The nuclear chain reaction in the reactor core produces energy in the form of ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem, as the fission fragments slow ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem and dissipate their kinetic energy in the fuel. This heat must be removed efficiently and at the same rate it is being generated in order to prevent ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem of the core and to transport the energy outside the core, where it can be converted to a convenient form for further utilization. The energy transferred to the coolant, as it flows ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem the fuel element, is stored in it in the form of sensible heat and pressure and is called the enthalpy of the fluid. In an electric power plant, the energy stored in the fuel is further converted to kinetic ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem through a device called a prime mover which, in the case of nuclear reactors, is predominantly a steam turbine. Another conversion takes place in the electric generator, where kinetic energy is converted into electric ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem as the final energy form to be distributed to the consumers through the power grid and distribution system.
Because heat removal must be accomplished as efficiently ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem possible, considerable attention must be given to fluid-flow and hydrodynamic characteristics of the system. The heat capacity and thermal conductivity of the fluid at the temperature of operation have a fundamental effect upon the design of the reactor ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem. The heat capacity ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem the mass flow of the coolant required. The fluid properties (thermal conductivity, viscosity, density, and specific heat) are important in determining the surface area required for the fuel—in particular, the number and arrangement of the ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem elements. These factors combine to establish the pumping characteristics of the system because the pressure drop and coolant temperature rise in the ascoredeterminesdownenergyfuelheatoverheatingpastpowersystem are directly related.