| 摘要 |
In a BWR- or PWR-type nuclear reactor, the fuel rods in the fuel assembly are cooled by a coolant flow which is pumped through the fuel core. Depending on the degree of burn-up of the fuel rods, the coolant flow to the fuel assemblies may need to be changed for the cooling to correspond to the actual need. To bring about a control of the coolant flow responsive to the degree of burn-up of the fuel rods, the irradiation growth of the elongated elements in the fuel assembly has been utilized. The elongated shape of the fuel rods results in a considerable linear expansion due to the irradiation growth. The ends (9, 11) of the elongated fuel rods have therefore been adapted to fit into corresponding openings (7, 8) in the top tie plate (1) or the bottom tie plate (2) to enable the ends, during the linear expansion due to the irradiation growth, to conform, to a greater or lesser extent, to the openings in order thus to control the passage of the coolant flow. |
