Japan Earthquake: nuclear plants Fukushima part 2

[nikkkom]

Monitoring air dose rates from a series of
aircraft surveys 30 months after the
Fukushima Daiichi NPS accident
http://www.nsr.go.jp/english/library/data/special-report_0114.pdf

Looks like gamma levels are decreasing slower now, as expected: the difference in last 10 monts is not that striking anymore.
We'll need to wait 30 years for levels to decrease by about 3-4 times...

 

[Sotan]

http://ex-skf.blogspot.ro/2014/01/fukushima-i-npp-reactor-3-water-leak_19.html

What do the specialists in this forum think of this?
Is this report likely to be true? Do we really have water being poured in the reactor vessel, coming into contact with the fuel/corium and then spilling out through some crack or valve opening? (Aren't the measured radiation/radionuclides readings in this water a bit low for such an hypothesis?) Is it as serious as implied in this link, as in causing urgent need for analysis of all MSIV's in other plants?

 

[Rive]

Do we really have water being poured in the reactor vessel, coming into contact with the fuel/corium and then spilling out through some crack or valve opening? (Aren't the measured radiation/radionuclides readings in this water a bit low for such an hypothesis?)

Non-specialist view: the readings are OK. The water in the basements are contaminated in the very first day, and till that it works as a reservoir: as water pumped in the density slowly decreases, but the amount of the water there and the amount of water pumped in limits the speed of this decrease.

The corium itself is directly washed with ('clear') water for years now: most of its soluble parts are already moved to the basements. The Cs level of its (water accessible) parts should be really low (in relative terms, of course).

 

[zapperzero]

The discussion on Ex-SKF is more about the status of the MSIV. It really should be closed. Generally speaking the steam circuit should be intact and it maybe isn't.

 

[Rive]

Actually, what is the vertical position of these valves?

If there is a leak there, with water which had contact with the core debris, then the water level inside the RPV (or PCV?) should be higher than the vertical position of the valves... ??

 

[etudiant]

The leaking water is somewhat contaminated and is 20 C, versus the 7C temperature of the injected water.
So it is flushing past something warm and radioactive or getting mixed with much warmer and more contaminated water from somewhere higher.
An experienced operator might be able to draw useful inferences from that.

 

[Hiddencamper]

Hey yall.

The "MSIV Room" is often known as the "Steam Tunnel". The steam tunnel contains a LOT of stuff, including shut down cooling (RHR) return, feedwater injection, reactor water cleanup return/injection, the main steam lines, and most of the piping for non-safety interfacing systems to interface with the reactor building/drywell/containment.

Whether or not the MSIVs are leaking is a good question. I know the containment drywell has a relatively high temperature right now (which is why there are occasional reports of steam). Now the main steam lines are above everything else in the reactor vessel. I have a lot of doubts that the leakage is from water inside the vessel or drywell. For one, all of the injection lines in the vessel are below the steam lines. Another important thing to realize, is that it is nearly impossible to flood up the containment high enough to flood the steam lines with a breached vessel.

Obviously if the MSIVs failed that's a big issue, but the MSIVs are responsible for interfacing the vessel with the steam lines leaving containment, not the outside environment. If an MSIV fails, that just means water/steam from the steam lines can make its way out of the reactor building, it doesn't mean a direct to environment leak (you would need another failure or a pipe break). If the leak is somehow from the reactor vessel itself, that would mean the piping in the MSIV room failed. And even if an MSIV failed in some way, it doesn't necessarily mean it has long term safety implications. Safety grade equipment like the MSIVs has a 30 days mission time, and a quantitative goal for the entire containment/isolation system as a whole to prevent leakage beyond a small percentage (between .25% and .5%) of drywell volume per day. One would have to prove a design defect that lead to the MSIVs not functioning during the event.

Anyways, the water temp is 20C (around 70F). The SFPs are probably in this range, so that is one possible leak location, although I'm not sure how it would get down into the steam tunnel. The reactor building closed cooling system may be a potential leak source. This provides cooling for the SFP heat exchangers and other heat carrying components in the reactor building, although this system may have been destroyed or not in use. We simply don't have enough information to draw good conclusions.

 

[Sotan]

Thank you all who replied to my earlier post.

Here's an excerpt from a regular report regarding the state of the plant - in my (loose) translation.
http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140121_04-j.pdf

・H26/１/21 H25/12/9 から２号機原子炉建屋内において、３Ｄレーザスキャンを実施しているが、ト
ーラス室における計測作業終了後、遠隔操作装置のクローラに不具合が確認されたため、
安全を考慮し、装置をトーラス室の階段の手前に置いている。1/22 に装置を回収し、原
因を調査する予定。

21 Jan 2014
Since 9 December 2013 they have been doing a 3D laser scan of the Reactor 2 building.
After finishing the scan of the torus room, a problem was discovered with the "chain tracks" of the robot used to perform this operation. The robot has been parked for safety in front of the stairs leading to the torus room and is to be recovered on 22 Jan for inspection and determination of the cause of the fault.

--------
Also from this Japanese report:
http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140121_05-j.pdf
Looks like they have been measuring the water level in the suppression chamber of Reactor 2.
I do not know the significance of this subject, but if they measured and report it, it must be important (perhaps some people could comment).
Results of measurements on 14, 15 and 16th of January suggest that the water level in the S/C changes to reflect the variations of the water level in the torus room. They think these measurements may prove useful for the planned works aimed to make the PCV water tight. (I hope I translated correctly the last phrase...)

----
Also in this Japanese report:
http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140120_06-j.pdf
You can see some images from the trench in which sea water pipes are installed at Reactor 2.
Again, I do not really understand the significance of these inspections and measurements, perhaps somebody could comment. (Was it done just to check the level of accumulated water?)

 

[zapperzero]

I'd surmise this is all done to get an idea of the various water flows. Interesting about the laser scan. I wonder what they will use it for? Maybe they will plan future robot expeditions using this 3d model of the building. There are iirc LIDAR scans of the exteriors of the plants, too, but the data has not been released, just some ugly and useless snapshots...

 

[Sotan]

Regarding the video inspection of the trenches: I just saw a piece of news on NHK which explained that the video inspection of the trenches has shown that there is no significant damage or obstacles in those areas as a result of the earthquake/tsunami. Therefore, starting at the beginning of March they plan to begin treating the highly radioactive water that has been sitting there since the accident, in the hope that this will drastically reduce the radioactive contamination of the sea (the trenches being thought to be one of the main sources of contamination).

 

[Sotan]

A brief note regarding this report:
http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140122_05-j.pdf
(Japanese only)

It is about the flow of water discovered at first floor of Reactor 3 building, in the vicinity of MSIV.

- Water flow was discovered on Jan 18 by reviewing video from robot. Water coming from the direction of the door of MSIV room was flowing into a floor funnel (drain).
- On Jan 20 they removed some garbage from that funnel.
- On Jan 21 they directed the robot to take images of the same area and discovered that the flow of water diminished considerably.
- The images and drawing attached show the position of the funnel (dotted white circle in photo) and the direction of the water flow (blue dotted arrow in the drawing).
- Analysis of the water indicated relatively high concentrations of Cesium, close to values recorded for the contaminated water accumulated in the basement. Temperature (about 20 degrees Celsius) was close to the that of water in the containment vessel. The water flow was approximated at about 1.5 cubic meters per hour.
Objectives for further investigation:
- Investigation of the interior of the MSIV room, by means which are now under consideration. Possibly try to insert a camera in that room.

The next pages of the report show results of analysis of radioactive content of various samples of water (page 5), results of temperature measurements in various places of Reactor 3 building (page 6), considerations of the areas where pipes exit from the PCV (through the MSIV) and which are suspected to be possible places for the location of the leak, seeing that they are located under the calculated level of water in the PCV (page 7 and 8). Page 9 shows a detail drawing of the “bellows type expansion” penetrations where pipes come out of the PCV.

 

[SteveElbows]

plume's laid down to the northwest if I'm reading the map right
would be interesting to correlate with weather at the time of the accident, iirc most of the time the wind was blowing east or south east, out to sea? but then my memory is very bad.

Well as radiation survey maps from previous years showed the same pattern, this stuff has been discussed before.

I don't have the most detailed studies to hand, but here is a rough description of relevant info:

Wind direction was out to sea at several stages, including the explosion of reactor 3 building. Thats probably what you are remembering. It often came up when issues such as whether reactor 2 was really responsible for most environmental contamination came up. For example there were people who attached much significance to the reactor 3 explosion, and it was not possible to prove to their satisfaction that it was a minor event in terms of radioactive releases to the environment compared to reactor 2, because the wind direction at the time prevented a strong record of the event showing up in land contamination readings.

The bulk of land contamination is usually put down to events of March 15th 2011, due to a combination of the vigorous emissions seen leaving the reactor 2 building, and the wind & other weather factors. Initially the wind was blowing approximately south, but during the period it gradually moved further clockwise, so that at some later point there was a plume to the north-west. Some of this hit a band of rain in the area (or according to some reports, snow) which greatly enhanced land contamination to the north-west.

There could have been some land contamination to the north from the reactor 1 vent and/or explosion, but again this tended to be overshadowed by the much higher levels of contamination on the 15th.

The rather poor state of narratives and accurate emission details for the period later in the month mean that further possible significant emissions, including from reactor 3, are not well described. There has been some attention to emissions around the 20th-21st March, because the wind was again blowing south and causing some radiation to show up in locations well south of Fukushima, such as Tokyo. Again I believe rain may have been involved in some places, and this episode was also of interest due to recurring 'white or black' smoke events at reactor 3, and indeed the general problems they had achieving anything resembling stable temperatures in March, well after the first few days of meltdowns.

The failure of company & government officials to swiftly admit and discuss containment failures at the reactors hampered the ability to generate a useful mainstream narrative that could be combined with weather and radioactive contamination data at various points to build a detailed picture in terms of the radioactive ground contamination and what reactor events it related to. Even when we could see for ourselves in photos and video steam/smoke escaping from reactor 3, and when much later there were photos published showing the vigorous nature of the emissions from reactor 2 on the morning of March 15th, attention still tended to linger on explosions, fuel pools and venting. So the weather on March 15th didn't get as much attention as it deserved, although it is featured in several reports which include rain radar images from pertinent moments. If I find them I will post a link.

edit - I'm not sure these are all the weather-related reports I've seen in the past but between them they describe fairly well the weather-contamination events and attempts at analysis.

http://www.nsr.go.jp/archive/nisa/shingikai/700/14/240723/AM-3-2.pdf Pages 14-16.

http://www.vic.jp/fukushima/global/global-e.html

http://www.irsn.fr/FR/Larecherche/p...Abstract_intervention_Anne-Mathieu_TS12a1.pdf

 

[Sotan]

According to the regular report on the state of the plant of 24 Jan
http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140124_07-j.pdf (in Japanese)
they will start inspecting the operating floor of Unit 2, aiming to progress with the plan for fuel extraction.

The operation is further detailed in this report:
http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140124_08-j.pdf (in Japanese)
where, among others, you can see two small pics with the present state of the operating floor.

They have 3 variants of plan to proceed towards extraction: one is to use the present building and installations as they are, after repair; the other two involve different amounts of work and construction of a container on top of the present operation floor, or even a full container of the present building. They are trying to decide which one to pick.

The report from the second link has a lot more content.

The inspection of the operating floor might be made by two methods: lowering lighting fixtures, gamma and normal light camera, radiation measuring devices from the top of the building; and entering a rather large robot (which later might even be used to take a core sample) through a "sliding door" (existing? or cut in the blow-out panels) on the lateral side of the building. They make some calculations regarding the amount of additional radiation and radioactive substances that might escape through the various holes that must be cut for these purposes. They conclude that this amount of radiation/radioactive substances does not pose a significant additional risk.

 

[Sotan]

To my surprise, "core sample" above apparently means a sample of the concrete in walls and floors.

 

[Sotan]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140212_05-j.pdf
(in Japanese)

Two cracks (I'd say rather large: 8m, 12m long) have been found in the concrete foundation of storing tanks in H4 and H4-East areas.

They have been spotted initially in December last year, when they were like very thin lines in the concrete. They added some epoxy resin to try and stop any water infiltration that might occur through them.

As they were cleaning the concrete surface for a new operation (adding a layer of urethane-based paint to improve water insulation), the cracks became very much apparent again. (You can see them in photos in the link above.)

They don't seem too worried, they will asses the situation thoroughly but they think the main thing to do is to hurry up the application of that urethane-based paint throughout the area.

----------------
http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140212_04-j.pdf

In July 2013 some samples displaying high radioactivity were gathered from Naraha-machi, Futaba-gun, Fukushima-prefecture. Tepco has received those samples (4 of them) and had them analyzed by JAEA and are reporting those results.

While I cannot say much about the numbers given in those tables, I notice from page 6 that the radiation levels (Cs-137, Co-60) measured from these samples are clearly higher than those recorded for debris picked from around Reactor 3 or from other places outside of the plant.

The conclusions on the last page:
- most of the radiation is attributed to Cs-134 and Cs-137;
- due to the high level of radioactivity and to the detection of Cobalt (absent normally in samples from outside the plant), the conclusions is that these samples probably originate from the plant;
- the first two samples appear to be poliethylene, the third one a polymer of "poliolefin" and the fourth one a piece of wood (sorry if I misspelled some of these materials);
- it was not possible to determine the route (by sea? by land?) by which these samples landed in the places where they were found.

 

[zapperzero]

Sounds like bits of roofing.

 

[Sotan]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140214_04-j.pdf
(in Japanese)

It's a report on the results of checks performed in the building of Reactor 3, after removing the debris.
Many interesting photos.
One important finding is that the massive concrete shield plug that covers the PCV (made of 3 slabs of concrete stacked one atop the other, each 600 mm thick) appears to have a big "dent", the surface is pushed in, about 300 mm. Most likely caused by the fall of the ceiling crane (it had a big heavy trolley right in that area). They don't seem much alarmed by this, though, as it probably didn't cause important damage to the PCV and the situation seems to be stable now.

 

[Hiddencamper]

http://www.tepco.co.jp/nu/fukushima-np/handouts/2014/images/handouts_140214_04-j.pdf
(in Japanese)

It's a report on the results of checks performed in the building of Reactor 3, after removing the debris.
Many interesting photos.
One important finding is that the massive concrete shield plug that covers the PCV (made of 3 slabs of concrete stacked one atop the other, each 600 mm thick) appears to have a big "dent", the surface is pushed in, about 300 mm. Most likely caused by the fall of the ceiling crane (it had a big heavy trolley right in that area). They don't seem much alarmed by this, though, as it probably didn't cause important damage to the PCV and the situation seems to be stable now.

Inside the reactor cavity, there is a reactor vessel head. On top of that is the PCV head. And on top of that is the shield plugs. I think the shield plugs did part of their job of protecting the PCV head, which is likely the most vulnerable point of the PCV.

 

[LabratSR]

An interesting twist to the filtered vent debate.

http://ex-skf.blogspot.com/2014/02/tepco-tells-governor-of-niigata-that.html

 

[Sean Thornock]

Meltdown: What Really Happened at Fukushima?

The authors have spoken to several workers at the plant who recite the same story: Serious damage to piping and at least one of the reactors before the tsunami hit. All have requested anonymity because they are still working at the plant or are connected with TEPCO. One worker, a maintenance engineer in his late twenties who was at the Fukushima complex on March 11, recalls hissing and leaking pipes. “I personally saw pipes that came apart and I assume that there were many more that had been broken throughout the plant. There’s no doubt that the earthquake did a lot of damage inside the plant," he said. "There were definitely leaking pipes, but we don’t know which pipes – that has to be investigated. I also saw that part of the wall of the turbine building for Unit 1 had come away. That crack might have affected the reactor.”

A second worker, a technician in his late 30s, who was also on site at the time of the earthquake, narrated what happened. “It felt like the earthquake hit in two waves, the first impact was so intense you could see the building shaking, the pipes buckling, and within minutes, I saw pipes bursting. Some fell off the wall. Others snapped. I was pretty sure that some of the oxygen tanks stored on site had exploded but I didn’t see for myself. Someone yelled that we all needed to evacuate and I was good with that. But I was severely alarmed because as I was leaving I was told and I could see that several pipes had cracked open, including what I believe were cold water supply pipes. That would mean that coolant couldn’t get to the reactor core. If you can’t sufficiently get the coolant to the core, it melts down. You don’t have to have to be a nuclear scientist to figure that out.”

Before the dawn on March 12, the water levels at the reactor began to plummet and the radiation began rising. Meltdown was taking place. The TEPCO Press release issued on March 12 just past 4am stated, “the pressure within the containment vessel is high but stable.” There was a note buried in the release that many people missed. “The emergency water circulation system was cooling the steam within the core; it has ceased to function.”

Oddly enough, while TEPCO later insisted that the cause of the meltdown was the tsunami knocking out emergency power systems, at the 7:47 p.m. TEPCO press conference the same day, the spokesman in response to questions from the press about the cooling systems stated that the emergency water circulation equipment and reactor core isolation time cooling systems would work even without electricity.

http://www.thewire.com/global/2011/07/meltdown-what-really-happened-fukushima/39541/

 

[Rive]

stuff

That article is from mid-2011.
This part of the events were discussed loooooong time ago, in the previous section of this topic.

 

[Sean Thornock]

The Geology of Fukushima

At a time when everyone is wondering where the coriums of the crippled Fukushima Daiichi nuclear plant may be, it is interesting to know the nature of the terrain where they could possibly be hiding. Although all documents used to write this article are readily available, most are in Japanese and this explains that to date knowledge of the geology of Fukushima is fragmented. Based on the geological survey that was conducted prior to building the plant, as well as on results of seismic testing and recent research related to drilling, this article will attempt to give an updated picture of the nature of the substratum of the nuclear plant, which may help to predict possible developments in the currently unfolding disaster.

http://www.fukushima-blog.com/article-the-geology-of-fukushima-88575278.html

 

[Sean Thornock]

I'm wondering also how they can clear the 50 tons of steel, refueling mast and cement out of the #3 fuel pool. Could these fuel racks still be intact ? I wonder how this can be done.

http://www.iaea.org/newscenter/focus/fukushima/statusreport270412.pdf

 

[LabratSR]

Meltdown: What Really Happened at Fukushima?
http://www.thewire.com/global/2011/07/meltdown-what-really-happened-fukushima/39541/

You may be interested to read the conclusion in this report. Look under Earthquake Damge, page 17

http://warp.da.ndl.go.jp/info:ndljp...ent/uploads/2012/09/NAIIC_report_lo_res10.pdf


The full report may be found here.

http://warp.da.ndl.go.jp/info:ndljp/pid/3856371/naiic.go.jp/en/

 

[nikkkom]

I'm wondering also how they can clear the 50 tons of steel, refueling mast and cement out of the #3 fuel pool. Could these fuel racks still be intact ? I wonder how this can be done.

They will use the novel technique of "pulling debris piece by piece out of the water". What did you expect?

 

[Sean Thornock]

Feb. 17, 2014: Co-60 - 750 Bq/L ( Wells No. 1-6 )

http://www.tepco.co.jp/nu/fukushima-np/f1/smp/2014/images/2tb-east_14021801-j.pdf

 

[Rive]

I heard that can't even get robots near this area.

I'm afraid it's simply not true. They've sent robots even much worse areas and doing their jobs as scheduled by remotes, robots and: personally too.

The top of the U3 was cleaned up with remote controlled machinery. That cleanup was performed unexpectedly well. The pool of U3 will be emptied by the same machinery.

 

[Sean Thornock]

I'm afraid it's simply not true. They've sent robots even much worse areas and doing their jobs as scheduled by remotes, robots and: personally too.

The top of the U3 was cleaned up with remote controlled machinery. That cleanup was performed unexpectedly well. The pool of U3 will be emptied by the same machinery.

I thought those fuel rods were delicate & the radiation levels at unit three are off the charts. Much different then taking wreckage from the roof. The #3 sfp is in very bad shape.

BWR/6 Fuel Assemblies & Control Rod Module ( these can't handle 50 tons without sever damage )

http://www.nucleartourist.com/images/bwrfuel1.jpg


What do you think about the fault / sandstone below the corium kinda makes it hard to stop the 600 tons of water flowing toward the ocean every day, no ?

 

[Sean Thornock]

And what about Cobalt-60 ? Or last weeks Cesium-137 54,000 Bq / Liter / Or the new revised Strontium-90 5 million Bq / Liter per recent well reading.

After 3 years the readings are quickening not slowing.

 

[jim hardy]

Well, you might peruse that reference Labrat posted, and study the old thread to see where we've been.

Questions are welcome but crazy assertions and articles from the tabloid press are, well, just not helpful.

Judge your sources. Isaac Asimov wrote at length about his "Built In Doubter" which makes him question all assertions that aren't backed up by supporting facts. And always cross check.

For example, that claim about fuel elements and 50 tons:
How then can fuel pools be stacked two layers deep?
What about the steel from which the fuel racks are made?

I think a fuel bundle might well support 50 tons in compression, especially if the racks prevent buckling.

So ask what you don't know, don't assert it as if it were fact - that way you'll be perceived as not so confrontational and annoying.



old jim

 

[SteveElbows]

What you may need to keep in mind is that this is a physics forum. As such there is a low tolerance towards various forms of discussion about Fukushima that veer to far away from the scientific method.

As I understand it there was more slack given to the main Fukushima thread than would often be the case, in terms of moderation etc, because at the time it was a fast-evolving situation with many unknowns and much room to speculate without unscientifically ignoring well-established facts. Over time more has been learnt, and certain things ruled out as possibilities, but since it will be very many years till certain important details may be discovered, and some may remain permanently out of reach, I expect some slack is still granted. Especially as poor communication and obfuscation from various official sources at various times, combined with bouts of ineptitude, has eroded faith in certain aspects of the official picture.

But with that said, people who consistently struggled to accept any evidence that contradicted their worst-case assumptions about Fukushima and the things that could yet go wrong on site, eventually ran into problems here. Not too many so far if memory serves me correctly, but it would be a shame to have any more, especially now that some years have passed with rarely anything more dramatic than water leaks. What you might find here is that many people already rank Fukushima as a very major series of nuclear disasters, and consider the clean-up operation, in so much as it will prove to be possible, is fraught with complications and not without risks. And that they don't need to inject a fresh sense of immediacy into the view of Fukushima in 2014 in order to appreciate the scale of the problems and the issues.

It is certainly true that the removal of spent fuel from the reactor 3 pool has a number of complications compared to the operation at reactor 4. Far more debris had & has still to be removed, and the radiation levels in the vicinity do require remote operations at this stage which makes the operation far more clunky. Plenty of things could impede progress at some point, but the progress that has been achieved to date, however slowly, is still going to be recognised here.

 

[Hiddencamper]

I'm pretty sure spent fuel pools need to be capable of surviving cask and other load drop accidents as part of their design criteria. So this really precludes major fuel or rack damage even with load drops in the pools. If major fuel damage had occurred it would be very easy to detect though a water sample of the pool. I wouldn't be surprised if they busted some bundles, but I'm not expecting anything that would be of major interest. I'll see if I can find anything. My plant uses similar spent fuel racks to the ones at Fukushima.

As for timelines, IAEA released a report that said Fukushima would be around 30-40 years. It was a final decommissioning timeline put together with TEPCO and the Japanese regulator with a lot of international help. I have the actual report on my thumb drive at work, I'll try to remember to post the link to it.

 

[Hiddencamper]

And what about Cobalt-60 ? Or last weeks Cesium-137 54,000 Bq / Liter / Or the new revised Strontium-90 5 million Bq / Liter per recent well reading.

After 3 years the readings are quickening not slowing.

Do not take the fact that higher numbers are being detected as an increased problem. A large amount of radioactive material has relocated from where it is supposed to be, and it is going to be moving slowly out from the areas around the plant. That doesn't mean it's getting worse, that just means stuff that got relocated by the accident is now starting to become detectable (it's moving), and the fact that it is moving isn't unexpected. What we didnt know is how quickly it would be moving.

The focus for everyone, shouldn't be on the "omg they found a high measurement" and more on how they are progressing with their efforts to stop the leaks, which will then reduce those measurements.

The reactors are shut down. No new radioactive material is being created. A lot of radioactive material is being relocated, and most of it is going into filters, but some of it is getting out, and that's going to happen until they reach a point where they no longer need to cool/shield the core material on site. Everyone on this site has known this for quite a while now, so no need to try and stir the pot.

If you don't understand radiation or nuclear technology, there are many people here who are more than willing to answer questions, but please be respectful of the fact that the people here have been following the accident since it happened, reading all sorts of official and unofficial reports, and have a very good understanding of it. I personally was involved with some of the earlier US industry response to Fukushima, and there are others who have a lot of nuclear industry knowledge here from a theoretical and/or practical perspective. We know pretty well what the magnitude is and what its going to take to clean it up, so trying to tell us its "zomg so bad" is just going to anger some people, because it detracts from any form of meaningful discussion about the event findings and cleanup progress.

tl;dr, don't detract from meaningful discussion and we will all be happy to discuss with you, teach what we know, or point you in the direction of data/documents. Otherwise please consider finding another site to post on. Thanks!

 

[Hiddencamper]

I thought those fuel rods were delicate & the radiation levels at unit three are off the charts. Much different then taking wreckage from the roof. The #3 sfp is in very bad shape.

BWR/6 Fuel Assemblies & Control Rod Module ( these can't handle 50 tons without sever damage )

http://www.nucleartourist.com/images/bwrfuel1.jpg


What do you think about the fault / sandstone below the corium kinda makes it hard to stop the 600 tons of water flowing toward the ocean every day, no ?

Before you make a claim that a BWR/6 fuel bundle can't support 50 tons, ask the question of what they can support. I work at a BWR and if I get a chance I can probably look up the structural load capacity of the fuel racks. I don't work in the same building as our engineering library anymore so I don't get a chance to pull stuff as often, but I'll see what I can do.

What I can tell you right now, is that the spent fuel racks are required to handle load drops in the pool as part of their seismic/structural safety requirements. The racks are Seismic category I and safety class 2, so I'm doubtful a large load would affect them given the large surface area to work with. But at the same time, WE HAVE A CALCULATION FOR THAT. Those calculations exist. So before you make an assertion, ask someone what they know.

 

[Hiddencamper]

Meltdown: What Really Happened at Fukushima?

The authors have spoken to several workers at the plant who recite the same story: Serious damage to piping and at least one of the reactors before the tsunami hit. All have requested anonymity because they are still working at the plant or are connected with TEPCO. One worker, a maintenance engineer in his late twenties who was at the Fukushima complex on March 11, recalls hissing and leaking pipes. “I personally saw pipes that came apart and I assume that there were many more that had been broken throughout the plant. There’s no doubt that the earthquake did a lot of damage inside the plant," he said. "There were definitely leaking pipes, but we don’t know which pipes – that has to be investigated. I also saw that part of the wall of the turbine building for Unit 1 had come away. That crack might have affected the reactor.”

A second worker, a technician in his late 30s, who was also on site at the time of the earthquake, narrated what happened. “It felt like the earthquake hit in two waves, the first impact was so intense you could see the building shaking, the pipes buckling, and within minutes, I saw pipes bursting. Some fell off the wall. Others snapped. I was pretty sure that some of the oxygen tanks stored on site had exploded but I didn’t see for myself. Someone yelled that we all needed to evacuate and I was good with that. But I was severely alarmed because as I was leaving I was told and I could see that several pipes had cracked open, including what I believe were cold water supply pipes. That would mean that coolant couldn’t get to the reactor core. If you can’t sufficiently get the coolant to the core, it melts down. You don’t have to have to be a nuclear scientist to figure that out.”

Before the dawn on March 12, the water levels at the reactor began to plummet and the radiation began rising. Meltdown was taking place. The TEPCO Press release issued on March 12 just past 4am stated, “the pressure within the containment vessel is high but stable.” There was a note buried in the release that many people missed. “The emergency water circulation system was cooling the steam within the core; it has ceased to function.”

Oddly enough, while TEPCO later insisted that the cause of the meltdown was the tsunami knocking out emergency power systems, at the 7:47 p.m. TEPCO press conference the same day, the spokesman in response to questions from the press about the cooling systems stated that the emergency water circulation equipment and reactor core isolation time cooling systems would work even without electricity.

http://www.thewire.com/global/2011/07/meltdown-what-really-happened-fukushima/39541/

Sorry I'm chain posting responses but there is too much bull this guy is posting.

With regards to "busted pipes",

Check out this link

http://www.tepco.co.jp/en/press/corp-com/release/betu13_e/images/131213e0101.pdf

Page 7

"Drawing surveys, eyewitness accounts, plant data, and other information have made it clear that the water flowing into the 4th floor of the nuclear reactor building unit 1 flowed in via a duct in the spent fuel pool".

This makes sense physically. The water level in the pools is maintained with scuppers and skimmers. Directly above these is a set of ducts used to draw vacuum above the pool to limit offgas of radioactive isotopes. During the earthquake a significant amount of water would have sloshed into this ductwork. The ductwork has sections designed for water to break/pass through, because it was envisioned that human error could overfill the pools and they didnt want water to inundate the entire reactor building HVAC system.

To add to this, any busted pipes in the reactor building that had safety significance would have either been in the ECCS cubicles or inside the containment. The containment is inerted with nitrogen, so no humans were in there. The ECCS cubicles were likely off limits due to flood waters preventing entry through the water tight doors.

There are reports of potential damage to feedwater. Feedwater is NOT a safety system. With the power grid offline, feedwater was incapable of functioning in the first place (Feedwater is not powered by emergency generators in BWRs). So the reports that broken pipes meant water couldn't get into the core combined with the physical layout of the plant of cooling pipes meant that the only pipes which they COULD have been talking about were the non-safety, non-functioning feedwater system.

If you have any questions about the ECCS network of BWR series plants or the design criteria, let me know and I will answer them. If you answer with some bs web link, assertion, or whatever, expect to get BS back in return.