Multi-pass, vapor moderated and cooled nuclear reactor and method of operating to variably moderate and control same

Claim 1

A HETEROGENEOUS NUCLEAR REACTOR COMPRISING A PRESSURE VESSEL DIVIDED INTO A PLURALITY OF PASSES FOR THE FLOW OF A FLUID THERETHROUGH, A MULTIPLICITY OF FISSIONABLE MATERIAL-BEARING FUEL ELEMENTS ARRANGED N A FIXED LATTICE AS A CORE IN A FIRST AND A THIRD PASS OF SAID REACTOR, SAID CORE ARRANGED TO UNDERGO A FISSION-TYPE CHAIN REACTION, MEANS FOR PASSING A SINGLE PHASE HYDROGEN-BEARING MODERATING AND COOLING VAPOR THROUGH A FIRST PASS IN DIRECT HEAT TRANSFER CONTACT WITH SAID FUEL ELEMENTS THEREIN TO COOL SAID ELEMENTS AND HEAT SAID VAPOR TO A PREDETERMINED RANGE OF MODERATING DENSITY, MEANS FOR PASSING SAID VAPOR THROUGH A SECOND PASS ABOUT ALL OF SAID FUEL ELEMENTS IN SAID FIRST AND THIRD PASSES TO MODERATE SAID CHAIN REACTION, MEANS FOR PASSING SAID HEATED VAPOR THROUGH SAID THIRD PASS IN DIRECT HEAT TRANSFER CONTACT WITH SAID FUEL ELEMENTS THEREIN, SAID FIRST PASS FUEL ELEMENTS BEING ARRANGED TO REFLECT CHANGES IN REACTIVITY OF SAID REACTOR BY CHANGING THE AMOUNT OF HEAT IMPARTED TO SAID VAPOR IN CONTACT THEREWITH TO REGULATE THE DENSITY OF SAID VAPOR ENTERING SAID SECOND PASS T VARY THE REACTIVITY OF SAID REACTOR, AND MEANS FOR VARYING THE DENSITY OF SAID VAPOR IN SAID CORE TO REGULATE THE CHAIN REACTION THROUGHOUT THE LIFE OF SAID FUEL ELEMENTS.