Patent Number: 050874128
Section: claims

1. A nuclear reactor including a reactor vessel having a core barrel inside the reactor vessel, fuel elements and safety rods inside the core barrel, a fuel element housing thimble surrounding each fuel element and defining a gap therebetween, and a primary coolant flow path that includes flow through the fuel element housing thimble gaps, wherein the improvement comprises: a. means for circulating a liquid moderator through the core barrel around the fuel element housing thimbles;  b. said primary coolant being at a cooler temperature than said liquid moderator when entering said fuel element housing thimble gaps; and  c. fins on the fuel element housing thimbles for conducting heat from the liquid moderator to the primary coolant flowing through said fuel element housing thimble gaps.  a. means for circulating a liquid moderator through the core barrel around the fuel element housing thimbles,  b. said primary coolant being at a cooler temperature than said liquid moderator when entering said fuel element housing thimble gaps; and  c. finds on the fuel element housing thimbles for conducting heat from the liquid moderator to the primary gas coolant flowing through said fuel element housing thimble gaps. 2. The nuclear reactor of claim 1, wherein the primary coolant is a gas. 3. The nuclear reactor of claim 1, wherein said means for circulating a liquid moderator comprises pumps and fill and drain nozzles on the reactor vessel. 4. A gas cooled nuclear reactor including a reactor vessel having a core barrel inside the reactor vessel, fuel elements and safety rods inside the core barrel, a fuel element housing thimble surrounding each fuel element and defining a gap therebetween, and a primary coolant flow path that includes flow through the fuel element housing thimble gaps, wherein the improvement comprises: 5. The nuclear reactor of claim 4, further comprising a supplemental heat exchanger external to the reactor in fluid communication with the liquid moderator and primary coolant of the reactor for conducting heat from the liquid moderator to the primary coolant.