Japan Earthquake: nuclear plants

rowmag

The Japanese version is a bit clearer: the plan is to "water entomb" all three reactors by filling up their containment vessels with water, after nitrogen purging. They plan to start this with Reactors 1 and 3 soon or right away, but have to seal up the leak in the containment vessel for Reactor 2 before they can do it there:

http://www.yomiuri.co.jp/zoom/20110417-OYT9I00585.htm

The announced plan so far only goes up to "medium-term." I imagine core unloading is part of the long-term plan.

|Fred

Could you please point to the item you are identifying as concrete slab.
Could you please point out to the picture you are referring to


I can't see any thing in the available visual evidences sporting that

@astronuc
http://www.youtube.com/watch?v=9Yl7UGfNQDc
full video

Astronuc

According my records, Unit 3 started up toward the end of October, 2010. It had about 4.5 months of operation at the time of the earthquake.

MOX fuel in unit 3 would have very little impact on the subsequent decay heat. It had very little exposure. For the most part, MOX fuel behavior at low exposure is no different the UO₂fuel behavior. I know this from experience. I also contributed to a report on MOX for TEPCO about 20 years ago.

The 2nd and 3rd cycle, and possibly 4th cycle, fuel is most at risk from decay heat.

The presence of MOX is largely irrelevant to the Fukushima accident. One utility had expressed interest in MOX, but withdrew due to commercial/finanical issues, not technical issues.

The MOX facility could have the capability to manufacture BWR fuel as well as PWR fuel.

tsutsuji

Packbot(s) entered into reactor buildings 1 & 3, after opening some of the doors connecting with the turbine buildings. Measurement results are expected to be released on April 18th or later : http://www.jiji.com/jc/c?g=soc_30&k=2011041700293

ceebs

Tepco robot film

TedNugget

Look over how small the shock wave is from Reactor Building 1. Not like a typical shock wave that projects in a hemisphere. For some reason this little shock wave was channeled by a building with older construction methods that allowed it an escape.
Look over the rebar hanging into SFP#3 and elsewhere. I'm still going with a much larger energy release in #3 versus Bldg #1 and that would be from explosions. A 'jet of flame' couldn't accomplish clean separation of the rebar from concrete.

tsutsuji

The first part of that video is a zooming on the still photographs released at http://www.tepco.co.jp/en/news/110311/index-e.html . It is not a release of a video taken by packbot(s).

MadderDoc

The buoyancy of water vapour is considerably more than for hot air (cf. water 18g/mol vs. atmospheric air 29 g/mol).

MadderDoc

Hydrogen explosion => severer structural damage to upper part of building => crash of overhead crane => critical damage to service deck => steam and whatnot explosion from the CV => objects going high in the air along with it => the most dense of those coming right back down, hitting destructively the NNW end of the building.

jmelson

I agree, that there would have been clear evidence of such an explosion.
The O2 tanks have fuse plugs that are supposed to melt and vent the tank in a non-explosive manner when subjected to fires, etc. They don't always work, of course, and a jet of O2 spewing from the fuse plug would also be a major hazard.


Jon

TCups

REGARDING THE INTERNAL BALLISTICS OF EXPLOSIONS IN CONFINED SPACES

I cannot speak with authority about hydrogen gas + oxygen explosions, but I can speak with authority about reloading ammunition with various gunpowders and primers so, for what its worth, consider this:

Reloading is very tricky and the limits of a safe reload are determined by the absolute pressure that develops in the cartridge and subsequently in the barrel of the firearm behind the projectile. Exceed the safe pressure and your firearm becomes a bomb.

The internal pressure developed depends on the weight of the projectile, the length & diameter of the barrel, and the speed that the primer and powder burn, as well as how firmly the bullet is crimped in the neck of the cartridge. It may seem counterintuitive, but high power rifles develop the most extreme pressures, muzzle velocities and bullet energies with slow burning powders. The tighter the bullet is crimped, and the more powerful the primer, the faster the pressure rises within the cartridge, and the more energy it develops. But the heavier the bullet used in a given rifle load, the lighter and slower burning a powder charge must be to safely propel the bullet without exceeding the safe pressure limits, because acceleration of the heavier bullet down the barrel takes longer, and more pressure builds behind the bullet.

As an analogy, again, for what it may be worth, the containment of the upper portion of Bldg 1 seems to have been structurally weaker than that of Bldg 3 or 4. When the ignition of the hydrogen gas occurred, the pressure in the top part of Bldg 1 rose very rapidly, and it blew out relatively quickly, without the internal build up of larger pressures, and perhaps without the efficient and complete ignition and combustion of all of the contained gas mixture.

The explosions in Bldg 3 and 4 were much more tightly contained, or "tightly crimped", so to speak. A much greater internal pressure (and heat) build up might have been possible, with a longer burn time (and here, we are talking only fractions of a second) and more complete combustion of the internal gasses before the external building exploded. If so, then much more energy might ultimately have been released when the external containment did explode, even starting with about the same amount of combustible gas within the building.

Perhaps this was even greater in the case of Bldg 3 than Bldg 4 because Bldg 3 was in service and during operation, as someone pointed out earlier, many of the internal doors of Bldg 3 were closed.

If the kinetic energy from the stored heat in the water of SFP3 released as steam is a correct scenario, then that, added to the hydrogen explosion, gives even more energy to the explosion of Unit 3 (and perhaps Unit 4?).

etudiant

The striking difference between the two explosions, at least to a layman, is that whereas building 1 exploded with a clean shock wave, almost a textbook case. the building three explosion was a much messier affair. Lots of flame and smoke, blasts going up and sideways, almost Hollywood production values.
It would be helpful to understand the basis for these differences, because there may be quite different mechanisms at work. It is for instance interesting that building 2 may in fact have had an even more damaging explosion, yet there is much less external apparent damage.

elektrownik

Can anyone look on new nisa report and write here what think about new data ? They add values from many sensors: http://www.meti.go.jp/press/2011/04/...10417002-2.pdf

etudiant

It has been suggested elsewhere that the fuel rods could have been protected effectively against failure by a thin gold coating, to protect the zirconium cladding from oxidation.
Is this valid even if the fuel rods overheat substantially because of lack of cooling?
Obviously the gold coating could fail once the temperature reaches the melting point of gold, but a very thin coating might well remain intact even if above melting.
Any studies or references would be very much appreciated.

|Fred

Beside the cause of the explosion , one could notice that the roof and wall structure of unit 1 and 3 are different.
Unit 1 does not seems to have been made to contain an explosion

Dmytry

Gold, Au-197, captures a neutron and turns into Au-198 , then beta-decays (half life about 2 and half days) into Hg-198 , stable mercury. AFAIK, gold has big enough neutron capture cross section for gold to be practically unusable in reactors.
Putting this aside, I don't think thin coating would help a lot if it reaches melting point of gold or zirconium, or even earlier when gold starts to diffuse into zirconium.

Dmytry

Exactly! I've been doing production for some studio at Hollywood, in fact (not explosions though, just regular clouds). To be exact, I've been developing software for rendering of clouds, that can do explosions. I even did some mushroom clouds with it.
http://dmytry.com/mojoworld/bigshrooms_aa3_pp_tiled.jpg
Movie explosions are made by blowing up a small charge inside a balloon of gasoline. Physically, they are equivalent to tank rupture. In this case, rapid venting of a HUGE volume of hydrogen + very hot steam fits the video perfectly. Most definitely it does not look like a detonation or deflagration of hydrogen-air mix at all. If you fill entire building with hydrogen at above detonation limit (above 60% hydrogen or so), then you might obtain this result, but then it is absolutely inconceivable you would not have substantial volume of hydrogen at detonation concentrations, with shockwave.
Movies try to use as slow explosions as possible for safety reasons.

If I were to make a CGI shot for movie that looks like building 3 explosion, using fluid simulation, I'd just create huge volume of hot air there (during timespan of 0.5 second or so). It would not cool very much by adiabatic expansion because it wouldn't be created at very high pressure. I'd also colour it burning for the fireball.
Product of typical explosion are hot at very high pressure, and cool down rapidly by adiabatic expansion, and thus don't look hollywood-ish at all. You need something that is hot at not so high pressure.

edit: I just realized, why nukes make such awesome mushroom clouds, whereas explosives typically don't. Chemical explosions produce huge amount of hot gas at extremely high pressure, which, once it expands, is not hot. Precisely what we seen in #1 video. I believe #3 is only perceived as explosion at all thanks to Hollywood 'explosions'.