Straight tubes in a vertical shell steam generator

Claim 1

A STEAM GENERATOR COMPRISING A VERTICAL CYLINDRICAL SHELL HAVING A LIQUID SPACE AND A VAPOR SPACE; A VERTICALLY ORIENTED BAFFLE WITHIN THE SHELL LIQUID SPACE DEFINING A STEAM GENERATING CHAMBER, AND, BETWEEN THE SHELL AND BAFFLE, AN ANNULAR DOWNCOMER PASSAGEWAY; A RISER AT THE UPPER END OF THE BAFFLE IN COMMUNICATION WITH THE CHAMBER; A PLURALITY OF RADIALLY SPACED VAPOR LIQUID SEPARATORS AT THE UPPER END OF THE RISER, THE RISER BEING CLOSED AT ITS TOP; A PLURALITY OF RECTILINEAR TUBES EXTENDING AXIALLY WITHIN THE BAFFLE STEAM GENERATING CHAMBER; A PLURALITY OF UPPER AND LOWER SUB-HEADER OF HEXAGONAL OUTLINE AT THE UPPER AND LOWER ENDS OF THE STEAM GENERATING CHAMBER RESPECTIVELY, THE TUBES TERMINATING IN THE SUB-HEADERS, THE SUB-HEADERS AND TUBES BEING ARRANGED SUCH THAT THE TUBES ARE REGULARLY AND UNIFORMLY DISTRIBUTED OVER THE CROSS-SECTION OF THE VAPOR GENERATING CHAMBER, ADJACENT SUB-HEADERS BEING STAGGERED IN AN AXIAL DIRECTION TO PERMIT THE FLOW OF VAPOR AND LIQUID FROM THE VAPOR GENERATING CHAMBER TO THE RISER; A PLURALITY OF MAIN HEADERS; MEANS COMMINICATING THE MAIN HEADERS WITH THE SUBHEADERS; A PLURALITY OF CONNECTIONS FOR THE MAIN HEADERS, THE CONNECTIONS FOR THE UPPER MAIN HEADERS EXTENDING UPWARD IN THE VICINITY OF THE AXES OF THE BAFFLE AND RISER AND PENETRATING THE RISER AND SHELL AT A LEVEL ABOVE THE LEVEL OF THE SEPARATORS.