Nuclear District Heating, Climate and the Environment

According to the Intergovernmental Panel on Climate Change (IPCC), limiting the adverse effects of global warming to a level tolerable for biodiversity and human well-being requires stopping the average increase in the Earth’s temperature to approximately 1.5 degrees. To achieve this goal, the net global greenhouse gas emissions must be brought to zero by the middle of this century. Such reductions are not possible without a comprehensive restructuring of the entire energy system.

Decarbonization of heat is more challenging compared to electricity

The vast majority of greenhouse gas emissions originate from the energy sector, which is the largest consumer of fossil fuels. So far, the most prominent actions for reducing the emissions have been targeted to electricity production. Replacing coal or natural gas-fired power plants with low-carbon production can reduce the emissions but does not solve the entire problem. This is because most fossil fuels are consumed in other segments of the energy sector: transportation, industry, and heating.

In countries with a cold winter climate, a significant amount of energy is used for heating homes and commercial, industrial, and public buildings. The available means for reducing the emissions from heat production are also more limited compared to electricity. Fossil heating fuels can be replaced with renewable bioenergy, but the large-scale utilization of growing wind power capacity, for example, would require more extensive changes in heating technology and energy systems.

Restructuring of heavy industry and transportation is expected to significantly increase the demand of both biomass and low-carbon electricity. These applications are subject to the same emission reduction targets as heating, and practically competing of the same limited resources.

District heating is commonly used in Europe

Electricity and heat also differ in terms of how the energy is distributed to the customer. Electricity can be transferred thousands of kilometers using power grids that extend across national borders. Heat, on the other hand, is both produced and consumed locally. District heating represents a centralized form of production, where heat is distributed to customers via hot water flowing in underground pipes. The distribution networks are typically limited to cities and local communities.

There are some 3,500 district heating networks throughout Europe, serving a total of 60 million people. 75% of the production is covered by fossil fuels, which need to be replaced by cleaner alternatives. Most of the European networks are located in the Nordic countries, the Baltics and Eastern Central Europe. In addition to climate goals, several countries are looking for options to reduce dependence on natural gas to improve their security of energy supply.

Nuclear energy is suitable for low-carbon heat production

Conventional nuclear power plants are large production units, but the size of the plant can be easily scaled down. The output from a district heating plant consisting of two LDR-50 reactor units would be sufficient for the heating needs of a small or medium-sized European city. In larger cities the heating plants could be comprised of four to six units.

A nuclear power plant does not produce any direct greenhouse gas emissions during its operation. Energy and fossil fuels are needed, however, for the construction, operation, maintenance and decommissioning of the plants, as well as uranium mining, enrichment, fuel fabrication and final disposal of spent fuel. These life cycle emissions must be counted in the carbon footprint of nuclear energy production.

Comprehensive life cycle analyses have been carried out for traditional electricity-producing nuclear power plants. According to estimates from IPCC, the carbon footprint of nuclear electricity is comparable to hydro-, solar and wind power. The same conclusion can be found in a report from the United Nations Economic Commission for Europe, published in 2021, in which also other adverse environmental effects of nuclear energy were found to be small.

Similar detailed analyses have not yet been carried out for nuclear-based district heating. Since the fuel cycle of the LDR-50 reactor does not significantly differ from electricity-producing plants, the carbon footprint of the production can be estimated to be of the same order in magnitude.

High energy content of uranium guarantees security of supply

Nuclear fuel is made of uranium, which has a very high energy content. The reactor is run with one fuel loading for the duration of the entire operating cycle, after which some of the fuel assemblies in the core are replaced with new ones. The cycle length of LDR-50 is around two years. Fuel assemblies to be used for the following cycles can be stored on site, which ensures self-sufficient heat production for several years.

The production of nuclear fuel is an international business, which means that the availability is not dependent on any single vendor. The largest producers of natural uranium are Kazakhstan, Australia, Namibia and Canada. The following stages in the supply chain are uranium conversion and enrichment, where Russia had a relatively large market share before the war in Ukraine. However, the situation is changing as western suppliers are increasing their production capacity. Fuel assemblies loaded into the reactor core are manufactured in, for example, USA, South Korea, France, Great Britain, Spain and Sweden.

Video of the nuclear fuel used in LDR-50:

 

Final disposal is part of the nuclear fuel cycle

After fuel assemblies are discharged from the reactor core, they become high-active nuclear waste, which must be isolated from the living environment. Spent fuel assemblies are cooled in the reactor pool for several years, after which they are transported to a centralized interim storage. The final stage of the fuel cycle is geological disposal. The assemblies are encapsulated inside copper canisters, which are buried in a tunnel excavated deep into the bedrock.

The prerequisite of safety for final disposal is that the adverse radiation effects inflicted on the local population remain, at all times, insignificant compared to natural background. The natural level refers to, for example, radiation exposure caused by radon gas from the ground and cosmic radiation from space.

Finland is the forerunner in final disposal of nuclear waste. Direct geological disposal has been studied and prepared since the 1980’s. The disposal of fuel assemblies from the oldest reactors in Loviisa and Olkiluoto is scheduled to begin by the end of this decade.

The construction of new nuclear power plants also requires a comprehensive nuclear waste management plan. Since LDR-50 is designed to operate with conventional light water reactor fuel, waste management can also rely on existing solutions.

Frequently asked questions about the nuclear fuel cycle and waste