METHOD FOR CLEANING A NECK SECTION OF A JET PUMP ASSEMBLY OF A NUCLEAR REACTOR

Abstract

A method for cleaning a jet pump assembly of a nuclear reactor may comprise inserting a cleaning tool into the jet pump assembly such that a front face of the cleaning tool is adjacent to an internal surface of the jet pump assembly and below a level of a first liquid in the jet pump assembly; the method may further comprise directing a plurality of front jets of a second liquid from a plurality of front orifices onto the front face of the cleaning tool such that the plurality of front jets of the second liquid strike the internal surface of the jet pump assembly; the method may further comprise maintaining a clearance distance between the front face of the cleaning tool and the internal surface of the jet pump assembly during the cleaning of the jet pump assembly.

Description

METHOD FOR CLEANING A NECK SECTION OF A JET PUMP ASSEMBLY OF A NUCLEAR REACTOR FIELD OF INVENTION This description relates to cleaning methods for a jet pump assembly of a nuclear reactor. BACKGROUND OF THE INVENTION Figure 1 is a cutaway view of a conventional jet pump assembly in a reactor pressure vessel of a boiling water reactor (BWR). Referring to Figure 1, a drive flow 102 of a mobile fluid (cooling liquid outside the reactor pressure vessel) enters the inlet riser 104 and flows upward to the inlet elbows 106. As the drive flow 102 is discharged downward through the nozzles 108, an entrained flow 110 of suction fluid (cooling liquid inside the reactor pressure vessel) is drawn into the neck section 112 of the inlet mixer 114 and mixes with the drive flow 102. The mixed flow continues downward to the diffusers 116 where the kinetic energy of the mixed flow is converted into pressure. When the boiling water reactor is shut down for maintenance, the jet pump assembly still contains the liquid from drive flow 102 and entrained flow 110. As a result, cleaning the jet pump assembly typically involves disassembling it to allow adequate access to the surfaces required for cleaning. Although efforts have been made to clean the jet pump assembly without disassembly, the ability to clean the jet pump assembly remains a challenge in such a situation. BRIEF DESCRIPTION OF THE INVENTION A method for cleaning a jet pump assembly of a nuclear reactor may comprise inserting a cleaning tool into the jet pump assembly such that a front face of the cleaning tool is adjacent to an internal surface of the jet pump assembly and below a level of a first liquid in the jet pump assembly. The method may further comprise directing a plurality of front jets of a second liquid from a plurality of front orifices. QFQZ ίη / ZZΖΠZ / E / YΙΛΙ on the front face of the cleaning tool such that the plurality of front jets of the second liquid travel through the first liquid and strike the inner surface of the jet pump assembly. The method may further comprise maintaining a clearance distance between the front face of the cleaning tool and the inner surface of the jet pump assembly during cleaning of the jet pump assembly. Inserting the cleaning tool may involve connecting the cleaning tool to a curved rod and lowering the cleaning tool into a secondary inlet opening of the jet pump assembly using the curved rod. The insertion of the cleaning tool may also include connecting the cleaning tool to a hose, mounting a handling tool over a flange of an inlet mixer of the jet pump assembly, and bending the hose and lowering the cleaning tool into a secondary inlet opening of the jet pump assembly using the handling tool. The direction of the plurality of front jets may include forcing the second liquid over a throat section of an inlet mixer of the jet pump assembly. The direction of the plurality of frontal jets can also be carried out at a pressure of at least 14,061,397 kgf / cm2 (20,000 pounds per square inch). Maintaining the reserve distance may include actuating the second liquid from a plurality of rear holes onto a rear face of the cleaning tool in the form of a plurality of rear jets to generate a reaction force to propel the front face of the cleaning tool toward the inner surface of the jet pump assembly. The drive of the second liquid from the plurality of rear holes can be carried out in such a way that the side plates of the cleaning tool make contact with the inner surface of the jet pump assembly while the front face of the cleaning tool is separated from the inner surface of the jet pump assembly. The direction and actuation of the second fluid can be carried out in such a way that the ratio of the plurality of front jets to the plurality of rear jets varies from approximately 1:1 to 1:2. Insertion and steering can be performed without disassembling the jet pump assembly. A cleaning tool for removing deposits from a jet pump assembly of a nuclear reactor may comprise a spray head including a front face and a rear face. The front face defines front openings and the rear face defines rear openings. The cleaning tool may further comprise a structure The QFQZ ίη / ZZΖΠZ / E / YΙΛΙ of removable orifice coupled with each of the front and rear openings. The cleaning tool may further comprise side plates secured to the opposite end faces of the spray head. The side plates project beyond the front face to establish a clearance distance from the jet pump assembly during deposit removal. The front face can be a convex surface and the back face can be an opposite concave surface. The removable hole structure can be threaded to each of the front and rear openings. The front face can define a number of front openings ranging from approximately 5 to 75. The back face can define a number of back openings ranging from approximately 5 to 75. The side plates can project beyond the front face in such a way that the clearance distance is approximately 1.27 centimeters (0.5 inches) or less during deposit removal. The side plates can be formed from a material that has a Mohs hardness of 3 or less. A system for cleaning the jet pump assembly of a nuclear reactor may comprise a cleaning tool and a curved rod connected to the cleaning tool. The curved rod is configured to position the cleaning tool inside the jet pump assembly. A system for cleaning the jet pump assembly of a nuclear reactor may also comprise a cleaning tool, a hose connected to the cleaning tool, and a handling tool configured to mount onto the jet pump assembly and to bend the hose to place the cleaning tool inside the jet pump assembly. BRIEF DESCRIPTION OF THE DRAWINGS The various advantages and features of the non-limiting embodiments herein may become more apparent upon review of the detailed description in conjunction with the accompanying drawings. The accompanying figures are provided for illustrative purposes only and should not be interpreted as limiting the scope of the claims. The accompanying drawings should not be considered as drawn to scale unless explicitly stated. QPQZ ίη / ZZΖΠZ / E / YΙΛΙ of clarity, several dimensions of the drawings may have been exaggerated. FIG. 1 is a cutaway view of a conventional jet pump assembly in a reactor pressure vessel of a boiling water reactor (BWR). FIG. 2 is a perspective view of a system that includes a cleaning tool for a jet pump assembly in accordance with an exemplary embodiment. FIG. 3 is a front view of a spray head of a cleaning tool for a jet pump assembly in accordance with an exemplary embodiment. FIG. 4 is a top view of a spray head of a cleaning tool for a jet pump assembly in accordance with an exemplary embodiment. FIG. 5 is a perspective view of a spray head of a cleaning tool for a jet pump assembly in accordance with an exemplary embodiment. FIG. 6 is a translucent view of a jet pump assembly during a cleaning method in accordance with an exemplary modality. FIG. 7 is another translucent view of a jet pump assembly during a cleaning method in accordance with an exemplary modality. FIG. 8 is a perspective view of a system that includes a handling tool used in a cleaning method in accordance with an exemplary modality. FIG. 9 is another perspective view of a system that includes a manipulation tool used in a cleaning method in accordance with an exemplary modality. FIG. 10 is a perspective view of a jet pump assembly during a cleaning method using a handling tool in accordance with an exemplary modality. FIG. 11 is another view of a jet pump assembly during a cleaning method using a handling tool in accordance with an exemplary modality. FIG. 12 is a photograph of a neck section of a prototype jet pump assembly after a cleaning method in accordance with an exemplary modality. DETAILED DESCRIPTION OF THE INVENTION It should be understood that when it is stated that a layer or element is in, connected to, coupled to, or covering another layer or element, it may be directly in, connected to, coupled to, or covering the other element or layer, or other intermediate layers or elements may be present. In contrast, when it is stated that an element is directly in, QFQZ ίη / ZZΖΠZ / E / YΙΛΙ directly connected or directly coupled to another element or layer; no intermediate layers or elements are present. Equal numbers refer to equal elements throughout the specification. As used herein, the term and / or includes any and all combinations of one or more of the associated listed items. It should be understood that although the terms first, second, third, etc., may be used here to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or section from another. Thus, a first element, component, region, layer, or section discussed later could be called a second element, component, region, layer, or section without departing from the teachings of exemplary modalities. Spatially relative terms (e.g., under, below, lower, above, and the like) may be used herein to facilitate the description of an element or the relationship of a feature to one or more other elements or features, as illustrated in the figures. It is understood that these spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is inverted, elements described as under or below other elements or features may then be oriented above those other elements or features. Thus, the term "under" may encompass both an "above" and a "below" orientation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein should be interpreted accordingly. The terminology used herein is for the sole purpose of describing the various modalities and is not intended to limit the modalities exemplified. As used here, the singular forms a, an, and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is further understood that the terms include, which includes comprises, and / or which comprises, when used in this description, specify the presence of the stated features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or groups thereof. The exemplary forms are described herein with reference to the cross-sectional illustrations, which are schematic representations of ideal forms (and intermediate structures) of exemplary forms. As such, variations in the shapes of the illustrations are to be expected as a result of, for example, production techniques and / or tolerances. Thus, the exemplary forms should not be interpreted as limited to the shapes of regions QFQZ ίη / ZZΖΠZ / E / YΙΛΙ illustrated herein but must include deviations in forms as a result of, for example, production. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person skilled in the art to which the exemplary modalities belong. It is further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly defined herein. Figure 2 is a perspective view of a system that includes a cleaning tool for a jet pump assembly according to an exemplary embodiment. Referring to Figure 2, the system includes a cleaning tool 202 that is attached to a rod 220 by means of a connector 214. The rod 220 is a rigid, tubular structure that defines an internal passage configured to carry a fluid flow for cleaning the jet pump assembly. The cleaning tool 202 defines an internal space configured to receive the fluid flow from the rod 220 by means of the connector 214. The connector 214 may be a threaded connector, a bayonet connector, or another type of secure, releasable connector. Although the connector 214 is illustrated as being on the upper face 208 of the spray head, it should be understood that the exemplary embodiments are not limited to this. The cleaning tool 202 includes a plurality of orifice structures 216 arranged on a front face 204 of the spray head. The orifice structures 216 are configured to transform the fluid flow exiting the front face 204 (during cleaning) into a plurality of high-pressure front jets. Each orifice structure 216 is designed to be a separate, removable component. In this respect, the orifice structures 216 can be changed as needed to adjust the cleaning pressure. For example, the orifice structures 216 can be structured to have externally threaded surfaces configured to engage with internally threaded openings on the front face 204. A pair of side plates 218 is secured to opposite end faces of the cleaning tool's spray head 202 to provide an appropriate clearance distance from a surface of the jet pump assembly during cleaning of that surface. For example, the side plates 218 may project beyond the front face 204 so that the clearance distance between the front face 204 and the surface being cleaned is approximately 1.27 centimeters (0.5 inches) or less. The side plates 218 are designed to be interchanged with plates of different sizes with relative ease. QFQZ ίη / ZZΖΠZ / E / YΙΛΙ to obtain the desired clearance distance. In addition, the front face 204 can be a convex surface that is dimensioned to correspond to a curved surface of a neck section of a jet pump assembly. As a result, a relatively uniform clearance distance can be provided during cleaning. Furthermore, the side plates 218 can be formed from a material having a Mohs hardness of 3 or less (e.g., aluminum). In such a case, the occurrence of damage to the surface of the jet pump assembly being cleaned (e.g., from scraping by the side plates 218) can be reduced or prevented. During a cleaning method for a jet pump assembly, the rod 220 allows the tool 202 to be inserted into and positioned within the jet pump assembly. In this respect, the rod 220 may include a first angled section and a second angled section to facilitate the maneuvering of the cleaning tool 202, although exemplary embodiments are not limited to these. Figure 3 is a front view of a spray head of a cleaning tool for a jet pump assembly according to an exemplary embodiment. Referring to Figures 2 to 3, the spray head 200 includes the connector 214 on its top face 208 and a plurality of front openings 206 on its front face 204. Although seventeen front openings 206 are shown, a different number may be provided. For example, the front face 204 may define a number of front openings 206 ranging from approximately 5 to 75. Furthermore, instead of being arranged linearly, the front openings 206 may be arranged in a zigzag pattern, in rows (e.g., in an array), or in some other suitable manner.When fully assembled, a hole structure 216 will be attached to each of the above openings 206, a side plate 218 will be secured to each of the opposite end faces of the spray head 200, and a rod 220 will be attached to the spray head 200 by means of the connector 214. Figure 4 is a top view of a spray head for a cleaning tool for a jet pump assembly according to an exemplary embodiment. Referring to Figures 2 to 4, the front face 204 is a convex surface and the rear face is a concave surface. The curvature of the front face 204 and the rear face may be the same. As a result, the spray head 200 may resemble a section of an annular structure. Additionally, the connector 214 may be centered between the opposite end faces of the spray head 200. Figure 5 is a rear view of a spray head of a cleaning tool for a jet pump assembly according to an exemplary embodiment. Referring to Figures 2 to 5, in addition to the connector 214 located on the upper face 208 of the spray head 200, the rear face 210 includes a plurality of rear openings. QFQZ ίη / ΖΖΠΖ / Ε / ΥΙΛΙ 212. Although five rear openings 212 are shown, a different number may be provided. For example, the rear face 210 may define a number of rear openings 212 ranging from approximately 5 to 75. Furthermore, instead of being arranged linearly, the rear openings 212 may be arranged in a zigzag pattern, in rows (e.g., in an array), or in some other suitable manner. In addition, each of the rear openings 212 is configured to receive an orifice structure (in a manner analogous to how each of the front openings 206 is configured to receive an orifice structure 216). The orifice structures coupled to the rear openings 212 are configured to transform the fluid flow exiting the rear face 210 (during cleaning) into a plurality of high-pressure rear jets.The orifice structures attached to the rear openings 212 can be changed as needed to adjust the reaction force. Figure 6 is a translucent view of a jet pump assembly during a cleaning method according to an exemplary embodiment. Referring to Figures 2 to 6, the cleaning tool can be inserted into the jet pump assembly by means of the rod 220 to clean the neck section 312. Access to the internal surface of the jet pump assembly can be achieved by inserting the cleaning tool 202 into an inlet opening 310 (e.g., the secondary inlet opening) between the nozzles 308 and the neck section 312. The cleaning tool 202 can be manufactured in a variety of sizes depending on the size of the inlet opening 310. The rod 220 can be manually manipulated by a plant operator to maneuver the cleaning tool 202. Regarding the orientation of the cleaning tool 202, the front face 204 is designed to face the inner surface of the neck section 312 of the jet pump assembly. Additionally, the contour of the front face 204 is structured to match the curvature of the inner surface of the neck section 312. When properly positioned, the side plates 218 of the cleaning tool 202 make contact with the inner surface of the neck section 312 to provide an appropriate clearance. In this manner, the cleaning tool 202 can be lowered into (and raised from) the neck section 312 using the rod 220. FIG. 7 is another translucent view of a jet pump assembly during a cleaning method in accordance with an exemplary embodiment. Referring to FIGS. 2 to 7, the cleaning tool 202 has been inserted into the inlet opening 310 of the jet pump assembly and lowered into the neck section 312 by means of the rod 220. In this lowered position, the cleaning tool 202 can be submerged below a level of a first liquid in the jet pump assembly. During cleaning, a flow of a second liquid through rod 220 is QFQZ iη / ZZΖΠZ / E / YΙΛΙ is expelled from the orifice structures 216 on the front face 204 of the cleaning tool 202 in the form of front jets that travel through the first liquid and strike the inner surface of the neck section 312. Additionally, the second liquid is also expelled from the orifice structures on the rear face 210 of the cleaning tool 202 in the form of rear jets that generate a reaction force to push the front face 204 toward the inner surface of the neck section 312. Consequently, the side plates 218 of the cleaning tool 202 will be pushed against the inner surface of the neck section 312. These side plates 218 of the cleaning tool 202 allow an appropriate clearance distance between the front face 204 and the inner surface of the neck section 312 to be maintained during cleaning. A pressure of at least 20,000 pounds per square inch may be used to generate the plurality of front jets from the front face 204 and / or the plurality of rear jets from the rear face 210 of the cleaning tool 202. The required pressure may be supplied by a pumping system. The ratio of the plurality of front jets to the plurality of rear jets may vary from approximately 1:1 to 1:2. In one exemplary embodiment, the cleaning method may be performed without disassembling the jet pump assembly, thereby saving time and costs. Figure 8 is a perspective view of a system that includes a handling tool used in a cleaning method according to an exemplary modality. Referring to Figure 8, a cleaning tool 402 is connected to a hose 420 as part of a system for cleaning a jet pump assembly. The hose 420 defines an internal passage configured to carry a fluid flow for cleaning the jet pump assembly. The cleaning tool 402 defines an internal space configured to receive the fluid flow from the hose 420. Apart from some variations such as size and shape, the cleaning tool 402 can be as described in combination with the cleaning tool 202. Although hose 420 may be more flexible than rod 220 (for example, in FIG. 2), hose 420 is still relatively rigid and difficult to manipulate by hand. Consequently, a handling tool may be used to bend and move hose 420 to maneuver cleaning tool 402 into and out of the jet pump assembly. The handling tool includes a base 404 configured to clamp a portion of the jet pump assembly. A pair of body plates 410 is secured to the base 404, and a roller arrangement is provided between the body plates 410 to interact with hose 420. A motor 418 is configured to drive at least one of the rollers. An arm 414 is also secured to each of the body plates 410. QFQZ ίη / ZZΖΠZ / E / YΙΛΙ help secure the handling tool against the jet pump assembly. Figure 9 is another perspective view of a system including a handling tool used in a cleaning method according to an exemplary modality. Referring to Figure 9, one of the handling tool's body plates 410 has been removed to show the arrangement of the rollers used to interact with the hose 420. The roller arrangement is configured to guide the hose 420, and thus the cleaning tool 402, from the raised position (shown) to a lowered position within the jet pump assembly during cleaning. Figure 10 is a perspective view of a jet pump assembly during a cleaning method using a handling tool in accordance with an exemplary embodiment. Referring to Figure 10, a handling tool is mounted on a jet pump assembly that is to be cleaned. For mounting, the base 404 can be clamped onto the flange of the neck section 412. In addition, the arms 414 can help secure the handling tool against the supports 416 (which are connected to the nozzle 408 and the neck section 412). The edge of the body plates 410 adjacent to the inlet elbow 406 and the nozzle 408 can also be profiled to reduce or avoid the potential for interference when mounting the handling tool. The cleaning tool 402 will be in the raised position (shown) when the handling tool is being mounted or moved.During cleaning, the motor 418 will drive the roller arrangement to move the hose 420 downwards to allow the cleaning tool 402 to descend from the inlet opening 422 to a lower position within the neck section 42. FIG. 11 is another view of a jet pump assembly during a cleaning method using a handling tool in accordance with an exemplary embodiment. Referring to FIG. 11, the cleaning tool 402 is in a lowered position, which may be below the level of a first liquid within the neck section 412. During cleaning, a second liquid is supplied through hose 420 and expelled from the cleaning tool 402 in the form of front jets that strike the inner surface of the neck section 412 (e.g., to remove deposits) and rear jets that propel the side plates of the cleaning tool 402 against the neck section 412 to maintain the appropriate clearance distance.The motor 418 is controlled to drive the roller arrangement in a manner that extends or retracts the hose 420 to access and clean the target internal surfaces of the neck section 412. Once a target section of the jet pump assembly is clean, the cleaning tool 402 can be returned to the raised state and the handling tool can be moved and mounted onto a part. QFQZ ίη / ZZΖΠZ / E / YΙΛΙ different from the flange of the neck section 412 to access other surfaces to be cleaned. As appropriate, the cleaning requirement can be fulfilled without disassembling the jet pump assembly. Figure 12 is a photograph of a neck section of a prototype jet pump assembly after cleaning in accordance with an exemplary method. Referring to Figure 12, a coating used to simulate rust deposits was substantially removed by the cleaning method discussed herein. Although several exemplary embodiments have been described herein, it should be understood that other variations are possible. Such variations should not be considered as a departure from the spirit and scope of the present description, and as all such modifications would be obvious to a person skilled in the art, it is intended that they be included within the scope of the following claims. QFQZ ίη / ΖΖΠΖ / Ε / ΥΙΛΙ Parts List QFQZ ίη / ΖΖΠΖ / Ε / ΥΙΛΙ 102 Drive Flow 104 Inlet Standpipe 106 Inlet Elbow 108 Nozzle 110 Entrained Flow 112 Neck Section 114 Inlet Mixer 116 Diffuser 200 Spray Head 202 Cleaning Tool 204 Front Face 206 Front Opening 208 Top Face 210 Rear Face 212 Rear Opening 214 Connector 216 Orifice Structure 218 Side Plate 220 Rod 308 Nozzle 310 Inlet Opening 312 Neck Section 402 Cleaning Tool 404 Base 406 Inlet Elbow 408 Nozzle 410 Body Plate 412 Neck Section 414 Arm 416 Bracket 418 Motor 420 Hose 422 Inlet Opening

Claims

NOVELTY OF THE INVENTION CLAIMS 1.- A method for cleaning a jet pump assembly of a nuclear reactor, comprising: inserting a cleaning tool into the jet pump assembly such that a front face of the cleaning tool is adjacent to an internal surface of the jet pump assembly and below a level of a first liquid in the jet pump assembly; directing a plurality of front jets of a second liquid from a plurality of front orifices onto the front face of the cleaning tool such that the plurality of front jets of the second liquid travel through the first liquid and strike the internal surface of the jet pump assembly;and maintaining a clearance distance between the front face of the cleaning tool and the inner surface of the jet pump assembly during cleaning of the jet pump assembly by actuating the second liquid from a plurality of rear holes onto a rear face of the cleaning tool in the form of a plurality of rear jets to generate a reaction force to drive the front face of the cleaning tool towards the inner surface of the jet pump assembly.

2. The method according to claim 1, further characterized in that the insertion includes connecting the cleaning tool to a curved rod and lowering the cleaning tool into a secondary inlet opening of the jet pump assembly by means of the curved rod.

3. The method according to claim 1, further characterized in that the insertion includes connecting the cleaning tool to a hose, mounting a handling tool on a flange of an inlet mixer of the jet pump assembly, and bending the hose and lowering the cleaning tool into a secondary inlet opening of the jet pump assembly by means of the handling tool.

4. The method according to claim 1, further characterized in that the direction of the plurality of front jets includes forcing the second liquid onto a neck section of an inlet mixer of the jet pump assembly.

5. The method according to claim 1, further characterized in that the direction of the plurality of frontal jets is carried out at a pressure of at least 14,061,397 kgf / m2 (20,000 pounds per square inch).

6. The method according to claim 1, further characterized in that the actuation of the second liquid from the plurality of rear orifices is carried out such that the side plates of the cleaning tool make contact with the inner surface of the jet pump assembly while the front face of the cleaning tool is separated from the inner surface of the jet pump assembly. 5 7. The method according to claim 1, further characterized in that the direction and actuation of the second liquid is carried out in such a way that the ratio of the plurality of front jets to the plurality of rear jets varies from approximately 1:1 to 1:

2.

8. The method according to claim 1, further characterized 10 because insertion and direction are performed without disassembling the jet pump assembly.

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