Japan Earthquake: nuclear plants

Rive

There was those steam plumes coming from the reactor, maybe? Iodine, Cesium - both can travel by steam, AFAIK.

Wait, they had taken samples from SFP#2??

Dmytry

this same very limited fuel damage would of released over a thousand times the observed amount of Cs-137 (given the ratio of i-131 to cs-137 in the old fuel), or alternatively, this fuel damage (and chemistry) would have to be over a thousand times more selective in releasing the iodine versus cs-137 than anywhere else. I'm not saying it proves criticality in sfp4, they might have used contaminated seawater for cooling (but if so, why did not TEPCO give it as explanation?). I'm saying that it doesn't cut it to handwave about chemistry when it is over 1000 times more selective than anywhere else (drains, ditches, ocean, fish bodies...) . If there is something this good at scrubbing out cs-137, that's be WONDERFUL news because they could use it to clean their nasty water.
edit: also, note. 1 mol of i-131 has 1360 times the radioactivity (in Bq) of 1 mol of cs-137, this rules out compounds such as CsI as explanation for the ratio.

MadderDoc

From the scenario, a 1000 tons of water in pool, superheated to about 110 deg C.
This system is unstable, the excess temperature 10 deg. C it is above the boiling point represents the energy available to suddenly vaporize some part of the water.

Water has a heat capacity of 4.18 MJ/ton/degree Celsius, so with 10 degrees and 1000 tons of water, that gives you 4.18*10*1000= 41.8E3 MJ of energy available for vaporization of water.

It takes 2.257E3 MJ/ton to vaporize water, so with 41.8E3 MJ available, this would suffice to vaporize 41.8/2.257 = 18 tons of the water in the pool.

PietKuip

I had a closer look at those data now.

The ratio of I-134 to I-137 is almost constant (almost always between 0.85 and 0.90), so there do not seem to be too many typos in those numbers.

The table contains some short-lived isotopes like Te-129 with its 70 minute half-life. But it is present because of Te-129m, which has a 34 days halflife. Generally, the tables show Te-129 activity at about half that of Te-129m. Except for March 15, when it is only 10 %. This could be a typo?

There is also I-132 with its 2.28 hour lifetime. It is the daughter of Te-132 (3.27 day halflife). Generally, the I-132 activity is about half that of Te-132. The largest deviation from that is March 16, when I-132 is listed with a higher activity than Te-132.

The ratio of I-131 to Cs-132 is rather variable. Probably this depends on rain etcetera. But the data point for I-131 on March 22 does not seem reliable.

So what is wrong with the Japanese? Why don't they make plots like the German test ban monitoring people do? Why not provide some interpretation?

jpquantin

Wouldn't it also happen in BWR cores then? Boiling water, high radiation would generate lot of hydrogen, which would not recombine (boiling + steam environment). This means cores would generate a lot of hydrogen, a lot more than observed, don't you think?

BTW same for Zirconium oxydation by steam in boiling environment.

StrangeBeauty

(all this in reference to SPF4)
Isn't another problem with the superheating scenario the fact that the site was experiencing almost constant aftershocks of varying degrees throughout this time period which would have created disturbances in the water which, along with the many nucleation sites mentioned by Borek, would inhibit/prevent superheating?

GJBRKS

https://netfiles.uiuc.edu/mragheb/ww...Structures.pdf

"Steam being quenched from the primary vessel into the torus under high pressure would act as a rocket and could cause vessel displacement"

Has the idea that the full top of the unit 3 RPV was blown off already been debunked ?

It would be consistent with the 1 atm pressure reading



source : http://www.abovetopsecret.com/forum/...g2#pid11221435

Rive

There are still living personnel on site, after a month. Such damage would make that site like Chernobyl -> some seconds at work, and then run for safety...

mrcurious

It has been suggested salt buildup (from the seawater injection period) at the bottom of the RPV could be insulating corium that deposited there from the partial melting.

|Fred

This non sense has been ruled out in march.

Jorge Stolfi

It occurred to me that *IF* the situation depicted below occurred in an SFP, and *IF* it led to the occurrence of some chain fission, then the water level would be unstable and could start to oscillate. Namely

water level inside assemblies rises --> moderation of neutrons increases --> chain fission increases --> fuel heats up --> steam pressure inside the assemblies rises --> water inside assemblies get pushed down

I presume that if water is boiling inside the assemblies the pressure there would be higher than atmospheric, since the top support plates and the assembly head impede the flow somewhat. Since it would take some time for the extra heat of fission to travel from the fuel to the cladding, the pressure within the assemblies would oscillate in sync with the water level but with some delay --- i.e., the push would be stronger on the way down --- tending to amplify the oscillation rather than to oppose it.



EDIT In fac,t the water level may start oscillating even if there is no chain reaction at first, just from the delay of heating and boiling the water. However, as the top of the wave gets some distance above the surviving boral, then the chain reaction should restart, no?

TCups

Aren't cesium and iodine volatile components that would travel with the vented steam? It seems to me (lay opinion) that this is entirely consistent with steam venting from the reactor vessel into the primary containment (damaged lines or vessel?) and then into the SFP3 (ie, through the fuel transfer chute).

As for the superheated water being very unstable, heck yes -- but the hypothesis was that the "critical" moment of superheating was immediately followed by the steam explosion, and that the explosion and venting of the contents within the primary containment was, in fact, the "last straw" impetus for the steam explosion that caused that criticality.

Is it also possible that criticality occurred, the water/steam was ejected from the SFP, and the contamination with cesium and iodine occurred either as a consequence of the criticality in the SFP or after the pool was refilled? Maybe. A lot of steam was still leaking at the apparent location of the transfer chute after the explosion.

Irrespective of the exact cause initiating the steam explosion, an open connection from the primary containment of Unit 3 to the contents of SFP3 seems to be supported by the water analysis, right?

~kujala~

They did:

http://www.asahi.com/english/TKY201104300099.html

Now the really interesting question is are they going to admit this might also have happened in SFP 2 and SFP 3 but in a larger scale. It's a possibility if the hoses for SFP 4 and SFP 2&3 sprayings were located on different places. But not the only theory.

But if they admit it they must also admit that their calculations concerning the leak into the sea might be heavily underestimated. Which might be the problem?

Jorge Stolfi

From various reports that I have read, it seems that many nuclear plant workers are temporary people "from all walks of life, bartenders etc.", often unemployed or in financial straits; with no special training or previous construction work experience, hired for a very short time and trained to do a very specific task only. Thus it is not surprising if they are clumsy, inefficient and unsafe when faced with an unforeseen event --- such as a stuck crane hook.

jlduh

The analysis this guy is giving is wrong based on the picture on which he is drawing the supposed reactor, simply because he places it at the wrong place! The reactor is normally centered in the middle of the North/South axis (it's normally offset towards the East on the East/West axis) , but the part of the picture where he is drawing the circle is completly offset to the North side.

See there is no metallic structure over the place where he is drawing the circle, while this remaining structure from the roof is present in the middle of the building after the explosion.



I'm not saying anything about the actual condition of the reactor (but at least it seems that some sensors for temps are still working!) but for sure the stuff the guy is showing is NOT the remains of the reacto because it's clearly at the wrong place!

GJBRKS

Things are at the wrong place in a lot of places ...

Thought so allready , good to have that cleared up

clancy688

One thing that hasn't been mentioned:

D/W radiation sensors are at the top of the containment, near the cap. They wouldn't give any data, not even bogus data, if that part of the reactor would be gone.