| 摘要 |
<p>In a nuclear fuel bundle (B) for a boiling water reactor, tapered fuel rods forming the bundle array are disclosed in a practical design including a fuel bundle and an improved associated spacer utilized in the upper two phase region of the fuel bundle. A tapered fuel rod is utilized having a large diameter bottom tube for holding corresponding large diameter fuel pellets at the fuel rod bottom, a smaller diameter top tube for holding correspondingly smaller diameter pellets at the top of the fuel rod, and a bell reducer (R) is situated between the large diameter lower fuel tube and the smaller diameter upper fuel tube. When the fuel bundle is conventionally assembled, a spring (32) in each cell biases the upper smaller diameter tubes in their designed side-by-side relation against stops (30,31,34) defined at each cell. At the same time, the spring is provided with sufficient flexibility to allow the lower large diameter tube and the transition bell reducer to pass through the individual cells of the upper spacer. <IMAGE></p> |
