The history of supplying heat energy by nuclear power, in addition to generating electricity, began with the Swedish prototype nuclear reactor Agesta in the 1960’s. It was the first civil nuclear power plant in the world that produced both heat and electricity. Subsequently, countries like Russia, Bulgaria, Switzerland and Romania also participated in the development of heat supply system with nuclear power. Heat-electricity co-generation is presently the most common means of nuclear-power heat production, with about 60 reactor units that are mainly located in eastern Europe which represent around 14% of operating reactor units in the world.

A nuclear power plant makes use of reactor heat to generate steam to drive a turbine that turns a generator to produce electricity. Similar to a coal-fired power plant, the nuclear power plant may use the steam from the turbine or condense the steam leaving the turbine in a condenser, to heat up a hot water circuit for industrial process, seawater desalination or, more commonly, providing heat to the nearby community that may be over 100 km away from the plant. In a nuclear power plant, roughly 40% of the steam is utilised in producing electricity. Using co-generation may increase steam utilisation to around 60%. This higher utilization rate enhances energy efficiency and improves the environment, due to the absence of emissions of CO₂ or other gaseous pollutants that come from the use of fossil fuels, especially coal, for heat production in such regions as northern China which suffers from air pollution due to heavy coal use for winter heating.

Potential egress of radioactivity from the reactor is prevented by installing multiple intermediate hot water circuits between the plant and the user. An intermediate circuit may operate at a higher pressure than the one upstream to inhibit any downstream leakage, and radiation detection is in place to assure proper operation. 

With the need to drive for a zero-carbon economy, more widespread use of nuclear co-generation will help address some of the challenging energy demands to decarbonise in heating, desalination and transportation.

This article is contributed by Ir Prof Ken C N Cheung with the coordination of the Nuclear Division.