Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[triumph61]

Two new Videos
http://www.tepco.co.jp/en/news/110311/index-e.html

 

[NUCENG]

How could Tepco have upgraded the seismic stability of their plant?

I would regard it as impossible the modify the concrete and steel construction physically. Maybe they just accepted that design criteria should be 600 gal. Without being able to do much about it, other than shutting down the reactors.

"The design basis acceleration for both Fukushima plants had been upgraded in 2008, and is now quoted at horizontal 441-489 Gal for Daiichi and 415-434 Gal for Daini. The interim recorded data for both plants shows that 550 Gal was the maximum for Daiichi, in the foundation of unit 2 (other figures 281-548 Gal), and 254 Gal was maximum for Daini. Units 2, 3 and 5 exceeded their maximum response acceleration design basis in E-W direction by about 20%. Recording was over 130-150 seconds. (Ground acceleration was around 2000 Gal a few kilometres north, on sediments.)"
http://www.world-nuclear.org/info/inf18.html

http://www.gengikyo.jp/english/shokai/Information_15_080416.htm

The above link is to a summary reportby JANTI of Japanese utilities responding to the 2006 NISA initiative to reevaluate seismic design basis. According to Attachment 1 there are two values of Ss for Fukushima Daiichi, For inland crustal earthquakes the value is 450 Gal. However for an oceanic intraplate earthquake such as that on March 11 the value is 600 Gal as was reported by WNA. So I guess we were both right. Attachment 2 summarizes the results of the reanalysis performed by the different utilities.

And now back the other way. They weren't finished upgrading to 600 Gal

http://www3.nhk.or.jp/daily/english/01_39.html

 

[ViewsofMars]

Here’s a TEPCO press release pertaining to the Plant Status of Fukushima Daiichi Nuclear Power Station (as of 10:00 am, May 8):

*Updates are underlined
All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down.

Unit 1 (Shut down)
-Explosive sound and white smoke were confirmed after the big quake
occurred at 3:36 pm on March 12. It was assumed to be hydrogen explosion.
-At approximately 2:30 am on March 23, seawater injection to the nuclear
reactor through the feed water system was initiated.
-From 3:37 pm on March 25, we started injecting freshwater and are now
injecting fresh water by a motor driven pump powered by the off-site
transmission line. From on April 27, we have increased the amount of
injecting freshwater from approximately 6 m3/h to approximately 14 m3/h.
At 10:14 am on April 29, we put the amount of injecting freshwater back
to approximately 6 m3/h.
-As it is suspected that hydrogen gas is accumulated inside reactor
containment vessel, we commenced the valve opening operation concerning
injection of nitrogen gas into the reactor container vessel at 10:30 pm
April 6th and commenced injection at 1:31am April 7.
-At 10:01 am on May 6th, in order to make nuclear reactor flooded to the
top of Fuel range, we have increased the amount of injecting freshwater
from approximately 6 m3/h to approximately 8m3/h.

Unit 2 (Shut down)
-At approximately 6:00 am on March 15, an abnormal noise began emanating
from nearby Pressure Suppression Chamber and the pressure within the
chamber decreased.
-From 10:10 am on March 26, we started injecting freshwater to the reactor
and are now injecting fresh water by a motor driven pump powered by the
off-site transmission line.

Unit 3 (Shut down)
-Explosive sound and white smoke were confirmed at approximately 11:01am
on March 14. It was assumed to be hydrogen explosion.
-From 6:02 pm on March 25, we started injecting fresh water to the reactor
and are now injecting fresh water by a motor driven pump powered by the
off-site transmission line.

Unit 4 (Outage due to regular inspection)
-At approximately 6:00 am on March 15, we confirmed the explosive sound
and the sustained damage around the 5th floor rooftop area of the Nuclear
Reactor Building.
-At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.

Unit 5 (Outage due to regular inspection)
-Sufficient level of reactor coolant to ensure safety is maintained.
-At 5:00 am on March 19, we started the Residual Heat Removal System Pump
(C) in order to cool the spent fuel pool.
-At 2:30 pm on March 20, the reactor achieved reactor cold shutdown.
-At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.

Unit 6 (Outage due to regular inspection)
-Sufficient level of reactor coolant to ensure safety is maintained.
-At 10:14 pm on March 19, we started the Residual Heat Removal System Pump
(B) of Unit 6 in order to cool the spent fuel pool.
-At 7:27 pm on March 20, the reactor achieved reactor cold shutdown.
-At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.

Operation for cooling the spent fuel pools
-On May 7th, we sprayed water to Unit 4 by the concrete pumping vehicle
from 2:05 pm to 5:30 pm.
-We will continuously conduct further water spray depending on the
conditions of spent fuel pools, if needed.

Others
-The transfer of high level radioactive wastewater in Unit 2 to the
Centralized Radiation Waste Treatment Facility was temporarily suspended
at 9:22am on May 7th, due to construction of injection piping (reactor
feeding water system) to reactor of unit3. The construction work has
completed and we re-started the transfer at 4:02 pm.
-From March 27, transfer of accumulated water in Unit 5 turbine building
to a condenser has been conducted, and water with the amount of
approximately 600 m3 has been transferred from March 27 to May 2.
From May 2, we have started work relating to the set up of exhausters, in
order to improve the working environment inside the reactor building of
Unit 1. At 4:36 pm on May 5th, all of exhausters (6 units) were started
to operation.
-We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.
http://www.tepco.co.jp/en/press/corp-com/release/11050802-e.html

 

[yakiniku]

What mistakes is he referring to? The release of the radiated water, or sharing of the information regarding it?

The wording of the translation is ambiguous, but my cynical side says this email looks like a caution to the concerned parties to keep their mouths shut.

Apologies about the ambiguity of the translation. As mentioned by rowmag and ernal_student, the mistake that is referred to, I believe is the way in which the information was shared. It does not imply that the information should or should not be revealed.

 

[elektrownik]

I don't know now, from new video fuel looks 100% undamaged so I don't know how there could be such big explosion in unit 4

 

[AntonL]

Reactor 3 temperatures
Higher cooling rates do not tame temperature rise
With the bottom head temperature now at 152^oC and showing a constant rate of increase, surely indicates that something very hot is lying in the bottom of the reactor that is not cooled by the water above it. This temperature sensor and the HVH sensor are the two sensors that Tepco have high confidence in as it is not marked #3 (under investigation)
[PLAIN]http://k.min.us/ilrAJa.JPG

 

[Dmytry]

I don't know about Japan and about the time when the units were built, but at least some (if maybe few) people did consider the effects of a possible hydrogen explosion, see the paper linked to in post #6055.

Ohh come on. 2 or 3 blow out panels. There we can see blow out roof, walls, and even the blow out pillars.

In general, I would also have expected that NPPs would be engineered a bit safer than that, but they survived the earthquake itself pretty well, as it seems. Too bad they apparently "forgot" about tsunamis...

there's no telling how well the buildings have survived the earthquake itself, after the tsunami and explosions. The only thing you can say is that buildings did not fall over. (also i don't think its visibly leaning. If it was it would of fell over shortly thereafter).

You see, the way things are done... first it was engineered without considerations for one in 100 years events and beyond (to save money), which really is not something you'd expect. Then when political situation has changed and there was more demand for oversight, the safety was 're-evaluated' to show on paper that it is safe.
Think about it, the way things should be done, tighter margins of error on new simulations should lower the max. predicted quake, not raise it.

 

[elektrownik]

Reactor 3 temperatures
Higher cooling rates do not tame temperature rise
With the bottom head temperature now at 152^oC and showing a constant rate of increase, surely indicates that something very hot is lying in the bottom of the reactor that is not cooled by the water above it. This temperature sensor and the HVH sensor are the two sensors that Tepco have high confidence in as it is not marked #3 (under investigation)

From current data: http://www.tepco.co.jp/nu/fukushima-np/f1/images/00_05080600.pdf we can see that water level drop litle once again.

 

[Dmytry]

Reactor 3 temperatures
Higher cooling rates do not tame temperature rise
With the bottom head temperature now at 152^oC and showing a constant rate of increase, surely indicates that something very hot is lying in the bottom of the reactor that is not cooled by the water above it. This temperature sensor and the HVH sensor are the two sensors that Tepco have high confidence in as it is not marked #3 (under investigation)
[PLAIN]http://k.min.us/ilrAJa.JPG[/QUOTE]
water is not only a coolant, but also a moderator and a washer-out of boron.

By now they really should've already gotten the on-site lab to analyse samples right away to check for short living isotopes. They were offered such stuff, but of course for them to take any nuclear accident - specific equipment is to admit that failure to have their own has contributed to disaster.

 

[AntonL]

I don't know now, from new video fuel looks 100% undamaged so I don't know how there could be such big explosion in unit 4

this new underwater video of SFP4 certainly seems to rule out that SFP4 boiled dry and Hydrogen produced by overheating fuel rods and, so how did the Hydrogen get into reactor 4 building? In my opinion, only two possibilities remain:
1. Hydrogen being pumped into the building during venting of unit 3. Unit 3 and 4 share a common exhaust stack and there was no power for fans to work to aid the exhaust procedure.
2. Radiolysis of water as perhttps://www.physicsforums.com/showpost.php?p=3287847&postcount=6068"

Do you have any other ideas?

 

[Dmytry]

this new underwater video of SFP4 certainly rules out that SFP4 boiled dry and Hydrogen produced by overheating fuel rods

How so? The pool is full with 5 core loads or so, most of them too old to ignite by themselves. 1 core is recent. A reactor is 1/5 of the pool.
The second video avoids looking at the damaged racks visible in the first video. Really, you need a sense of scale. How much larger the pool really is than the reactor core. Pool's 20% damaged is a reactor 100% damaged.
Radiolysis: nonsense. The radiolysis would be about same as before the accident, and same as when video was taken. Can you see giant number of hydrogen bubbles rising? I can't. Just a few bubbles here and there. Not cubic metres per hour level bubbling.
edit: also, try stop the video when its briefly looking at 'bottom left' corner of pool that the first video was off. I don't see anything inconsistent with the look of first video.

 

[GJBRKS]

I don't know now, from new video fuel looks 100% undamaged so I don't know how there could be such big explosion in unit 4

From my viewpoint it is you who sees 0% damage ,which says nothing about the true amount of damage. How can you tell it is not damaged ?
And from your conclusion you question the explosion and make it into a 'mysterious' explosion ?

I do understand that the condition is not how you expected.

I'm getting particularly interested in such a video from unit 3

 

[elektrownik]

The fuel sets should be damaged in upper part because when water boil off it would expose first upper part of fuel, but on new video, upper part of sets looks undamaged, there is also no change in rack shape, to generate hydrogen you need big temperature, if fuel sets would get so big temperature to generate hydrogene they would be more damaged also, thermal decomposition need 2000C...

 

[PietKuip]

water is not only a coolant, but also a moderator and a washer-out of boron.

By now they really should've already gotten the on-site lab to analyse samples right away to check for short living isotopes. They were offered such stuff, but of course for them to take any nuclear accident - specific equipment is to admit that failure to have their own has contributed to disaster.

They are checking for La-140 (40 hours halflife) and monitoring neutron detectors, according to IAEA Miroslav Lipar.
http://www.slideshare.net/iaea/technical-briefing-11-0505

 

[biffvernon]

Temperature conditions at night make it easier for the steam to rise and escape ?

(which is actually strange as temperature inversions occur more often at nighttime :

http://apmru.usda.gov/aerial/Publications/2008 Pubs/Fritz Low level Inversions 2008.pdf

It would however create more atmospheric stability , so better results from spraying

)

I doubt whether temperature inversions dictate pumping timings. More important than inversions would be whether the wind is off-shore or on-shore. The video shows clouds moving right to left which is at least along-shore northwards if not on-shore. There are probably other reasons for the timing.

 

[ranchorelexo]

Here is some temps for reactor 3 since the start of the month, not sure what all the different readings are though.

http://www.tepco.co.jp/nu/fukushima-np/f1/images/032_1F3_05081100.pdf

 

[AntonL]

How so? The pool is full with 5 core loads or so, most of them too old to ignite by themselves. 1 core is recent. A reactor is 1/5 of the pool.
The second video avoids looking at the damaged racks visible in the first video. Really, you need a sense of scale. How much larger the pool really is than the reactor core. Pool's 20% damaged is a reactor 100% damaged.
Radiolysis: nonsense. The radiolysis would be about same as before the accident, and same as when video was taken. Can you see giant number of hydrogen bubbles rising? I can't. Just a few bubbles here and there. Not cubic metres per hour level bubbling.
edit: also, try stop the video when its briefly looking at 'bottom left' corner of pool that the first video was off. I don't see anything inconsistent with the look of first video.

One point I accept we might be and possibly are looking at the cool fuel assembles

I beg to differ:
Full Reactor load = 548 fuel assemblies
Spent fuel in pool = 1331 assemblies
New fuel in pool = 202 assembles

Hot fuel just under 1/3 of all fuel assemblies and not 1/5.

1kg Steam has 1.7m³ volume at atmospheric pressure

We also know that 70+tonnes of water are being evaporated per day
that is 119000+m³ of steam, last night we had a nice demonstration how this https://www.physicsforums.com/showpost.php?p=3289122&postcount=6128" when not blown away.

According to Light Water Reactor Hydrogen Manual by Allen L Camp et al radiolysis mostly occurs in boiling water where the steam carries away the Hydrogen, in non boiling water the H2 and the O quickly recombine, so I would not discount radiolysis in boiling SFP that quickly, possibly others might want to comment this.

Video could have been made after a lengthy water spray operation to cool the water long enough to stop or reduce vigorous boiling such that inspection is more successful by increasing visibility.

 

[AntonL]

Here is some temps for reactor 3 since the start of the month, not sure what all the different readings are though.

http://www.tepco.co.jp/nu/fukushima-np/f1/images/032_1F3_05081100.pdf

In above table some RPV temperature is exceeding the design limit of 300^oC.

Please could a kind knowledgeable person translate the headings

 

[triumph61]

These two things are moving...??

 

[Rive]

These two things are moving...??

I dunno, but those 40 assemblies at the center of the pic are from the last load IMO. Those are the only ones with visible glowing.

Ps: now we have enough pictures to make a drawing about the pool and make some count about the assemblies- at least we will know how many were not seen.

 

[AntonL]

These two things are moving...??

Movement due to hot water rising

On the right lower diagonal we see a fuel rack with new fuel. Earlier it was reported that fuel assemblies have plastic cap, I think that is what we are seeing here

 

[MiceAndMen]

Apologies about the ambiguity of the translation. As mentioned by rowmag and ernal_student, the mistake that is referred to, I believe is the way in which the information was shared. It does not imply that the information should or should not be revealed.

Thanks to you and the others who commented on it. No apology needed, the misunderstanding was mine.

 

[zapperzero]

Can you see giant number of hydrogen bubbles rising? I can't. Just a few bubbles here and there. Not cubic metres per hour level bubbling.

Careful. Unless I lost some zeroes along the way (all too likely), 1 cubic metre per hour is 278 cubic centimetres per second. That's ONE round bubble about 8 cm across every second (or a number of smaller ones). To put it another way, the average human goes through about half a cubic metre of air an hour.

I'm sure most of what's in those bubbles we see now is steam but... dunno, cubic metres per hour sounds quite as if it were in the realm of the possible, especially if the pool was hotter earlier on (my intuition is more steam means more radiolysis, I bet water self-shields otherwise).

 

[MiceAndMen]

Careful. Unless I lost some zeroes along the way (all too likely), 1 cubic metre per hour is 278 cubic centimetres per second. That's ONE round bubble about 8 cm across every second (or a number of smaller ones). To put it another way, the average human goes through about half a cubic metre of air an hour.

I'm sure most of what's in those bubbles we see now is steam but... dunno, cubic metres per hour sounds quite as if it were in the realm of the possible, especially if the pool was hotter earlier on (my intuition is more steam means more radiolysis, I bet water self-shields otherwise).

Also keep in mind that if the pool is full then the tops of the fuel assemblies are about 8 m under water. The gas in each bubble will occupy a larger volume when it gets to the surface. If that rate of bubble generation is constant and continuous and is H2, it's not insignificant.

 

[imandylite]

New video Spent Fuel Pool of Unit 4 of Fukushima Daiichi Nuclear Power Station

http://www.youtube.com/watch?v=QVqfPCsl2AA"

 

[imandylite]

Video of team working Inside of Reactor Building of Unit 1

http://www.youtube.com/watch?v=1CFZblqvw9s"

 

[MadderDoc]

<..>
Ps: now we have enough pictures to make a drawing about the pool and make some count about the assemblies- at least we will know how many were not seen.

Yes. We appear to have seen enough fuel racks to hold the recorded number of assemblies in the pool. Here is a rough lineout of the stacking in the pool, as much as can be gleaned from the two released videos.

 

[elektrownik]

Unit 3 is 314,5C now, this is really big...

 

[GJBRKS]

Unit 3 is 314,5C now, this is really big...

This morning at 0600 it was 202 C :

http://www.tepco.co.jp/nu/fukushima-np/f1/images/00_05080600.pdf

Do you have a link to the source ? I can't find it at the usual locations ...

(and somehow TBS decides to zoom in on unit 1+2 , leaving unit 3 off camera ...)

 

[imandylite]

This morning at 0600 it was 202 C :

http://www.tepco.co.jp/nu/fukushima-np/f1/images/00_05080600.pdf

Do you have a link to the source ? I can't find it at the usual locations ...

(and somehow TBS decides to zoom in on unit 1+2 , leaving unit 3 off camera ...)

Just looking at the stats myself

Link:

http://www.tepco.co.jp/nu/fukushima-np/f1/images/032_1F3_05081630.pdf"

 

[MadderDoc]

In above table some RPV temperature is exceeding the design limit of 300^oC.

Please could a kind knowledgeable person translate the headings

Here's what Google Translate gives for the headers, (change in the temperatures over the last week)

1. N4B Water Nozzle Temperature (93.7 --> 202.1 gr.C)
2. RPV bottom head top (122.3 --> 255.6 gr.C)
3. RPV flange body (99.6 --> 310.1 gr.C)
4. Lower temperature pressure vessel (116.5 --> 151.9 gr.C)
5. RPV stud temperature (98.8 --> 253.6 gr.C)
6. RPV flange body Lower temperature (154.6 --> 173.3 gr.C)
7. Relief safety valve 2-71D Leakage (91.3 --> 158.2 gr.C)
8. Relief safety valve 2-71F Leakage (96.9 --> 108.8 gr.C
9. Main steam isolation valve 2-86A Rikuofu (61.2 --> 63 gr.C)
10. D/W HVH return temperature (101.7 --> 157.6 gr.C)
11. Bellows RPV (137.3 --> 208.6 gr.C)
12. S/C Pool A water temperature (40.6 --> 40 gr.C)
13. S/C Pool B water temperature (40.6 --> 40 gr.C)

 

[MadderDoc]

I found this photo somewhere several weeks ago. Google found it again at

http://www.japannewstoday.com/wp-content/uploads/2011/04/FukushimaSpentFuelRodPoolUnit3-1.jpg

By the title, it would seem to be a close-up of the edge of #3's spent-fuel pool, obviously after the explosion, presumably taken by a camera attached to the pump crane. What are those two gray bars at the top left? (They are too smooth and the wrong color to be rebars, and their ends are closed so they do not seem to be conduits.)

I can't see how this motive can be anywhere near the spent fuel pool of unit 3.
It looks more like the edge of a pit or a manhole than a spent fuel pool. For a starter, where's the steel liner?

 

[fluutekies]

[...]
The cooling water is leaking, which means that they are losing boron, and eventually they will run out of boron, at which point cooling could become impossible as non borated cooling water would cause criticality.
The boron in question is not ordinary boron, but enriched boron-10 which is not readily available.

Why should they use enriched B-11? It would be very expensive and scarce. Natural occurring boron contains 20% B-10 with 80% B-11.
Boric acid H₃BO₃, Borax Na₂B₂O₇ and even Boron trioxide B₂O₃ are bulk chemicals and very cheap. (I don't think TEPCO needs high grade qualities anymore ...)

An aqueous solution of the above mentioned chemicals can be prepared either on- or off-site. Really no big deal.

Does anybody know which concentration is needed to effectively absorb neutrons with B to avoid criticality?

 

[MadderDoc]

Why should they use enriched B-11? It would be very expensive and scarce. Natural occurring boron contains 20% B-10 with 80% B-11.
Boric acid H₃BO₃, Borax Na₂B₂O₇ and even Boron trioxide B₂O₃ are bulk chemicals and very cheap. (I don't think TEPCO needs high grade qualities anymore ...)

An aqueous solution of the above mentioned chemicals can be prepared either on- or off-site. Really no big deal.

Does anybody know what concentration is needed to effectively absorb neutrons with B to avoid criticality?

From what I've read, boron is used up to a few thousand ppm in the cooling water.

 

[StrangeBeauty]

This morning at 0600 it was 202 C :

http://www.tepco.co.jp/nu/fukushima-np/f1/images/00_05080600.pdf

Do you have a link to the source ? I can't find it at the usual locations ...

Just looking at the stats myself

Link:

http://www.tepco.co.jp/nu/fukushima-np/f1/images/032_1F3_05081630.pdf"

The second doc has more readings. The two temps from the first doc map to column #1 and #4 in the second doc. Column #3 has the 300+ C reading but all readings are climbing -- not a good sign.