Hydrogen buildup at Fukushima? What does it mean & why does it happen? from Fairewinds Associates on Vimeo.

TEPCO recently discovered hydrogen build-ups within the containment buildings in Fukushima Units 1, 2 and 3. Could there be another explosion, and if so how? Fairewinds conducts a laboratory experiment to show that if oxygen is present with hydrogen in a nuclear power containment, a deflagration explosion might occur.

Video transcript:

Hi, I'm Arnie Gundersen from Fairewinds...

A little change of venue today. There have been some reports in the press about a hydrogen buildup inside the containment at Fukushima and along with that hydrogen gas, there is a discussion that there are some radioactive isotopes that are in the containment that could only be caused by a fission.

Well I thought I would simulate today what a hydrogen buildup inside a containment looks like. Now we are going to use this bottle as a containment. And I am going to generate hydrogen gas in this little flask. Those nails are coated with zinc and I will add some acid to the zinc, and we will create hydrogen gas out this hose. Put the hose in the bottom of the bottle, and hydrogen being lighter than air, is going to push all of the gas out of this bottle and we will be left with a bottle full of hydrogen. All right, let us see what happens. This is something you should not try at home. I am wearing gloves and we have got a fire extinguisher in the corner as well as bountiful water, just in case. Again, do not try this at home. Here is our beaker and this is muriatic acid. And those bubbles are hydrogen gas bubbles that are filling this containment, this bottle, with hydrogen. Now we are going to wait a little while here for this bottle to completely fill. Again, hydrogen is lighter than air, so it is going to float to the top. And then it is going to gradually, gradually push all of the air out of this container.

Now we have waited about 4 or 5 minutes and this bottle should be filled with hydrogen gas. All those bubbles ran out that hose and filled this bottle with hydrogen gas. I am going to take the hose out and set the acid aside. Because the next part of this lab is inside the bottle.

Hydrogen gas is lighter than air. So we put it in the bottom, but there is no place for it to go at the top, so it is going to stay in there. It is not going to leak out. Now I have put a little hole in the top of this bottle and I am going to light it with a match. Now what is going to happen is that you are going to be seeing a little tiny flame up here and that is the hydrogen gas escaping. It is barely visible and I will try to enhance it in a minute.

Now there is a little flame at the top of this, it is made of hydrogen gas, pure hydrogen gas. You can see I just lit this. You notice the bottle is NOT burning. It is just the very tippy, tippy top of this. That is hydrogen mixing with the oxygen in air forming that flame at the very top of this bottle.

[sound decreasing in pitch, then the sound of an explosion]

Well, that is a hydrogen deflagration. That is the smaller of the two shock waves. That is what happened inside Unit 1. When you get oxygen coming in and hydrogen in just the right amount, 2:1, they combine to form water vapour and they create a lot of heat and an explosion. Now what is TEPCO doing to avoid this? The containment is leaking. We know the containment is leaking. Well, instead of allowing oxygen to leak in, they keep adding and adding and adding nitrogen inside this vessel, so that hydrogen is at the top, but they are not allowing the oxygen to get in because they continually add nitrogen to the vessel.

Nitrogen is inert. So as long as the inert nitrogen and the hydrogen exist inside the containment vessel, then everything is going to be fine. The gasses from our experiment were generated chemically, but of course, in the nuclear reactors, the chain reaction and the radioactive decay, creates hydrogen gas. So that part of the lab is different, but the containment is just the same. It is just that TEPCO's containment is a couple of million times bigger than my soda bottle...