The role of nuclear heat sources in district heating systems in the electric power distribution network

Nuclear power and heating plants are classified in categories according to their utilization in the power and heat system considering that (a) the nuclear power and heating plant is mainly designed for heat supply for the district heating system while the remainder of its thermal output is supplied in the form of electric power, (b) the plant only provides the basic heat supply, (c) such plant is operated mainly for the purpose of the electric power distribution system. A hypothetical district heating system derived from the actual system is described as an example. For this hypothetical system, heat is supplied by a nuclear power and heating plant, conventional power and heat plant I, conventional power and heat plant II, and a conventional heating plant. The nuclear power and heating plant is equipped with one WWER-440 pressurized water reactor with a thermal output of 1,375 MW and a pressure of 4.61 MPa. Also given is the equipment of both conventional power and heating plants as are the diagram of heat supply and electric outputs. The maximum thermal outputs of the sources applicable for heat supply and the electric power generation for the maximum load of the distribution system are shown for variants (a) and (b). An increase by 56,066 MWh/y was found for variant (b) while the amount of fuel spent in conventional sources is higher for variant (b) by less than 11% and the specific fuel consumption in conventional plants decreased by almost 17%. An informative calculation was also carried out of the utilization of natural heat storage in the hot-water supply of the nuclear power and heating plant provided water temperature was 150/70 degC at normal operation without storage and 175/70 degC with storage. It was found that natural storage may not considerably affect the nuclear power and heat plant output. (J.P.)