Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[KateB]

Chief Cabinet Secretary Yukio Edano told a news conference that the government believes that the meltdown was only temporary.
http://english.kyodonews.jp/news/2011/03/81431.html

Hm.

 

[razzz]

Here's an ignorant question...In these of boiling water reactors during the loop of water to steam back to water as it travels and passes through turbine fans blades and back to the reactor, is this water coming in contact with rod casings during the transfer of heat to create the steam? Or is there a heat exchanger isolating the reactor's heated water from the looping water-steam-water to the turbine?

(Yes I know the heavy water reactors have their own isolated heated loop and use an exchanger to pass heat to a separate dedicated loop)

 

[Astronuc]

Here's an ignorant question...In these of boiling water reactors during the loop of water to steam back to water as it travels and passes through turbine fans blades and back to the reactor, is this water coming in contact with rod casings during the transfer of heat to create the steam? Or is there a heat exchanger isolating the reactor's heated water from the looping water-steam-water to the turbine?

(Yes I know the heavy water reactors have their own isolated heated loop and use an exchanger to pass heat to a separate dedicated loop)

Boiling Water Reactors (BWRs) boil water in the core. The steam passes through a dry to remove moisture, and that steam goes directly to the high pressure turbine. The moisture drops back to the annulus on the outside of the reactor baffle, where it mixes with the feedwater which is returning from the condenser under the low pressure turbine. There are various reheaters that collect condensate from the high pressure turbine and LP turbine, and the condensate is used to reheat the water from the condenser as it heads back to the core through the feed water system. The condensate also passes through filters to remove corrosion products.

BWRs are a direct cycle. PWRs have a separate primary system, and a steam generator separates the primary system coolant from the secondary side in which steam is produced and sent to the turbine. The steam side of the PWR is similar to that of a BWR.

 

[razzz]

Thanks for that Astronuc. I guess I couldn't believe that design would ever see the light of day except maybe for military purposes. It would only take 1 to ruin your whole day in a worse case scenario but here you have maybe 3 or more. Nothing like having an 'I' beam protruding out of your spent fuel pond to withdraw your operating permit extension application. Betcha they restart 5&6.

 

[AtomicWombat]

NYT article:

http://www.nytimes.com/cwire/2011/0...a-1-explosions-and-19903.html?pagewanted=all"

A couple of points:
1) The hole in reactor building 2 was deliberately cut to prevent an explosion like that in buildings 1, 3 & 4:
"Braving dangerous conditions, workers had time to remove a wall panel at the top of the unit 2 reactor building providing an exit for hydrogen, avoiding a similar roof-level explosion, he said. The damage to the buildings 1 and 3 and the opening in 2 created an exit route for radioactive releases from the spent fuel pools at the top of the reactor pools."

2) Partial meltdowns (at least) likely:
'In an analysis shared with other U.S. nuclear experts Saturday, Lake Barrett, who led the Nuclear Regulatory Commission's investigation of the Three Mile Island accident, describes the burning of zirconium cladding on fuel rods in the reactor cores after normal cooling operations failed because of a lack of electric power.'

'Barrett predicted that the melted reactor cores at the three Fukushima units resemble those of Three Mile Island's reactor 1: "a bed of rubble with localized melting of composite materials of steel, zirconium, and uranium. Sort of like a highly radioactive steel mill slag-like material. These cores are likely still in the reactor vessels, and are being cooled by seawater injection using highly pressurized fire engine pumps."'

'"This current 'feed and bleed' method of cooling with salt water is not a sustainable long term cooling method. Salt deposits are likely building up in locations in the thermally heterogeneous core rubble pile. This configuration is completely unknown. But the Fukushima reactors, I believe, are much more damaged and contaminated than TMI was and there are three of them in this state."'

 

[Rational Deb8]

Hi Razzz,

This might help: NRC Boiling Water Reactor Systems Overview: http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf

 

[Rational Deb8]

Folks, when someone references an older post by post number, how do I find that post? There must be a way to jump directly to it... if I enter a post number into the search box, I get no returns. Thanks in advance for your help!

 

[AntonL]

something to keep an eye on: pressure in RPV #1 is rising once again:... why?

a pressure increase is expected with the volume of water injected into a closed system

but more worrying the temperature is approaching the 300 degree design limit
below history since last high temperature alarm first temperature reports from 22/3

22/3 11:20 383 degree C .227Mpa_g 33 l/min 11:20
23/3 04:00 >400 degree C .270Mpa_g 300 l/min 03:33
23/3 16:00 305 degree C .358Mpa_g 188 l/min 11:00
24/3 17:00 217 degree C .367Mpa_g 113 l/min 21:45
25/3 10:00 197 degree C .349MPa_g 120 l/min 15:30
26/3 13:00 212 degree C .380MPa_g no new reading
27/3 05:30 212 degree C .407MPa_g no new reading
27/3 09:00 224 degree C .416MPa_g no new reading
28/3 03:00 273 degree C .443MPa_g 113 l/min 14:00

 

[razzz]

Hi Razzz,

This might help: NRC Boiling Water Reactor Systems Overview: http://www.nrc.gov/reading-rm/basic-ref/teachers/03.pdf

Yeah, I get it, I just don't like it.

 

[Gilles]

As 134I has a gamma emission at 847.0 kev (95.4% yield) and 56Co 846.7 kev (100% yield) I could see it being very easy for an operator / software error getting them mixed up.

Assuming gamma spectrometry is the analysis being done of course.

http://ie.lbl.gov/toi/Gamma.asp?sql=&A1=134&A2=134&Z=53

yes but https://www.physicsforums.com/showpost.php?p=3213341&postcount=1602", we see that both I-134 and Co-56 have disappeared after the reanalysis, how is it explainable if there was a blending of two lines?

hope this is not kind of "political" suppression... or may be as they were unable to distinguish between two lines, they just chose to skip them.

Another thought : no idea what the gamma-ray spectrum looks like, but it must be rather crowded and messy... maybe they just publish the most prominent lines they can identify, but the "absence" of some nuclides may just be due to the fact that they cannot distinguish properly their lines between all the others ?

 

[AtomicWombat]

Washington Post article: Source of Contaminated Water

Grim reading.

http://www.washingtonpost.com/world/radiation-levels-reach-new-highs-as-conditions-worsen-for-workers/2011/03/27/AFsMLFiB_story.html"

Quotes relating to source of leaks:

'Unlike in newer reactor designs, the older boiling-water reactors at Daiichi are pierced by dozens of holes in the bottoms of their reactor vessels. Each hole allows one control rod — made of a neutron-absorbing material that quickly stops nuclear fission inside the reactor — to slide into the reactor from below, as happened when the earthquake shook the plant March 11. During normal operations, a graphite stopper covers each hole, sealing in highly radioactive primary cooling water, said Arnie Gundersen, a consultant at Fairewinds Associates with 40 years of experience overseeing boiling-water reactors.'

'But at temperatures above 350 degrees Fahrenheit, the graphite stoppers begin to melt.'

'“Since it is likely that rubble from the broken fuel rods . . . is collecting at the bottom of the reactor, the seals are being damaged by high temperature or high radiation,” Gundersen said. As the graphite seals fail, water in the reactor will leak into a network of pipes in the containment buildings surrounding each reactor — the very buildings that have been heavily damaged by explosions. Gundersen said that this piping is probably compromised, leaving highly radioactive water to seep from the reactor vessels into broken pipes — and from there into the turbine buildings and beyond."'


Me again. Graphite has the highest melting point of any solid (3652 - 3697 Celsius), so the "the graphite stoppers begin to melt" line has me confused.
http://invsee.asu.edu/nmodules/carbonmod/point.html"

 

[AtomicWombat]

I have previously suggested Japan will eventually turn to robots to deal with this disaster.

This Washington Post article discusses the same thing:

http://www.washingtonpost.com/natio...-ours/2011/03/25/AF2A3ClB_story.html?hpid=z1"

'Inside a nondescript warehouse south of Mannheim, Germany, a dozen robots, ranging in size from a low-slung inspection bot no bigger than a toy wagon to a 22-ton Caterpillar excavator, stand ready to respond to a nuclear emergency. With their electronics hardened to withstand radiation, the versatile machines can handle fuel rods as well as monitor doses that would kill a human engineer.'

'But in Japan, where the Fukushima Daiichi nuclear crisis drags into its third week, the question is: Where are the robots?

The answer is disquieting, say Japan’s top roboticists...'

 

[|Fred]

a better picture of the operating floor (I added a few comments)
[PLAIN]http://i.min.us/jjU8wO.jpg

 

[AtomicWombat]

a better picture of the operating floor (I added a few comments)
[PLAIN]http://i.min.us/jjU8wO.jpg[/QUOTE]

Thanks Fred.

It doesn't quite make sense. I see you've oriented it so that the containment vessel lid is in the north west, as it appears in reactor building 4. My understanding is that the SFP, reactor and equipment pool are lined up in the long-orientation of the building (~45 metres), that is north-south in reality, but east-west in your labeling.

The overhead crane straddles this long orientation i.e. bridges the short section of the building (~35 metres). This photo was probably taken from it.

 

[rmattila]

I had thought that BWR's ran with significant coolant cover over the assembly tops - but recently read that no harm would be expected in BWRs during normal operating conditions even, ran with as much as 1/3rd of the top of the rods uncovered, because of steam cooling. Is this correct? Or would it even be correct during cool down or something?

In normal operating conditions, the level lies somewhere between 3 and 5 m above the top of core, depending on plant design. Following a scram, the steam bubbles collapse and the level drops by about 1 m.

If you somehow lose the ability to inject feedwater after a scram, the water will keep boiling away and the top of the fuel rods will uncover in about an hour. In this situation, fuel rods will not be damaged immediately due to steam cooling. There is a rule of thumb based on accident analyses made sometime in the 90's stating that the correlation between (negative) water level and max fuel rod temperature is approximately the following:

-0.5 m -> 450 °C
-1.0 m -> 500 °C
-1.5 m -> 800 °C
-1.8 m -> 900 °C

This rule is valid for the first few days after a scram, and it has a very small dependence on the linear power of the fuel rod prior to shutdown, since more power means more steam, which in turn means better cooling on the top of the fuel.

After the level falls below half core, the steam is no longer able to cool the top of the rods, and fuel damages start to occur. Within an hour or so from this point, all rods can be assumed to have lost their integrity and started to melt.

 

[Borek]

Folks, when someone references an older post by post number, how do I find that post? There must be a way to jump directly to it... if I enter a post number into the search box, I get no returns. Thanks in advance for your help!

I am afraid I am not aware of any fast method. The only approach I can think of at the moment is to browse the thread.

There is a post number in upper right corner of each post, and it is also a link to this particular post, so a best way of referencing the post is to post this link, not just a post number.

This is link to your post I am answering now.

 

[Maxion]

a better picture of the operating floor (I added a few comments)
[PLAIN]http://i.min.us/jjU8wO.jpg[/QUOTE]

Wasn't this from Fukushima Daiichi unit 5 or 6? As in not really relevant when talking about units 1, 2, 3 and four?

 

[AntonL]

'This is far beyond what one nation can handle - it needs to be bumped up to the UN Security Council,' said Najmedin Meshkati, of the University of Southern California. 'In my humble opinion, this is more important than the Libya no-fly zone.'

I fully agree

 

[AntonL]

Edano said he has received a report that the radioactive substances are assumed to be either condensed steam from the reactor containment vessel or radioactive substances diluted by the water released into those facilities as part of cooling efforts

"released into those facilities as part of cooling effort"
What does that mean !
Surely they know the consequences !

 

[AntonL]

>1000mSV outside the building in the sewer system !

emphasis on greater, basement 2 also reported as greater as

URGENT: High-level radiation detected in trench outside Fukushima reactor building
TOKYO, March 28, Kyodo

High levels of radiation exceeding 1,000 millisieverts per hour were found in water in a trench outside the No. 2 reactor's turbine building at the troubled nuclear power plant in Fukushima on Sunday afternoon, Tokyo Electric Power Co. said Monday.

Similarly high levels of radioactivity have been found in a pool of water in the basement of the turbine building at the Fukushima Daiichi complex, raising concerns that radioactive substances may have seeped into the environment, including the sea nearby.

==Kyodo

 

[|Fred]

The picture of unit (5 or 6 I have to check) was taken by Mitsuhiko Tanaka,engineer at Babcock Hitachi K.K., who helped design and supervise the manufacture of the steel pressure vessel for Tokyo Electric in 1975. on reactor n°4 . He was a weasel blower on a cover up during the manufacture of a faulty vessel structure on n°4.

According to M Tanaka the operating floor is the same on the other unit.
According to M TanaKa in his latest web video http://www.ustream.tv/recorded/13573218 Dated 26 Of Mars, The reactor n°1 experienced a LOCA just after the quake due to borken pipes (this was not disclosed)

He indicate that the reactor Pressure vessel operate a 7MPa in regular operation, 12 hours after scram the pressure was down to 0.8 MPa (black line), meanwhile Pressure from the containment vessel raise from 0,1MPa to 0.8MPa 0.4MPa (being the design max)(pink line), and the water drop (yellow line)

edit: during the same webconference it was idicated that tepco said that the situation in reactor 1 was the most critical. Mitsuhiko Tanaka speculated that it was because the fuel melted and reach the bottom of the reactor vessel.
Mitsuhiko base his speculation on the disclosed external temperature of the bottom of the steel vessel reaching 400°



the Mark-1 improved used on the Fukushima plant
[PLAIN]http://i.min.us/jjPBO2.jpg
The pressures of the RPV and PCV and the water level
note number are gage number ie (ABS - 0.1MPa) for CPV (the PCV is filled with Nitrogen)
[PLAIN]http://i.min.us/jjTY2Q.jpg


Wall of the containment vessel with 'cable' of those cable joint being design not to leak befor 300°
[PLAIN]http://i.min.us/jmlgOE.jpg[PLAIN]http://i.min.us/jmliWM.jpg
[PLAIN]http://i.min.us/jjUxY2.jpg[PLAIN]http://i.min.us/jjU0gA.jpg
[PLAIN]http://i.min.us/jjQjQA.jpg

 

[blab31]

Greetings, this is my first post and I'm not that good with english language, i apologize in advance.

I have a question regarding the radioactivity measurements in reactor #2 :

in this document (http://www.nisa.meti.go.jp/english/files/en20110327-1-5.pdf ) i understand there has been mistakes about I-134 and possibly other elements. But even without these I-134 and Co-56 numbers, something troubles me.

As i understand, they can only measure up to 1 sieverts with current equipment there (press reports worldwide are 1 sieverts per hour but original documents show MORE than 1 sievert per hour without more details. In this pdf, measurements inside Unit 3 are at 750 msv/h).

Knowing that for example :
I-131 - Unit 2 : 1.3×10E7 vs Unit 3 : 3.2×10E5
Cs-137 - Unit 2 : 2.3×10E6 vs Unit 3 : 5.6×10E4
the list goes on, but from what i see most elements are about 50 times higher in Unit 2 compared to Unit 3.

My question is : is there a way to calculate (approximately) the real number of Sv/h in Unit 2 (and outside Unit 2 probably now...), as we know Unit 3 water surface is at 750 msv/h ?

Oh, and thank you all for a very useful topic to help us understand the situation

 

[TCups]

Any idea where the steam at video 3:25 to 3:29 originates from
later again at 3:49 to 4:04
seems to come from a crack in the concrete and quiet forcefully
any ideas?

I believe this is may be the top of the gate for the fuel transfer chute of unit 3.

 

[|Fred]

As i understand, they can only measure up to 1 sieverts with current equipment

As far as what was reported on NHK is concerned, the reason why they did not get better measurement was that left in a hurry when during the mesure they saw that they were already over 1 sievert/h .
Since then the Japanese government urged them to get more readings and more accurate reading.

 

[gmax137]

... Graphite has the highest melting point of any solid (3652 - 3697 Celsius), so the "the graphite stoppers begin to melt" line has me confused.

here's the explanation:

...[blah, blah, blah]... said Arnie Gundersen...

As far as I can see, nothing this guy says has anything to do with reality or facts.

 

[AntonL]

for those still interested here is the english version of the revised radiation levels of basement unit 2 water

 

[artax]

some interesting information on the heat outputs of fuel in fuel pools and time to boil off water.

http://allthingsnuclear.org/post/4133270698/where-did-the-water-in-the-spent-fuel-pools-go

 

[Gilles]

so confirming again that a blending of I-134 and Co-56 lines has mysteriously become undetectable ...

 

[curious11]

I believe this is may be the top of the gate for the fuel transfer chute of unit 3.

If that's the case, does that mean the void in front of the gate (ie closer to the camera) in that image is the SFP, which appears empty in the frames prior to your screengrab?

 

[Bodge]

Are the daily updates still coming out from TEPCO re. reactor temperatures, CAMS and containment pressures?

I haven't seen any new data for a while.