The present application relates generally to nuclear reactors; and more particularly to, a system for dampening the level of vibration experienced by system piping within a nuclear reactor pressure vessel.
One type of nuclear reactor, a conventional boiling water reactor (BWR) is shown in
The core shroud 30 is a stainless steel cylinder that surrounds the nuclear fuel core 35, which includes a plurality of fuel bundle assemblies 40 (only a few are illustrated in
The coolant water flows downward through the downcomer annulus 25 and into the core lower plenum 55. Then the water in the core lower plenum 55 flows upward through the nuclear fuel core 35. In particular, water enters the fuel bundle assemblies 40, wherein a boiling boundary layer is established. A mixture of water and steam exits the nuclear fuel core 35 and enters the core upper plenum 60 under the shroud head 65. The steam-water mixture then flows through standpipes 70 on top of the shroud head 65 and enters the steam separators 75, which separate water from steam. The separated water is recirculated back to the downcomer annulus 25 and the steam flows out of the RPV 10 and to a steam turbine, or the like, (not illustrated).
The BWR also includes a coolant recirculation system, which provides the forced convection flow through the nuclear fuel core 35 necessary to attain the required power density. A portion of the water is drawn from the lower end of the downcomer annulus 25 via recirculation water outlet 80 and forced by a recirculation pump (not illustrated) into a plurality of jet pump assemblies 85 (one is illustrated in
As illustrated in
During RPV 10 operation, the flow through the feedwater sparger pipe 20 contains pressure fluctuations from various sources in the reactor system. These pressure fluctuations can have frequencies close to one or more natural vibration modes of the feedwater sparger pipe 20. The vibration modes experienced by the feedwater sparger pipe 20 depends, in part on, on preload and welds on the lugs 110 (not illustrated in
There are a few possible problems with the currently known systems for dampening the vibration. Currently known systems involve re-welding the lugs 110, which may lead to a repeat failure. These systems generally require longer installation time and expose operators to longer period of radioactivity.
For the aforementioned reasons, there is a need for a new system for dampening the vibration experienced by the feedwater sparger pipe 20. The system should not require welding. The system should reduce the installation time and lower operator exposure to radioactivity.
In accordance with an embodiment of the present invention, an apparatus for dampening vibration experienced by an object integrated with a structure within a reactor pressure vessel (RPV) of a nuclear power plant; wherein the apparatus comprises: a bearing plate configured for providing a barrier between an object and a structure, wherein the structure is located within a reactor pressure vessel (RPV) of a nuclear power plant; a lower section for holding a portion of the object, wherein a first surface of the lower section integrates with the bearing plate and a second surface of the lower section holds a portion of the object; an upper section for holding another portion of the object, wherein the upper section integrates with the bearing plate and mates with the lower section; wherein the lower section and the upper section cooperatively secure the object at a distance from a facing surface of the bearing plate, and allows for dampening of a vibration experienced by the object.
In accordance with another embodiment of the present invention, a system for reducing the vibration experienced by a pipe within a nuclear reactor pressure vessel (RPV), the system comprising: a nuclear fuel core comprising a plurality of fuel bundle assemblies; a feedwater inlet; a feedwater sparger pipe; a core spray line; and a clamp comprising an upper section and a lower section; wherein the clamp is connected to a portion of the feedwater sparger pipe to reduce a level of vibration experience by the feedwater sparger pipe; and wherein the clamp applies a compressive load to the feedwater sparger pipe and positions the feedwater sparger pipe and a distance from the core spray line.
Certain terminology is used herein for convenience only and is not to be taken as a limitation on the invention. For example, words such as “upper,” “lower,” “left,” “front”, “right,” “horizontal,” “vertical,” “upstream,” “downstream,” “fore”, and “aft” merely describe the configuration shown in the Figures. Indeed, the components may be oriented in any direction and the terminology, therefore, should be understood as encompassing such variations unless specified otherwise. Furthermore, the following discussion focuses on an embodiment of the present invention integrated with the feedwater sparger system of the RPV 10. Other embodiments of the present invention may be integrated with other systems that require a dampening of and/or frequency change in vibration.
The present invention has the technical effect of reducing the level of vibration experienced by a line, such as, but not limiting of, a pipe, a cable, tubing, or the like, that is connected to at least one separate structure. For example, but not limiting of, the structure includes: a RPV 10, a feedwater sparger pipe 20, steam generator, a pipe, a pressure vessel, a heat exchanger, a pump, a condenser, a tank, or the like. An embodiment of the present invention may provide support and a preload to the line at a new location or may replace an existing support, such as, but not limiting of, a weld; which may alter the natural frequencies to avoid resonance from occurring when the structure(s) is excited.
An embodiment of the present invention takes the form of an apparatus or system that may reduce the level of vibration experienced by a feedwater sparger pipe 20 or other similar object within a RPV 10. An embodiment of the present invention provides at least one repair clamp that generally adds support, to the feedwater sparger pipe 20. After installation, the repair clamp may lower the amplitude of, and/or change the frequency of, the vibration experienced by the feedwater sparger pipe 20.
Referring again to the Figures, where the various numbers represent like parts throughout the several views.
An embodiment of the repair clamp 200 may comprise three main components. An upper section 205 for restraining a portion of the feedwater sparger pipe 20. A lower section 210 for restraining another portion of the feedwater sparger pipe 20 and for receiving a portion of the upper section 205. A bearing plate 215 for providing a barrier between the feedwater sparger pipe 20 and a wall of the RPV 10. Generally, the upper section 205 and the lower section 210 cooperatively operate to secure the feedwater sparger pipe 20 and a desired distance from the wall of the RPV 10 and from a surface of the core spray line 105. When installed the repair clamp 200 may add or restore a preload to the feedwater sparger pipe 20, while changing the amplitude and/or frequency of the potential vibration.
Referring now to
The second crimp collar 230 serves to fix the second jacking bolt 235 to a desired position. This may prevent the second jacking bolt 235 from loosening due to vibration after the repair clamp 200 is installed. An embodiment of the second crimp collar 230 may allow for the second jacking bolt 235 to pass through and mate with a portion of the upper clamp body 250, as illustrated, for example, but not limiting of, in
The at least one pinch bolt 245 serves to apply a compressive load from the repair clamp 200 to the feedwater sparger pipe 20. Essentially, the at least one pinch bolt 245 clamps the upper section 205 and the lower section 210 around a portion of the feedwater sparger pipe 20. An embodiment of the upper clamp body 250 may allow for the lug 110 to mate with a surface on the upper clamp body 250. This may allow for a robust connection between the repair clamp 200 and the feedwater sparger pipe 20. The pinch plate 240 may serve to provide a bearing surface between the at least one pinch bolt 245 and the second jacking bolt 235.
As illustrated in
A surface of the upper clamp body 250 may be of a shape allowing for mating with the portion of the feedwater sparger pipe 20. For example, but not limiting of, the shape may comprise an arc of a similar radius of the outer diameter of the feedwater sparger pipe 20. Moreover, the surface may comprise a notch, or the like, that allows for mating with the lug 110.
The bearing plate 215 serves as a barrier between the repair clamp 200 and a wall of the RPV 10. Generally, the bearing plate 215 may form the rear of the repair clamp 200 encompassing the rear portions of the upper section 205 and the lower section 210. In an embodiment of the present invention an overall length of the bearing plate 215 extends beyond an overall length of the upper section 205 mated with the lower section 210. This feature may allow for the applied forces of the second jacking bolt 235 and the first jacking bolt 225 to be transferred on the wall of the RPV 10.
Referring now to
The lower clamp body 227 serves to receive and hold a portion of the feedwater sparger pipe 20. A first surface of the lower clamp body 227 may integrate with the bearing plate 215. A second surface of the lower clamp body 227 may be of a shape allowing for mating with the portion of the feedwater sparger pipe 20. For example, but not limiting of, the shape may comprise an arc of a similar radius of the outer diameter of the feedwater sparger pipe 20. Moreover, the second surface may comprise a notch, or the like, that allows for mating with the lug 110.
Referring now to
A second benefit of the repair clamp 200 allows for a range of approximately 0.250 inches of adjustment. This may accommodate a broad range of feedwater sparger pipe 20 positions relative to a wall of the RPV 10.
A third benefit involves the crimp collars 220,230, which may serves as a positive anti-rotation device. The crimp collars 220,230 may only require a visual inspection to confirm that the repair clamp 200 has not loosened.
The components of an embodiment present invention may be formed of any material capable of withstanding the operating environment to which the repair clamp 200 may be exposed.
In use, the repair clamp 200 may clamp around the feedwater sparger pipe 20 at a location of previous jacking bolts. When fully engaged, the repair clamp 200 may provide for generous clearance around the upper bounds of the feedwater sparger pipe 20 tolerance and connecting welds. The repair clamp 200 may restore the preload on the feedwater sparger pipe 20 at the location of the previous jacking bolts. The repair clamp 200 may also reduce the vibration experience by the feedwater sparger pipe 20.
Although the present invention has been shown and described in considerable detail with respect to only a few exemplary embodiments thereof, it should be understood by those skilled in the art that we do not intend to limit the invention to the embodiments since various modifications, omissions and additions may be made to the disclosed embodiments without materially departing from the novel teachings and advantages of the invention, particularly in light of the foregoing teachings. Accordingly, we intend to cover all such modifications, omission, additions and equivalents as may be included within the spirit and scope of the invention as defined by the following claims. For example, but not limiting of, an embodiment of the present invention may be used to: a) introduce a different vibration mode; h) to secure a pipe, cable, wire, or other similar object, at a fixed distance away from a separate structure or other object; or c) to apply a compressive load to at least one of the aforementioned objects.