I have a trip to Tokyo and southern Japan scheduled 3/25, so I've been following this event closely. The BBC website has been my main source of info:
http://www.bbc.co.uk/news/world-middle-east-12307698
Latest from BBC:
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22:12: Some clarification: It is the number three reactor at the Fukushima No. 1 plant where officials have just announced that the cooling system has failed. This morning's blast took place at the number one reactor at the same plant. "All the functions to keep cooling water levels in No. 3 reactor have failed at the Fukushima No. 1 plant," a spokesman for the operator said.
Also, residents in Japan are reporting long aftershocks, some lasting 2 mins in length.