In 1950, the first commercial nuclear power plants were built. The public was promised a clean, resourceful form of energy, but how safe was and is nuclear power? Although there are fewer than 500 licensed nuclear power plants in the world, many nuclear accidents already endanger civilian lives. More serious accidents are not only likely, but inevitable (Fairchild 29). Nuclear energy may appear to be the ideal energy source for the future: however, it has many negative effects which can lead to very dangerous situations. Energy has always been one of humanity's fundamental concerns, just like food and shelter. He participates in all activities, from walking to operating even the most complicated equipment. Humanity has been faced with the challenge of meeting its energy needs without risking human health and the environment. The many types of energy are mechanical, thermal, chemical, electrical, radiant and atomic (Microsoft Encarta). In 1987, oil provided 32% of the world's energy. Coal comes next with 26%, followed by natural gas with 17%, biomass with 15% and nuclear energy with only 4% (Galperin 19). As our primary sources of energy become depleted, nations are turning to new sources to power our society. Nuclear power, the newest type of energy, was studied to see if it would be the most promising type of energy for the future. Surprisingly, nuclear power was discovered by chance. In 1896, French scientist Antoine-Henri Becquerel conducted an experiment with uranium salts and discovered that these salts emitted their own light when exposed to sunlight. Marie and Pierre Curie were fascinated by the possibilities of Becquerel's rays. The Curies discovered exactly what these rays were and then named the phenomenon radioactivity (Halacy 6). During World War II, many scientists from around the world came to the United States to work on reactors and nuclear weapons. Very successfully, they continued after World War II and focused more on nuclear power. Scientists immediately realized that nuclear power would be an excellent source of energy because of the amount of energy it released. Splitting an amount of uranium equal to one cent would produce as much energy as seven and a half tons of coal (Lilienthal 85). A nuclear power plant is where energy is formed during nuclear fission or fusion. Until now, however, only the power of fission has been controlled and used as energy. The nuclear power plant has many parts, including the reactor, generator, control room, cooling systems, and electrical, air, and water lines. The heart of the nuclear power plant is its reactor core, which contains a few hundred fuel assemblies. The reactor core is enclosed in a pressurized steel tank