Given article is focused on the geologic causes of the earthquake of 11 March 2011 in Japan, which became the largest earthquake of all occurred on the Earth over the past 100 years. It caused a tsunami wave of 10 meters altitude, which has claimed the vast majority of lives. The cooling system of reactors at Fukushima-1 has got damaged resulting in leakage of radioactive isotopes into the atmosphere and the environment. Japanese engineers and managers of the company operator Tokyo Electric Power Co are also responsible for the accident and its consequences. On the example of the accident at Fukushima-1 are considered short and long-term (first decades) negative factors that affect the environment. Preventive measures to prevent the negative effects of radiation from nuclear power plants are listed. Conditions and perspectives of development of nuclear energy in Japan after the accident at Fukushima-1 are considered.