Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[clancy688]

Melting down doesn't automatically imply corium. A meltdown can be cladding splitting open and dumping pellets to the bottom of the RPV.

Of course, but that didn't happen at Fukushima. I think it's VERY unlikely that we're only dealing there with dumped pellets. It's a full scale meltdown in all three reactors.
Remember TMI. The coolant loss there was nothing compared to the loss at Fukushima. And still corium formed.

 

[Borek]

Of course, but that didn't happen at Fukushima. I think it's VERY unlikely that we're only dealing there with dumped pellets. It's a full scale meltdown in all three reactors.

Truth is we don't know what have happened. No doubt there is a mess inside, but stating anything as a known fact is premature.

 

[MadderDoc]

Ah well, the latest data shows a major drop, not sure why it trended in this fashion.
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110617_01-e.pdf
<..>

It is not plausible that the exhauster after having done relatively little to lower the air contamination over a 5 day operation period, then suddenly over a 12 hour period appears to have decimated it. It is also not plausible that it is due to a measurement or graphing error.

But Tepco could plausibly have opened the door, letting in fresh air. Yesterdays press article reported that taking this step had been authorized.

 

[clancy688]

Truth is we don't know what have happened. No doubt there is a mess inside, but stating anything as a known fact is premature.

That's why I said that dumped pellets are unlikely instead of impossible. :tongue:We won't know for sure what's actually present in- or outside the RPV. We'll get facts when they open up the reactors, which won't happen during the next few years. So we should work with the most likely scenario. That is, in my opinion, and especially if we take TMI2, the time the cores were uncovered and the water height in the vessels during the melting (In Unit 1 possibly zero) into consideration, the presence of corium. Moreover most discussers here seem to have implemented the presence of corium into their reasoning. So I don't see much problems telling that corium is very likely present.

 

[biggerten]

The pipe hooked up to the handrail does not reach into the spent fuel pool. It pours the water into the pool from above. Therefore no check valve is necessary.

That will do the trick.

By the way, the water decontamination system is now online -

http://www3.nhk.or.jp/daily/english/17_34.html

 

[DSamsom]

By the way, the water decontamination system is now online -

http://www3.nhk.or.jp/daily/english/17_34.html

looking at the pictures of the decontamination system, i wonder how they are going to deal with the huge buildup of radioactivity in the filtersystems. Have they figured out a way to get rid of the radiating sludge fully automatically?

 

[etudiant]

looking at the pictures of the decontamination system, i wonder how they are going to deal with the huge buildup of radioactivity in the filtersystems. Have they figured out a way to get rid of the radiating sludge fully automatically?

In theory, the cesium, which represents the vast bulk of the activity afaik, is mostly adsorbed in the Kurion zeolite columns, which are sealed cartridges. So exchanging these would be fairly easy and quick, although looking at the pictures, there is no room for a robot handler, so people will have to take the radiation hit to make the exchange. These cartridges are apparently designed for direct vitrification, so provided Kurion can keep the cesium inside while the cartridge is getting glassified, rhat contamination can be safely locked away.

The rest of the process looks much more messy, as AREVA has indicated they expect several thousand cubic meters of toxic radioactive sludge to be produced. Japan has said the wastes will be stored in Japan, so we may look for an urgent search for a waste repository.
Maybe in Okinawa or some similar out of the way location :).

 

[SteveElbows]

Well this months roadmap update didnt contain anything surprising, or at least not that I've noticed. Perhaps a few small details of note, but none that I can think of off the top of my head.

http://www.tepco.co.jp/en/press/corp-com/release/11061702-e.html

However the following document does contain some pictures that I don't think I've seen before, outside reactor 3 building (demolished the damaged vehicle entrance tunnel by the looks of it). And also, joy of joys, a view of the site looking down from the top of the slope where the webcam is, so that we can actually see the ground around the reactors and further to the left of reactor 1 than normal. Its not very high res within this pdf, but it still gives me a much improved sense of the state of a good chunk of the site these days. (that photo, or rather 3 photos stitched together, is on page 13)

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110617e4.pdf

 

[Astronuc]

Is the presence of corium a fact?

Thanks in advance.

No. It is based on an analysis, apparently with conservative assumptions regarding heat transfer, or lack thereof. It is a fact that there is significant damage to the fuel. We won't establish the 'facts' until the vessel head is removed and the cores are visually inspected. Comments regarding fuel melting and corium are speculative for now.

There is certainly the question of whether or not the cores of units 1, 2 and 3 actually received the cooling water that was being pumped into the vessels. Some instruments indicated coolant levels in the core, but perhaps those instrument measurements are unreliable. If the vessel penetrations were breached early in the event, then it could be that the injected water simply flowed out. One the other hand, since the water found in the base of the reactor building was heavily contaminated with radioisotopes, it is likely the water contacted the fuel, so it seems there was water in the cores, or at least in the RPVs.

It also appears that TEPCO and NISA believe there was/is water in the lower plenums of the RPVs, and if that is so, then the fuel is less likely to have melted.

 

[MiceAndMen]

The rest of the process looks much more messy, as AREVA has indicated they expect several thousand cubic meters of toxic radioactive sludge to be produced. Japan has said the wastes will be stored in Japan, so we may look for an urgent search for a waste repository.
Maybe in Okinawa or some similar out of the way location :).

I don't remember reading about the average spent fuel load that was originally expected in your average BWR SFP, but I'm sure that those loads increased in large part due to the lack of off-site storage. High density racks for Spent Fuel Pools speak to the fact that the loads initially designed for have been exceeded. I guess that's pretty common knowledge nowadays, both in Japan and in the U.S. at least.

To now, the attitude seems to have been "we'll just continue to accumulate spent fuel on-site for the forseeable future and someone will eventually figure out how to deal with it." Hopefully the Fukushima Daiichi situation provides impetus going forward to deal with the off-site spent fuel repository "problem" in Japan. Too bad no such thing will happen in the U.S. and spent fuel will continue to accumulate at the plants indefinitely. One cannot continue to kick that can down the road forever.

 

[joewein]

However the following document does contain some pictures that I don't think I've seen before, outside reactor 3 building (demolished the damaged vehicle entrance tunnel by the looks of it). And also, joy of joys, a view of the site looking down from the top of the slope where the webcam is, so that we can actually see the ground around the reactors and further to the left of reactor 1 than normal. Its not very high res within this pdf, but it still gives me a much improved sense of the state of a good chunk of the site these days. (that photo, or rather 3 photos stitched together, is on page 13)

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110617e4.pdf

Yes, that was a worthwhile read.

Of interest to me was the description of a plan to fix the presumed unit 2 torus leak (page 4):

Open a hole in floor of 1st floor of R/B and fill grout in the torus

By surrounding the donut-shaped suppression chamber with concrete they are hoping to stop outflow of water from the containment through the cracked torus.

I think that work will be very tricky because they'll effectively have to pour concrete under water. Normally, when you construct concrete foundations of bridges, etc. in a river you get rid of the water first, which won't be possible here. It reminds me of the trouble they had plugging that water leak in the trench near unit 2 back in April. Anyway, they say they'll try out their plan in a lab first. Will they build a mockup of a broken, flooded torus?

What's worse, the water in and around the torus is highly radioactive. They're talking about drilling down into the basement from the first floor, but next door in unit 1 they measured 3000-4000 mSv/h in a location where steam rises into the first floor from the basement, which is the worst figure measured anywhere in Fukushima Daiichi outside the containments so far.

The document shows a lot of visual details of preparations for pouring concrete (page 19). Looks like one of the Putzmeister trucks (dubbed "zousan 3" = Elephant 3) will finally get used for its original purpose. I think I saw that the Putzmeister trucks used for pouring water are referred to as "kirin" (giraffe).

There's a diagram showing the newly installed 32 steel pillars under the unit 4 spent fuel pool (SFP) getting embedded into a concrete wall (page 18). So the steel is ultimately just meant as reinforcement bars, with the concrete carrying the load.

They also show a system "under consideration" of a cooling system within the reactor building (page 2), with water pumped from the basement of the reactor building through a heat exchanger into the RPV. The current plan is to pump water from the basement of the turbine hall, treat it and then feed some of it back into the RPV. Do they think sufficient time with the treatment cycle plan would decontaminate the containment enough that a cooling cycle without decontamination will become feasible? Given that they will be paying some $500 million to Areva SA for water treatment by early next year, maybe they have a strong incentive to eventually skip the filtration step.

 

[joewein]

One the other hand, since the water found in the base of the reactor building was heavily contaminated with radioisotopes, it is likely the water contacted the fuel, so it seems there was water in the cores, or at least in the RPVs.

Whether fuel pellets lie at the bottom of the RPV or melted there or melted through to the concrete floor of the dry well, water injected into the RPV would have passed the fuel and picked up cesium and iodine, simply following gravity from the feedwater or fire suppression lines.

Once pellets melted, the volatile elements would have evaporated and later condensed in the suppression chamber and/or the dry well. Water leaking from the containment would first have picked up major contamination from there even if it didn't directly pass what's left of the core.

In fact, the less water was in the core in the first couple of days the more cesium and iodine would have escaped from inside melting ceramic pellets, later recondensing elsewhere in the containment. Therefore I see the high levels of radioactivity in the water in the building basements not so much as hopeful evidence that fuel did receive minimal cooling, but perhaps that it did not.

I am more encouraged by moderate temperature readings at the RPVs, but who knows what sensors can still be trusted at this stage?

 

[sigyn]

Problems with cleaning water ?

"The level of radiation at a machine to absorb cesium has risen faster than our initial projections,"

...

"Officials had said earlier this week that large and growing pools of radioactive water at the Fukushima Daiichi plant were in danger of spilling into the sea within a week unless action was taken quickly."



http://news.yahoo.com/s/nm/20110618/ts_nm/us_japan_nuclear;_ylt=Aq_cxFl3pVcRyWkwjsf.5gJZ.3QA;_ylu=X3oDMTJudThtOGhmBGFzc2V0A25tLzIwMTEwNjE4L3VzX2phcGFuX251Y2xlYXIEcG9zAzExBHNlYwN5bl9wYWdpbmF0ZV9zdW1tYXJ5X2xpc3QEc2xrA2phcGFuMzlzdGVwYw--

 

[etudiant]

Problems with cleaning water ?

"The level of radiation at a machine to absorb cesium has risen faster than our initial projections,"

...

"Officials had said earlier this week that large and growing pools of radioactive water at the Fukushima Daiichi plant were in danger of spilling into the sea within a week unless action was taken quickly."



http://news.yahoo.com/s/nm/20110618/ts_nm/us_japan_nuclear;_ylt=Aq_cxFl3pVcRyWkwjsf.5gJZ.3QA;_ylu=X3oDMTJudThtOGhmBGFzc2V0A25tLzIwMTEwNjE4L3VzX2phcGFuX251Y2xlYXIEcG9zAzExBHNlYwN5bl9wYWdpbmF0ZV9zdW1tYXJ5X2xpc3QEc2xrA2phcGFuMzlzdGVwYw--

Perhaps this is mixed news, rather than all bad.
The good news is that the Kurion cesium adsorbing material is clearly doing its job well.
The bad news is that the water is so contaminated that the cesium build up may make the cartridges too dangerous to handle. Judging from the few pictured that have been released, the plant does not appear to be automated, so that the periodic replacement of spent cartridges is a manual task. That may not be feasible if the cesium level is too high.
It is surprising that this development was not anticipated in the design. Or is my understanding just wrong?

 

[razzz]

Since concrete (which is usually rock(s), sand and cement) and even grout (which is cement and sand) are heavy than water, the mix will displace the water (force it out and away). Concrete could dilute (water washes out the cement) but pumping in more would overcome that. Many additives available for concrete mix design properties.

Problems ex. torus leak is not where anticipated, torus has or develops (due to added weight) other leak areas where in effect one has to fill the entire area in and around the torus with this concrete mix, decay heat causes the concrete to setup faster than desired, water finds or causes other passages to subsoil, disturbing the coolant flow creates a mini-disaster, air-pockets occur leaving voids, contaminated coolant discharge is raised to a higher level and so on and so on.

Well, that's why you have architects and engineers to draw up a plan. Seems a bit early in the game to me unless they know something we don't.

 

[Luca Bevil]

Problems with cleaning water ?

"The level of radiation at a machine to absorb cesium has risen faster than our initial projections,"

...

"Officials had said earlier this week that large and growing pools of radioactive water at the Fukushima Daiichi plant were in danger of spilling into the sea within a week unless action was taken quickly."



http://news.yahoo.com/s/nm/20110618/ts_nm/us_japan_nuclear;_ylt=Aq_cxFl3pVcRyWkwjsf.5gJZ.3QA;_ylu=X3oDMTJudThtOGhmBGFzc2V0A25tLzIwMTEwNjE4L3VzX2phcGFuX251Y2xlYXIEcG9zAzExBHNlYwN5bl9wYWdpbmF0ZV9zdW1tYXJ5X2xpc3QEc2xrA2phcGFuMzlzdGVwYw--

Very alarming news after a few hours of operation...

This equipment was supposed to operate in an almost continuos basys.

We should suppose they began processing an heavier than average contaminated water..

Why ?

And what countermeasures could be available ?

I feel like we wll never see the end of this nightmare.

 

[Orcas George]

Let us hope for the best, perhaps an instrument problem.

Apparently someone left a valve closed on the Kurion machine and overpressurized it, damaging a relief valve and releasing 6000 liters of water. They fixed that yesterday but perhaps there was more damage to the machine than thought? I was a little concerned that they started up so quickly after replacing that damaged valve, testing should have started over from step #1 as soon as anybody placed a wrench on the equipment.

The problem with that system is that if it does have a leak when processing the hot stuff, it becomes expensive junk. For something so mission critical, I have heard the "leak" word an awful lot these last few weeks. I may be jumping to conclusions that it is a leak related problem, but otherwise it doesn't make much sense. The designers knew that they would be handling highly radioactive water so I would assume that shielding was designed into the machine.

Once again TEPCO's vagueness leaves us all wondering.

 

[jlduh]

In theory, the cesium, which represents the vast bulk of the activity afaik, is mostly adsorbed in the Kurion zeolite columns, which are sealed cartridges. So exchanging these would be fairly easy and quick, although looking at the pictures, there is no room for a robot handler, so people will have to take the radiation hit to make the exchange. These cartridges are apparently designed for direct vitrification, so provided Kurion can keep the cesium inside while the cartridge is getting glassified, rhat contamination can be safely locked away.

The rest of the process looks much more messy, as AREVA has indicated they expect several thousand cubic meters of toxic radioactive sludge to be produced. Japan has said the wastes will be stored in Japan, so we may look for an urgent search for a waste repository.
Maybe in Okinawa or some similar out of the way location :).

Well, reading this news

http://www3.nhk.or.jp/daily/english/18_10.html

is no good news and to tell you the truth when they announced that kind of plan for treating so much water with so much contamination with a system put in place in 2 months in a total last resort mode, i didn't believe this could work: it looks kind of magical to remove contamination from water for non specialists and citizens and medias but there is no free lunch, contamination has to go somewhere and be even more concentrated: there is no process to reduce radioactivity, there are only some to separate it (to some extent) from other medium, in this case water. Does this kind of "magical" process already happen somewhere in the world in an industrial fashion, with so much contamination at first i mean and at such a rate, 1200 tons per day? I don't think so!

One way or another, the contamination that was contained in the pellets + zirconium rods + pressure vessel + containment vessel (with steel and more than 1 meter thickness concrete) will have to be concentrated somewhere, and this somewhere will be with no real containment except the cartridges! How can we believe this can really happen and work, especially in a last resort installation put in place in 2 months like this one?

That's why I said a long time ago that i strongly think that the final containment of this mess will be the pacific ocean. I still hope to be really wrong. But my hope is more miracle based than science based.

 

[NUCENG]

Well, reading this news

http://www3.nhk.or.jp/daily/english/18_10.html

is no good news and to tell you the truth when they announced that kind of plan for treating so much water with so much contamination with a system put in place in 2 months in a total last resort mode, i didn't believe this could work: it looks kind of magical to remove contamination from water for non specialists and citizens and medias but there is no free lunch, contamination has to go somewhere and be even more concentrated: there is no process to reduce radioactivity, there are only some to separate it (to some extent) from other medium, in this case water. Does this kind of "magical" process already happen somewhere in the world in an industrial fashion, with so much contamination at first i mean and at such a rate, 1200 tons per day? I don't think so!

One way or another, the contamination that was contained in the pellets + zirconium rods + pressure vessel + containment vessel (with steel and more than 1 meter thickness concrete) will have to be concentrated somewhere, and this somewhere will be with no real containment except the cartridges! How can we believe this can really happen and work, especially in a last resort installation put in place in 2 months like this one?

That's why I said a long time ago that i strongly think that the final containment of this mess will be the pacific ocean. I still hope to be really wrong. But my hope is more miracle based than science based.

I am trying to figure out your point. I assume you don't want them to give up and pump this water into the sea, even though that would fulfill your prediction. They are just starting up this process and will have some startup issues.

 

[GJBRKS]

Well, reading this news

http://www3.nhk.or.jp/daily/english/18_10.html



One way or another, the contamination that was contained in the pellets + zirconium rods + pressure vessel + containment vessel (with steel and more than 1 meter thickness concrete) will have to be concentrated somewhere, and this somewhere will be with no real containment except the cartridges!

I haven't examined the design yet , but it would seem logical to suppose that there would be a multitude of cartridges to absorb and replace.

The news makes it look like one of the cartridges is experiencing a buildup , perhaps due to an uneven distribution of contaminated water.

They would have to look at ways to regulate the parallel flow and processing.

Either that or the level of contamination is much higher than expected , or the filter is doing a better job than anticipated

 

[Calvadosser]

jlduh: "That's why I said a long time ago that i strongly think that the final containment of this mess will be the pacific ocean. I still hope to be really wrong. But my hope is more miracle based than science based."

I am trying to figure out your point. I assume you don't want them to give up and pump this water into the sea, even though that would fulfill your prediction. They are just starting up this process and will have some startup issues.

I think jlduh is simply expressing what I and many others have come to believe. That the indications are that the consequences to the accident at Fukushima are not being dealt with effectively and that, if this is correct, some very large releases of radioactivity into the ocean will be the result. Nobody is suggesting TEPCO give up their efforts and we ernestly hope that our lack of confidence in what they are attempting is proved unfounded.

 

[jlduh]

I am trying to figure out your point. I assume you don't want them to give up and pump this water into the sea, even though that would fulfill your prediction. They are just starting up this process and will have some startup issues.

I'm not criticizing Tepco attempts to put "something" in place, of course. I'm criticizing Tepco attempts to put in place these kind of last resort solutions NOW, in the current situation where prototype process has no time to be prototype.

The total imprepareness for managing that kind of situation is softly covered by the generic term "Beyond design basis accident and expectations". Let me tell you that anger, distress, fear and current or future suffering of people is "beyond design basis human acceptation" also.

The problem is that when things are considered as "impossible to happen", nothing is done to anticipate the consequences, and this water treatment story started a few days before overflowing of contaminated water is a typical example. This is the all story of this Fukushima disaster in fact: Fukushima is an impossible accident, but consequences are real.

I'm a little bit fed up with that kind of rhetoric in which some consider accidents impossible but THEN very easily present as "possible" what are in fact very improbable solutions to (try to) manage consequences of these "impossible" accidents!

I think they just screwed up in the way they placed the word "impossible", in fact. But this is a critical and even criminal mistake, at least IMHO.

But this leads to one real technical question to specialists: does it ever exists in production in the world a system to separate so much contamination at a such rate of 1200 tons per day (even letting aside the question: can it be installed and started up in 2 months which is the "cherry on the cake", as we say in french?)

If this exists, then I will admit that my comments above are biased or even wrong.

If not, then I will tend to think that they are just biased... by facts?

 

[Luca Bevil]

I apologise if this point has already been discussed and was just I that had not enough time for recognising it.

I just came across this analisys
http://allthingsnuclear.org/post/4704112149/how-many-cancers-did-chernobyl-really-cause-updated

nothigh that appeared extraordinarily new as of now, but it was clearly written and well presented so I kept reading until my attention was catched by this statement:

"The momentary loss of power closed the main steam isolation valves (MSIVs). As shown in the diagram above, there are two MSIVs in each of the four pipes carrying steam from the reactor vessel to the turbine. The fail-safe position of the MSIVs is closed. When power was lost, the MSIVs closed. Steam being produced by the reactor core’s decay heat had been traveling through the steam lines to the turbine.
When the MSIVs closed, that steam could no longer travel this path. In addition, the normal supply of makeup water to the reactor vessel to compensate for water leaving as steam is via the feedwater system.
The feedwater system features steam-driven pumps. The source of steam for the feedwater pump turbines is taken from the steam lines downstream of the MSIVs. Thus, closure of the MSIVs made the feedwater pumps unavailable.
The successful start of both emergency diesel generators restored power to essential plant equipment. The operators would have been able to re-open the MSIVs. But that step, if taken, would not have been longlasting.
The emergency diesel generators do not provide power to the equipment handling the steam
collecting in the main condenser. Normally, the pressure inside the condenser is maintained as close to perfect vacuum conditions as can be obtained. The near-vacuum conditions help pull steam through the turbine. As condenser vacuum is lost, sources of steam to it are automatically isolated. Thus, if re-opened, the MSIVs would have soon automatically re-closed".

Now if the statement is correct, and I am not extrapolating erroneously, that seems to suggest to me that EVEN IF the EDG had not failed the EDG provided power would have not been enough for the condenser to operate correctly.

In this case what would have been done to prevent meltdown ?
I can only think of external, out of loop, water injection and repeated venting.
In other words in such designs assuming grid connection fail, but EDG do not fail, what is the expected release to the environment ?
It would seem to me that in such cases at least a TMI2 pattern if not probably much more could be expected (may be something in a INES 5, or even INES 6 if grid connection takes several days to restore, classification range ?).

Not that reinsuring to say the least... one would wonder what could happen in different designs, like PWRs for example..

but for that I guess would be better to open different threads.

 

[rmattila]

Now if the statement is correct, and I am not extrapolating erroneously, that seems to suggest to me that EVEN IF the EDG had not failed the EDG provided power would have not been enough for the condenser to operate correctly.

That's right; the large seawater pumps supplying cooling water to the condensers are too large to be run with the EDGs. Therefore, for the situations where the normal heat transfer route is lost due to loss of external power, the plant is equipped with auxiliary/emergency cooling systems - so called safety systems.

These systems supply water to the reactor, which is converted to steam and directed to the containment suppression chamber/condensation pool (instead of the condenser). The heat is supposed to be transferred from the condensation pool to the sea via dedicated heat transfer systems which are small enough to be run with the EDG power. This is quite usual operation mode of the BWR plants whenever the large seawater pumps stop for some reason. The problem at Fukushima was the loss of these safety systems designed to run when the systems for normal operation are not used - not the loss of the normal operation systems, which is just an operational occurrence - supposed to take place once a year or so.

 

[Luca Bevil]

That's right; the large seawater pumps supplying cooling water to the condensers are too large to be run with the EDGs. Therefore, for the situations where the normal heat transfer route is lost due to loss of external power, the plant is equipped with auxiliary/emergency cooling systems - so called safety systems.

These systems supply water to the reactor, which is converted to steam and directed to the containment suppression chamber/condensation pool (instead of the condenser). The heat is supposed to be transferred from the condensation pool to the sea via dedicated heat transfer systems which are small enough to be run with the EDG power. This is quite usual operation mode of the BWR plants whenever the large seawater pumps stop for some reason. The problem at Fukushima was the loss of these safety systems designed to run when the systems for normal operation are used - not the loss of the normal operation systems, which is just an operational occurrence - supposed to take place once a year or so.

Thanks.
That would be Residual Heat Removal System - Suppression Pool Cooling Function I suppose.

I see.
While reading a BWR manual on line - I incorrectly assumed that these functions would use subsystems or sections of the heat exchanger in the condenser and hence got alarmed when reading that the condenser to be operated needs low pressure to be maintened on its outlet on the primary side.

 

[NUCENG]

I'm not criticizing Tepco attempts to put "something" in place, of course. I'm criticizing Tepco attempts to put in place these kind of last resort solutions NOW, in the current situation where prototype process has no time to be prototype.

The total imprepareness for managing that kind of situation is softly covered by the generic term "Beyond design basis accident and expectations". Let me tell you that anger, distress, fear and current or future suffering of people is "beyond design basis human acceptation" also.

The problem is that when things are considered as "impossible to happen", nothing is done to anticipate the consequences, and this water treatment story started a few days before overflowing of contaminated water is a typical example. This is the all story of this Fukushima disaster in fact: Fukushima is an impossible accident, but consequences are real.

I'm a little bit fed up with that kind of rhetoric in which some consider accidents impossible but THEN very easily present as "possible" what are in fact very improbable solutions to (try to) manage consequences of these "impossible" accidents!

I think they just screwed up in the way they placed the word "impossible", in fact. But this is a critical and even criminal mistake, at least IMHO.

But this leads to one real technical question to specialists: does it ever exists in production in the world a system to separate so much contamination at a such rate of 1200 tons per day (even letting aside the question: can it be installed and started up in 2 months which is the "cherry on the cake", as we say in french?)

If this exists, then I will admit that my comments above are biased or even wrong.

If not, then I will tend to think that they are just biased... by facts?

OK, I.m still trying. Are you suggesting that this type of recovery system should have been prototype tested and standardized before the accident? That is a valid idea, but since that didn't happen, we are seeing the prototype go through its birthing pains in an actual emergency.

 

[intric8]

1 of 24 cartridges reached capacity within 5 hours time. Given the volume of water and Cs content therein, we can speculate that under normal operations, after every 5-10 hours an additional cartridge would max out and require manual removal.

Let's face facts - this water cleansing operation will prove notoriously expensive not only monetarily, but in precious time and cumulative exposures to staff, especially if each cartridge is removed manually.

I think this was a bit unanticipated by tepco, and that the areva staff are getting an earful right about now. Areva was provided the appropriate data and indicated that each cartridge would be http://www.google.com/hostednews/ap/article/ALeqM5jlXd5_F1goJBmZByasNwAiP6EoRA?docId=d223ba8d656345f2972d68b492c83187" .

 

[ManuBZH]

I think this was a bit unanticipated by tepco, and that the areva staff are getting an earful right about now. Areva was provided the appropriate data and indicated that each cartridge would be http://www.google.com/hostednews/ap/article/ALeqM5jlXd5_F1goJBmZByasNwAiP6EoRA?docId=d223ba8d656345f2972d68b492c83187" .

Well, in this case, it is Kurion's system (cesium absorption) which is not working as expected. Not Areva's water decontamination one (yet?).

 

[joewein]

Let's face facts - this water cleansing operation will prove notoriously expensive not only monetarily, but in precious time and cumulative exposures to staff, especially if each cartridge is removed manually.

I recall recently seeing an interview with someone from Areva in which they were introducing the treatment system and explained that it was being provided at a fixed price, as they were not going to take advantage of TEPCOs troubles to make a great profit.

If indeed all cartridges were included then -- ignoring the practical problems involved in frequently swapping cartridges for the moment -- Areva would have a problem. Kurion would make money in the short term if they sell more cartridges to Areva, but it would be bad for their business relationship if the cartridges don't last as advertised.

Ultimately none of the three companies will be happy if the solution sold to the public doesn't work.

 

[swl]

Well, in this case, it is Kurion's system (cesium absorption) which is not working as expected. Not Areva's water decontamination one (yet?).

[STRIKE]"The (TEPCO) official said teams working at the plant believed the radiation rise could be linked either to sludge flowing into the machinery absorbing caesium or a monitoring error caused by nearby pipes carrying contaminated water."[/STRIKE]

Bold text highlighted by me.

[STRIKE]http://ibnlive.in.com/news/radiation-spike-halts-work-at-japan-nplant/160610-2.html[/STRIKE]

Please see following post by Tsuji san.

 

[tsutsuji]

Or walked into a greenhouse in the middle of Summer to water the plants.

For reference, the yield strength of polyethylene is about 4,000 psi or about 25 MPa. About 1/3 that of copper (at 70 MPa).

So, a 1 mm square string could support ~2.5 kg. Or a 25 mm x 1 mm strip could support ~62.5 kg.

We will wait and see, but I am optimistic that it isn't in tatters by this time next year.

The cover is not made of polyethylene, but of polyesther fabric coated with PVC (polyvinyl chloride), like truck covers or tarpaulins : http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110614e17.pdf

They are using 40mil poly pond liner (40mil = 1mm).

Where did you find the 1 mm thickness data ?

I haven't examined the design yet , but it would seem logical to suppose that there would be a multitude of cartridges to absorb and replace.

The news makes it look like one of the cartridges is experiencing a buildup , perhaps due to an uneven distribution of contaminated water.

They would have to look at ways to regulate the parallel flow and processing.

Either that or the level of contamination is much higher than expected , or the filter is doing a better job than anticipated

The absorption facility is divided into 4 parallel lines (see the figures on http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110612_01-e.pdf and http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110617_04-e.pdf ). Yesterday they started only two. And both of them are having the unexpected high radiation trouble. 4.7 mSv/h was measured on line No. 1 and 3.9 mSV/h on line No. 3. (No.2 and No.4 were unused).

The absorption towers displaying these radiation levels are the oil and technetium removing towers, at the entrance of the system. Three possibilities were mentioned during the NISA's press conference on June 18th ( http://www.ustream.tv/recorded/15456089 ) :

* To do without the oil and technetium absorption tower (starting directly with the cesium removal towers) ;
* Use of silica sand to filter oil
* Changing the location of the radiation sensor

The first two will be tested on June 18th and 19th, using different solutions on each line and making comparisons.

If my understanding is correct, most of the oil is removed by the Toshiba oil separator mentioned in http://mdn.mainichi.jp/mdnnews/news/20110616p2a00m0na013000c.html before the water enters the Kurion-made facility. There is hardly any technetium in the water so there is no harm in bypassing the oil and technetium removal tower.

Flushing with clean water had been started, and the radiation level had decreased to around 1 mSv/h at the time of the press conference.

OK, I.m still trying. Are you suggesting that this type of recovery system should have been prototype tested and standardized before the accident? That is a valid idea, but since that didn't happen, we are seeing the prototype go through its birthing pains in an actual emergency.

Having to design a solution from scratch is not unlike the various attempts to plug and pump the Deepwater Horizon oil spill. However, the water purifying facility is not totally made from scratch, because the Kurion-made part is "an improved version of the reputable TMI water treatment", and the Areva-made part "has a track record at the reprocessing plant at La Hague" : http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110609e8.pdf

"The (TEPCO) official said teams working at the plant believed the radiation rise could be linked either to sludge flowing into the machinery absorbing caesium or a monitoring error caused by nearby pipes carrying contaminated water."

Bold text highlighted by me.

http://ibnlive.in.com/news/radiation-spike-halts-work-at-japan-nplant/160610-2.html

What was said in the press conference is the possibility that radioactive particles may combine with oil to form something similar to "salad dressing".

 

[etudiant]

We have, according to NISA, the bulk of the contamination onsite in the water. many terabequerels worth. The treatment will hopefully move this to the filters and the processing sludge, leaving (fairly) clean water.
The plan is to exchange the cartridges when the ambient radioactivity exceeds 4 millisievert, which has happened very quickly, unsurprising given the extent of the water contamination. Yet the stated expectation was that this level would only be reached after a month.
So the problem is why did anyone expect the filters to last so long if the water is so dirty?
Afaik, the bulk of the contamination is from the cesium and the Kurion filters are designed to pick up the cesium, which they appear to be doing. So the problem is that because the filters cannot be changed out automatically, they can only serve for a brief period before they must be changed, lest they become too contaminated for humans to handle.
This seems like a design flaw. What am I missing?

 

[Astronuc]

We have, according to NISA, the bulk of the contamination onsite in the water. many terabequerels worth. The treatment will hopefully move this to the filters and the processing sludge, leaving (fairly) clean water.
The plan is to exchange the cartridges when the ambient radioactivity exceeds 4 millisievert, which has happened very quickly, unsurprising given the extent of the water contamination. Yet the stated expectation was that this level would only be reached after a month.
So the problem is why did anyone expect the filters to last so long if the water is so dirty?
Afaik, the bulk of the contamination is from the cesium and the Kurion filters are designed to pick up the cesium, which they appear to be doing. So the problem is that because the filters cannot be changed out automatically, they can only serve for a brief period before they must be changed, lest they become too contaminated for humans to handle.
This seems like a design flaw. What am I missing?

It could be that the filters worked very efficiently, or it could be a matter of communication or rather miscommunication. Is it perhaps the water is more highly contaminated, or is it perhaps that the water chemistry is such that the collection of the intended radioisotope(s) was much more efficient than expected. If the collection reached a limit in hours instead of weeks, then that's two orders of magnitude difference in collection rate. So one must ask, is the concentration of radioisotope(s) so high, or so specific (i.e., not so many different metal ions (each with a different decay constant) competing for the same amount of absorber), or . . . ?

If a filter is too hot to manually handle, then obviously it must be handled remotely, just as with any radioactive source or object. Normally enriched fuel is handled with thin gloves, while MOX fuel is handled remotely, often in glove boxes (with heavier gloves) if an individual must do 'hands on' work.

 

[elektrownik]

Someone here computed that in basements of reactors and turbine buildings contain 1/2 of Chernobyl core (amount of cesium and iodine), so yes there is change problem but also there would be thousands of radioactive filters to store somewhere...

 

[Astronuc]

OK, I.m still trying. Are you suggesting that this type of recovery system should have been prototype tested and standardized before the accident? That is a valid idea, but since that didn't happen, we are seeing the prototype go through its birthing pains in an actual emergency.

Adding to NUCENG's comment - I believe the water treatment system is based on current AREVA technology used in their waste treatment streams either in their reprocessing plants or remediation programs. What we don't know is what access AREVA has had to the TEPCO site, or what information has been provided by TEPCO to AREVA concerning the contaminated water.