Power reactors are typically found in nuclear power plants. Dedicated to generating heat mainly for electricity production, they are worked in more than 30 countries around the world. Their lesser uses are drinking water or district water production. In smaller units, they also power ships. In the U.S currently these reactors provide an estimated of 20 % of electrical energy. In these reactors, the fission of heavy atomic nuclei, the most used of which is uranium-235, produces heat changing to a fluid which acts as a coolant. Fission is the process in which heavy nucleus divides to form smaller nuclei of intermediate mass and one or more neutrons. In the fission process, bond energy is released and this becomes as the kinetic energy of the fission products generated and that of the neutrons being released, and then the kinetic energy turns into heat energy. .
There are many different types of power reactors. Three types are the main features of them. The first type is, Light Water Reactors. These reactors are the most important of them. Most of the reactors are Light water Reactors because they use light water (H2O) as a moderator. The fission reactions are highly exothermic. The neutrons produced usually move at high velocities. They must be slowed down before used, so scientists use moderators that are substances that can reduce kinetic energy of neutrons. Second is, Heavy Water Reactors. They uses heavy water (D2O). Fewer neutrons are absorbed, it is more efficient, and does not require enriched uranium. And finally, Breeder Reactors. Breeder Reactor uses uranium fuel, but produces more fissionable materials than it uses. The U.S does not have any of these reactors, just a few countries like France and Russia have been built these breeder reactors. .
It is important that the U.S Department of Energy is responsible for the installation of the elimination for the long term management of used uranium fuel from America's nuclear power plants, but the federal government, does not have a reasonable system for the management of utilized nuclear fuel from nuclear energy facilities and high level radioactive waste from the government's defense and research activities.