Note: Descriptions are shown in the official language in which they were submitted.
CA 2766459 2017-03-06
Attorney Docket No. 027813-9038-CA00
CALANDRIA TUBE, PRESSURE TUBE, AND ANNULUS SPACERS REMOVAL
APPARATUS AND METHOD FOR NUCLEAR REACTOR RETUBING
RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Application No.
61/433,349 titled "NUCLEAR REACTOR PRESSURE TUBE SEVERING TOOL AND
METHOD" filed January 17, 2011, and U.S. Provisional Application No.
61/433,479 titled
"CALANDRIA TUBE, PRESSURE TUBE, AND ANNULUS SPACERS REMOVAL
APPARATUS AND METHOD FOR NUCLEAR REACTOR RETUBING" filed January 17,
2011.
FIELD OF THE INVENTION
[0002] The present invention relates to methods and systems for retubing
nuclear reactors.
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] Therefore, embodiments of the present invention provide methods and
systems for
retubing a nuclear reactor. The retubing process includes a removal process of
various reactor
components. During the removal process, the existing calandria tube, pressure
tube, and annulus
spacers that separate the pressure tube and the calandria tube can be removed
as a package. To
create the removable package, the pressure tube is severed and rotated while
contained inside the
calandria tube. Rotating the pressure tube counters the sag typically found in
existing calandria
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and pressure tubes and applies a constraining load to the annulus spacers.
Thus the result is a
straighter package with constrained components that is easier to remove from
the reactor. Also,
by rotating the pressure tube as just described, the annulus spacers are
better contained within the
package during removal, which allows for easier handling and control. This
procedure
eliminates one removal step (i.e., separately removing the pressure tube from
the calandria tube),
and allows two components to be transported and disposed of as one package.
[0005] Accordingly, one embodiment of the invention provides a method of
removing a
calandria tube and a pressure tube from a calandria of a nuclear reactor as a
package during
retubing of the reactor. The method includes gripping, with a guide tool
advanced into the lattice
site from a pushing end of the reactor, at least a portion of a first diameter
of a calandria tube
contained in the lattice site, wherein the calandria tube includes a pressure
tube rotated from an
operational position to a removal position, and gripping, with a retrieval
tool advanced into the
lattice site from a receiving end of the reactor, at least a portion of a
second diameter of the
calandria tube. The method further includes pulling, with the retrieval tool,
the calandria tube to
remove the calandria tube from at least one tube sheet, and advancing, with
the retrieval tool and
the guide tool, the calandria tube and the rotated pressure tube as a package
across at least a
portion of the calandria toward the receiving end of the reactor. In addition,
the method includes
releasing the guide tool from the first diameter of the calandria tube, and
retracting the guide tool
from the lattice site at the pushing end of the reactor.
[0006] Another embodiment of the invention provides a tool for removing a
calandria tube
and a pressure tube from a calandria of a nuclear reactor as a package during
retubing of the
reactor. The tool includes a retrieval tool configured to be positioned within
a diameter of a
calandria tube contained in a lattice site, the calandria tube including a
pressure tube rotated from
an operational position to a removal position. The tool also includes at least
one gripper
positioned on the retrieval tool configured to grip at least a portion of the
diameter of the
calandria tube. In addition, the tool includes a puller positioned on the
retrieval tool and
configured to pull the calandria tube free from at least one tube sheet. The
retrieval tool is
configured to move the calandria tube and the rotated pressure tube as a
package across a
calandria.
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[0007] Still another embodiment of the invention provides a tool for
removing a calandria
tube and a pressure tube from a calandria of a nuclear reactor as a package
during retubing of the
reactor. The tool includes a guide tool configured to be positioned within a
diameter of a
calandria tube contained in a lattice site, the calandria tube including a
pressure tube rotated from
an operational position to a removal position. The tool also includes at least
one gripper
positioned on the guide tool, the at least one gripper configured to grip at
least a portion of the
diameter of the calandria tube, and a pusher positioned on the guide tool
configured to push the
calandria tube and the rotated pressure tube as a package across a calandria.
[0008] Furthermore, another embodiment of the invention provides a system
for removing a
calandria tube and a pressure tube from a calandria of a nuclear reactor as a
package during
retubing of the reactor. The system includes a retrieval tool and a guide
tool. The retrieval tool
is configured to be advanced into a lattice site including a calandria tube
and a pressure tube
rotated from an operational position to a removal position from a receiving
end of the reactor
until the retrieval tool is positioned within a first diameter of the
calandria tube, to grip at least a
portion of the first diameter of the calandria tube, to pull the calandria
tube to release the
calandria tube from at least one tube sheet, and to move the calandria tube
and the rotated
pressure tube as a package across a calandria and out of the lattice site at
the receiving end of the
reactor. The guide tool is configured to be advanced into the lattice site
from a pushing end of
the reactor until the guide tool is positioned within a second diameter of the
calandria tube, to
grip at least a portion of the second diameter of the calandria tube, and to
guide the calandria
tube and the rotated pressure tube as a package across at least a portion the
calandria toward the
receiving end of the reactor.
[0009] Still another embodiment of the invention provides a method of
removing a calandria
tube, a pressure tube, and a plurality of annulus spacers from a calandria of
a nuclear reactor
during retubing of the reactor. The method includes gripping at least a
portion of a first diameter
of the pressure tube from a pushing end of the reactor, advancing the pressure
tube across the
calandria to a receiving end of the reactor and into a flask, and sweeping the
plurality of annulus
spacers from within the calandria tube. The method also includes gripping at
least a portion of a
first diameter of the calandria tube from a pushing end of the reactor,
gripping at least a portion
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of a second diameter of the calandria tube from a receiving end of the
reactor, and advancing the
calandria tube across the calandria to the receiving end of the reactor.
[0010] Other aspects of the present invention will become apparent by
consideration of the
detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective view of a reactor core of a CANDUTm-type
nuclear reactor.
[0012] FIG. 2 is a cut-away view of a CANDUTm-type nuclear reactor fuel
channel assembly.
[0013] FIGS. 3 and 4 are perspective views of a pressure tube severing
tool according to
embodiments of the present invention.
[0014] FIG. 5 illustrates a cutting head of the pressure tube severing
tool of FIGS. 3 and 4
according to an embodiment of the present invention, shown with cutting wheels
extended.
[0015] FIG. 6 is a flow chart illustrating a method for severing a
pressure tube using the
pressure tube severing tool of FIGS. 3 and 4 according to an embodiment of the
present
invention.
[0016] FIG. 7 is a cut-away view of the cutting head of the pressure tube
severing tool of
FIG. 3 inserted inside a pressure tube.
[0017] FIG. 8 is a perspective view of a retrieval tool according to an
embodiment of the
invention.
[0018] FIG. 9 is a perspective view of a receiving guide sleeve according
to an embodiment
of the invention.
[0019] FIG. 10 is a perspective view of a pushing guide sleeve according
to an embodiment
of the invention.
[0020] FIG. 11 is a perspective view of a guide tool according to an
embodiment of the
invention.
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[0021] FIG. 12 is a perspective view of receiving tooling installed at a
receiving end of a
reactor.
[0022] FIG. 13 is a perspective view of guide tooling installed at a
pushing end of a reactor.
[0023] FIGS. 14 and 15 are flow charts illustrating a removal process for
removing a
calandria tube, a pressure tube, and annulus spacers as a single package
according to an
embodiment of the invention.
[0024] FIG. 16 is a cut-away view of the guide tool of FIG. 11 on the
pushing end of the
reactor, shown gripping a diameter of a calandria tube.
[0025] FIG. 17 is a cut-away view of the retrieval tool of FIG. 8 on the
receiving end of the
reactor, shown gripping a diameter of the calandria tube.
[0026] FIG. 18 is a cut-away view of the retrieval tool of FIG. 8 on the
receiving end of the
reactor, shown performing a first pull of a calandria tube.
[0027] FIG. 19 is a cut-away view of the guide tool of FIG. 11 on the
pushing end of the
reactor after the first pull of the calandria tube.
[0028] FIG. 20 is a cut-away view of the retrieval tool of FIG. 8 on the
receiving end of the
reactor moving the calandria tube through the receiving guide sleeve of FIG.
9.
[0029] FIG. 21 is a cut-away view of the guide tool of FIG. 11 on the
pushing end of the
reactor, shown after the calandria tube is moved through the receiving guide
sleeve of FIG. 9.
[0030] FIG. 22 is a cut-away view of the guide tool of FIG. 11 on the
receiving end of the
reactor, shown before a second pull of the calandria tube.
[0031] FIG. 23 is a cut-away view of the retrieval tool of FIG. 8 on the
receiving end of the
reactor, shown before the second pull of the calandria tube.
[0032] FIG. 24 is a cut-away view of the retrieval tool of FIG. 8 on the
receiving end of the
reactor, shown after the second pull of the calandria tube.
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[0033] FIG. 25 is a cut-away view of the guide tool of FIG. 11 on the
pushing end of the
reactor, shown after the second pull of the calandria tube.
[0034] FIG. 26 is a cut-away view of the guide tool of FIG. 11 on the
pushing end of the
reactor, shown retracting from the calandria tube.
DETAILED DESCRIPTION
[0035] 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. Also, the methods and processes described herein
can be performed
in various orders. Therefore, unless otherwise indicated herein, no required
order is to be
implied from the order in which elements, steps, or limitations are presented
in the detailed
description or claims of the present application. Also unless otherwise
indicated herein, the
method and process steps described herein can be combined into fewer steps or
separated into
additional steps.
[0036] 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 bores that 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.
[0037] FIG. 2 is a cut-away view of the fuel channel assembly 28. As
illustrated in FIG. 2,
each fuel channel assembly 28 is surrounded by a calandria tube ("CT") 32. The
CT 32 forms a
first boundary between the heavy water moderator of the calandria 10 and the
fuel bundles or
assemblies 40. The CTs 32 are positioned in the bores on the tube sheet 18. A
CT rolled joint
insert 34 within each bore is used to secure the CT 32 to the tube sheet 18.
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[0038i 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 the 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 the PT 36 and the 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 circulating gas are part of an annulus gas system. The annulus gas system
can serve two
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 an indication of a leaking CT 32 or PT 36 via
the presence of
moisture, deuterium, or both in the annulus gas.
[0039] An annulus spacer or garter spring 48 is disposed between the CT 32
and PT 36. The
annulus spacer 48 maintains the annulus space 44 between the PT 36 and the
corresponding CT
32, while allowing the passage of the annulus gas through and around the
annulus spacer 48.
Maintaining the annulus space 44 helps ensure safe and efficient long-term
operation of the
reactor 6.
[0040] As also shown in FIG. 2, an end fitting 50 is attached at the fuel
channel assembly 28
outside of the tube sheet 18 at each end 22, 24. At the front 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
fitting 50 using a coupling assembly 56 including a number of screws, washers,
seals, and/or
other types of connectors.
[0041] Coolant from the inlet feeder assembly flows along an annular
channel of the end
fitting 50 until it reaches a shield plug 58. The shield plug 58 is contained
inside the end fitting
50 and provides radiation shielding. The shield plug 58 also includes a number
of openings that
allow the coolant provided by the inlet feeder assembly to enter an end of a
PT 36. A shield plug
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58 located within the end fitting 50 at the other end of the fuel channel
assembly 28 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.
[0042] Returning to FIG. 2, 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. The positioning hardware assemblies 60 are used to set an end of a
fuel channel
assembly 28 in either a locked or an unlocked position. In a locked position,
the end of the fuel
channel assembly 28 is held stationary. In an unlocked position, the end of
the fuel channel
assembly 28 is allowed to move. A tool can be used with the positioning
hardware assemblies
60 to switch the position of a particular fuel channel assembly 28.
[0043] The positioning hardware assemblies 60 are also coupled to an end
shield 64. The
end shields 64 provide additional radiation shielding. Positioned between the
tube sheet 18 and
the end shield 64 is a lattice sleeve or tube 65. The lattice tube 65 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.
[0044] It should be understood that although a CANDUTm-type reactor is
illustrated in FIGS.
1 and 2, 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 and 2.
[0045] As described above, the reactor 6 can be retubed to extend its
useful life. The retube
process can include various steps and series of steps. For example, to prepare
for retubing, the
reactor 6 can be shut down and the reactor vault can be prepared for retubing.
A variety of
material-handling equipment, tools, supports, and systems can also be
installed and implemented
to aid the retubing process. In some embodiments, a retube tool platform
("RTP") is installed.
The RTP is an adjustable platform upon which much of the fuel channel removal
operations are
performed. One or more heavy work tables ("HWTs") can be installed and mounted
on the RTP,
which can serve as the basis for tool delivery during the removal process. The
HWTs provide a
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platform that supports retubing equipment. Various control and observation
systems can also be
installed and commissioned at this point in the process, such as a retube
control center ("RCC"),
a vault observation system ("VOS"), and a vault communication system ("VCS").
[0046] Once the reactor 6 is prepared for retubing, various initial
components can be
removed from the reactor 6, such as the closure plugs 52 and the positioning
hardware
assemblies 60. The feeder assemblies 54 can also be disconnected from the end
fittings 50.
[0047] Also, in preparation for removing the fuel channel assemblies 28,
the bellows 62 and
the PTs 36 can be severed. A pressure tube severing tool ("PTST") 70 is
illustrated in FIGS. 3
and 4. The PTST 70 can be installed adjacent a reactor face on a HWT 72. The
HWT 72 carries
and supports the PTST 70 as the PTST 70 is moved from lattice site to lattice
site across the face
of the calandria 10. The HWT 72 is laterally movable in an x direction (e.g.,
upon rails) by one
or more drives at a common elevation across the face of the calandria 10. In
some embodiments,
the HWT 72 can also be vertically movable in a y and/or a z direction by one
or more drives. In
other embodiments, however, the HWT 72 is movable in an x direction, the HWT
72 is mounted
upon a RTP assembled in front of the reactor face that is movable in the y
direction, and
additional tooling and systems (e.g., a removal pallet system) mounted on top
of the HWT 72 are
movable in the z direction.
[0048] The PTST 70 can include a cutting head 74 (see FIG. 5). The cutting
head 74 can
include a chipless tube cutter that minimizes the creation of loose
contaminated debris during the
severing, which can be difficult to control and clean. In some embodiments,
the cutting head 74
contains a plurality of (e.g., approximately three) cutting wheels 75. A drive
shaft 76 transmits
rotational energy to the cutting head 74, while a second shaft 77 (e.g.,
located inside the drive
shaft 76) can control extension of the cutting wheels 75 (see FIG. 7). This
configuration can
allow for dependant control of the cutting parameters (e.g., rotation and
extension of the cutting
wheels 75 are dependent on the same drive shaft 76). Due to the possible
hardened state of the
PT 36, cutting speeds and forces can be controlled to avoid a ragged cut edge.
[0049] In some embodiments, the cutting head 74 includes threads that
connect to the PTST
70 using a right-handed thread direction. The threads create a self-tightening
relationship
between the cutting head 74 and the PTST 70 as the cutting head 74 is rotated
to sever the PT 36.
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[0050] FIG. 6 is a flow chart illustrating a method 80 of severing a PT 36
using the PTST 70
according to one embodiment of the invention. As shown in FIG. 6, the method
80 includes
removing the shield plug 58 from a lattice site (at 81), aligning the PTST 70
with the lattice site
(at 82), and inserting the PTST 70 into the lattice site (at 83). In some
embodiments, the PTST
70 can be physically attached to the reactor 6 after being inserted into the
lattice site. For
example, clamps can be used to attach the PTST 70 to other components of the
reactor 6 for
stability (e.g., the end fittings 50).
[0051] FIG. 7 illustrates the PTST 70 inserted into a lattice site. In some
embodiments, the
PTST 70 is inserted into the lattice site until the cutting head 74 reaches a
desired distance within
the PT 36. For example, the cutting head 74 (i.e., the cutting wheels 75
located on the cutting
head 74) can be positioned approximately 24.0 inches from the end of the PT
36. Severing the
PT 36 at this location allows access to the CT 32 separate from the PT 36
(i.e., the CT 32 is
longer than the severed PT 36 contained within the CT 32). In addition, this
severing location
limits deformation of the PT during the cutting process, which eliminates the
ligament effect
sometimes seen during PT cutting. Furthermore, severing the PT 36 at this
location also contains
all of the annulus spacers 48 contained in the fuel channel assembly 28.
Therefore, the location
of the PT cut may vary based on the location and configuration of the annulus
spacers 48 in a
particular reactor.
[0052] With the cutting head 74 of the PTST 70 inserted into the lattice
site within the PT 36
at the desired position (e.g., approximately 24.0 inches from the end of the
PT 36), the cutting
wheels 75 can be extended using the second shaft 77 to engage the wheels 75
with inside
diameter of the PT 36 (at 84). Extending the cutting wheels 75 can plunge the
sharp cutting
wheels 75 into the PT 36. With the cutting wheels 75 engaged with the PT 36,
the cutting head
74 is rotated (e.g., via the drive shaft 76) (at 85). As the cutting head 74
rotates, the cutting
wheels 75 are rotated and sever the PT 36.
100531 In some embodiments, after the PT 36 is severed from the end fitting
50, the PT 36
can be rotated with respect to the CT 32 from an operational position to a
removal position to
prepare the PT 36 for removal with the CT 32 as described below (at 86). In
some cases, the
removal position is approximately 180 degrees from the operational position,
although, other
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degrees of rotation can be performed to achieve similar results. Rotating the
PT 36 to the
removal position can turn the bottom surface of the PT 36 into the top
surface, which helps
maintain the annulus spacers 48 captive, and reduces the overall bow in the
CT/PT combination.
For example, PTs 36 and CTs 32 can sag of as much as four inches over time.
These sags,
however, can be effectively cancelled by rotating the PT 36 approximately 180
degrees within
the CT 32, which creates a tube package that is significantly straighter than
either of the
individual tubes (the rotation of the sagged PT relative to the sagged CT
results in the two bows
canceling each other, and both tubes are counter bent to a relatively straight
position). A
straighter tube package reduces the forces of extraction of the CT, which
reduces damage risks to
the downstream tube sheet bore.
[0054] In some embodiments, the PTST 70 can be used to rotate the severed
PT 36. For
example, the cutting head 74 can include one or more radially extendible
grippers (e.g., shoes,
expanding split rings, bungs, wedges, cams, rotating circular grippers, or
other mechanisms for
gripping a PT 36) that extend to engage the PT 36. Once the grippers are
engaged, the cutting
head 74 can be rotated (as it is rotated during the severing process or using
a separate drive
mechanism). In other embodiments, a separate tool can be used to rotate the PT
36. For
example, in some embodiments, after the bellows 62 is cut on one end of the
reactor 6 for a
particular lattice site (e.g., using a cutting tool similar to the PTST 70),
the bellows 62 can be
rotated using the cutting tool to ensure that the bellows 62 has been properly
cut and is released
from the end fitting 50. Therefore, the bellows 62 cutting tool can be used in
a similar fashion to
rotate the PT 36.
[0055] Similarly, in some embodiments, the bellows 62 cutting tool can
rotate the end fitting
50 to verify that the bellows 62 has been cut (e.g., using radially-extendible
shoes and/or clamps
that can be engaged and disengaged from the end-fitting 50 to prevent or to
allow the end-fitting
50 to rotate as the cutting tool rotates). Rotating an end fitting 50 will
also rotate the PT 36
provided that the opposite end of the PT has already been severed. Therefore,
after the PT 36
has been severed at one end of the reactor but before the opposite end of the
PT 36 has been
severed, the bellows 62 cutting tool can be used to rotate the end fitting 50
at the opposite end of
the reactor, which also rotates the PT 36.
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[0056] Furthermore, in some embodiments, the retrieval tool 100 and/or the
guide tool 130
described below can be used to grip an end of a severed PT 36 and rotate the
PT 36 to the
removal position. For example, in some embodiments, the retrieval tool and/or
the guide tool
130 described below can use their grippers to grip and rotate the PT 36. Also,
in some
embodiments, the tools 100 and/or 130 can include a second set of grippers
that grip and rotate
the severed PT 36. It should be understood that when the tools 100 and/or 130
include a second
set of grippers for rotating the PT 36, the tools 100 and/or 130 can rotate
the PT 36 before or
after the retrieval tool and/or the guide tool 130 uses the other set of
grippers to grip the CT 32.
For example, in some embodiments, the tools 100 and 130 can grip the CT 32
before or at the
same time as gripping and rotating the severed PT 36 to ensure the CT 32
remains stationary.
[0057] In some embodiments, while the PT 36 is rotated, the CT 32 will
deflect out to the
side. For example, when the PT 36 has been rotated approximately 90 degrees,
the sag of the PT
36 will be sideways and the CT 32 will also deflect sideways (e.g., because
the PT 36 has a
slightly greater structural stiffness than that of the CT 32). The sideways
sag will disappear
when the PT 36 is rotated to its final 180 degrees. The momentary sideways sag
of the CT 32
can be a concern depending on the nominal distance between the CT 32 and
vertical reactivity
mechanisms contained in the reactor. For example, in some reactors this
distance is as small as
approximately 5/8 of an inch. In addition, the vertical reactivity mechanisms
are made from
thin-walled zirconium (much like the CTs 32) and are intended to stay in
position throughout a
retubing process. Therefore, if the sideways sag of the CT 32 is greater than
the small distance
between the CT 32 and the vertical reactivity mechanisms, the sideways sag can
damage the
vertical reactivity mechanisms.
[0058] To overcome this concern, the direction of rotation of the PTs 36
(i.e., clockwise or
counterclockwise) can be selected to avoid damage to the vertical reactivity
mechanisms. In
other embodiments, the CT 32 can be rotated in an opposite direction of the PT
36 rotation to
counteract the sideways sag. In particular, the sag of the PT 36 can be pitted
against the sag of
the CT 32 during rotation of the PT 36 so that there is little or no sideways
movement of the CT
32 as the PT 36 is rotated relative to the CT 32. To perform this synchronized
rotation, the tool
used to rotate the PT 36 can be also be configured to rotate the CT 32 in a
synchronized manner.
Alternatively, a separate tool (inserted at the same end of the reactor as the
tool used to rotate the
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PT 36) can be used to rotate the CT 32. The tool used to rotate the CT 32 can
also be configured
to pull the CT 32 free from the tube sheet 18 (similar to the retrieval tool
100 described below)
before rotating the CT 32.
[0059] After the severed PT 36 has been rotated (or before the rotation
depending on the tool
used to rotate the PT 36), the PTST 70 can be retracted from the lattice site
(at 87) and the shield
plug 58 can be reinstalled (at 88). The PTST 70 can then be positioned at
another lattice site for
PT severing (at 89) (e.g., using the HWT 72 and the RTP).
[0060] In some embodiments, the process of severing PTs 36 can be operated
in parallel on
opposite ends of the reactor 6. For example, one RTP and HWT can start from A-
row and can
be moved to sever PTs 36 down one end of the reactor 6, and a second RTP and
HWT can start
at Y-row and can be moved to sever PTs 36 up the opposite end of the reactor
6.
[0061] It should be understood that the PTST 70 can be remotely or locally
operated and can
be automated. Furthermore, the PTST 70 can be adapted to minimize any
radiation emitting
from the cutting head 74 and to support local control, maintenance, or
troubleshooting. The
PTST 70 can also be provided with one or more outboard motorized drives
configured to rotate
the PTST 70 and/or to actuate the cutting wheels 75 on the cutting head 74 as
described above.
The drives can also include override attachments that allow the drives to be
manually operated
(e.g., to recover from motor failures).
[0062] In some embodiments, the cutting head 74 may require occasional
maintenance or
replacement (e.g., after severing approximately 40 to 60 PTs 36) to ensure cut
quality
consistency and to save valuable face production time. The cutting head 74 can
be replaced
through a semi-automated sequence to minimize radiation exposure and ensure
proper
installation. When PTST cutting head maintenance or replacement is needed,
individuals (e.g.,
two tradesmen and a radiation protection qualified person) can access the PTST
70 to replace the
used cutting head 74 with a new cutting head 74 containing new cutter wheels
75. A number of
cutting head replacements may be performed during the processing of severing
all of the PTs 36
contained in a reactor (e.g., between 8 and 12 replacements). The removed used
cutting head 74
can be surveyed by qualified personnel, such as a radiation protection
qualified person, and can
be removed and bagged. The removed used cutting head 74 can be considered low
level waste
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and, in some cases, does not require a shielded container for transport to the
waste facility. In
other embodiments, the cutting head 74 can be dismantled and the cutting
wheels 75 can be
replaced rather than replacing the entire cutting head 74.
[0063] A removal pallet system (also referred to as a "pallet") can be
installed and
implemented before or after severing the PTs 36 to remove additional
components from the
reactor 6. The pallet is designed to serve as a modular base for mounting and
supporting various
tooling systems. The pallet can be mounted on a HWT and can be controlled by
one or more
workstations. In some embodiment, a first workstation is used to manipulate
shielding, and the
another workstation is used to control a rigid chain to drive and deliver end
effectors. Once
installed, the pallet can remain on the HWT for the majority of the removal
series.
[0064] After the pallet is installed, the end fittings 50 can be removed.
With the end fittings
50 removed, the severed PTS 36 and CTs 32 can be removed. However, as
described above, the
CT inserts 34 (also referred to as "CTIs") attach the CTs 32 to the tube
sheets 18 and hold the
CTs 32 in place with a rolled joint assembly. Therefore, before the CTs 32 can
be removed, the
CT inserts 34 are removed. Also, in some embodiments, the CT inserts 34 are
released before
they are removed. Once so prepared, the CT inserts 34 can be removed from the
reactor 6.
[0065] With the CT inserts 34 removed, the PTs 36 and CTs 32 can be removed
from the
reactor 6. In some embodiments, this process includes removing a single CT 32,
PT 36, and the
annulus spacers 48 placed around the PT 36 together in a single stroke from a
lattice site, placing
the entire package into a shielded flask, removing the flask from the vault,
and installing an
empty flask back onto the removal tooling. This process can be repeated as
many times as
necessary (e.g., approximately 380 to 480 times for some reactors) to remove
all of the CTs 32,
PTs 36, and annulus spacers 48 from the reactor 6. In some embodiments, a full
flask can be
transported in a separate stream to an on-site volume reduction system where
it is emptied and
returned in cue for re-installation on the removal tooling.
[0066] In some embodiments, the CTs 32, PTs 36, and annulus spacers 48 are
moved
through the calandria 10 from one end (hereinafter a "pushing end" ) to an
opposite end
(hereinafter a "receiving end") of the reactor 6. In this configuration, the
receiving end
comprises "receive" tooling and the pushing end comprises "guide" tooling. It
should be noted,
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however, that although the term "pushing" is used herein with reference to
various tools and
components of the reactor 6, the same tools and components need not
necessarily push the CTs
32, PTs 36, and annulus spacers 48, and that the CTs 32, PTs 36, and annulus
spacers 48 may
only be guided through the calandria 10 in some embodiments. Accordingly, the
term "push" is
used for ease of description only, and is intended to encompass embodiments in
which the CTs
32, PTs 36, and annulus spacers 48 are not in fact "pushed." It should also be
understood that
other tube and annulus spacer movement directions can be used to remove the
CTs 32, PTs 36,
and annulus spacers 48 from the reactor 6. Also, in some embodiments, certain
packages of the
CT 32, PT 36, and annulus spacers 48 ("CT-PT-AS") can be removed in one
direction while
other packages are removed in an opposite direction.
[0067] The CT-PT-AS removal process can be divided into automated and
manual
operations. Automated operations can be controlled remotely from the RCC, and
can include
operations that are associated with a reactor face operation with tools on a
HWT. Performing
these activities remotely is for "as low as reasonably achievable" ("ALARA")
purposes, so that
people are kept away from highly radioactive operations as much as possible.
Manual operations
can include, for example, those operations associated with hoisting and
transportation of flasks
containing removed CT-PT-AS packages.
[0068] In some embodiments, there are no or little configuration changes of
the RTPs or the
HWTs before the CT-PT-AS removal process begins, and most of the tooling used
in the
previous series (e.g., CT insert release and removal) can be re-used in this
series of steps. For
example, any front extensions installed on the front of HWTs in previous
series can be retained
and the pallet, a lattice sleeve/shield plug insertion and removal tool ("LS-
SPIRT"), a sleeve
carriage, and a vision system on both reactor faces can be re-used from
previous series. These
common features benefit ALARA and critical path time by eliminating the need
to remove,
install, and commission new tools.
[0069] Transition into the CT-PT-AS removal series of steps can involve
installing and
commissioning one or more accessory tools onto the pallet on the RTP on both
the pushing end
and the receiving end of the reactor 6. These accessory tools are typically
mechanical sub-
assemblies that perform specialized functions in the CT-PT-AS removal series
of steps. The
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accessory tools are designed to be moved on one or more floor trolleys, and
hoisted by one or
more vault cranes. The accessory tools required for the CT-PT-AS removal
series can include a
flask located at the receiving end, a retrieval tool located at the receiving
end, a guide sleeve
located at the receiving end, a guide tool located at the pushing end, and a
guide sleeve located at
the pushing end, each of which are described in more detail below. It should
be understood that
when the term "receiving" or "pushing" is used added to the name of particular
tooling or
equipment, it designates a location of the tooling or equipment. For example,
the "receiving"
RTP indicates the RTP located on the receiving end of the reactor 6.
Similarly, the "pushing"
RTP indicates the RTP located on the pushing end of the reactor 6.
[0070] There are various benefits to removing the CT-PT-AS together in a
single stroke from
the reactor as compared with removing the PTs 36 and CTs 32 separately. First,
the possibility
of loose annulus spacers 48 is reduced or eliminated. This can be important
when the annulus
spacers 48 are made from material that attains a highly radioactive state
after use in the reactor.
For example, annulus spacers 48 constructed from Inconel are many times more
radioactive than
annulus spacers 48 made from zirconium after use. Therefore, if Inconel
annulus spacers 48
become loose, individuals could be exposed to high radiation, and there would
be a loss of
critical path time to recover the spacers 48. When the PT 36 is separately
removed from the CT
32, loose annulus spacers 48 can be inherently generated. However, this
problem is eliminated
by keeping the PT 36 together with the CT 32, so that the CT 32 and the PT 36
trap the annulus
spacers 48. Furthermore, as described above, by rotating the severed PT 36
from an operational
position to a removal position, a load is induced on the annulus spacers due
to the difference in
direction of sag between the PT 36 and the CT 32 because the sag of the PT 36
has been rotated
to oppose the sag of the CT 32, which provides more assurance that the spacers
remain trapped.
In other embodiments, the annulus spacers 48 may be contained by inserting a
ring of material
that caps or fits into the annulus gap between the PT 36 and the CT 32, hence
forming a vessel to
trap the annulus spacers 48. As described below, rotating the PT 36 also
straightens the CT-PT-
AS package by counteracting the sag of both the CT 32 and the PT 36. Thus, the
straighter CT-
PT-AS is easier to remove from the reactor 6.
[0071] Volume reduction is also achieved by leaving the PT 36 inside the CT
32 during and
after the removal process. Leaving the PT 36 inside the CT 32 decreases the
traffic of flasks into
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and out of the vault because fewer flasks are needed to remove the CT-PT-AS
packages than if
the PTs 36 and CTs 32 were removed separately. Also, because the PTs 36 are
retained in the
CTs 32, which decreases the amount of removed components that have to be
disposed of, less
volume reduction is needed to arrive at a particular volume of radioactive
material to dispose of.
Furthermore, when volume reduction is performed outside of the vault rather
than in the vault,
additional benefits are realized. For example, the design of tooling in the
vault is simplified
because in-vault volume reduction equipment does not have to be considered.
Also, by using
volume reduction systems located outside of the vault, such systems can be
installed,
commissioned, production operated, maintained, and removed off of the critical
path.
Furthermore, volume reduction systems can be set up in a dedicated Zone 3
facility, which can
be used at a reactor site or between reactor units and can be maintained or
refurbished without
moving to another facility. The design of volume reduction systems external to
vaults can also
be optimized for process efficiency and reliability because the systems are
not restricted in size,
weight, and cycle time due to vault constraints. Fully installed and
commissioned backup
volume reduction systems can also be used, which help ensure little or no
critical path time is
wasted in troubleshooting or replacing a volume reduction system.
[0072] Removing the CTs 32 and PTs 36 together also reduces the number of
removals from
the calandria by half, which directly reduces critical path time. Also, the
design of removal
tooling in the vault is simplified because such tooling only needs to consider
CT removal, and
does have to consider PT removal separately.
[0073] As described in detail above, to prepare for removing a CT-PT-AS
package, the PT
36 can be severed. During this severing, the PT 36 can be severed, for
example, approximately
two feet inboard of the end fitting 50, and the remaining PT 36 can be rotated
from an
operational position to a removal position. As previously noted, by rotating
the PT 36, the sag of
the PT 36 (typical in existing PTs 36 used for a period of time) opposes the
sag of the CT 32
(also typical in existing CTs 32 used for a period of time), which nearly
straightens both out. In
some embodiments, the result is a relatively small upward hump of the CT 32,
because the PT 36
has a slightly greater structural stiffness than that of the CT 32.
Straightening the CT 32 makes it
is easier to remove the CT-PT-AS package from the lattice site. Specifically,
clearing the CT 32
from the bore of the tube sheet 18 and other horizontal components installed
in the reactor is
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easier and less likely to cause damages to other components when the CT 32 is
as straight as
possible.
[0074] After the end fittings 50 are removed (e.g., with the two-foot stub
of the PT 36
attached), the ends of the remaining PT 36 sit inward (e.g., approximately two
feet) from either
end of the CT 32. This configuration allows grippers from removal tooling to
access a diameter
of the CT 32 at each end of the CT 32. Cutting the PT 36 shorter in this
manner also decreases
the overall influence of the sag of the PT 36 so that the residual upward hump
in the resulting
CT-PT-AS package is smaller.
[0075] In some embodiments, once the CT-PT-AS packages are ready to be
removed, the
arrangement of tools and the presence of feeder pipe cantilever supports that
were not removed
can dictate a flow of work across the reactor face. However, in other
embodiments, for planning
and monitoring purposes, the order in which the CT-PT-AS packages are removed
from lattice
sites is systematic (as opposed to a random order). For example, in some
embodiments, there are
two removal order options available that are equally efficient. The first
removal order option
progresses along rows to the left or to the right and then up or down as rows
are completed. The
second removal order option progresses along columns up or down and then to
the left or to the
right as each column is completed. In some embodiments, progressing along rows
can be more
efficient because the HWTs may be more efficient at moving to the next lattice
site than the
RWT platform, and the RWT platform is not moved with every flask change using
the first
removal order option.
[0076] FIG. 8 is a perspective view of a retrieval tool 100 according to an
embodiment of the
invention. The retrieval tool 100 includes an attachment 102 that attaches to
the end of a rigid
push pull chain (e.g., a rigid push pull chain such as that manufactured by
Serapid Inc.) on the
pallet. As will be described in greater detail below, the retrieval tool 100
advances through the
inside of a flask, a receiving guide sleeve, a receiving CT bell, and into a
CT 32 a small distance
from the receiving end of the reactor 6. The retrieval tool 100 also includes
one or more grippers
104 that grip a diameter of the CT with enough traction force to allow the CT
32 to be pulled one
or more times to release the CT 32 from the reactor 6. The grippers 104 can
include shoes,
expanding split rings, bungs, wedges, cams, rotating circular grippers, or
other mechanisms for
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Attorney Docket No. 027813-9038-CA00
gripping a portion of the CT 32. In some embodiments, the retrieval tool 100
includes two rows
of grippers, which improves traction forces by a factor of two. The additional
traction force can
assure that the retrieval tool 100 is able to perform a first pull on the CT
32 without slipping
under nominal conditions of released joints holding the CT 32 in place. If
slippage occurs,
however, a guide tool (described below) can be used to provide pushing
assistance to remove the
CT 32. As shown in FIG. 8, the retrieval tool 100 also includes an actuator
105 for the grippers
104.
[0077] The illustrated retrieval tool 100 also incorporates a puller
106 that can generate
forces sufficient for one or more pulls on the CT 32 to counteract the nominal
conditions of the
released joints holding the CT 32 in place. The reaction force generated by a
first pull can be
directed into a guide sleeve positioned at the receiving end of the reactor,
which in turn can
direct the reaction force onto the outboard surface of the receiving tube
sheet 18. In some
embodiments, the reaction force generated by subsequent pulls on the CT 32 can
be directed to a
brake mechanism in the flask receiving removed CT-PT-AS packages.
[0078] In some embodiments, the retrieval tool 100 can use a water-
hydraulic system
mounted on the pallet to perform the gripping and pulling operations. Water
can be used in case
there is a leak from the tooling to the reactor, in which case water will not
harm the reactor other
permanent reactor components (i.e., leaked water evaporates, unlike hydraulic
oil which would
need to be cleaned up and would tend to leave a residue). The retrieval tool
100 can maintain its
grip of the CT 32 as the retrieval tool 100 is pulled out of the lattice side
by the rigid push pull
chain. The retrieval tool 100 can also retract clear of the flask receiving a
removed CT-PT-AS
package, and can be parked inside the rigid push pull chain drive unit. In
some embodiments,
the retrieval tool 100 uses separate water-hydraulic lines for operating the
grippers 104 and the
pullers 106, which allows the grippers 104 and the pullers 106 to be
controlled independently.
This independence allows the retrieval tool 100 to perform second and
subsequent pulls, without
requiring that the grippers 104 disengage from the CT 32 to reset the puller
106. The grippers
104 and the puller 106 can be operated by an automated control system during
production. They
can also be operated by manual override as needed.
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[0079] The retrieval tool 100 can be designed to be maintenance free during
a re-tube outage,
but may require maintenance in between re-tube outages. It should be
understood that multiple
retrieval tools 100 can be used as needed, and that some retrieval tools 100
can be used as spares
or for training.
[0080] FIG. 9 is a perspective view of a guide sleeve 110 positioned at the
receiving end of
the reactor according to an embodiment of the invention. The receiving guide
sleeve 110 guides
the end of the CT 32 to protect the receiving tube sheet bore from damage as a
CT-PT-AS
package is removed. The receiving guide sleeve 110 also accommodates the
larger diameter bell
sections of the CT 32 as they pass out of the receiving tube sheet 18. In
addition, the receiving
guide sleeve 110 can provide a hard stop that interfaces with the retrieval
tool 100 for the first
pull on the CT 32 and directs the force generated by the pull through the
outboard face of the
receiving tube sheet 18. The receiving guide sleeve 110 can attach to a
compliant mount on a
sleeve carriage (see FIG. 12). In some embodiments, the receiving guide sleeve
110 is
approximately 4 feet long and 6 inches in diameter, and weighs approximately
50 pounds.
[0081] With continued reference to the illustrated receiving guide sleeve
embodiment of
FIG. 9, a guide mechanism 112 is located at the front of the receiving guide
sleeve 110, such that
when the receiving guide sleeve 110 is installed into a lattice site, the
guide mechanism 112
becomes located just outboard of the receiving tube sheet 18. The guide
mechanism 112 can be
designed with rollers that can be radially contracted onto a diameter of the
CT 32 or expanded
from the diameter of the CT 32. This contraction can be used to support a
minor diameter of the
CT 32 for protection of the receiving tube sheet 18 while the CT-PT-AS package
is being
removed. The reaction loads from the guide mechanism 112 can be passed onto
the inboard
bearing of the lattice site. The rollers can also be expanded to accommodate
the larger CT bell
sections when they pass through the guide mechanism 112. The rollers can also
be used to
promote a frictionless contact between the receiving guide sleeve 110 and the
CT-PT-AS
package and to avoid wear issues.
[0082] Expansion and contraction of the guide mechanism 112 can be achieved
by axially
compressing or releasing the body of the receiving guide sleeve 110. This can
be performed by
the z-axis of the pallet, which can advance to axially compress the body of
the receiving guide
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sleeve 110 against the outboard face of the receiving tube sheet 18, or
retract from the body of
the receiving guide sleeve to release the body. This operation can be achieved
by an automated
system for ALARA purposes.
[0083] As also shown in the illustrated embodiment of FIG. 9, the receiving
guide sleeve 110
includes an internal hardstop 114. The hardstop 114 can be integral with the
guide mechanism
112 and can enable the puller 106 on the retrieval tool 100 to direct its
reaction force to the
outboard surface of the receiving tube sheet 18 (see FIGS. 12-13, described in
greater detail
below). For ALARA purposes, installation and removal of the receiving guide
sleeve 110 from a
lattice site can be fully automated through advance and retract operations of
the pallet with a
sleeve carriage, which keeps individuals away from potential open radiation
beams.
[0084] The receiving guide sleeve 110 can be designed to be maintenance
free during a re-
tube outage, but may require maintenance between re-tube outages. In some
embodiments, the
above-described roller mechanism undergoes inspection with every flask change
to assure proper
function is maintained. The receiving guide sleeve 110 can be removed from a
sleeve carriage
with relative ease for maintenance purposes. Again, it should be understood
that multiple
receiving guide sleeves 110 can be used as needed, and that some sleeves 110
can be used as
spares or for training.
[0085] FIG. 10 is a perspective view of a guide sleeve 120 positioned at
the pushing end of
the reactor according to an embodiment of the invention. The pushing guide
sleeve 120 guides
the body of a guide tool, such that its trajectory into the calandria 10 is
straight. The pushing
guide sleeve 120 also prevents the guide tool from making contact with the
pushing end tube
sheet 18. The pushing guide sleeve 120 can be attached to a complaint mount on
a sleeve
carriage (see FIG. 8). The compliant mount makes it easier to install or
remove the pushing
guide sleeve 120 from the lattice site without binding because the pushing
guide sleeve 120 can
be deflected slightly sideways, upward, and/or downward and is slightly angled
to account for
misalignments. In some embodiments, the pushing guide sleeve 120 is
approximately 4 feet long
and 6 inches in diameter, and weighs approximately 50 pounds.
[0086] As shown in FIG. 10, the illustrated pushing guide sleeve 120
includes guide rollers
122 to obtain nearly frictionless contact with the guide tool. The illustrated
rollers 122 are
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located at the front of the pushing guide sleeve 120. Therefore, when the
sleeve 120 is installed
into the lattice site, the rollers 122 are located just outboard of the
pushing end tube sheet 18.
The rollers 122 can be configured to support the body of the guide tool so
that it clears and
prevents damage to the tube sheet 18. Support loads can also react against the
inboard bearing of
the lattice site.
[0087] For ALARA purposes, installation and removal of the pushing guide
sleeve 120 from
a lattice site can be fully automated through advance and retract operations
of the pallet with a
sleeve carriage, which keeping individuals away from potentially open
radiation beams.
[0088] The pushing guide sleeve 120 can be designed to be maintenance free
during a re-
tube outage, but may require maintenance between re-tube outages. If
maintenance is needed,
the pushing guide sleeve 120 can be easily removed from the sleeve carriage.
It should be
understood that multiple pushing guide sleeves 120 can be used as needed, and
that some sleeves
120 can be used as spares or for training.
[0089] FIG. 11 is a perspective view of a guide tool 130 according to an
embodiment of the
invention. The illustrated guide tool 130 guides the trailing end of the CT 32
in the x and y
directions to prevent damage to reactor components as CT-PT-AS packages are
removed from
the calandria 10. The guide tool 130 also provides assistance to the retrieval
tool 100 during the
first and any subsequent CT pulls on a contingency basis. The guide tool 130
can also include
provisions to pull the CT 32 back toward the pushing tube sheet 18 on a
contingency basis. The
guide tool 130 can also work in cooperation with the guide sleeve 120 to
prevent damage to the
pushing tube sheet 18.
[0090] As shown in FIG. 11, the illustrated guide tool 130 includes a water-
hydraulic pusher
132 and a brake point 133 (see FIG. 13) along a tubular body 134 that works in
cooperation with
a sleeve carriage (see FIG. 8). These features are designed to assist the
retrieval tool 100 during
the first and any subsequent pulls on the CT 32 to provide sufficient pushing
force. In particular,
the brake point 133 includes a positive brake device (e.g., electro-
mechanical) that couples
and/or locks the tubular body 134 to the sleeve carriage. The brake point 133,
therefore,
transfers the load generating from pushing the guide tool 130 through the
sleeve carriage, the
pallet system, and the HWT. In addition, the guide tool 130 can be an
accessory of the pallet,
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which requires less transaction time than separate tools. The guide tool 130
of the illustrated
embodiment also includes rollers 136 that protect the receiving end tube sheet
18 from damage
when the guide tool 130 is retracted from the lattice site. In some
embodiments, the guide tool
130 is approximately 28 feet long and 4.75 inches in diameter, and weighs
approximately 800
pounds.
[0091] The illustrated guide tool 130 also includes grippers 138, a flange
140, linear bearings
142, and brackets 144. The grippers 138 and rollers 136 can define a head 145
of the guide tool
130. The grippers 138 can include shoes, expanding split rings, bungs, wedges,
cams, rotating
circular grippers, or other mechanisms for gripping a portion of the CT 32.
The brackets 144
mount to the top surface of the pallet, and can align the tubular body 134 to
the working axis of
the pallet. Also, the linear bearings 142 guide the tubular body 134 in the z-
direction. The
flange 140 at the back of the tubular body 134 connects to the front of the
rigid push pull chain
of the pallet. When the rigid push pull chain is advanced, the tubular body
134 is advanced
through the linear bearings 142, and when the rigid push pull chain is
retracted, the tubular body
134 is retracted through the linear bearings 142. Also, the linked body of the
rigid push pull
chain is guided by the linear bearings 142 when in the advanced position. The
guide tool 130
can be transported in the vault on floor dollies, and can be installed or
removed from the pallet
by hoisting.
100921 The design of the grippers 138 and the pusher 132 on the guide tool
130 can be
similar to the grippers 104 and the puller 106 on the retrieval tool 100. For
example, the grippers
138 and the pusher 132 on the guide tool 130 can be operated with water-
hydraulic actuators.
However, in some embodiments, because push requirements can be less than pull
requirements,
the guide tool 130 includes only one row of grippers. Also, the automated
system for the guide
tool 130 can be configured to expand the head 145 to perform a push, whereas
the automated
system for the retrieval tool 100 can be configured to retract the tool 100 to
perform a pull. The
grippers 138 of the illustrated guide tool 130 are also designed to stay
engaged with the CT 32 as
it moves across the calandria 10, until the pushing CT bell has been pulled
through the receiving
tube sheet 18 (see FIG. 20, described in greater detail below).
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[0093] The guide tool 130 can be designed to be maintenance free during a
re-tube outage,
but may require maintenance between re-tube outages. Also, the head 145 can be
easily
removed for maintenance purposes. It should be understood that multiple guide
tools 130 may
be used as needed, and that some guide tools 130 may be used as spares or for
training.
[0094] Various contingency operations can also be performed with the
removal tools. For
example, tool shielding can be installed to allow individuals to troubleshoot
directly on the tools
when high radiation sources are present. In most cases, shielding allows tools
to be fixed
quickly, which allows production to be resumed. For this reason, the tooling
can be designed
with adequate shielding to allow individuals to perform safe troubleshooting
directly on the
tools.
[0095] Tooling on the receiving end of the reactor 6 can also be designed
so that it can push
a CT-PT-AS assembly back into the reactor 6 if needed. Likewise, tooling on
the pushing end of
the reactor 6 can be designed so that it can pull a CT-PT-AS assembly back
into the reactor 6.
This allows a CT-PT-AS package to be cleared from the receive tooling on the
receiving end of
the reactor 6 so that troubleshooting and replacements and repairs can be
performed to the
receive tooling if necessary. Furthermore, the pallet z-drive, which advances
and retracts the
tooling, and the rigid push pull chain ram drive can switch to alternate servo
drives if they should
become inoperable. These can also be driven manually to further support
recovery, if necessary.
[0096] The tooling described herein can be placed in various layouts at the
reactor faces.
When CT-PT-AS packages are removed from the pushing end to the receiving end
across the
calandria 10, the receiving RTP can include tools considered the "receive
tooling," and the
pushing RTP can include tools considered the "guide tooling." For example,
FIG. 12 is a
perspective view of receive tooling 150 installed at a receiving end of a
reactor 6 that includes
the retrieval tool 100 and the receiving guide sleeve 110. As shown in FIG.
12, the receive
tooling 150 also includes a HWT 152 with a front extension 154, a pallet 156,
a LS-SPIRT 158,
a flask 160, a sleeve carriage 162, and a vision tool 164. The vision tool 164
can be used to help
align the tooling 150 with a particular lattice site 166.
[0097] Similarly, FIG. 13 is a perspective view of guide tooling 170
installed at a pushing
end of the reactor 6 that includes the guide tool 130 and the pushing guide
sleeve 120. As shown
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CA 02766459 2012-01-16
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in FIG. 13, the guide tooling 170 also includes a HWT 172 with a front
extension 174, a pallet
176, a LS-SPIRT 178, a sleeve carriage 180, and a vision tool 182. Again, the
vision tool 182
can be used to align the guide tooling 170 with a particular lattice site 184.
100981 FIGS. 14 and 15 are flow charts illustrating a removal process for
removing a CT-PT-
AS package and placing the package into a flask using the tooling described
above according to
some embodiments of the present invention. In some embodiments, the operations
illustrated in
FIGS. 14 and 15 are carried out remotely from the RCC with automated tooling.
As shown FIG.
14, to start the process, the flask 160 is mounted on the receiving pallet 156
(at 200) and the
RTPs on each end of the reactor 6 are moved to the designated row (if not
already located there)
(at 202). In some embodiments, no workers are on the RTPs when they are moved.
The
receiving and pushing HWTs 152 and 172 are also moved to the designated column
(if not
already located there) (at 204) and are moved sideways a predetermined amount
to align the
working axis of the receive tooling 150 and the guide tooling 170 respectively
to the lattice site
where the CT-PT-AS package will be removed (at 206). If the receive tooling
150 or the guide
tooling 170 has difficulty aligning to the site, the vision systems 164 and
180 can be used to
perform the alignment for troubleshooting purposes.
100991 The receive tooling 150 and the guide tooling 170 are then advanced
to install the
guide sleeves 110 and 120 into the lattice site (at 208). The guide tool 130
is also advanced
through the pushing guide sleeve 120 and grips a diameter of the CT 32 (at
210). In some
embodiments, the guide tool 130 grips a minor diameter of the CT 32 toward the
pushing end of
the reactor just inward of a pushing bell section 209 of the CT 32. The guide
tool 130 holds the
CT 32 in its current z-position, as shown in FIG. 16.
1001001 The retrieval tool 100 is then advanced through the flask 160 and the
receiving guide
sleeve 110 and grips a diameter of the CT 32 (at 212). In some embodiments,
the retrieval tool
100 grips a minor diameter of the CT 32 toward the receiving end of the
reactor just past a
receiving bell section 211 of the CT 32, as shown in FIG. 17. In other
embodiments, this step
can be performed after, prior to, or simultaneously with the step of advancing
the guide tooling
170 as described above.
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Attorney Docket No. 027813-9038-CA00
[00101] With the retrieval tool 100 gripping the CT 32 at the receiving end
of the reactor, the
puller 106 of the retrieval tool 100 performs a first pull of the CT 32 (at
214), which frees the CT
32 from both tube sheets 18 as shown in FIGS. 18 and 19. The reaction force
generated from the
pull can be directed through the outboard face of the receiving tube sheet 18
(see FIG. 18).
Should the required removal force be higher than expected, the guide tooling
170 can provide an
additional push to remove the CT 32 (e.g., using the guide tool 130). The PT
36 and the annulus
spacers 48 positioned inside the CT 32 are contained inside the CT 32 as the
CT 32 is removed
from the lattice site and are prevented from moving out of the CT 32 by the
retrieval tool 100
and the guide tool 130 gripped at each end of the CT 32. Therefore, the PT 36
and annulus
spacers 48 cannot fall into the calandria 10.
[00102] After the first pull, the CT 32 and its contents are moved a
distance (e.g.,
approximately 12 inches) toward the receiving end of the reactor 6 by
synchronized operation of
the retrieval tool 100 and the guide tool 130 (at 216) as shown in FIGS. 20
and 21. At this point,
the receiving bell section 211 of the CT 32 has cleared the expanded rollers
112 in the receiving
guide sleeve 110 (see FIG. 20).
[00103] Next, the rollers of the receiving guide sleeve 110 are made to
contract onto and
support the receiving minor diameter of the CT 32 so it does not damage the
receiving tube sheet
18 as the CT 32 is moved through the receiving tube sheet bore in the next
step (at 218). Then
the CT 32 and its contents are moved almost all the way across the calandria
10 by synchronized
operation of the retrieval tool 100 and the guide tool 130. Throughout this
operation, the trailing
end of the CT 32 (i.e., the pushing end) is guided in the x and y directions
by the guide tool 130
to prevent damage to other reactor components. The CT 32 is stopped when the
pushing CT bell
209 is a relatively small distance (e.g., approximately 2 inches) away from
fully entering the
receiving tube sheet 18 (at 220) as shown in FIG. 22.
[00104] The guide rollers 112 on the receiving guide sleeve 110 are then
expanded so they
clear the pushing CT bell 209 (at 222), and the retrieval tool 100 perfolins a
second pull (at 224)
as shown in FIGS. 23 and 24, which moves the pushing CT bell 209 through the
receiving tube
sheet 18 as shown in FIG. 25. The reaction force generated by the retrieval
tool 100 is directed
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through a brake mechanism 225 in the flask 160 that is mounted at the
receiving end of the
reactor 6.
[00105] After the pushing CT bell 209 has cleared the receiving tube sheet 18,
the guide tool
130 un-grips the CT 32, and the guide tool 130 is retracted back across the
calandria 10 (at 226).
Small rollers 136 in the end of the guide tool 130 prevent damage to the
receiving tube sheet as
the guide tool 130 is retracted out of the lattice site (see FIG. 26). The
guide tooling 170 (e.g.,
guide tool 130 and pushing guide sleeve 120) is retracted from the lattice
site (at 228), the
pushing HWT 172 moves sideways (at 230), and the LS-SPIRT 178 installs the
shield plug back
into the lattice site on the pushing end of the reactor 6 (at 232).
[00106] On the receiving end of the reactor 6, the receive tooling 150 pulls
the CT-PT-AS
package into the flask 160 (at 234), and the receive tooling 150 (e.g.,
retrieval tool 100 and
receiving guide sleeve 110) is retracted from the lattice site (at 236). The
retrieval tool 100 then
un-grips the CT 32 (at 238), the retrieval tool 100 is retracted from the
flask 160 (at 240), the
receiving end HWT 152 moves sideways (at 242), and the LS-SPIRT 158 installs
the shield plug
back into the lattice site (at 244).
[00107] It should be understood that in some embodiments, the guide tool 130
is advanced
only partially (e.g., halfway) across the calandria 10 before it is retracted.
Furthermore, in some
embodiments, a CT-PT-AS package can be pushed out of the reactor using the
guide tool 130
without using the retrieval tool 100 to pull on the package. Similarly, in
some embodiments, a
CT-PT-AS package can be pulled out of the reactor using the retrieval tool 100
without using the
guide tool 130 to guide and push the package.
[00108] It should also be understood that in some embodiments, the annulus
spacers 48 may
be removed from the lattice site before the PT 36 and the CT 32 are removed.
Also, in some
embodiments, after the annulus spacers are removed, a spacer, such as a
sleeve, can be inserted
between the PT 36 and the CT 32 to maintain a gap between the PT 36 and the CT
32. After the
spacer has been installed, the PT 36 can be rotated and the resulting CT-PT-
spacer package can
be removed as described above.
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[00109] As alternative embodiments, the PTs 36 and CTs 32 can be removed
separately. To
remove each PT 36, the PT 36 can be pulled from the fuel channel assembly 28
and into a
shielded flask or a volume reduction machine that cuts the PT 36 into small
pieces and places the
pieces into a transfer flask. In some embodiments, PT removal begins at the
bottom row of the
calandria 10 and works up to the next higher row, from the lattice site near
the middle of the
calandria and toward the periphery sites. In some embodiments, approximately
14 to 25 PTs 36
can be removed each day in these alternate embodiments.
[00110] In some embodiments, the guide tooling 150 and/or the receive tooling
170 can be
used to remove the PTs 36 and the CTs 32 separately. For example, the guide
tooling 150 and/or
the receive tooling 170 can be configured to remove the PT-CT-AS package and
can also be
configured to remove the PTs 36 and CTs 32 separately as a back-up process. In
particular, to
remove the PTs 36 and CTs 32 separately, the guide tool 130 on the pushing end
of the reactor 6
can be used to push a severed PT 36 through the CT 32 and into a flask (while
also sweeping
loose annulus spacers 48 into the flask). In addition, the retrieval tool 100
can be configured to
grip the PT 36 and pull the PT 36 into the flask. Also, in some embodiments,
only the guide tool
130 is used to grip the PT 36 and push the PT 36 into the flask (e.g., the
additional pulling force
provided by the retrieval tool 100 may not be needed because the PT 36 does
not need to be
pulled from the tube sheet 18 as the CT). Furthermore, in some embodiments,
after the guide
tool 130 is used to push the PT 36 out of the CT 32 at the receiving end of
the reactor, the guide
tool 130 is retracted across the calandria 10 and can be configured to sweep
any remaining
annulus spacers 48 contained in the CT 32 to the pushing end of the reactor,
where they can be
deposited into a separate flask.
[00111] After the PT 36 has been removed, the flask containing the PT 36 can
be removed
and a new flask can be installed to receive another PT 36 at a different
lattice site or to receive
the CT 32 from the same lattice site. For example, in some embodiments, all of
the PTs 36 are
removed before the CTs 32 are removed to efficiently use removal tooling. In
other
embodiments, the PT 36 and the CT 32 from the same lattice site can be removed
sequentially
and the same flask can be used to separately receive the PT 36 and the CT 32.
After any needed
flask replacements have made performed (or after all of the PTs 36 have been
removed), the CT
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32 can be removed using the guide tool 130 and the .retrieval tool 100 as
described above with
respect to the CT-PT-AS package.
[00112] It should be understood that volume reduction can be performed at
various stages of
the CT and PT removal process (e.g., either as a package or separately). For
example, in some
embodiments, volume reduction can be performed at the face of the reactor 6
while a PT 36, a
CT 32, or a CT-PT-AS package is still partially inside the reactor 6.
Furthermore, in some
embodiments, after PTs 36, CTs 32, and/or CT-PT-AS packages have been placed
in a flask, the
full flask can be rotated (e.g., approximately 90 degrees) so it is parallel
to the face of the reactor
6. The HWT and/or the RTP supporting the flask can then be moved in the y
and/or the x
direction to engage the front end of the flask into volume reduction tooling
mounted to the vault
floor or the RTP. A drive mechanism (e.g., a Serapid chain drive included in
the pallet) can then
push the removed reactor components from the flask into the volume reduction
tooling. In yet
further embodiments, the volume reduction tooling can be positioned at other
locations, such as
inside or outside of the reactor vault. If the volume reduction tooling is
positioned outside of the
reactor vault, full flasks are transported to the volume reduction tooling and
empty flasks are
returned to the reactor face.
[00113] Thus, embodiments of the present invention provide, among other
things, methods
and systems for removing CTs 32, PTs 36, and annulus spacers 48 from a nuclear
reactor during
a re-tubing process. It should be understood, however, that the methods and
systems described
herein can be performed in various orders and configurations, and 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 CTs, PTs, annulus spacers, and/or reactor being retubed.
[00114] Various features and advantages of the invention are set forth in the
following claims.
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