SE1151236A1 - Adjustable hard stoppers for restriction brackets in the nuclear reactor and methods for using them - Google Patents

Abstract

24NS2478898564-OO0239/US ADJUSTABLE HARD STOPS FOR NUCLEAR REACTOR RESTRAINERBRACKETS AND METHODS OF USING THE SAME ABSTRACT OF THE DISCLOSURE Hard stops are useable in an Operating nuclear reactor to separate and biasrestrainer brackets and inlet miXers. Hard stops include a lip clamp thatclamps to a restrainer bracket and a wedge member that biases against theinlet mixer. The wedge member and lip clamp are engaged such that the twocomponents can slide against one another to bias the restrainer bracket andinlet mixer. The lip clamp includes a clamp arm and an engagement memberto clamp opposite sides of the restrainer bracket. Ratchet assemblies maintainselective positioning various components of the hard stops. Hard stops may beused in several different numbers, positions, and conflgurations in repair ormodiñcation systems. Hard stops may be installed by determining location onan outside of a restrainer bracket for the hard stop, securing the hard stop atthe location, and biasing the hard stop between two components at the location. 24

Description

24NS2478898564-000239/US ADJUSTABLE HARD STOPS FOR NUCLEAR REACTOR RESTRAINERBRACKETS AND METHODS OF USING THE SAME BACKGROUND

[0001] Conventional boiling water reactors include a reactor pressurevessel (RPV) which surrounds a core shroud. The core shroud, in turn,surrounds a reactor core. Generally, each of the core shroud and the reactorpressure vessel are cylindrically shaped such that an outer diameter of the coreshroud is less than an inner diameter of the reactor pressure vessel. Betweena reactor pressure vessel wall and a core shroud wall is an annular space inwhich jet pump assemblies are typically located.

[0002] FIG.1 illustrates a conventional jet pump assembly 25 located inthe aforementioned annulus. As illustrated in FIG. 1, an inlet nozzle 10extending through a sidewall 15 of RPV 20 is coupled to jet jump assembly 25.Jet pump assembly 25 includes a riser pipe 30 that extends between shroud35 and sidewall 15 of RPV 20. Riser pipe 30 is coupled to two jet pumps 35Aand 35B by a transition assembly 40. Each jet pump 35A and 35B includes ajet pump nozzle 42, a suction inlet 45, an inlet mixer 50, and a diffuser 55.For example, first jet pump 35A includes a first inlet mixer 50A and second jetpump 35B includes second inlet mixer 50B. Jet pump nozzles 42 arepositioned in the suction inlets 45 that are located at a first end of inlet mixers50A and 50B. Diffusers 55 are coupled to a second end of inlet mixers 50Aand 50B by a slip joint 65. Typically, both inlet mixers 50A and 50B and diffusers 55 are formed of multiple cylindrical sections. Circumferential welds 24NS2478898564-000239/US 70 join the cylindrical sections together. A support member (riser brace) 75typically surrounds riser pipe 30 and connects to riser pipe 30 via a weld 80Which may span approximately 180 degrees around the circumference of theriser pipe 30. Inlet mixers 50A and 50B are secured to riser pipe 30 via arestrainer bracket 105.

[0003] As shown in FIG. 2, conventional restrainer bracket 105 is a yoke-like member surrounding the inlet mixer 50A at a belly band 195 of inlet mixer50A. Though not shown, a similar yoke-like restrainer bracket surroundsmixer 50B. Penetrating the restrainer bracket 105 are at least two set screws110 which press against the inlet mixer belly band 195. In FIG. 2, only one setscrew 110 is shown. Inlet mixer 50A further includes several guide ears 190arranged about, and extending from, outer edges of restrainer bracket 105. Astrengthening rib 191 may also be present between an edge and lip ofrestrainer bracket 105 to provide rigid support to the restrainer bracket 105. Amain wedge 1 15 is typically provided between a restrainer bracket pad 145 ofrestrainer bracket 105 and inlet mixer belly band 195. The main wedge 115includes a circular hole through which a wedge rod 130 passes. The wedge rod130 has a threaded top end 131 which connects to an upper support casting120 arranged above restrainer bracket 105 and a threaded bottom end whichconnects to a lower support casting 125 below restrainer bracket 105. As inletmixer 50A moves vertically or horizontally, wedge 115 may slide on wedge rod 130 and, through contact between restrainer bracket pad 145, wedge 1 15, and 24NS2478898564-OO0239/US restrainer bracket belly band 195, such motion of the inlet mixer 50A may be nondestructively opposed and reduced.

SUMMARY

[0004] Example embodiments include hard stops useable in an Operatingnuclear reactor to separate and bias related components, such as restrainerbrackets and inlet mixers. Example embodiment hard stops may include a lipclamp that clamps to a restrainer bracket in a jet pump assembly and a wedgemember that biases against an inlet mixer at the restrainer bracket. Thewedge member and the lip clamp may be moveably engaged such that the twocomponents can slide against one another in a single direction. The lip clampmay include a clamp arm and an engagement member that clamp on oppositesides of the restrainer bracket. The lip clamp may further include a ratchetassembly that engages and maintains selective positioning of the clamp armrelative to the engagement member through ratcheting action.

[0005] The lip clamp further may be moveably engaged to the wedgemember in a single direction via an engagement extension captured by a slot inthe wedge member. Relative motion along this interface may be achieved via arod that rotatably seats in a flange defined by the wedge member while matingwith the engagement extension, through a threaded surface and threaded hole.A further ratchet assembly may be attached to the rod with a correspondingratchet keep on the wedge member to maintain selective positioning of the lip clamp relative to the wedge member in the single interface direction. By 24NS2478898564-OO0239/US configuring the single interface direction as an incline with respect to a straightline distance between the inlet mixer and the restrainer bracket spanned by thehard stop, the inlet mixer and restrainer bracket may be forced apart bymoving the lip clamp in the single direction with respect to the wedge member.Example embodiment hard stops may be fabricated from reactor-compatiblematerials, including stainless steel, a nickel alloy, and a zirconium alloy.

[0006] Example embodiment hard stops may be used in several differentnumbers, positions, and conflgurations. For example, two exampleembodiment hard stops may be afñxed to a restrainer bracket at guide ears orstrengthening ribs of the restrainer bracket. Example methods of using hardstops in nuclear reactors may include determining locations for installing thehard stop to bias inlet mixers in a direction that prevents the inlet mixer fromflexing outward from the jet pump assembly, securing at least one hard stop atthe determined location, and/ or biasing the hard stop between the firstcomponent and the second component at the determined location. Forexample, the location may be at a restrainer bracket of a jet pump assembly inthe nuclear reactor, between the restrainer bracket and an inlet mixer surrounded by the restrainer bracket.

BRIEF DESCRIPTION OF THE DRAWINGS[0007] Example embodiments of the present invention will be more clearlyunderstood from the following detailed description taken in conjunction with the accompanying drawings. 24NS2478898564-OO0239/US

[0008] FIG. 1 is a view of a conventional jet pump assembly;

[0009] FIG. 2 is a view of a conventional restrainer bracket of a jet pumpassembly;

[0010] FIG. 3 is an illustration of an example embodiment system using example embodiment hard stops.

[0011] FIG. 4 is an illustration of an example embodiment hard stop.[0012] FIG. 5 is a detail view of a lip clamp useable in exampleembodiment hard stops.

[0013] FIG. 6 is a detail view of a wedge member useable in exampleembodiment hard stops.

[0014] FIG. 7 is a flow chart illustrating an example method of using hard stops in a nuclear reactor.

DETAILED DESCRIPTION[0015] Example embodiments of the invention will now be described morefully with reference to the accompanying drawings, in which exampleembodiments are shown. The invention may, however, be embodied indifferent forms and should not be construed as limited to the embodiments setforth herein. For example, although example embodiments may be describedwith reference to a Boiling Water Reactor (BWR), it is understood that exampleembodiments may be useable in other types of nuclear plants. Example embodiments are provided so that this disclosure will be thorough and 24NS2478898564-OO0239/US complete, and Will fully convey the scope of the invention to those skilled in theart. In the drawings, the sizes of components may be exaggerated for clarity.[0016] It Will be understood that When an element or layer is referred toas being "on", "connected to", or "coupled to" another element or layer, it can bedirectly on, connected to, or coupled to the other element or layer orintervening elements or layers that may be present. In contrast, When anelement is referred to as being "directly on", "directly connected to", or "directlycoupled to" another element or layer, there are no intervening elements orlayers present. As used herein, the term "and/or" includes any and allcombinations of one or more of the associated listed items.

[0017] It Will be understood that, although the terms first, second, etc.may be used herein to describe various elements, components, regions, layers,and/ or sections, these elements, components, regions, layers, and/ or sectionsshould not be limited by these terms. These terms are only used to distinguishone element, component, region, layer, and/ or section from another element,component, region, layer, and/ or section. Thus, a first element, component,region, layer, or section discussed below could be termed a second element,component, region, layer, or section Without departing from the teachings ofexample embodiments.

[0018] Spatially relative terms, such as "beneath", "beloW", "loWer","above", "upper", and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It Will be understood that the spatially 24NS2478898564-000239/US relative terms are intended to encompass different orientations of the device inuse or operation in addition to the orientation depicted in the figures. Forexample, if the device in the figures is turned over, elements described as"below" or "beneath" other elements or features would then be oriented "above"the other elements or features. Thus, the exemplary term "below" canencompass both an orientation of above and below. The device may beotherwise oriented (rotated 90 degrees or at other orientations) and thespatially relative descriptors used herein interpreted accordingly.

[0019] Embodiments described herein will refer to plan views and/ orcross-sectional views by way of ideal schematic views. Accordingly, the viewsmay be modified depending on manufacturing technologies and/ or tolerances.Therefore, example embodiments are not limited to those shown in the views,but include modifications in configuration formed on the basis ofmanufacturing processes. Therefore, regions exemplified in figures haveschematic properties and shapes of regions shown in figures exemplify specificshapes or regions of elements, and do not limit example embodiments.

[0020] As discussed above, a conventional riser pipe 30 of a jet pumpassembly 25 is connected to inlet mixers 50A and 50B via restrainer brackets105. Inventors of the present application have recognized that vertical andradial movement in inlet mixers 50A and 50B causes wear and otheroperational deficiencies in wedge 115 and other various elements interactingwith restrainer brackets 105, such that restrainer brackets 105 lose capacity to stabilize inlet mixers 50A and 50B in both horizontal/radial and vertical 24NS2478898564-000239/US directions. In this Way, although vertical movement of inlet mixer 50A and 50Bmay be permitted for thermal expansion, vibration, etc., by conventionalrestrainer brackets, this vertical movement may cause inlet mixer 50A and/ or50B to further displace horizontally away from set screws 110, flexing awayfrom riser pipe 30, causing additional vibration, damage, and/ or reduced flowefficiency through jet pumps 50A and/ or 5OB.

[0021] Example embodiments and methods discussed below uniquelyaddress these effects of conventional restrainer bracket 105 usage to achieveseveral advantages, including reduced horizontal flexing of inlet mixers withoutsignificant alteration of existing restrainer bracket structures, and/ or other advantages discussed below or not, in nuclear power plants.

Example Embodiments

[0022] FIG. 3 is an illustration example embodiment system usingexample embodiment hard stops 200 to prevent or reduce horizontal/radialflexing of an inlet mixer 50 toward restrainer bracket 105 and away fromcentral riser pipe 30 because of, or in combination with, upward or downwardvertical movement of inlet mixer 50 along a length of inlet mixer 50. As shownin FIG. 3, one or more example embodiment hard stops 200 may be seatedbetween restrainer bracket 105 and inlet mixer 50 to stabilize movementbetween restrainer bracket 105 and inlet mixer 50 and prevent or reduceadditional movement of inlet mixer 50 outward toward restrainer bracket 105.

For example, two example embodiment hard stops may be placed between 24NS2478898564-000239/US restrainer bracket 105 and inlet mixer 50 at guide ear 190 and strengtheningrib 191 of restrainer bracket 105. In this Way, if a biasing structure or force isprovided on an opposite side of inlet mixer 50 (from the direction of riser pipe30 of FIG. 1), equal, three-point support may be provided by exampleembodiment hard stops 200 equidistant on either side of a midpoint ofrestrainer bracket 105 from the opposite biasing force.

[0023] By seating against guide ears 190 and/ or strengthening rib 191,circumferential movement of example embodiment hard stops 200 aboutrestrainer bracket 105 may be reduced or prevented, preserving balancedcontact between inlet mixer 50 and hard stops 200. Additionally, by directingforce from inlet mixer 50 against one or more example embodiment hard stop200, direct force, and resulting Wear, on set screWs 110, Wedge 115, andrelated structures may be reduced or prevented. Although exampleembodiment hard stops 200 are shown in pairs, each against guide ear 190 orstrengthening rib 191, in FIG. 3, it is understood that other numbers andpositions of example embodiment hard stop 200 are equally useable.

[0024] Example embodiment hard stop 200 is shaped to seat against inletmixer 50 and guide ear 190/strengthening rib 191, and example embodimenthard stop 200 is further shaped to join to restrainer bracket 50. For example,example embodiment hard stop 200 may extend around and clamp a lip ofrestrainer bracket 105 to rigidly join to restrainer bracket 105 in vertical andhorizontal/circumferential directions. Example embodiment hard stop 200 may further abut guide ear 190 and/ or inlet mixer 50 at belly band 195, for 24NS2478898564-000239/US example, and bias against these structures. Several different fasteningmechanisms and arrangements are useable for example embodiment hardstops to provide normal, adjustable biasing at desired directions whilemaintaining desired separation between restrainer bracket 105 and inlet mixer50 to avoid the above discussed outward flexing and Wear. For example, hardstops may be attached by mechanical fasteners including bolts and screw, orwelded, to restrainer brackets 105. Similarly, although example embodimentsare discussed as joining to restrainer brackets and biasing against inlet mixers,it is understood that example embodiment hard stops may be placed in otherstructures to achieve desired separation and /or biasing.

[0025] FIG. 4 is an isometric view of an example embodiment hard stop200 as subjected to forces if used in the example system of FIG. 3. As shownin FIG. 4, example embodiment hard stop 200 may contact, and receive anormal force Lg from, restrainer bracket 105 in a radial direction. Exampleembodiment hard stop 200 may further contact, and receive a normal force L1from, a guide ear 190 or strengthening rib 191 in a circumferential direction.The sum of forces of L1 and Lg may provide a resultant normal force LR to inletmixer 50 in a direction normal to a surface of inlet mixer 50 at any verticalposition of contact between inlet mixer 50 and example embodiment hard stop200. As shown in FIG. 4, resultant force LR may be evenly distributed to inletmixer 50 from example embodiment hard stop 200. Of course, other forcesfrom other components interacting with example embodiment hard stop 200 may provide a desired resultant force. 24NS2478898564-000239/US

[0026] Specific features of example embodiment hard stop 200 aredescribed below that uniquely enable the above-described positioning andconfiguration. It is understood that other structures and functionality fromthose described below may be used in example embodiment hard stops toprovide desired connections and force distributions between restrainer bracketand inlet mixers, or any other structure. As shown in FIG. 4, exampleembodiment hard stop 200 may include an adjustable lip clamp 250 forfastening to restrainer bracket 105, so as to rigidly join hard stop 200 andrestrainer bracket 105 in vertical, horizontal/circumferential, andhorizontal/radial directions, in example embodiments. Example embodimenthard stop 200 may further include a wedge member 210 that moveably joins tolip clamp 250 and is configured to abut, at any vertical point, restrainerbracket 50 at belly band 195 or elsewhere. Lip clamp 250 and wedge member210 may movably engage at a diagonal or inclined interface 259.

[0027] Lip clamp 250 is described in connection with FIGS. 4 and 5. Lipclamp 250 may provide rigid fixing between restrainer bracket 105 andexample embodiment hard stop 200 discussed above. As shown in FIGS. 4and 5, lip clamp 250 may include two moveably engaged components, clamparm 251 and lip engagement member 252. Clamp arm 251 may include abrace 255 that extends downward in a vertical direction a length sufflcient toreach a bottom surface of a restrainer bracket 105 (FIG. 3). Brace 255 mayinclude a ledge that extends around a bottom surface of a restrainer bracket 105. Brace 255 may be shaped and sized to directly mate with a restrainer ll 24NS2478898564-000239/US bracket 105, and/ or brace 255 may be alternately configured to indirectlyengage with restrainer brackets or other features to provide a desiredpositioning / functionality for example embodiment hard stop 200.

[0028] Clamp arm 251 may be movable in lip engagement member 252 soas to provide a desired clamping functionality and/ or physical configuration,for removal and installation, for example. As shown in FIGS. 4 and 5, clamparm 251 may move by sliding in a horizontal/radial direction, in a directiontoward wedge member 210. Clamp arm 251 may slide in a clamp slot 254 thatcaptures an extension of clamp arm 251 to prevent relative movement betweenclamp arm 251 and lip engagement member 252 in other directions. Lipengagement member 252 may include a lip-receiving surface 256 into which alip or extension of restrainer bracket 105 (FIG. 3) may seat as clamp arm 251with brace 255 is biased against an opposite surface of restrainer bracket 105(FIG. 3). In this way, brace 255 and lip-receiving surface 256 may correspondto opposite surfaces of restrainer bracket 105 and clamp restrainer bracket105 between clamp arm 251 and lip engagement member 252.

[0029] Clamp arm 251 may further include a ratchet assembly 260 orother device to provide for selective movement and tensioning between clamparm 251 and lip engagement member 252. As shown in FIG. 5, ratchetassembly 260 may include several ratchet components including an adjustableratchet bolt 263, a ratchet surface 262 and corresponding ratchet keeper 261,and/ or a release 264. Ratchet bolt 263 may extend through clamp arm 251 and interface with a surface of clamp slot 254 to move or lock clamp arm 251 12 24NS2478898564-000239/US in clamp slot 254 When rotated. A ratchet surface 262 may turn With ratchetbolt 263 and ratchet against a fixed corresponding ratchet keeper 261,providing for single-way movement of ratchet bolt 263 and thus clamp arm251. For example, ratchet assembly 260 may permit single-way movement ofbolt 263 in a way that drives clamp arm 251 toward lip engagement member252 so as to provide a biasing clamp of restrainer bracket 105 (FIG. 3) betweenclamp arm 251 and lip engagement member 252. A spring-loaded release 264may permit two-way movement of ratchet bolt 262, permitting loosening orreleasing of example embodiment hard stop 200 from a restrainer bracket 105,for example. Of course, other mechanisms and structures may provideselective biasing between clamp arm 251 and lip engagement member 252,including springs, elastic members, screws and threaded holes, magnets,adhesives, etc., any of which permit lip clamp 250 to securely join to anexisting restrainer bracket.

[0030] As shown in FIG. 4, lip clamp 250 and wedge member 210 mayslidably engage about inclined interface 259, so as to permit relative movementbetween lip clamp 250 and wedge member 210 along inclined interface 259between surfaces 259a and 259b of wedge member 210 and lip clamp 250,respectively. Such engagement may be achieved in several ways, includingcapturing mating extension 253 (FIG. 5) of lip clamp 250 within acorresponding mating slot 213 (FIG. 6) of wedge member 210. Surfaces 259aand 259b and contact between mating extension 253 and corresponding mating slot 213 may otherwise be smooth to permit the two surfaces to slidably 13 24NS2478898564-000239/US move along each other. Relative movement of lip clamp 250 and wedgemember 210 in any other direction may be prohibited.

[0031] Specific relative positions of wedge member 210 and lip clamp 250may be achieved and maintained in several ways. For example, as shown inFIG. 5, mating extension 253 may further include a threaded hole 258 passingthrough mating extension 253 in a direction of inclined interface 259.Threaded rod 257 may include corresponding threads and be screwed intothreaded hole 258. Relative position between threaded rod 257 and matingextension 253, and thus lip clamp 250, may be adjusted by turning threadedrod 257 in threaded hole 258.

[0032] An interface ratchet assembly 270 may be provided on threadedrod 257 to maintain relative position between lip clamp 250 and wedge member210, permit one-way rotation of threaded rod 257 and thus one-way relativemovement of wedge member 210 and lip clamp 250, and/ or permit biasing ofexample embodiment hard stop 200 by maintaining relative position. Asshown in FIGS. 5 and 6, threaded rod 257 may include a bushing 273 shapedto engage and be rotatably captured in a corresponding flange 214 in wedgemember 210. As threaded rod 257 is turned relative to threaded hole 258, lipclamp 250 may be forced in a direction along interface 259 due to threaded rod257 being fixed to wedge member 210 through bushing 273 seating incorresponding flange 214. Rod bolt 271 and ratchet surface 272 may functionas a ratchet with wedge ratchet keeper 212, in a similar manner to ratchet assembly 260. For example, ratchet surface 272 may interface with wedge 14 24NS2478898564-000239/US ratchet keeper 212 to permit rod bolt 271 and thus threaded rod 257 to beturned in only a single direction, pushing lip clamp 205 downward alonginterface 259. A release mechanism may release or permit two-way movementin interface ratchet assembly 270.

[0033] Of course, other structures and functionality for providing desiredrelative movement, positioning, and biasing between lip clamp 250 and wedgemember 210 about interface 259 are equally useable in example embodimenthard stops 200. For example, threaded rod 257 may not be threaded butsmooth and integral with mating extension 253. Threaded rod 257 may itselftelescopically elongate when rod bolt 271 is rotated to move lip clamp 250 andwedge member 210 relative to one another. Alternatively, gearedarrangements, pins and stop holes, springs, elastic members, screws andthreaded holes, magnets, adhesives, etc. or any other fixable movingconfiguration between lip clamp 205 and wedge member 210 may enableselective relative movement and expansion of example embodiment hard stop200.

[0034] As shown in FIG. 6, wedge member 210 may include a contactsurface 215 that contacts inlet mixer 50, such as at belly band 195, in asubstantially flush manner. Wedge member 210 and contact surface 215 havea relatively long vertical length so at to contact an inlet mixer 50 even if inletmixer 50 has shifted up or down vertically or radially during operation. Wedgemember 210 and/ or lip clamp 250 in example embodiment hard stop 200 may further have a horizontal width and lateral surface configured to bear against 24NS2478898564-000239/US an external lateral structure, such as guide ear 195 or strengthening rib 191.By acting as a rigid body after being selectively biased in the above-discussedmanners, example embodiment hard stop 200 may translate forces L1, Lg, andLR among desired components such as inlet mixer 50 and restrainer bracket105. As shown in FIGS. 4-6, example embodiment hard stop may extend in aradial direction and/ or provide additional biasing force in the Lz direction,when wedge member 210 is driven downward along interface 259 relative to lipclamp 250. For example, by rotating rod bolt 271 when lip clamp is secured toa restrainer bracket 105, wedge member 210 may move downward alonginclined interface 259, such that contact surface 215 moves both verticallydownward and horizontally/radially inward. That is, a total distance betweencontact surface 215 and lip receiving surface 256 seated against a restrainerbracket 205 may be increased when wedge member 210 is drawn downward inexample embodiment hard stop 200. This increased distance may provideadditional biasing against inlet mixer 50 and/ or achieve a desired degree ofseparation between restrainer bracket 105 and inlet mixer 50. Ratchetingaction of interface ratchet assembly 270 may fix example embodiment hardstop 200 in the biased configuration to provide constant separation and forcethrough example embodiment hard stop 200.

[0035] Example embodiment hard stops may be fabricated from materialsdesigned to withstand operating conditions within a nuclear reactor andprovide material compatibility and avoid fouling for contacting pieces. For example, wedge member 210, clamp arm 251, lip engagement member 252, 16 24NS2478898564-OO0239/US ratchet bolt 263, and/ or threaded rod 275 may be fabricated of stainless steel,such as type-304 stainless steel. Various ratchet keepers 261 and 212 may befabricated of a nickel-chromium alloy, such as Inconell type X-750, to preservematerial compatibility With other hard stop element that are in constantmaterial contact With keepers 261 and 212. Or, for example, any of threadedrod 275 and ratchet bolt 263 may be fabricated from other types of stainlesssteels, such as types-304, -316 or XM-19. Still further, any parts of exampleembodiment hard stops may be fabricated from zircalloys, austenitic stainlesssteels, nickel alloys, etc. that substantially maintain their physical propertiesin high pressure/ temperature aqueous environments With elevated levels andtypes of radioactivity, depending on the desired material characteristics andmaterial compatibility among reactor elements interacting With exampleembodiment hard stops.

[0036] Example embodiment hard stops 200 are thus useable in severalharsh environments such as operating nuclear power reactors. It isunderstood that several features discussed above in connection With exampleembodiments may be reconfigured or omitted based on the specific applicationand/ or desired operational characteristics of example embodiment hard stops.While example embodiment hard stops 200 may be installed and used inaccordance With example methods discussed below, it is understood that otheruses and installation locations may be applicable With example embodiment hard stops. 17 24NS2478898564-000239/US Example Methods

[0037] Example methods include installing one or more hard stops, suchas example embodiment hard stop 200, in a jet pump of a nuclear reactor. Asshown in FIG. 7, example methods include determining S100 a location orlocations for installation of hard stop(s) within a nuclear power plant. Forexample, in S100, specific radial positions about a restrainer bracket 105 (FIG.2) may be chosen for installing hard stops to achieve a desired separationand/ or biasing between restrainer bracket 105 and inlet mixer 50, such asbetween restrainer bracket 105 and inlet mixer 50 on a side of inlet mixer 50farthest from riser pipe 30.

[0038] Example methods further include securing S200 hard stops in thedetermined location or locations. For example, using example embodimenthard stop 200, lip clamp 250 may be loosened through ratchet assembly 260such that clamp arm 251 and lip engagement member 252 fit around arestrainer bracket 105. Ratchet assembly 260 may then be selectivelytightened such that surfaces 256 and 255 seat against opposite correspondingsurfaces of restrainer bracket 105, fixing example embodiment hard stop 200to the restrainer bracket 105 at the desired location. Securing S200 may beperformed at any point when the selected location is available, including duringplant fabrication or during a maintenance outage such as a refueling outage.[0039] Example methods further include S300 biasing the secured hardstop(s) to achieve a desired level of pressure or separation between two components at the selected location. For example, using example embodiment 18 24NS2478898564-000239/US hard stop 200, threaded rod 257 may be ratcheted through interface ratchetassembly 270 so as to move lip clamp 250 and wedge member 210 into adesired relative position having a desired radial separation and/ or providing adesired level of bias between structures seating against example embodimenthard stop 200. Biasing in S300 may further include moving an externalstructure, such as inlet mixer 50 against set hard stops 200, such as With astructure positioned between inlet mixer 50 and riser pipe 30 urging inletmixer outward toward hard stops 200 set at opposite positions on restrainerbracket 105. Biasing S300 may be performed at any point, including duringplant fabrication or during a maintenance outage such as a refueling outage, orduring operation through remote-controlled mechanisms, for example.

[0040] The foregoing description is illustrative of example embodimentsand is not to be construed as limiting thereof. Those skilled in the art willreadily appreciate that many modifications are possible in the exampleembodiments without materially departing from the novel teachings andadvantages of the present inventive concept. Accordingly, all suchmodiflcations are intended to be included within the scope of present inventiveconcepts as defined in the claims. Therefore, it is to be understood that theforegoing is illustrative of various example embodiments and is not to beconstrued as limited to the specific example embodiments disclosed, and thatmodifications to the disclosed example embodiments, as well as other exampleembodiments, are intended to be included within the scope of the appended claims. 19

Claims (10)

24NS2478898564-000239/US What is claimed is:

1. A hard stop (200) useable in an Operating nuclear reactor, the hardstop (200) comprising: a lip clamp (250) configured to clamp to a restrainer bracket (105) in a jetpump assembly (25) ; and a wedge member (210) configured to bias against an inlet mixer (50) atthe restrainer bracket (105), the Wedge member (210) being moveably engaged With the lip clamp (250).

2. The hard stop (200) of claim 1, Wherein the lip clamp (250)includes a clamp arm (251) and an engagement member (252) configured toengage opposite sides of the restrainer bracket (105), and Wherein the clamparm (251) and the engagement member are moveably engaged such that therestrainer bracket (105) can be clamped between the clamp arm (251) and the engagement member (2 52).

3. The hard stop (200) of claim 1, Wherein the lip clamp (250) furtherincludes an engagement extension (253), and Wherein the Wedge member (210)deflnes an engagement slot (213) configured to capture the engagementextension (253) and permit movement of the engagement extension (253) and lip clamp (2 50) in a single direction.

4. The hard stop (200) of claim 3, further comprising: 24NS2478898564-000239/US a rod (257) configured to rotatably seat in a flange (214) defined by thewedge member (210), the rod (257) configured to mate with the engagementextension (253), wherein the rod (257) includes a threaded surface, andwherein the engagement extension (253) defines a corresponding threaded hole(258) configured to receive the rod (257) such that the engagement extension(253) and lip clamp (250) are moved in the single direction relative to the wedge member (210) by rotation of the rod (257).

5. The hard stop (200) of claim 3, wherein the single direction isinclined with respect to a shortest line between the inlet mixer (50) and therestrainer bracket (105) such that a distance between the inlet mixer (50) andthe restrainer bracket (105) spanned by the hard stop (200) changes withmovement of the engagement extension and lip clamp (250) in the single direction.

6. The hard stop (200) of claim 1, wherein at least one of the lipclamp (250) and the wedge member (210) are further configured to seat againstat least one of a guide ear (190) and strengthening rib (191) of the restrainer bracket (105).

7. A system for modifying for a jet pump assembly (25), the systemcomprising: an inlet mixer (50) to a side of a riser pipe; 21 24NS2478898564-000239/US a restrainer bracket (105) surrounding the inlet mixer (50); andat least one hard stop (200) fixed to the restrainer bracket (105) betweenthe inlet mixer (50) and the restrainer bracket (105), the hard stop (200) biasing the inlet mixer (50) toward the riser pipe.

8. The system of claim 7, Wherein the at least one hard stop (200)includes a first hard stop (200) and a second hard stop (200), and Wherein thefirst hard stop (200) and the second hard stop (200) are arranged at one of a guide ear (190) and a strengthening rib (191) of the restrainer bracket (105).

9. A method for stabilizing components in a nuclear reactorenvironment, the method comprising: determining (S100) at least one location in a nuclear reactor for installinga hard stop (200) such that the hard stop (200) biases against an inlet mixer(50) in a direction of a riser pipe; securing (S200) at least one hard stop (200) at the determined location,the hard stop (200) including a clamp conflgured to clamp to a first componentat the determined location, the hard stop (200) including a Wedge member(210) configured to bias against the inlet mixer (50), the Wedge member (210)being moveably engaged With the lip clamp (2 50); biasing (S300) the hard stop (200) against the inlet mixer (50) at the determined location. 22 24NS2478898564-OO0239/US

10. The method of claim 10, Wherein the first component is a restrainer bracket (105) of a jet pump assembly (25) in the nuclear reactor. 23