Patent Application
20100246743
The present application relates generally to steam pressure vessels; and more particularly to, a system for dampening a level of flow-induced vibrations experienced by components of a steam pressure vessel.
One type of steam pressure vessel is 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 separates water from steam. The separated water is recirculated back to the downcomer annulus 25 and the steam exits the RPV 10 via a steam outlet nozzle 110.
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 operation steam exiting the RPV 10 tends to rotate while flowing through the steam outlet nozzle 110, creating at least one vortex. The vortex can create flow-induced vibrations and a pressure loss. As known, flow-induced vibrations are a factor in causing cracks to internal RPV 10 components, such as, but not limiting of, the steam separators 75. Some flow-induced vibrations have pressure fluctuations with frequencies close to one or more natural vibration modes of one, or more, of the internal components of the RPV 10. When an excitation frequency is near the natural frequencies of the internal component, the resulting vibration may crack the internal component. This may require the RPV 10 to operate at a reduced load. This may also require a shutdown of the RPV 10.
For the aforementioned reasons, there is a need for an apparatus and system for reducing the likelihood of flow-induced vibrations. The apparatus should reduce the possibility of vortex formation. The apparatus should provide a cost effective solution to the known issue of flow-induced vibrations occurring in pressure vessels.
In accordance with an embodiment of the present invention, an apparatus for reducing flow induced vibrations within a system, the apparatus comprising: a base adaptable for integrating within a system that allows for flow induced vibrations; and a vortex restrictor configured for reducing the likelihood of a flow vortex forming; wherein the flow vortex leads to the flow induced vibrations; and wherein the vortex restrictor is supported by the base; wherein the vortex restrictor is positioned adjacent a flow path of a fluid of the system and reduces a level of the flow induced vibrations.
In accordance with another embodiment of the present invention, a system for reducing flow induced vibrations experienced within a steam system of a nuclear reactor pressure vessel (RPV), the system comprising: a nuclear fuel core comprising a plurality of fuel bundle assemblies; a feedwater inlet; a steam nozzle; and a flow straightener comprising a base and a vortex restrictor; wherein the vortex restrictor is positioned adjacent a steam flow path of steam within the steam system and reduces a level of flow induced vibrations.
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.
The following discussion focuses on an embodiment of the present invention integrated with at least one steam outlet nozzle 110 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 the flow-induced vibrations. For example, but not limiting of, the other pressure vessels including: a steam generator, a heat exchanger, a condenser, a boiler, or the like.
Referring again to the Figures, where the various numbers represent like parts throughout the several views.
An embodiment of the flow straightener 200 may comprise two primary components, a base 210 and a vortex restrictor 220. The base 210 generally serves to support the flow straightener 200. The base 210 may be adapted for connecting with at least one surface of the steam outlet nozzle 110. The vortex restrictor 220 configured for reducing the likelihood of formation of a flow vortex. A portion of the vortex restrictor 220 may be positioned adjacent a flow path of a fluid flowing within a system of the RPV 10.
Specifically,
The vortex restrictor 220 generally serves to reduce the likelihood of the of at least one vortex formation. The vortex restrictor 220 may be positioned directly or indirectly within the flow path of the steam exiting the RPV 10. The vortex restrictor 220 may be formed of a shape that allows for partially or completely blocking the formation of a vortex. An embodiment of the vortex restrictor 220 may resemble a fin or vane-like, as illustrated in
In use, the flow straightener 200 engages the steam exiting the RPV 10 via the steam outlet nozzle 110, as previously described. Each flow straightener 200 may prevent the formation of the vortex, possibly leading to a reduction in flow-induced vibrations.
The components of an embodiment present invention may be formed of any material capable of withstanding the operating environment to which the flow straightener 200 may be exposed.
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.
