Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Cire]

Well the Daini plants reached cold shutdown.

As of 3:00 pm on August 29, the reactors of Unit 1 to 4 are in cold
shutdown (please refer to the appendix). We will continue to make our
endeavors to further stabilize each plant of cold shutdown.

 

[joewein]

Yes, but the last Daini unit to reach cold shutdown was on http://www.tepco.co.jp/en/press/corp-com/release/11031501-e.html", not anything that happened recently.

I am curious if TEPCO is still planning on restarting operations at Daini (maybe after a few years) even though it's almost 10 km inside the Daiichi exclusion zone.

I am curious what other purpose the inspection of the containment serves. Are they suspecting internal damage?

 

[joewein]

Well, they [plutonium/neptunium, JW] are both (in their metal form) somewhat soluble in water. During the meltdown, some of the metal oxide gets reduced and seawater is mildly alkaline. I don't know if it's the only mechanism, but some of the plutonium mst have left with the steam.

Plutonium and neptunium (as well as uranium) are http://www.meta-synthesis.com/webbook/36_eneg/electroneg.html" than hydrogen, so even if their metallic form was present while there was still steam around, they should get reoxidated by steam similar to the zirconium reaction.

In fact plutonium is more electropositive than zirconium (in the fuel rod cladding), so it might grab oxygen from zirconium that had reacted with steam already. On the other hand, metallic plutonium boils at a lower temperature than metallic zirconium, so that might shift the balance the other way.

If any metallic plutonium was evaporated in the core, I expect it would react back to oxide with the steam and turn into an oxide aerosol before it has a chance to meet liquid water again.

 

[etudiant]

Plutonium and neptunium (as well as uranium) are http://www.meta-synthesis.com/webbook/36_eneg/electroneg.html" than hydrogen, so even if their metallic form was present while there was still steam around, they should get reoxidated by steam similar to the zirconium reaction.

In fact plutonium is more electropositive than zirconium (in the fuel rod cladding), so it might grab oxygen from zirconium that had reacted with steam already. On the other hand, metallic plutonium boils at a lower temperature than metallic zirconium, so that might shift the balance the other way.

If any metallic plutonium was evaporated in the core, I expect it would react back to oxide with the steam and turn into an oxide aerosol before it has a chance to meet liquid water again.

Thank you for this quite illuminating comment.
It makes a lot more sense than the stories of fuel fragments flung for miles, but in a real way is more troublesome. It implies that the emissions from a meltdown are even more lethal than the relatively short lived cesium contamination. Cesium is excreted by adults in a couple of months, whereas plutonium tends to stay in the body afaik, barring heroic measures such as chelation therapy.

 

[zapperzero]

Plutonium and neptunium (as well as uranium) are http://www.meta-synthesis.com/webbook/36_eneg/electroneg.html" than hydrogen, so even if their metallic form was present while there was still steam around, they should get reoxidated by steam similar to the zirconium reaction.

In fact plutonium is more electropositive than zirconium (in the fuel rod cladding), so it might grab oxygen from zirconium that had reacted with steam already. On the other hand, metallic plutonium boils at a lower temperature than metallic zirconium, so that might shift the balance the other way.

If any metallic plutonium was evaporated in the core, I expect it would react back to oxide with the steam and turn into an oxide aerosol before it has a chance to meet liquid water again.

I was thinking about a scenario where quenching with seawater succeeded - the surface of the corium would have come in contact with liquid water. Much lower temps and availability of anions (esp. hydroxil) would change the picture yu're painting somewhat.

Re boiling point: for Pu it is over 3200 while Zr is around 4300. You must be thinking of melting points - 640 and 1855 respectively.

EDIT: there's even a paper, for those of you who have access
http://www.sciencedirect.com/science/article/pii/S0969804301000975

LATER EDIT: chemical analysis of the water they are recirculating would tell us more.

 

[tsutsuji]

http://www.asahi.com/national/jiji/JJT201108290140.html 2 workers have been exposed to 23.4 and 17.1 mSv of beta radiations while changing filters at the desalination facility yesterday. The condition of a third worker is not known yet.

http://www3.nhk.or.jp/news/html/20110830/t10015234611000.html While it is above the 15 mSv planned exposure, it is less than the legal limit of 1000 mSv in emergency situations for beta rays. The workers were changing filters with gum gloves. Tepco will check if anything is wrong either with the working method or with the equipment.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110830/1230_hibakuryou.html The Ministry of Health and Labour will cancel by next Autumn the decision taken in March to allow worker exposure up to 250 mSv / year. The limit will come back to 100 mSv like before the accident. No worker has been tested above 100 mSv since April.

Decommisionning Fukushima Daiichi:

It is believed that raising water levels inside the reactor has been difficult because of a hole in the bottom of the vessel. It will be necessary to plug the hole, and continue filling the vessel with water while extracting the melted fuel. How to fill the vessel with water is still being debated.
http://mdn.mainichi.jp/mdnnews/news/20110828p2a00m0na002000c.html

 

[Bandit127]

http://www3.nhk.or.jp/news/html/20110830/t10015234611000.html While it is above the 15 mSv planned exposure, it is less than the legal limit of 1000 mSv in emergency situations for beta rays.

Thanks for your valuable contribution as always.

I suspect this should be 100 mSv though.

 

[SteveElbows]

Dose equivalent rates inside Daini reactor 4 containment have been published, and don't appear unusual to me:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110830_04-e.pdf

Looks like they have found a problem with a pump at Daini reactor 2:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110830_03-e.pdf

http://www.tepco.co.jp/en/press/corp-com/release/11083014-e.html

 

[SteveElbows]

What happened with the plan to spray water into reactor 3 from a different point? I've not seen it mentioned since they announced they were going to try it, and I certainly haven't seen temperatures falling.

 

[tsutsuji]

[URL]http://www.tepco.co.jp/en/news/110311/images/110830_4t.jpg[/URL]
http://www.tepco.co.jp/en/news/110311/images/110830_4.jpg

http://mainichi.jp/select/jiken/news/20110607ddm003040107000c.html :

It was discovered that the 13 km long Yunotake fault which runs in Iwaki city 40 km south of Fukushima Daini was activated by aftershocks of the 11 March earthquake. The problem is that this fault had been overlooked in past earthquake safety designs. NISA instructs all NPP operators to review their earthquake safety assessments to ensure similar faults elsewhere are not being overlooked.

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110831/0515_katsudansou.html Replying to the NISA request concerning the 11 April aftershock, Tepco has checked the faults around Fukushima Daiichi and Daini and found 5 faults, including the South-North running Hatakegawa fault West of the plants (1), and faults on the sea bed South-East of the plants (2) where Earth crust deformation was confirmed whereas this had previously been dismissed. Tepco is confident that the faults cannot produce earthquakes stronger than the plants' earthquake resistance design can resist, but will conduct detailed surveys about the faults, including the use of boring techniques.

(1) a map of this fault is available on pages 53,54,55 (pdf numbers 54,55,56) of http://www.tepco.co.jp/nu/material/files/ga08080401.pdf (2008)
(2) http://www.tepco.co.jp/nu/material/files/ga08080401.pdf (2008) p. 64-68

http://www.47news.jp/CN/201108/CN2011083001000448.html The Yunotake fault is included in the 5 faults reported by Tepco. Concerning the Japco and Jaea facilities in Tokai-Mura, 9 faults were reported to NISA. All in all, 5+9=14 faults were reported to NISA.

 

[tsutsuji]

I suspect this should be 100 mSv though.

I was surprised with this alleged legal "1000 mSv" too. In the same sentence it is said that beta rays affect the skin but cannot move to other parts of the body. Mainichi says exactly the same as NHK in http://mainichi.jp/select/weathernews/news/20110830ddm002040102000c.html "Because it can't move from skin to other parts of the body, the legal limit is 1000 mSv". http://www.asahi.com/national/update/0829/TKY201108290599.html doesn't speak about any legal limit, and in addition to the beta ray data, provides the gamma ray data of the two mentioned workers: 0.28 and 0.22 mSv. It was the first time the filters were being changed. An alarm should ring whenever high radiations are detected. Tepco has yet to investigate whether any alarm rang.

What happened with the plan to spray water into reactor 3 from a different point? I've not seen it mentioned since they announced they were going to try it, and I certainly haven't seen temperatures falling.

Just my two pence, but if some corium has melt through, the problem is located lower than the RPV bottom. So It would not be surprising if adding more cooling in the top part of the RPV won't help much.

 

[joewein]

What happened with the plan to spray water into reactor 3 from a different point? I've not seen it mentioned since they announced they were going to try it, and I certainly haven't seen temperatures falling.

Just my two pence, but if some corium has melt through, the problem is located lower than the RPV bottom. So It would not be surprising if adding more cooling in the top part of the RPV won't help much.

So perhaps indirectly the fact that temperatures were *not* falling tells us something about how much of the corium is located where, which is useful.

EDIT: I checked the original release again:
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110823_01-e.pdf

The switchover to the core spray line was supposed to start on August 26. That would make today (Aug 31) day 5, with 5 m3 injected through the feed water line and 3 m3 through the core spray line. However, today's 1F status release mentions nothing of core spray injection:
http://www.tepco.co.jp/en/press/corp-com/release/11083101-e.html

Water is currently injected at approx. 7.0 ㎥/h through reactor feed water system piping arrangement.

It looks pretty much like the previous arrangement. Perhaps the experiment has been delayed but I have seen no announcement about any delay or reasons for it.

 

[rmattila]

A new release dated today concerning the core spray line-up:
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110831_02-e.pdf

No date given as to when the feed through the spray line will be / has been started.

 

[tsutsuji]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110831/index.html Two workers have been showered with radioactive water at the decontamination facility on 31 August, receiving 0.14 and 0.16 mSv. While working at removing water from a spent adsorption vessel, one worker who was on a ladder unplugged a hose without being aware that the corresponding valve was still open. The other worker who was holding the ladder below was showered too. ( See English version at http://www3.nhk.or.jp/daily/english/31_34.html )

"TEPCO presents plan to extract melted rods":

The first 3 stages of TEPCO's plan are devoted to removing radioactive materials from the reactors' buildings to repair containment vessels and stop water leaks.

The utility plans to then put water in the vessels and take pictures to determine the amount of nuclear fuel that has leaked from the reactors.
http://www3.nhk.or.jp/daily/english/31_32.html

http://www.tepco.co.jp/en/press/corp-com/release/11083105-e.html Basic Design of Water Shield Wall at the Seaside

http://www.tepco.co.jp/cc/press/betu11_j/images/110830t.pdf Tepco's big report (280 pages, 97MB, in Japanese) about the faults surrounding Fukushima Daiichi and Daini and Kashiwazaki-Kariwa. The abstract is smaller, with only 5 pages : http://www.tepco.co.jp/cc/press/betu11_j/images/110830a.pdf (Japanese)

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110831e9.pdf Water treatment weekly report for the 24-30 August week : 10,970 tons (or 131% of 8400=50 tons/hour*24hours*7days), including 3480 tons processed by SARRY.

 

[clancy688]

"TEPCO presents plan to extract melted rods":

So they want to remove fuel which leaked from the RPV into the containment structure? I thought there were little to no fuel leaks and only holes through which water escapes, not fuel.

Not that leaking fuel hasn't been discussed here... but I thought TEPCO never quite acknowledged that actual fuel escaped from the RPVs?

 

[tsutsuji]

So they want to remove fuel which leaked from the RPV into the containment structure? I thought there were little to no fuel leaks and only holes through which water escapes, not fuel.

Not that leaking fuel hasn't been discussed here... but I thought TEPCO never quite acknowledged that actual fuel escaped from the RPVs?

There is more information on the website of the Atomic Energy Commission of Japan's Fukushima middle and long term special committee:

http://www.aec.go.jp/jicst/NC/tyoki/sakutei/siryo/sochi2/siryo1.pdf "Images of the work to remove fuel from the pools and from the cores" by Tepco (A sort of manga showing the pool fuel's 5 steps and the core fuel's 9 steps). On the diagrams some melt-through corium is shown with dotted lines. Step 9 is the final step when the corium is removed: the red lettered text says "(especially concerning the removal of the fuel located inside the primary containment vessel, there is no prior experience of this, even at TMI)". The the black lettered text concludes: "Development of technology and methods of a higher level than those from TMI".

http://www.aec.go.jp/jicst/NC/tyoki/sakutei/siryo/sochi2/siryo2.pdf "Necessary research and development topics and contents" by JAEA, Toshiba and Hitachi-GE Nuclear Energy.

http://www.aec.go.jp/jicst/NC/tyoki/sakutei/siryo/sochi2/siryo3.pdf Document contributed by special committee member Satoru Tanaka (opinion)

http://www.aec.go.jp/jicst/NC/tyoki/sakutei/siryo/sochi2/siryo4.pdf Minutes of the 3 August meeting

 

[robinson]

As always, thanks for the information and translation.

 

[tsutsuji]

Let's translate the core fuel removal 9 steps of http://www.aec.go.jp/jicst/NC/tyoki/sakutei/siryo/sochi2/siryo1.pdf . First of all, Tepco insists that this is only an example and that no firm decision has been taken yet. On difficult technological problems, alternative solutions will be studied and whenever necessary the alternative solution shall be used.

① Decontamination inside the reactor building
(To be performed each time it is required by the following step ② and later steps)

To enhance accessibility to the primary containment vessel, the working area is decontaminated using high pressure water, coating, surface removal, etc.
♦ High radiation spots (some 100~1000 mSv/h) are present
♦ Access is restricted by the debris inside the building.
・Studying and establishing remote-controlled decontamination methods taking the above into account is necessary.

② Primary containment vessel leakage survey ; Survey of the inside of the primary containment vessel, performed from outside

Leakage in primary containment vessel and reactor building is surveyed using remote controlled radiation measurements, cameras, etc. The status of the inner parts of the primary containment vessel is infered from the outside using gamma ray measurements, ultrasonic testing, etc.
♦ The surveyed objects are high radiation areas, areas flooded with contaminated water, narrow parts, etc.
・Development of methods and equipments for the leakage points survey
・Development of methods and equipments for the survey of the inside of the primary containment vessel, performed from outside

③ Waterproofing of reactor building ; Repair of the lower part of primary containment vessel
- - - - - - - - - - - - - -
If the waterproofing of the reactor building is achieved, the intake of the closed loop cooling water system can be switched from the turbine building accumulated water to the torus chamber.
- - - - - - - - - - - - - -

Waterproofing is performed, leakage points are repaired considering also that, for radiation shielding purposes, fuel removal is best performed underwater. With the primary containment vessel internal survey goal in mind, the lower part will be given priority.
♦ Waterproofing is performed under exposure to high radiation, while water is flowing, as water injection goes on as part of the closed loop reactor cooling system
・Development of leakage repair techniques and methods
・Study and development of alternative solutions

(to be continued)

 

[tsutsuji]

④ Partial filling of primary containment vessel
- - - - - - - - - - - - - -
If the boundary construction in the lower part of the primary containment vessel is achieved, the closed loop cooling water system's intake can be switched from the torus chamber to the primary containment vessel
- - - - - - - - - - - - - -

Heading toward the survey inside the primary containment vessel, water filling is performed in the lower part of the primary containment vessel
♦ same as ③
・Boundary construction in the lower part of the primary containment vessel (including the proposal to fill the torus chamber with grout) is a major prerequisite.

⑤　Primary containment vessel internal survey and sampling

Inspecting inside the primary containment vessel, the distribution of damaged fuel assumed to have flowed down from the reactor pressure vessel is understood. Sampling, etc. is performed.
♦ It is unclear how much accessibility is restricted due to the high radiations. The environment inside the primary containment vessel (such as the water turbidity or the whereabouts of damaged fuel) is unclear
・Considering the above, development of remote-controlled surveying and sampling methods.

⑥ Repair of the upper part of primary containment vessel

Because the primary containment vessel must be completely filled with water, its upper part is repaired using remote-controlled or manual tools.
♦ same as ②
・Development of primary containment vessel leakage repair and waterproofing techniques and methods　(same as ③)

(to be continued)

 

[tsutsuji]

⑦ Filling primary containment vessel / reactor pressure vessel with water ⇒ reactor pressure vessel cap opening

After sufficient radiation shielding is provided by filling both the primary containment vessel and the reactor pressure vessel with water up to the suitable level, the reactor pressure vessel cap is taken off.
・The boundary construction as provided by ⑥ is a major prerequisite

⑧ Survey and sampling inside reactor

Surveying inside reactor, the status of the damaged fuel and the status of the structures inside the reactor is understood. Sampling, etc. is performed.
♦ It is unclear how much accessibility is restricted due to the high radiations. The environment inside the primary containment vessel (such as the water turbidity or the whereabouts of damaged fuel) is unclear
・Considering the above, development of remote-controlled surveying and sampling methods.

⑨　Core fuel removal

Damaged fuel removal from the reactor pressure vessel or from the primary containment vessel is performed.
♦ Depending on the damaged fuel distribution, the technical development domain grows (especially concerning the removal of the fuel from inside the primary containment vessel, there is no prior experience of this, even at Three Mile Island).
・Development of technology and methods of a higher level than those from Three Mile Island.

 

[rmattila]

A new release dated today concerning the core spray line-up:
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110831_02-e.pdf

No date given as to when the feed through the spray line will be / has been started.

From http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110901_05-e.pdf:

9/1:
14:09 We started to control the water flow into the reactor Unit 3 in order to start water injection by core spray system
14:20 We started injection by core spray system
14:58 We controlled the rate of water injection by reactor feed water system at the level of approximately 7.0 m3/h and the rate of water injection by core spray system at the level of approximately 1.0 m3/h

 

[zapperzero]

Depending on the damaged fuel distribution, the technical development domain grows (especially concerning the removal of the fuel from inside the primary containment vessel, there is no prior experience of this, even at Three Mile Island).

The mind boggles. They propose to do three quarters of the job flying blind. Someone at TEPCO really, really does not want to know where the corium is.

Interesting that they assume the upper parts of the PCVs will need repairs.

 

[etudiant]

⑦ Filling primary containment vessel / reactor pressure vessel with water ⇒ reactor pressure vessel cap opening


Thank you tsutsuji for your continued insight and coverage of this situation.

It seems that TEPCO (and by extension the Japanese government) are gradually preparing the way for a decade long cleanup effort.
The engineering cost of the task sheet outlined in your post is surely way in excess of the construction cost of this plant. Robotically inspecting and repairing a damaged and highly radioactive site is truly a first. The tools will need to be developed and debugged before any real work can begin. That is far beyond TEPCOs financial capacity, so there will be Japanese government programs to fund these advances. As ex Finance Minister, Mr Noda should have no trouble with that.
In addition, the site will need to be extensively cleaned up beforehand. Ay guess is all of 2012 will be needed just for that site cleanup phase, so there is plenty of time for the engineering designs to be refined.
Imho, if the effort simply gets the spent fuel pools cleared, it will already be a major achievement. Cleaning out the reactor fuel after a meltdown is a much more difficult task. If it took more than a decade to perform that at TMI, there is little chance of TEPCO doing it faster, especially as the task is much bigger.
A 20 year time frame seems fairly reasonable.

 

[Bodge]

Strange looking storm approaching

 

[zapperzero]

Strange looking storm approaching

I am not familiar with this subject at all. In what way is the storm strange?

 

[tsutsuji]

http://mainichi.jp/select/weathernews/20110311/news/20110831k0000m040149000c.html Concerning the beta ray exposure accident during filter change, it was learned that the alarm rang when 15 mSv was reached, but as the work was close to the end, the three workers decided to finish the job. The third worker had 1.1 mSv. [beta or gamma?]

http://www3.nhk.or.jp/news/genpatsu-fukushima/20110901/index.html After 6 PM on 31 August, one water treatment facility worker was found with radiations at his wrist and elbow, at a level exceeding the limit forbidding workers to leave the plant. His exposure for his job on that day was 0.89 mSv. It is suspected he was splashed with contaminated water. The NISA has orally instructed Tepco to perform improvements over the last 3 worker exposure accidents at the Water treatment facility (the beta ray accident on 28 August, and those on 31 August), saying that Tepco failed from learning from prior lessons and was late in reporting.

http://www3.nhk.or.jp/news/html/20110902/t10015313662000.html The NISA instructed Tepco to build plans dealing with the possibility of beta exposure before starting any job, in addition to the gamma ray plans.

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110901_01-e.pdf drawing of the two workers who were splashed while working with the ladder on 31 August. [They mean "ladder" not "rudder" : both words are spelled "radaa" in Japanese, which makes the confusion quite easy]

* At around 3:00 pm on August 31, we confirmed water leakage near the sludge transfer pump (B) for the coagulation settling instruments inside the water treatment system (decontamination instruments). We bypassed a part of the coagulation setting instruments and segregated the pump's surroundings, then the leakage stopped. The treatment of the accumulated water is continuing.
http://www.tepco.co.jp/en/press/corp-com/release/11090102-e.html

[URL]http://www.tepco.co.jp/en/news/110311/images/110901_1t.jpg[/URL]
http://www.tepco.co.jp/en/news/110311/images/110901_1.jpg The water leakage spot of the sludge transfer pump casing (pictured on August 31, 2011)
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110901_04-e.pdf Outline drawing of the water leakage spot of the sludge transfer pump casing

20 August Fukuichi Live camera, west side steel truss assembly
26 August Fukuichi Live camera, north side steel truss assembly

(TBS) The NISA said 15 among the 38 troubles that occurred at the water treatment facility since June are human errors.

Looks like they have found a problem with a pump at Daini reactor 2:

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110830_03-e.pdf

http://www.tepco.co.jp/en/press/corp-com/release/11083014-e.html

http://www.meti.go.jp/press/2011/08/20110830010/20110830010.pdf The Daini pump incident is classified as INES level 0 by the NISA: the reactor is in cold shut down so the HPCS was not needed. External power and two other diesel generators were still available. No radiation released.

Emergency drill simulating earthquake and tsunami, followed by blackout at Hamaoka NPP on 1 September.

 

[Bodge]

I am not familiar with this subject at all. In what way is the storm strange?

It had a very interesting structure, with a HUGE eye, nothing that strange *really* lol

 

[Astronuc]

Strange looking storm approaching

It looks like a cyclone/typhoon/hurricane.

 

[Astronuc]

So they want to remove fuel which leaked from the RPV into the containment structure? I thought there were little to no fuel leaks and only holes through which water escapes, not fuel.

Not that leaking fuel hasn't been discussed here... but I thought TEPCO never quite acknowledged that actual fuel escaped from the RPVs?

Sure they did. They acknowledged the fuel melted, which means it communicated with whatever coolant the plant personnel were able to get into the RPV, and any coolant that escaped carried fuel with it.

Well before the fuel melts, the cladding fails by rapid oxidation, PCMI and/or creep rupture, and the exposed fuel is oxidized by the coolant to higher order oxides: usually UO₂ => U₄0₉ => U₃0₈ => UO₃, which is readily soluble. The UO₂ oxidizes along grain boundaries, so fuel particles can wash out. Even if the RPV remains intact, there is likely a large amount of fuel in the coolant.

They should have been able to determine degradation of the fuel by presence of Np-239 in the coolant, as well as significant TU concentrations.

 

[Astronuc]

♦ Depending on the damaged fuel distribution, the technical development domain grows (especially concerning the removal of the fuel from inside the primary containment vessel, there is no prior experience of this, even at Three Mile Island).
・Development of technology and methods of a higher level than those from Three Mile Island.

Um - I would expect that the core damage looks similar to that of TMI-2. At TMI, they had to remove the 'rubble' which considered of fuel material, disintegrated structural material, and disintegrate control rod material. That's pretty much what they have to do in the core of FK1-1, FK1-2 and FK1-3. There may be no such experience in Japan, but there is experience in the US.

In addition, I would expect that they have not even looked at the fuel, so I don't understand how anyone there could make such a definitive statement.

If the bail of the fuel assembly is sitting at the top of the channel, then the fuel is likly not damaged. In that case, they should be able to grapple the assembly.

If the bail and channel lift without the assembly, then they'll have to employ a fishing tool, which takes advantage of the large central water rod, and the somewhat open bottom tie plate, in the STEP II fuel.

 

[joewein]

Emergency drill simulating earthquake and tsunami, followed by blackout at Hamaoka NPP on 1 September.

September 1 is the anniversary of the 1923 Great Kanto Earthquake and is commemorated every year as a disaster preparedness day in Japan.

 

[zapperzero]

Sure they did. They acknowledged the fuel melted, which means it communicated with whatever coolant the plant personnel were able to get into the RPV, and any coolant that escaped carried fuel with it.

Were that the situation was so good. It is not, apparently.

http://www.telegraph.co.uk/news/wor...s-melted-through-base-of-Fukushima-plant.html

 

[alpi]

Were that the situation was so good. It is not, apparently.

http://www.telegraph.co.uk/news/wor...s-melted-through-base-of-Fukushima-plant.html

Why bother with a British newspaper saying that a melt-through is "the worst possibility in a nuclear accident"? The previously melted fuels are solids heavy as lead and are not going anywhere.

 

[zapperzero]

Why bother with a British newspaper saying that a melt-through is "the worst possibility in a nuclear accident"?

I don't care one bit about their opinions. Why would you raise such a trivial issue?

They are reporting the following: that the J-gov believes the RPV bottoms to be breached and significant quantities of fuel to be strewn around on the PCV floor below, where significant means "tons, in the form of rubble/melt" not "decagrams, dissolved in water".

Do you have anything to say with regard to the facts they are reporting, or are you just trying to derail the conversation?

The previously melted fuels are solids heavy as lead and are not going anywhere.

This one sentence is so full of wrong/unsupported I don't even know where to begin.
Oh well. For the sake of completeness.

1. "previously melted [...] solids" is unsupported by evidence. Due to decay heat, at least part of the corium could be molten NOW, even if it does have a crust (which we don't know for sure), especially if it's all in the same place, as in an optimistic scenario where most of it is still in the RPVs.

2. "fuels" is just wrong. There's fuel, control rods, racks, bits of shroud and Thor knows whatever else.

3. "heavy as lead" is wrong. Molten lead has a density of 10 g/cm^3. Molten Uranium has a density of 17 g/cm^3.
At TMI, the solidified corium rubble, which was made up of mostly Zirconium Oxide and Uranium Oxide, was found to have an average bulk density of around 8 g/cm^3.

4. "not going anywhere" is unsupported. Are you implying it's immobile because it's heavy? It's also generating heat, so it may still be flowing, albeit slowly. If you have evidence to the contrary, feel free to present it.

 

[clancy688]

They are reporting the following: that the J-gov believes the RPV bottoms to be breached and significant quantities of fuel to be strewn around on the PCV floor below, where significant means "tons, in the form of rubble/melt" not "decagrams, dissolved in water".

I'd like to see their sources, or at least know where they are and ask tsutsuji to provide a translation.

Anyway, let's assume that's correct. So there are actually tons of molten corium in the containment below the RPV. TEPCO now wants to clean up that mess. But how? It's probably a big, multi-ton heavy blob of concrete, steel, fuel rods, control rods and god knows what else which's lying somewhere in the catacombs of Units 1-3. How do you remove such a mess? You can't possibly take the blob as a whole. So you'd need to take it apart. Which's impossible since the fuel rods are no longer neatly separable. And how will you saw something into pieces which kills every human over a course of minutes and which dust (which will be generated while sawing) is probably the most dangerous and longest living poison in the history of mankind?

How did they remove the molten fuel from TMI? How were they able to break the molton mass apart without hazarding the workers?