NISA couldn't stop physics from working its way at Fukushima I Nuke Plant, so they did their best to hide it. And the reporters, usually not very much trained in physics not to mention any science at all, didn't know what to ask at the press conferences in the early days of the accidents and/or didn't understand the answer given by TEPCO or NISA.
Those few who did ask and did understand, and wrote about their speculation about the condition of the plant were branded as "fear-mongering liars" both by the government, the MSM who received tons of advertising money from the electric power companies who run nuke plants all over Japan, and also by a surprising number of ordinary Japanese, usually well-educated and therefore very trusting of the "official" explanations.
Anyway, the Nuclear and Industrial Safety Agency now says a huge amount of hydrogen was generated only a few hours after the fuel rods started to get exposed in the Reactors 1, 2 and 3.
Maybe they've finally read the entries in English Wikipedia about "corium".
And always remember this PM assistant who said "We knew it was meltdown from the beginning, we didn't feel like announcing it", and the MSM who let him get away with it.
(That assistant, Goshi Hosono, is visiting the US (the link is in Japanese) to "exchange" information with high-ranking US officials. He will then go to the UK and France, steadfast supporters and promoters of nuclear energy along with the US and Japan.)
From Yomiuri Shinbun (9:43PM JST 6/8/2011):
The Nuclear and Industrial Safety Agency (NISA) of the Ministry of Economy, Trade and Industry (METI) analyzed the data that suggests the maximum 1 ton of hydrogen gas was rapidly generated within few hours that the fuel rods in the Reactors 1, 2 and 3 started to get damaged at Fukushima I Nuclear Power Plant.
The majority of the hydrogen gas was generated within the first few hours, which probably led to the hydrogen explosions in the reactor buildings.
According to the NISA's analysis, the water level in the Reactor Pressure Vessel at Reactor 1 started to decline at about 5:00PM on March 11, 2 hours after the earthquake. The fuel rods started to get exposed, and one hour later zirconium in the cladding started to interact with water, generating hydrogen gas. Within few hours, most of 1 ton of hydrogen gas was generated.
Hydrogen gas started to get generated at about 8:00PM on March 14 in Reactor 2, and at about 10:00AM on March 13 in Reactor 3. In both cases, it took place within 2 hours after the fuel rods started to get exposed. The amount of hydrogen gas in Reactor 2 was 0.8 ton, and 1 ton in Reactor 3.