Japan Earthquake: nuclear plants

razzz

Meltdowns also likely occurred at No. 2, No. 3 reactors of Fukushima plant

Worker Enter Reactor 2

The workers wear a "tungsten vest" to prevent external radiation exposure. They also carry oxygen tanks on them.

Entergy Tungsten Shielding Innovation Sent to Japan

In fact, tungsten shielding was recently sent to Japan for use in their current incident at Fukushima.

Jim Bacquet, radiation protection supervisor and project team leader, said, “Now that it has gone to Japan, it continues to be a real team success story. Because of the flexibility of the material and embedded magnets, we call it the ‘snap-on-snap-off shield because it attaches easily in the field. It is lightweight and so versatile – we even have tungsten duct tape for small spaces. The effectiveness overall is unmatched as we can maximize weight at a source, cut it in the field, lay a tungsten sheet for flooring if needed and, of course, there is the tungsten vest. Our team wears tungsten vests and gains protection we never had prior.”

Tons of tungsten shielding blankets and sheets along with 160 tungsten vests have been sent to Fukushima to date.

MadderDoc

Quote by rowmag

I'm not sure they were targeting the north end of the building.

In the video from which this frame is from, the waterspray hit the north end
and the spray was also directed towards that end of the building. It does not look at all like a failed attempt to reach the sfp.

MadderDoc

Quote by SteveElbows

Yes it does. That post links to multiple documents, one of which is this one:

http://k.min.us/ilnMjk.pdf

The pressure peak is right there, in the tables of data.

Yes, you are absolutely right, it is there, thank you. I really should have looked more carefully.

Knowing the data for the pressure peak in the more recently available data-series is in the column for the RPV A sensor, I went to look for it for that sensor in the older version of the data set. However in that dataset the high pressure data has been assigned to the RPV B sensor.

artax

Quote by MadderDoc

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

Why do you think so?

TBH I am having second thoughts based on some images posted earlier of it not being there before the explosion but I still think it very unlikely.
If you look at the pipe coming out of the end of the cream/yellow cylinder, it is bent vertically downwards. The bend is a manufactured bend and I think it even more unlikely that any ballistic object would land like that.
however I don't think it was 'installed' after the explosion by the fuku50 because it's there on the First Helicopter flyby vids.
So I am open minded but unconvinced!

tsutsuji

Quote by rowmag

Quote by ernal_student

The sentence where this appears could also mean something like "... TEPCO performed water leak countermeasures at a different building" - which, from what is written before that, could mean that the current facility is overburdened and they need to prepare another place.
In any case, whether it means fixing leaks, in my opinion "more watertight" is not a good translation. It is also logically wrong (someone already said that).

Even if you think the translations are good English (something I can probably not judge), I think we should look at the original text when there is some strange sounding information.

Thank you also for correcting my impression.

In slightly more detail, I interpreted the original to mean they were fixing another building (than the one used to receive Unit 2's water) within the Centralized Waste Treatment Facility. Which, yes, I guess I can agree is another inaccuracy in the translation that might have contributed to the original poster's complaint.

(For that matter, I suspect it was not a "building" (建物) that they were concerned about, but rather some holding tank or piping within a building. But that may have been an issue with the original terminology -- or my own mis- or over-interpretation. And I issue the caveat that I am not a professional translator.)

Yes, I definitely agree.

I see two possibilities. The first possibility is that the Centralized Waste Treatment Facility was designed some years ago for a given capacity of liquid waste. Storing larger quantities of highly contaminated water there straight away would have somehow meant breaking the rules. So they had to enhance their water leaking countermeasures, like having some more pumps and empty tanks ready in case a leak would occur, and ask NISA for approval. An other possibility is that the building was not designed at all to store liquids, but they made it watertight so that they can flood it with the contaminated water.

According to http://www.yomiuri.co.jp/science/new...OYT1T01016.htm , the Centralized Waste Treatment Facility enjoys a high level of shielding against radiations.

The video at http://www.tv-asahi.co.jp/ann/news/w...210516022.html shows that the pipes are running through the "high temperature incinerator building" before reaching the "Main process building".

I guess the "Centralized Waste Treatment Facility" is a set of several buildings including both the "main process building" where the contaminated water is being sent, and the incinerator building.

The worker who died on May 14th "had been working on the drainage system of the centralised radioactive waste store" : http://www.world-nuclear-news.org/RS...d-1605115.html

MadderDoc

Quote by artax

TBH I am having second thoughts based on some images posted earlier of it not being there before the explosion but I still think it very unlikely.
If you look at the pipe coming out of the end of the cream/yellow cylinder, it is bent vertically downwards. The bend is a manufactured bend and I think it even more unlikely that any ballistic object would land like that.
however I don't think it was 'installed' after the explosion by the fuku50 because it's there on the First Helicopter flyby vids.
So I am open minded but unconvinced!

Yes, the bend certainly looks like a manufactured bend, the question is if the cylinder is actually attached to it. Since I have been unable to find any signs of the presence of a cylindrical object there before the explosion, in photos that should have shown it if it was there, it seems impossible that it is actually attached. So, by an improbable stroke of chance it must have come to rest on the crushed remains of the original piping, such that it deceptively _looks_ as if it is attached to the bend.

"When you have eliminated the impossible, whatever remains, however improbable, must be the truth" (said Sherlock Holmes in "The sign of four")

swl

Does anyone here now what the pressure relief or steam relief valves are set for on one of these BWRs? Maybe running them above double design pressure is risky.

Also, did they actually ever successfully vent any of the 3 reactors or did they all blow a gasket, or rupture disk?

westfield

Quote by razzz

LOC makes venting a mute point. The reactors resorted to self venting or uncontrolled venting in this case. If there is no water available, do you just leave the vents open, waiting for water to return to the system? Maybe counter intuitive but the alternative is to allow the reactors to overpressurize with vents closed. Unit 2 overpressurized and blew around the torus area with the containment building still standing albeit is the source of a lot of the contaminated runoff to the ocean. Of course Unit 2 self vented somehow and sent a pop out panel flying out on its own according to workers who were sent to remove a pop out panel, finding that one gone already. A direct venting to the outside atmosphere, so to speak, with better results? (Not much)

Yes much better idea to permanently sacrifice your primary containment in order to prevent what might only be a minor atmospheric release. /sarcasm off ;)

artax

some interesting stuff here

http://online.wsj.com/article/SB1000...846064194.html

I'd hope they release these documents and I'd like to see the whiteboard scribblings from the time prior to the explosions!

The continuing conflicting reports about the situation are a nightmare,..... I was talking to a collegue last week who said everything's OK there now. Just depends which paper you read!

clancy688

Quote by jlduh

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

http://motherjones.com/blue-marble/2...s-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 learnt Tepco workers have possibly volountarily turned off after Tsunami and shutdown, in a procedure to "protect" the reactor).

The article is a joke, IMHO. If I understand it correctly, it's telling that the passive safety systems of the BWR/3 is better than later, energy driven safety systems. That's ridiculous.
First, we can perfectly see what happens if an Isolation Condenser is used to cool a nuclear reactor - total meltdown within 16 hours. It was switched off, but switched on again three hours after the earthquake.

And second, the Isolation Condenser is not even designated to provide emergency cooling for extended time periods. In a pdf regarding safety issues of the BWR/Mark-I design it's stated that the IC pool will be boiled dry within 1,5 hours! (Which would allegedly leave enough time to secure other means of cooling - ha, my ***...)

Moreover, the emergency cooling systems of Unit 2 und 3 (RCIC) worked much longer than the IC - for up to three days in case of Unit 2.

~kujala~

http://www.tepco.co.jp/en/challenge/.../plants-e.html

the plants are built on solid bedrock

I think I found out why they are using this term.

Here is how Merriam-Webster defines "bedrock":
http://www.merriam-webster.com/dictionary/bedrock

the solid rock underlying unconsolidated surface materials

Here is how Wikipedia defines it:

In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil.

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

The main thing is "unconsolidated". Mudstone happens to be a special form of shale/clay/mud that has accumulated during million years in the sediment layer of the ground and is considered to be "consolidated":

When consolidated and relatively massive it is known as mudstone (or claystone)...

http://www3.hf.uio.no/sarc/iakh/lithic/mudstone.html

Below "mudstone" is a harder/older layer of consolidated rock but still "mudstone" is thought to be part of "bedrock" when we use the word "bedrock" in its general meaning. If we want to divide between these two some special words has to be used. Like they use words "Mesozoic bedrock" and "Franciscan bedrock" in this page:
http://earthquake.usgs.gov/regional/nca/soiltype/
(I am using the word "harder bedrock" here.)

So when TEPCO says they have built Fukushima plants on solid bedrock they are not lying. Still I feel little bit cheated as the qualities of mudstone and harder bedrock probably differ a lot as seen from the earthquake stand of point. Again referring to previous page:
Vs > 1500 m/sec Includes unweathered intrusive igneous rock.
1500 m/sec > Vs > 750 m/sec Includes volcanics, most Mesozoic bedrock, and some Franciscan bedrock.
750 m/sec > Vs > 350 m/sec Includes different kind of sand, sandstones, mudstones and limestones.

Note 1: I am quite sure TEPCO has made some research concerning the qualities of harder bedrock (-46 meters from the current ground level) and mudstone and it would be very interesting to get the results from this research.
Note 2: They removed a 25 meter layer level of soft sand to get to the mudstone layer. Would it have been possible to remove a 46 meter layer of mudstone to get to the harder bedrock layer? But if they had done that the whole plant would have been below sea level which I guess would have been impossible.

zapperzero

Quote by artax

I was talking to a collegue last week who said everything's OK there now.

Your colleague has an interesting idea of what OK is.

MadderDoc

Quote by Rive

<..>
5) On one of the T-Hawk videos it can be seen that the service floor is broken only under the north crane boom.

Rive, sorry to be so late in catching up with this. I think quite on the contrary of what you say, in one of the T-Hawk videos the drone hovers close to the west end of the south crane boom, and it is readily apparent that the service floor in this position is also not intact (seeing that the floor has sunk under the boom.)
This is from the THawk video no3 from April 15th.

~kujala~

Quote by tsutsuji

I see two possibilities. The first possibility is that the Centralized Waste Treatment Facility was designed some years ago for a given capacity of liquid waste. Storing larger quantities of highly contaminated water there straight away would have somehow meant breaking the rules. So they had to enhance their water leaking countermeasures, like having some more pumps and empty tanks ready in case a leak would occur, and ask NISA for approval. An other possibility is that the building was not designed at all to store liquids, but they made it watertight so that they can flood it with the contaminated water.

Whether A or B I still see problems here. The thing is building watertight systems is not easy and if you do it "fast" you might fail. These things need time and good design to succeed and if you have to improvise it you never know what's the end result going to be.

On the other hand, I assume they simply don't have enough space so they have no other choice as to do it on the fly.

tsutsuji

Quote by artax

some interesting stuff here

http://online.wsj.com/article/SB1000...846064194.html

I'd hope they release these documents and I'd like to see the whiteboard scribblings from the time prior to the explosions!

The continuing conflicting reports about the situation are a nightmare,..... I was talking to a collegue last week who said everything's OK there now. Just depends which paper you read!

The documents are here : http://www.tepco.co.jp/nu/fukushima-np/index10-j.html (in Japanese). For example you can see some of the snapshots of whiteboards mentioned by the Wall Street Journal from page 17/55 of http://www.tepco.co.jp/nu/fukushima-..._Nisshi1_2.pdf

jlduh

Quote by NUCENG

The non-hardened vent system is the Standby Gas Treatment System. In an emergency it takes a suction on the secondary containment and discharges to the stack through particulate HEPA filters and activated charcoal filters to remove radiation from the vented air. The system maintains secondary containment at a small negative pressure so any leakage of the building is from the atmosphere to the building. Later in an accident the system can be used to take a suction on containment to clean up radiation inside a depressurized containment. Again it would discharge through the filters to minimize the release.

The whole purpose of the hardened vent is to allow a high pressure vent path from the torus air space to save containment integrity. The only motive force is containment pressure. The drywell will releve through the downcomers to the torus water pool which will also hold up soluble contaminants. As torus pressure drops whole containment is being vented.

Ok thanks NUCENG this is much clearer now.

So in fact hardened vent is not so hardened as it has to be operated in a reliable manner (which is the main problem!) very early in a severe accident case, otherwise it's not enough hardened to bear the high pressures.

Do we have data (in the US) about the values of max pressures allowable we are talking about for an" hardened vent" system?

Lookin at the speed at which H2 fills the much too small Mark I containment, yes this has to be VERY quick...

Now, the point that are unclear concerning the venting at Unit 1 during the 3 additional hours after Kan visit are:

- was it because the workers couldn't open the valves?
- was it because Tepco management had some fears of opening them (would be very interesting to know the content of the discussions during the 3 hours)?
- did it finally explode because they finally vented but the pressure was already too high and the tightness of Mark I containment already failed, with H2 entering the top floors (probably first at containment cover seal which was considered to be a weak point, based on data discussed here on the forum)?
- did it finally explode because they vented but the venting (supposedly hardened) failed because of too high pressure and the leak path of H2 entered the building and the top floors before exploding?

These question are currently unresolved IMHO.

jlduh

Quote by clancy688

The article is a joke, IMHO. If I understand it correctly, it's telling that the passive safety systems of the BWR/3 is better than later, energy driven safety systems. That's ridiculous.
First, we can perfectly see what happens if an Isolation Condenser is used to cool a nuclear reactor - total meltdown within 16 hours. It was switched off, but switched on again three hours after the earthquake.

And second, the Isolation Condenser is not even designated to provide emergency cooling for extended time periods. In a pdf regarding safety issues of the BWR/Mark-I design it's stated that the IC pool will be boiled dry within 1,5 hours! (Which would allegedly leave enough time to secure other means of cooling - ha, my ***...)

Moreover, the emergency cooling systems of Unit 2 und 3 (RCIC) worked much longer than the IC - for up to three days in case of Unit 2.

You are right of course, but the main idea of this article is to say that passive cooling is maybe a more reliable system than active ones (meaning the necessity of AC or DC power). Personally i have no idea of the problems associated with that principle which seems on the paper interesting. But what the paper says is that the newst generations of reactors seem to re-include that kind of systems. Again I have no idea if it is "marketing oriented stuff" (passive cooling seems great!) or if there is real improvement, and the article qustions this also by the way.

That's how I understand the spirit of this article.

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artax	some interesting stuff here http://online.wsj.com/article/SB1000...846064194.html I'd hope they release these documents and I'd like to see the whiteboard scribblings from the time prior to the explosions! The continuing conflicting reports about the situation are a nightmare,..... I was talking to a collegue last week who said everything's OK there now. Just depends which paper you read!