Direct contact heat transfer-type steam generator

The steam generator comprises a heat exchanger portion through which primary sodium heated to a high temperature in a reactor core passes, a vessel incorporating the heat exchanger portion, a low-melting point alloy contained in the vessel and in which the heat exchanger portion is immersed, a water injection member for injecting water directly to the low melting alloy, and a steam take-out port disposed above a free liquid surface of the low melting point alloy. Water is directly injected into the low-melting point alloy heated by the primary sodium to generate steams. The high temperature primary sodium heats the low-melting point alloy in the vessel by indirect heat exchange during passage through the heat exchanger portion. The heated low-melting point alloy boils and evaporates water directly injected by means of direct-heat transfer. Steams are discharged from the steam take-out port above the free liquid surface of the low-melting point alloy. In addition, the low-melting point alloy does not react with water. Further, even if the primary sodium leaks from the heat exchanger portion, the low-melting point alloy intrudes into sodium, thereby enabling to avoid contact between sodium and water. (N.H.)