Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[joewein]

And why did the emergency cooling system of reactor #1 fail much earlier than in units 2 and 3?

According to the AREVA report the design of unit 1 differs from units 2 and 3 with regards to the offline cooling system.

Unlike its siblings units 2 and 3, unit 1 was an older type called BWR3 (the others were of a type called BWR4). One difference between them is that the BWR4 has a Reactor Core Isolation Cooling (RCIC) system. During a loss of all grid and backup power a steam turbine running off decay heat in the core could still pump water from the Suppression Chamber into the reactor core. The BWR3 makes do with an isolation condensor, which relies on electric pumps to cool and condense steam from the reactor using cold outside water. Once the pumps stop, the isolation condenser stops cooling steam. With the RCIC at least liquid water was being injected as long as there was battery power to control valves and the water in the suppression chamber wasn’t boiling yet.

According to the AREVA report, cooling in the isolation condenser in unit 1 stopped at 16:36 on March 11, less than an hour after the backup diesel generators had failed. By contrast, the RCIC pump in unit 3 continued until 02:44 on March 13, about 35 hours after loss of backup power. In unit 2 the RCIC survived until 13:25 on March 14, some 46 hours after the accident.

Furthermore, the isolation cooling system in unit 1 seems to have been manually switched off while the Residual Heat Removal System was still operating on Emergency Diesel power and wasn't immediately restarted when the diesels (and consequently the RHRS) failed.

 

[elektrownik]

More about radiation in unit 1:

Google translation: NHK www3.nhk.or.jp Extremely high radiation doses the No. 1 building
June 4, at 51 minutes 13
Nuclear melt down "meltdown" in the reactor building of Unit 1 of Fukushima Daiichi Nuclear Power Station is expected to Toukyoudenryoku happened to the survey put the robot, the steam rising from the gap between the floor and piping, found that the radiation dose was measured extremely high mSv per hour near its 4000.
In Unit 1 of Fukushima Daiichi nuclear power plant, the "meltdown" a hole in the reactor, seen as too damaged containment vessel also has accumulated a large amount of water in the basement of the reactor leaked high levels of pollution . The roadmap towards the convergence of the accident, move it out through the cold water pipe pollution, plans to build a recycling system that re-inserted into a reactor, in a full-scale preparation reactor are underway. Thus, three days into the reactor building teleoperator radio, conducted a survey of internal state. As a result, the double doors near the southeast side of the ground floor, has been confirmed that the steam rose up from the pipes have come up from the floor space. In this area, 3000 per hour - is that the radiation dose was measured extremely high 4000 mSv. The reactor building of Unit 1 had a high radiation dose is measured in mSv per hour on June 13 2000, this value is the highest radiation dose was measured at Fukushima Daiichi nuclear power plant so far value. TEPCO, try the steam that leaked out of the water of about 50 degrees have a lot of pressure control chamber of the reactor building basement, trying to further analysis. TEPCO, for now, the high radiation dose was measured because this place is limited, impact on work and has less radiation dose is extremely high, and interfere with future work Do not proceed to consider it

50C ? But it is boiling... and how it can be so hot ? Reactor readings show ~100C but this boiling place is not in torus level, but on ground floor

 

[elektrownik]

http://www.tepco.co.jp/en/news/110311/images/110604_10.jpg

I see now, Hight side pressure - 0,1 MPa, low side pressure 0,2 MPa, and differential pressure - 0,1 MPa
So reactor presure is 0,2 MPa - 0,18 MPA = 0,02 MPa
equation from here: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110602_02-e.pdf
So we should now add 0,1013 to result ?
so 0,1013 + 0,02 = 0,1213 so it is litle bigger than atmospheric pressure ?

 

[Lambert]

this may be off topic but I found it as interesting nontheless :

 

[joewein]

There a proper translation on http://www3.nhk.or.jp/daily/english/04_16.html :

Steam, high radiation detected at No.1 reactor
The operator of the damaged Fukushima Daiichi nuclear plant says steam was observed coming out of the floor of the No.1 reactor building, and extremely high radiation was detected in the vicinity.

Tokyo Electric Power Company inspected the inside of the No.1 reactor building on Friday with a remote-controlled robot.

TEPCO said it found that steam was rising from a crevice in the floor, and that extremely high radiation of 3,000 to 4,000 millisieverts per hour was measured around the area. The radiation is believed to be the highest detected in the air at the plant.

TEPCO says the steam is likely coming from water at a temperature of 50 degrees Celsius that has accumulated in the basement of the reactor building.

 

[elektrownik]

There a proper translation on http://www3.nhk.or.jp/daily/english/04_16.html :

Yes but there is more informations in Japan version

 

[Borek]

The fission products do not go far - only a few microns (2-6 um) with the heavier nuclide going shorter distances, and the lighter one going longer.

Sorry, and thanks for clarification. I guess my statement "highly charged ions going through the fuel rod" wasn't the luckiest one. Several microns - in terms of atomic distances - means nuclei move past several thousands atoms from the place they were created, that's far enough to assume place where they stop is completely random and unrelated to the place of origin.

 

[Borek]

(Steam coming from water 50°C? Doesn't make sense to me...)

Why not? Whether the steam - that is, condensation - is visible, is a matter of many factors, including humidity, air temperature, presence of nucleation sites (dust) and so on.

50C ? But it is boiling...

Is it confirmed it is boiling, or do you just guess it boils because it is steaming?

 

[elektrownik]

Why not? Whether the steam - that is, condensation - is visible, is a matter of many factors, including humidity, air temperature, presence of nucleation sites (dust) and so on.



Is it confirmed it is boiling, or do you just guess it boils because it is steaming?

You can see on tepco video that water is boiling
http://www.tepco.co.jp/en/news/110311/images/110604_09.zip when robot zoom to hole

 

[razzz]

this may be off topic but I found it as interesting nontheless :

Fascinating.

 

[LabratSR]

Unit 1 Radiation Survey

http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110604_01-e.pdf

 

[tsutsuji]

I made the following quote yesterday at https://www.physicsforums.com/showthread.php?p=3336238#post3336238, using copy-paste from the nhk website :

In mid-August, [Tepco] will also install an underground storage tank that can hold 100,000 tons of highly radioactive water.
http://www3.nhk.or.jp/daily/english/03_19.html

Other people have made a similar copy-paste with the 100,000 ton figure ( http://arkanoidlegent.blogspot.com/2011/06/japan-tepco-needs-to-store-100000-tons.html ; http://www.wahlfieber.com/de_du/forum/Bundestagswahl/4793/751/#posting751 )

However, when I access http://www3.nhk.or.jp/daily/english/03_19.html today, I see that the text has been changed with a 10,000 ton figure instead :

In mid-August, it will also install an underground storage tank that can hold 10,000 tons of highly radioactive water.

Friday, June 03, 2011 14:05 +0900 (JST)
http://www3.nhk.or.jp/daily/english/03_19.html

The "storage tank" wording might actually mean "storage facility" consisting of a number of the smaller tanks mentioned at http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110603_02-e.pdf

The original Japanese nhk news at http://www3.nhk.or.jp/news/html/20110603/t10013296051000.html is using the word "tank(s)" without any clue whether it is a singular or a plural. The figure reads 10,000 tons. The installing date information actually reads "aiming the middle decade of August" (which is not the same as starting in mid-August).

A few hours later nhk said :

TEPCO officials say that in the event the filters don't work properly, the utility will complete an additional underground tank for highly contaminated water by mid-August.

Friday, June 03, 2011 20:15 +0900 (JST)
http://www3.nhk.or.jp/daily/english/03_31.html

A few more hours later (June 04, 2011, 18:48 JST), nhk added that an amount of 370 tanks - those with a 120 ton capacity from June 4th to the middle decade of July ; those with a 100 ton capacity from the middle decade of June until the middle decade of August - will be installed, providing a 40,000 ton storage capacity : http://www3.nhk.or.jp/news/html/20110604/t10013318631000.html

Tokyo Electric Power Co, the utility that operates the troubled Fukushima Dai-ichi plant, said two of the 370 tanks were due to arrive today.

http://www.walesonline.co.uk/news/l...er-tanks-for-stricken-n-plant-91466-28819462/

The Yomiuri helicopter photographed the departure of the 120 ton tanks from Kanuma city : http://www.yomiuri.co.jp/national/news/20110604-OYT1T00656.htm

The tank manufacturer Tamada's website has a copy of a picture showing some of the 100 ton tanks waiting in Kumamoto on May 25th : http://www.tamada.co.jp/company/news/110527.php

 

[Lambert]

Fascinating.

So true, what do you expect though? Cheers!

 

[elektrownik]

http://www.tepco.co.jp/en/news/110311/images/110604_10.jpg

I see now, Hight side pressure - 0,1 MPa, low side pressure 0,2 MPa, and differential pressure - 0,1 MPa
So reactor presure is 0,2 MPa - 0,18 MPA = 0,02 MPa
equation from here: http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110602_02-e.pdf
So we should now add 0,1013 to result ?
so 0,1013 + 0,02 = 0,1213 so it is litle bigger than atmospheric pressure ?

weee my computations were correct, look on tepco data summary 6/4 at 12:00
http://www.tepco.co.jp/nu/fukushima-np/f1/images/11060412_table_summary-j.pdf
0,025MPa + 0,1013=0,1263
So where all nitrogen go ?



Ps. also water level in unit 1 sfp hit low record - only 1m, if they will not inject water fuel will be exposed in less than 24 h

 

[GJBRKS]

Is it confirmed it is boiling, or do you just guess it boils because it is steaming?

Not sure if it's water or photons on the CCD ?

Could be the CCD , but seems like waterbubbles ?

http://www.tepco.co.jp/en/news/110311/images/110604_09.zip

[EDIT] Hmmm , on third look they do seem to be waterbubbles ...( from 0:20 sec onwards)

 

[MadderDoc]

Not sure if it's water or photons on the CCD ?

Could be the CCD , but seems like waterbubbles ?

http://www.tepco.co.jp/en/news/110311/images/110604_09.zip

[EDIT] Hmmm , on third look they do seem to be waterbubbles ...( from 0:20 sec onwards)

Yes, it would seem too far fetched to say these are CCD artefacts..

Only two explanations seem to me consistent with what we see
a) boiling water
b) gas mixture escaping through water, either or both of which hot.

 

[MadderDoc]

So, is the cesium a metal or an oxide?

Coming out of a nuclear reaction, presumably cesium atoms (metal) as well as a multitude of cesium ion species could be initially formed, however with cesium ion Cs⁺ being likely the only chemically stable end product.

 

[imandylite]

Packbot video of Steaming pipe junctions - ground floor reactor unit 1

https://www.youtube.com/watch?v=0cA8Kz_bPmM

Or - is it boiling?

 

[AntonL]

Packbot video of Steaming pipe junctions - ground floor reactor unit 1

https://www.youtube.com/watch?v=0cA8Kz_bPmM

Or - is it boiling?

http://www3.nhk.or.jp/daily/english/04_16.html

TEPCO said it found that steam was rising from a crevice in the floor, and that extremely high radiation of 3,000 to 4,000 millisieverts per hour was measured around the area. The radiation is believed to be the highest detected in the air at the plant.

TEPCO says the steam is likely coming from water at a temperature of 50 degrees Celsius that has accumulated in the basement of the reactor building.

The company sees no major impact from the radiation so far on ongoing work, as it has been detected only within a limited section of the building

The steam generated in the reactor must go somewhere, that it is from 50^oC water in the basement is possibly the simpler and non alarmist message

 

[westfield]

You can see on tepco video that water is boiling
http://www.tepco.co.jp/en/news/110311/images/110604_09.zip when robot zoom to hole

FWIW I'm not convinced by the footage, the quality just isn't good enough to see properly. Looking in slow mo at the darker patches, the "water", just doesn't look to me like boiling fluid. More like artifacts I thought.

But also, for it to be visible boiling fluid wouldn't two levels of basement need to be completely and totally flooded to the ceilings? If it was totally flooded and boiling would it just quietly percolate at that pipe penetration or would it be burping water and steam out of that hole much more actively?

Whatever it is or isn't, it's still not a good thing to have going on obviously.

 

[swl]

Regarding the bubbling steam video:

If those are gas bubbles boiling up in the video, they could also be from Nitrogen gas being injected, or air entrained in a water injection or circulation system.
Is TEPCO still injecting Nitrogen into unit 1? If so, does anyone here know the injection point?

Could also be gas, including steam, bubbling up from the RPV via way of it's ventilation path through the torus. Or gas from the boiling lump in the bottom of the dry well, or... nevermind.

And as for the water could it be just water standing in a drain under a steam trap? Are we sure the water in video represents the 50* water in the "basement"?

It looks quite hot to me, but I can imagine too many possibilities to make the video of much use to me.

The high radiation readings sound bad to me, but I'm comforted to hear TEPCO is not overly concerned.

 

[robinson]

The things you learn from the Japanese. I didn't even know steam could be produced by water at a temperature of 50 degrees Celsius. I also thought steam was invisible.

 

[Bioengineer01]

The things you learn from the Japanese. I didn't even know steam could be produced by water at a temperature of 50 degrees Celsius. I also thought steam was invisible.

Can somebody disprove this?

My Hypothesis: Water is in contact with Superhot Corium somewhere in the basement, a layer of vapor exists around the Corium, the outside layer of that superhot vapor is finding its way to the surface through the rest of the water in the basement, that is at 50 C on the average near the surface, where they are probably measuring its temperature.

 

[robinson]

From a physics point of view, what material could be producing that high level of radiation in the water vapor we see in the video?

 

[Bioengineer01]

http://www.chrismartenson.com/blog/exclusive-arnie-gundersen-interview-dangers-fukushima-are-worse-and-longer-lived-we-think/58689#comments
Arnie Gundersen says that Units 1 and 2 can not get any worse because the worst already happened... He also says that the Corium can not achieve re-criticality... That is not what I thought, can somebody clarify this?
Also he makes no mention of the large increase in Iodine-131/Cesium-137 that we saw inside the silt fence of Unit2, I think that the 28th of May... He doesn't think that the Corium will ablate through the concrete. He doesn't say why he thinks that way.

He says that Unit 3 is starting (getting critical) and stopping all the time and can still get a lot worse if the fuel melts through and suddenly falls on water.

He is also concerned about unit 4 SFP crashing. And about the ground water being contaminated by radioactive material.

 

[Borek]

The things you learn from the Japanese. I didn't even know steam could be produced by water at a temperature of 50 degrees Celsius. I also thought steam was invisible.

Water evaporates - producing steam - always, even at room tmeperatures. Leave a glass of water for long enough and it dries out - that's evaporation, no boiling needed.

Steam is invisible, but depending on conditions it can quite easily condense into fog. What people call "steam" is in fact fog. I guess (English being my second language) these things can be also classified as "dry steam" and "wet steam" - the latter containing small, visible water droplets.

 

[Bioengineer01]

Water evaporates - producing steam - always, even at room tmeperatures. Leave a glass of water for long enough and it dries out - that's evaporation, no boiling needed.

Steam is invisible, but depending on conditions it can quite easily condense into fog. What people call "steam" is in fact fog. I guess (English being my second language) these things can be also classified as "dry steam" and "wet steam" - the latter containing small, visible water droplets.

The explanation is a lot simpler, just put a very long and narrow cylindrical container full of water and apply heat to its bottom, after a while you will see water bubbles coming to the surface if the heat at the bottom is enough to vaporize and energize the layer of water at that spot so that it can reach the surface without cooling down below the boiling point. Obviously, the temperature of the surface water (opposite side to where the heat is applied) will be inversely proportional to the height of the cylinder that you used. This case can provide you with a sufficiently long cylinder and sufficient energy applied to the bottom in the form of heat, boiling water bubbles going through water at 50 C in the surface.

 

[robinson]

I guess if you define steam as water vapor, and define fog or water droplets (what we see) as steam, then it all makes sense.

 

[Bioengineer01]

I guess if you define steam as water vapor, and define fog or water droplets (what we see) as steam, then it all makes sense.

Guys, this is not vapor from normal evaporation of water, this is steam coming through the surface of water and distorting the surface in the form of bubbles, you can see the dynamics of the steam bubbles breaking the surface of the water in the video, this has a lot more energy than regular evaporation vapor. Something -The Corium?- has energized these water molecules a lot...

 

[tsutsuji]

http://www3.nhk.or.jp/daily/english/04_16.html


The steam generated in the reactor must go somewhere, that it is from 50^oC water in the basement is possibly the simpler and non alarmist message

Is this steam contaminated ? If it is, don't we need a cooling system to cool this basement to a temperature lower than 50°C in order to prevent contaminated steam from rising into the atmosphere ?