Japan Times on Melt Through: 'Molten ‘lava’ melted bottom of containment vessel,' says nuclear engineer given access by top official — Huge amounts of fission materials released into environment
Yomiuri: “The worst-case scenario is a China syndrome” [...] A China syndrome refers to a situation in which nuclear fuel in a reactor melts and goes through a containment vessel -Masao Yoshida, former chief of the Fukushima Daiichi plant
Title: Fukushima: Probability theory is unsafe
Source: The Japan Times Online
Author: Kenichi Ohmae, Nuclear engineer
Date: Apr. 18, 2012
Emphasis Added
[...] As a nuclear core designer and someone who earned a Ph.D. from the Massachusetts Institute of Technology in nuclear engineering, I volunteered to look into the situation at Fukushima No. 1 in June of 2011. Mr. Goushi Hosono, minister of nuclear power and environment, personally gave me access to the information and personnel who were directly involved in the containment operations of the postdisaster nuclear plants. After three months of investigation, I analyzed and wrote a long report detailing minute by minute how the nuclear reactors were actually disabled (pr.bbt757.com/eng/)
Here are the highlights of my findings:
1. Three of the six reactors of Fukushima No. 1 had a complete core meltdown a few days after the tsunami hit. The molten fuel penetrated not only through the bottom of the thick pressure vessel, but also poked holes at the bottom of the containment vessel, thus releasing fission materials into the environment. The meltdown itself started at 11p.m. on the day of the tsunami, March 11, 2011.
2. As expected, the meltdown caused the fuel cladding material, zircaloy (zirconium alloy), to react with vapor and to create large quantities of hydrogen and zirconium oxide, which caused the catastrophic hydrogen explosion that blew out three reactor buildings. The hydrogen explosion took place on March 12, 14 and 15. The Japanese Government did not admit to the meltdown until three months later, nor did they admit to the damage to the containment vessels until a half year later. Our government tried to hide this important information for some reason, though judging from the amount of fission material released and from the size of the hydrogen explosion, the meltdown of the entire core was undeniable for anyone who has studied reactor engineering. [...]
Many long-held myths have been broken as a result of the Fukushima No. 1 meltdown.
As the molten fuel made its way through the pressure vessel and the molten “lava” melted the bottom of the containment vessel, it released huge amounts of fission gasses and particles to the air and water.
The assumed role of the containment vessel proved to be faulty against this type of melt through. [...]
The Lesson?
The Japanese government’s official explanation of the Fukushima disaster focuses only on the inability of anyone to predict an extreme natural disaster. Because of this focus, the rest of the world is not taking notice of the important lessons we need to understand to make the world a safer place. Many countries rely on nuclear energy, and yet these same countries assume that because they do not have to worry about earthquakes and tsunamis, what happened in Japan on March 11, 2011 does not apply to them. This could become a fatal mistake.
Read the report here
It appears Hosono is aware of this analysis: Top Japan official: Very strong possibility there is nuclear fuel outside containment vessel (VIDEO)