Japan Earthquake: nuclear plants

Joe Neubarth

They failed about thirty minutes after the Earthquake (and reactor Scram) because they no longer were there.

Joe Neubarth

With ruptured fuel plates, a release of high pressure steam would carry some entrained solids with it. The question is how much?

Reno Deano

The fact that they can get into the plants and grounds around them indicate that there are no spent fuel rods from the SFPs laying about.

83729780

tsunami wave receding from plant:



video:

http://www.youtube.com/watch?v=oqeb2GnBKrU

Borek

Could be I misread the information Astro posted here:

http://www.physicsforums.com/showpos...6&postcount=46

My impression was that the tsunami wave was first and they stopped some time later, but now I see it can be read differently - they started immediately and stopped when the wave came.

Joe Neubarth

Most of us are still trying to find out what is happening and what actually happened.

I am convinced that we had some fuel meltdown. I also know that the steam release to decrease pressure on the reactor carried considerable radiation release with it. That cesium and strontium and iodine came from at least one of the reactors.

Some on here seem to think that Reactor Number Three had a full melt down and loss of fuel material through the reactor vessel.

I keep on looking and can not find a reference to the pressure of Reactor Number three at the present time. Those of you in the know, can you post the present values if they have been released by Tokyo Electric?

tadjik

Could it be ... that :
http://www.nisa.meti.go.jp/english/f...110325-1-4.pdf

Supression chamber : 2 atm
Dry water : atmospheric
Temperature : relatively low
Radioactivity similar to other reactors

turbo

That is likely the case, Borek. Power turbines are large, but delicate and they trip on anomalous vibration, and likely the plant was set to scram its reactors on input from seismic sensors. Earthquake takes out the turbines and reactors, and the tsunami arrives later and takes out the emergency backup generators. Battery back-ups are limited and can't take the place of backup generators - maybe they have the capability of providing critical instrumentation and closing or opening critical valves to fail-safe conditions.

Reno Deano

If Cesium and Sr got out, where are the other long lived fission products? If am not wrong, there were no significant quantities of long lived fisson products reported to have beern blown by the steam into the environment around and offsite of the plant. Sure there is reactor core and SFP bundles damaged, but some what contained within their respective locales.

Jakeh

No expert but as I understand it (from here or elsewhere) the battery power controls valves, the back-up system pumps themselves being powered by steam from the reactors. Which is pretty clever for as long as the valves can be controlled.

The amount of battery power available must be a possible lesson-learned thing. 8 hours wouldn't be acceptable for a mobile phone. That's probably very unfair. But also true.

First post here as well, I've been watching this unfold through here. Thanks to everybody, by far the best resource I've found on the web.

Gilles

Hi everybody

do you know the chemical properties of compounds and cesium and iodine ? iodine is very volatile, what about Cs and Sr compounds ? could it explain the fact that they could have been emitted together with water vapor , but not heavier elements ?
(1st post too - hello especially to other French people here - very interesting forum)

jlduh

About the generators, i think this info will have to be clarified by further inquiry but what i heard about was that they started (probably just after the quake) then stopped after. Looking at the vidéo above of the flooding of the plant we can understand that they have been flooded and probably destroyed as they were on the ground floor of the building, just close to the white fuel tanks as shown earlier on FRED's drawing.

We can be surprised that no mobile power generator could be available soon (I'm talking about these kind of things, like gas turbine generators: )

I heard an info at the beginning of the crisis that Tepco asked for ten of them... but found on the GE site that only three of them where available... in Florida! Ok i understand that total loss of power (including safety groups) was not a scenario conceived by Tepco and this perfectly demonstrates it...

An other subjet: can somebody give me a good explanation of why Tepco had to vent the H2 inside the buildings (in the top floor) instead of outside? This looks an odd way of doing it, considering that there was a risk of explosion. Why inside instead of outside? This looks strange to me and i find no analysis or answer on this point.

Joe Neubarth

So why are the pressure readings negative? Those are negative signs I see in front, right?

Gilles

concerning the release of volatile cesium, I found that
http://blogs.nature.com/news/thegrea...dioactive.html

with this comment

are 10 kg plausible ?

tadjik

Don't know why ...
The figures for the inside (I suppose) reactor are hardly understandable.
Below atmospheric pressure un all cases except reactor 1 (and negative for 2 3).

That's why I only read ther Dry well and Supression Chamber.
If anyone has a explanation (except instrumentation broken) ...

Joe Neubarth

My understanding is limited with respect to what they do, but I read somewhere that they vent steam from the primary inside of the building rather than to the open air. This supposedly is done to decrease the radiation released outside the building.

It looks to me that they did not know that they would be releasing hydrogen from the reactor plant. Hydrogen can come from breaking the bonds of the water molecule, and that could most likely happen in a scrammed reactor if the surface temperature of the fuel plates reached approximately 1000 degrees Fahrenheit. At some temperature in that range, the Zirconium cladding will oxidize with the Oxygen in the water molecule I thing the above is correct but will not be offended if corrected. I am not certain about the temperature needed for the Zirconium oxidation.

Borek

If I recall correctly venting inside of the building means lower chances of radioactive contaminants getting outside, hence the design.

Edit: beaten by Joe.