Uh oh.. Nigrogen and radioactive steams escaping from the Containment Vessel (which they call "Primary Containment"; "Secondary Containment" being the building itself, which is already badly damaged in the case of the Reactor 1).
From Yomiuri Shinbun (1:37PM JST 4/11/2011):
TEPCO announced today that the pressure of the Containment Vessel of the Reactor 1 at Fukushima I Nuclear Power Plant has stopped rising above 1.95 atmospheric pressure; TEPCO has been injecting nitrogen in order to prevent a hydrogen explosion. TEPCO thinks that a significant amount of radioactive steam and nitrogen is escaping the Containment Vessel and into the surrounding area.
TEPCO has been injecting 28 cubic meters of nitrogen per hour since early hours of April 7. The pressure inside the Containment Vessel rose gradually from 1.56 atmospheric pressure on April 7 to 1.9 atmospheric pressure on April 9, but the pressure stopped rising at 1.95 atmospheric pressure on April 10.
About 1,000 cubic meters of steam and nitrogen may have been escaped, but there has been no significant change in radiation levels around the Plant.
The plan was to inject 6,000 cubic meters of nitrogen into the Reactor 1's Containment Vessel over 6 days, and raise the pressure from 1.5 atmospheric pressure to 2.5 atmospheric pressure. TEPCO thinks "the containment vessel's seal is compromised, and significant amount [of steam and nitrogen] is escaping." TEPCO will continue to inject nitrogen while trying to figure out what to do in order to avoid a hydrogen explosion.
The US's NRC didn't think the Containment Vessel of the Reactor 1 was broken, but that was March 26.
Earlier today, I was watching the separate press conferences of Nuclear and Industrial Safety Agency and TEPCO (which they did it roughly at the same time). What was interesting was a "doom and gloom" among the Internet audience of these press conferences that were presented live by independent journalists (yes there are such people now in Japan). Many of them were saying (tweeting) that there was something amiss in both press conferences, as if some huge SHTF event was coming soon.