The issues of primary causes for severe accidents Fukushima-Daiichi

The review of the primary causes for severe accidents on NPP Fukushima-Daiichi using well-known data from nuclear safety regulatory state organizations of Great Britain, USA and Japan including data from operator TEPCO (Tokyo Electric Power Company) are presented. It is shown that the main causes of severe accidents and the devastating explosions were fundamental drawbacks of early BWR projects in overcoming consequences of of extreme natural events, as well as the lack of trained personnel to manage accidents which has relatively low probability. (authors)