Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 2766472 2017-02-27
Attorney Docket No . 027813-9037-CA00
CALANDRIA TUBE INSERT REMOVAL FOR REACTOR RETUBING
RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Application No.
61/433,471 of the same title 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] In some nuclear reactors, an insert is provided between each
calandria tube (which is
a conduit for a pressure tube and the fuel and fluid it contains during
operation of the reactor)
and a wall or "tube sheet" through which the calandria tube extends. The
insert can take various
forms, and in some cases is in the form of a sleeve or short tube. The insert
is typically
employed to secure and seal the calandria tube to the tube sheet to prevent
fluid from escaping
the interior of the calandria, especially in cases where the calandria tube
and the tube sheet are
constructed of different materials making welding and other attaching and
sealing manners
impractical or impossible. The calandria tube insert is often rolled (via a
roller extrusion
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process) into shape within its respective tube sheet bore, and must typically
be removed for
replacement during reactor re-tubing operations.
[0005] Embodiments of the present invention provide methods and systems for
removing a
calandria tube insert for reactor retubing. The method can include removing a
shield plug from a
lattice site, installing a hardstop sleeve in the lattice site to an outer
surface of a tube sheet,
advancing a removal tool into a calandria tube, gripping the calandria tube
with the removal tool,
and extracting the calandria tube insert. The method can also include
retracting the removed
calandria tube insert contained on the removal tool into a shielding flask,
and stripping the
removed calandria tube insert from the removal tool to place the calandria
tube insert into the
flask for transportation and disposal.
[0006] In particular, one embodiment of the invention provides a method for
removing an
insert attaching a calandria tube to a tube sheet in a nuclear reactor during
retubing of the reactor.
The method includes (a) advancing a removal tool into a lattice site including
a calandria tube
and an insert until a head of the removal tool is positioned within a diameter
of the calandria
tube, (b) expanding at least one retractor of the removal tool radially to
align the at least one
retractor inboard of the insert, (c) retracting the at least one refractor
axially to remove the insert
from the calandria tube and collect the insert on the removal tool, and (d)
retracting the removal
tool, with the collected insert, from the lattice site.
[0007] Another embodiment of the invention provides a tool for removing an
insert attaching
a calandria tube to a tube sheet in a nuclear reactor during retubing of the
reactor. The tool
includes a ram body and at least one retractor positioned on the ram body. The
ram body is
configured to be advanced into a lattice site containing a calandria tube and
an insert until a head
of the ram body is positioned within a diameter of the calandria tube. The at
least one retractor is
configured to expand radially to be aligned inboard of the insert and to
retract axially to remove
the insert from the calandria tube. The ram body is also configured to collect
the removed insert
and be retracted from the lattice site with the collected insert.
[0008] Yet another embodiment of the invention provides a system for
removing an insert
attaching a calandria tube to a tube sheet in a nuclear reactor during
retubing of the reactor. The
system includes a removal tool, a removal pallet system, and a flask. The
removal tool is
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=
mounted on the removal pallet system and is configured to be advanced into a
lattice site
including a calandria tube and an insert until a head of the removal tool is
positioned within a
minor diameter of the calandria tube, to grip at least a portion of the minor
diameter of the
calandria tube, to expand at least one retractor radially to align the at
least one retractor inboard
of the insert, to retract the at least one retractor axially to remove the
insert from the calandria
tube and collect the insert on the removal tool, to release the head of the
removal tool from the
minor diameter of the calandria tube, and to be retracted, with the collected
insert, from the
lattice site. The removal pallet system is configured to advance the removal
tool into the lattice
site and retract the removal tool from the lattice site. The flask is mounted
on the removal pallet
system and is configured to receive the removal tool, with the collected
insert, after the removal
tool is retracted from the lattice site and strip the collected insert from
the removal tool as the
removal tool is retracted from the flask.
[0009] Other aspects of the present invention will become apparent
by consideration of the
detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a reactor core of a CANDUTm-
type nuclear reactor.
[0011] FIG. 2 is a cut-away view of a CANDUTm-type nuclear reactor
fuel channel assembly.
[0012] FIG. 3 is a perspective view of a calandria tube insert
removal tool according to an
embodiment of the invention.
[0013] FIG. 4 is a perspective view of a calandria tube insert
hardstop sleeve according to an
embodiment of the invention.
[0014] FIG. 5 is a perspective view of a sleeve carriage according
to an embodiment of the
invention.
[0015] FIG. 6 is a perspective view of a calandria tube insert
removal system.
[0016] FIG. 7 is a flowchart illustrating a calandria tube insert
removal process according to an
embodiment of the invention.
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[0017] FIG. 8 is a side cut-away view of the calandria tube insert removal
system of FIG. 6,
shown in a retracted configuration.
[0018] FIG. 9 is a side cut-away view of the calandria tube insert removal
system of FIG. 6,
shown installing the hardstop sleeve of FIG. 4 into a lattice site.
[0019] FIG. 10 is a side cut-away view of the calandria tube insert removal
system of FIG. 6,
with the ram of the removal tool of FIG. 3 advanced to position the head of
the removal tool at
the minor diameter of a calandria tube inside the lattice site.
[0020] FIG. 11 is a cut-away view of the head of the removal tool of FIG.
3, shown
positioned at the minor diameter of the calandria tube inside the lattice site
as illustrated in FIG.
10.
[0021] FIG. 12 is a cut-away view of the head of the removal tool of FIG.
3, shown with
retractors of the removal tool expanded.
[0022] FIG. 13 is a cut-away view of the head of the removal tool of FIG.
3, shown with the
retractors retracted to remove the calandria tube insert.
[0023] FIG. 14 is a cut-away view of the head of the removal tool of FIG. 3
illustrating a
reaction force load path when the removal tool removes the calandria tube
insert.
[0024] FIG. 15 is a cut-away view of the head of the removal tool of FIG.
3, shown released
from the minor diameter of the calandria tube.
[0025] FIG. 16 is a side cut-away view of the calandria tube insert removal
system of FIG. 6,
with ram of the removal tool of FIG. 3 and the removed calandria tube insert
retracted into a
flask.
[0026] FIG. 17 is a side cut-away view of the calandria tube insert removal
system of FIG. 6,
shown retracted from the lattice site.
[0027] FIG. 18 is a side view of a profile of a cam tube included in the
removal tool of FIG.
3.
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[0028] FIG. 19 is a cut-away view of the removal tool of FIG. 3, shown with
multiple
calandria tube inserts contained on the ram.
[0029] FIG. 20 is a top cut-away view of the removal tool of FIG. 3, shown
with posts
included in the flask that strip calandria tube inserts off the ram of the
removal tool.
[0030] FIG. 21 is a side cut-away view of the calandria tube insert removal
system of FIG. 6,
shown with the removal tool of FIG. 3 retracted through the flask and the
removed calandria tube
inserts contained within the flask.
DETAILED DESCRIPTION
[0031] 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.
[0032] 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.
[0033] 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.
[0034] A pressure tube ("PT") 36 forms an inner wall of the fuel channel
assembly 28. The
PT 36 provides a conduit for reactor coolant and the fuel bundles or
assemblies 40. The PT 36,
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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 gas are part of an annulus gas system. The annulus gas system has two
primary functions.
First, a gas boundary between the CT 32 and PT 36 provides thermal insulation
between hot
reactor coolant and fuel within the PTs 36 and the relatively cool CTs 32.
Second, the annulus
gas system provides an indication of a leaking CT 32 or PT 36 via the presence
of moisture,
deuterium, or both in the annulus gas.
[0035] An annulus spacer or garter spring 48 is disposed between the CT 32
and PT 36. The
annulus spacer 48 maintains the gap between the PT 36 and the corresponding CT
32, while
allowing the passage of the annulus gas through and around the annulus spacer
48. Maintaining
the gap helps ensure safe and efficient long-term operation of the reactor 6.
[0036] As also shown in FIG. 2, 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.
[0037] Coolant from the inlet feeder assembly flows along an annular
perimeter 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 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
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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.
[0038] 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 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.
[0039] 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.
[0040] 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.
[0041] 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
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").
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[0042] 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.
Also, in preparation for removing the fuel channel assemblies 28, the bellows
62 and the PTs 36
can be severed.
[0043] A removal pallet system (also referred to as a "pallet") can be
installed and
implemented at an end of the reactor 6 on a RTP after severing the PTs 36 from
the bellows 62 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.
[0044] After the pallet is installed, the end fittings 50 can be removed.
With the end fittings
50 removed, the 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. Therefore, before the CTs 32 can be removed,
the CTIs 34 are
removed. Also in some embodiments, the CTIs 34 are released before they are
removed (e.g.,
through induction heating, milling, or other means). The processes of
releasing and removing
the CTIs 34 can be coordinated such that they are performed in parallel at
different lattice sites.
In other embodiments, the release and removal processes can be performed
sequentially, which
can require less coordination. The CTIs 34 can be released or prepared for
removal using
various methods and systems, including using heat induction. Once so prepared,
the CTIs 34 can
be removed from the reactor 6.
[0045] As described in more detail below, during a CTI removal series,
removal tooling (also
described in more detail below) removes one CTIs 34 at a time, until a
predetermined quantity of
CTIs 34 (e.g., approximately ten CTIs 34) have been accumulated. The
accumulated CTIs 34
are then placed into a shielded flask. The flask provides shielding from the
removed CTIs 34
and minimizes radioactive exposure to personnel while performing their duties
(e.g., removing a
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full flask or troubleshooting the removal tooling). When a flask is full, the
RTP can be lowered
to the vault floor for hoisting the full flask to a vault trolley system. The
vault trolley system
transports the full flask out of the vault for loading onto a truck. An empty
flask 178 is then
transported into the vault by the trolley system, and can be hoisted onto the
RTP. The RTP can
then be elevated to the designated row where the tooling continues removing
CTIs 34.
[0046]
In some embodiments, the CTI removal series can be divided into automated and
manual operations. The automated operations may be controlled via a local
tethered pendant, or
may be controlled remotely from the RCC, and can include those operations
associated with
reactor face operations where tooling is mounted on the HWTs. These remote
operations can be
performed for "as low as reasonably achievable' ("ALARA") purposes, so that
although the
radioactive components are behind shielding, people may be positioned away
from highly
radioactive operations as much as possible. On the other hand, the manual
operations can be
those operations associated with the hoisting and transportation of the flasks
178.
[0047]
The CTI removal process can be performed using one or two HWTs 174 on each
face
of the reactor 6, and HWTs 174 on the same and opposite faces can be operated
independently
from the other HWTs 174. Tooling used on the HWTs 174 at each face can be
identical, and
CTIs 34 can be removed simultaneously in a staggered fashion (e.g., from the
opposite reactor
faces) to accommodate flask trolley vault traffic.
[0048]
Removal tooling used in the CTI removal process can include a CTI removal
tool.
FIG. 3 is a perspective view of a CTI removal tool 100 according to an
embodiment of the
invention. In some embodiments, the CTI removal tool 100 is mounted to the
pallet. In some
embodiments, by way of example only, the CTI removal tool 100 can be
approximately 12 feet
long, 20 inches wide, and 1 foot tall, and can weigh approximately 500 pounds.
[0049]
As shown in FIG. 3, the illustrated CTI removal tool 100 includes a backstop
101, a
ram body 104, retractors 105, and optional grippers 106. The removal tool 100
can use the
pallet's rigid "push pull" chain (e.g., a rigid push pull chain manufactured
by Serapid, Inc.) to
advance and retract the ram 104. As will be discussed in greater detail below,
the ram 104
reaches through a flask to obtain a CTI 34 and extract it into the flask. The
grippers 106 can be
configured to grip a diameter of a CT 32 (e.g., a minor diameter or a bell
section of the CT 32) to
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prevent the CT 32 from moving while the CTI 34 is removed. The grippers 106
can include
shoes, expanding split rings, bungs, wedges, cams, rotating pie-shaped
grippers or circular
grippers, or other mechanisms for gripping a portion of the CT 32 while the
CTI 34 is removed.
The removal tool 100 directs the reaction load from removing the CTI 34
against the flask. The
removal tool 100 can remove CTIs 34 one at a time, and can accumulate any
desired number
(e.g., ten CTIs 34) on the ram 104. After a CTI 34 is removed, if the optional
grippers 106
where used, the removal tool 100 un-grips or releases the minor diameter of
the CT 32 to prevent
the CT 32 from moving while the ram 104 is retracted. The removal tool 100
uses the flask
where removed CTIs 34 are deposited for shielding, and can operate with
automated systems. In
some embodiments, the removal tool 100 also operates manually for contingency
purposes.
100501 The retractors 105 retract the CTIs 34 from the lattice site. In
particular, the
retractors 105 can be radially expandable to be engaged with or aligned
inboard of (i.e., behind)
a released CTI 34, such that when the retractors 105 are retracted axially,
the CTI is also
retracted. The retractors 105 illustrated and described in the present
application include shoes
that are radially expandable and axially retractable. However, similar to the
grippers 106, it
should be understood that the retractors 105 can include expanding split
rings, bungs, wedges,
cams, rotating pie-shaped or circular grippers, or other mechanisms for
engaging and retracting a
released CTI 34 from a lattice site.
100511 The CTI removal tool 100 can be transported in the vault on floor
dollies, and can be
installed or removed from the pallet by hoisting. In some embodiments, the CTI
removal tool
100 uses off-the-shelf, commercially available servo drives, linear drives,
and a gear box. A
frame 107 of the CTI removal tool 100 can be mounted to the top surface of the
pallet by
brackets 108, which bring the working axis of the pallet and the CTI removal
tool 100 into
alignment. The pallet's rigid push pull chain attaches to the back of a
carriage 110 of the tool
100 at a flange 112. As shown in FIG. 3, the removal tool 100 also includes
linear bearings 114
and rails 116. The frame 107, rails 116, linear bearings 114, carriage 110,
and the cantilevered
ram body 104 form a ram axis that is advanced or retracted by the rigid push
pull chain. In the
illustrated embodiment, the grippers 106 and the retractors 105 are actuated
by a pull rod and
linear drive assembly 118 also included in the CTI removal tool 100. The drive
118 can derive
its power through a cable track 120, which accommodates the z-motion of the
carriage 110. The
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illustrated ram body 104 is designed to hold approximately ten removed CTIs
34, and the
backstop 101 prevents the removed CTIs 34 from traveling lengthwise along the
ram body 104
toward the carriage 110 as the ram body 104 is retracted from the lattice
site.
[0052] In some embodiments, the CTI removal tool 100 is designed to be
maintenance free
during a retube outage. However, the CTI removal tool 100 may require
maintenance between
retube outages. It should be understood that multiple removal tools 100 can be
used during a
retube process for production or training or for the purpose of keeping a
spare on hand.
[0053] In some embodiments, a CTI hardstop sleeve can be used to remove the
CTIs 34.
The hardstop sleeve provides a path for the reaction load between the flask
where removed CTIs
34 are deposited and the outboard face of the tube sheet 18 surrounding the
lattice site where the
CTI 34 is removed from. The hardstop sleeve can be used if high loads are
required to remove
the CTIs 34 (i.e., to provide additional support to the removal tooling). In
particular, one
purpose of the hardstop sleeve is to provide additional rigidity to the
removal tooling in cases
where the removal forces are very high. This situation can occur if the
release tooling did not do
a nominal job of releasing a CTI 34 and several thousands pounds of force is
needed to extract
the CTI 34 from the tube sheet 18 and the CT 32. Without the hardstop sleeve,
the reaction load
is taken by the flask receiving removed CTIs 34 butting up against the lattice
sleeve assemblies
(i.e., thumbtacks) or by the RTP.
[0054] FIG. 4 is a perspective view of an example of a CTI hardstop sleeve
130 according to
an embodiment of the invention. The sleeve 130 is designed to accommodate
removed CTIs 34
through its opening. For example, the sleeve 130 can be approximately 4 feet
long and 6 inches
in diameter, and can weigh approximately 50 pounds. In some embodiments, the
sleeve 130 is
mounted to a sleeve carriage 140, as described below.
[0055] For ALARA purposes, installation and removal of the CTI hardstop
sleeve 130 from
a lattice site can be fully automated through advance and retract operations
of the pallet and the
sleeve carriage 140, which keeps people away from potential open radiation
beams. The CTI
hardstop sleeve 130 can be designed to be maintenance free during a retube
outage, but may
require maintenance between retube outages. In some embodiments, the CTI
hardstop sleeve
130 can be removed from the sleeve carriage 140 with relative ease for
maintenance as needed.
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It should be understood that multiple sleeves 130 can be used during a retube
process for
production or training or for the purpose of keeping spares on hand. Also, in
some
embodiments, the hardstop sleeve 130 may not be used, and the existing lattice
tube sleeve 65
can be used to perform the same functionality provided by the sleeve 130.
Using the lattice tube
65 in place of the hardstop sleeve 130 can shorten the length of the CTI
removal tooling and, in
some embodiments, allows the flasks containing removed CTIs 34 to be lowered
through a back
hatch of the RTP.
[0056] As previously mentioned, the CTI hardstop sleeve 130 can be mounted
on a sleeve
carriage 140. FIG. 5 is a perspective view of a sleeve carriage 140 according
to an embodiment
of the invention. The sleeve carriage 140 can be used in the CTI removal
process to mount the
CTI hardstop sleeve 130.
[0057] The sleeve carriage 140 mounts and aligns the sleeves 130 with the
working axis of
the pallet. The sleeve carriage 140 can allow for easier insertion and removal
of the sleeves 130
from a lattice site by providing some compliance to the sleeve alignment. In
addition, clearance
to the inboard end of the flask is provided when pallet tooling is in a
retracted position. This
clearance facilitates easier change-out of the flasks. In addition, the sleeve
carriage 140 provides
clearance at the front of the flask collecting the removed CTIs 34 such that
the flask can be
closed for ALARA purposes when the pallet is moved to an advanced position.
[0058] In some embodiments by way of example only, the sleeve carriage 140
is
approximately 3 feet long, 3 feet high, and 18 inches wide, and can weigh
approximately 400
pounds. As shown in FIG. 5, the sleeve carriage 140 consists of shielding 142,
a compliant
mount 144, a bracket 146, linear bearings 148, and a hitch 150. The hardstop
sleeve 130 can be
attached to the shielding 142 by the compliant mount 144 so that the sleeve
deflects slightly in
the x and y directions when advanced or retracted from the lattice site. This
deflection ability
accommodates some misalignment of tooling to the lattice site, so that less
critical path time is
spent troubleshooting tool alignment.
[0059] The shielding 142 is provided between the front of the flask
collecting removed CTIs
34 and the lattice sleeve assembly ("LSA") for ALARA purposes so that when the
CTI 34 is
being removed there is minimal radiation originating from that area. The
shielding 142 is k.
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supported by the bracket 146 mounted to the linear bearings 148. The linear
bearings 148 can
engage HWT rails for motion in the z-direction, which can also be the same
rails that the pallet
uses for its z-axis motion. The sleeve carriage 140 aligns the sleeves 130
with the working axis
of tooling mounted on the pallet while allowing movement in the z-direction.
In some
embodiments, the flask collecting the removed CTIs 34 abuts the shielding 142
to conduct the
reaction force generated with CTI removal.
100601 The hitch 150 of the illustrated sleeve carriage 140 connects the
sleeve carriage 140
to the pallet. When the pallet is in a retracted position, the hitch 150
functions to push the
shielding 142 a few inches away from the flask collecting the removed CTIs 34
along the HWT
rails. This provides clearance to allow easier and safer hoisting of the
flask. When the pallet is
advanced to engage a lattice site, a sensor in the hitch 50 can detect if the
front end of the sleeve
130 is not being inserted freely and, if so, can signal the automated system
to stop, which allows
operators to troubleshoot. The sleeve carriage 140 can be designed to be
maintenance free
during a retube outage, but may require maintenance between retube outages.
The compliant
mount 144 can be designed so that the sleeves 130 can be removed easily for
maintenance as
needed. It should be understood that multiple sleeve carriages 140 can be used
during a retube
process for production, training, or for to be kept as a spare.
100611 Additional tooling can also be used to remove the CTIs 34. For
example, a lattice
sleeve/shield plug insertion and removal tool ("LS-SPIRT") 160 (see FIG. 6)
can be used to
remove the shield plug 58 of the LSA to gain access to the CTI 34 for removal
thereof, and to re-
insert the shield plug 58 after the CTI 34 has been removed. A vision tool can
also be used to
ensure proper alignment and operation of the tooling used during the removal
process.
100621 Other contingency tools can be used during the process of removing
the CTIs 34. For
example, flask shielding allows (e.g., manual) troubleshooting be performed
directly on the
removal tool 100 if necessary. Also, the z-drive of the pallet, which advances
and retracts the
CTI removal tool 100, and the rigid push pull chain can switch to alternate
servo drives if they
should become inoperable. These drives can also be driven manually, if
necessary, to further
support recovery. In some embodiments, if the CTI removal tool 100 drags or
drops a CTI 34
into the lattice sleeve 65, a camera on a boom or a CTI reinstallation tool
can be used to insert
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the CTI 34 back into the bore of the tube sheet 18 where it can be removed
again using the CTI
release tool 100.
[0063] FIG. 6 is a perspective view of a CTI removal system 170 according
to an
embodiment of the present invention. The system 170 includes the CTI removal
tool 100, the
hardstop sleeve 130, the sleeve carriage 140, and the LS-SPIRT 160. As shown
in FIG. 6, the
CTI removal tool 100 is mounted on a pallet 172, which is supported by a HWT
174 including a
front extension 176. The LS-SPIRT 160 is also supported by the HWT 174 in this
embodiment,
and a CTI flask 178 is mounted in front of the removal tool 100 on the pallet
172. At the front of
the HWT 174, the CTI hardstop sleeve 130 is mounted on the sleeve carriage
140. If a vision
tool 180 is used during the CTI removal process, it can also be mounted toward
the front of the
HWT 174. It should be understood that in some embodiments, a CTI removal
system 170 as
illustrated in FIG. 6 is set up on each end of the reactor 6. Therefore, a CTI
34 can be removed
from a lattice site on each end of the reactor 6.
[0064] In some embodiments, most of the tooling used from the previous
series of steps (e.g.,
the steps performed for releasing CTI 34) in the retubing process can be re-
used during the CTI
removal series. For example, the front extensions 176 of the HWT 174 can
remain installed on
the front of the HWT 174 and the pallet 172, LS-SPIRT 160, and vision system
180 can be re-
used. These common features benefit ALARA and critical path time by
eliminating the need to
remove, install, and commission new tools between each series of steps in the
retubing operation.
Additional tooling needed for the CTI removal process, such as the CTI removal
tool 100, the
hardstop sleeve 130, the sleeve carriage 140, and the flask 178, can be moved
on to the RTP
using a floor trolley and hoisted by a vault crane to the RTP.
[0065] FIG. 7 is a flow chart illustrating a CTI removal process in more
detail. As illustrated
in FIG. 7, the exemplary process initially starts by mounting the flask 178 to
the pallet 172 (at
200). Once the flask is mounted, the RTP can be positioned at the designated
row (at 202), and
the HWT 174 can be moved to the designated column (at 204), such that the CTI
removal tooling
is positioned in front of a designated lattice site where a CTI 34 is to be
removed. Once the
tooling is in place, the LS-SPIRT 160 removes the shield plug 58 (at 206). If
the LS-SPIRT 160
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has difficulty aligning to the site, the vision system 180 can be used to
perform alignment for
troubleshooting purposes.
[0066] Next, the HWT 174 moves sideways a predetermined amount to align the
working
axis of the CTI removal tool 100 to the lattice site (at 208). If the CTI
removal tool 100 has
difficulty aligning to the lattice site, the vision system 180 can be used to
perform alignment for
troubleshooting purposes. At this point, the CTI removal tooling is in its
initial retracted
configuration in front of a designated lattice site 209, as shown in FIG. 8.
100671 Next, the CTI hardstop sleeve 130 is optionally installed into the
lattice site 209 (at
210), as shown in FIG. 9. The ram 104 of the CTI removal tool 100 is then
advanced through
the flask 178, the CTI hardstop sleeve 130, and a released CTI 34 to a
diameter of the CT 32 (at
212), as shown in FIGS. 10-11. The CTI removal tool 100 then expands the
retractors 105
radially to align the retractors 105 inboard of (i.e., behind) the CTI 34 (at
214), as shown in FIG.
12. Optionally, grippers 106 can be simultaneously expanded with the
retractors 105 to grip at
least a portion of the diameter of the CT 32 (at 216), as also shown in FIG.
12. In some
embodiments, the grippers 106 grip a CT bell 213 or a minor diameter of the CT
32. Gripping
the CT 32 with the grippers 106 prevents or limits the CT 32 from moving when
the CTI 34 is
removed in a later step. It should be understood, however, that gripping the
CT 32 is optional
and may not be needed in some situations depending on how the CTI 34 are
released and,
consequently, how much force is needed to remove the CTIs 34.
[0068] After the retractors 105 are radially extended, the retractors 105
are retracted axially
to remove the CTI 34 (at 218), as shown in FIG. 13. It should be understood
that in some
embodiments, the retractors 105 do not engage an inner surface of the CTI 34
when they are
initially expanded. For example, once the retractors 105 have been expanded
radially, there can
be approximately 'A of an inch axial clearance between the back edge of the
retractors 105 and
the inner edge of the CTI 34. In this situation, the expanded retractors 105
engage the CTI 34 as
the retractors 105 are retracted. In other embodiments, however, the
retractors 105 can be
radially expanded to engage an inner surface of the CTI 34 even before the
retractors 105 are
retracted from the lattice site.
CA 02766472 2012-01-16
Attorney Docket No. 027813-9037-CA00
[0069] The reaction force generated by the ram 104 as the CTI 34 is removed
is taken by the
ram tube and is directed through the flask 178, the CTI hardstop sleeve 130,
and onto an
outboard face 221 of the calandria tube sheet 18, as shown in FIG. 14. With
the CTI 34
removed, if the optional grippers 106 were used, the grippers 106 un-grip or
release the CT 32
(at 220) as shown in FIG. 15. Next, the ram 104 and the removed CTI 34 are
retracted back into
the CTI flask 178 (at 222) as shown in FIG. 16, and the CTI removal tooling is
retracted from the
LSA (at 224) as shown in FIG. 17. The CTI hard stop sleeve 130 can then be
removed (at 226),
and the LS-SPIRT 160 can reinstall the shield plug 58 (at 228).
100701 In some embodiments, the grippers 106 and the retractors 105 are
actuated by a
central rod 300 (see FIGS. 11-13 and 15). For example, linear bearings 302 are
incorporated into
the grippers 106 and in a housing 304 of the CTI removal head to guide the
grippers 106 radially.
Rollers 306 are also incorporated into the grippers 106 that ride on a profile
of a cam tube 308.
Mechanical springs (not shown) apply loads to the grippers 106 to contract the
grippers 106 in a
compliant manner onto the profile of the cam tube 308. As shown in FIG. 18,
the profile of the
cam tube 308 includes a first low surface 310, a raised surface 312, and a
second low surface 314
with sloped transitions 316 between each surface. The cam tube 308 is moved
axially by the
central rod 300 that extends back along the ram body 104 to a servo drive
unit. When the rollers
306 are on the first and second low surfaces 310 and 314, the grippers 106 are
retracted (i.e., not
gripping the CT 32) (see FIGS. 11 and 15), and when the rollers 306 are on the
raised surface
312, the grippers 106 are extended (i.e., gripping the CT 32) (see FIG. 12).
[0071] Similarly, the retractors 105 (illustrated as shoes 105 in FIGS. 11-
13 and 15) are
configured to move radially and axially with respect to the housing 304, and a
mechanical wedge
320 is used to actuate the shoes 105 radially when the central rod 300 is
actuated axially. A
compliant sleeve 322 is configured with a compression spring 324 so that it
can be moved axially
by the shoes 105 when sufficient force is applied. When the central rod 300 is
in its extended
position (see FIG. 11), the wedge 320 is disengaged. From its forward
position, when the central
rod 300 is first retracted, light force engages the wedge 320 until the shoes
105 are fully
expanded (see FIG. 12). Once fully expanded, the shoes 105 hard-stop and
additional force
moves the compliant sleeve 322, which allows the shoes 105 to move axially
(see FIGS. 13 and
15).
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[0072] Therefore, in operation the central rod 300 operates both the
grippers 106 and the
retractors 105 simultaneously. For example, the central rod 300 starts in the
fully extended
position, in which the grippers 106 are retracted (i.e., the rollers 306 are
on the first low surface
310 of the cam tube 308) and the shoes 105 are retracted (i.e., the wedge 320
is disengaged) (see
FIG. 11.). As shown in FIG. 11, in this position, the CTI removal tool 100 is
deployed to the
lattice site to a depth such that the grippers 106 are aligned axially with
the minor diameter of the
CT 32 next to the bell 213 and the lip of the shoes 105 are aligned to clear
the inboard edge of
the CTI 34 by approximately 'A of an inch. Once the CTI removal tool 100 is
positioned, the
central rod 300 is pulled a short distance, such that the grippers 106 become
fully expanded to
grip the CT 32 (i.e., the rollers 306 are on the raised cam surface 312), and
the shoes 105 become
fully expanded (i.e., the wedge 320 is engaged) (see FIG. 12).
[0073] To retract the shoes 105 axially, the central rod 300 is pulled a
further distance, which
causes the compliant sleeve 322 and the shoes 105 to move axially (see FIG.
13) and remove the
CTI 34 while the grippers 106 remain engaged with the CT 32 (i.e., to ensure
the CT 32 is not
pulled out with the CTI 34). The central rod 300 is then pulled to its maximum
position, which
moves the shoes 105 and the removed CTI 34 further along the ram body 104 and
retracts the
grippers 106 (i.e., the rollers 306 are on the second low surface 314 of the
cam tube 308) (see
FIG. 15). The CTI removal tool 100 is then retracted from the lattice site.
[0074] As shown in FIG. 7, after removing a CTI 34, the removal tooling can
be moved to
the next lattice site. For example, if the next lattice site is in the same
row, the HWT 174 can be
moved sideways to align the tooling with the next lattice site (at 204). If
the next lattice site is in
the next row, the RTP can be vertically repositioned to the new row (at 202).
Once re-aligned,
the tooling can repeat steps 206 through 228 until multiple CTIs 34 (e.g.,
ten) have been
removed and collected on the ram 104. It should be understood that number of
CTIs 34 that can
be removed and collected on the ram 104 may vary based on the size of the CTI
34, the size of
the removal tooling, and the size of the flask 178. For example, as shown in
FIG. 19, when ten
CTIs 34 are removed in the illustrated embodiment, the ram 104 is filled with
CTIs 34 that must
be removed to make room for additional CTIs 34.
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[0075] To remove the CTIs 34 from the ram 104, the flask 178 can include
fixed posts 430
on a side of the flask 178 behind the outboard CTI on the ram 104 when the ram
104 is
positioned in the flask 178, as shown in FIG. 20. The posts 430 can be used to
strip the CTIs 34
off the ram 104 as the ram 104 is retracted out of the flask 178, as shown in
FIG. 21. Therefore,
although the ram 104 is retracted from the flask 178, the posts 430 block the
CT! 34 from also
being retracted, and the CTI 34 remain in the flask 178. If the flask 178 is
full, it can be removed
from the pallet 172, and an empty flask 178 can be mounted on the pallet 172
if additional CTIs
34 still need to be removed from the reactor 6 (at 200). Thereafter, the
process can be repeated
again (steps 202 through 228) as additional empty flasks 178 are needed, and
until all CTIs 34
have been removed from the reactor 6. In some embodiments, the reactor 6
includes
approximately 760 to 960 CTIs 34 that are removed and disposed of as
radioactive waste. Using
the methods and systems described above, in some embodiments, CTIs 34 can be
removed at a
rate of approximately 90 per day.
[0076] Thus, embodiments of the invention provide, among other things,
methods and
systems for removing CTIs for retubing a nuclear reactor. It should be
understood, however, that
the methods and systems described above can be performed in various orders and
configurations,
and 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 CT, the CTI, and/or the reactor
being retubed.
[0077] Various features and advantages of the invention are set forth in
the following claims.
18
