Fukushima Japan Earthquake: nuclear plants Fukushima part 2

[Rive]

TMI-2 cleanup team tried it, and decided that it is far too difficult and costly.

I'm sure you did not expect me giving an answer valid for financial viewpoint too...

Mechanically, there is no real issue with drilling/milling and sucking that stuff out. (What does not mean that other means might not be more easy, cheaper, safer, more heroic or even: funny.)

 

[Azby]

Tepco, NDF (Nuclear Damage Compensation and Decommissioning Facilitation Corporation), and the IRID consortium which is developing a lot of the new technologies for this decommissioning, seem to believe that it will be possible to remove the melted fuel material. Last summer it was announced that a side-entry method would be given priority. The equipment will be remotely operated, and they seem to be prepared for it to take decades. The attached image shows a recent schematic of the proposed equipment, much of which has already been built and is undergoing tests (annotations mine). Now we know, of course, that the melted fuel is not in nice coherent clumps...

This detailed 2016 report from NDF describes the removal scenarios that have been considered and the results of planning and testing in great detail. The “partial submersion-side access” scenario is described starting on p. 4-96:

NDF: Technical Strategic Plan 2016 for Decommissioning of the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company Holdings, Inc., July 13, 2016
http://www.dd.ndf.go.jp/en/strategic-plan/book/20170322_SP2016eFT.pdf

The 2017 NDF Technical Strategic Plan (Japanese only available so far) was released on August 31, 2017. A fairly detailed schematic and photos of the currently planned robotic removal equipment are on p. A-61
http://www.dd.ndf.go.jp/jp/strategic-plan/book/20170831_SP2017FT.pdf

 

[nikkkom]

I'm sure you did not expect me giving an answer valid for financial viewpoint too...

My point is precisely about economic feasibility of doing this.
I have no doubt that technically it can be done, but cost/benefit ratio looks very bad. Benefit is near-zero. There are no economical reasons to have corium removed from PCVs, the reasons are almost purely emotional ("we cleaned up this mess") with a tinge of perceived improvement in nuclear material security.
How is it worth spending several billion dollars and ~10 years to achieve?

 

[Rive]

My point is precisely about economic feasibility of doing this.

Your original post were mixing the complete decontamination with the corium cleanup, on basis of the 'how', which is exactly the technological aspect.

There are no economical reasons to have corium removed from PCVs, the reasons are almost purely emotional ("we cleaned up this mess") with a tinge of perceived improvement in nuclear material security.

The term 'cleaning up' can mean many things in this aspect. If you ask 'should they retrieve and safely deposit the corium and the most seriously affected materials' then my answer is 'yes': that stuff cannot be safely stored in that damaged PCV for long term, so it must be retrieved, and in this cost has only limited meaning.

If you ask decontamination as 'should they restore the buildings as they was before', then my answer is 'no'.

 

[nikkkom]

that stuff cannot be safely stored in that damaged PCV for long term

...why? You are just assuming it. Give me the reasons why it cannot be safely stored there.

 

[Rive]

...why? You are just assuming it. Give me the reasons why it cannot be safely stored there.

Safe storage in this context means control over the stuff. Do you feel like anybody there has any real control over that stuff there?
Other than pouring water endlessly they are totally helpless even with such basic matters as cooling.

Dry storage, with scheduled supervision. That's 'storage'. The actual situation is just 'rubble pile'.

 

[nikkkom]

Safe storage in this context means control over the stuff. Do you feel like anybody there has any real control over that stuff there?

Yes. I'm pretty sure no one can steal it. It is a thick steel-lined concrete structure without possibility of human entry.
Also, unlike TMI-2 corium, this corium's Pu is not weapon-grade, so the material is not useful as bomb material, there are no incentives to steal it.

Other than pouring water endlessly they are totally helpless even with such basic matters as cooling.

It does not require cooling now.

Dry storage, with scheduled supervision. That's 'storage'. The actual situation is just 'rubble pile'.

Why it can not be dry there?
Why being in the shape of rubble is particularly bad?
Why it can not be supervised there?
(Aside from the question "what exactly you are expecting to prevent by supervising it?". Magically disappearing? However, if it makes you feel better, by all means, supervise it as often as you want. Install a CCTV camera in a glass box inside.)

 

[Rive]

I'm pretty sure no one can steal it.

Are you able to guarantee that it won't go away by itself? Would you bet your neck on it?
Just 'cause it was quite a hassle to keep that water in check, you know: with all the typhoons and raining and such. Somehow, that building does not seems to be watertight.

It does not require cooling now.

You don't even know how it is deposited there, are you sure you have the qualification to say such thing?

(Aside from the question "what exactly you are expecting to prevent by supervising it?". Magically disappearing?)

There are quite number of 'magical' disappearings, leaks and such in this context already. Even dry storage not infallible - not without regular checks, and re-storage as necessary.

 

[nikkkom]

Are you able to guarantee that it won't go away by itself? Would you bet your neck on it?

Yes. I'm positive, 100.00% certain uranium ceramic resolidified melt does not evaporate. :D

You don't even know how it is deposited there, are you sure you have the qualification to say such thing?

Yes.

 

[Hiddencamper]

Yes. I'm pretty sure no one can steal it. It is a thick steel-lined concrete structure without possibility of human entry.
Also, unlike TMI-2 corium, this corium's Pu is not weapon-grade, so the material is not useful as bomb material, there are no incentives to steal it.
It does not require cooling now.
Why it can not be dry there?
Why being in the shape of rubble is particularly bad?
Why it can not be supervised there?
(Aside from the question "what exactly you are expecting to prevent by supervising it?". Magically disappearing? However, if it makes you feel better, by all means, supervise it as often as you want. Install a CCTV camera in a glass box inside.)

What are you talking about. TMI2 corium having weapons grade plutonium. That's pretty bogus.

 

[Rive]

Yes.

And in the same time you are talking like as if Uranium would be the main concern there.

 

[nikkkom]

What are you talking about. TMI2 corium having weapons grade plutonium. That's pretty bogus.

TMI-2 accident happened on the very first fuel load, after only three months of operation. Therefore, the plutonium generated in its fuel was quite low on Pu-240.

Why do you think TMI-2 corium was sent for storage to _DOD_ facilities instead of being stored in civilian dry storage?

 

[HowlerMonkey]

It will likely heat up if there weren't a ton of water being circulated.

 

[nikkkom]

It will likely heat up if there weren't a ton of water being circulated.

By very little. (I would guesstimate that if all air and water circulation would be closed, the hottest location would go to about 60-70 celsius). The accident happened almost seven years ago.

Let's compare it to TMI:
NP-6931.pdf
The Three Mile Island accident occurred on March 28, 1979. Two years later, decay heat became so low that reactor was cooling itself just by conducting heat to outside:

 

[Hiddencamper]

It will likely heat up if there weren't a ton of water being circulated.

At this point it's not so much about temperature, it's more about keeping stuff wet to reduce airborne contamination and holding fission products in the liquid. Letting stuff dry out is a great way for stuff to potentially go airborne. Water also provides shielding.

 

[Rive]

At this point it's not so much about temperature

Before we knew how the stuff actually deposited it was said here that water is needed because there are configurations which limits cooling, so we can't guarantee the temperature without active cooling.

As it is now, we already has some idea about the configuration (stuff embedded in sand-like substance in the bottom of a big bucket) and this configuration is precisely one of the worst. All previous worries are now justified.

It would not be a miracle to find some underwater mud/heat springs there.

Let's compare it to TMI:

TMI had far less stuff melt together, without being embedded into a flow-blocking substance.

 

[nikkkom]

TMI had far less stuff melt together, without being embedded into a flow-blocking substance.

Wrong. TMI-2 had all "stuff" tightly packed in one place (RPV), sealed in it, then sealed in containment building, practically none of major heat generating nuclides (Cs, Sr) were removed - unlike Fukushima, where Cs must be largely removed by 7-year leaching now.

And yet, ~2 years from accident, TMI-2 heating was low enough that no forced cooling was necessary to keep it below 100 celsius, when they closed valves to OTSGs (steam generators).

TMI-2 reactor temperature fell below 100 celsius much earlier than that - on 1979-04-27. Ironically, this happened exactly on the day when they switched *off* pumped recirculation through OTSGs, since the pump was generating 2/3 of the heat load.
Recirculation through OTSGs continued after 1979-04-27 for ~1 year by natural flow due to hotter water's lower density.

 

[nikkkom]

TMI-2 cooling:

 

[Rive]

Wrong. TMI-2 had all "stuff" tightly packed in one place (RPV)

Man, take a look at any picture about the final configuration of the TMI reactor internals and give some deep thoughts about convection and surface.

 

[nikkkom]

Man, take a look at any picture about the final configuration of the TMI reactor internals and give some deep thoughts about convection and surface.

I read this as "I have an argument why TMI-2 situation wrt heat generation by corium was better than Fukushima, but I won't tell you what this argument is. Guess it".

Sorry, but this is not how discussions work. You need to lay out your arguments yourself.

 

[Sotan]

http://photo.tepco.co.jp/library/180316_01/180316_02.JPG
A glimpse inside the cover newly installed over the operating floor of Unit 3 building.
Photo taken during a visit of the US Ambassador to Japan on March 16.

Sorry... not much else to post. It's been a while but if there have been important developments, I must have missed them.

 

[turi]

• Mainichi reports that TEPCO is set to extract a debris sample from unit 2: http://mainichi.jp/english/articles/20180316/p2a/00m/0na/018000c
• For your search optimization: The Fukushima units are often written like "２号" for example for unit 2 in Japanese. Depending on the site I've been on or the search engine I've used, my searches sometimes didn't find what I've expected. The "２" used here isn't a simple ASCII digit "2", instead its a Unicode FF12 (fullwidth digit two). Some search indexes unify them, some keep them separate. And the "in page search" functionality of browsers might distinguish them as well (e.g. Firefox).

 

[nikkkom]

http://photo.tepco.co.jp/library/180316_01/180316_02.JPG
A glimpse inside the cover newly installed over the operating floor of Unit 3 building.
Photo taken during a visit of the US Ambassador to Japan on March 16.

Any info how the floor's contamination was removed or shielded? There are some removable shields installed (e.g. concrete blocks), or they resurfaced it?

 

[etudiant]

Any info how the floor's contamination was removed or shielded? There are some removable shields installed (e.g. concrete blocks), or they resurfaced it?

Afaik, the ambassador is standing on the floor of the extra superstructure that was added to hold the replacement fuel handling machine.
So he is not close to touching the actual floor of the damaged reactor, which was previously scrubbed and then surfaced with metal plates to cut the radiation burden as much as possible.
In general, it seems that the clean up effort is ongoing and progressing steadily. It appears to be more effectively managed than the comparable US effort at Hanford, which admittedly poses a larger and more dispersed cleanup task.

 

[Charles Smalls]

Any info how the floor's contamination was removed or shielded? There are some removable shields installed (e.g. concrete blocks), or they resurfaced it?

You can see the new metal/ sheild clad walking surface erected over the original refuelling floor here. One of the techs appears to be using a Geiger counter to measure the amount of radiation coming up from below as they walk over it.

 

[Sotan]

http://www.tepco.co.jp/nu/fukushima-np/roadmap/2018/images1/d180329_07-j.pdf
(in Japanese)

Pages 4-12: They will make a big opening in the West wall of the Reactor Building of Unit 2 and install an "antechamber" in front of that opening. The idea is that, at some point in the future (2020~) they plan to remove the whole roof and upper side of the reactor building, in preparation for the works for removing the fuel bundles stored in the SFP. Before that, they need to investigate the operating floor (5th floor) foor radiation and dust and take measures to decrease these, and in order to carry out these operations they will cut a 5m x 7m opening in the West wall. The antechamber will be air-tight and equipped with purification installatons and HEPA filters.The opening should be ready around June or July.

Pages 13-18: Progress on the installation of the new cover on the operating floor of Unit 3. In fact, as you know, the cover is completed. The drawings on page 15 show that at step 1 there are some insulation/shielding layers placed on the operating floor (not sure if this is a satisfactory answer to nikkkom's question at post 1623 above). 2 pages give info on the number of people who worked durign this phase and the amount of radiation they were exposed to. The schedule on page 18 shows that they are planning to begin removing the spent fuel from the SFP sometime in the 3rd trimester of Fiscal year 2018, so maybe mid October.

 

[Stephenk53]

Part 1 can be found here:
https://www.physicsforums.com/showthread.php?t=480200Magnitude-5.3 earthquake hits Japan's Fukushima
http://www.usatoday.com/story/news/world/2013/09/19/japan-fukushima-nuclear-plant/2835493/

What is the reason for thread closure, please?

Not closed, moving to part 2. After 14k posts it becomes a system performance issue.

Since it is at 16k I suggest moving to part 3

 

[krater]

Since it is at 16k I suggest moving to part 3

Off by an order of magnitude.

 

[Stephenk53]

Off by an order of magnitude.

oops, oh well.

 

[etudiant]

Actually, I do think the slow but steady progress being made with the Fukushima cleanup is really newsworthy.
Somehow, the Japanese seem to have mastered the problem of pursuing a very difficult engineering project without falling prey to totally corrupt corporate log rolling, in contrast to the debacles in the US on similar projects such as Hanford or INEL. It would be useful to look at the contractual details, including the performance incentives, that are yielding such different outcomes.

 

[jim hardy]

It would be useful to look at the contractual details, including the performance incentives, that are yielding such different outcomes.

I have to think it's largely cultural... at the end of World War Two we sent Edward Demming over there to teach 'statistical product quality administration'.
They established a business culture of "doing things well" .
But back home we ,... well..; have you ever seen that old movie "how to succeed in business without really trying" ?

 

[etudiant]

I have to think it's largely cultural... at the end of World War Two we sent Edward Demming over there to teach 'statistical product quality administration. They established a business culture of "doing things well" .
But back home we ,... well..; have you ever seen that old movie "how to succeed in business without really trying" ?

Well, corporate US has certainly drunk the Kool-Aid concept of 'shareholder value' as the primary measure of merit for business decisions.
So that mandates very different contractual standards than when business was based on relationships and trust as much as on the bid numbers.
It should not be impossible to develop such standards, but there is understandably not much interest on part of industry, while the government bureaucracy has little incentive to do so while money is abundant.

 

[etudiant]

Not sure whether this alters the legal landscape, but apparently TEPCO executives told the regulators 4 days before the accident that the plant would be swamped in the event of a 15 meter tsunami. That tsunami estimate had been developed as part of an independent study earlier when TEPCO was considering building a seawall., but then decided not to proceed. A multi hundred billion dollar mis-judgment in retrospect.

 

[jim hardy]

Not sure whether this alters the legal landscape, but apparently TEPCO executives told the regulators 4 days before the accident that the plant would be swamped in the event of a 15 meter tsunami. That tsunami estimate had been developed as part of an independent study earlier when TEPCO was considering building a seawall., but then decided not to proceed. A multi hundred billion dollar mis-judgment in retrospect.

Wow so somebody got through.. Not much they could've done in four days, though.

 

[etudiant]

Wow so somebody got through.. Not much they could've done in four days, though.

It seems the actual tsunami assessment was done in 2007, with a 15.7 meter maximum estimated. The decision not to do anything dates from around that time.
The testimony to the regulators came much later, in what context I don't know.
Asahi Shimbun reported on April 11 2018. http://www.asahi.com/ajw/articles/AJ201804110051.html

 

[Cire]

Our first good view of what happened under the RPV.

http://www.asahi.com/ajw/articles/AJ201804270041.html

 

[jim hardy]

Asahi Shimbun reported on April 11 2018. http://www.asahi.com/ajw/articles/AJ201804110051.html

That's quite an interesting article. I don't know how i missed your post.

A multi hundred billion dollar mis-judgment in retrospect.

Can you imagine ? He must feel worse than captain of Titanic.

 

[Sotan]

Our first good view of what happened under the RPV.
http://www.asahi.com/ajw/articles/AJ201804270041.html

Great find Cire, thank you.

The same subject is treated in this report, part of the regular update in Long- and Mid-term Roadmap released on April 26:
http://www.tepco.co.jp/nu/fukushima-np/roadmap/2018/images1/d180426_08-j.pdf
(Japanese only)
- The images taken during the investigation of Jan 2018 have been processed a lot and various new findings appeared.I will mention below just a few notes derived from the photos and text in this document.
- Page 10 as given by Acrobat reader: Pebble and sand size sediment layer which looks like something that was melted and then solidified is visible on the floor of the pedestal. Sediment is also deposited on the "cable tray" which is made of stainless steel 4mm thick, but it must have been cool enough, judging from the fact that the steel of the cable tray hasn't changed shape.
- Page 11: 3 puddles of water are observed on the floor (rather, on the surface of the sediment). Enough cooling is ensured, judging from the temperature (21 degrees Celsius).
- Page 12: sediment in one part of this area may be 70cm thick. Close to the CRD changing machine the thickness is believed to be more like 40-50 cm. Various structural remnants can be seen here (upper tie plate of a fuel bundle; pipe-shaped thing; spring-shaped thing.
- Page 14: pedestal walls show some peeling and roughness of the epoxy-based paint but no further damage.
- Page 15-16: they could identify some letters on the handle of that fuel bundle, but not all of them therefore they cannot say exactly where that fuel bundle was located in the reactor before the meltdown (theoretically can be any of the 132 blue squares on page 16).
- Page 23: Another fallen object which suggests a fuel bundle handle (1 cm thick) has been seen on the rails used for the rotation of the working platform.
- Page 24: Pipe-like fallen object, ~2 cm thick. Hard to say where it comes from.
- Page 25: Spring-like fallen object. Might be from SRNM or LPRM detectors (I don't know what those are...) or from a fuel bundle, as those things contain springs.
- Page 26-27: Rod-like fallen object.
- Page 28: something that looks like a plate, but examined more closely suggests a panel of grating covered by sediment.

Pages 35~ refer to Unit 3 PCV. Based on the images taken by the swiming robot they created a partial 3D map of structural elements in the PCV.

 

[nikkkom]

Looks about as expected...

TMI-2 cleanup was walk in the park compared to this mess...

 

[HowlerMonkey]

TMI-2 didn't suffer a 9.0 earthquake.

 

[nikkkom]

TMI-2 didn't suffer a 9.0 earthquake.

Neither did Fukushima arrive to this state because of the quake per se.
It suffered from a tsunami, which we now know was a _known_ to the company risk.

 

[Charles Smalls]

There’s a new 49 minute feature by NKH investigating some sustained high level radiation releases that occurred from the plant during the accident but have never been clearly understood or explained:

https://youtube.com/watch?v=CwlvPRpq7aw

It’s very well done with a lot of work gone into tie information and masses of date together. Good breakdown of the program and it’s findings here:

http://www.fukuleaks.org/web/?p=16683

 

[nikkkom]

The massive regulatory/bureaucratic machine produced thousands upon thousands of pages on safety, and yet the recipe for handling the meltdown seems to be: "seal the reactor shut to avoid leaks of radioactive materials... and then pump water into it to cool it down". No one saw any problems with this idea? Really?

 

[Charles Smalls]

The massive regulatory/bureaucratic machine produced thousands upon thousands of pages on safety, and yet the recipe for handling the meltdown seems to be: "seal the reactor shut to avoid leaks of radioactive materials... and then pump water into it to cool it down". No one saw any problems with this idea? Really?

I think when you design and sell a plant based on the notion that it is too safe to fail, you can’t really then go on to clearly and explicitly plan for an event in which then does. It’s like the unsinkable Titanic not having enough lifeboats for the all passengers on board, once you bill a system as 100% safe and reliable even if something goes wrong, it’s suddenly really difficult if not politically impossible to then start talking about things like “in case we’re wrong and things go completely wrong, do this”. They sold it as fool proof so they kind of have to live that lie. Otherwise it’s 10 times more difficult to credibly suggest operating it in the first place.

As for on the Daiichi itself, I think even with manuals, I don’t know if the outcome would have been any different. Handbooks are only as good as the data you have to put into them. With no power and no reliable readings, they wouldn’t have had anything other than hunches to go on. Plus I think the doc highlights clearly, is that managing conditions in the pressure vessels was almost a side issue anyway. Almost all attention was focused on the dangerous condition of the unit 3 and 4 spent fuel pools. Falling water levels uncovering the fuel, damage from the explosions and no real effective containment over the pools if anything went badly wrong, they were clearly top priority. If they lost control there, eastern Japan could have been lost. In a full on crisis like this, even something as serious as keeping the pressure vessel contents cooled can be relegated to a side issue. Add to that the fatigue, undermanning and rising dose rates effecting who could go where on site, they had to pick their battles.

Was very impressed NHK pulled together so much information and with the incredibly tight timeline they established. They are really pursuing the events of the accident in incredible detail

 

[gmax137]

I think when you design and sell a plant based on the notion that it is too safe to fail...

... once you bill a system as 100% safe and reliable even if something goes wrong...

... They sold it as fool proof ...

These are all strawmen. Who ever said "100% safe." Nothing is 100% safe.

 

[nikkkom]

I think when you design and sell a plant based on the notion that it is too safe to fail, you can’t really then go on to clearly and explicitly plan for an event in which then does.

This might have been the reason before Fukushima.

But what are the reasons why filtered vents are not mandated in US even _after_ Fukushima experimentally demonstrated that meltdowns are a realistic possibility?

As for on the Daiichi itself, I think even with manuals, I don’t know if the outcome would have been any different. Handbooks are only as good as the data you have to put into them.

Well, they definitely could have properly engaged IC on Unit 1, if accident manuals has clear directives to do so in station blackout. Thus, Unit 1 could have been saved.

And if manuals would have sections directing them to do so, they could have vented RPVs of Units 2 and 3 down to atmospheric pressure _before_ fuel started to melt. This would have released small amounts of radioactivity, yes, but then they could start injecting water with much less powerful pumps, since there would be no pressure difference to fight against. Units 2 and 3 could have been saved, too.

In reality, and as the video above clearly explains, with no manuals, they tried to reach two opposing goals at once: keep RPVs pressurized, and pump water into them. It was not possible to achieve both at once.

 

[jim hardy]

It was not possible to achieve both at once.

That's the heart of it.

 

[etudiant]

Nikkom indicates that the NKH report highlights how most of the damage from the accident was because there was no early depressurization of the crippled reactors.
If this is a correct understanding, has depressurizing now become part of the regular accident mitigation procedure for nuclear sites more generally?

 

[anorlunda]

That's quite an interesting article.

I don't know. The article gives far too little detail to judge whether the employee made his case well enough. Employees disagree with each other all the time. History will prove some of them to be right, but that does not prove the others were negligent.

But, I did like the article title: TEPCO worker: Boss scrapped tsunami wall for Fukushima plant. Clearly improved safety results from having no bosses.

 

[jim hardy]

From the article:

Some experts were skeptical about the assessment, given that there were no archives showing a towering tsunami ever striking the area.

I've been under the impression since the early days after the incident that there were old stone markers on the hill above the plant indicating a high water mark from a thousand years ago.

https://www.smithsonianmag.com/smar...inst-tsunamis-dot-japans-coastline-180956448/

but my memory could have altered facts in the intervening years. I couldn't testify today as to whether they're on that particular hill.

old jim