U.S. patent application number 14/032550 was filed with the patent office on 2014-03-20 for jet pump stabilizer.
This patent application is currently assigned to AREVA NP Inc.. The applicant listed for this patent is AREVA NP Inc.. Invention is credited to Thomas Newland Busic, Grant Clark Jensen, Kenneth Wade Markham.
Application Number | 20140079468 14/032550 |
Document ID | / |
Family ID | 50274623 |
Filed Date | 2014-03-20 |
United States Patent
Application |
20140079468 |
Kind Code |
A1 |
Jensen; Grant Clark ; et
al. |
March 20, 2014 |
Jet Pump Stabilizer
Abstract
A jet pump stabilizer is disclosed and claimed. The stabilizer
includes a clamp body that is affixed about the riser pipe. Two
U-clamps are connected to the clamp body, each U-clamp positioned
about a jet pump mixer section. A wedge assembly is positioned
between the clamp body and each mixer pipe, cooperating with the
clamp body and U-clamps to laterally restrain the mixer sections. A
clamp ring is positioned about each mixer section and retained in
place by the U-clamps, wedge assemblies, and clamp body. A sealing
ring is moveably connected to the clamp ring such that it is biased
toward engagement with the jet pump diffuser. Seals provided on the
stabilizer engage the jet pump assembly above and below the slip
joint, preventing vibration-inducing leakage through the slip
joint.
Inventors: |
Jensen; Grant Clark; (Morgan
Hill, CA) ; Markham; Kenneth Wade; (Forest, VA)
; Busic; Thomas Newland; (Forest, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AREVA NP Inc. |
Lynchburg |
VA |
US |
|
|
Assignee: |
AREVA NP Inc.
Lynchburg
VA
|
Family ID: |
50274623 |
Appl. No.: |
14/032550 |
Filed: |
September 20, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61703734 |
Sep 20, 2012 |
|
|
|
Current U.S.
Class: |
403/188 |
Current CPC
Class: |
F04F 5/46 20130101; F04F
5/44 20130101; Y10T 403/3906 20150115; F04F 5/54 20130101 |
Class at
Publication: |
403/188 |
International
Class: |
F04F 5/44 20060101
F04F005/44 |
Claims
1. A stabilizer for a jet pump having an inlet riser pipe, two
mixers, and two diffusers, a first of the mixers being connected to
a first of the diffusers by a first slip joint, and a second of the
mixers being connected to a second of the diffusers by a second
slip joint, the stabilizer comprising: a clamp body configured to
be affixed about the jet pump riser pipe; two U-clamps, each of
said U-clamps being coupled to said clamp body, a first of said
U-clamps configured to be positioned about the first jet pump
mixer, a second of said U-clamps configured to be positioned about
the second jet pump mixer; two clamp rings, a first of said clamp
rings configured to be positioned about the first jet pump mixer
and retained by said first U-clamp, a second of said clamp rings
configured to be positioned about the second jet pump mixer and
retained by said second U-clamp; and two sealing rings, a first of
said sealing rings coupled to said first clamp ring, a second of
said sealing rings coupled to said second clamp ring.
2. The stabilizer of claim 1, further comprising two wedges, each
of said wedges being coupled to said clamp body, a first of said
wedges positioned adjacent the first jet pump mixer, a second of
said wedges positioned adjacent the second jet pump mixer.
3. The stabilizer of claim 2, wherein said first clamp ring is
further configured to be positioned adjacent to and in contact with
said first wedge, and said second clamp ring is further configured
to be positioned adjacent to and in contact with said second
wedge.
4. The stabilizer of claim 3, wherein said first wedge is
adjustable to impart a variable force against the jet pump riser
pipe and the first jet pump mixer, and said second wedge is
adjustable to impart a variable force against the jet pump riser
pipe and the second jet pump mixer.
5. The stabilizer of claim 1, wherein said first sealing ring is
moveably coupled to said first clamp ring, said first sealing ring
being biased away from said first clamp ring and into contact with
the first jet pump diffuser.
6. The stabilizer of claim 1, wherein a first subassembly defined
by said first U-clamp, said first clamp ring, and said first
sealing ring includes two sealing members.
7. The stabilizer of claim 6, wherein a first of said sealing
members is positioned to be in contact with the jet pump on a first
side of the first slip joint and a second of said sealing members
is positioned to be in contact with the jet pump on a second side
of the first slip joint,
8. The stabilizer of claim 7, wherein said first sealing member is
coupled to said first clamp ring and said second sealing member is
coupled to said first seal ring.
9. The stabilizer of claim 6, wherein said sealing members are
formed of a malleable metal material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This patent application claims the benefit of U.S.
Provisional Patent Application No. 61/703,734 filed on Sep. 20,
2012, which is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a clamp, and, more
particularly, the present invention relates to a repair device for
use, for example, with boiling water reactor jetpumps.
[0004] 2. Description of the Related Art
[0005] While the present invention may be used in a variety of
industries, the environment of a boiling water reactor (BWR)
nuclear power plant will be discussed herein for illustrative
purposes. In a BWR, a steam-water mixture is produced when reactor
coolant (water) moves upward through the core, absorbing heat
produced by the fuel. The steam-water mixture leaves the top of the
core and enters a moisture separator, where water droplets are
removed before the steam is allowed to enter the steam line. The
steam line directs the steam to the main turbine, causing it to
turn the turbine and the attached electrical generator. The steam
is then exhausted to a condenser where it is condensed into water.
The resulting water is pumped out of the condenser back to the
reactor vessel, Recirculation pumps and jet pumps allow the
operator to vary coolant flow through the core and change reactor
power.
[0006] Within the BWR vessel, core shrouds surround the core to
provide a barrier to separate the downward coolant flow through the
annulus/downcomer (the space between the core shroud and the
reactor vessel wall) from the upward flow through the core and fuel
bundles. In a typical boiling water reactor, jet pumps are located
in the downcomer and provide forced flow of coolant through the
reactor vessel in order to yield higher reactor power output than
would be possible with natural circulation. Twenty jet pumps are
located in two semicircular groups in the annular downcomer region
of the reactor. Two jet pumps and a common inlet header or riser
pipe comprise a jet pump assembly as shown in FIG. 1. Each jet pump
assembly 1 includes an inlet riser pipe 2, a short radius elbow 3
welded at the bottom of the riser pipe 2, a transition piece 4
welded to the top of the riser pipe 2, two inlet mixer assemblies
5, and two conical diffuser assemblies 6.
[0007] FIG. 2 shows a typical inlet mixer assembly 5. Each inlet
mixer assembly 5 includes an elbow 7 and associated converging
nozzle 8, a flow mixing section 9, and a gravity wedge apparatus 10
that is employed the lateral restraint of the inlet mixer 5.
[0008] Inlet risers 5 are utilized for each jet pump assembly 1 to
permit the reactor recirculation inlet nozzles to be located below
the active fuel region. This prevents significant fast neutron
exposure which could adversely affect the mechanical properties of
the nozzle penetration welds. Additionally, riser brace arms 11
provide lateral support for the upper end of the jet pump assembly
1 and also allow for the vertical differential expansion between
the riser 2 and the reactor vessel during plant heat-up and
cool-down.
[0009] The inlet mixer elbow 7 and converging nozzle 8 sections
redirect the coolant flow stream 180.degree. and increase the
velocity of the flow stream as the coolant passes through the
nozzle 8. This increase in fluid flow velocity results in lower
static pressure of the driving flow. This decreased static pressure
in the upper end of the inlet mixer 5 draws higher pressure water
from the downcomer plenum and the two flows (driving and drive are
then combined together in the mixing section 9 of the inlet mixer
5. The inlet mixer 5 interfaces with the diffuser assembly 6 at the
slip joint 12 of the jet pump. The slip joint 12 provides means to
remove the inlet mixer assembly 5 from a jet pump assembly 1 and
also accommodates the differential thermal expansion that occurs in
the jet pump assembly 1 during plant heat-up and cool-down. This
differential thermal expansion is the result of the riser pipe 2
being anchored in the low alloy carbon steel of the reactor vessel
and the differing lengths of stainless steel jet pump components.
The inlet mixer assemblies 5 are supported laterally by a
restrainer bracket 13 that is welded to the riser pipe 2. The
gravity wedge 10 of the inlet mixer and two opposing set screws
that are mounted to the restrainer bracket 13 are designed to
restrain the inlet mixer 5.
[0010] The inlet mixers 5 are subject to flow induced vibration
resulting from the mixing action of the drive and driven flow
components in the mixing section 9 of the inlet mixer 5. In
addition, unstable pressure fluctuations result from the passage of
coolant through the slip joint 12 to the lower pressure downcomer
annulus. Consequently, abnormal wear of jet pump assembly 1
components has been experienced at several BWR plants. Components
affected have been the inlet mixer 5 and diffuser collar 6 at the
slip joint location 12, and the gravity wedge 10 and interfacing
surface of the restrainer bracket 13. Isolated cracking has also
been experienced at the set screw tack welds, riser brace 11 to
riser pipe 2 weld, and short radius elbow 3 to thermal sleeve
weld.
[0011] Thus, there is a need to provide a simple mechanical device
which will minimize or limit coolant leakage at the slip joint
location and also provide supplemental structural support to the
jet pump assembly.
SUMMARY OF THE INVENTION
[0012] The jet pump stabilizer disclosed and claimed herein
restricts coolant leakage at the jet pump slip joint. A clamp body
is provided in two parts to interconnect around the jet pump riser
pipe. In this manner, it can be placed in position without removal
of any jet pump assembly components. Two U-clamps are connected to
the clamp body, each U-clamp fitted around a separate one of the
jet pump inlet mixer pipes. A wedge subassembly is positioned
intermediate the riser pipe and each mixer pipe. The wedge
assemblies impart a force to the mixer pipe in a direction that is
substantially opposite the force imparted to the mixer pipe by the
U-clamp. Thus, the mixer is restrained against movement, including
flow-induced vibration. The connections between the U-clamp and the
clamp body can incorporate mating spherical seats to accommodate
any misalignment between the two mixer pipes and the riser
pipe.
[0013] A clamp ring is provided for each jet pump mixer. Each clamp
ring is provided in two parts to interconnect around the jet pump
mixer pipe. In this manner, the clamp rings can be placed in
position without removal of any jet pump assembly components. An
outboard portion (that is, a portion away from the riser pipe) of
each clamp ring is placed between the U-clamp and the mixer pipe,
and may be mechanically connected thereto. An inboard portion (that
is, a portion towards or adjacent to the riser pipe) of each clamp
ring is placed between the wedge and the mixer pipe, and may be
mechanically connected thereto. In this manner, the clamp ring is
held in the desired position about the jet pump inlet mixer. A
seal, preferably a malleable seal, may be provided on the inner
perimeter of the clamp ring such that it is in contact with the
mixer above the slip joint. This clamp ring seal limits leakage
past the jet pump slip joint in an upward direction.
[0014] A sealing ring is attached to each clamp ring. Each sealing
ring is provided in two parts to interconnect around the jet pump
mixer pipe. In this manner, the sealing rings can be placed in
position without removal of any jet pump assembly components. Each
sealing ring is connected to its corresponding clamp ring by one or
more spring-biased connection pins, allowing movement of the
sealing ring relative the clamp ring. A seal, preferably a
malleable seal, may be provided on a lowermost portion of the
sealing ring. The springs bias the sealing ring downward, causing
the seal to contact the jet pump diffuser collar below the slip
joint. This sealing ring seal limits leakage past the jet pump slip
joint in a downward direction. Slots may be provided in the sealing
ring to accommodate the jet pump diffuser guide vanes. The relative
movement between the sealing ring and the clamp ring accommodate
any thermal expansion or contraction at the slip joint.
DESCRIPTION OF THE DRAWINGS
[0015] The present invention is described with reference to the
accompanying drawings, which illustrate exemplary embodiments and
in which like reference characters reference like elements. It is
intended that the embodiments and figures disclosed herein are to
be considered illustrative rather than restrictive.
[0016] FIG. 1 shows a typical jet pump assembly.
[0017] FIG. 2 shows a typical inlet mixer assembly.
[0018] FIG. 3 shows a slip joint clamp of the present
invention.
[0019] FIG. 4 shows a slip joint clamp subassembly of the slip
joint clamp of FIG. 3.
[0020] FIG. 5 shows a cross-sectional view of the slip joint clamp
of FIG. 3 in place on a jet pump assembly as shown in FIG. 1.
[0021] FIG. 6 shows a first clamp body of the slip joint clamp
subassembly of FIG. 3.
[0022] FIG. 7 shows a second clamp body of the slip joint clamp of
FIG. 3.
[0023] FIG. 8 shows an inlet mixer restraint assembly of the slip
joint clamp of FIG. 3 mounted at a preferred elevation on the riser
pipe of the jet pump assembly of FIG. 1.
[0024] FIG. 9 shows a stabilizing wedge system of the slip joint
clamp of FIG. 3.
[0025] FIG. 10 shows a cross-sectional view of a U-clamp
subassembly of the slip joint clamp of FIG. 3.
[0026] FIG. 11 shows the connection of one U-clamp of the slip
joint clamp of FIG. 3 to its corresponding restraint clamp body
about the inlet mixer of the jet pump assembly of FIG. 1.
[0027] FIG. 12 shows a cross-sectional view of a U-clamp pad of the
slip joint clamp of FIG. 3 in contact with the outboard clamp ring
of the slip joint clamp.
[0028] FIG. 13 shows optional stop bolts that can be used in the
slip joint clamp of FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
[0029] FIG. 3 shows a slip joint clamp 20 of the present invention,
and FIG. 4 shows a slip joint clamp subassembly 30 thereof. The
subassembly 30 includes inboard 31 and outboard 32 semicircular
clamp segments, which are joined together by a pair of slip joint
bolts 40 and bolt keepers 41 to form a circular clamp ring 33. A
seal ring 36 includes inboard 34 and outboard 35 semicircular seal
segments that are joined to the clamp ring 33 by several guide pins
37. Captive to the guide pins 37 are spring elements 38, which
collectively provide a separation force between the stationary
clamp ring 33 and the moveable seal ring 36. The seal ring 36 is
designed to move axially upward in response to the thermal growth
of the diffuser 6 relative to the inlet mixer 5. This upward axial
movement is resisted by the compressive action of the spring
elements 38.
[0030] The inboard 31 and outboard 32 semi-circular clamp segments
are configured with an opposing tongue-and-groove design to ensure
proper alignment of these two clamp segments. Additionally, slots
are provided in the seal ring 36 to allow for clearance with the
diffuser 6 guide vanes. These engineered slots are sized to
minimize slip joint coolant leakage by providing a tight fit with
the diffuser guide vanes.
[0031] Malleable metal seals 39 may be integrated into the clamp 33
and seal 36 rings to provide a more positive seal against coolant
leakage. A preferred spatial orientation of these metal seals is
depicted in the cross-sectional view of FIG. 5. The clamp ring 33
is held stationary and in the desired position on the inlet mixer 5
by the clamping action of the U-shaped clamp pads 73 and the mixer
wedge element 63 of the wedge clamp 10 components of the inlet
mixer restraint subassembly 50.
[0032] The inlet mixer restraint assembly 50 preferably includes a
right clamp subassembly 51 and a left clamp subassembly 52. FIGS. 6
and 7 show preferred right 51 and left 52 clamp bodies,
respectively. Bearing surfaces 501 of these subassemblies 51, 52
are joined together at the desired elevation on the riser pipe 2 by
a pair of clamp bolts 53 and clamp nuts 54. Clamp bolt keepers 55
are also provided to prevent loss of mechanical preload in the
bolted joint. Preferably, the design of the clamp bolts 53 and the
clamp nuts 54 incorporates spherical seats 56 that interface with
mating spherical seats 56 in the right 51 and left 52 clamp bodies.
This ensures proper clamp fit-up in the event that the centerlines
of the riser pipe 2 and attendant inlet mixers 5 are not
coplanar.
[0033] One of the clamp body portions 51, 52 may be provided with
one or more "tongue" features 57 that interface with a
corresponding pair of mating "groove" features 58 that may be
provided on the other clamp body 52, 51. This tongue-and-groove
arrangement can help ensure proper subassembly alignment and ease
of remote installation. For example, the right clamp body 51 can
incorporates a pair of tongue features 57 that interface with a
pair of mating groove features 58 of the left clamp body 52 as
shown in the illustrated embodiments of FIGS. 6 and 7. FIG. 8 shows
the inlet mixer restraint assembly 50, with connected right 51 and
left 52 clamp bodies, mounted at a preferred elevation on the jet
pump riser pipe 2.
[0034] The as-built distance between the riser pipe 2 and the inlet
mixer 5 preferably is stabilized by a system of wedges 60. A
preferred system of wedges 60 is illustrated in FIG. 9. Primary 61
and secondary 62 wedge elements bear on the wedge surfaces 59 of
the right 51 or left 52 clamp bodies and the inlet mixer wedge
element 63. As the primary 61 and secondary 62 wedge elements are
drawn closed together by virtue of the wedge bolt 64, the inlet
mixer wedge element 63 is brought to bear on the inboard clamp ring
31 of the slip joint clamp 30. The primary 61 and secondary 62
wedge elements are identical in overall size and shape. The primary
wedge 61 design accommodates the wedge bolt keeper 65 and the
bearing surface of the wedge bolt 64. The secondary wedge design 62
provides internal threads that interface with the threaded end of
the wedge bolt 64.
[0035] FIG. 9 also shows a U-clamp subassembly 70 of the restraint
assembly. The U-clamp subassembly 70 is attached to both the right
clamp body 51 and the left clamp body 52 by U-clamp bolts 71. Ends
of the U-clamp assembly 70 abut the right 51 and left 52 clamp
bodies at horizontal surfaces 502 thereof. U-clamp bolt keepers 72
are provided to prevent loosening of the associated bolts 71. As is
the case with preferably all of the mechanical fasteners in the
slip joint 30 and inlet mixer restraint clamp 50 assemblies, in a
preferred form the bolt keepers are essentially cantilever beam
elements with ratchet teeth that interface with mating ratchet
teeth integral with the fasteners. The keepers are designed to
deflect as the ratchet teeth of the bolts are rotated in a
tightening direction, and to resist rotation of the bolt in a
loosening direction. A crimp cup is another preferred form of bolt
keeper 72. In this design, the bolt includes a cup portion that
surrounds the head and fits into a counter bore. After the bolt has
been inserted and tightened, one or more locations along the cup
portion are plastically deformed or crimped outward into the
counter bore, which features a plurality of machined
semi-cylindrical depressions or partial cylindrical features. The
interference of the plastically deformed crimp collar with these
counter bore features prevents rotation of the bolt.
[0036] In order to eliminate shear stress in the U-clamp bolts 71,
pockets can be provided in the right 51 and left 52 clamp bodies.
As shown in the cross-sectional view of FIG. 10, the U-clamp 70 is
seated on a horizontal surface 504 of the clamp bodies 51, 52. A
step feature is provided at both extremities of the U-clamp 70,
which are inserted into these pockets, thus providing a substantial
bearing surface 503 to transmit loads from the U-clamp 70 into the
clamp bodies 51, 52.
[0037] FIG. 11 shows the connection of one U-clamp 70 to its
corresponding restraint clamp body 51, 52 about the jet pump inlet
mixer 5, and FIG. 12 shows a cross-sectional view illustrating a
preferred spatial arrangement of the U-clamp pad 73 in contact with
the outboard clamp ring 32 of the slip joint clamp 30. Mechanical
preload can be generated in the U-clamp 70 by advancing the U-clamp
pads 73 onto the outboard clamp ring 32 of the slip joint clamp
subassembly 30. This can be accomplished via a jack bolt 77, which
is coupled to the U-clamp pad 73 by, for example, a cap screw 78.
The forces thus imparted on the U-clamp pad 73 and the clamp ring
32 coupled with the force applied by the inlet mixer wedge 63 onto
the slip joint inboard clamp ring 31 provide the necessary friction
to maintain the slip joint clamp 30 in the desired position on the
inlet mixer 5.
[0038] FIG. 12 shows a cross-sectional view illustrating a
preferred spatial arrangement of the U-clamp pad 73 in contact with
the outboard clamp ring 32 of the slip joint clamp 20.
[0039] Optionally, in lieu of relying solely on friction to
maintain the slip joint clamp 30 in position on the jet pump inlet
mixer 5, stop bolts 75 and accompanying stop bolt keepers 76 can be
employed. As illustrated in FIG. 13, these stop bolts 75 can be
inserted into blind holes that are machined into the inlet mixer
5.
[0040] This disclosed jet pump stabilizer design restricts coolant
leakage at the jet pump slip joint 12, accommodates thermal
expansion at the slip joint 12, provides additional lateral support
to the inlet mixers 5, accommodates misalignment between the riser
pipe 2 and adjacent inlet mixers 5, and can be installed without
removal of any jet pump assembly components, such as the inlet
mixer 5.
[0041] While the preferred embodiments of the present invention
have been described above, it should be understood that they have
been presented by way of example only, and not of to limitation. It
will be apparent to persons skilled in the relevant art that
various changes in form and detail can be made therein without
departing from the spirit and scope of the invention. Thus the
present invention should not be limited by the above-described
exemplary embodiments, but should be defined only in accordance
with the following claims and their equivalents. Furthermore, while
certain advantages of the invention have been described herein, it
is to be understood that not necessarily all such advantages may be
achieved in accordance with any particular embodiment of the
invention. Thus, for example, those skilled in the art will
recognize that the invention may be embodied or carried out in a
manner that achieves or optimizes one advantage or group of
advantages as taught herein without necessarily achieving other
advantages as may be taught or suggested herein.
* * * * *