ABSTRACT
A nuclear reactor converts atomic energy into heat. A chain reaction from uranium U-235 pellets in the fuel rods is controlled to a steady-state rate of heat production with control rods made of a neutron-absorbing material. Source rods containing neutron sources are used to initiate startup of the reactor. Very high velocity neutrons are slowed in the moderator, converting their kinetic energy into heat. At full extension the adjustable control rods allow just enough free neutrons for the heat production needed to supply thermal energy utilized to drive the steam turbine at full load. In US nuclear power plants the water circulated through the reactor serves both as moderator and coolant. The pressurized water reactor (PWR) system has a highly pressurized primary loop to prevent boiling in the reactor, which is hermetically separated from the secondary loop. The feed water and auxiliary feed water pumps of both PWR and boiling water reactor (BWR) systems are among the most critical safety-related pumps in a nuclear power plant.
