Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Jorge Stolfi]

These roof panels that are long and narrow and overlapping or interlocking when attached to the joists and ribbing that make up the roof ...

You seem to be referring to a layer of ribbed sheet metal (aluminum?) strips that sits over the steel framework. Those strips look like bits of white fettucini in the aerial photos (some 8 meters long and less than 1 meter wide), and are scattered all over the place. a few of them are still attached to the steel frame of #4.

Above that sheet metal layer there seems to be a dark grey layer of concrete and/or tarmac. In the best photos of #4 one can see some ribbing on it too, possibly a negative cast of the ribbing on the metal sheets. That layer presumably is reinforced with rebar or wire mesh, because in #4 a chunk some 15-20 meters across was thrown up in the air, then sliced though the steel beams next to the north wall, and is still hanging there in one piece.

Unit 4 looks like the blast (type??) came from the lower floors so didn't disengage the entire roof like a 'normal' hydrogen explosion would and even forced the parapet and its associated pivoting wall inward during the blast just pushing or sliding the roof section that remained inward until it folded the framework.

In #4 the entire concrete/tamac layer and almost all the metal sheets of the roof were blasted away. Part of the explosion indeed appears to have occurred in the 4th floor (below the service floor), but the only communications between those floors are the elevator shaft and four narrow stairwells at the corners. That is quite enough for the H2 to flow between floors, but hardly enough to transmit the explosion with such a force. Moreover the service floor slab of #4 does not appear to have been breached or even cracked (unlike that of #3).

I still cannot quite understand what hapened to the top of the north wall of #4. Its exterior paint seems to have been scraped down, and its top edge was pushed southwards (i.e. inwards) by several meters. I thought about the middle parts of the pillars being pushed out by the explosion and causing the tops to pivot inwards; but there does not seem to be anything in that location that could have served as the pivot, and I cannot see how the explosion could have pushed the middle of the pillars out without also pushing the top.

My best theory so far is that the slab of concrete/tarmac on the roof, after being lifted by the explosion, behaved like an airfoil and fell diagonally rather than straight down (as a playing card will do if you drop it at an angle). Part of it hit the roof steelwork near the north wall; after slicing thhrough the roof beams it crashed into the north pillars near the middle, breaking them at that height and pushing them out. The other part of the slab fell over the top edge of the wall; being tilted, it slid northwards and down over that edge, leaving the scrape marks and pushing the edge down but southwards. This chunk of the roof slab should now be lying among the rubble and ruined buildings at the feet of the north wall.

Since buildings #3 and #4 seem to be very similar, I would expect the roof of #3 to behave in a similar way. Namely the concrete/tarmac layer probably was lifted as one or more large "flakes", rather than pulverized. (However the explosion of #3 was more forceful and so the flakes may have been smaller than the mega-flake of #4.) Once in the air, those broad but thin flakes may fall obliquely rather than straightdown due to aerodynamic effects. Does this match the observations?

 

[|Fred]

Hey wait a minute. I thought a Chernobyl-like sarcophagus was not being contemplated. Any word on digging to bedrock to contain water pollution?
EDIT: Having perused the document, it seems they plan on patching up a torus which is cracked.

If they believe cooling it no longer achievable, I make sens to fast forward to options that were on hold because they interferes with cooling. Retrospectively it could look like 2 months wasted, and I'm sure the expert who believed the core melted to the bottom within the first few hours/days will make a point underlining that.

 

[GJBRKS]

They injecting 14,5m3/h to unit 3 now but temperatures going up not down...

I'm not sure about the dimensions of the RPV ,

but if I assume a height of 21 meter and diameter of 7 meter ,

(http://www.jnes-elearning.org/contents/bk/JNESeL-BK-004.pdf )

and a resulting total decay heat of 7 Mw ,

(http://mitnse.com/2011/03/16/what-is-decay-heat/ )

then an evenly spread of this heat energy around the surface would result in 15100 W/m^2

Which is equivalent to a blackbody temperature of 445 Celsius .

(http://www.wolframalpha.com/input/?i=15100+watts+per+square+meter&lk=1)

So without other cooling a homogenous conduction within such an RPV would not exceed

an outside surface temperature above 445 degrees celsius.

(http://www.tepco.co.jp/nu/fukushima-np/f1/images/032_1F3_05141200.pdf)

(EDITED for change of estimated decay heat for unit 1 to unit 3 )

In the case of unit 1 with a smaller estimated decay heat production of 4.5 Mw this would be 370 degrees Celsius

 

[zapperzero]

So without other cooling a homogenous conduction within such an RPV would not exceed

an outside surface temperature above 370 degrees celsius.

(http://www.tepco.co.jp/nu/fukushima-np/f1/images/032_1F3_05141200.pdf)

Okay. Now, to fill the RPV with something that will distribute the heat from the core, which is pooled on the bottom, evenly along the whole inner surface. Oh, wait...

 

[AntonL]

I'm not sure about the dimensions of the RPV ,

but if I assume a height of 21 meter and diameter of 7 meter ,

(http://www.jnes-elearning.org/contents/bk/JNESeL-BK-004.pdf )

and a resulting total decay heat of 7 Mw ,

(http://mitnse.com/2011/03/16/what-is-decay-heat/ )

then an evenly spread of this heat energy around the surface would result in 15100 W/m^2

Which is equivalent to a blackbody temperature of 445 Celsius .

(http://www.wolframalpha.com/input/?i=15100+watts+per+square+meter&lk=1)

So without other cooling a homogenous conduction within such an RPV would not exceed

an outside surface temperature above 445 degrees celsius.

(http://www.tepco.co.jp/nu/fukushima-np/f1/images/032_1F3_05141200.pdf)

(EDITED for change of estimated decay heat for unit 1 to unit 3 )

In the case of unit 1 with a smaller estimated decay heat production of 4.5 Mw this would be 370 degrees Celsius

Interesting analysis, however I think your decay heat load is too high, it would be around 2.7MW today (https://www.physicsforums.com/showpost.php?p=3242513&postcount=3526")

 

[jim hardy]

Based on the available data of the reactor parameters, the combined system of RPV and support plumbing of unit 3 failed already on March 13th (between 9:10 and 9:25 the RPV pressure dropped abruptly from 7.3 MPa to 0.45 MPA, while drywell pressure increased from 0.46 to 0.53 MPa.) This would seem to imply that the dozen or so preventive relief valves you mention, failed too.

Consequently, on March 14th, the day of the explosion, the RPV and the PCV were no longer sharply separated volumes, and a depressurizing of the PCV at that stage would also lead to a depressurizing of the RPV . The data available up to and after the explosion indicates a depressurizing of both vessels in connection with the explosion of no less than 0.1 MPa.

do not the plant logs show they manually opened those relief valves on 13th to depressurize?
That is part of US industry mitigation strategy to lower reactor temperature, hence lower heat into drywell . I was under impression from some press releases that they had got high level direction to do so.
Drywell needs to be kept below 350F or so for two reasons
so electrical penetrations don't melt their polymer seals and leak,,
and metal skin doesn't expand from heat enough to buckle and develop cracks.

So opening them makes RPV and Drywell two connected volumes.

Those WONDERFUL plots that Jorge Stolfi put up show it quite clearly,
http://www.ic.unicamp.br/~stolfi/EXPORT/projects/fukushima/plots/cur/Main.html
select unit 3 Pc X Pd and you see the horizontal line slightly below middle is the depressurization. After that the red and yellow dots show drywell and core remained coupled but offset for a few days. (but core lower than DW by 1/2 atm? instrument error maybe, 1/2 atm on a 100 atm gage isn't bad) .
they got closer in green dots then decoupled.


Are instructions posted anyplace how to imbed pictures and quotes? as you see i am not having much luck.

Have you guys studying the columns seen this picture?
http://www.flickr.com/photos/xtcbz/5705961026/in/photostream/
moderator feel free to imbed if you like, it saves casual readers from having to log in so often.

 

[Borek]

Are instructions posted anyplace how to imbed pictures and quotes? as you see i am not having much luck.

Check your PM box (Private Messages link in the bottom right corner).

 

[MadderDoc]

<..>
In the case of unit 1 with a smaller estimated decay heat production of 4.5 Mw this would be 370 degrees Celsius

I am not familiar with this sort of calculation. It appears to be saying that a blackbody heated from within has a maximum surface temperature which can be calculated with no regards to the energetics of its environment. This seems counter-intuitive. Assuming the temperature of its environment is 370^o, equal to the surface temperature of the RPV then no net heat transfer between the two can occur. On the assumption that the RPV can be no warmer than it already is, while seeing that heat energy is still produced on its the inside, one is led to ask: what happens to that energy?

 

[GJBRKS]

Interesting analysis, however I think your decay heat load is too high, it would be around 2.7MW today (https://www.physicsforums.com/showpost.php?p=3242513&postcount=3526")

I took that figure from an MIT calculation specifically aimed at Fukushima I reactors 2 and 3.

It extrapolates to after 1 year of 11th of March

http://mitnse.com/2011/03/16/what-is-decay-heat/

They address one caveat : Their calculations assume an infinite prior operational time which
would upscale the results slightly , but I doubt that it would correct downwards that much to 2.7MW

However , using your 2.7 MW and this time including the top and bottom ends of the cylinder , it would result in an upper flux of 5600 W/m^2

http://www.wolframalpha.com/input/?i=2.7+MW+%2F+%28%2821+m+*+7+m+*+pi%29%2B%282+*+pi+*+%283.5+m+^+2%29%29%29

Equivalent to 287 degrees Celsius for reactors 2 and 3

 

[GJBRKS]

I am not familiar with this sort of calculation. It appears to be saying that a blackbody heated from within has a maximum surface temperature which can be calculated with no regards to the energetics of its environment. This seems counter-intuitive. Assuming the temperature of its environment is 370^o, equal to the surface temperature of the RPV then no net heat transfer between the two can occur. On the assumption that the RPV can be no warmer than it already is, while seeing that heat energy is still produced on its the inside, one is led to ask: what happens to that energy?

The calculations do not concern themselves with the environmental temperatures.
The named temperatures are above those of the environment.

But that would be a correction of less than 10% , I'm assuming it could be +- more than 10% considering that these are estimates.

And i don't think an evenly distribution of the heat is likely

 

[AntonL]

I wanted to study the initial explosion of unit 3 to check if anything new can be found, I have no further insight to what has been said.

However, I make available the http://k.min.us/illbHq.zip" s of the first 1.5 seconds in 40mS increments (25 frames/second)

The only strange thing is the apparent contraction and as some have said bulging of unit 3 just before the explosion, compare frames 000ms and 040ms,

The contraction I attribute to a mpeg compression or sharpening artifact, but why the west wall should suddenly reflect less light - possibly already starting to crumble or shake as a reaction of what is happening inside.

 

[jim hardy]

"""It's highly unlikely you could over-pressurize the RPV. The support plumbing would fail first and the RPV would depressurize. You don't design the system such that your pressure vessel is what pops first.

Not to mention the dozen or so relief valves installed on the RPV to prevent this from happening. """

Smaller pipes are usually more pressure tolerant than big vessels because of their smaller area.

i believe what happens when you exceed the capacity of the safety valves is the head bolts stretch opening a gap under it and steam blows out sideways.

It's an easy calculation,
Force up = pressure X area of head
maximum force the bolts can hold down is
Force down = area of bolts X yield strength of bolt material

to get area of bolts you need the number of them and their diameter.

yield strength - i saw 125000 psi someplace which sounds reasonable for exotic bolt steel. Here's a reference,
http://www.americanfastener.com/technical/grade_markings_steel.asp
go down to A490 grade near bottom of chart it's 120,000 psi

When the up and down forces equal the head will lift.
Fup = pi/4 X (diameter of head)^2 X Pressure
Fdown = pi/4 X ((diameter of bolts)^2 X (number of bolts) X (yield strength of bolts)

at lift,
Fup/Fdown = 1 = pressure X ((diameter of head)^2 / ((diameter of bolts)^2 X (number of them) X yield strength of bolts)

solve by USWAG method: (Un Scientific Wild A** Guess)
Head = 16 ft diameter, 30 tons USWAG
Bolts = 3 inch and sixty of them USWAG but looks right from ppictures
Bolt yield= 120,000 yield SWAG, not U because it's referenced

When pressure makes Fup/Fdown = 1 head lifts.

1 = Press X ( 16ft X 12 in/ft )^2) / (3in^2 X 60 X120,000 psi)

1= Press X (568.9E-6)

Press = 1/0.0005689 = 1758 psi
A real mechanical engineer would adjust for weight of head by adding weight/area of head,
say 60,000 lbs / (28,953 sq in) = 2 more psi,, bumps it up to 1760 psi.
1760 psi isn't very much pressure for good pipe.

I checked my units and think i did that right.
But it's only back of envelope calc using guesses so don't take it as real.
Somebody knows how many bolts there really are and the actual vessel head diameter.

That's how i'd design a vessel, make its headbolts be the safety valve of last resort.

old jim

 

[MadderDoc]

re unit 3

do not the plant logs show they manually opened those relief valves on 13th to depressurize?

I have no access to the plant logs, only notes I took of press releases at the time of the events, and of observations of the webcam.
Here are excerpts, just what I find may be relevant to your question:

March 12th
11:00 Preparing to implement a measure to reduce the D/W pressure (i.e. venting)

March 13th
08:41 Venting procedure finished
08:56 Radiation at site boundary exceeds limits
09:10-09:25 Large drop of RPV pressure, with increase of DW pressure
10:00 webcam shows vent from unit 3 exhaust stack
13:00 webcam shows vent from unit 3 exhaust stack
14:00 webcam shows vent from unit 3 exhaust stack
14:00 Sea water injection is being attempted followed by boric acid injection
14:00 Safety relief valve has been opened manually

March 14th:
05:00 Water level that has been held at about -2.3 m relative to fuel top goes downscale
06:00 DW and SC pressure goes above design max limits
07:00 Water level comes back within scale, but only at -3.0 m relative to fuel
08:00 Water level indicators erratic or water level unstable
11:01 Explosion

 

[TCups]

Based on the available data of the reactor parameters, the combined system of RPV and support plumbing of unit 3 failed already on March 13th (between 9:10 and 9:25 the RPV pressure dropped abruptly from 7.3 MPa to 0.45 MPA, while drywell pressure increased from 0.46 to 0.53 MPa.) This would seem to imply that the dozen or so preventive relief valves you mention, failed too.

Consequently, on March 14th, the day of the explosion, the RPV and the PCV were no longer sharply separated volumes, and a depressurizing of the PCV at that stage would also lead to a depressurizing of the RPV . The data available up to and after the explosion indicates a depressurizing of both vessels in connection with the explosion of no less than 0.1 MPa.

Or, might it simply imply that the pressure relief valves were bypassed, as by damage and subsequent rupture of one of the connecting feed lines, especially the high pressure steam lines near the top of the RPV? Would that not produce the same observations?

It has been reported that lateral forces of the quake exceeded the design limits of Unit 3.

 

[jim hardy]

""The only strange thing is the apparent contraction and as some have said bulging of unit 3 just before the explosion, compare frames 000ms and 040ms, """

i have speculated whether there might have been a near invisible hydrogen flame already leaving the building at those first instants, it distorted the image while the flying debris took a few milliseconds to accelerate from rest.

warn me when i approach the line, guys.

 

[jim hardy]

Maddrr Doc neither do i have access to logs and may be having a senior moment.
Here's some notes about venting unit 1, i could be remembering wrong unit.

>>>>>>>
Anger rose as TEPCO dithered

TEPCO began preparations for opening the valves around 7 p.m. on March 11. Pressure inside the No. 1 reactor was particularly high.

"Soon, the reactor won't be able to withstand the pressure," said an official of the accident headquarters at the plant, which was keeping in touch with TEPCO's head office via video phone. "We have to vent the pressure immediately."

"Pressure inside the containment vessel of the No. 1 reactor has gone up dramatically," the agency told Banri Kaieda, economy, trade and industry minister, at 12:45 a.m. on March 12. In fact, it had reached 1.5 times the designed maximum, meaning the condition of the reactor was critical.

"To get things under control, we have to pour water into the reactors and then vent the steam that is generated," Haruki Madarame, chairman of the Cabinet Office's Nuclear Safety Commission, told Kaieda.

At 1:30 a.m. on March 12, Kan, Kaieda and Madarame gathered at the crisis management center in the basement of the Prime Minister's Office.

The three urged TEPCO officials to vent the steam as soon as possible. But TEPCO officials said there was no way of opening the valves because there was no power supply.

Exasperated, Kaieda called the utility's head office in Tokyo and the accident headquarters at the plant every hour, pressuring them to open the valves immediately.

TEPCO workers tried to open the valves by manually overriding the automatic system, but struggled to make progress because they had to work in darkness.

At dawn, pressure inside the No. 1 reactor was more than twice the designed maximum.

Eventually, at 6:50 a.m., the government ordered the utility to open the valves under the Nuclear Reactor Regulation Law.

When Kan visited the accident site shortly after 7 a.m. and found TEPCO had not opened the valves yet, he reprimanded company officials. The officials replied they would like to have another hour to make a decision on what to do.

Kan blew his stack.

"Now's not the time to make such lackadaisical comments!" the prime minister told the TEPCO officials.

Yet even still, the utility spent three more hours discussing the matter before finally opening the valves at 10:17 a.m.

Five hours after that, a hydrogen explosion occurred at the No. 1 reactor, blowing apart its outer building.

via Yomiuri



source http://www.houseofjapan.com/local/tepco-tardy-on-plant-emergency

 

[MadderDoc]

<..>
The contraction I attribute to a mpeg compression or sharpening artifact, but why the west wall should suddenly reflect less light - possibly already starting to crumble or shake as a reaction of what is happening inside.

If you can attribute the contraction to artefacts why not go the full Monty and attribute the lessening of reflection from the west wall to artefacts too? Using the 'artefacts' card, nothing in a video should really be inexplicable :-)

No seriously. You should establish for yourself a baseline looking at a series of frames before 000ms. How much bulging and contracting do you see there, how does it look when nothing is ongoing in the building, how much can it all wobble due to artefacts?

I think you will not likely find a contraction similar to the one you see in frame 040ms in any frames before frame 000ms. If that is so, then what you see is an aberration in relation to your baseline and therefore unlikely an artefact. It is the real thing, something is really changing. Same goes for what you see on the west wall.

(You may consider using another video source, the one you have been using appears to have been recompressed resulting in loss of information)

 

[AntonL]

Tepco admit to the possibility that all primary containment vessels of all reactors are leaking.
[URL]http://www.asahi.com/national/update/0514/images/TKY201105140388.jpg[/URL]
english article: http://www.asahi.com/english/TKY201105130192.html
japanese article: http://www.asahi.com/national/update/0514/TKY201105140387.html
which also talks of that the cooling plan for Unit 1 will most likely be abandoned.
3000Tons of water is missing from the unit 1 containment, possibly in the torus basement and also leaked into the ground water.

Also here is the english article of the leaked 100 page report http://www.asahi.com/english/TKY201105130370.html

 

[rowmag]

Tepco admit to the possibility that all primary containment vessels of all reactors are leaking.
[URL]http://www.asahi.com/national/update/0514/images/TKY201105140388.jpg[/URL]
english article: http://www.asahi.com/english/TKY201105130192.html
japanese article: http://www.asahi.com/national/update/0514/TKY201105140387.html
which also talks of that the cooling plan for Unit 1 will most likely be abandoned.
3000Tons of water is missing from the unit 1 containment, possibly in the torus basement and also leaked into the ground water.

Also here is the english article of the leaked 100 page report http://www.asahi.com/english/TKY201105130370.html

English version says 3000 tons of water missing, Japanese version says 3000 tons of water found in basement.

So what now? Fill the basement with cement?

 

[robinson]

I don't think it's speculation to say this is the biggest nuclear mess mankind has ever faced.

 

[swl]

""The only strange thing is the apparent contraction and as some have said bulging of unit 3 just before the explosion, compare frames 000ms and 040ms, """

My opinions:

The building was not contracting. The upper containment walls are beginning to expand in the "0" frame. I can see that the dark roof outline has not moved down, but the white color of the wall does appear to have moved down at the upper edge.

As has been noted, H.264 compression uses inter-picture prediction over as many as 16 frames. This codec is intended to provide very high data compression while maintaining reasonable -motion- picture quality. When set up for streaming video, like on youtube, the data is optimized for a motion picture where you view each frame for 1/25th of a second. It can not be relied upon to provide fidelity of an individual frame for still analysis.

In addition to being subjected to H.264 conversiom, avi conversion, and pray tell what else, the quality of the master was almost certainly of poor quality with low resolution, poor contrast and atmospheric distortion.

Question: Having done my bast to discredit the reliability of the video, does it look to any of you like the ignition point might have been outside the upper southwest corner?

 

[AntonL]

re unit 3


I have no access to the plant logs, only notes I took of press releases at the time of the events, and of observations of the webcam.
Here are excerpts, just what I find may be relevant to your question:

March 12th
11:00 Preparing to implement a measure to reduce the D/W pressure (i.e. venting)

March 13th
08:41 Venting procedure finished
08:56 Radiation at site boundary exceeds limits
09:10-09:25 Large drop of RPV pressure, with increase of DW pressure
10:00 webcam shows vent from unit 3 exhaust stack
13:00 webcam shows vent from unit 3 exhaust stack
14:00 webcam shows vent from unit 3 exhaust stack
14:00 Sea water injection is being attempted followed by boric acid injection
14:00 Safety relief valve has been opened manually

March 14th:
05:00 Water level that has been held at about -2.3 m relative to fuel top goes downscale
06:00 DW and SC pressure goes above design max limits
07:00 Water level comes back within scale, but only at -3.0 m relative to fuel
08:00 Water level indicators erratic or water level unstable
11:01 Explosion

Extracted from NISA status report for Unit 3 http://www.nisa.meti.go.jp/english/files/en20110513-1-2.pdf

March 11th 15:42 Report based on the Article 10 (Total loss of A/C power)
March 13th 05:10 Occurrence of the Article 15 event (Inability of water injection of the Emergency
Core Cooling System)
March 13th 08:41 Started to vent.
March 13th 13:12 Started to inject seawater and borated water to the Reactor Core.
March 14th 05:20 Started to vent.
March 14th 07:44 Occurrence of the Article 15 event (Unusual rise of the pressure in PCV)
March 14th 11:01 Sound of explosion
March 16th around 08:30 White smoke generated.

 

[AntonL]

I don't think it's speculation to say this is the biggest nuclear mess mankind has ever faced.

yes you a right, Chernobyl vaporized their core and spread it over a large area, Fukushima are dissolving their core and burying it in their ground water.

 

[turi]

re unit 3
[...]
March 14th:
05:00 Water level that has been held at about -2.3 m relative to fuel top goes downscale
06:00 DW and SC pressure goes above design max limits
07:00 Water level comes back within scale, but only at -3.0 m relative to fuel
08:00 Water level indicators erratic or water level unstable
[...]

Does anyone here know how those water level sensors work? What could cause them to give erronous info (instead of simply appear offscale or stuck)? If the newly attempted measurements at unit 1 are to be believed the two sensors there showed erronous info for quite some time. Also interesting might be that they both showed more or less the same values. How do two of those sensors go awry in the same way?

 

[MadderDoc]

The calculations do not concern themselves with the environmental temperatures.

No, and that's what strikes me as odd. It is as if this RPV is suspended in empty space at absolute zero- Otherwise I cannot see how one can avoid involving a term representing the temperature of the environment. A blackbody is something that would absorb all radiation incident on it, if I understand that term? It would seem to have to emit that amount of energy again plus the internally produced heat in order to reach an equilibrium temperature. I think.

 

[GJBRKS]

No, and that's what strikes me as odd. It is as if this RPV is suspended in empty space at absolute zero- Otherwise I cannot see how one can avoid involving a term representing the temperature of the environment. A blackbody is something that would absorb all radiation incident on it, if I understand that term? It would seem to have to emit that amount of energy again plus the internally produced heat in order to reach an equilibrium temperature. I think.

Yes ,but :
- considering that the environment is a heatsink and therefore in equilibrium it contributes to an equivalent constant inward flux of 419 W/m^2 (at 20 degrees celsius) , therefore this is a negligable amount considering the uncertainties of the whole.

We can extrapolate likewise for higher temperatures in the surrounding containment :

100 degrees Celsius containment would amount to an additional 1100 W/m^2 above the 15100 W/m^2 for reactor 2 and 3 , thereby increasing the temperature line to 475 degrees from 445 degrees calculated before , so that would be +30 degrees celsius

 

[MadderDoc]

Does it look to any of you like the ignition point might have been outside the upper southwest corner?

I think no one can claim to have actually seen the ignition. It would seem to me to be an extraordinary claim that the ignition point was outside the building. I would like to hear about the supposed mechanism for such occurrence before even considering it.

 

[dh87]

I have fallen behing with my plots due to other work. But now I wonder whether it is worth keeping them updated.

For one thing, TEPCO has been releasing a lot more readings and more often, including plots; and other people have been doing it too.

More seriously, the latest news about #1 mean that *both* its water level readings, for the past two months, were garbage --- not inaccurate, not biased, not noisy, but just total garbage. Since the readings for #2 and #3 have similar values and behavior, it is very likely that they are garbage too. (Indeed the black smoke event for #3 sems to coincide with some major event in the RPV emperatures and other variables --- a core breach perhaps?)

Now what trust can we put in the other measurements? I have this mental image of a room somewhere in the reactor building, half-full with water, with a big chunk of fallen concrete in the middle and all the pressure and water level gauge pipes disappearing under it. Or of the "RPV bottom" termocouple inside the drywell, hanging in mid-air by its wires, gently swaying under a drizzle of warm borated water from a ruptured pipe pipe above.

Anyway, I will think about it over the next weekend, when I have more time. Sorry... and all the best.

Thank you for all the work in maintaining your graphs. They've helped me to try to think about what's been happening. Even if I am 20 pages behind on reading this forum.

 

[mikefj40]

The different photon energy possibilities are listed in the nuclide table. Other types of decays are also listed in the nuclide table with a description of the energy levels. just click on the decay type and it will give you the decay energy diagrams.

http://atom.kaeri.re.kr/index.html

Thanks again... I have some reading to do after Saturday chores!

 

[MadderDoc]

Yes ,but :
- considering that the environment is a heatsink and therefore in equilibrium it contributes to an equivalent constant inward flux of 419 W/m^2 (at 20 degrees celsius) , therefore this is a negligable amount considering the uncertainties of the whole.

Yes, I can understand that, and I agree this is a negligible amount.

We can extrapolate likewise for higher temperatures in the surrounding containment :

100 degrees Celsius containment would amount to an additional 1100 W/m^2 above the 15100 W/m^2 for reactor 2 and 3 , thereby increasing the temperature line to 475 degrees from 445 degrees calculated before , so that would be +30 degrees celsius

Yes, I see, however now we are getting close to my pain threshold for negligible terms. In conclusion, if I understand this now :-), the calculation does strictly yield the maximum surface temperature of a RPV suspended in empty space at absolute zero -- but this is with good approximation the same as the maximum surface temperature in an environment (I assume, to be able to neglect other heat transfer, a low density environment, e.g. air), at up to about 100^oC.

 

[MadderDoc]

Does anyone here know how those water level sensors work? What could cause them to give erronous info (instead of simply appear offscale or stuck)?

My understanding is that when water gets low and the going gets tough in a reactor, there _is_ no well-defined water level anymore to measure. When the water level starts jumping up and down, its time for duck and cover.

 

[MadderDoc]

Or, might it simply imply that the pressure relief valves were bypassed, as by damage and subsequent rupture of one of the connecting feed lines, especially the high pressure steam lines near the top of the RPV? Would that not produce the same observations?

I had to think a bit before figuring out what you are saying and I may have misunderstood. I think you are arresting my statement that multiple relief valves would have to have failed too, and you are right. Funny thing though, to have relief valves that do not open before some 'blow-panel' in the high pressure steam lines gives in.

 

[triumph61]

TEPCO concealed radiation data before explosion at No. 3 reactor
Tokyo Electric Power Co. concealed data showing spikes in radiation levels at the Fukushima No. 1 nuclear power plant in March, one day before a hydrogen explosion injured seven workers.

The Asahi Shimbun obtained a 100-page internal TEPCO report containing minute-to-minute data on radiation levels at the plant as well as pressure and water levels inside the No. 3 reactor from March 11 to April 30.

The data has never been released by the company that operates the stricken plant.

The unpublished information shows that at 1:17 p.m. on March 13, 300 millisieverts of radiation per hour was detected inside a double-entry door at the No. 3 reactor building. At 2:31 p.m., the radiation level was measured at 300 millisieverts or higher per hour to the north of the door.

Both levels were well above the upper limit of 250 millisieverts for an entire year under the plant's safety standards for workers. But the workers who were trying to bring the situation under control at the plant were not informed of the levels.

http://www.asahi.com/english/TKY201105130370.html

 

[SteveElbows]

English version says 3000 tons of water missing, Japanese version says 3000 tons of water found in basement.

So what now? Fill the basement with cement?

This NYT article makes passing reference to NISA announcing that 12 feet of water have been found in the basement:

http://www.nytimes.com/2011/05/15/world/asia/15japan.html?_r=1&hp

On Saturday, the Nuclear and Industrial Safety Agency said that it had found more than 12 feet of water in the basement of Reactor No. 1.

 

[ascot317]

The unpublished information shows that at 1:17 p.m. on March 13, 300 millisieverts of radiation per hour was detected inside a double-entry door at the No. 3 reactor building. At 2:31 p.m., the radiation level was measured at 300 millisieverts or higher per hour to the north of the door.

I've always wondered about this "x or higher". Remember the first weeks when they often measured "999mSv/h or higher"? Is this made by limited personal counters?

Both levels were well above the upper limit of 250 millisieverts for an entire year under the plant's safety standards for workers. But the workers who were trying to bring the situation under control at the plant were not informed of the levels.

Naive press people. Ahh.


I find it interesting that Tepco apparently covers some things up. There's no point in doing so, this series of events will likely undergo more investigative efforts than anything similar before. Not many hiding places except /dev/null. Unless this is just a lapse and not deliberate.