Underground nuclear power plants

Purpose: To prevent underground scattering of nuclear fission products resulted from rupture accidents in primary coolant circuits. Constitution: A reactor cavity for housing an underground nuclear reactor, its accessory systems and equipments is communicated with a turbine cavity for housing a turbine, its accessory system and equipments by way of a main steam tunnel in which main steam pipes are laid. The main steam tunnel is further connected by way of a plurality of vent pipes with a pressure suppression cavity situated at a level equal to or lower than the tunnel and containing water in the inside. In this structure, while high temperature and high pressure coolants are filled in each of the cavities upon rupture of the primary coolant circuits, they are released passing through the vent pipes into the water of the pressure suppression cavity and condensated, whereby the pressure in each of the cavities can rapidly be reduced. (Furukawa, Y.)