Abstract: In a liquid-metal cooled reactor equipped with a primary cooling system, a secondary cooling system and a steam turbine power generation system, or equipped with a primary cooling system and a steam power generation system, an alkali metal thermoelectric converter is disposed between the primary cooling system or the secondary cooling system and the steam turbine power generation system. Heat of the primary cooling system or the secondary cooling system is supplied to a high-temperature side of the alkali metal thermoelectric converter and waste heat on a low-temperature side of the alkali metal thermoelectric converter is supplied to the steam turbine power generation system. Thus, power generation by the steam turbine power generation system is performed simultaneously with power generation by the alkali metal thermoelectric converter. As a result, the power generation efficiency of the whole plant can be significantly increased.