At the end of the 19th century, scientists discovered the radioactivity of the atomic nucleus. In 1916, Einstein revealed the extremely important natural law in the relationship between mass and energy - E = MC2, where m is the change of mass（ Δ m) , C is the speed of light - 300000 kilometers per second. Therefore, C2 in the formula becomes a surprisingly large quantity! This relationship shows that a small amount of matter can be transformed into huge energy.
The research of nuclear physics shows that the mass of nuclear fission products is usually less than that of the materials before fission, and the change of this mass Δ M (mass loss) will be converted into energy and released, which is nuclear energy. The energy generated by nuclear reaction can be used to make atomic bombs or controllable nuclear reactors to drive generators to generate electricity, which is commonly known as "nuclear power technology".
Nuclear power is a clean, safe, economic and efficient energy. Compared with coal-fired power, although the one-time input of nuclear power is large, its economy can be reflected from the comparison of long-term input and output: the cost of coal-fired power in France is 1.75 times that of nuclear power, 1.64 times in Germany, 1.51 times in Japan and 1.7 times in South Korea. The cost of nuclear power in the United States was lower than that of coal-fired power as early as 1962. Therefore, nuclear power is the only renewable energy with lower cost than coal power or even hydropower. Many countries have built nuclear power plants. By the end of 2011, there were 434 nuclear power units in operation worldwide with a net installed capacity of 372760 MW, including 15 nuclear power units in operation in China with a net installed capacity of 11881 MW. It can be said that nuclear power, together with hydropower and thermal power, has become the three pillars supporting the world's power supply.
However, the disposal of nuclear waste and the occurrence of nuclear accidents will cause great environmental damage and casualties, which is the most worrying side of nuclear power technology.
On April 26, 1986, the Chernobyl nuclear power plant of the Soviet Union had a violent explosion and a fire at the same time. A large amount of radioactive substances in the reactor leaked out, and the clouds with radioactive substances dispersed with the wind. Even the radiation dose in the coastal area of Eastern Sweden exceeded the normal value by more than 100 times. The nuclear accident polluted the water source in Ukraine, and the agriculture and animal husbandry of the Soviet Union and its surrounding countries were greatly affected, with a comprehensive loss of hundreds of billions of dollars. It is reported that the nuclear accident caused 33 deaths, more than 300 people were seriously exposed to radiation, more people were exposed to varying degrees of radiation pollution, and more than 280000 people were evacuated outside the radiation area.
On March 11, 2011, a major earthquake occurred in the Northeast sea area of Japan, triggering a tsunami, and a serious nuclear leak occurred in the Fukushima nuclear power unit. One year after the earthquake, the nuclear radiation intensity in the area near the nuclear power plant is still as high as 470 millisieverts per year, much higher than the safe value. These nuclear contaminated areas have been designated as permanent no residential areas.
The nuclear power plant accident has exposed that there are still many problems in nuclear power technology, management and site selection. In particular, nuclear power has terrible "lethality" to mankind and the possibility of serious pollution to the environment.