Nuclear reactor heat exchangers

Claim 1

FOR INSTALLATION IN A TANK, A SHELL AND TUBE HEAT EXCHANGER SYSTEM COMPRISING A TOP CLOSURE PLUG FOR THE TANK HAVING APERTURES PENETRATING THERETHROUGH, INSERT PLUGS LOCATABLE RESPECTIVELY IN THE CLOSURE PLUG APERTURES, A HEADER DISPOSED BENEATH THE CLOSURE PLUG FOR RECEIVING A PRIMARY COOLANT AND HAVING A BASE PROVIDED WITH APERTURES IN POSITIONS CORRESPONDING TO THE CLOSURE PLUG APERTURES, AN ELONGATED SHELL UNIT CARRIED DEPENDENTLY BY EACH INSERT PLUG AND EXTENDING WITH A CLEARANCE FIT THROUGH A RESPECTIVE HEADER APERTURE, SUCH UNIT HAVING AN INLET OPENING ADAPTED TO REGISTER INTERNALLY OF THE HEADER WHEN THE RESPECT INSERT PLUG IS LOCATED IN THE CLOSURE PLUG AND AN OUTLET OPENING EXTERNALLY OF THE HEADER TO DEFINE A DOWNWARD FLOW PASS FOR THE PRIMARY COOLANT THROUGH THE UNIT, MEANS TO SEAL EACH UNIT AGAINST PASSAGE THROUGH THE HEADER APERTURES OF PRIMARY COOLANT, AND SECONDARY COOLANT CONDUCTING MEANS FOR EACH UNIT COMPRISING AN INLET AND AN OUTLET AT THE PLUG END OF THE UNIT, INLET AND OUTLET PIPEWORK EXTENDING RESPECTIVELY TO THE INLET AND OUTLET THROUGH THE RESPECTIVE INSERT PLUG, AND TUBING CONNECTED TO THE OUTLET AND HAVING A RUN PROGRESSING IN THE AFORESAID DOWNWARD PASS FROM THE OTHER END OF THE UNIT TO THE OUTLET FOR COUNTERFLOW HEAT EXCHANGE BETWEEN THE PRIMARY AND SECONDARY COOLANTS.