Note: Descriptions are shown in the official language in which they were submitted.
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CA 2766590 2017-02-27
Attorney Docket No. 027813-9044-CA
NUCLEAR REACTOR BELLOWS REPLACEMENT SYSTEM AND METHOD
RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Application No.
61/433,377 of the same title, filed January 17, 2011.
FIELD OF THE INVENTION
[0002] The present invention relates to methods and systems for retubing a
nuclear reactor.
SUMMARY
[0003] A nuclear reactor has a limited life of operation. For example,
second generation
CANDUTm-type reactors ("CANada Deuterium Uranium÷) are designed to operate for
approximately 25 to 30 years. After this time, the existing fuel channels can
be removed and
new fuel channels can be installed. Performing this "retubing" process can
extend the life of a
reactor. For example, retubing a CANDUTm-type reactor can extend the reactor's
life by an
additional 25 to 40 years. Without performing the retubing, a reactor that
reaches the end of its
useful life is typically decommissioned and replaced with a new reactor, which
poses significant
costs and time. Alternatively, replacement energy sources may be used to
extend the life of a
reactor. However, replacement energy sources are often more expensive than
installing a new
reactor, and can be difficult to acquire.
[0004] Nuclear reactor retubing processes include removal of a large number
of reactor
components, and include various other activities, such as shutting down the
reactor, preparing the
vault and installing material handling equipment and various platforms and
equipment supports.
The removal process can also include removing closure plugs and positioning
hardware
assemblies, disconnecting feeder assemblies, severing bellows, removing end
fittings, releasing
and removing calandria tube inserts, and severing and removing pressure tubes
and calandria
tubes. After the removal process is complete, an inspection and installation
process is typically
performed.
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[0005] During the removal process, particular procedures can be used to
improve the
efficiency of the process. For example, a stand-alone retube tooling platform
can be installed on
each face of the reactor, which is used to support operators and tools during
the retubing process.
Also, when components are removed from the reactor, they must be transported
and disposed of
properly. In some embodiments, the components are volume reduced before being
transported,
such as by cutting the components into smaller pieces.
[0006] Furthermore, during the removal process, different components may be
left on the
reactor. For example, bellows that allow the fuel channel assemblies of the
reactor to move
axially can be removed and replaced with new bellows that are pre-installed on
end fittings, or
may instead be left intact for re-use in the event they have not been subject
to unacceptable
damage or deterioration. However, by removing the bellows, less inspection and
preparation is
needed in the process of installing new end fittings and fuel channel
assemblies. Additionally,
by removing the old bellows from the reactor, concern regarding potential
damage to the old
bellows due to other operations on the reactor face is eliminated, and the
time and resources
needed to repair and qualify the old bellows for continued operation is
eliminated.
[0007] In many reactors (including CANDUTm-type reactors described above),
the bellows
of each fuel channel assembly must be severed in order to efficiently release,
remove, and
replace other components of the fuel channels, such as end fittings of the
fuel channels. Based at
least in part upon the relatively large number of such bellows in a typical
reactor and the
collective time consumed in severing each bellows, new and improved bellows
severing tools
and methods are welcome additions to the art.
[0008] Embodiments of the present invention provide fuel channel bellows
severing tools
and methods which can be used to streamline and at least partially automate
much of the process
in severing fuel channel bellows in nuclear reactors.
[0009] Some embodiments of the present invention provide a method of
removing and
replacing bellows on a nuclear reactor having a fuel channel assembly coupled
to and extending
through an aperture in a tube sheet, wherein the method comprises: severing
the bellows from a
tube of the fuel channel assembly at a ferrule adjacent the tube sheet;
removing the severed
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bellows from the tube; and installing a replacement bellows by coupling the
replacement bellows
to the tube adjacent the tube sheet.
[0010] In some embodiments, a method of removing and replacing bellows in a
nuclear
reactor having a plurality of lattice tubes is provided, and comprises:
installing a bellows
replacement cutting tool on a mobile table; cutting the bellows off with a
cutting tool; removing
that portion of the bellows cut off with the cutting tool; measuring a
remaining bellows stub left
after removing that portion of the bellows cut off with the cutting tool;
positioning a replacement
bellows for installation; and affixing the replacement bellows onto the
remaining bellows stub.
[0011] Some embodiments of the present invention provide a method of
removing bellows
from a nuclear reactor having a fuel channel assembly, the bellows including a
first flange at a
first end, a second flange at a second end and a plurality of convolutions
between the first flange
and the second flange, wherein the method comprises: removing a closure plug
from an end of
the fuel channel assembly; disconnecting a feeder assembly from the fuel
channel assembly;
removing an end fitting from the rest of the fuel channel assembly; severing
the first flange of
the bellows; severing a calandria tube; severing a pressure tube; removing the
calandria tube
through the bellows; removing the pressure tube through the bellows; after
removing the
calandria tube and the pressure tube, severing the second flange of the
bellows; and after
severing the second flange of the bellows, removing the bellows.
[0012] In some embodiments, a method of replacing bellows in a nuclear
reactor having a
plurality of lattice tubes is provided, and comprises: inserting a cutting
tool into one of the
lattice tubes; cutting through the bellows with the cutting tool; removing the
bellows with a first
ferrule and a portion of a second ferrule severed by the cutting tool;
inserting a welding tool into
that portion of the second ferrule remaining after the removing step; and
welding replacement
bellows to that portion of the second ferrule remaining after the removing
step.
[0013] Some embodiments of the present invention provide a method of
removing and
replacing bellows in a nuclear reactor having a plurality of lattice tubes,
wherein the method
comprises: installing a shield plug installation tool on a mobile table;
aligning the shield plug
installation tool to one of the plurality of lattice tubes; installing a
bellows replacement shield
plug in the one of the plurality of lattice tubes with the shield plug
installation tool; installing a
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bellows replacement cutting tool on the mobile table; cutting the bellows with
the bellows
replacement cutting tool, thereby leaving a bellows stub coupled to the one of
the plurality of
lattice tubes; measuring the bellows stub; positioning a replacement bellows
for installation;
installing welding equipment on the bellows replacement shield plug; securing
the replacement
bellows to the bellows stub; welding the replacement bellows to the bellows
stub; and inspecting
the weld.
[0014] In some embodiments, an apparatus is provided for removing bellows
from a nuclear
reactor including a plurality of lattice tubes, each of the plurality of
lattice tubes being coupled to
a respective bellows, wherein the apparatus comprises: a shaft having a
longitudinal axis, the
shaft insertable into any of the plurality of lattice tubes, and the shaft
being rotatable about the
longitudinal axis; a blade moveable between a stowed position and a deployed
position to
selectively engage and cut the bellows; a protrusion engageable with a bellows
replacement
shield plug, the apparatus operable to insert and remove the bellows
replacement shield plug into
any of the plurality of lattice tubes; and a bellows engagement mechanism
operable to engage
and remove the severed bellows from the respective one of the lattice tubes,
wherein when the
blade is in the deployed position and the shaft is inserted into the
respective one of the plurality
of lattice tubes, the deployed blade engages the bellows, and wherein upon
rotation of the shaft
about the longitudinal axis when the blade is in the deployed position and
when the shaft is
inserted into one of the plurality of lattice tubes, the blade severs the
bellows at the ferrule of the
bellows closest to the bellows replacement shield plug from the one of the
plurality of lattice
tubes.
[0015] Some embodiments of the present invention provide an apparatus for
replacing
bellows in a nuclear reactor having a plurality of lattice tubes each received
within a respective
aperture in a tube sheet, wherein the apparatus comprises: a first elongate
member extending
along a first axis; a weld head supported on the first elongate member; a
second elongate
member insertable into an aperture in the tube sheet to retain a position of
the weld head with
respect to the tube sheet; and a bellows supported on the first elongate
member adjacent the weld
head, wherein the weld head is operable to weld the bellows to a ferrule
secured to the tube
sheet.
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[0016] Other aspects of the invention will become apparent by consideration
of the detailed
description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of a CANDUTM reactor.
[0018] FIG. 2 is a cut away view of a CANDUTm-type nuclear reactor fuel
channel assembly.
[0019] FIG. 3 is a close up perspective view of a bellows, tube sheet, and
end fitting of FIG.
2.
[0020] FIG. 4 is a longitudinal cross-sectional view of one configuration
of the inboard
bellows ferrule with convolution stub of the bellows that can be used with the
tube connection
shown in FIG. 3.
[0021] FIG. 5 illustrates a bellows replacement base tool assembly
according to an
embodiment of the present invention.
[0022] FIG. 6 illustrates a bellows replacement plug insertion tool
according to an
embodiment of the present invention.
[0023] FIG. 7 illustrates a bellows replacement shield plug according to an
embodiment of
the present invention, shown in a first perspective view.
[0024] FIG. 8 illustrates the bellows replacement shield plug of FIG. 7 in
a second
perspective view.
[0025] FIG. 9 illustrates the bellows replacement shield plug of FIGs. 7
and 8, shown
installed in a lattice tube.
[0026] FIG. 10 illustrates a bellows replacement cutting tool according to
an embodiment of
the present invention, shown engaged in a fuel channel, received in a bellows
replacement shield
plug, and securing a bellows flange (convolutions of the bellows not shown for
clarity).
[0027] FIG. 11 is a first perspective view of another embodiment of a
bellows replacement
cutting tool mounted on a bellows replacement base tool assembly.
,
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[0028] FIG. 12 is a second perspective view of the bellows
replacement cutting tool of FIG.
11.
[0029] FIG. 13 shows a weld head delivery tool with weld head
according to an embodiment
of the present invention, shown with a replacement bellows attached.
DETAILED DESCRIPTION
[0030] Before any embodiments of the invention are explained in
detail, it is to be
understood that the invention is not limited in its application to the details
of construction and the
arrangement of components set forth in the following description or
illustrated in the following
drawings. The invention is capable of other embodiments and of being practiced
or of being
carried out in various ways.
[0031] FIG. 1 is a perspective of a reactor core of a CANDUTm-type
reactor 6. The reactor
core is typically contained within a vault that is sealed with an air lock for
radiation control and
shielding. A generally cylindrical vessel, known as a calandria 10, contains a
heavy-water
moderator. The calandria 10 has an annular shell 14 and a tube sheet 18 at a
first end 22 and a
second end 24. The tube sheets 18 include a plurality of apertures that each
accept a fuel channel
assembly 28. As shown in FIG. 1, a number of fuel channel assemblies 28 pass
through the tube
sheets 18 of calandria 10 from the first end 22 to the second end 24
[0032] As in the illustrated embodiment, in some embodiments the
reactor core is provided
with two walls at each end 22, 24 of the reactor core: an inner wall defined
by the tube sheet 18
at each end 22, 24 of the reactor core, and an outer wall 64 (often referred
to as a "end shield")
located a distance outboard from the tube sheet 18 at each end 22, 24 of the
reactor core. A
lattice tube 65 spans the distance between the tube sheet 18 and the end
shield 64 at each pair of
apertures (i.e., in the tube sheet 18 and the end shield 64, respectively).
[0033] FIG. 2 is a cut away view of the fuel channel assembly 28. As
illustrated in FIG. 2,
each fuel channel assembly 28 includes a calandria tube ("CT") 32 surrounding
other
components of the fuel channel assembly 28. The CTs 32 each span the distance
between the
tube sheets 18. Also, the opposite ends of each CT 32 are received within and
sealed to
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respective apertures in the tube sheets 18. In some embodiments, a CT rolled
joint insert 34 is
used to secure the CT 32 to the tube sheet 18 within the bores, although other
tube-to-sheet
joining structures and methods can instead be used. In this manner, the CTs 32
each form a first
boundary between the heavy water moderator of the calandria 10 and the
interior of the fuel
channels assemblies 28.
[0034] A pressure tube ("PT") 36 forms an inner wall of the fuel channel
assembly 28. The
PT 36 provides a conduit for reactor coolant and fuel bundles or assemblies
40. The PT 36, for
example, generally holds two or more fuel assemblies 40 and acts as a conduit
for reactor coolant
that passes through each fuel assembly 40. An annulus space 44 is defined by a
gap between
each PT 36 and its corresponding CT 32. The annulus space 44 is normally
filled with a
circulating gas, such as dry carbon dioxide, helium, nitrogen, air, or
mixtures thereof. The
annulus space 44 and gas are part of an annulus gas system typically having at
least one of two
primary functions. First, a gas boundary between the CT 32 and PT 36 provides
thermal
insulation between hot reactor coolant and fuel within the PTs 36 and the
relatively cool CTs 32.
Second, the annulus gas system provides indication of a leaking calandria tube
32 or pressure
tube 36 via the presence of moisture, deuterium, or both detected in the
annulus gas.
[0035] An annulus spacer or garter spring 48 is disposed between the CT 32
and PT 36. The
annulus spacer 48 maintains the gap between the PT 36 and the corresponding CT
32, while
allowing passage of the annulus gas through and around the annulus spacer 48.
Maintaining the
gap helps ensure safe and efficient, long-term operation of the reactor 6.
[0036] As also shown in FIG. 2, each end of each fuel channel assembly 28
is provided with
an end fitting 50 located outside of the corresponding tube sheet 18. At the
terminal end of each
end fitting 50 is a closure plug 52. Each end fitting 50 also includes a
feeder assembly 54. The
feeder assemblies 54 feed reactor coolant into or remove reactor coolant from
the PTs 36. In
particular, for a single fuel channel assembly 28, the feeder assembly 54 on
one end of the fuel
channel assembly 28 acts as an inlet feeder, and the feeder assembly 54 on the
opposite end of
the fuel channel assembly 28 acts as an outlet feeder. As shown in FIG. 2, the
feeder assemblies
54 can be attached to the end fittings 50 using a coupling assembly 56
including a number of
screws, washers, seals, and/or other types of connectors.
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[0037] The lattice tube 65 (described above) encases the connection between
the end fitting
50 and the PT 36 containing the fuel assemblies 40. Shielding ball bearings 66
and cooling
water surround the exterior the lattice tubes 65, which provides additional
radiation shielding.
[0038] With continued reference to FIGS. 2 and 3, coolant from the inlet
feeder assembly 54
flows along a perimeter channel of the end fitting 50 until it reaches a
shield plug 58. The shield
plug 58 is contained within the PT 36 and the lattice tube 65, and includes a
number of openings
that allow the coolant provided by the inlet feeder assembly to enter the end
of the PT 36.
Another shield plug 58 is located within the PT 36 and the lattice tube 65 at
the other end of the
fuel channel assembly 28, and includes similar openings that allow coolant
passing through the
PT 36 to exit the PT 36 and flow to the outlet feeder assembly 54 through a
perimeter channel of
another end fitting 50 at the opposite face of the reactor 6. As shown in FIG.
1, feeder tubes 59
are connected to the feeder assemblies 54 that carry coolant to or away from
the reactor 6.
[0039] Returning to FIGS. 2 and 3, a positioning hardware assembly 60 and
bellows 62 are
also coupled to each end fitting 50. The bellows 62 allows the fuel channel
assemblies 28 to
move axially ¨ a capability that can be important where fuel channel
assemblies 28 experience
changes in length over time, which is common in many reactors. The positioning
hardware
assemblies 60 can be used to set an end of a fuel channel assembly 28 in
either a locked or an
unlocked position. In the locked position, the end of the fuel channel
assembly 28 is fixed in an
axial position. In the unlocked position, the end of the fuel channel assembly
28 is allowed to
move axially. A tool can be used with the positioning hardware assemblies 60
to switch the
position of a particular fuel channel assembly 28.
[0040] The positioning hardware assemblies 60 are also coupled to the end
shield 64. The
positioning hardware assemblies 60 each include a rod having an end that is
received in a bore of
the respective end shield 64. In some embodiments, the rod end and the bore in
the end shield 64
are threaded.
[0041] It should be understood that although a CANDUTm-type reactor is
illustrated in FIGS.
1-3, the methods and systems described below for retubing a reactor also apply
to other types of
reactors containing similar components as illustrated in FIGS. 1-3.
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[0042] The various tools utilized in the present invention can be installed
and/or used
adjacent the calandria 10 of the nuclear reactor on a mobile table. The table
can carry and
support the tooling from lattice site to lattice site (i.e., those positions
on each side of the reactor
6 defined by the locations of the fuel channel assemblies 28 described above)
across the face of
the calandria 10. In some embodiments, the table is laterally movable in an x
direction (e.g.,
upon rails, on a cart, and the like) at a common elevation across the face of
the calandria 10,
whereas in other embodiments, the table is also vertically movable in a y
direction and/or is
movable toward and away from the reactor face in a z direction. By way of
example, in some
embodiments, the table is movable in x and z directions, and is mounted upon a
retube tooling
platform ("RTP") assembled in front of the calandria face and vertically
movable (in the y
direction) to different lattice sites. In some embodiments, the RTP is an
adjustable platform
upon which much of the fuel channel component removal operations are
performed. Also in
some embodiments, the RTP is a stand-alone machine that does not rely on
existing plant
structures for positioning or movement, and is adapted to adjustably support
one or more tables.
[0043] The tools and methods of severing and replacing fuel channel bellows
as described
and illustrated herein can be utilized under normal nuclear reactor retubing
conditions, or
alternatively as a contingency operation performed if a bellows 62 is not fit
for service. In any
case, there can be a much higher probability of needing the tools and methods
disclosed herein
when attempting to recover and reuse existing bellows, compared to replacing
all bellows during
reactor retubing. Retubing projects may require bellows replacements as a
result of damage that
either existed prior to a retubing campaign, or that was inflicted during the
campaign.
[0044] As shown in greater detail in FIG. 3, the bellows 62 includes a
bellows flange 70 at a
first end, a ferrule 72 at a second end and a plurality of convolutions 74
between the bellows
flange 70 and the ferrule 72. In some embodiments, the bellows 62 can
initially be severed at or
proximate the bellows flange 70 to separate the bellows 62 from the end
fitting 50 and/or the PT
36 to thereby permit removal of the end fitting 50 and/or the PT 36 from the
bellows 62. In such
cases, a portion of the bellows flange 70 can remain connected to the
convolutions 74 and the
ferrule 72. The severed bellows 62 can then be inspected to determine if the
severed bellows 62
can be re-used or must be replaced. If the severed bellows 62 can be re-used,
the severed
bellows 62 can be repaired (if needed), machined, and otherwise prepared for
re-attachment.
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Some possible machining processes include deburring and face-grinding, whereas
preparation
processes can include cleaning and inspection of the bellows 62.
[0045] In some embodiments, the bellows 62 are removed without inspection,
such as if a
decision has already been made to replace all of the bellows 62 in a retubing
campaign. If the
severed bellows 62 will be replaced (in such cases, or in cases in which
inspection has shown
that the bellows 62 have sustained unacceptable damage or deterioration), the
bellows 62 are
additionally severed at the ferrule 72 to permit removal of the severed
bellows 62. As shown in
greater detail in FIGS. 3 and 4, in some embodiments the ferrule 72 includes
an annular groove
76. The ferrule 72 can be cut at the groove 76 to facilitate cutting and
removal of the severed
bellows 62. Alternatively, the ferrule 72 can be cut inboard or outboard of
the groove 76 (if such
a groove exists in the ferrule 72) as desired. However, cutting at the groove
76 can speed the
severing process while at the same time providing a substantial ferrule stub
72' on which to
attach a new bellows 62 in later operations. After the ferrule 72 has been
cut, a ferrule stub 72'
can remain connected to the tube sheet 64 and/or the lattice tube 65 (part of
the ferrule stub 72'
being visible in FIG. 9).
[0046] With continued reference to FIGS. 3 and 4, in some embodiments the
ferrule 72
includes a journal ring 78 positioned and held between first and second
retaining rings 80, 82 on
the inside surface of the ferrule 72. The journal ring 78 engages a sleeve 84
which is part of the
end fitting 50, and permits the end fitting 50 to move with respect to the
ferrule 72. The journal
ring 78 and the first and second retaining rings 80, 82 are optionally removed
and replaced
during the retubing operation. Also, in other embodiments, the journal ring 78
(and therefore the
retaining rings 80, 82) are not used, or are replaced with a feature on the
inside surface of the
ferrule performing the same or similar functions as the journal ring 78 and
retaining rings 80, 82.
[0047] The bellows replacement system and method according to some
embodiments of the
present invention is comprised of two main activities. The first main activity
is severing the
bellows 62 at the ferrule 72. The second main activity is welding a
replacement bellows to the
ferrule stub 72' at or proximate the tube sheet 64.
[0048] In some embodiments of the bellows replacement system and method
according to
the present invention, all mounted tools used in the system and method are
releasably fastened to
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a base tool assembly, such as the base tool assembly 86 shown in FIG. 5. The
base tool
assembly 86 can allow for accurate positioning of all tools mounted thereon,
and itself can be
mounted to a mobile table (described in greater detail above) that is
adjustable in x, y, and/or z
directions, and that can also adjusted for pitch and yaw changes with respect
to a lattice site. As
also described above, the mobile table can be supported upon an RTP which
moves the mobile
table and anything thereon to different lattice sites across the reactor face.
[0049] Once aligned with a particular lattice site with any necessary
adjustments of a mobile
table and/or RTP, if used, the base tool assembly 86 of FIG. 5 can provide
accurate repeatable
positioning of other tools (used for bellows replacement) at the lattice site.
The illustrated base
tool assembly 86 includes hand wheels 88, 90 to adjust the position of the
base tool assembly 86
on the mobile table, and brakes 92, 94 to affix the base tool assembly 86 to
the mobile table.
[0050] FIG. 6 illustrates an example of a plug insertion tool 96 that can
be mounted on the
base tool assembly 86 of FIG. 5. The illustrated plug insertion tool 96
includes a hand crank 98,
a housing 100, and a nose 102. The crank 98 can be actuated by a user (either
locally, or
remotely using an appropriate motor drive connected thereto) to move the nose
102 along the
direction of arrow A. In some embodiments, the housing 100 remains stationary
while a
threaded shaft (not shown) telescopes a protrusion 104 of the nose 102 in the
direction of arrow
A. The nose 102 of the illustrated plug insertion tool 96 also includes a pin
having first and
second ends 106, 108, the purpose of which will be apparent below. The first
end 106 of the pin
projects from a first side of the protrusion 104 and the second end 108 of the
pin projects from a
second side of the protrusion 104, although separate pins or similar
protrusions can be attached
or defined on the nose 102 to arrive at a similar structure.
[0051] The plug insertion tool 96 is used to install and secure a bellows
replacement shield
plug (BRSP) 110 into the lattice tube 65 of a fuel channel assembly 28 in
preparation of
performing a bellows cutting operation, such as to sever the ferrule 72 of the
bellows 62 as
described above. The plug insertion tool 96 can also be used as an alignment
structure for the
cutting tool used in the bellows cutting process, and well as for removing the
BRSP 110. As an
alternative to the plug insertion tool 96 of FIG. 6, a manually-operated
bellows replacement
shield plug insertion tool can be used to handle the BRSP 100. However, due to
the relatively
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heavy weight of the BSRP 100, it is anticipated that a manually-operated
bellows replacement
shield plug insertion tool could be used with the aid of a trolley or
hoist(s).
[0052] A BRSP 110 according to an embodiment of the present invention is
shown in FIGS.
7 and 8. The BRSP 110 provides shielding from radiation that would otherwise
stream from the
calandria 10 through the lattice tube 65, and can also provide (i) an axial
reference for tools
performing bellows cutting; (ii) an axial reference for tools performing
welding of replacement
bellows; and/or (iii) radial anchoring for the either or both types of tools.
In some embodiments,
the BRSP provides shielding from radiation and one or more separate components
provide axial
reference and radial anchoring for tools. The BRSP 110 of the illustrated
embodiment includes a
first end 112, a second end 114, and a reduced-diameter shaft 116 extending
between the first
end 112 and the second end 114. The reduced diameter shaft 116 can provide
significant weight
savings for the BRSP, although in other embodiments the BSRP has no reduced
diameter portion
or is otherwise shaped as necessary to fit within the lattice tube 65.
[0053] With continued reference to the illustrated embodiment, the first
end 112 of the BSRP
includes a recess 118 and a pair of opposing slots 120 on opposite side of the
recess 118. The
recess 118 is sized to receive and mate with the protrusion 104 of the plug
insertion tool 96, and
the slots 120 are sized to receive the first and second ends 106, 108 of the
pin of the plug
insertion tool 96 in a bayonet connection (i.e., axially inserted into the
slots, followed by a
circumferential rotation of the pin to secure the BRSP 110 to the nose 102 of
the plug insertion
tool 96. Accordingly, to mount the BRSP 110 to the plug insertion tool 96, a
user inserts the
protrusion 104 of the plug insertion too 96 into the recess 118 of the BRSP
until the user is able
to twist the BRSP about its own longitudinal axis to clinch the bayonet
connection defined by the
pin of the plug insertion tool 96 within the slots 120 of the BRSP 110. When
connected to the
plug insertion tool 96, the BRSP 110 can be inserted into (or removed from)
the lattice tube 65
by operation of the hand crank 98 and/or adjustment of the base tool assembly
86 as described
above.
[0054] With reference back to FIGs. 7 and 8, the second end 114 of the
illustrated BRSP 110
includes a recess 122 and a plurality of radial projections 124. The radial
projections 124 can
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engage an interior of the lattice tube 65 to inhibit radial movement of the
BRSP 96 within the
lattice tube 65, and in some embodiments can also center the BRSP 96 within
the lattice tube 65.
[0055] An alternative embodiment of a BRSP 110' is illustrated in FIG. 9,
and is
dimensioned to extend into a lattice tube 65 and to abut a calandria side
bearing when fully
inserted in some embodiments. The BRSP 110' of FIG. 9 includes a first end
112', a second end
114' and a shaft 116' extending between the first end 112' and the second end
114'. The first
end 112' includes a recess 118' and a pair of opposing slots 120' which
substantially correspond
to the recess 118 and slots 120 of the BRSP 110 of FIGs. 7 and 8. The second
end 114' of the
BRSP 110' of FIG. 9 includes a recess 122' and a plurality of radial
projections 124', which
substantially correspond to the recess 122 and the plurality of radial
projections 124 of the BRSP
110 of FIGs. 7 and 8.
[0056] In some embodiments, an alignment tool can be secured to the plug
insertion tool of
FIG. 6. The alignment tool can provide information on alignment of the plug
insertion tool with
respect to the fuel channel (e.g., with respect to the lattice tube 65) in x,
y, pitch and yaw
orientations.
[0057] A bellows cutting tool 126 according to an embodiment of the present
invention is
shown in FIG. 10, and can be mounted to the base tool assembly 86 of FIG. 5.
The bellows
cutting tool 126 includes a head end 128 and a drive end 130. The head end 128
of the
illustrated bellows cutting tool 126 can include a parting tool 132 that is
insertable into the
bellows 62 (the convolutions 74 and bellows flange 70 of which are not shown
in FIG. 10 for
clarity), the ferrule 72 of the bellows 62, and optionally into the tube sheet
64 and calandria tube
65. One or more depth limiting rods 137 (illustrated in FIGS. 11 and 12) on
the head end 128 of
the bellows cutting tool 126 can limit the insertion depth of the head end 128
by abutment
against surfaces adjacent the lattice site, such as upon the external surface
of the lattice tube
sheet 64. The head end 128 of the bellows cutting tool 126 can also include a
clamp 134 that
selectively clamps the bellows 62 by rotation of a hand crank 133 connected
thereto. The drive
end 130 of the tool includes a drive 136, such as a servo motor, that rotates
the parting tool 132
to cut the ferrule 72. Alternatively, the bellows 65 can be severed by a
milling cutter, shears, a
laser cutter, one or more blades, a boring bar or other similar severing
mechanism.
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Attorney Docket No. 027813-9044-CA
[0058] In operation, the cutting tool 126 can be used to first secure the
bellows 62 with the
clamp 134 (e.g., by securing the clamp 134 about the bellows flange 70). With
the bellows 62
clamped in this manner, the drive 136 can be started to cause one or more
retractable blades (not
shown) at the head end 128 of the cutting tool 126 to begin rotating with the
head end 128 about
the longitudinal axis of the cutting tool 126. The blade(s) can then be
extended radially outward
into cutting engagement with the ferrule 72 by a suitable drive motor or (as
shown in FIG. 10,
and better shown in an alternative cutting tool embodiment of FIGs. 11 and 12)
a hand crank 135
mechanically connected to the retractable blade(s). After the blade(s) have
severed the ferrule
72, the blade(s) can be retracted, the drive 136 can be stopped, and the
severed bellows 62 still
attached to the cutting tool 126 via the clamp 134 can be withdrawn from the
fuel channel.
[0059] FIGS. 11 and 12 illustrate an alternative embodiment of a bellows
cutting tool 126'
that is mounted to a base tool assembly 86' similar to the base tool assembly
86 of FIG. 5. The
bellows cutting tool 126' includes a head end 128' and a drive end 130'. The
head end 128' of
the bellows cutting tool 126' can include a parting tool 132' that can be
inserted into the bellows
62 and the ferrule 72 of the bellows 62, and optionally into the tube sheet 64
and calandria tube
65. Like the embodiment of FIG. 10, the head end 128' of the bellows cutting
tool 126' can also
include a clamp 134' that selectively clamps the bellows 62. The drive end
130' of the tool
includes a drive 136', such as a servo motor, that rotates the parting tool
132' to cut the ferrule
72. The cutting tool 126' can be used to secure the bellows 62 with the clamp
134', cut through
the ferrule 72 by rotation of the parting tool 132' in response to the
operation of the drive 136',
and then safely remove the bellows 62 from the target site with the clamp 134'
in a manner
similar to that discussed above in connection with the embodiment of FIG. 10.
[0060] A weld head delivery tool 140 according to an embodiment of the
present invention is
shown in FIG. 13. The weld head delivery tool 140 can be mounted to a fixture
on the base tool
assembly 86 for being retained in a desired position in front of the subject
lattice site, or can be
retained in such a position in any other suitable manner. The weld hand
delivery tool 140 can
include a weld head 142, a rod 144 that supports the weld head 142, and a
projection 146
connected to the rod 144. The projection 146 is sized to extend into the bore
118 of the bellows
replacement shield plug 110. Replacement bellows 62 are mounted on the weld
head delivery
tool 140. The weld head delivery tool 140 further includes first and second
support shafts 148,
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CA 02766590 2012-01-16
Attorney Docket No. 027813-9044-CA
150 spaced from and substantially parallel to the rod 144. The first shaft 148
includes a first
projection 152 and the second shaft 150 includes a second projection 154. The
first and second
projections 152, 154 can extend into apertures in the tube sheet 64 for proper
orientation and
alignment of the weld head 142 with respect to the bellows ferrule 72 in
preparation for welding
the new bellows 62 in place.
[0061] The weld head delivery tool 140 can provide centering and support
for the weld head
142 and the replacement bellows 62 through the engagement between the
projection 146 and the
bore 118 and the engagement between the first and second projections 152, 154
and the apertures
in the tube sheet 64. In some embodiments, the weld head delivery tool 140
holds the
replacement bellows 62 tightly against the cut ferrule stub 72', thereby
eliminating any potential
axial gap of the weld joint.
[0062] Tools for the bellows replacement process disclosed herein can be
locally operated
from a work table as described above, and tool operation can be largely
automated in some
embodiments. Also, radiation exposure during the process can be minimal, as
personnel are only
in the vault for a limited amount of time for each fuel channel. During the
time personnel are in
the vault, there are also no exposed radioactive components.
[0063] Thus, embodiments of the present invention provide, among other
things, methods
and systems for retubing a nuclear reactor. It should be understood, however,
that the methods
and systems described above can be performed in various orders and
configurations, and that
some steps can be performed in parallel to other steps. Some steps can also be
combined or
distributed among more steps. Also, the details of the methods and systems can
be modified
according to the specific configuration of the fuel channel, and/or the
reactor being retubed.
[0064] Also, it should be noted that the embodiments described above and
illustrated in the
accompanying figures are presented by way of example only and are not intended
as a limitation
upon the concepts and principles of the present invention. As such, it will be
appreciated by one
having ordinary skill in the art that various changes in the elements and
their configuration and
arrangement are possible without departing from the spirit and scope of the
present invention as
set forth in the appended claims.
