Video of Explosion at Japanese Nuclear Reactor

There was an explosion at the Fukushima nuclear reactor:

NPR notes:

The good news at this hour, The Associated Press reports, is that a radiation leak at the plant "was decreasing despite fears of a meltdown ... officials said. Government spokesman Yukio Edano said the explosion destroyed the exterior walls of the building where the reactor is placed, but not the actual metal housing enveloping the reactor."

Still, the situation is serious. NPR's Jon Hamilton has been following what he says is the "last-ditch effort to protect the reactor's radioactive core," and said a short time ago on the NPR Newcast that:

"The reactor in Fukushima prefecture has had problems with its cooling system since the earthquake. Now it appears efforts to keep the system working have failed.

"A spokesman for the Japanese government said the reactor's core would be flooded with sea water and boric acid. The boric acid helps to suppress any lingering nuclear reaction. The spokesman also explained an explosion that destroyed a building at the Fukushima plant early this morning. He said efforts to add cooling water to the reactor core had resulted in the production of hydrogen gas. The gas built up inside the building and then exploded."

Nikkei reports:

The Nuclear and Industrial Safety Agency (NISA) said Saturday afternoon the explosion at the Fukushima No. 1 nuclear plant could only have been caused by a meltdown of the reactor core.

And Reuters writes:

On Saturday, an explosion blew off the roof and upper walls of the building housing the facility's No. 1 reactor, stirring alarm over a possible major radiation release, although the government later said the explosion had not affected the reactor's core vessel and that only a small amount of radiation had been released.