Nuclear reactors

Claim 1

A gas cooled fast nuclear reactor having a pair of generally parallel first and second grid plates, a plurality of elongated tubular coolant permeable fuel assemblies extending between said grid plates from one to the other, the sides of the grid plates facing away from each other defining inlet and outlet areas, each assembly including, inner and outer generally parallel perforated tubular elements and a porous fuel bed of fission product retaining fuel particles contained between the tubular elements along a major part of the length of the assembly, an elongated coolant outlet face formed by the bore wall of the inner tubular element of the tubular assembly, an elongated coolant inlet face formed by the outer wall of the outer tubular wall of the tubular assembly; elongated coolant supply channels adjacent and bounded in part by said inlet faces and extending along the length of said inlet faces, the supply channels including means for constraining all of the gas entering the supply channel to flow through the fuel bed, means for introducing coolant to the supply channels from the inlet area through said first grid, said supply channels thus defining a coolant flow path for coolant entering the supply channels to flow in series along the inlet faces and in parallel flow relation into and through the poRous fuel beds and through the outlet faces, elongated coolant delivery channels adjacent and formed in part by said outlet faces and extending along the length of said outlet faces to receive gas from said coolant flow path, the delivery channels including means for contraining all of the gas entering the delivery channels through the fuel bed to flow outwardly through discharge oepnings, the coolant delivery channels terminating at said discharge openings which open into the outlet area beyond the said second grid, said delivery channels thus defining a path for the coolant to flow along the outlet faces to said discharge openings, the flow area of the delivery channels into the outlet area being substantially as large as the flow area of the delivery channels at the downstream end thereof, the increasing size of the coolant delivery channels from the upstream end thereof to the discharge opening constituting a means for decreasing the velocity of the coolant and hence increasing the pressure of the coolant along the length of the coolant delivery channels in the flow direction, and thus reducing the difference in the pressure drop across the porous fuel bed along the length of the elongated fuel assembly.