Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Bioengineer01]

English version of the report is here:

http://www.kantei.go.jp/foreign/kan/topics/201106/iaea_houkokusho_e.html"

...no attachments!

For Unit 2 they say"
"Since March 20 the RPV temperature has been measured when the amount of water
injected increased. During most of the period after the start of measurements, the
temperature was stable at around 100°C, and during most of the period after March 29
when the amount of water injected was decreased, the RPV temperature was around
150°C. Accordingly, at this point, it is presumed that a significant amount of the fuel
remained in the RPV. However, it cannot be denied that the bottom of the RPV was
damaged and part of the fuel dropped and accumulated on the D/W floor (lower
pedestal).
Judging from the fact that the temperature in some part of the RPV is higher than the
saturated temperature in relation to the RPV pressure, it is presumed that part of the fuel
was not submerged and cooled by steam."
http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/chapter_iv-2.pdf

 

[MadderDoc]

Those releases appear to me to be coming from the containment structure, although; I will agree that there is a possibility they are coming from north of the containment.

But there is nothing that i know of to the north of the containment structure that could be a source of steam release, except steam from a leak or broken pipe lower in the containment structure which finds its way out there.

But that still leaves the two sources of steam as being the containment structure and the SFP.

What do you think?

I think that the photographic evidence cannot support that the south distinct source should be the SFP per se, but rather strongly suggests that the south source is or is close to the SFP/reactor transfer chute. The strongest evidence in this respect is the photos from March the 16th, which display a SFP which has apparently little or no water in it and is not steaming at all, Nonetheless there's a well developed south steam fan, which appears to originate from the same area as it does in all other photos of unit 3 that include a visible south steam fan.

 

[NUCENG]

Did someone disprove the steam-explosion hypothesis while I wasn't looking?

As I understood that hypothesis it depended on stratification and no natural circulation until the pont where the whole pool was a whisker away from flashing to steam. Aftershocks had to be ignored. And this had to exist in a pool with debris and fuel assemblies and metal racks and walls and control rods that would serve as nucleation sites for boiling onset that would have initiated convection flows and mixing even before the pool reached bulk boiling temperaute. I calculated that the unit 4 pool could have reached bulk boiling conditions a little more than a day after it lost cooling. That was well before the building was severely damaged. So my question is, what could cause a steam explosion in a pool that was already boiling? If I am wrong to think that is low credibility, my apologies for ommiting that as a possibility.

 

[Bioengineer01]

For Unit 1 they say:
"As a result of recovering and correcting the standard water
level for the water level gauge in the reactor on May 11, it was confirmed that the water
level was lower than the fuel. Therefore, at the present moment it is estimated that the
fuel has melted and an considerable amount of it is lying at the bottom of the RPV.
However, the bottom of the RPV is damaged, and it is thought at the present stage it is
possible that some of the fuel has fallen through and accumulated on the D/W floor
(lower pedestal).
The temperature of part of the RPV (the feed water nozzles, etc.) is higher than the
saturation temperature for the PRV pressure, so at the present stage it is estimated that
part of the fuel is not submerged in water, but is being cooled by steam."
http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/chapter_iv-2.pdf

 

[Bioengineer01]

For Unit 3 they say:
"Some RPV temperatures exceeded the measurable range (higher than 400C) due to the lower injection flow rate caused by the increase of RPV pressure on March 20, but the temperature dropped through the securing of injection flow rate on March 24 and stayed around 100C. Accordingly a considerable amount of reactor fuel may remain within the RPV. It cannot be denied at this moment that the bottom of the RPV might get damaged, through which part of reactor fuel might drop to the D/W floor (lower pedestal) and might accumulate there.
The temperature tends to rise in general from the beginning of May. Considering that it partially exceeds 200C and is higher than the saturation temperature for the RPV pressure, part of reactor fuel may still remain unsubmerged and be cooled by vapor."
http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/chapter_iv-3.pdf

 

[Quim]

If I am wrong to think that is low credibility, my apologies for ommiting that as a possibility.

You are not alone in thinking that hypothesis is low probability.
IMO "low probability" is a generous assessment for that theory.

 

[Bioengineer01]

It was all discussed here ad infinitum. That's not to say further information wouldn't be welcome. A new batch of photos would re-ignite the conversation, but every image and video publicly available has been dissected at length.

On another note, Foust's enlarged pictures don't really reveal anything new. She posts some interesting information once in a while. Can't say much about her analyses, though.

Hey thanks! I am reading through all posts, but it is a daunting task!

 

[NUCENG]

i'm in information overload. would you put up a pointer to them, or a search term to look for?

g'nite all, over & out till morning

Search with advanced search tool using: User "NUCENG", Keyword "recriticality". My position is that recriticality is possible, however, not yet proven.

 

[NUCENG]

I'm no graphics expert but when I zoom in on the SBGT pipe in this picture, it is as clear as a bell that the pipe was broken while #4 was still intact. When I compare it to other pictures I have of that pipe break (after #4 blew but before the pipe was bent downward) the pipe is in an identical condition as this satellite picture.

I will add that the helicopter crew which went up to dump water in the SFPs reported that the SFP at #4 still had water in it - so they tried to dump their load on #3 (I'll find that for you if you are missing that information.)

The radiolysis theory would seem to be proven by this satellite picture showing the broken pipe before #4 blew.

What do you think?

How intelligent, astute, and even, dare I say, Brilliant of you to agree with me! (For those of you who lack a sense of humor, "That is a joke, son!"

I asked the question, because I don't know. I have tried to warn others about trying to read too much from photographs and seeing what you want to see. I don't have any software tools to do anything more than zoom, and that just gives an incoherent jumble of pixels. I don't have any background in photoshop or other tools that may show more, so I'm asking the forum what they can tell from this photo.

 

[StrangeBeauty]

It would very much depend on the history of the fuel rod, if it is brand new it is not very radioactive, but it becomes increasingly more radioactive during use, reaching a peak when it is time for it to be taken out of service and placed in the sfp. Once there, its radioactivity will again slowly wane over many years.

However, just to get some idea of the magnitude of activity we could be looking at, according to the NRC, the surface radioactivity of a spent fuel rod still exceeds 100 Sv/h after having been stored ten years in the sfp.

Thank you!

Now for some small measure of consensus, it would be great if one (or more) other experts replied to this with an "I agree. 100 Sv/h is a reasonable estimate." or...not! :)

 

[jim hardy]

seeing as how the used fuel elements make water glow blue around them, i think 100Sv is a conservative number.

 

[MiceAndMen]

For Unit 1 they say:
"As a result of recovering and correcting the standard water ...

Also interesting on page IV-40:

TEPCO worked to vent the PCV in order to lower its pressure. However, since radiation
inside the reactor building was already at the high radiation environment level, the work
proceeded with difficulty.

That implies radiation leakage well before the explosion at Unit 1, doesn't it?

 

[Bioengineer01]

You are not alone in thinking that hypothesis is low probability.
IMO "low probability" is a generous assessment for that theory.

completely agree and I used to run a lab in biophysics with that experiment... :) A few decades ago... :)

 

[clancy688]

Also interesting on page IV-40:

That implies radiation leakage well before the explosion at Unit 1, doesn't it?

Wasn't it confirmed that there was already high level radiation inside Unit 1 at March 11th/12th midnight?

TEPCO reported that workers who entered the Unit 1 building in the night after the Tsunami encountered 300 mS/h radiation in the secondary containment, which at least implicates that the earthquake already damaged water pipes.I know that one member discovered this particular statement and concluded, with news reports from the beginning of the accident which cited TEPCO telling that the Containment was NOT breached, that TEPCO LIED. But I don't know who it wrote, I don't know when and I don't know where. That's the problem if there are 10.000 posts...

 

[Bioengineer01]

Also interesting on page IV-40:

That implies radiation leakage well before the explosion at Unit 1, doesn't it?

Excellent catch! This would support other data suggesting containment damage with the quake...

 

[clancy688]

I know that one member discovered this particular statement and concluded, with news reports from the beginning of the accident which cited TEPCO telling that the Containment was NOT breached, that TEPCO LIED. But I don't know who it wrote, I don't know when and I don't know where. That's the problem if there are 10.000 posts...

Found it...

https://www.physicsforums.com/showpost.php?p=3320390&postcount=172

 

[robinson]

It's funny, I was just looking at old news reports from the March 14-17th period, noting the vast amounts of deception and blatant lies fed to the world. I've often thought that you would have to be disconnected from reality to look at the video of the explosions, and then believe the nonsense the media was feeding 24/7

The actions of the US at the time, where they moved their entire rescue operation to the other side of Japan, avoiding the ocean down wind from the fires and explosions, told the real tale of the radiation escaping out to sea.

Of course nobody did any measurements at all of what was blowing down wind over the ocean, so it's about impossible to tell what the real amounts are.

 

[tsutsuji]

Japanese Government Admits "Melt-Through" in Reactors 1, 2 and 3

"Yomiuri Shinbun (original in Japanese; 6/7/2011) reports that the Japanese government will now admit in the report to IAEA that the "melt-through" may have taken place in the Reactors 1, 2 and 3 at Fukushima I Nuke Plant."

Thanks again to http://ex-skf.blogspot.com/2011/06/fukushima-i-nuke-accident-japanese.html" for the story

So, are the reactor cores in the Drywell, the Torus or the Basement for all 3 reactors?

Perhaps it is a new development that the Japanese government admits this possibility in a formal written manner, but this is nothing new as far as Tepco is concerned. At the beginning of last month, when the water level gauge was changed, Tepco had to admit that a large part of unit 1's core had melted and Jun'ichi Matsumoto, the Deputy General Manager of the nuclear power plant siting division was quoted on May 12th as saying : « I do not believe that the nuclear fuel has leaked outside of the reactor pressure vessel, but this is a possibility that cannot be ruled out » : http://www.asahi.com/national/update/0512/TKY201105120174.html

 

[MiceAndMen]

Report of Japanese Government
to the IAEA Ministerial Conference on Nuclear Safety
June 2011

Some of us have been referring to the PDF files on this page: http://www.kantei.go.jp/foreign/kan/topics/201106/iaea_houkokusho_e.html

For convenience, I have combined all of the PDFs on that page into one 385-page document that can be downloaded from here: http://min.us/mvoVGLP

The cover page + summary + all 13 chapters total about 11.5 MB. I added bookmarks for the major chapters (as well as a few for the individual reactors in part "IV-5. Situation of Each Unit etc. at Fukushima NPS"). Sometimes it's convenient to have everything in one file.

Suggest double-checking the page numbers of any references you may cite. For example, there are 2 pages numbered IV-37 and there may be other oddities in there as well.

 

[SteveElbows]

Wasn't it confirmed that there was already high level radiation inside Unit 1 at March 11th/12th midnight?

TEPCO reported that workers who entered the Unit 1 building in the night after the Tsunami encountered 300 mS/h radiation in the secondary containment, which at least implicates that the earthquake already damaged water pipes.

Exactly, in fact we had quite a discussion just a few days ago about the early radiation levels that occurred at various moments from late on march 11th through the morning of march 12th. Its not just data from inside the building around 11pm onwards but also various other data from both on and off site. Indeed the subject came up again the other day because detection of some nasty substances quite some distance from the plant on the morning of march 12th had just been revealed, having previously gone unpublished.

However I remain quite cautious about attributing these things to earthquake damage, because damage caused by loss of cooling happened quite quickly at reactor 1, and so I cannot be sure that earthquake made much of a difference. I believe some data they have may tend to suggest very little or no earthquake damage, in that both reactor and containment pressures achieved high levels at points well after the quake.

At the moment, as best I can tell it actually looks like reactor 3 where they are closest to entertaining the possibility of certain earthquake damage. This emerged a while ago but we only had a few press reports to go by as the detail was in Japanese. Well now we can read about it in the english documents linked to today, at least if I have found the right bit and am putting 2 & 2 together properly, as part of their analysis they mention that steam may have been escaping from the HPCI.

 

[robinson]

From a physics point of view, how long would it take for a meltdown in #1 if the earthquake damaged the reactor while it was going full bore? Hypothetically. If the quake damaged both the control rods, preventing them from being inserted, and broke a main pipe, leading to loss of water, how long would it take for a reactor of that design to fail in a catastrophic way?

 

[MiceAndMen]

Found it...

https://www.physicsforums.com/showpost.php?p=3320390&postcount=172

The search function on this site works rather well compared to some really bad ones I've encountered elsewhere. Sometimes you have to fiddle with your search terms but in general you can narrow down what you're looking for pretty quickly.

 

[SteveElbows]

Perhaps it is a new development that the Japanese government admits this possibility in a formal written manner, but this is nothing new as far as Tepco is concerned. At the beginning of last month, when the water level gauge was changed, Tepco had to admit that a large part of unit 1's core had melted and Jun'ichi Matsumoto, the Deputy General Manager of the nuclear power plant siting division was quoted on May 12th as saying : « I do not believe that the nuclear fuel has leaked outside of the reactor pressure vessel, but this is a possibility that cannot be ruled out » : http://www.asahi.com/national/update/0512/TKY201105120174.html

Yes, and it seems that government analysis of this possibility is pretty much the same as what people have been able come up with on this forum in the past.

Really it seems to come down to the idea that the various cores were all in a state that can damage the RPV for a fair amount of time, but also that measured RPV temperatures seem reasonably consistent with quite a bit of core still being in the RPV, and this is further supported by what happens to temperature readings when they increase or decrease flow of water into RPV.

I don't know how to improve on this, its still a pretty broad range of possibilities and I don't know what sort of data it may be possible to use to estimate what percentage of cores have left the RPV's. Am I right to think we may be waiting a very long time indeed to learn much more about this?

 

[niks1]

Wasn't it confirmed that there was already high level radiation inside Unit 1 at March 11th/12th midnight?

It is now officially admitted in the Gov't report on the same page (IV-40), a couple paragraphs above the previous quote:
" In addition, it has been confirmed that the radiation level
inside the turbine building increased at around 23:00 on March 11. "

 

[MikeIt]

RPV bottom head failure in a severe accident, according to US BWR beliefs, will occur in an ablating fashion. Uncooled core debris in contact with the inside of the RPV bottom head is likely to penetrate the head at an incore instrument penetration or CRDM housing penetration. When this occurs, it is believed that the hole will rapidly increase in size and a large portion of the molten debris will rapidly flow into the under vessel area. Some IPE-PRA studies claim this could occur as soon as an hour after core uncovery (in worst case scenarios). To avoid this situation, sufficient RPV injection is required to at least remove decay heat and thus keep the debris cooled enough to keep the RPV bottom head from failing. Of course, this assumes that all the RPV injection actually comes in contact with the debris. If this can't be done, the BWR strategy is to flood the primary containment to at least the elevation of the RPV bottom head and thereby contact the outer RPV with water and hopefully prevent or delay bottom head failure. If the RPV is breached by core debris, a combination of parameters should be observed such as RPV pressure decreasing while drywell pressure increases, drywell temp increasing, hydrogen detected in drywell, RPV water level below the bottom of active fuel, etc.

The frustrating thing about trying to figure out what happened at Fukushima is the lack of values for all these parameters. By our SAGs, we cannot positively say that RPV breach occurred. On the other hand we cannot say it hasn't. Even without this information, however it is very, very hard not to believe that much of the core debris has migrated onto the drywell floor simply for the extremely long time the cores have remained uncovered. The reliance on data from the couple RPV metal TCs is questionable. Sure, they track with changes in RPV injection flowrate but they only sense the outside surface of the RPV. For all we know these TCs are simply swinging in the breeze, especially the TC on the bottom head.

All the media talk about % fuel melt is meaningless. The questions that should be asked are: where did the fuel go? and, what can be done about it?

 

[SteveElbows]

Excellent, finally a document that sheds some significant light on timing of certain things.

This part of the report to IAEA deals with radioactive release into the environment:

http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/chapter_vi.pdf

Within just a page or two it starts to make sense of some of the increases in radiation detected in various places, and attributes events at specific reactors to them. Just a small taster below, check out the document for more.

After earthquake, the discharge of radioactive materials became evident early on the morning of March 12 when the air dose rate measured by a monitoring car near MP-6(monitoring post No. 6 in the site of Fukushima Dai-ichi NPS) increased. It can be estimated that there was a leakage of radioactive materials from the PCV and a discharge of such materials to the air, as a slight decrease in the PCV pressure was observed in Unit 1 after an abnormal rise at this point. According to an analytical result, that fuel meltdown had already started.

And at the other end of the time range covered by this stuff:

In addition, an increase in the air dose rate was observed near MP-6 at 23:00 on March 15 and at 12:00 on March 16. D/W pressure decreases were observed in Unit 3 and Unit 2 at respective times. It is estimated, therefore, that discharges occurred from Unit 3 and Unit 2 at these respective times.

Dont get me wrong, its not perfect, it doesn't cover everything in great detail but its way better than the complete lack of narrative we've previously had on this subject from official sources. Dont think there's anything for those fascinated by reactor 3 march 20th-23rd events though.

 

[Quim]

From a physics point of view, how long would it take for a meltdown in #1 if the earthquake damaged the reactor while it was going full bore? Hypothetically. If the quake damaged both the control rods, preventing them from being inserted, and broke a main pipe, leading to loss of water, how long would it take for a reactor of that design to fail in a catastrophic way?

Here is a good place to look for that kind of information:
http://www.ornl.gov/info/reports/1981/3445600211884.pdf The NRC had a study done to examine the probable failure sequence of a Mark I reactor.
Read that and you will know as much as anyone else here.

 

[clancy688]

Here is a good place to look for that kind of information:
http://www.ornl.gov/info/reports/1981/3445600211884.pdf

But that doesn't include a meltdown scenario with the core being still at full power, does it? He asked how long a meltdown would need if the control rods weren't inserted.
I'd say it would be a matter of minutes.
If coolant flow is cut off and control rods are not inserted, there's an accumulation of 1,4 Gigajoule thermal energy every second. I don't think the RPV will withstand such stress for more than a few minutes... but the thermal energy production will probably decrease as soon as the fuel melts.
Still I don't think that something like this happened. It was told that all reactors scrammed successfully.

 

[joewein]

Which once again points out how unfortunate it is that we are lacking a poster knowledgeable of the subject of geology.

It simply can't be true that the underground rock formations, water tables and streams at the Fukushima site are an unknown.

Somebody did the engineering for that dam.

Google Earth shows several lakes in hilly woodlands to the west of the power station, within 1-2 km. When TEPCO started switching from sea water cooling to fresh water cooling around march 22 they once listed the name of the dam on a diagram.

 

[joewein]

Can anyone explain me this graph at page 3, there is big jump in I-131 level between 5/27 and 5/31: http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110607e8.pdf

What's so interesting in that "Radioactivity Density of Sub-drain at Unit 3 (Bq/cm3)" graph is not so much the increase but the change in isotope ratios.

If we look at corresponding graphs for units 1 and 2 we see them start off with I-131 activity more than an order of a magnitude higher than cesium activity, but due to the 8 day half life, iodine drops off against longer lived Cs-134 (2 yr) and Cs-137 (30 yr) until it ends about an order of a magnitude *below* cesium.

We saw the same picture here in Tokyo, in published fallout numbers. From 3/20-23, I-131 levels in fallout in Tokyo were 1-2 orders of magnitutes higher than Cs-134 and Cs-137. About 4 weeks ago, the last detected iodine level was one order of a magnitude lower than the last detected cesium level.

That's how it should be. Adding water (rainwater or groundwater) might change absolute concentrations, but should dilute all isotopes equally.

What happens on the unit 3 chart between about 5/27 and 6/2 is iodine coming back up again to the level of cesium. That means some inflow of water in which iodine was at least as prevalent as cesium. About 10 half-lives after the SCRAM (i.e. a 3 order of magnitude drop in iodine) there shouldn't be any such water in Fukushima 1, unless limited re-criticality occurred at some point.