Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHOD FOR LOCATING A CALANDRIA TUBE
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims all benefit including priority to United
States Provisional
Patent Application 62/524,330, entitled "APPARATUS AND METHOD FOR LOCATING A
CALANDRIA TUBE", and filed June 23, 2017; and Romanian Patent Application
a 2018 00139, filed February 28, 2018.
[0002] These applications are hereby incorporated by reference in their
entireties.
FIELD
[0003] The following application relates to inserting a calandria tube in a
reactor, and in
particular to an apparatus and method for inserting the calandria tube in the
reactor using an
insertion tool and a guide tool.
BACKGROUND
[0004] 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 "re-tubing" process can
extend the life of a
reactor significantly, as an alternative to decommissioning the reactor.
Nuclear reactor re-tubing
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.
[0005] After the removal process is complete, an inspection and
installation process is
typically performed. For example, tube sheets positioned at each end of the
reactor may include
a plurality of bores. Each of the plurality of bores supports a fuel channel
assembly that spans
between the tube sheets. When a fuel channel assembly is removed, each tube
sheet bore is
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inspected to ensure that the tube sheet bore is to specification and that the
tube sheet bore is
ready for insertion of a new fuel channel assembly.
[0006] After the tube sheets are confirmed to be in suitable condition, the
calandria tubes,
pressure tubes, end fittings, and other components can be re-installed into
the bores. For each
fuel channel assembly, part of this process involves rolling the end of the
calandria tube to the
tube sheet of the calandria (e.g., using a deformable calandria insert),
inserting an end fitting
body into the bore, rolling the end of the pressure tube into the end fitting
body, and inserting an
end fitting liner into the end fitting.
SUMMARY
[0007] In some embodiments, the invention provides a method of inserting a
calandria tube
in a reactor. The method includes engaging an insertion tool with an inner
diameter of the
calandria tube, inserting a portion of the calandria tube through a first
calandria tube sheet bore
via the insertion tool, inserting a guide tool into the inner diameter of the
calandria tube and
guiding a portion of the calandria tube through a second calandria tube sheet
bore via the
insertion tool and the guide tool.
[0008] The invention also provides an apparatus for locating a calandria
tube relative to a
first calandria tube sheet bore and a second calandria tube sheet bore of a
reactor. The apparatus
includes a worktable mounted on a re-tubing platform located adjacent to the
reactor, an
insertion tool mounted to the worktable and engageable with an inner diameter
of the calandria
tube through the first calandria tube sheet bore, and a guide tool engageable
with an inner
diameter of the calandria tube through the second calandria tube sheet bore.
[0009] The invention provides a method including removing a first calandria
tube from a
calandria tube bore via an insertion/removal tool and inserting a second
calandria tube into the
calandria tube bore via the insertion/removal tool.
[0010] Other aspects of the invention will become apparent by consideration
of the detailed
description and accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Various aspects of the invention will become apparent by
consideration of the
detailed description and accompanying drawings.
[0012] Figure 1 is a perspective view of a reactor core of a nuclear
reactor.
[0013] Figure 2 is a cut-away view of the fuel channel assembly.
[0014] Figure 3 is a schematic view of an insertion tool and a plurality of
support members
for a calandria tube.
[0015] Figure 4 is a schematic view of the insertion tool of Fig. 3 with a
calandria tube.
[0016] Figure 5 is a schematic view of the insertion tool and calandria
tube of Fig. 4 with a
guide tool.
[0017] Figure 6 is a schematic view of the insertion tool and the calandria
tube with an
alternative guide tool.
[0018] Figure 7 is a schematic view of the insertion tool and the calandria
tube with another
alternative guide tool.
[0019] Figure 8A is a schematic view of the insertion tool and the
calandria tube with yet
another alternative guide tool.
[0020] Figure 8B is a front view of the guide tool shown in Fig. 8A.
DETAILED DESCRIPTION
[0021] 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
accompanying drawings. The invention is capable of other embodiments and of
being practiced
or of being carried out in various ways.
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[0022] Fig. 1 is a perspective of a reactor core of a CANDUTm-type reactor
6, for example a
900MW CANDUTM reactor. Alternatively, the reactor 6 may be a 100-300MW CANDUTM
reactor, a 600MW CANDUTM reactor, a 1000MW CANDUTM reactor, or another
pressurized
heavy water reactor (PHWR). The reactor core is typically contained within a
vault that is sealed
with an air lock for radiation control and shielding. Although aspects of the
invention are
described with particular reference to the CANDUTm-type reactor 6 for
convenience, the
invention is not limited to CANDUTm-type reactors, and may be useful outside
this particular
field as well. Returning to Fig. 1, a generally cylindrical vessel, known as
the calandria 10 of the
CANDUTm-type reactor 6, 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 (referred to herein as "bores") 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.
[0023] 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
bores (i.e., in the tube sheet 18 and the end shield 64, respectively).
[0024] Fig. 2 is a cutaway view of one fuel channel assembly 28 of the
reactor core
illustrated in Fig. 1. 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 respective bores 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. 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,
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such as dry carbon dioxide, helium, nitrogen, air, or mixtures thereof One or
more annulus
spacers or garter springs 48 are disposed between the CT 32 and PT 36. The
annulus spacers 48
maintain the gap between the PT 36 and the corresponding CT 32, while allowing
passage of
annulus gas through and around the annulus spacers 48.
[0025] As also shown in Fig. 2, each end of each fuel channel assembly 28
is provided with
an end fitting assembly 50 located outside of the corresponding tube sheet 18.
Each end fitting
assembly 50 includes an end fitting body 57 and an end fitting liner 59. At
the terminal end of
each end fitting assembly 50 is a closure plug 52. Each end fitting assembly
50 also includes a
feeder assembly 54. The feeder assemblies 54 feed reactor coolant into or
remove reactor
coolant from the PTs 36 via feeder tubes 59 (Fig. 1). 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 fitting
assemblies 50 using a coupling assembly 56 including a number of screws,
washers, seals, and/or
other types of connectors. The lattice tube 65 (described above) encases the
connection between
the end fitting assembly 50 and the PT 36 containing the fuel assemblies 40.
Shielding ball
bearings 66 and cooling water surround the exterior of the lattice tubes 65,
which provides
additional radiation shielding.
[0026] Returning to Fig. 2, a positioning hardware assembly 60 and bellows
62 are also
coupled to each end fitting assembly 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
configuration that fixes the axial position, or an unlocked configuration. The
positioning
hardware assemblies 60 are also coupled to the end shield 64. The illustrated
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. Again, it should be understood that although a CANDUTm-type reactor
is illustrated in
FIGS. 1-2, the invention may also apply to other types of reactors, including
reactors having
components that are similar to those illustrated in FIGS. 1-2.
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[0027] Fig. 3 illustrates an insertion tool 110 for inserting the calandria
tube 32 into a
calandria tube bore in the tube sheets 18 (Figs. 1, 4). Specifically, the
insertion tool 110 inserts
the calandria tube 32 through a bore in a first tube sheet 18 (on a first side
of the reactor 6) and
through a bore in a second tube sheet 18 (on a second side of the reactor 6,
opposite the first
side). As shown, the insertion tool 110 is a telescoping ram including a first
support 112, a
second support 114, a telescoping arm 116, and a mounting portion 118, for
mounting the
insertion tool 110 to a worktable 100 on a re-tubing platform, located
adjacent to the reactor 6.
[0028] The first and second supports 112, 114 are spaced apart from each
other. The first
and second supports 112, 114 are mounted to the telescoping arm 116 at a
distance apart from
one another and are configured to simultaneously engage with an inner surface
of the calandria
tube 32, as shown in Fig. 4. Though schematically shown as being cylindrical,
the supports 112,
114, may be spoked or otherwise designed to engage with and support the
calandria tube 32.
Utilizing two distinct supports 112, 114 provides a cantilevered support
system, thereby
decreasing the rotational moment of the calandria tube 32 when one end 22 of
the calandria tube
32 is mounted on the tool 110.
[0029] The telescoping arm 116 is configured to extend and retract along a
longitudinal axis
120. The longitudinal axis 120 is aligned with or is parallel to a
longitudinal axis of the
calandria tube 32 so that extension of the telescoping arm 116 extends the
calandria tube 32
along its axis and retraction of the telescoping arm 116 retracts the
calandria tube 32 along its
axis. The telescoping arm 116 is fixed to the mounting portion 118. The
mounting portion 118
is movable along the worktable 100 so that the insertion tool 110 can be
aligned with various
points along the reactor face. Specifically, the insertion tool 110 is movable
to align the
telescoping arm with the bore in the first tube sheet 18.
[0030] As shown in Figs. 3-4, the worktable 100 further supports a
plurality of support
members 124. As shown, the support members 124 are spaced apart in the
longitudinal direction
of the calandria tube 32. Four support members 124 are shown, though more or
less may be used
(e.g., 1-3 support members, 5+ support members) to support the calandria tube
32 radially (i.e.,
providing a force in the radial direction of the calandria tube 32) and
further reduce the moment
of the cantilevered tube 32 and the resulting sagging of the distal end 24 of
the tube 32. The
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support members 124 may apply a force on an outer surface of the calandria
tube 32. As
depicted in Fig. 4, the support members 124 may apply forces that are spaced
apart in the
longitudinal direction of the calandria tube 32. The support members 124 may
be, for example,
hydraulically-controlled plungers, pneumatically-controlled plungers, or
electrically-controlled
solenoids.
[0031] As shown in Figs. 5-8B, a guide tool 130A-D is further provided to
control the
movement of the calandria tube 32. The guide tool 130A, as shown in Fig. 5,
extends into an
end of the calandria tube 32. Specifically, the guide tool 130 extends into
the second end 24 of
the calandria tube 32 opposite to the first end 22 through which the insertion
tool 110 extends.
The guide tool 130A shown in Fig. 5 is a cylindrical rod 132 that contacts an
inner surface of the
calandria tube 32 and includes a tapered end to improve the accuracy of
insertion.
[0032] At least the second end 24 of the calandria tube 32 is a belled end,
with a larger
diameter than that of the rest of the tube 32. The guide tool 130B shown in
Fig. 6 is a cylindrical
rod, but unlike the guide tool 130A, the guide tool 130B terminates with a
larger end for
engaging the belled end 24 of the calandria tube 32. The larger end of the
guide tool 130B may
be tapered (as shown) to improve the accuracy of insertion. When engaged with
the belled end
24, the guide tool 130B is axially aligned with the second end 24 of the
calandria tube 32.
[0033] As shown in Fig. 7, the guide tool 130C is provided with fingers 134
that extend
radially from the cylindrical body 132 to engage the inner surface of the
calandria tube 32. As
shown, the fingers 134 are offset from one another by ninety degrees, though
this may be
increased or decreased based on the density of the fingers 134. The fingers
may be made of a
resilient material to support off-center insertion of the guide tool 130C into
the calandria tube 32
yet still provide structural support to hold the calandria tube 32 relative to
the cylindrical body
132.
[0034] As shown in Figs. 8A-8B, the guide tool 130D is provided with a cam
136 fixed to
the distal end of the cylindrical body 132. The cam 136 is provided with an
egg-shaped profile
138 (Fig. 8B) and is mounted off-center to the cylindrical body 132.
Therefore, when the cam
136 is inserted into the end 24 of the calandria tube 32, rotation of the
cylindrical body 132
varies the position of the end 24 of the calandria tube 32.
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[0035] To replace a calandria tube 32, the old calandria tube 32 is removed
and the bores in
the first and second tube sheets 18 are prepared for a new calandria tube 32.
The insertion tool
110 is moved along the support platform to align the telescoping arm 116 with
a prepared bore in
the first tube sheet 18. Once aligned, the insertion tool 110 is provided with
the new calandria
tube 32. The supports 112, 114 of the insertion tool 110 are inserted into the
first end 22 of the
calandria tube 32, engaging the inner surface of the tube 32, thereby
supporting it in a
cantilevered fashion. The telescoping arm 116 extends, inserting the second
end 24 of the
calandria tube 32 towards the bore of the first tube sheet 18. To support the
tube 32 further, the
support members 124 are extended to radially support the tube 32 from below.
The support
members may use distance sensors (not shown) to determine the correct
actuation distance to
support (e.g., to support the belled end 24 at one actuated displacement and
the center of the tube
32 at a second actuated displacement). With the aforementioned alignment and
support, the
second end 24 of the calandria tube 32 is inserted through the bore of the
first tube sheet 18.
[0036] As the calandria tube 32 is moved through the bore in the first tube
sheet 18, the
second end 24 begins to sag, moving out of alignment with the bore in the
second tube sheet 18.
When the second end 24 of the calandria tube 32 is a predetermined distance
away from the
second tube sheet 18, the guide tool 130A-D is inserted through the bore of
the second tube sheet
18 to engage the second end 24 of the calandria tube 32. More specifically,
the guide tool 130
extends into the second end 24 of the calandria tube 32 to engage the inner
surface of the
calandria tube 32. The guide tool 130A-D prevents further sagging of the
calandria tube 32
between the two tube sheets 18 and aligns the tube 32 with the destination
bore in the second
tube sheet 18. The guide tool 130A-D also serves to align the calandria tube
32 with the bore of
the second tube sheet 18 in situations in which the bore in the first tube
sheet 18 is not in perfect
alignment with the bore in the second tube sheet 18.
[0037] With the guide tool 130A-D engaged with the inner surface of the
tube 132, the
insertion tool 110 continues to push the second end 24 toward the bore in the
second tube sheet
18. Certain guide tools (e.g., guide tool 130C) may additionally provide a
pulling force to aid
the pushing force of the insertion tool 110. Adjustments to the position of
the second end 24 of
the tube 32 may be effected by the guide tool 130A-D in response to sensor
outputs (e.g.,
position sensors, etc.) as the second end 24 approaches the bore of the second
tube sheet 18. For
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example, the guide tool 130D may be rotated to rotate the cam 136 relative to
the tube 32,
thereby modifying the position of the calandria tube 32 relative to the bore
of the tube sheet 18.
[0038] Once the second end 24 is safely through the second bore, additional
sensors (not
shown) verify that the tube 32 is fully inserted and properly seated. If the
calandria tube 32 is
properly located, the guide tool 130 and insertion tool 110 are disengaged
from the inner surface
of the tube 32 and are removed. The insertion tool 110 is moved to a new
location along the
worktable 100 to insert a calandria tube 32 into a different bore.
[0039] The system above is provided with a control system and a plurality
of sensors that
provide feedback regarding the position of the calandria tubes 32. Therefore,
the process can be
automated to install the tubes 32 without direct user contact, thereby
limiting human exposure
around the reactor. Further, as the process is repeated for every calandria
tube 32 (dozens to
hundreds of tubes 32 per reactor 6), the control system can use information
gathered from
previous tube installations to anticipate necessary corrections to, for
example, the insertion angle
of the tube 32, thereby improving in efficiency after each completed
insertion. Alternatively, the
process described above may be completed via human interaction to actuate the
insertion tool
110 and the guide tool 130A-D.
[0040] It should also 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.
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