VTT is developing a low-temperature nuclear reactor for district heating, as a type of small modular reactor (SMR) having high potential for deployment. The safety design relies on passive systems, which enable fulfilling the high safety requirements of nuclear reactors with simplified technology. A significant patent related to the passive cooling functions of the LDR-50 reactor module has been granted to VTT in November 2021.
VTT launched the Low Temperature District Heating and Desalination Reactor (LDR) project in February 2020. The aim is to develop a nuclear energy solution tailored to the Finnish district heating needs, in an effort to replace fossil fuels in heat production. Decarbonization of the heating sector is considered one of the major climate challenges in Finland.
The invention is related to a passive heat removal mode, which is actuated when the normal cooling path through the primary heat exchangers is compromised, for example, following the loss of electric power. The reactor module consists of two nested pressure vessels, with their intermediate space partially filled with water. When the primary cooling functions are lost, water in the intermediate space begins to boil, forming an efficient passive heat transfer path from the reactor core to an external heat sink. The system includes no moving parts vulnerable to mechanical failure.