Video above: This is the source of the 4:30 pm time from Wikipedia. The video shows the explosion, after the fact. If you understand Japanese, would you please help out by translating the source of the time? This source is reporting 3:36 pm and the New York Times is reporting 3:40 pm. We will be going with the 3:36 pm chart, which puts Leo in the ascendant. The 3:36 pm time appears to be confirmed by a press release from the nuclear plant itself. Note, here is the latest from Karl Grossman, posted to his personal blog. A longtime scholar of nuclear power issues, he is able to explain the technical side of the situation.
News from the damaged Fukushima nuclear power plant has taken a turn for the worse overnight, as an explosion was reported at the plant at about 3:36 local time. The atomic reactor suffered the loss of its primary and backup cooling systems in yesterday’s earthquake, and was running on battery power as Japanese and American workers worked to install portable diesel generators to supply backup power.
The explosion at the plant, seen in the video above, obviously did damage — the question is whether the containment structure is intact. It does not look good.
Both pressure and radiation levels inside the plant were increasing through the day yesterday and overnight, with radiation being reported inside the control room of the plant at 1,000 times the normal level. Plant engineers were venting toxic steam, probably from the primary and secondary cooling loops, into the atmosphere in an attempt to keep the pressure down. Last night Rachel Maddow did a segment explaining the situation. It is worth watching if you want a clearer picture of how this type of nuclear plant works and which ways the situation could go.
But the explosion Saturday afternoon seems to indicate that their efforts failed; basically the world is left hoping that the 40-year-old nuclear device does not melt down. It is located just 240km from Tokyo, a city of more than 12 million — extremely close in terms of the potential for radiation to travel.