The APPR-1 is a pressurized water reactor having a low specific heat fuel and a water primary coolant. The primary coolant loop delivers heat from the reactor to the steam generator. The secondary water in the steam generator is converted to steam and then taken to the turbine to drive an electrical generator. The simulation of this system is broken down into three primary areas: the neutron kinetics in the reactor which are necessary to generate the primary power function, the heat transfer in the reactor, and the heat transfer in the steam generator.