The biggest mistake...
The biggest mistake in all this is that as soon as an emergency situation arose, the Japanese Nuclear Safety Agency (or whatever its called in Japan) should have taken complete control of the situation and they should have been the only ones making press releases.
TEPCO naturally are going to try and protect their asses, and so cant be trusted to be 100% honest (especially with their past history). So this situation should be being completely managed by the government (or even more preferably an independent) safety agency. At least then we would get accurate and (relatively) honest reports coming out.
Additionally TEPCO need to seriously sack there public relations people! In this sort of situation what you want to give is regular reports (every 2 hours minimum), providing accurate factual information. A report saying " Radiation at plant of ****mS detected. Radiation at 10km from plant of ****mS detected. These values can have this effect on people. Plant A is *** hours from complete shut down. Plant B is *** from shut down. Plant C, etc....". Just give the facts, explain that when things happen (the explosions for example) they were expected, and what effects they will have. Thats what the public want - The Facts.
At the moment, the long silences, the sort of half information and banal platitudes about safety and that "all is well" that are being released are having the exact opposite effects to reassuring the public.
I'm a bloody engineer and it seems i know more about public relations then the PR people TEPCO are paying a lot of money too!