Japanese authorities now reporting that about 6:14 a.m. (Tokyo) Tuesday, March 15, there was an explosion at the Daiichi Unit 2 [at right - before explosion] of the Fukushima Nuclear Station. This explosion was heard, not seen from the outside. The explosion reportedly did not blow off the roof/walls, as the explosions did at Units 1 and 3.
The explosion reportedly occurred near the containment area. Plant officials fear there may now be a crack in the reactor containment, which would allow more serious releases of radiation. A “pressure suppression pool,” the doughnut-shaped area at the bottom of the reactor vessel may have been damaged, which officials are describing as “serious.”
They are evacuating non-essential personnel around the plant. Release levels spiked to 965 micro-Sv/hour [translation unclear?] and then fell back, but remain at elevated levels. [Now reported to have reached 8,217 micro-SV/hour, before dropping.] Winds are reported from the NNW.
At the time of the explosion, about one half of the reactor core — about 2.7 meters — had become uncovered. According to one analyst, at some point, the entire core was exposed. Pressure reached 3 atmospheres, but has fallen back to 1.
These pressure and radiation readings suggest the reactor pressure vessel holding the core may have been breached.
There is also an inoperable value that would otherwise allow pressure releases. That’s preventing or limiting the ability to inject cooling water.
An official is describing the event on this live tv feed, with English translation.
Radiation levels around the damaged reactors is rising to serious levels.
The French are preparing to evacuate their Tokyo embassy.
From a former worker in the nuclear energy industry:
From this point on, onsite personnel will become very ill. Many will die. If they are forced to stop working or if they fail to keep control, we could get three or four large steam explosions, dispersing many tons of radioactive material high into the air.