Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[tsutsuji]

Reactor 3 torus room survey robot, which had sound monitoring equipment to listen for running water, got stuck and hasnt been retrieved. 360 mSv/h measured at side of the northern torus access hatch, 230 mSv/h in location where robot is stuck:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120712_03-e.pdf

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120713/index.html No conspicuous damage was observed except the fact that the south-western door is broken.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120713/0400_4gk.html The NISA approved the plan to retrieve 2 fresh fuel assemblies from unit 4 pool. The assemblies will be pulled with 4 wires. The operation will be controlled with the help of an underwater camera, and radiation measurement tools. The NISA said these safety measures are "appropriate". As a security measure concerning radioactive substances, Tepco will not announce the date beforehand.

http://www.meti.go.jp/press/2012/07/20120712003/20120712003.html NISA approval for unit 4 fresh fuel assembly removal
http://www.meti.go.jp/press/2012/07/20120712003/20120712003-3.pdf Figure 2 at the bottom of the page shows the rafter crane on the platform above the reactor well with two hooks. Figure 4 is the tool that will be used for inspecting the fuel at the common pool. This inspection is scheduled during the last ten days of August. Normally the radiation on the surface of the fresh fuel is 25 microsievert/hour.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120712_05-e.pdf Unit 2 RPV Alternative Thermometer: SLC Pipe Soundness Confirmation.

Why isn't the pipe already filled with water from the RPV ? Is there a check valve or something preventing water from flowing downwards ?

At 10:35, "no more water could be injected from that point". Why not ? What is preventing the water from pouring into the RPV ?

Does this result (soundness of SLC instrumentation pipe is confirmed) mean that the core is not as badly melted as could be thought ? It sounds like at least that pipe did not melt.

 

[Joffan]

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120712_05-e.pdf Unit 2 RPV Alternative Thermometer: SLC Pipe Soundness Confirmation.

Why isn't the pipe already filled with water from the RPV ? Is there a check valve or something preventing water from flowing downwards ?

At 10:35, "no more water could be injected from that point". Why not ? What is preventing the water from pouring into the RPV ?

Does this result (soundness of SLC instrumentation pipe is confirmed) mean that the core is not as badly melted as could be thought ? It sounds like at least that pipe did not melt.

Thanks for for continuing reporting efforts tsutsuji.

As Tepco says, the amount of water injected into the pipe and the retention of pressure point to a blocked pipe. The 15L injected was way less than the (as-designed) volume of the pipe, 33L. So there is potentially crud in the pipe, perhaps corrosion products, and these are blocking the pipe. It's also possible that the pipe has distorted (by heat or mechanical impact) which could block and reduce volume, or that the RPV internal section of the pipe has been penetrated and blocked by corium; or a combination.

The "result" is that the SLC pipe is not currently usable as a thermometer insertion route. Exactly why is not yet determined.

 

[tsutsuji]

Thanks Joffan. I was perplexed by this "soundess is confirmed" conclusion in the Tepco handout.

http://genpatsu-watch.blogspot.fr/2012/07/20127131800.html [transcript of July 13's press conference] Junichi Matsumoto:

"Normally, it is thought that the injected volume obtained from the pipe's length and diameter is 33 litres. Of course, in the hypothesis where the pipe is open up to the RPV, we presumed that water would go on entering even after filling 33 litres of water, but the situation in yesterday's soundness check is that injection becomes impossible at around 15 litres, and after the water filling was stopped, we observed the pressure decline status.

Today, when we checked at around 10:00, it was about 100 kPa as shown above. Well, as it was not the water head value of 68 kPa or 56 kPa measured by the water elevation when the extremity is open, we are suspecting that the pipe is somehow clogged.

Therefore, about anything special that we could say about this pressure, well, we understood that probably it is clogged, and we want to check the status of this clogging.

Also, checking methods are currently under study, but as we had been carrying out the preparations for alternative thermometer insertion, at present we are checking if we could not look inside the pipe using an industrial endoscope with that method".

 

[Joffan]

Thanks Joffan. I was perplexed by this "soundness is confirmed" conclusion in the Tepco handout.

Me too, but I can speculate that, as the pipe did hold a very considerable pressure for a long time, in one sense it is "sound" in that it is probably not leaking to the PCV. Or perhaps - you would know better than me - it's a mistranslation of the idea that the the soundness has been confirmed... bad.

 

[tsutsuji]

Or perhaps - you would know better than me - it's a mistranslation of the idea that the the soundness has been confirmed... bad.

That's right. It was a mistranslation.

計装配管の健全性を確認　should have been translated as "checking instrumentation pipe soundess" or "we shall check instrumentation pipe soundness".

There is a second handout on the same topic dated July 13: www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120713_04-e.pdf

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120718/index.html Tepco removed one of the 204 fresh fuel assemblies in unit 4 pool on 18 July, starting at around 9:00 AM. They plan to remove a second one soon.

http://www.sbs.com.au/news/article/1670136/Workers-remove-nuke-fuel-from-Japan-plant "Television crews used helicopters to film the operation, defying requests from TEPCO"

Asahi News

Fuji News

http://www.dailymotion.com/video/xs8r32_yyyyyyyyy-yyyyyyyy_news JNN

 

[Andres Arce]

Does anybody know what that underwater tarpac is for ?
(at 01.22)
http://www.dailymotion.com/video/xs8r32_yyyyyyyyy-yyyyyyyy_news

 

[MadderDoc]

Does anybody know what that underwater tarpac is for ?
(at 01.22)
http://www.dailymotion.com/video/xs8r32_yyyyyyyyy-yyyyyyyy_news

Hello there Andres Arce. I believe this particular sequence of that video is from the May 26th tour to the top floor of unit 4. The camera appears to be looking into the cutaway in the southwest corner of the general floating plastic construction which composed the covering of the pool at that time. The cutaway gives access to the water surface of the pool. I think this cutaway is where water is circulated in and out of the pool and perhaps where e.g temperature sensors are interfaced. I am not sure what exactly we are seeing underwater, but since the general covering is there to protect from something falling into the pool, it would make sense to me that a similar protection has been put underwater in the cutaway in order to catch objects that might fall into the pool during operations there.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120719/index.html On 19 July at around 06:00 AM, Tepco took the second fresh fuel assembly out of unit 4 pool and put it into a special transportation container. There was not any trouble so far.

[I'm unsure if the fuel assemblies are still on the 5th floor or if they have already taken them away to the common pool]

 

[westfield]

Does anybody know what that underwater tarpac is for ?
(at 01.22)
http://www.dailymotion.com/video/xs8r32_yyyyyyyyy-yyyyyyyy_news

It's a reflection, not underwater.

 

[zapperzero]

There was not any trouble so far.

Apparently the rods were slightly contaminated, but nothing dramatic.

 

[tsutsuji]

Apparently the rods were slightly contaminated, but nothing dramatic.

Do you know that from a news source or how did you guess it ?

http://www.tepco.co.jp/en/press/corp-com/release/2012/1206689_1870.html "The transportation to common pool building was completed at 4:47 PM on July 19"

 

[LabratSR]

Fukushima contractor covers up worker exposure

http://www3.nhk.or.jp/daily/english/20120721_23.html

 

[tsutsuji]

http://icanps.go.jp/post-2.html Cabinet investigation committee final report (Japanese)

http://icanps.go.jp/eng/SaishyuRecommendation.pdf Final report recommendations (English)

 

[zapperzero]

Fukushima contractor covers up worker exposure

http://www3.nhk.or.jp/daily/english/20120721_23.html

Asahi also covers it:

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201207210069

Disgraceful, to say the least. Lack of oversight.

 

[zapperzero]

Reactor 2 is still the worst polluter, Asahi reports:

The most radiation is being emitted from the No. 2 reactor, which is releasing 8 million becquerels an hour.

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201207240087

 

[Ms Music]

Hi, long time since I have posted here... (thankfully)

What is the process for removing fuel from the storage pools? Just curious since they have only removed two new assemblies so far. I understand the used fuel is hotter, so what is the process (even if so far unknown) and how long can the used assemblies be out of water? How long does it take to inspect the assemblies?

Just curious why a/ it has taken so long to remove the two new ones (is it low priority?), and b/ why do they expect it to take so long to remove the rest? I have read this thread long enough now you can throw some meat at me, and I should understand.

Thanks in advance, back to being a lurker.

 

[Astronuc]

Hi, long time since I have posted here... (thankfully)

What is the process for removing fuel from the storage pools? Just curious since they have only removed two new assemblies so far. I understand the used fuel is hotter, so what is the process (even if so far unknown) and how long can the used assemblies be out of water? How long does it take to inspect the assemblies?

Just curious why a/ it has taken so long to remove the two new ones (is it low priority?), and b/ why do they expect it to take so long to remove the rest? I have read this thread long enough now you can throw some meat at me, and I should understand.

Thanks in advance, back to being a lurker.

The reactor service floor and spent fuel pools were covered with debris, and the areas were heavily contaminated. The new (fresh) fuel could be more easily removed, except that is has been contaminated on the outer surface by activated corrosion products and any fission products that escaped from the operating or spent fuel.

The normal course is the use the fuel handling machine (the green bridge structure) to install and remove fuel assemblies. The fuel racks have a little clearance with each fuel assembly, so usually the fuel handling machine is indexed to the spent fuel pool racks.

The fuel assemblies sit under several meters of water which provides shield from the radiation to the workers operating on the machine. They will move the assemblies underwater to a cask. Once loaded, the cask lid is installed and the cask is then drained - really the water inside is displaced by an inert gas - helium. The cask environment is dried and finally sealed. There is an outer shield and protective container in which the cask sits. The whole set is then lifted and moved to a transporter - trailer or truck. The cask may be transferred to another pool (interim storage), or it may be sent to a dry storage facility onsight. If the fuel is sufficiently cool, it may be sent to a reprocessor, if the utility is part of a program to reprocess its fuel.

The overhead crane is used to lift the heavy cask and its contents. The overhead cranes were destroyed in the explosions and fires.

 

[Ms Music]

The FHM is functioning on #4? I thought they would have to use an external (outside of the building) crane to remove the assemblies, and other methods of getting them into a cask. Well, at least 3 and 4. 1 and 2 still have a roof...

I am just surprised it has been a year and a half before they removed two fresh fuel assemblies out of 4.

Thanks again.

 

[LabratSR]

The FHM is functioning on #4? I thought they would have to use an external (outside of the building) crane to remove the assemblies, and other methods of getting them into a cask. Well, at least 3 and 4. 1 and 2 still have a roof...

I am just surprised it has been a year and a half before they removed two fresh fuel assemblies out of 4.

Thanks again.

Video shot from news helicopters of the operation.

http://www.youtube.com/watch?v=j_kDf2JB8-Q&feature=related

 

[zapperzero]

The FHM is functioning on #4? I thought they would have to use an external (outside of the building) crane to remove the assemblies, and other methods of getting them into a cask. Well, at least 3 and 4. 1 and 2 still have a roof...

I am just surprised it has been a year and a half before they removed two fresh fuel assemblies out of 4.

Thanks again.

No, the FHM is not operational. They have used a small crane for this operation but there will be a need for a much larger one to handle casks, as well. Most of the time has been spent in waiting for the radiation fields to lower somewhat and then in clearing debris (a rather involved operation, but one which has taken shorter than planned, iirc)

 

[mscharisma]

... Just curious ... why do they expect it to take so long to remove the rest? ...

Am also a lurker and a complete nontechnical person. Apart from the difficulty of the process and the destroyed equipment/more or less improvised new equipment, I believe to remember that, per regulations, the used fuel rods have to be cooled a certain number of years in the pool before they are cool enough be moved.

 

[Astronuc]

Am also a lurker and a complete nontechnical person. Apart from the difficulty of the process and the destroyed equipment/more or less improvised new equipment, I believe to remember that, per regulations, the used fuel rods have to be cooled a certain number of years in the pool before they are cool enough be moved.

Yes - there is usually a 5 year or so cooling period before the any fuel is committed to dry storage. The exception would be a single assembly or a few fuel rods which could be removed soon after operation - several months to a year - in order to be sent to hotcell for examination. One can also mix cooler older fuel with hotter younger fuel to balance the thermal burden. One can also use lower burnup fuel to shield higher burnup fuel.

The higher the burnup, the more the decay heat, so a utility could elect to the let fuel cool longer than 5 years, which has been the case for much of the fuel, at least in the US, since the use of dry storage has been a more recent development due to lack of a repository or reprocessing program.

Dry storage casks may handle up to 68 BWR fuel assemblies, but Fukushima may use smaller transportation casks that might handle fewer assemblies.

See this discussion - Impact of Fukushima Accident on Spent Fuel Management in Japan
http://rampac.energy.gov/PCN/P8.pdf

 

[Ms Music]

Yes - there is usually a 5 year or so cooling period before the any fuel is committed to dry storage.

Yes, but that would be in a normal situation. Here we are dealing with a structurally unsound building. I thought there would be more of a push to get the rods into another pool quicker. Maybe they trust their temporary structural reinforcement more than I do.

I will read the other thread (edit PDF, not thread), maybe I can grasp this without dragging this thread too far into my own questions.

Thank you all!

 

[LabratSR]

Yes, but that would be in a normal situation. Here we are dealing with a structurally unsound building. I thought there would be more of a push to get the rods into another pool quicker. Maybe they trust their temporary structural reinforcement more than I do.

I will read the other thread (edit PDF, not thread), maybe I can grasp this without dragging this thread too far into my own questions.

Thank you all!

http://www.tepco.co.jp/en/press/corp-com/release/2012/1201934_1870.html

And that links to this.

http://www.tepco.co.jp/en/press/corp-com/release/betu12_e/images/120416e0201.pdf

 

[Astronuc]

Yes, but that would be in a normal situation. Here we are dealing with a structurally unsound building. I thought there would be more of a push to get the rods into another pool quicker. Maybe they trust their temporary structural reinforcement more than I do.

I will read the other thread (edit PDF, not thread), maybe I can grasp this without dragging this thread too far into my own questions.

Thank you all!

As far as I know, the reinforced concrete containment structure that supports the spent fuel pool is sound, and they added reinforcement to it. The upper containment structures (the structure above the reactor service floor) of Units 1, 3 and 4 were severely damaged - and the refueling bridges and overhead cranes were damaged or basically destroyed. In addition, the areas are heavily contaminated, so their immediate access for personnel is severely limited/restricted.

As far as I know, the spent fuel pools are receiving adequate cooling.

The spent fuel would normally be moved carefully underwater, especially since it may now contain failed rods. If that is the case, then movement of the fuel will be done carefully to avoid additional contamination of the spent fuel pool water and exposure to the personnel and current containment. Any failed fuel could also release Kr-85 (t_1/2 = 10.75 y) as well as other water-soluble fission products, e.g., Cs-134, -137, and fuel particles.

 

[tsutsuji]

http://www.nisa.meti.go.jp/shingikai/700/14/240724/BT-3-6.pdf Hiroto Inoue, JNES, "Seismic Safety Evaluation of the Spent Fuel Pool at the Unit 4", July 24, 2012 (English)

http://www.tepco.co.jp/nu/fukushima-np/images/handouts_120723_05-j.pdf Fukushima Daiichi accident workshop, July 23-24 2012 "middle and long term roadmap toward decommissioning and research & development"

http://www3.nhk.or.jp/news/genpatsu-fukushima/20120724/index.html The strontium removal device was publicly presented on 24 July in Yokohama. At present, more than 170,000 tons of contaminated water are stored at Fukushima Daiichi. In the device that was shown, nuclides contained in the contaminated water are adsorbed by resin in a stainless steel tank. By passing through different tanks, up to 62 nuclides can be removed, it was said. This way water can be decontaminated down to the level specified for release into the sea, which is a precaution against the risk of leaks into the environment. The facility will be installed at Fukushima Daiichi by the first 10 days of September, and then the test run will be started. For the time being, the decontaminated water is planned to be stored in tanks, but what will be done in the future has not been decided.

 

[tsutsuji]

Fukushima Daiichi accident workshop, July 23-24 2012

http://www.nisa.meti.go.jp/shingikai/700/14/240723/program.pdf program

http://www.nisa.meti.go.jp/shingikai/700/14/240723/240723.html presentations, July 23

http://www.nisa.meti.go.jp/shingikai/700/14/240724/240724.html presentations, July 24

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120723_05-e.pdf Tepco presentations, July 23

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120724_02-e.pdf Tepco presentations, July 24

 

[zapperzero]

http://www.nisa.meti.go.jp/shingikai/700/14/240723/240723.html presentations, July 23

Yet another MAAP accident simulation, yet another presentation wrt presumed causes of the explosion at #4, yet another iteration of the plan to find and plug leaks of radioactive water. I wonder, when will the simulations and projections start being replaced with actual data?

 

[etudiant]

Well, it seems that the plan is to reprocess the decontaminated water sufficiently to be able to dump it, although 'no decision has been made'. That is pretty unavoidable, as otherwise there would be need to eventually store several million tons of processed cooling water.
The rest of the work is going deliberately slowly, which seems sensible.
There is no prospect of doing much with the reactors in this decade, apart maybe from emptying the spent fuel pools.
So why hurry, if all of the work has to be done by humans? Better to play for time and push the teleoperator technology forward as fast as possible. That way Japan might also hopefully still get something useful out of this disaster.