Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[unlurk]

I just simply cannot bring myself to imagine the conceptual failure to engineer and store spent or unspent fuel rods in any arrangement inside SFP racks, or anywhere else outside of a reactor core that would allow even the remote possibility of criticality to occur.

That sounds almost "faith based" IMO.
Faith based reasoning rolls off me like water off a ducks back.

!?? Has that indeed been confirmed? Did I miss it? Gulp.

Post # 3319 at page 208 was never rebutted that I know of.
https://www.physicsforums.com/showthread.php?t=480200&page=208


TCups, You have added the search for answers which would be all but lacking here if not for you. I don't mean to be critical of you personally.

But I think you are fighting somebody else's battle here. So you get to take the slings and arrows of righteous indignation which follow.

Sorry about that.

 

[Dmytry]

Maybe it is an empiric trust in the nuclear energy industry sadly misplaced, but, I must believe that "criticality" inside a reactor core, using uranium fuel rods enriched to 3% requires a pretty carefully planned geometric arrangement of fuel rod assemblies, control rods and moderators that doesn't happen by chance.

BS. It is closer to 5% for unspent rods in BWR, and it used to happen for 2..3% naturally a while back:
http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

This accident is not a scenario of letting two hemispheres of pure plutonium get too close, or pouring concentrated uranium salts in liquid solution from several smaller containers into a single large container too quickly.

I just simply cannot bring myself to imagine the conceptual failure to engineer and store spent or unspent fuel rods in any arrangement inside SFP racks, or anywhere else outside of a reactor core that would allow even the remote possibility of criticality to occur.

Google 'boral'. Compressed mix of boron carbide and aluminium dust.

I think you have some sort of severe misunderstanding as of why the very careful geometry is necessary. It is necessary to sustain the controllable criticality over a wide range of uranium concentrations (from fresh to old fuel), and furthermore burn up the fuel equally. Also, the xe-135 is produced during reactor operation, with a good lag. xe-135 is a neutron poison and it limits lifespan of fuel. But after you take the spent fuel out, and xe-135 decays, the spent fuel has some criticality margin again.

Really, the thought that the criticality is something hard to achieve is how most of the criticality accidents have happened (the mundane ones, not dramatically stupid like Slotin's)

 

[ascot317]

And fuel rods from the SFP of unit three are currently scattered about the Fukushima one site. I hope we are in agreement on that.

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.

 

[RealWing]

Some interesting facts about dense packing and criticality in this document. It also discusses fuel cooling as the water level drops.

Reducing the Hazards from Stored Spent Power-Reactor Fuel in the United States http://www.princeton.edu/sgs/publications/sgs/pdf/11_1Alvarez.pdf

Because of the unavailability of off-site storage for spent power-reactor fuel, the NRC
has allowed high-density storage of spent fuel in pools originally designed to hold much
smaller inventories. As a result, virtually all U.S. spent-fuel pools have been re-racked
to hold spent-fuel assemblies at densities that approach those in reactor cores. In order
to prevent the spent fuel from going critical, the fuel assemblies are partitioned off from
each other in metal boxes whose walls contain neutron-absorbing boron. It has been
known for more than two decades that, in case of a loss of water in the pool, convective
air cooling would be relatively ineffective in such a “dense-packed” pool. Spent fuel
recently discharged from a reactor could heat up relatively rapidly to temperatures at
which the zircaloy fuel cladding could catch fire and the fuel’s volatile fission products, including 30-year half-life137 Cs, would be released. The fire could well spread to older spent fuel. The long-term land-contamination consequences of such an event could be significantly worse than those from Chernobyl.

Page 24
Figure 8 shows the value of the neutron multiplication factor keff in an infinite
square array of 4.4% enriched fuel at various burnups as a function of the spacing
between the rod centers (the array “pitch”) in a pool of unborated water.
It will be seen that, for burnups of less than 50 percent, the open array is critical
at a pitch of 2.6 cm and that the neutron multiplication factor increases as the
pitch decreases to about 1.6 cm.

 

[TCups]

That sounds almost "faith based" IMO.

TCups, You have added the search for answers which would be all but lacking here if not for you. I don't mean to be critical of you personally.

But I think you are fighting somebody else's battle here. So you get to take the slings and arrows of righteous indignation which follow.

Sorry about that.

The only "battle" I am waging is in my own mind.

The only criticality (or lack thereof) of which I can be sure lies is in my thought processes.

Did "sudden criticality" occur in SFP3? Maybe, I don't know, but

Neutron source ≠ fuel rod.

High level radioactive debris ≠ fuel rod.

A small, exposed fragment of a damaged fuel rod ≠ irrefutable evidence of criticality

Did very small fragments of fuel rods get scattered for up to a mile? Maybe, I don't know.

If a substantial piece of a fuel rod blew out of SFP3, it almost certainly did not end up 1 mile away, IMO.

Per private correspondence with those much more knowledgeable than I, it appears that an exposed spent fuel rod would heat rapidly in air and be easily visible on thermal images.

Have I seen a definitive picture of a substantial piece of an exposed fuel rod, either by standard or thermal imagery, outside of the SFP or core of any reactor in any of the preceding 6347 posts? -- I don't think so.

Might there be some other explanation besides "sudden criticality" that powered the explosion(s) at Bldg 3 and SFP 3? Maybe, I don't know.

I do know that it is bedtime for Bozo, though. I will sleep on it.
PS: Wake me up if Bldg 4 falls over, please.

 

[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.