Wednesday, September 28, 2011

Fuku I Hydrogen Gas Update: It Was 63% Concentration

and no need to worry, TEPCO will take care of it.

TEPCO also says since there is no oxygen in the pipe that leads to the Reactor 1 Containment Vessel, there is NO DANGER of explosion.

(Uh huh. "There is no danger of explosion" was what they said to the fire department and the Self Defense Force right before Reactor 1 blew up, and then before Reactor 3 blew up.)

From Yomiuri Shinbun (9/28/2011):


TEPCO announced on September 28 that the concentration of hydrogen gas in the pipe that leads to the Containment Vessel of Reactor 1 at Fukushima I Nuclear Power Plant was 63%.


TEPCO says there is no danger of explosion because no oxygen was detected in the pipe. The company will inject nitrogen in the pipe on September 29 to expel hydrogen.


The high concentration of hydrogen was found in the pipe that was to be used as part of the filtering system to suppress the leak of radioactive materials in the Containment Vessel. TEPCO will measure the levels of hydrogen gas in the similar pipes in Reactors 2 and 3.


It is considered that hydrogen gas was generated when the nuclear fuel was heated to high temperature right after the accident and the cladding and water reacted. If there are more than 4% hydrogen and more than 5% oxygen in the atmosphere, the chance of explosion increases. It is possible that there is hydrogen gas in the upper part of the Containment Vessel and in other pipes. The company says it will take measures to address hydrogen gas before proceeding on any work from now on.

Looking at TEPCO's handout for the press on September 28 (Japanese only for now), all they will do is to try to expel hydrogen in the pipe alone by injecting nitrogen from the far end of the pipe. They must be operating on the assumption that all the hydrogen in the pipe is from the initial zirconium cladding and water interaction, not the recent or on-going radiolysis, and once the hydrogen currently in the pipe is expelled, that will be the end of the story.

The idea seems to be that as long as the "MO11" valve is closed off, they can just purge hydrogen from the pipe and not worry about any "fresh supply" if any from the Containment Vessel, and they are free to cut the pipe for their gas management system.

There's a word for that in Japanese, "ba-atari-teki", and it can be translated as "ad hoc". The word seems to describe how TEPCO has been dealing with the crisis very well. (Remember the bath salt as tracer?)


Atomfritz said...

Duh... we seem far from an end of the nuclear crisis.

Hydrogen is the lightest of all gases.

So we can expect that the upper area of the reactor vessel and the containment are filled with steam and a mixture of radiolysis gases (mainly hydrogen and an yet unkown quantity of oxygen).

As long Tepco manages to maintain overpressure in the containment/reactor compartment there will be not much oxygen flow into there.

But, the "supply" of Zirconium cladding in the reactors will eventually die out and then there will be nothing that absorbs the hydrogen.

Too bad they don't measure the composition of gases in the steam that the reactors "fart out" regularly at the upper reactor lids.
Remember, we have to assume that the gas in the tubes had much time to settle into layers. So we cannot deduce from the composition of the gas in the pipes that the gas composition in the containment is identical. Even more important, we cannot deduce that there is no oxygen there as Tepco tries to suggest.

At least Tepco is aware now that every action they perform there has to be verified that it does not lead to the reactors/their containments blowing off.

If they make any mistake there, the consequence of a hydrogen explosion could be the reactor lids popping off violently, shooting out the remaining reactor contents high into the air like mortars.
Such happening would change the whole situation fundamentally.

Atomfritz said...

Arf! No edit function...

I have to correct what I wrote:
...there will be nothing that absorbs the OXYGEN (NOT THE HYDROGEN).

Slap me if you like.

Anonymous said...

Good News TEPCO has achieved cold shutdown before end of September, 3 months ahead of schedule. Japan is finally nof.
“TEPCO says temperature at the base of Nos. 1-3 reactors at Fukushima N-plant are below 100 C, a key condition for achieving “cold shutdown.” -The Daily Yomiuri

Anonymous said...

Looks like someone has been brainwashed into the <100 degrees = cold shutdown school of thought.

Cold shutdown means that the fuel is only generating a small amount of decay heat. When the water surrounding the reactor is less than 100 degrees Celsius, that only means that the water is no longer boiling. It is a gross mis-characterization to state that just because the water is at 99 degrees C that therefore there is no further fission (and thus releases) taking place.

Unfortunately, it is not possible to stop melted fuel from fissioning. True, pumping water in helps to remove the heat that is being generated. But as long as the fission process continues, fission products will be created and released. The best that can be done is to try to contain the releases (which is not being done, but attempted by means of the tent).

Anonymous said...

Here's a sharp unseen turn on TEPCO's fantasy road map. It can be filed away along with the undetermined hotspots found around the site that will be sure to hinder work as they delve into the facility looking for loose fuel. The fact that they are moving evacuees back into the area even after this revelation is criminal. Most people are going to let TEPCO beg off on an act of god for the initial accident but now that they know they are still deep in the midst of of the disaster they have no excuse for exposing the population to further risk. The Japanese are redefining the term "Cold Shutdown" and the world nuclear establishment is more that happy to promote this myth through their IAEA mouthpieces. The Japanese are still guessing/hoping where the fuel actually is with faulty gauges and sensors 7+ months after the accident. How can you claim any sort of control in the situation when you can't even reliably locate the source of the problem and quantify it?

As far as I'm concerned you don't have true cold shutdown until you can locate and account for at least 99% of the fuel then sequester it in a closed cooling loop system. This cooling loop also has to be truly "closed" it can't use a ruptured building basement for a sump or supplement water from outside the system. Nobody in the world nuclear club is going to hold Japan to any standard because they may be in the same boat the next time and they want the same leniency.

Anonymous said...

When are the TEPCO higher-ups going to do the honorable thing by committing seppuku?

Anonymous said...

"When are the TEPCO higher-ups going to do the honorable thing by committing seppuku?"
they R resetting up shop in Vietmonoï

Anonymous said...

What do you mean its not possible to stop melted fuel from fissioning? Of course its possible. I think you are mistaking fission for decay of fission products.

jmdesp said...

Generation of hydrogen requires a heat of several hundred degrees. Cold shutdown indeed means that no new hydrogen is being generated.

We have to hope however Tepco has a decent knowledge of what gazes are present in which quantity, but the fact they had no idea 63% of hydrogen could be present in that pipe give a bad idea about their ability to do that.

One important thing about cold shutdown : If the temperature is below 100°C, then the water doesn't boil, then fissile matterials that are water soluble (this means iode and cesium) are *not* going away together with the water vapors, and the reactor stops emitting further radioactive isotopes in the atmosphere (this means direct leaking of water is left as the only canal of emission to the outside world).
It is a significant positive outcome.
Even if it'd be better to have a temperature of water below 100°C in a more significant way, as there's still some water vapor production at 99°C.

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