FUEL PENCIL FOR A NUCLEAR REACTOR

摘要

The nuclear reactor (1) comprises a lower stopper (10) sealingly fixed to a lower end of the tubular casing (2) of the pencil which comprises a part (10a) which is internal to the casing (2) successively comprising a first cylindrical section (11) having a diameter which is substantially equal to the inner diameter of the tubular casing (2); a second cylindrical section (12) whose diameter is smaller than the inner diameter of the tubular casing (2); and a third cylindrical section (13) whose inner diameter is smaller than the inner diameter of the tubular casing (2) and greater than the diameter of the second cylindrical section (12), such that 1-2 tenths of a millimeter radial play is created in the gas passage between the outer surface of the third section (13) and the inner surface of the casing (8). The fuel pellet column (3) rests on a substantially planar upper surface (14) of the third cylindrical section (13) of the inner part (10a) of the stopper (10). An annular space (16) for the expansion of gas making up a plenum which is complementary to the fuel pencil is defined between the outer surface of the second cylindrical section (12) of the inner part (10a) of the stopper (10) and the inner surface of the tubular casing (2).