Patent Application
20080095296
With reference to
As shown in
The expanded section 14 preferably begins at an elevation above the top of the active fuel. By having the expanded section 14 below the grid of the upper tie plate, additional flow area is created, thereby reducing the pressure drop relative to current designs. Additionally, the expanded section 14 eliminates the need for separate spacers and the fastener guard.
The expansion of the channel 10 on only two sides enables the design to be compatible with existing power plants. In an alternate embodiment shown in
The exact shape and location of the transition to the expanded section 14 can be determined through analysis and testing during product development. The transition could be a sharp step change, simple radius or very gradual angular change. The location of the elevation change could be at any point above where the control blades are positioned at maximum insertion. Alternatively, a small expansion may be formed down in the control blade zone with a larger one above the control blade or in the case of expanding on three or four sides, the non-control blade sides may expand below the control blade height.
In yet another alternative embodiment, the expanded section 14 may include a plurality of slots 22 therein defining one or more finger springs 24. The finger springs 24 serve the same purpose as the channel fastener springs in the conventional design. Additional or alternative slots may also be provided at the corners to make forming easier and to further reduce the pressure drop by creating more exit area for the bundle flow.
As a peripheral advantage, the expanded channel described herein may also enable a previously-proposed design for a top cover filter to be implemented. The top cover filter proposal was essentially a porous plate that would prevent debris from entering the fuel bundle from the top. A concern with the top filter, however, was the additional pressure drop. The expanded channel design described herein may create enough pressure drop margin to enable use of the top filter.
The expanded fuel channel described herein eliminates several components and the associated manufacturing, inspection and purchasing requirements associated with those components, thereby resulting in a cost savings. Moreover, the expanded channel reduces a pressure drop across the fuel bundle, increasing flow and bundle performance.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
