Reactor

• In a nuclear power plant, radioactive material is kept in a concrete-and-steel housing called a reactor. A containment building surrounds the reactor; it shields the workers and public from heat and radiation. In the reactor, rods of radioactive metal such as uranium or plutonium are organized in a grid. Neutrons given off by radioactive decay drive a chain reaction among the atoms in the rods. The radioactivity is carefully monitored; several mechanisms in the reactor allow the reaction to be adjusted to meet changing circumstances. The reaction gets very hot.
  
  

Steam

• Heat from the nuclear reaction boils water to make steam and drive a turbine. Steam-driven turbines are well-known and proven technology, also used in gas and coal-fired power plants. The steam cools back to water in a cooling tower and returns to the boiler, making a closed loop.
  
  

Generator

• The turbine runs an electric generator, producing electricity. The same basic technology is used in fossil-fuel power plants. Safety and reliability is enhanced, because the turbines and generators for different plants are similar.
  
  

Battery

• An atomic battery also uses nuclear energy to make electricity. Radioactive decay and heat can be used to produce a small DC current. While a nuclear power plant replaces its radioactive material on a regular schedule, a nuclear battery is a sealed unit meant to last for many years. They're used to power deep-space probes; solar panels don't work at distances far from the sun. Atomic batteries are also used for heart pacemakers, providing power for years before needing replacement.