataset, from shortly before the explosion and until 3 days after, so we can still say nothing about the effect it may have had on those readings.

 

[MadderDoc]

>..>
I am interested in any interpretation of what happened at any unit late on March 20th or early in the morning on March 21st, because I am curious about the radioactivity peak recorded in Mito at 6 AM on the morning of March 21st, as in most cities in Eastern Japan on that date<..>

I think it is fair to say that the new data set indicates an untoward event occurring in unit 3 about 2am on March 21st. This is something we have been so far completely oblivious about. It happened during the nighttime, so there's no imagery of the event, and for the relevant period of this event, we also had no access to data until now.

 

[SteveElbows]

Have the recent large volume of new data released by TEPCO shed any further light on the questions of:
1) the possible origin of the explosion of Bldg 3 (ie, origin from the primary containment?), or
2) the nature of the radiation spike resulting from the explosion of Bldg 3 (ie, sudden criticality vs. some other mechanism of apparent littoral explosion in SFP3 with gamma shine)?

The main problem with the data and these questions is the time period that the data covers. There were 2 important releases of data in recent days.

One set filled in some gaps at various times later on, for example around 18th-19th march onwards when they managed to switch on lots of additional temperature sensors at reactor 3. We already had a lot of this data but some corrections were made and some gaps were filled in, but I think this was more notable for reactor 2 at an earlier time period, think I mentioned this yesterday.

The other set was a large quantity of data about lots of reactor parameters during the earthquake and in the hour or so that followed afterwards. So this data is from too early a period to tell you about the explosions. Its probably of most interest to those who want to see how water levels and emergency systems responded to the earthquake and tsunami. Press stories indicate that the data shows the emergency cooling at reactor 1 being turned off. But there is also data showing what things such as the RCIC were doing in the first hour or so. Problem with much of this data is we need to know what happened in the many emergency hours that followed, but this data is not available.

 

[NUCENG]

An important thing to recognize is that the reactor would trip regardless of the distance to the earthquake - if the sea recedes from the intake area, then the large circulating water pumps that push the normal cooling water through the condenser would run dry, the condenser pressure would increase, and the turbine would trip. This loss of load would lead to a direct reactor trip, or if that failed to occur, then an indirect trip on high pressure in the reactor (among others). So, there is no need to boil off the full reactor power for more than a few seconds.

Thanks, that is a good amplification on my post. I should have covered the trip.

 

[razzz]

Sure you could build a floating box with 20 foot thick walls all around, doesn't mean it can't be shaken. Do you want to put your really thick walled floating box on sand or solid rock? See the difference yet?

 

[SteveElbows]

I think it is fair to say that the new data set indicates an untoward event occurring in unit 3 about 2am on March 21st. This is something we have been so far completely oblivious about. It happened during the nighttime, so there's no imagery of the event, and for the relevant period of this event, we also had no access to data until now.

To be honest it is not true that data about this event was new to us yesterday. Plenty of people had likely seen some of this data in graph form already, although it may not have been noticed because of the larger messy temperature etc picture seen on reactor 3 graphs both before and after 21st. And the data that showed huge pressure spike from one sensor at 01:25, 01:45 and 02:30 had certainly been seen before by some people on this forum, because someone found old version of this data on the internet and posted about it here a while back, but again I am not sure if anyone noticed the pressure spike early on 21st march.

The problem I still have with this event is that there are no interesting changes to CAMS readings around this period, and simply because there was so much going on during the week of the 20th march that it is hard to know what to rule out. I have already talked about weather, and I believe tepco webcam archive images from around 20th will show that it rained on site. They had been connecting power up to various things at various reactors. When they got temperature sensors working at reactor 3 around 19th march, they saw scary temperatures and I think they implemented additional cooling within a few days. And by the end of the week we heard about basement water at reactor 3 because workers trod in it. And even now I think I am missing out plenty more things that happened that week.

Im not trying to dismiss the march 21st event, but given these things, and the fact that there also seemed to be spikes in radiation levels on site in the days before 21st, we should not try to look at this event in relative isolation. Its not so easy because as mentioned the interesting temperature measurements are unavailable until 19th march, so there is a gap in our knowledge about key early days of problems at reactor 3.

 

[I_P]

This, elektrownik, is a most interesting document. It includes far more datapoints than I have seen before, including during the most interesting moments. I've previously estimated the pressure drop within the containment during the explosion of unit 3 to be >=0.1 MPa. Based on this document, the estimate of DW pressure drop must be revised to >=0.4MPa.

It is also news to me from this document, that the RPV during the period of the 'black smoke event' on March 21st briefly peaked out at >12MPa, before it dropped back abruptly and went down to to atmospheric. My,my.

I think it is fair to say that the new data set indicates an untoward event occurring in unit 3 about 2am on March 21st. This is something we have been so far completely oblivious about. It happened during the nighttime, so there's no imagery of the event, and for the relevant period of this event, we also had no access to data until now.

At the time (20th) TEPCO said that they were considering venting unit 3 due to rising pressure. Later they said that the situation had resolved itself and they didn't need to vent... Yes, of course they didn't because the pressure dropped to atmospheric after the 'resolution', whatever it was.

 

[MadderDoc]

Hey Madder, the chances of a ballistic object landing in that configuration, parallel with anything and just a foot away from a wall,... and not deforming it's shape are quite frankly near zero.

That's a perfect non-argument. The a priori chances of its landing in _any_ particular configuration is near zero.

C'mon... it was installed there before anything happenned.

Why do you think so?

 

[SteveElbows]

But: How can the core melt holes into the RPV without falling out afterwards at least partially?

Its a good question. I am not sure if TEPCO have tried to answer it, but from everything I have read this seems to be the position they currently take on this matter, as talked about a lot in the news at the weekend.

It maybe that they actually mean that most of the core is still in the reactor pressure vessel, and that they do not exclude possibility that a little bit of it escaped.

It could be that they mean very tiny holes. Or holes that are above the level where the corium now lives, but still low enough down that water they pump in escapes.

Or some combination of the above in conjunction with the idea that the corium didnt melt the reactor vessel itself, but rather something that is normally connected to the reactor pressure vessel, but melts more easily, and leaves a gap where it was before it melted.

I assume the main reason we don't hear far more talk about the core no longer being in the reactor, is the temperature levels of the reactor vessels. They are still hot, so we assume something is still there to heat them. But this is far from my area of expertise so other people could say better about this stuff.

 

[RealWing]

Siting plants at higher levels would not help for that aspect of a tsunami. Are power plants designed to handle the lows?

The cooling inlets may fall dry for 15 minutes, due to distant earthquakes that would not scram the reactor. Can a reactor at full power survive that?

Are you referring to the pre-tsunami event where the sea level receeds - or a different event that causes a drop in sea level at the cooling water intakes?

In either scenario, if the water level drops at the cooling water intakes, the pumps will likely trip on low suction levels (if so equipped) or just stop pumping. This will quickly cause a loss of the turbine condenser cooling water flow, condenser vacuum quickly deterorates and causes a turbine trip which cross trips the reactor.

In other words, a low sea level will result in a fairly quick reactor trip. Then one has to deal with decay heat via RCIC or isolation condensers.

 

[MadderDoc]

If the object fell in that part of the roof, it probably rolled about until it hit the wall. That would account for its position.

As for deformation, it depends on where it came from and how sturdy it is. For example, in the Air Photo Service pics one can see a large dark gray metal box that was ejected from Unit #3 and was lying on the ground, some 30 meters southwest of the building --- apparently intact.

I'd be grateful if you'd point it out on a photo. To understand the explosion it is potentially useful to look at fragments ejected.

As regards the grey cylinder, in this video , right at the end, there is a brief sequence showing a firetruck spraying water to the roof, apparently in the direction of the object (two frames are attached, one before, and one after the firetruck starts spraying.

I ask forgiveness for presenting you to a video of this low quality, it is horrible, but it is the only source I know of which includes this particular sequence.

The video starts out with a brief sequence from the helicopter video shortly after the tsunami. There are better sources for this sequence.

The rest of the video appears to have been made by someone with the Tokyo Fire Department Hyper Rescue Unit. It shows bits and pieces of the emergency response at unit 3 of the Hyper Rescue Unit, around midnight between March 18 and March 19. The bits and pieces are timestamped throughout.

Parts of this sequence have better sources, but this source contains a few sequences which are not included there (in the sequence in which the photographer sits tight in the dark, in an apparently high radiation environment, with his camera showing a multitude of variations of radiation blips on the otherwise mainly dark background.)

Finally there is this brief sequence at the end, in which we see one of the trucks of the Hyper Rescue Unit spraying water to the roof close to the grey cylinder. The timestamp for this sequence is March 19 14:08.

 

[RealWing]

Well, a theoretical question. If it's not possible to trust those DP cells as water level indicators can they be turned to pressure meters of the RPV relative to the atmospheric pressure?

Not really. Level transmitters are designed and calibrated to sense a differential pressure of a few cm's or meters of water. To measure actual pressures of many Kpa or Mpa, you need a different transmitter with a much larger range.

They have several separate lines running into the reactor vessel to measure pressure via pressure transmitters..

 

[MadderDoc]

At the time (20th) TEPCO said that they were considering venting unit 3 due to rising pressure. Later they said that the situation had resolved itself and they didn't need to vent... Yes, of course they didn't because the pressure dropped to atmospheric after the 'resolution', whatever it was.

Please, can I ask of your source of this information?

 

[jlduh]

If it is the chunk I am thinking, then it is clearly one of the service floor wall panels --- some 5-7 meters across but perhaps only 30-40 cm thick. The following picture shows it clearly, and shows that it did bend the metal railings above the pipes. If it came from #4, its position and the lack of damage to the pipes are easy to explain. If it came from #3, it may have hit something else (such as the wall of #4 or of its turbine building) before landing there.

http://www.ic.unicamp.br/~stolfi/EX...isc4/drone/hires/aerial-2011-3-30-1-11-12.jpg
http://www.ic.unicamp.br/~stolfi/EX...isc4/drone/hires/aerial-2011-3-30-0-20-11.jpg

This is this one but how do you interpret this view from the south from where the thickness seems huge:

http://www.netimago.com/image_201109.html

EDIT: hummm i think i got trapped by an optical illusion when i viewed it from this side... What i interpreted as thickness was in fact length seen from perspective angle i think!

The quality of your images seems better than mine and now i see better the shape of this object which is not so thick than i saw it. Damn optical illusion

 

[Dmytry]

1. We may experience a China Syndrone as written by Time.com. Core will explode when hitting ground water soon. Or burns deep into Earth's crust triggering a volcano (wtf! I cannot believe this could happen).

1. 
   this could not. absolutely impossible. When core melts through stuff, it dilutes. This is case of stupid abstract thinking by media. Reactor core. A core, something hard, that stays itself.
   Reality: molten corium, of low thermal conductivity, mixes up with stuff, dilutes, the heat output decays, etc. Hitting ground water, another dumb abstraction. Water content in the soil increases gradually, the material in question (corium lava) has low thermal conductivity, and freezes on contact. The giant steam explosion is a concern if a lot of it falls literally into a body of water at once. Otherwise you simply do not get heat transmission rate enough to explode anything. Even if it literally falls into water it might not explode. Indeed it did fall into water once, when the water ran below the fuel level - and remained there, corium falling into it.

 

[MadderDoc]

<..>the data that showed huge pressure spike from one sensor at 01:25, 01:45 and 02:30 had certainly been seen before by some people on this forum, because someone found old version of this data on the internet and posted about it here a while back, but again I am not sure if anyone noticed the pressure spike early on 21st march.

Perhaps you can dig up a link to the data to which you make reference. It would be interesting to correlate it with this present dataset.

The problem I still have with this event is that there are no interesting changes to CAMS readings around this period, and simply because there was so much going on during the week of the 20th march that it is hard to know what to rule out.

Well, not all events in a wrecked NPP would affect CAMS readings, I reckon.

I have already talked about weather, and I believe tepco webcam archive images from around 20th will show that it rained on site.

Not really. Neither the evening shots of the webcam from March 20th nor the morning shots on March 21st indicate any rain. At the time of the event itself it was of course dark night, and there is no data from the webcam.

They had been connecting power up to various things at various reactors. When they got temperature sensors working at reactor 3 around 19th march, they saw scary temperatures and I think they implemented additional cooling within a few days.

During this period it appears several hefty and dangerous missions to control unit 3 was done by first the Japanese Defence Force, then the Hyper Rescue Unit of the Tokyo Fire Department using firetrucks and fire hoses.

At the time of the apparent event in unit 3 around 2 am on March 21st, according to Tepco press releases, the Hyper Rescue Unit would have been in action at unit 3:
"At approximately 9:30 pm, March 20th, spraying water was started with the
cooperation of Fire Rescue Task Forces of Tokyo Fire Department. At
approximately 4 am, March 21st, they finished the operation."

 

[NUCENG]

This link shows a basic layout of the level circuit. 2 taps into the vessel connected to a differential pressure (DP) cell and transmitter. http://www.pbnc2010.org.mx/pdfs/technical/tuesday/14.00_ModelingLevelInstrumentation.pdf

The released TEPCO photo shows the techs at a whole panel of DP cells.
I don't think anyone knows for sure where these taps actually sense level in the RPV. Is the bottom tap in the shroud region or acually in the vessel itself (ie below the downcomer)??
It is also not clear if they blew back the sensing lines to make sure they were clear of any obstruction. They also should have pumped water back up to the upper condensate pot to ensure the reference leg was full. Without doing these 2 steps - the readings may still be wrong!

See RG 1.97 for requirements for Post-Accident Monitoring Instrumentation at US Nuclear plants (Rev 3 is the latest version that included the required ranges):
http://adamswebsearch2.nrc.gov/idmws/DocContent.dll?library=PU_ADAMS^pbntad01&LogonID=104a5533b05307c56d262f6d365c76e8&id=003957314

Table 2 BWR Variables
Coolant Level in Reactor Vessel
Required Range.
Bottom of core support plate to lesser of top of vessel or centerline of main steam line.

For post- accident monitoring instrumentation, I checked one BWR3 and one BWR 4 in the US. Both of these plants have instrument taps about 150 cm below the steam nozzle centerlines and a lower tap near the bottom of the core shroud well below the core support plate. The fact that the highest tap is below the nozzle centerline is of no consequence in a Fukushima-type event.

These water level instruments are Category 1 per RG 1.97 and are qualified seismically and environmentally for design basis accidents. Both plants have keep-fill systems that will maintain the reference legs filled. Every US plant has made submittals of the design , qualification, and quality controls for their Post-Accident Monitoring Programs. These submittals have been reviewed and approved by NRC and are subject to periodic inspections by NRC inspections.

Again, I cannot say for certain whether Japan has similar requirements, however, this all came out of TMI2 and Japan did implement many of the Post-TMI Lessens Learned.

 

[jim hardy]

But: How can the core melt holes into the RPV without falling out afterwards at least partially?

there's a Oak Ridge study about that at
http://www.osti.gov/bridge/servlets/purl/6124656-R8y05j/6124656.pdf

it's linked someplace earlier in this long, long thread I'm not first.

basically the rods and instrument tubes penetrate the vessel bottom through stub tubes to which they are in turn welded. The rod stub tubes stick up a ways, instruments are welded right at inside bottom.

there's sketches around page six.

I remember hearing in a press release that some of (which unit? i forget)'s rod mechanisms were observed down against their mechanical stop, meaning they are detached on the inside as expected. The mechanical stop is there to keep them from falling all the way out in case they do detach..

 

[SteveElbows]

Please, can I ask of your source of this information?

Official english TEPCO documents that contain history of things says:

Since 6:15am, March 17th, the pressure of the Suppression Chamber temporarily increased, on March 20th, we were preparing for implementing measures to reduce the pressure of the reactor containment vessel (partial discharge of air
containing radioactive material to outside) in order to fully secure safety. However, at present, it is not a situation to immediately implement such measures and discharge air containing radioactive material to outside. We will continue monitoring the status of the pressure of the reactor containment vessel.

Sorry I don't have link to document handy right now. But it also says things about spraying operations you just mentioned,with more detailed timing. These come from the section dealing with spraying of seawater into spent fuel pool at reactor 3.

From approx. 9:30am to past 10:00am, March 17th, water was sprayed by helicopters upon our request for the cooperation to Self-Defense Forces.
- From approx. 12:30am to 1:10am, March 19th, water was sprayed with the cooperation of Fire Rescue Task Forces of Tokyo Fire Department. They resumed the operation from approx. 2:10pm to 3:40am, March 20th.
- From approx. 9:30pm, March 20th to 3:58am, March 21st, water was sprayed with the cooperation of Fire Rescue Task Forces of Tokyo Fire Department.
- From approx. 3:10pm to 3:59pm, March 22nd, water was sprayed with the cooperation of Fire Rescue Task Forces of Tokyo Fire Department.
- Sea water was injected through Fuel Pool Cooling and Filtering System; From approx. 11:03am to 1:20pm on March 23rd From approx.5:35am to 4:05pm on March 24th

 

[ernal_student]

Sorry I don't have link to document handy right now.

Maybe this one? It has an odd URL, though - not original TEPCO

http://www.tepco.co.jp.cache.yimg.jp/en/press/corp-com/release/betu11_e/images/110506e2.pdf

 

[SteveElbows]

Perhaps you can dig up a link to the data to which you make reference. It would be interesting to correlate it with this present dataset.

I found the post on this thread where these older documents were rediscovered:

https://www.physicsforums.com/showthread.php?p=3291191&highlight=google#post3291191

As for comparing it with new version of data, one version of the data released just the other day showed which entries were new by putting them in blue. These were what I quickly skimmed over in order to conclude that most pertinent new info was about a certain key time at reactor 2, but that I may have missed other important new aspects. Do have to be careful in a few places though because for at least one reactor not all the reactor pressure readings that are in blue are really new, rather they seem to have swapped round the A and B readings that were previously published, and so that's why the data is classed as new.

Well, not all events in a wrecked NPP would affect CAMS readings, I reckon.

True, its just in particular at 01:25 on 21st I would have liked to see even more data that could lead us neatly to a theory, and the CAMS does not help in this case, especially as much like the temperature data they only started getting it again a few days before the 21st so can't see moment that CAMS levels first shot up, there is a gap.

Not really. Neither the evening shots of the webcam from March 20th nor the morning shots on March 21st indicate any rain. At the time of the event itself it was of course dark night, and there is no data from the webcam.

Well bear in mind that I have indicated that I am looking at a wider period of time, not just restricting myself to 01:25 on that day. But even so I am not sure what webcam images you are looking at, because I look at the archive for March 21st and very quickly it shows what looks like raindrops on camera lens cover.

http://gyldengrisgaard.dk/tepcowebcam/tepweb20110321.html

During this period it appears several hefty and dangerous missions to control unit 3 was done by first the Japanese Defence Force, then the Hyper Rescue Unit of the Tokyo Fire Department using firetrucks and fire hoses.

As hinted at in my previous post, its not safe to characterise these JDF missions as being about the reactor, but rather the fuel pool. In theory its possible that it was to do with reactor and they never told anyone, but we would need better evidence to lead us in that direction.

 

[NUCENG]

Interesting, thanks for sharing. That seems like very solid data, I mean it comes from the official "Japanse Geospatial Information Authority of Japan (GSI)" site after all (link from ex-skf's blog entry: http://www.gsi.go.jp/chibankansi/chikakukansi40005.html ).

And it comfirms what some people have mentioned on this forum based on the TEPCO webcam pictures.

Thinking of those pictures of that road and the pictures from the New Zealand quake, it's good that at least there was no crack and horizontal offset in the ground right through the site of the power plant.

At lunch today I spoke with a college geology professor who tried to explain this to me. Hopefully I won't confuse everybody further. The area just off the Japanese east coast is a subduction zone where the pacific geological plate is diving down underneath the asian plate. As the pacific plate tries to move to the west over time it builds up pressure which tries to move Japan to the west and also pushes it upward. When the quake hit the two plates slipped and the result was that Japan moved to the east as the pressure was relieved and also dropped vertically.

Japan is riding on top of two plates. As the Pacific plate gets deeper and melts beneath Japan some of it rises through cracks above to fuel Japan's volcanos. Japan is apparently not in any danger of sinking, but it is likely to get shaken up periodically and may experience further problems from volcanos.

 

[MadderDoc]

Maybe this one? It has an odd URL, though - not original TEPCO

http://www.tepco.co.jp.cache.yimg.jp/en/press/corp-com/release/betu11_e/images/110506e2.pdf

"Since 6:15am, March 17th, the pressure of the Suppression Chamber temporarily
increased, on March 20th, we were preparing for implementing measures to
reduce the pressure of the reactor containment vessel (partial discharge of air
containing radioactive material to outside) in order to fully secure safety. However,
at present, it is not a situation to immediately implement such measures and
discharge air containing radioactive material to outside."

It is clear this is a poor translation of a text in Japanese, which I am sure originally made perfect sense.

As it stands, it appears to be saying that S/C pressure was seen as a problem due to pressure readings on March 17th. (D/W and S/C pressure readings on March 17th at our present state of knowledge do not clearly show which S/C readings could have caused this concern. The DW/SC readings for this period appear incomplete, confusingly unstable, and/or implausible.

Anyhow, due to this concern, it appears, Tepco would have liked to vent, and had anticipated that such a measure could be implemented on March 20th. It may be implied here that conditions at the reactor did not allow this to be done earlier, and from what else we know that may very well have been the case, whatwith all the douching with helicopters and firetrucks and hoses to the top of the wrecked reactor building.

The last statement, I do read it as saying that the present conditions at unit 3 on March 20th doesn't allow venting to be done (one would have to wait a bit longer than anticipated) -- however alternatively it seems to me the statement can perfectly well be read as saying that present conditions at unit 3 on March 20th no longer makes the measure necessary to implement immediately.

 

[Astronuc]

At lunch today I spoke with a college geology professor who tried to explain this to me. Hopefully I won't confuse everybody further. The area just off the Japanese east coast is a subduction zone where the pacific geological plate is diving down underneath the asian plate. As the pacific plate tries to move to the west over time it builds up pressure which tries to move Japan to the west and also pushes it upward. When the quake hit the two plates slipped and the result was that Japan moved to the east as the pressure was relieved and also dropped vertically.

Japan is riding on top of two plates. As the Pacific plate gets deeper and melts beneath Japan some of it rises through cracks above to fuel Japan's volcanos. Japan is apparently not in any danger of sinking, but it is likely to get shaken up periodically and may experience further problems from volcanos.

Japan and Indonesia are somewhat unique, which has to do with a convergent boundary and the smaller plates involved.

http://pubs.usgs.gov/gip/dynamic/zones.html
http://earthquake.usgs.gov/learn/topics/plate_tectonics/plates.php

http://en.wikipedia.org/wiki/Plate_tectonics

The western side of the Pacific Ring of Fire (Pacific and Asia plate intersection and Australia and Pacific plate intersection) and the Sunda extension (Australia and Asia plate intersection) have become particularly active in the last decade.

 

[jlduh]

Some informations that you know already maybe about the flaws of the Mark I design, from an article that summarizes the history of mark I containment and some old studies (not sure they are available on the net anyway) which made this design very controversial:

http://www.nytimes.com/2011/03/16/world/asia/16contain.html

Several utilities and plant operators also threatened to sue G.E. in the late 1980s after the disclosure of internal company documents dating back to 1975 that suggested that the containment vessel designs were either insufficiently tested or had flaws that could compromise safety.

See also this document hyperlinked in the article, which criticizes the technology used by GE in order to reduce size of containment and ultimately cost:

http://graphics8.nytimes.com/images/blogs/greeninc/hanauer.pdf

And you have also an interesting page, PAGE 63, in this document, where are compared with curves the abilities of different containments to absorb a sudden Hydrogen production from Zr oxydation, and Mark I is far behind the other ones (high percents of H2 inside the containment are reached much quicker, increasing risks of explosion...)

http://www.galcit.caltech.edu/~jeshep/fukushima/ShepherdFukushima30April2011.pdf

These reactors have been through some retrofit to improve the flaws but it is unclear right now which ones are implemented at Daichi (the hardened venting seems part of this, also some deflectors in the torus?)

But still retrofit has its limits of course...

 

[MadderDoc]

I found the post on this thread where these older documents were rediscovered:

https://www.physicsforums.com/showthread.php?p=3291191&highlight=google#post3291191

Disappointingly this dataset does not appear to include data for the pressure peak during the early hours of March 21st. (I inferred from your previous words that it did.)

<..> in particular at 01:25 on 21st I would have liked to see even more data that could lead us neatly to a theory, and the CAMS does not help in this case <..>

Well, one would always like to have more data

Well bear in mind that I have indicated that I am looking at a wider period of time, not just restricting myself to 01:25 on that day. But even so I am not sure what webcam images you are looking at, because I look at the archive for March 21st and very quickly it shows what looks like raindrops on camera lens cover.

http://gyldengrisgaard.dk/tepcowebcam/tepweb20110321.html

I think it risks confusing things for everybody to take observations over several days in one stew. The whimpering demise of unit 3 after the explosion might be describable as a series of events that could better be approached independently, than as included in a 'grand unified theory' of 'what happened'.

As hinted at in my previous post, its not safe to characterise these JDF missions as being about the reactor, but rather the fuel pool. In theory its possible that it was to do with reactor and they never told anyone, but we would need better evidence to lead us in that direction.

I do apologize if I have used such sloppy language and characterised any JDF missions as being about the reactors.

It is clear from video evidence, that the building was douched with water from the sky using helicopters, and was douched from the ground at its north, west, and south side, and that some of that douching neither targeted nor significantly hit the spent fuel pool.

 

[Astronuc]

It is clear from video evidence, that the building was douched with water from the sky using helicopters, and was douched from the ground at its north, west, and south side, and that some of that douching neither targeted nor significantly hit the spent fuel pool.

The spray from the helicopters and ground was directed at the SFPs. The spray from the helicopter was ineffective with respect to the SFP, although it might have suppressed any fire.

Before the top of Unit 4 came off, the helicopter spray would have been useless inside containment. Hence the concrete pump truck on the south side of the building.

 

[jlduh]

This shows that things are more complex in real life than on paper...

Generator trucks proved useless at Fukushima plant

http://www3.nhk.or.jp/daily/english/17_11.html

The operator of the stricken Fukushima Daiichi nuclear plant says dozens of power-generating trucks brought to the plant just after the March 11th disaster mostly proved to be useless.About 70 generator trucks from the Self-Defense Forces and other entities headed to the plant after the quake knocked out external power and the tsunami disabled the facility's backup generators.

But plant operator TEPCO says debris strewn across the compound and flooded switchboards hampered the trucks' set up.The utility says a switchboard for the No.2 reactor was finally wired to one of the generator trucks about 24 hours after the disaster.
But moments later, a hydrogen explosion at the neighboring No.1 reactor fried the wiring and cut off the power supply from the truck.

Another hydrogen explosion 2 days later at the No.3 reactor damaged generator vehicles with chunks of flying concrete.Electricity was finally restored to the plant through the regular power grid on March 21st -10 days after the quake and tsunami.

 

[Astronuc]

These reactors have been through some retrofit to improve the flaws but it is unclear right now which ones are implemented at Daichi (the hardened venting seems part of this, also some deflectors in the torus?)

But still retrofit has its limits of course...

It is my understanding with information provided by others, that the FK units with MkI containment did not have the various retrofits applied in the US.

 

[jlduh]

It is my understanding with information provided by others, that the FK units with MkI containment did not have the various retrofits applied in the US.

Ok thanks. I think the list of these retrofits in US is like described in this document, right?

http://www.nrc.gov/reading-rm/doc-collections/gen-comm/gen-letters/1989/gl89016.html

I'm still trying to find an accurate description and drawing of what this hardened venting (enabling it seems direct venting from primary containment to environment) looks like. I read somewhere that some venting -like the illustration below- was placed in the Torus, but this is secondary containment.

http://www.netimago.com/image_201117.html Does hardened venting means direct venting from primary (so with pressures much higher)?

 

[MadderDoc]

The spray from the helicopters and ground was directed at the SFPs.

Yes, largely speaking. However, in the case of unit 3, we do have videos showing firetrucks targeting the north end of the building, while the SFP is situated in the south end of it.

The spray from the helicopter was ineffective with respect to the SFP, although it might have suppressed any fire.

It probably did not have much effect, no, but in the context of the situation, it is quite understandable that the attempt was made. There was not much else to do either. It came at a time, when unit 3 had most recently acted out in such obnoxious fashion that it must have looked as prohibitively risky business to get close to it.

 

[jlduh]

Also, of interest, i put this article on "passive cooling" (no external power required to cool the reactor).

http://motherjones.com/blue-marble/...chnology-safer-not-always-japans-crisis-shows

BWR3 reactors are of this type, and number 1 unit is a BWR3 (that's why it has a different cooling principle than the others, that we just learned Tepco workers have possibly volountarily turned off after Tsunami and shutdown, in a procedure to "protect" the reactor).http://www3.nhk.or.jp/daily/english/17_22.html

The operator of the Fukushima Daiichi nuclear power plant says workers may have manually shut down the No.1 reactor's emergency cooling system in order to prevent damage to the reactor. It says pressure inside the reactor had dropped sharply after the earthquake struck the plant on March 11th.

The system is designed to cool the reactor even if all external sources of power are lost, but the move to shut it down temporarily means that it did not fully function.TEPCO says the decision may have been made based on a manual to prevent damage to the reactor. It says if the system had worked, it may have had more time until the meltdown, so it will investigate developments leading up to the decision to turn it off and whether the move was correct.

 

[ThomS]

I have been watching the Live cam some this morning here and noticed that there is some smoke or steam coming from Plant 2. Not much, but still...

Edit: First noticed (saw) at 09:29am Local time. Now at 10:38 am, it is sporadic with occasional small plumes.

 

[Astronuc]

Ok thanks. I think the list of these retrofits in US is like described in this document, right?

http://www.nrc.gov/reading-rm/doc-collections/gen-comm/gen-letters/1989/gl89016.html

I'm still trying to find an accurate description and drawing of what this hardened venting (enabling it seems direct venting from primary containment to environment) looks like. I read somewhere that some venting -like the illustration below- was placed in the Torus, but this is secondary containment.

http://www.netimago.com/image_201117.html


Does hardened venting means direct venting from primary (so with pressures much higher)?

These are the major mods in the US.
http://resources.nei.org/documents/japan/major_mod_usbwr_4511.pdf

It's not clear if they were implemented in Japan.