Japan Earthquake: nuclear plants Fukushima part 2

[Sotan]

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201508100012
Kyushu Electric announces Sendai nuclear plant reactor restart set for Aug. 11

Maybe not directly related to Fukushima... but then of course it is, in many ways.
Thought I mention it anyway.

"Japan has gone a year and 11 months with no nuclear power plants in operation [...]".
I don't know why but I thought it has been much longer.

 

[Hiddencamper]

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201508100012
Kyushu Electric announces Sendai nuclear plant reactor restart set for Aug. 11

Maybe not directly related to Fukushima... but then of course it is, in many ways.
Thought I mention it anyway.

"Japan has gone a year and 11 months with no nuclear power plants in operation [...]".
I don't know why but I thought it has been much longer.

I think one or two units were allowed to operate through their next fuel cycle. But all plants except one that tripped off after the earthquake weren't allowed to restart.

 

[turi]

The IAEA report is here:
http://www-pub.iaea.org/books/IAEABooks/10962/The-Fukushima-Daiichi-Accident
Happy reading...

 

[ronaldkr]

Thanks, Turi.

Please note that only the leafy wood-based version is priced with 60 EUR. The PDFs of chapters and annexes can be downloaded for free (and in additional languages too). Seems worthwhile.

Happy downloading...

 

[turi]

The subdrain and groundwater draining operations are set to start:
http://www.tepco.co.jp/en/press/corp-com/release/2015/1259088_6844.html

 

[Sotan]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2015/images/handouts_150909_12-j.pdf
Tepco report in Japanese regarding the results of a camera investigation in relation to the hatch of PCV of Unit 3

I do not recall but apparently in 2011 they discovered radioactive water in the vicinity of this hatch - more exactly, on the rails that serve to move the "shield plug" - and therefore assumed there might be a leak there, with water from the dry well seeping up from the hatch.

Now they managed to insert a small camera through the space around the shield plug. Several photos are shown. The floor seems wet and there is stuff such as flakes of paint scattered on it, and there is still water in the rails of the shield plug, but they found no leak from the hatch and the hatch itself seems intact. They saw droplets of water falling down from above - they assume it's rainwater or condensation water.

This investigation required the work of 5 men, with a planned exposure of 2.2 mSv per person. Highest recorded exposure was 0.99 mSv, total exposure for the team was 3.62 mSv.

Page 5-6 show that in October they plan to make additional observations in the area (after mockup training) by sending in a small robot that carries a... mobile phone, if I understand correctly, with camera and lighting. The robot will be steered by remote control by operators sitting outside of the "double door" of the reactor building (to help reduce their exposure). The camera will be tilted slightly downwards so as to be able to see the floor and thus help with robot steering.

(I am not very confident about the above report as I don't really understand what's in the area and why this is important. Maybe they are just thoroughly checking the leak hypothesis?)

 

[Sotan]

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2015/images/handouts_150909_01-e.pdf
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2015/images/handouts_150910_01-e.pdf
English language reports regarding the "Seaside Impermeable Wall Closing Operation"

 

[URob]

Not sure if there is dedicated scaremongering forum so I'll leave this here.

http://www.counterpunch.org/2015/09/30/the-worlds-never-seen-anything-like-this/

 

[Cire]

Not sure if there is dedicated scaremongering forum so I'll leave this here.

http://www.counterpunch.org/2015/09/30/the-worlds-never-seen-anything-like-this/

That's nothing more then FUD and propaganda disguised as a poorly written article.

Where is the fuel? If it's not in the bottom of the reactor vessel its under it. It's not on Mars, its not on the west coast of the United states. Giant mutant fish and flowers didn't eat it. Do we need to take anyone seriously that uses the term "Mother Earth?" in a faux technical article? Where does the author think the fuel came from originally?

Once again we see these propagandizers pushing the proven to be false linear no-threshold theory. We only need to find one example of a theory failing to know its invalid. There are plenty of examples of people with high radiation exposure that never develop cancer or related diseases. Many of these people are atomic bomb survivors, scientists, etc. Take a look at several of the atomic bomb test camera men that where close to HUNDREDS of test detonations. A few in their late 80s are still alive today. Cancer free. Most of the cameramen met or exceeded the average life expectancy for men.

The large non-linearity of cancer rates vs. exposure (at the bottom end) blows that theory out of the water. Linear means Linear . The vary name of the theory fails itself; like most of that article.

 

[Sotan]

They completed the removal of the roof panels of Reactor 1 building.

http://www3.nhk.or.jp/nhkworld/english/news/nuclear.html

And two small photos:
http://english.kyodonews.jp/photos/2015/10/377668.html
http://english.kyodonews.jp/photos/2015/10/377667.html

 

[Sotan]

http://www.tepco.co.jp/decommision/planaction/roadmap/index-j.html
There’s an update on Tepco’s site regarding the medium-long term roadmap for decommissioning, dated October 1st.

One PDF files posted there has information on several investigations on the damaged reactors:
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d151001_08-j.pdf

Starting on page 1 (I’m using the page numbers as they are in the PDF file, not what the browser or Adobe Reader displays) there’s info on the investigation of “TIP room”, main steam valves room and “airlock room” of Reactor 1.

Page 2: General info
- because in the area of the entrance of TIP room and main steam valves room the radiation level is high, access will be made by opening a hole in the corridor of the turbine building (where the radiation level is low).
- the SHC room is yet to be investigated too, but radiation is high in this case even in the corridor of the turbine building. Therefore they will study the possibility of accessing the SHC room from the main steam valves room.
- there’s a drawing with the first floor of reactor 1 and the radiation values. The turbine building is at the right side (the gray band is the corridor). SHC and TIP rooms are adjacent to that corridor. Airlock room is on the other side of the PCV. Sorry but at the moment I don’t know the meaning of TIP and SFC.

Page 3: Purpose of the investigation (1)

- TIP room:
- reduction of the radiation level around X-6 penetration (study of the possibility of accessing the AC pipes). X-6 penetration offers a way inside the PCV, but radiation levels in the area must be decreased. For this reason the decontamination of the highly radioactive AC pipes (ducts?) is necessary.
This requires setting an installation for removing radioactive contamination on one side of the AC ducts, at first floor – which means right near the TIP room. The investigation should indicate if access is possible from the TIP room to the highly radioactive AC ducts (they measured more than 1000 mSv/h);
- stopping the water leak of the lower PCV: study of the possibility of sealing the leak in the “vacuum destruction line”, leak discovered right below the TIP room;
- repairs of some electrical connections/cables in the PCV penetrations (these require human operators, so again a reduction in radioactivity of the area is strictly required);
- studying the possibility of accessing the SHC room and the main steam valves room.

Page 4: Purpose of the investigation (2)

- Main steam valves room:
- study of the possibility of repairs in the PCV; study of the access to PCV penetrations. Welding and filling are the the two methods envisaged for “repairing” some of these penetrations; if human access will be deemed impossible, filling will be the only method left.

- Airlock room:
- examination of the area around the X-53 penetration, especially of the traces/leaks of highly radioactive water observed on the floor of the Airlock room, leading to the funnel on the floor; also study the possibility of doing some repairs in the area of the penetration if needed.

Page 5: Drawing of the areas targeted for investigation

Page 6: The devices to be used. A visible light camera on wheels, a 3D scanner, a gamma camera and a radiation level detector.

Page 7: Schedule.
Seems that the TIP room and main steam valve room investigation is actually on the way.
The decontamination of the various rooms should begin during 2016.
Repairs to the PCV – probably to start in 2018.

Pag. 8: Additional info
The aimed radiation level, after decontamination, is 3 mSv/h for the working areas and 5 mSv/h for access routes. The main sources of radiation are the inside surfaces of the AC and DHC pipes/ducts, but also walls, floors and machinery surfaces. Shielding of some surfaces – insufficiently decontaminated – might also be required in the end.
The gamma camera images in the right suggest 300-500 mSv/h for DHC pipes and 1000-1200 mSv/h for AC ducts.

Pag 9: Additional info on the decontamination plans for the AC ducts

Pag 10: Additional info on the decontamination plans for the DHC pipes
- It is known that the DHC pipes and the adjacent RCW pipes are all highly contaminated. The first step would be emptying the pipes through the existing valves; removing the contaminated water should decrease the radiation level. Washing/rinsing/drying the pipes could help too (the main contaminant, Cs, is soluble in water). The removal of water should be done through the existing structures: drainage pipes -> gathering funnel -> floor funnel -> reactor building torus room sump pit) if it is deemed usable. Complete removal of the DHC pipes will be considered in the end.(…the document continues with the progress of investigations on R2 and R3. Will have to post later about those, ran out of time for now.)

 

[Sotan]

http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d151001_08-j.pdf
(continuation.)

Because the page numbers are reset for each section, this time I must refer to the page numbers as shown in the browser or in Adobe Reader (the PDF file page numbers in parantheses)

Page 14 (1): The “A-2 investigation“ – the inside of the pedestal and platform of Reactor 2. Update on the removal of the concrete blocks in front of X-6 penetration.

Page 15 (2):
- The removal of the concrete blocks started on June 11 – as preparation for the A-2 investigation inside Reactor 2, scheduled for August. By June 26 128 of the 136 concrete blocks had been removed. The remaining 7 blocks were found stuck in a way that resisted all efforts and required further planning. The operation was suspended on July 8 and resumed on September 28.

Page 16 (3): general drawing to show the concrete block removal operation. A grasping device is used to loosen and remove the metal plate located beyond the concrete blocks. After that the device hopefully can grasp the concrete blocks themselves. There’s 4-6 mSv/h behind the first shielding and another shield protects the operator.

Page 17 (4):
Sep 28: The metal plate was loosened. However the grasping device slips on the metal, preventing the lifting of the plate.
Sep 29: Rubber is added to the grasping device in order to prevent the slipping, but the grip is still insufficient unsuccessfully. Some WD40-like liquid has also been sprayed for a while on the stuck surfaces seams, helping to dissolve rust and loosen the connections.

Page 18 (5):
Some “clamps” have been added to the grasping device. This time the grip was good enough and the metal plate could be removed from behind the concrete blocks. The photo on the right shows the view towards the X-6 penetration lid after the removal of the metal plate.

Page 19 (6):
The concrete blocks were finally removed. Photos shown are “before” and “after”.

Page 20 (7): Schedule
The actual investigation will be done after the decontamination of the area to reduce the radiation levels. Therefore the date is not yet clear.- And the third report:

Page 21: Results of the video camera investigation of the “machinery hatch” in the PCV of Unit 3
(not sure about the “machinery hatch” translation)

Page 22 (1) Purpose of the investigation:
- regarding the Unit 3 PCV machinery hatch (reactor building, 1st floor, North side)
In 2011 highly radioactive water has been found in the area of the rails for moving the shield plug, suggesting the possibility of a leak through the seal of the machinery hatch. Therefore the plan is to insert a camera through the openings available around the shield plug and check the surroundings.

Page 23 (2) General drawing
A camera is attached on a 2.1m aluminum stick. The images taken by the camera are visible on a portable screen held by the operator and at the same time recorder on a microSD card. The drawing at the right shows the shield plug pulled back a little, creating those spaces through which the camera will be inserted.

Pag. 24 (3) Results
- paint is gone/fallen from the machinery hatch
- the paper (pad?) for recording periodical checks is still there
- no water leak is seen and the machinery hatch seems intact.

Pag. 25 (4) Results
- chips of paint are gathered on the floor
- small amounts of water are visible in the rails used for moving the shield plug

Pag. 26 (5) conclusions
- no leak from the PCV machinery hatch
- no changes in the shape of the PCV machinery hatch
- the inside surfaces of the shield plug appeared humid and there was water in the rails used for moving the shield plug
- rain water or condensation water seemed to seep in from the top regions of the shield plug
- chips of paint were gathered on the floor.

Page 27 (6) Additional investigation will be carried out using a small remote controlled robot to check the several places that couldn’t be seen in this investigation.

Page 28 (7) Schedule
A mockup training will be carried in the corresponding region of Unit 5 reactor, and the robot investigation will probably take place sometime in November.

Page 29 (8) The robot to be used
(Now I realize I’ve seen and reported about this before)
Small radio-controlled robot carrying a smartphone to be used as a camera.

Page 30 (9)
A drawing of the various penetrations into the PCV. Horizontal lines indicate their nominal elevations in the PCV. For now a water leak has been confirmed in the area designated as D (in the connecting bellows of some pipe). X-1A is the machinery hatch investigated this time.

(end)

 

[Hiddencamper]

TIP = Traversing Incore Probe.

TIP is a set of neutron fission chambers which are inserted into the core roughly once every month or two and are slowly withdrawn to measure the flux in the core and generate a 3D flux profile. There are 4-6 TIP drive units at a typical BWR. Each probe can go to about 5-6 different locations in the core. For a max of 36 locations. The TIP probes spend very little time in the core and have very low uranium depletion, meaning their voltage/current characteristics don't really change, making them very useful for calibrating the LPRMs (local power range monitors) in the core to compensate for detector burnup. The process computer records TIP data during the run, and sends that to the core monitoring computer which then calculates new gain adjustment values so that the LPRM readings are accurate and the flux shape and core monitoring model agree with each other.

The TIP system penetration is a known potential containment leak path. To protect the penetration and ensure it can be sealed even if the probe cable is in the core, the TIP system uses explosive squib valves for forcibly isolating the TIP penetration. This likely did not happen at Fukushima due to the loss of power meaning this is a possible containment release path and is part of why the TIP area might be worth investigating.

SHC is shutdown cooling. The BWR/2 plants and early BWR/3 plants have a separate dedicated shutdown cooling system. I'm not as familiar with this system, but if you could get into SHC piping you'd have a direct path into the containment and reactor vessel.

The machine hatch (also called the equipment hatch) is the large hatch used for moving equipment in and out of containment. For many BWRs the hatch seals are one of the first components to fail during high pressure events, especially if containment is flooded, making it a good thing to investigate for potential PCV leakage. The equipment hatch is one of two containment access hatches, there is also a personnel airlock which is used when you need to enter containment but primary containment integrity is still required (typically between 200 degrees and 5% power)

Hope this helps

 

[mheslep]

They completed the removal of the roof panels of Reactor 1 building.

I'm curious about any method for handling water accumulation / runoff with the roof panels removed.

 

[Sotan]

Thank you Hiddencamper.
A wealth of information, as always - and much needed in the context of my messy translations.

 

[Sotan]

A short presentation of another PDF document from the October 1st update of the Mid and Long Term Roadmap on Tepco’s sit, referring mainly to the spent fuel pools
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d151001_07-j.pdf
(in Japanese)

Progress in removal of large debris from the spent fuel pool of Unit 3

Page 5: diagram of the main steps carried out until now and future schedule. Main issues at the moment: placing of further protective panels over the spent fuel racks and removal of the “cover/lid of the CUW F/D hatch”. Intensive work is under way, with a lot of (most of?) the debris to be removed until the end of November.
- Google informs me that this CUW F/D hatch must be related to the “Reactor Water Clean Up System (CUW)”
(http://www.hitachi-hgne-uk-abwr.co.uk/downloads/UKABWR-GA91-9901-0032-00001-Rev2_P-Ver.pdf)

Page 6: Drawing as of Sep 21 showing the placement of protective panels over the fuel racks and the position of the CUW F/D hatch lid.

Page 7 presents the schedule again.

Pag 8 refers to the incident of Sep 3 during preparation work for the removal of the CUW hatch lid. A pressure hydraulic hose of the steel cutting machine got stuck around the handle of a protective panel, which led to the twisting/loosening of a hose connector and to an oil leak. The oil spread over the surface of the SFP but was controlled using the installed oil barrier/fence.

Pages 9 - 11 show the analysis of the incident, causes and corrective measures for the future. The two types of protective panels have different geometries, the height of the “handle” part is different, they didn’t pay enough attention to the risk of some hydraulic hose touching or becoming entangled to certain parts of the panels already placed in the pool. They will consider these things more carefully, and moreover they will strengthen the inspection of the tools used for cutting/handling the debris.

Page 12: Procedure for removing the CUW F/D hatch lid (1/2)
1 – sweep away small concrete debris from the top of the hatch lid
2 – remove pieces of concrete debris from around the hatch lid
3 – slowly lower the special device built for the purpose of lifting the hatch lid
4 – “encapsulate” the lid in the special device and fix it using 4 hydraulic cylinders, and then lift it up.
The last photo shows the concrete debris mentioned in steps 1 and 2 and the metallic handles envisaged to be used for lifting the lid.

Page 13: Procedure for removing the CUW F/D hatch lid (2/2)
5 – bring the lid to a horizontal position and place it temporarily on a rack protective panel
6 – attach some supplementary anti-drop wires to the lid, then lift it out of water and remove it from the SFP.

Page 14: Mockup trial
- Mockup was built at real size and weight and used to verify the procedure. The hydraulic cylinders can be seen in one of the photos.

Pag 15: Explanations about the CUW hatch
There seem to be 2 of them, South of the SFP (red squares in the first drawing).
The lid to be lifted in this operation is the one marked with the curvy red line.
The lid measures approx. 1 x 1 x 2m and weighs about 2.6 tons.

Page 16: Explanations of the specially designed device to be used for lifting the hatch lid
- It has two lifting "eyes", A for the initial lifting and B for bringing the hanging lid to a horizontal position

Page 17-21: areas of operating floors of Unit 1 and 3 to be sprayed with dust-fixing resine, once a months, over 1.5 liters per square meter. Schedule of this operation and so on.

Page 22: removal of the roof of Unit 1 Reactor Building.

Page 23: work done recently on the operating floor of Unit 3 (decontamination, debris removal etc)

Page 24: number and location of the spent nuclear fuel stored in the Fukushima Daiichi plant.

(end)

 

[Hiddencamper]

Holy dang those reactor water cleanup shield plugs are sideways!

 

[Sotan]

What does that mean, Hiddencamper?
What happened there (if you can speculate) and what are the implications.

 

[Hiddencamper]

What does that mean, Hiddencamper?
What happened there (if you can speculate) and what are the implications.

I'm just trying to figure out how those shield plugs got lifted. Those are very heavy. Was the hydrogen explosion that violent?

I don't know if the reactor water cleanup system isolated or not following the initial LOOP. It probably did, but if they didn't then those filter rooms and the heat exchangers would be in direct communication with the now broken bottom head of the vessel and the recirc loops.

 

[Sotan]

Well, Unit 3 did have the most violent explosion of all - at least it seemed so...
Old video, just to illustrate:

 

[cockpitvisit]

Is TEPCO still pumping water into any of the reactors? We are now 4.5 years away from the accident, so the residual heat should be very low now (IIRC, spent fuel can be put into dry casks after 5 years).

 

[Hiddencamper]

I'm assuming they still are.

At this point the water is for direct radiation shielding and for contamination control more than heat removal.

 

[Bandit127]

In addition, the reconfigured cores will:
Not necessarily follow the "normal rules" for the decay of decay heat so be somewhat unpredictable, certainly outside regulations for active/passive cooling timescales that would apply to neatly ordered and stored fuel rods.
Not be in a reliably measurable depth of water.

I suspect that pumping of water will need to continue until they can characterise the cores and positively work out that it is safe to stop.

 

[eXorikos]

Is TEPCO still pumping water into any of the reactors? We are now 4.5 years away from the accident, so the residual heat should be very low now (IIRC, spent fuel can be put into dry casks after 5 years).

They can be placed in dry storage after 3 years. This depends on the cask type and filling.

 

[etudiant]

Seen that the cores have turned into blobs somewhere beneath the reactors, the current heat production of the fuel may be very different from normal.

 

[nikkkom]

And also, bureaucrats would prefer to not change things, than change things and get the blame for any resulting change. In bureaucrat's logic, if entire building rusts through because of water, the blame goes to whoever started water injection program, not to people who could have stopped it years later, but did not.

 

[Rive]

Seen that the cores have turned into blobs somewhere beneath the reactors, the current heat production of the fuel may be very different from normal.

Due the already removed amount of Cs and such water-soluble stuff, the overall heat production is surely lower than 'normal'.
However, the surface of the stuff might be much lower than necessary to remove that heat on free air, at acceptable temperature.

 

[etudiant]

The bulk of the water inflow into the site currently is groundwater, afaik. Sadly that suggests that rust is inevitable, even if injections are ended.
It may be that TEPCO hopes to transform the situation once the ice dam is fully in place. That might then allow the site to be drained and dried if necessary.

 

[Sotan]

From the most recent "handout" about the plant situation, periodically published by Tepco (this one is from Oct 16; in Japanese)
http://www.tepco.co.jp/nu/fukushima-np/handouts/2015/images/handouts_151016_10-j.pdf

Unit 1, water pumped in: 2.5 m3/h by (main?) water lines; 1.9 m3/h by core spray system. PCV lower region temperature: 25.6 degrees Celsius
Unit 2: 1.9 m3/h and 2.4 m3/h, respectively; 31.5 degrees Celsius
Unit 3: 2.0 m3/h and 2.4 m3/h respectively; 29.9 degrees Celsius.

 

[Sotan]

Also another report is out regarding the visual inspection after the removal of the CUW F/D shield plug from of Unit 3 SFP - mentioned in earlier posts (2 page PDF file, in Japanese)
http://www.tepco.co.jp/nu/fukushima-np/handouts/2015/images/handouts_151016_08-j.pdf

The 2.6 ton concrete shield plug was removed on Oct 15.
A video camera was lowered then in the water to check the 4 fuel bundles that were under the displaced shield plug.
2 of these fuel bundles were found to have slightly bent handles. Check the photos on page 2 - red circles=bent handles, white circles=normally shaped handles.
The amount of rubble is again impressing, as is its missing from the region where the concrete shield plug had been sitting.

 

[etudiant]

It is surprising that TEPCO is still pumping in so much water, more than 4 m3/hr in all three cases. TEPCO engineers could get a pretty reasonable fix on the residual heat generated by the fuel by suspending/reducing injections and then looking at the rate at which the temperature rises in the lower PCV .
Presumably this has been done, even though the results have not been made public.

 

[Sotan]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2015/images/handouts_151020_07-j.pdf
(in Japanese)

An investigation was carried out yesterday into the PCV of Unit 3.

Page 2: A pan-tilt camera, a CCD camera, a radiation meter and a thermometer were inserted into the PCV through the X-53 penetration, then down along the PCV wall.

Page 3: Results from the pan-tilt camera and radiation meter
- No visible damage was observed on structural elements inside the PCV (such as RHR piping, PCV internal lighting elements, electric cabling, D/W spray sparger).
- Radiation measurements in air indicated about 1 Sv/h right near the PCV wall and about 0.75 Sv/h at 550 mm away from the exit of X-53 penetration, inside the PCV.

Page 4: Results from the pan-tilt camera and radiation meter. Photos.
- Left: D/W spray sparger
- Middle: RHR piping and PCV wall
- Right: PCV internal lighting

Page 5: Results from the pan-tilt camera and radiation meter. Photos.
Up-left: A view downwards toward the "inspection platform". The water surface can be seen.
Up-right: RHR piping
Below: Shielding support on the inspection platform

Page 6: Results from the CCD camera and thermometer
- The space between the 1st floor grating and the PCV wall is narrow and obstacles are present. Therefore the investigation went only down to 1st floor grating.
- The investigated portions of the PCV wall did not display visible damage.
- The two photos on the upper row show images of the PCV wall (regions depicted as "a" and "b" in the left-side diagram)
- The photo below shows the region "b" and the narrow space between the 1st floor grating and the PCV wall.

Page 7: Results from the CCD camera and thermometer
- Preliminary results on the water level in the PCV: water surface was confirmed to be somewhere around the upper level of the inspection platform - thus roughly matching previous assumptions (OP ~ 12,000)
- Temperature in air was 26-27 degrees Celsius; temperature in water was 33-35 degrees Celsius.
- The temperature was measured in 7 places (along the red line in the diagram), from the exit of X-53 penetration down to the 1st floor grating.
- It wasn't possible to insert the camera lower beyond the 1st floor grating.

Page 8: Conclusions (everything here was already mentioned above).

Page 9: Schedule from now on.
On October 21 a device will be inserted for taking water samples.
More pan-tilt camera investigation and water samples will be taken on Oct 22 and also possibly on 23 and 26.

Edit: There is also a 2min32s, 88 Mb film which I can't see on this computer, you can find it here:
http://photo.tepco.co.jp/date/2015/201510-j/20151020-01j.html

 

[Hiddencamper]

It is surprising that TEPCO is still pumping in so much water, more than 4 m3/hr in all three cases. TEPCO engineers could get a pretty reasonable fix on the residual heat generated by the fuel by suspending/reducing injections and then looking at the rate at which the temperature rises in the lower PCV .
Presumably this has been done, even though the results have not been made public.

That's only about 17 gallons per minute. Pretty low, well below what I would expect for water cleanup operations.

 

[etudiant]

Very true, but afaik it is essentially the same rate as has been in effect for the last several years. I'm surprised that there has not been more change since 2011.

 

[Sotan]

I remember reading, long time ago, on other sites how some people believed that the explosion that took place at Unit 3 was not a hydrogen explosion, but rather some sort of "nuclear blast", "atomic explosion" and I think I saw some other terms used as well. Many other people tried to debunk that theory, with more or less success, as it happens in such cases.

I don't think that theory has many adepts left, but I was thinking that these findings from the lower PCV of Unite 3 are good proof that such a thing did not happen. The destruction seen in the building - the walls and roof blown away, the FHM, the dislocation of the large concrete shield plugs from the SFP, on one side, and things like lighting fixtures remaining rather intact in the PCV on the other side, indicate to me that the explosion happened in the building, and the interior of the PCV was actually protected from the explosion. I suppose if the PCV is designed to keep stuff in when things go wrong, it works as we; when the things go "bang" outside of it.

Like everybody else, I can't wait until we get more solid information regarding the state of the fuel in the 3 reactors.