Nuclear power plants generate electricity and a large amount of waste heat which is valuable for cogeneration. District heating (DH) is a suitable technology to decarbonize the European heat sector. By contrast with most of nuclear non-electric applications, nuclear district heating (NDH) has already been implemented in Europe, thus providing us with some valuable empirical insights. This paper investigates the forces and obstacles to nuclear cogeneration by looking at the Loviisa 3 NDH project in Finland. The key forces are energy efficiency, decarbonization of the heat sector, operational competitiveness of future nuclear technologies, and synergies with renewable energies. The key obstacles are split incentives, electricity prices volati...