Three Letters about the Extraordinarily Severe Nuclear Accident at Fukushima Daiichi Nuclear Power Plant after the March 11 Earthquake and Tsunami in Japan

Three letters were presented at different stages for the extraordinarily severe nuclear accident at Fukushima Nuclear Power Plant after the March 11 earthquake and tsunami in Japan.The accident's evolutionary trend of the Fukushima nuclear power plant was primarily investigated in the first letter.Some problems about nuclear safety inspections in china were considered and some natural events and contrived incidents which may affect nuclear power plant's safety were described in the second letter. Some topics about geology and earthquake were posed in the third letter.