Fukushima. The accident sequence and important causes. Pt. 3/3

The immediate cause of the Fukushima Daiichi disaster was the earthquake that was stronger than the design basis of the NPP Fukushima. The earth quake has at least destroyed the external power supply for all six units of the power plant. It is not yet clear whether other damage has been caused in the different units. The subsequent tsunami was of dominant importance for the progress of the reactor accidents. The power plant had no appropriate protection against tsunamis of this fortitude. The connections between politics, regulatory authority and owner of the power plant did not allow an effective and independent surveillance of the activities in the power plant. The most important principles of reactor safety were not implemented in the NPP Fukushima (for instance: the heat removal from the condensation chambers was dependent on a single heat sink). The local infrastructure was not protected against severe damage from earth quakes or tsunamis, so that immediate mitigating actions were not possible.