The paper deals with the evaluation of the Fukushima-Daiichi Nuclear Power Plant (NPP) accident in Units 1 to 4: an attempt is made to discuss the scenario within a technological framework, considering precursory documented regulations and predictable system performance. An outline is given at first of the NPP layout and of the sequence of major events. Then, plausible time evolutions of relevant quantities in the different Units, is inferred based on results from the application of numerical codes. Scenarios happening in the primary circuit and containment (three Units involved) are distinguished from scenarios in spent fuel pool (four Units involved). Radiological releases to the environment and doses are approximately estimated. The event is originated by a natural catastrophe with almost simultaneous occurrence of earthquake and tsunami. These caused heavy destruction in a region in Japan much wider than the land around the NPP which was affected by the nuclear contamination. Key outcome from the work is the demonstration of strength for nuclear technology; looking at the past, misleading Probabilistic Safety Assessment (PSA) data and inadequacy in licensing processes have been found. Looking into the future keywords are Emergency Rescue Team (ERT), Enhanced Human Performance (EHP), and Robotics in Nuclear Safety and Security (RNSS). 1. Introduction On March 11, 2011 a magnitude 9.0 (Richter scale) destructive earthquake occurred in the north-east coast of Japan, close to the city of Sendai. The earthquake was followed by an equally devastating tsunami with waves as high as six meters entering a few miles into the land. Thousands of square kilometers of territory were affected, a few percent of the Japan islands surface. Whatever man-made installation like roads, factories, buildings, and dams was destroyed or severely damaged. The death toll accounted for around 30 thousands, that is, more than 2/10000 of the Japanese population. Several Nuclear Power Plants (NPPs) for the electricity production were (and are) in the affected area, including Onagawa (3 Units), Tokai-2 (1 Unit), Fukushima Daiichi (6 Units), and Fukushima Daini (4 Units). At a larger distance, there are the Kashiwazaki Kariwa (7 Units) and the Tohoku (1 Unit) NPPs. All Nuclear Power Plants safely responded to the earthquake and to the tsunami (where concerned) solicitations, including the NPP closest to the epicenter that is, Onagawa, with the noticeable exception of four over six Units of the Fukushima Daiichi installation. Namely, the nuclear accidents in the Units 1 to 4 of
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