Speaking of hydrogen, TEPCO just announced it detected hydrogen at 2 locations inside the pipe that leads to the Containment Vessel of Reactor 1.
TEPCO's handout for the press on September 23 says (not their exact words):
- TEPCO was planning to cut the pipe for the spray system to install a gas management system for the Reactor 1 Containment Vessel;
- Before cutting, they measured hydrogen inside the pipe to be safe. More than 10,000 ppm hydrogen was detected;
- They won't cut the pipe until the safety is assured.
10,000 ppm is equivalent to 1%. As we know from the previous post, if the hydrogen density is more than 4% in the air, a hydrogen explosion could happen.
The company assures us, according to Yomiuri Shinbun, that the existence of hydrogen in the pipe had been expected, although the density was higher than expected, and that there would be no danger of an explosion.
So if TEPCO says "more than 10,000 ppm", it either means they didn't bring the instrument that could measure higher than 10,000 ppm, or they don't want you to know how high.
I wouldn't be surprised at either. We haven't heard anything more about the location near the exhaust stack for Reactors 1 and 2 that measured "more than 10 sieverts/hour". Was it 11 sieverts? 20 sieverts? 50 sieverts?
It could be the same here in the pipe. "More than 10,000 ppm" could be 11,000 ppm, 20,000 ppm, or 40,000 ppm.
Yomiuri also mentions the reassuring word from TEPCO:
TEPCO has been injecting nitrogen into the Containment Vessel since April, and it is considered there is hardly any oxygen that would be required for an explosion, according to the company. TEPCO says there is no immediate danger of explosion.
Here we go again, "no immediate" danger. (Calling Mr. Edano...) That word makes me nervous.
Besides, the very fact that the water being injected into the Reactor Pressure Vessel somehow ends up in the basement means the Containment Vessel is leaking badly. Nitrogen that's been injected since April is leaking, as the pressure doesn't go up at all. How would they know that there is hardly any hydrogen left? It could easily leak in from outside, couldn't it?