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AFT = About Fuckin Time!

The key acronym is LOCA (Loss of Cooling Accident), which is NEVER supposed to happen. If it does happen, for ANY reason, the nuke should have NEVER been constructed and/or operated (if constructed by not operated, like the Shoreham nuke (in Long Island next to NYC, then the owner usually goes bankrupt, as was the case with Long Island Lighting Company (LILCO) - which actually did happen, and LILCO bacame LIPA). They (Tokyo Electric) might actually be able to avoid a Chernobyl event, for now, but only barely. That this LOCA event went on for more than an hour is an IMMENSE FUBAR.

We now have TWO confirmed LOCA's and subsequent H2 explosions at the Fukushima complex. To make a big H2 boom, you have to make a lot of H2, which evidently comes from this reaction:

Zr + 2 H2O  -->  ZrO2 + 2 H2

So this means that lots of Zr fuel cladding has turned into zirconia and lots of H2, and that the really hot UO2 fuel pellets (self heating due to daughter products radioactive (via beta emission) decay) are now exposed to hot steam and some nasty "daughters" are puking out of the system via the steam vents. Just to add spice to the gumbo, Unit 3 has about 5% Mixed Oxide Fuel (plutonium 239 based, but also some Pu240).

Supposedly the daughters can provide 5 to 7% of the thermal energy of a fissioning facility, but since the Unit 1 was evidently about to get changed out, this could be more like 15%. For a 480 MW unit, this would mean that 36 to 72 MW of heat had to be removed, assuming that all fission reactions were stopped by the control rod insertion.

Well, that's a lot of heat. Translated, 7.5% residual heat generation is 36 MW is 122.8 MBtu/hr (millions of Btu/hr), and that is close to 126,000 lbs/hr of steam generation at atmospheric or 15,136 gallons/hr = 252 gpm water evaporation). For the metrically inclined, the 7.5% decay heat removal corresponds to an evaporation rate of 57 tonnes/hr of water. At 15%, you can double that. That's a lot of water buckets...... On the other hand, a gasoline powered water pump with a 2" pipe outlet (50 mm) might be able to do the trick, if they have them handy, and if they have a way to pump this water into the system. Power wise, they need about 25 kw engines to pump this water, or about 35 hp ones.

And that is needed for EACH active reactor.

Oh, BTW, they also need lots of cooling for those swimming pools where all those spent fuel rods are "cooling" off. While no where nearly as hot, take those out of water and they will also start glowing cherry red after a few minutes to a few hours. And when those catch on fire, well, that's just another massive load of stuff to hit the fan.

Oh yes, totally safe, nothing for mere mortals to discuss, trust the big government - big corporate hybrid, they know all, they know what is best, just rest your weary head, they will surely pass this test that "no one could have foreseen". And BTW, quit watching that damn You-Tube video of the TWO explosions on the top of the reactor buildings in Japan... that might lead you to think "not correct" thoughts, and if you think incorrect thoughts, that will REALLY lead to bad problems.

What a nasty Black Swan this one is turning out to be. And one of the characteristics of kick-ass Black Swan Events is that they are game changing events. I would bet that this qualifies...

Nb41

by nb41 on Mon Mar 14th, 2011 at 12:43:18 PM EST
nb41:
Supposedly the daughters can provide 5 to 7% of the thermal energy of a fissioning facility, but since the Unit 1 was evidently about to get changed out, this could be more like 15%. For a 480 MW unit, this would mean that 36 to 72 MW of heat had to be removed, assuming that all fission reactions were stopped by the control rod insertion.
You can find the rated powers of the reactors on the wikipedia page.

DaiIchi 1: 460MW
DaiIchi 2 and 3: 784 MW

All the reactors at Dai-Ni, three of the four are undergoing LoCA events, are rated 1.1GW each.

One of the Onagawa Plant reactors (operated by Tohaku, a different utility) is also reportedly in LoC. The ratings are 524MW and 2x825 MW.

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11

by Migeru (migeru at eurotrib dot com) on Mon Mar 14th, 2011 at 12:50:33 PM EST
[ Parent ]
Eeks. Or, as The Onion magazine is known to say in such circumstances, Holy Fucking Shit!

Nb41

by nb41 on Mon Mar 14th, 2011 at 10:17:55 PM EST
[ Parent ]
nb41:
On the other hand, a gasoline powered water pump with a 2" pipe outlet (50 mm) might be able to do the trick, if they have them handy, and if they have a way to pump this water into the system. Power wise, they need about 25 kw engines to pump this water, or about 35 hp ones.

Is this power needed in excess of internal pressure?so would those pumps be able to pump against the Nominal 75 atmosphere internal system pressure?

Any idiot can face a crisis - it's day to day living that wears you out.

by ceebs (ceebs (at) eurotrib (dot) com) on Mon Mar 14th, 2011 at 01:01:01 PM EST
[ Parent ]
I have heard that the pressure was bled down, so it is or should be near atmospheric pressure. Obviously, the higher the pressure difference you pump against the more power the pump would need. This number relates to a 1 ATM pressure drop.

As an ultimate jury rig, you could use a fire truck to pump these flow rates, as long as the pressure drop was not too severe. You could also put pumps together in series.

Anyway, we need to wish those at the site the best of luck. Hopefully they also managed to get the fuel rods out of the pools and into somewhere else before these things went bonkers.

Nb41  

by nb41 on Mon Mar 14th, 2011 at 10:15:33 PM EST
[ Parent ]
Something tells me dry cask storage is going to become a lot more popular in the future.

Peak oil is not an energy crisis. It is a liquid fuel crisis.
by Starvid on Tue Mar 15th, 2011 at 12:45:51 PM EST
[ Parent ]
Off topic: why Niobium?

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11
by Migeru (migeru at eurotrib dot com) on Mon Mar 14th, 2011 at 01:06:54 PM EST
[ Parent ]
Niobium is fairly inert, high melting point and has a low neutron cross section.
by njh on Mon Mar 14th, 2011 at 08:51:27 PM EST
[ Parent ]
A long while ago, I got a patent on the use of a niobium compound that was a catalyst, along with a sister tantalum compound. These were superacids, such as [H2F][NbF6].

Tantalum and niobium are also relatively non-toxic -can be used like titanium inside the human body - and it turns out that your cellphone needs a capacitor made of tantalum and tantalum oxide to work, and that is why tantalum is in such hot demand, and also exploited by some very evil scumbags in central Africa. But, good news, because a company called Vishay in Niagara Falls has just come up with a way to use niobium and it's oxide for the same use. And niobium is much more common than tantalum.

And so, I adopted it for a e-name. And every once in a while, you find people who are "elementarily" aware...

by nb41 on Mon Mar 14th, 2011 at 10:42:38 PM EST
[ Parent ]
We now have TWO confirmed LOCA's and subsequent H2 explosions at the Fukushima complex. To make a big H2 boom, you have to make a lot of H2, which evidently comes from this reaction:

Zr + 2 H2O  -->  ZrO2 + 2 H2

So this means that lots of Zr fuel cladding has turned into zirconia and lots of H2, and that the really hot UO2 fuel pellets (self heating due to daughter products radioactive (via beta emission) decay) are now exposed to hot steam and some nasty "daughters" are puking out of the system via the steam vents.

I thought one known mechanism for hydrogen production was dissociation of cooling/moderator water by neutrons or gamma rays from the nuclear reaction. Can than not possibly produce enough H2 for the kinds of explosions we've seen without assuming the Zircon alloy fuel cylinders have begun to disintegrate?

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11
by Migeru (migeru at eurotrib dot com) on Mon Mar 14th, 2011 at 05:19:22 PM EST
[ Parent ]
One ton of Zr can make about 88 lbs of H2, which is about 15,780 ft^3 of H2. That would probably be enough to take the roof off the buildings, especially as this would be uniformly distributed over a big area - like a fuel-air bomb. It would be ugly.

Ionizing water, or catalytically decomposing water at cherry red temps would make both H2 and O2 which could also recombine, especially with all that ionizing radiation. Maybe some ionizing radiation from a "hot" isotope of Xe or I2 kicked off the explosion that blew off the roof...or maybe just a motor or a switch that was not rated" explosion-proof".

Nb41

by nb41 on Mon Mar 14th, 2011 at 11:00:31 PM EST
[ Parent ]
Checking some other sources like this one, I see that the zirconium reaction is indeed considered the primary source of hydrogen gas during meltdowns, and radiolysis as source of hydrogen gas poses more a problem of accumulation.

I also read that after Chernobyl, to prevent hydrogen gas explosions, plant safety plans foresee the flooding of the vessel with nitrogen so that there is no oxygen to react with. Hence the explosion only outside after venting.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Tue Mar 15th, 2011 at 07:09:09 AM EST
[ Parent ]

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