Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[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.

 

[clancy688]

One question regarding the SFP #4 video:

There are bubbles rising in the water... where do they come from? Or rather, what's in a SFP that could produce air bubbles?

 

[~kujala~]

Interesting piece of news from Nuclear News concerning the explosion of unit 4:

The building seems to have suffered a hydrogen explosion, but it is possible
that nobody witnessed the event due to a site evacuation prompted by a radiation release from unit 2 on 15 March.

So perhaps nobody has seen the actual explosion?

Nuclear News also offers their alternative explanation:

It may also have been damaged by the explosion at unit 3.

http://www.world-nuclear-news.org/newsarticle.aspx?id=29978

This goes a little bit in the same direction as the https://www.physicsforums.com/showpost.php?p=3289449#post3289449" by AntonL that hydrogen could have been the result of venting in unit 3, except that the explanation of AntonL is better as the explosion of unit 3 and the estimated explosion at unit 4 happened at different time.
At 11:15 JST on 14 March for Unit 3
At 06:00 JST on 15 March for Unit 4
(Wikipedia)

How sure can we be about the time of explosion of the unit 4 if nobody saw it? Could there be even hours of margin in the estimated time and real time if people around there have not been attentive enough?

 

[Jeff_H]

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)

Would the rising temp be consistent with a sensor placed just at the boundary between liquid and steam, with a falling liquid level?

 

[MadderDoc]

How sure can we be about the time of explosion of the unit 4 if nobody saw it? Could there be even hours of margin in the estimated time and real time if people around there have not been attentive enough?

There was a webcam, that pretty much nails the time of the explosion to some time between 6 and 7 am on March 15th

 

[clancy688]

Nuclear News also offers their alternative explanation:

It may also have been damaged by the explosion at unit 3.

http://www.world-nuclear-news.org/newsarticle.aspx?id=29978

That's highly implausible in my opinion. Sat images of March 14th (taken a few minutes after the Unit 3 explosion) show no visible damage on north and east side of Unit 4.

http://www.digitalglobe.com/downloads/featured_images/japan_earthquaketsu_fukushima_daiichi_march14_2011_dg.jpg

And the roof of Unit 3 plus the debris laying around don't change over the next weeks, so there's been no other explosion after that event.

 

[elektrownik]

About unit 3: 5/8 11:00 314,5C

 

[AntonL]

One question regarding the SFP #4 video:

There are bubbles rising in the water... where do they come from? Or rather, what's in a SFP that could produce air bubbles?

The camera is being boiled - steam bubbles

 

[Dmytry]

Why should they use enriched B-11?

You tell me. France and US flew them 95 and 5 tons of enriched boron 10 a few days in. Not sure how much enriched though.

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 ...)

Well, maybe natural boron would work fine. I too know that the boron is very cheap and readily available and is a common chemical, but I also know that they've been flying it in on airplane for some reason. I don't know if that's because of perfectionism or because you can't dissolve enough natural boron in water to definitely prevent the criticality.

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?

Yep, would be good to know for the worst case. It would depend to the fuel burnup. Fresh fuel has a lot of excess reactivity.

edit: see
http://en.wikipedia.org/wiki/Boron#Enriched_boron_.28boron-10.29
i presume that there's some good reason for enriching boron, 'cause it is obviously quite expensive to do isotope separation.

 

[clancy688]

The camera is being boiled - steam bubbles

But they are not coming from the camera... those two for example, they're coming from between the racks.

 

[SteveElbows]

There was a webcam, that pretty much nails the time of the explosion to some time between 6 and 7 am on March 15th

Indeed.

As far as official info about this event, the wording was quite poor and tried to downplay things regarding unit 4, but anyway:

March 14th 04:08 Temperature of pool is 84 degrees C.
March 15th 06:14 It was confirmed that a part of wall in the operation area of Unit 4 was damaged
March 15th 09:38 Fire spotted at unit 4
March 15th 11:00 Fire no longer seen - presume it went out of its own accord

For example of this information being presented, see parts of this document: http://www.nisa.meti.go.jp/english/files/en20110316-4.pdf

OK so they were very late spotting the fire, but they reported the damage pretty much on time, although using misleading language, we only learned how badly 4 was damaged once we saw photos/video.

Given the timing of unit 3 explosion, I do not have an alternative explanation for what happened at unit 4. It happened within within minutes of the explosive sound at suppression chamber of unit 2, but I don't see how those events could be related. Given that the temperature of the pool was reported at 84C about 26 hours before the explosive event, I still blame the pool, even if we can't see any obvious damage to fuel (can there be significant damage that is not visible?)

 

[Dmytry]

Indeed.

As far as official info about this event, the wording was quite poor and tried to downplay things regarding unit 4, but anyway:

March 14th 04:08 Temperature of pool is 84 degrees C.
March 15th 06:14 It was confirmed that a part of wall in the operation area of Unit 4 was damaged
March 15th 09:38 Fire spotted at unit 4
March 15th 11:00 Fire no longer seen - presume it went out of its own accord

For example of this information being presented, see parts of this document: http://www.nisa.meti.go.jp/english/files/en20110316-4.pdf

OK so they were very late spotting the fire, but they reported the damage pretty much on time, although using misleading language, we only learned how badly 4 was damaged once we saw photos/video.

well yea this translation is a largest nuclear understatement since the Chernobyl's 'electrical equipment fire'.

Given the timing of unit 3 explosion, I do not have an alternative explanation for what happened at unit 4. It happened within within minutes of the explosive sound at suppression chamber of unit 2, but I don't see how those events could be related.

People near #2 could of misidentified #4's explosion sound as coming from #2 for example.

 

[Astronuc]

Enriched boron (B-10 > 0.5) is quited common in the nuclear industry. For a given amount of boric acid, it would be preferable to have more B-10 than the natural concentration would give.

 

[Dmytry]

Enriched boron (B-10 > 0.5) is quited common in the nuclear industry. For a given amount of boric acid, it would be preferable to have more B-10 than the natural concentration would give.

but how bad it would be to run out of enriched B-10 ? I imagine it would be fairly easy to calculate what concentration of B-10 in the water would cancel out water's effect as a moderator... then it could be seen if natural boron can achieve this.

 

[rmattila]

but how bad it would be to run out of enriched B-10 ? I imagine it would be fairly easy to calculate what concentration of B-10 in the water would cancel out water's effect as a moderator... then it could be seen if natural boron can achieve this.

It's mainly the matter of controlling pH. If natural boron is used, more boric acid is needed to get the same reactivity effect, and this makes the pH lower. Depending on the acceptable pH limits and the water chemistry used, this might require addition of base chemicals in order to keep the pH high enough for the core materials.

Regarding the units 1-4 at Fukushima, I don't think the disadvantageous water chemistry resulting from suboptimal pH would make the situation any worse than it already is, taking into account the use of seawater etc.

 

[Astronuc]

but how bad it would be to run out of enriched B-10 ? I imagine it would be fairly easy to calculate what concentration of B-10 in the water would cancel out water's effect as a moderator... then it could be seen if natural boron can achieve this.

That's not really relevant. If they needed a certain level of B-10, then they only need 40% the amount of enrich boron then natural boron. In terms of shipping, the choice would be 95 and 5 tons, as opposed to 250 T and 12 T for natural boron.

The idea is to get as much boron into the system ASAP. Enriched boron is preferred because there is more B-10 especially if one is constrained by solubility limit and/or pH.

 

[NUCENG]

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?

If the venting from unit 3 containment used the hardened vent it was a release of pressure directly to the stack. The off-gas stacks are really just support structures for the exhaust pipes from each unit. The pipes are separate and go all the way to the top of the stack. Even without power to the fans, to get hydrogen to then flow back down the pipe for unit 4 seems less than likely. Pictures of unit 3 seem to show the stack piping is broken at the unit 3 building so after the explosion of unit 3 there may not even have been a way to get hydrogen to the stack from unit 3. Whatever happened in Unit 4 happened after the explosion in unit 3.

If there were enough radiation to make radiolysis a legitimate threat in a spent fuel pool with freshly discharged fuel, it would be a problem for every fuel pool during every refueling outage. That just doesn't happen. And the freshly discharged fuel in SFP4 was at least 4-5 months old.

The latest fuel pool pictures from unit 4 seem to confirm TEPCO reports that there was only minor damage to fuel in the pool. We still haven't seen any reports or evidence of an explosive source in unit 4 other than hydrogen. There doesn't appear to be sufficient damage the fuel in the pool to have released much hydrogen. The stack is not a likely path for hydrogen from unit 3 to unit 4. Nobody has reported any fresh damage to unit 3 from a second explosion there that can explain damage to unit 4.

Meteorite?

 

[SteveElbows]

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.

You did not demonstrate clearly visible damage of fuel racks in the first video. There could have been damage, but it certainly was not visible in any clear way.

 

[clancy688]

Meteorite?

Osama bin Laden may be another option. He was still alive back in March. Jorge spotted him in the SFP of Unit 4, didn't he...? Chernobyl happened 25 years and we still don't really know yet why the whole reactor went KABOOM.
I don't think we'll find any answers as to what happened in Unit 4 even during the following months and years...

 

[NancyNancy]

Interesting piece of news from Nuclear News concerning the explosion of unit 4:


So perhaps nobody has seen the actual explosion?

Nuclear News also offers their alternative explanation:


http://www.world-nuclear-news.org/newsarticle.aspx?id=29978

This goes a little bit in the same direction as the https://www.physicsforums.com/showpost.php?p=3289449#post3289449" by AntonL that hydrogen could have been the result of venting in unit 3, except that the explanation of AntonL is better as the explosion of unit 3 and the estimated explosion at unit 4 happened at different time.
At 11:15 JST on 14 March for Unit 3
At 06:00 JST on 15 March for Unit 4
(Wikipedia)

How sure can we be about the time of explosion of the unit 4 if nobody saw it? Could there be even hours of margin in the estimated time and real time if people around there have not been attentive enough?

I had someone point out that the time when 4 likely exploded was right before sunlight so any of the cameras running may have been off. There was a fire reported somewhere between 4am and 6am.

 

[clancy688]

I had someone point out that the time when 4 likely exploded was right before sunlight so any of the cameras running may have been off. There was a fire reported somewhere between 4am and 6am.

I discovered some video material of the scene after the explosions. But you can't really see anything:

https://www.physicsforums.com/showthread.php?p=3266278#post3266278