Integral nuclear reactor-steam generator unit

Claim 1

A NUCLEAR REACTOR COMPRISING AN UPRIGHT WALL FORMING A VERTICALLY ELONGATED PRESSURE VELLEL HAVING AN OPENING IN THE UPPER END THEREOF, A REMOVABLE CLOSURE FOR SAID OPENING, AN UPRIGHT TUBULAR BAFFLE ARANGED IN SAID PRESSURE VESSEL AND REMOVAL THROUGH SAID OPENING, SAID BAFFLE COACTING WITH SAID PRESSURE VESSEL WALL TO FORM A DOWNCOMER PASSAGE THEREBETWEEN AND AN UPRIGHT CENTRAL RISER CHAMBER, SAID BAFFLE PROVIDING COMMUNICATION BETWEEN SAID RISER CHAMBER AND SAID DOWNCOMER PASSAGE AT THE UPPER AND LOWER ENDS THEREOF, MEANS INCLUDING A PLURALITY OF HETEROGENEOUS NUCLEAR FUEL ELEMENTS ARRANGED AS A CORE IN SAID RISER CHAMBER TO PROVIDE A CONTROLLED SELF-SUSTAINING FISSION-TYPE CHAIN REACTON, A FLUID COOLANT HAVING A CIRCULATION UPWARDLY THROUGH SAID CORE AND SAID RISER CHAMBER AND DOWNWARDLY THROUGH SAID DOWNCOMER PASSAGE, A TUBE BUNDLE DISPOSED IN SAID DOWNCOMER PASSAGE AND AT LEAST PARTLY OFFSET FROM THE PERIMETER OF SAID PRESSURE VESSEL UPPER END OPENING, SAID TUBE BUNDLE BEING ARRANGED TO PERMIT RADIAL INWARD MOVEMENT THEREOF UPON REMOVAL OF ONLY SAID BAFFLE THROUGH SAID PRESSURE VESSEL UPPER END OPENING, SAID TUBE BUNDLE HAVING A MAXIMUM RADIAL DIEMENSION LESS THAN THE DIAMETER OF SAID PRESSURE VESSEL UPPER END OPENING TO PERMIT REMOVAL OF SAID TUBE BUNDLE THERETHROUGH, AND MEANS FOR PASSING A SECONDARY HEAT ABSORBING FLUID THROUGH SAID TUBE BUNDLE.