Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[unlurk]

They must be pretty cold then, they're not showing up on IR. I yet have to see evidence for that claim. We've asked this before, were is it? I've been actively looking for it, but it is frustrating to see claims of such but not finding evidence supporting it.

Regarding criticality in the #3SFP, well, #4 blew up without any working reactor. Still, the SFP looks fairly undamaged inside. #3 had a hot reactor in addition to a SFP. #3 was very likely leaking hydrogen into the containment, in addition to the SFP doing the same.

It's even possible that there were numerous hydrogen leaks/sources in the whole building:

the SFP, the drywell-head, the SGTS/venting system. It's known that the containment leaks under high pressure, so do the venting systems. There were probably many cavities filled with hydrogen (even the venting stack pipes were affected). I still believe this was just another hydrogen explosion. Just a very powerful one, possibly with more than one room affected.

Unit four is not at all the same as unit 3.

Here is repost of 6333:

Unit four seems a pretty straightforward case.

Hydrogen accumulated in the building structure, mixed with oxygen and ignited.

This was not a contained explosion, the gasses could expand and compress the interior air throughout the structure before achieving enough overpressure to lift the roof slab and pop out the "blast panels."

I'm not an explosives expert, but I know that an uncontained explosive delivers less energy than one which is contained (think pipe bomb) and I can see that that fact is in play here.

The overpressure on the SFP wouldn't have been all that much.

As for your lack of evidence, does this mean that in your opinion, the site is not laced with dangerous amounts of radiation? That the bulldozers were just catching up on some old landscaping project?

The only people who can "prove" the site is hot or not is TEPCO or the Japanese government. And they are clearly withholding information. Outside of a few pictures with hotspots marked around the 1-4 units which were published in Japanese newspapers and played on Japanese TV news programs, TEPCO has remained mum about on site radiation or near site radiation.

The post #3319 still stands here.

 

[StrangeBeauty]

...TEPCO has remained mum about on site radiation or near site radiation.

Actually, as previously posted:
http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/f1-sv-20110506-e.pdf
Take their accuracy and completeness of reporting as you will of course.

My reading of this thread has been that the precise scenario of the #4 explosion/fire to be very difficult to determine... (as is #3 and #2 -- #1 appears a little more clear cut hydrogen vented to inside of building followed by explosion).

I've heard allusions to fuel rods being found far away from the plant by people such as Gunderson, but haven't seen pictures, or any real evidence other than talk that such is the case. Have I missed something there?

I'd of course like to see a lot more information released on all fronts by those involved.

 

[rowmag]

TEPCO rethinking the hydrogen-explosion hypothesis for Unit 4:

http://www.yomiuri.co.jp/feature/20110316-866921/news/20110509-OYT1T01116.htm

Lack of damage seen in SFP4 videos, along with low water contamination measurements, suggests that the explosion at Unit 4 may not have been due to hydrogen after all. TEPCO is pondering other possibilities, including 100 tons of pump-lubricating oil that are stored in the building, as well as propane tanks that were there for welding.

 

[MiceAndMen]

I've heard allusions to fuel rods being found far away from the plant by people such as Gunderson, but haven't seen pictures, or any real evidence other than talk that such is the case. Have I missed something there?

There was exactly one source for the story about radioactive material being found far away from the reactors. This New York Times story on 5 April:

http://www.nytimes.com/2011/04/06/world/asia/06nuclear.html?partner=rss&emc=rss

It refers to a "confidential assessment" prepared by the NRC which they obtained a copy of. The actual document can be found on the cryptome website with the description "Fukushima Daiichi Reactors Condition Assessment" (daiichi-assess.pdf) here:

http://cryptome.org/nppw-series.htm

That document is dated 26 March 2011 and says in the section on Unit 3 on page 10:

Fuel pool is heating up but is adequately cooled, and fuel may have been ejected from the pool (based on information from TEPCO of neutron sources found up to 1 mile from the units, and very high dose rate material that had to be bulldozed over between Units 3 and 4. It is also possible the material could have come from Unit 4).

That is the beginning, the middle, and the end of the "spent fuel miles away" saga. The information originated with TEPCO, was told to representatives of the NRC, and the document was leaked (I guess) to the New York Times who published the story. Everything else you see, hear or read about this subject derives from that NYT story. "Up to 1 mile" is not "miles away"; it's some distance less than 1.6 km.

 

[rowmag]

Also heard on radio that they are going to try feeding water through a different line at Unit 3 later today, due to the rising temperatures there, since merely increasing the flow rate through the current one is not working, suggesting that the water is not getting where it needs to go for some reason.

 

[AntonL]

SFP-4 spent fuel pool analysis of yesterday shows I-131 further declining with half-life expectancy

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110509e3.pdf

 

[MiceAndMen]

Also heard on radio that they are going to try feeding water through a different line at Unit 3 later today, due to the rising temperatures there, since merely increasing the flow rate through the current one is not working, suggesting that the water is not getting where it needs to go for some reason.

See page 9 of the NRC document reviewed by the NYT above.

Injecting water through the RHR system is cooling the vessel, but with limited flow past the fuel. Water flow, if not blocked, should be filling the annulus region of the vessel to 2/3 core height. Based on the reports of RPV level at one half core height, the reactor vessel water level is believed to be even with the level of the recirculation pump seals, implying the seals have failed. While core flow capability may be affected due to continued salt build up, RPV water level indication is suspect due to environment. Natural circulation believed impeded by core damage. It is difficult to determine how much cooling is getting to the fuel.

Bold emphasis added by me. Of course the water isn't getting where it needs to go. They knew this might be a problem 7 weeks ago, assuming it was they, TEPCO, who gave the NRC guys the information used to make their assessment.

 

[unlurk]

That is the beginning, the middle, and the end of the "spent fuel miles away" saga.

The area we are referring to here is under the control of Tepco and entry to anybody except Tepco employees is prohibited.

If Tepco is attempting to play down the magnitude of the disaster where would you expect other reports to come from?

ALSO:
This quibbling about whether hot spots are a kilometer or a mile or some other distance away from ground zero (unit 3) appears to me just a way to deflect the debate away from salient facts. Who cares what the exact distance of the farthest piece of hot stuff is? I don't.

The fact that unit three blew and generated a shower of debris from a height of several hundreds of meters can not be denied, there is film of the event.

How could there not be radioactive debris a kilometer or so away after that explosion?





Denial is not just a river in Egypt.

 

[StrangeBeauty]

...New York Times story..."confidential assessment" prepared by the NRC...

Thanks. For me, that increases the likelihood of it being true.

SFP-4 spent fuel pool analysis of yesterday shows I-131 further declining with half-life expectancy

http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110509e3.pdf

Those numbers look odd to me. I-131 dropped from 220 to 27 in 16 days (3x half life not 2x) and both isotopes of Cs also falling by far more than their half lives would dictate on those same days (being washed away somewhere?; the turbine buildings?). But then both Cs isotopes increase between apr 29 and may 7 while I-131 decreases less than a half life.

 

[AntonL]

Those numbers look odd to me. I-131 dropped from 220 to 27 in 16 days (3x half life not 2x) and both isotopes of Cs also falling by far more than their half lives would dictate on those same days (being washed away somewhere?; the turbine buildings?). But then both Cs isotopes increase between apr 29 and may 7 while I-131 decreases less than a half life.

Nothing odd about those numbers, with daily addition of fresh water to a salty chemical brew you cannot expect uniform mixing and textbook results

 

[BlueCactus]

Could you please upload them elsewhere, in order to share them with non Japanese readers
that's about 80 pictures it seems

http://www.flickr.com/photos/xtcbz/sets/72157626687253144/

These photos were taken by a person concerned in late April.

 

[unlurk]

My statement:

...TEPCO has remained mum about on site radiation or near site radiation.

Your response:

Actually, as previously posted:
http://www.tepco.co.jp/en/nu/fukushima-np/f1/images/f1-sv-20110506-e.pdf
Take their accuracy and completeness of reporting as you will of course.

You make my case.

My reading of this thread has been that the precise scenario of the #4 explosion/fire to be very difficult to determine... (as is #3 and #2 -- #1 appears a little more clear cut hydrogen vented to inside of building followed by explosion).

There is nothing complicated about the explosion of #4 - except where did the hydrogen come from - and that seems to be answered by the radiolysis explanation. My post #6352 dealt with that. If you want to discuss it I'm game.

#2 is a mystery as far as I know, there is no data available on that.

#1 Was a hydrogen blast but what the exact path of the hydrogen remains unknown - at least to me.

 

[mscharisma]

There was exactly one source for the story about radioactive material being found far away from the reactors. This New York Times story on 5 April:

http://www.nytimes.com/2011/04/06/world/asia/06nuclear.html?partner=rss&emc=rss

It refers to a "confidential assessment" prepared by the NRC which they obtained a copy of. The actual document can be found on the cryptome website with the description "Fukushima Daiichi Reactors Condition Assessment" (daiichi-assess.pdf) here:

http://cryptome.org/nppw-series.htm

That document is dated 26 March 2011 and says in the section on Unit 3 on page 10:


That is the beginning, the middle, and the end of the "spent fuel miles away" saga. The information originated with TEPCO, was told to representatives of the NRC, and the document was leaked (I guess) to the New York Times who published the story. Everything else you see, hear or read about this subject derives from that NYT story. "Up to 1 mile" is not "miles away"; it's some distance less than 1.6 km.

"... and fuel MAY have been ejected ..." clearly means it's POSSIBLE, but NOT CERTAIN.

 

[MiceAndMen]

The area we are referring to here is under the control of Tepco and entry to anybody except Tepco employees is prohibited.

If Tepco is attempting to play down the magnitude of the disaster where would you expect other reports to come from?

ALSO:
This quibbling about whether hot spots are a kilometer or a mile or some other distance away from ground zero (unit 3) appears to me just a way to deflect the debate away from salient facts. Who cares what the exact distance of the farthest piece of hot stuff is? I don't.

The fact that unit three blew and generated a shower of debris from a height of several hundreds of meters can not be denied, there is film of the event.

How could there not be radioactive debris a kilometer or so away after that explosion?

Denial is not just a river in Egypt.

Who is denying anything? The context of this is multiple media sources breathlessly declaring that spent fuel was found miles and miles away from the plant. That's not quibbling, that's correcting inaccurate reporting. It sounds like you're saying you do not intend to let the facts get in the way of your own preconceived conclusions.

 

[unlurk]

miles and miles away from the plant.

Hyperbole much?

 

[MiceAndMen]

There is nothing complicated about the explosion of #4 - except where did the hydrogen come from - and that seems to be answered by the radiolysis explanation.

There is now some question whether the #4 explosion involved hydrogen at all, in which case the radiolysis explanation is incorrect. Start spinning.

 

[unlurk]

There is now some question whether the #4 explosion involved hydrogen at all, in which case the radiolysis explanation is incorrect. Start spinning.

There have been some actual physicists in this thread who have proposed a theory that radiolysis could have provided an ample source for the amount of hydrogen needed for an explosion of that size.

With no electricity there could have been no air circulation in building four and the trickle of radiolysis would have just kept accumulating.

That makes sense to me, because the damage to the unit certainly seems consistent with a hydrogen explosion, undamaged fuel pond and all.


Maybe Astronuc should E-mail some of his friends if Tepco really is going out in left field on this one. The physics forum may be ahead of them on unit four.

 

[|Fred]

http://www.flickr.com/photos/xtcbz/sets/72157626687253144/

THANK YOU

I hope this will be enough for the disbeliever get over the tilting UNIT 4 theory

http://farm4.static.flickr.com/3056/5705932388_dca31f4961_o.jpg
http://farm3.static.flickr.com/2369/5705368411_4a2ee8f0a6_o.jpg
http://farm4.static.flickr.com/3099/5705937752_99f42dca4b_o.jpg

There is some other interesting pictures for ex: it is surprising to see that the cast transfer truck entry show some 'from the inside' blast damage on unit 4 while not on unit 3

 

[AntonL]

TEPCO rethinking the hydrogen-explosion hypothesis for Unit 4:

http://www.yomiuri.co.jp/feature/20110316-866921/news/20110509-OYT1T01116.htm

Lack of damage seen in SFP4 videos, along with low water contamination measurements, suggests that the explosion at Unit 4 may not have been due to hydrogen after all. TEPCO is pondering other possibilities, including 100 tons of pump-lubricating oil that are stored in the building, as well as propane tanks that were there for welding.

There is now some question whether the #4 explosion involved hydrogen at all, in which case the radiolysis explanation is incorrect. Start spinning.

IMHO, Yomiuri Press cannot be taken too seriously. The "Gate Theory" saved by the flood only they reported and I bet that the "Lube & Propane Theory" will remain a Yomiuri exclusive.

However, should it be true then it is really a sad state of affairs that a nuclear power plant can be destroyed by maintenance material. How will nuclear power plants be maintained in the future?

Are the lube barrels that hold potential flammable material nuclear certified? I bet not, just a standard 44 gallon drum.

Are the propane (or is it acetylene that is normally used for welding) and oxygen tanks or cylinders nuclear certified so they can be used in a nuclear power station.

 

[GJBRKS]

http://www.flickr.com/photos/xtcbz/sets/72157626687253144/

These photos were taken by a person concerned in late April.

http://www.flickr.com/photos/xtcbz/5705937752/in/set-72157626687253144/

looking at these pictures I'm amazed at how lucky they were that no one was seriously hurt during the unit #3 explosion.
The force just blew the walls out of the back of adjacent buildings.
The scale of it is enormous ,something that I sometimes miss because of all these birdeye views

 

[sp2]

http://www.flickr.com/photos/xtcbz/sets/72157626687253144/

These photos were taken by a person concerned in late April.

Forgive me if this is old news that I somehow missed, but these pix are pretty incredible.

The first thing that jumps out at me is that a lot of the upper superstructure of R3 and R4 has vanished since the last time I saw new close-ups.
I've seen some indications to that effect in the last few days, but I assumed they were nonsense.

These pix clearly show that a whole lot of structure is gone. (I'd have to dig up some older pix, for comparison, to be sure, but I really don't think it's my imagination, is it?)

What the hell happened to it?

Did they cut a whole bunch of stuff down, or did it fall in an aftershock?

And, either way, why haven't we heard about it before?

(And wouldn't either event pose a gigantic risk? Like of one of those gigantic pillars plummeting into an SFP?)

Somebody help me out here.

 

[|Fred]

..

One article that is relatively unbiased
http://www.scientificamerican.com/article.cfm?id=mox-fuel-nuclear
And an other with some factuals informations
http://www.ans.org/misc/ans-technical-brief-mox-fukushima.pdf

and again while I have no doubt Areva has some interest in the process. But Fukushima is a textbook example of what happens to a GE MK-1 NPP Failure, the main concern should be for the dozen US NPP based on similar design. And so far the "our NPP are not exactly the same , this will never can happens over here" is to me far from convincing.
So you can focus on the 6% mox fuel used in UNIT 3. If you like I'll focus on the 4 Failing MK1 NPP

 

[jim hardy]

@TCups

i have been toying with similar idea, speculating orange flame came from inside containment and squeezed out from under yellow domed top at flange..
Cant prove it was nor can prove it wasn't.

A cloud of hot H2 & steam squeeezing out from under containment cap would go horizontal at first and there's a low place in the wall between reactor and fuel pool for refueling crane to maneuver that'd duct it one direction..

Is this picture credible or was somebody playing with photoshop? it as linked a few pages back.
http://img34.imageshack.us/img34/6077/aerial201133002011.jpg

criticality in pool i don't buy either. They use either boron bearing metal to build the racks or boraflex silicone plastic inserts between the fuel assemblies to assure plenty of shutdown margin. i couldn't figure a credible mechanism for removing the boron.

In the vessel criticality is a lot more likely imho. But pressure readings here, kindly linked by somebody above, infer the vessel held pressure a while after explosion. Any idea where those sensors are and what's their reliability? Pressure dropped from 3 atmospheres to 2 at time of explosion. Sorry for units I'm old and just don't do metric - atmospheres is Kpa/100... 101.3 if one wants to be picky.

and to the several who've asked, hydrazine is used in PWR's to scavenge oxygen out of the water - a trickle of it is injected into the water going in. Being mostly hydrogen it turns free oxygen back into water. I don't know if it's common practice for BWR's.

 

[Samy24]

Also heard on radio that they are going to try feeding water through a different line at Unit 3 later today, due to the rising temperatures there, since merely increasing the flow rate through the current one is not working, suggesting that the water is not getting where it needs to go for some reason.

Looks like they have manged it!
http://www.tepco.co.jp/nu/fukushima-np/f1/images/032_1F3_05100600.pdf

 

[Jorge Stolfi]

IMHO, Yomiuri Press cannot be taken too seriously. The "Gate Theory" saved by the flood only they reported and I bet that the "Lube & Propane Theory" will remain a Yomiuri exclusive.

There were three explosions at about the same time, all three similar in that the damage occurred mostly in the 5th floor. It is hard to believe that they were all caused by freak accidents with lubrication oil or welding supplies; or that #4 was due to an entirely different cause than #1 and #3.

Also, lubricating oil should not create an explosive mixture with air, unless it is heated to its boiling point, which presumably is >>100 C. What would have been the source of the heat? In #4 the reactor was empty so there was no superheated steam anywhere in the building, not even in the SFP it seems. And then oil vapor would presumably explode with an orange fireball and black sooty smoke. I see hardly any sign of that in the videos of the explosions of #1 and #3.

 

[elektrownik]

Looks like they have manged it!
http://www.tepco.co.jp/nu/fukushima-np/f1/images/032_1F3_05100600.pdf

no way, 6 hours and 170C difference ?? strange, or it was sensor error...

 

[razzz]

http://www.flickr.com/photos/xtcbz/sets/72157626687253144/

These photos were taken by a person concerned in late April.

Thanks for those pics, couldn't get them originally. Saying the plant is a disaster area is an understatement. Turbine buildings blown outward, vehicles standing on end, etc.

Unit 4: Unless the exterior skin was built just to rigid, they didn't plan on that type of explosion that occurred thereby undermining the structural support for the SFP. Before the noted explosion there were reports of fires and then the fires burning out but no visual or conformation of the fires or their location at the time. Some educated guesses posted here on possibilities of some other source(s) exploding at Unit 4 were assembles in transit/diesel/lubricants/acetylene bottles or whatever else might have been onsite for the shroud remodel. One of them might be a winner. You might throw in the backup batteries just to sure and not forgetting avenues of travel available from the other Units.

Unit 3, I'm guessing, vaporized nuclear fuels and sent them airborne around the world. I doubt the pellets even survived the heat.

Unit 2 seems to have blown some lower plumbing enabling radioactive lava to flow freely once it cleared the RPV since spreading allows borated water to intermingle on more surface area, no big booms just lots of radioactivity.

Unit 1 seems to have functioned well in this dilemma, too bad though since remaining fuel rods and the melted mix are still contained in the RPV making it harder to cool a ponding of the melt that continues to heat the remaining assemblies above.

 

[Jorge Stolfi]

A cloud of hot H2 & steam squeeezing out from under containment cap would go horizontal at first and there's a low place in the wall between reactor and fuel pool for refueling crane to maneuver that'd duct it one direction..

Is this picture credible or was somebody playing with photoshop? it as linked a few pages back.
http://img34.imageshack.us/img34/6077/aerial201133002011.jpg

criticality in pool i don't buy either. They use either boron bearing metal to build the racks or boraflex silicone plastic inserts between the fuel assemblies to assure plenty of shutdown margin. i couldn't figure a credible mechanism for removing the boron.

Aluminum melts at ~650C; from the description of boral, it seems to be mostly Al, so it should flow down at that temperature. Now, the reaction Zr+H2O is said to begin at 800C or higher. Thus getting rid of the boral seems to be easier than generating the required amount of H2. Or was radiolysis enough?

 

[Samy24]

no way, 6 hours and 170C difference ?? strange, or it was sensor error...

Not all readings are down that much. But you are correct the mass is >100t and there sould be a delay in the temperature change.

Maybe at the measurement point with the biggest drop there was no water before. After the change of the injection path there is now water at that place.

 

[BlueCactus]

TEPCO released a detailed layout of temperature meters for a press corps.

 

[Borek]

Actually, the thought was that a still pool of absolutely pure water might superheat, and that an explosion venting through the fuel transfer chute, particularly one that caused a very violent agitation (atomization?) of the pre-heated water as well as initiating an accompanying, secondary hydrogen explosion in the upper floor might well result in the phase change of a sufficient volume of water to steam to result in an "eruption" from the SFP.

That was cphoenix idea:

https://www.physicsforums.com/showpost.php?p=3255628&postcount=4280

I never liked the idea of superheating, as there is plenty of objects in the water that should easily help to start local boiling (see http://en.wikipedia.org/wiki/Boiling_chips - that's all about rough surface) and remove excess heat. This boiling will be very localized, not different in its effects to bubbles of carbon dioxide evolving as a line of beads in a glass of beer, you must have seen it. However, amount of energy stored in the pool water is impressive, and something occurred to me just now. After the hydrogen explosion there should be an implosion phase - lowering the pressure above water - and that could be enough to start flash boiling.

 

[dh87]

For the #4 explosion, the absence of fuel damage appears to exclude hydrogen generation from Zr oxidation. I am skeptical that radiolysis is sufficient for hydrogen generation for an explosion. Wikipedia says that radiolysis is mainly caused by alpha particles, in which case it's only a major issue if the fuel rods are damaged, I think. It's important to consider that this is a comparative rates argument. Hydrogen diffuses rapidly (Graham's Law), and it's hard to accumulate hydrogen over a long period. Perhaps someone who knows could provide a real radiolysis rate estimate that would refute what I'm arguing, but it appears that hydrogen isn't the cause of this explosion.

Can the #4 explosion be a steam explosion? There are two reported fires in #4. A fire could heat up a steel structure: a crane, a replacement shroud [I have no idea what one is or what it's made of], some steel girders. A hot steel structure could fall into water. There's the SFP, filled with water, the RPV is filled with water, and there's 5 meters of water in the basement of the building, although I don't know how accessible this is to falling things. Can heated steel falling into water make enough steam to blow up the building? I thought that this might be a good explanation, but I calculate that you'd need too much steel, although I might have made a mistake.

 

[MiceAndMen]

There have been some actual physicists in this thread who have proposed a theory that radiolysis could have provided an ample source for the amount of hydrogen needed for an explosion of that size.

Indeed they have, and it's something worth investigating further. And they may be right. The PDF file AntonL linked back on 7 May, "Light Water BWR Radiolysis", is compelling. I lean towards a hydrogen explosion myself in Unit 4 and agree the radiolysis theory could explain it.

Edit: Not worth arguing about.

What's lacking is a good CFD simulation in tandem with a FEA run that demonstrates that a 150 kg hydrogen detonation (or deflagration) can account for the physical results we see in the photographs of Unit 4 post-explosion. (Come to think of it, a similar study for Unit 3 would be most welcome.)

If you're really game, as you say, post that and we'll consider the matter settled. Lashing out at those whom you perceive as having some sort of agenda against you is unbecoming.

 

[elektrownik]

Not all readings are down that much. But you are correct the mass is >100t and there sould be a delay in the temperature change.

Maybe at the measurement point with the biggest drop there was no water before. After the change of the injection path there is now water at that place.

Also if cold water would hit 300C metal there should be much steam, but there wasnt on live webcam
Ubit 4: I want pictures of empty RPV first...

 

[jim hardy]

Aluminum melts at ~650C; from the description of boral, it seems to be mostly Al, so it should flow down at that temperature. Now, the reaction Zr+H2O is said to begin at 800C or higher. Thus getting rid of the boral seems to be easier than generating the required amount of H2. Or was radiolysis enough?

Well in order to melt either the Boral metal or the Boraflex plastic, the fuel would have to be not under water. Then it could melt, if the water were gone.

But without water it can't go critical. It'd have to get covered with water again to go critical and they weren't adding water to pools yet on day of explosion - it's reported to have started days later. They were still adding seawater to reactors.

so that's the catch-22 I'm in on pool criticality.