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Patent 2766465 Summary

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Claims and Abstract availability

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(12) Patent: (11) CA 2766465
(54) English Title: CALANDRIA TUBE ROLLED JOINT LEAK TEST TOOL AND SERVICE CART
(54) French Title: OUTIL D'ESSAI ET CHARIOT DE SERVICE POUR VERIFIER LA PRESENCE DE FUITES DANS LES JOINTS ROULES DES TUBES DE CALANDRE
Status: Granted
Bibliographic Data
(51) International Patent Classification (IPC):
  • G21C 17/017 (2006.01)
  • G01M 3/28 (2006.01)
(72) Inventors :
  • METZGER, DONALD RAY (Canada)
  • RICE, STEFANI NANCY JEAN (Canada)
  • ALBERT, MICHAEL DAVID (Canada)
  • COLLING, GEOFFREY SHANE (Canada)
  • SABHAYA, SAUMIL (Canada)
  • QUASTEL, AARON DAVID (Canada)
(73) Owners :
  • ATOMIC ENERGY OF CANADA LIMITED (Canada)
(71) Applicants :
  • ATOMIC ENERGY OF CANADA LIMITED (Canada)
(74) Agent: NORTON ROSE FULBRIGHT CANADA LLP/S.E.N.C.R.L., S.R.L.
(74) Associate agent:
(45) Issued: 2018-01-02
(22) Filed Date: 2012-01-16
(41) Open to Public Inspection: 2012-07-17
Examination requested: 2016-10-20
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data:
Application No. Country/Territory Date
61/433,431 United States of America 2011-01-17

Abstracts

English Abstract

Methods and systems for testing a joint assembly coupling a calandria tube to a tube sheet in a reactor. One method includes (a) inserting a test tool into a lattice site containing the joint assembly, the test tool including at least two seals that define an enclosed volume surrounding the joint assembly. The method also includes (b) drawing a vacuum in the enclosed volume, (c) stopping drawing the vacuum in the enclosed volume and allowing the vacuum to decay over a predetermined decay period, (d) measuring a change in pressure in the enclosed volume during the decay period and calculating a leak rate based on the change in pressure, (e) repeating (b) through (d) to generate a plurality of leak rates, and (f) determining an equilibrium leak rate based at least on the plurality of leak rates. The method also includes performing diagnostics during the testing method.


French Abstract

Des méthodes et des systèmes servent à vérifier un mécanisme de joint couplant un tube de calandre à une feuille de tube dans un réacteur. Une méthode comprend (a) linsertion dun outil de vérification dans un site de réseau comportant le mécanisme de joint, loutil de vérification comprenant au moins deux joints détanchéité qui définissent un volume fermé entourant le mécanisme de joint. La méthode comprend (b) la production dun vide dans le volume fermé, (c) larrêt de la production du vide dans le volume fermé et lattente de décroissance du vide pendant une période de décroissance prédéterminée, (d) la mesure dun changement dans la pression du volume fermé pendant la période de décroissance et le calcul dun taux de fuite fondé sur le changement de pression, (e) la répétition de (b) à (d) pour produire une pluralité de taux de fuite et (f) la détermination dun taux de fuite équilibré fondé sur la pluralité de taux de fuite. La méthode comprend également la réalisation de diagnostics pendant la méthode de vérification.

Claims

Note: Claims are shown in the official language in which they were submitted.



What is claimed is:

1. A method of testing a joint assembly coupling a calandria tube to a tube
sheet in a
reactor, the method comprising:
(a) inserting a test tool into a lattice site containing the joint assembly,
the test tool
including at least two seals that define an enclosed volume surrounding the
joint
assembly;
(b) drawing a vacuum in the enclosed volume;
(c) stopping drawing the vacuum in the enclosed volume and allowing the
vacuum to decay over a predetermined decay period;
(d) measuring a change in pressure in the enclosed volume during the decay
period and calculating a leak rate based on the change in pressure;
(e) repeating (b) through (d) to generate a plurality of leak rates; and
(f) determining an equilibrium leak rate based at least on the plurality of
leak
rates.
2. The method of Claim 1, further comprising comparing the equilibrium leak
rate to
a quality leak rate range to identify when the joint assembly is properly
installed.
3. The method of Claim 1, further comprising radially expanding at least
one of the
at least two seals of the test tool after the test tool is inserted into the
lattice site.
4. The method of Claim 1, further comprising:
(g) supplying helium to at least one area outside of the enclosed volume;
(h) measuring an amount of helium in the enclosed volume;
(i) calculating a second leak rate based on the measured amount of helium in
the
enclosed volume and an ambient helium amount; and

17


(j) repeating (h) through (i) to generate a plurality of second leak rates.
5. The method of Claim 4, wherein determining the equilibrium leak rate
includes
determining the equilibrium leak rate based on the plurality of leak rates and
the plurality
of second leak rates.
6. The method of Claim 1, further comprising:
(g) supplying helium to at least one area outside of the enclosed volume;
(h) measuring an amount of helium inside the enclosed volume; and
(i) determining when one of the two seals of the test tool is leaking based on
the
measured amount of helium inside the enclosed volume.
7. The method of Claim 6, further comprising repeating (g) through (h).
8. The method of Claim 6, wherein supplying helium includes supplying
helium
when the vacuum is drawn on the enclosed volume.
9. The method of Claim 6, further comprising stopping supplying helium to
the at
least one area outside of the enclosed volume during the decay period.

18


10. A system for testing a joint assembly coupling a calandria tube to a
tube sheet in a
reactor, the system comprising:
a pump for drawing a vacuum on an enclosed volume surrounding the joint
assembly;
a test tool coupled to the pump by at least one hose and including
a test head including at least two seals for defining the enclosed volume
and an inlet for drawing the vacuum on the enclosed volume,
a pressure gauge for measuring a pressure in the enclosed volume,
a vacuum tube for drawing the vacuum on the enclosed volume, and
at least one valve for repeatedly drawing the vacuum on the enclosed
volume and letting the vacuum decay over a predetermined decay period,
wherein the pressure gauge provides a plurality of pressure readings in the
enclosed volume during the repeated drawings of the vacuum and vacuum decays,
the
plurality of pressure readings used to calculate an equilibrium leak rate of
the joint
assembly.
11. The system of Claim 10, further comprising a helium leak detector for
detecting
an amount of helium in the enclosed volume.
12. The system of Claim 11, wherein the helium leak detector contains the
pump and
is connected to the test tool by the at least one hose.
13. The system of Claim 12, wherein the detected amount of helium in the
enclosed
volume is compared to an ambient helium amount to determine the equilibrium
leak rate
of the joint assembly.

19


14. The system of Claim 10, wherein the at least two seals includes an
inboard seal
that engages an inside diameter of the calandria tube and an outboard seal
that engages a
face of the tube sheet.
15. The system of Claim 10, wherein the test tool further includes at least
one of a
threaded rod and a lead screw rotatable to expand at least one of the at least
two seals.
16. The system of Claim 10, wherein the test tool further includes at least
one tube for
supplying helium to at least one area outside of the enclosed volume to test
the tightness
of at least one of the at least two seals.
17. The system of Claim 10, further comprising at least one automated
controller for
controlling the valve.
18. The system of Claim 10, further comprising a cart for carrying the
pump.
19. The system of Claim 10, further comprising a control unit for logging
the plurality
of pressure readings.
20. The system of Claim 10, further comprising at least one shield plug for
supporting
the vacuum tube and for shielding radiation.


Description

Note: Descriptions are shown in the official language in which they were submitted.


= CA 2766465 2017-03-01
Attorney Docket No. 027813-9061-CA00
CALANDRIA TUBE ROLLED JOINT LEAK TEST TOOL AND SERVICE CART
RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Application No.
61/433,431 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
and, in particular, methods and apparatus for testing a calandria tube rolled
joint for a leak.
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] During retubing, calandria tubes are replaced, which requires
replacing calandria tube
rolled joints that hold the calandria tube in the reactor. Traditionally,
rolled joints are leak tested
by applying helium tracer gas to the calandria side of the rolled joint. The
helium tracer gas is
then pulled through the joint by a vacuum pump into a helium leak detector.
Deployment of this
traditional leak test method, however, is difficult due to the severe
constraints in accessibility and
the radioactive environment present during retubing operations. Furthermore,
this test often
requires a long test time and, once started, cannot be interrupted to perform
other diagnostic
functions without requiring that the test be restarted.
1

CA 2766465 2017-03-01
Attorney Docket No. 027813-9061-CA00
[0005] Therefore, embodiments of the present invention provide methods and
systems for
confirming the leak tightness of in-reactor calandria tube joints during
retube operations. One
embodiment of the invention provides a method for testing a joint assembly
coupling a calandria
tube to a tube sheet in a reactor. The method includes (a) inserting a test
tool into a lattice site
containing the joint assembly, the test tool including at least two seals that
define an enclosed
volume surrounding the joint assembly. The method also includes (b) drawing a
vacuum in the
enclosed volume, (c) stopping drawing the vacuum in the enclosed volume and
allowing the
vacuum to decay over a predetermined decay period, (d) measuring a change in
pressure in the
enclosed volume during the decay period and calculating a leak rate based on
the change in
pressure, (e) repeating (b) through (d) to generate a plurality of leak rates
and (f) determining an
equilibrium leak rate based at least on the plurality of leak rates.
[0006] Another embodiment of the invention provides a system for testing a
joint assembly
coupling a calandria tube to a tube sheet in a reactor. The system includes a
pump for drawing a
vacuum on an enclosed volume surrounding the joint assembly and a test tool
coupled to the
pump by at least one hose. The test tool includes a test tool head that
includes at least two seals
for defining the enclosed volume and an inlet for drawing the vacuum on the
enclosed volume.
The test tool also includes a pressure gauge for measuring a pressure in the
enclosed volume, a
vacuum tube for drawing the vacuum on the enclosed volume, and at least one
valve for
repeatedly drawing the vacuum on the enclosed volume and letting the vacuum
decay over a
predetermined decay period. The pressure gauge provides a plurality of
pressure readings in the
enclosed volume during the repeated drawings of the vacuum and vacuum decays,
the plurality
of pressure readings used to calculate an equilibrium leak rate of the joint
assembly.
[0007] Other aspects of the invention will become apparent by consideration
of the detailed
description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a perspective view of a CANDUTM reactor.
[0009] FIG. 2 is a cut-away view of a CANDUTm-type nuclear reactor fuel
channel
assembly.
2

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
[0010] FIG. 3 is a cross-sectional view of a calandria tube rolled joint
assembly before being
rolled according to some embodiments of the invention.
[0011] FIG. 4 is a cross-sectional view of the calandria tube rolled joint
assembly of FIG. 3
after being rolled according to some embodiments of the invention.
[0012] FIG. 5 is a cross-sectional view of the calandria tube rolled joint
assembly of FIG. 3
and potential leak paths associated with the rolled joint assembly.
[0013] FIG. 6 is a perspective view of a calandria tube rolled joint leak
test tool according to
some embodiments of the invention.
[0014] FIG. 7 is a flow chart illustrating a leak test method performed
using the leak test tool
of FIG. 6 according to some embodiments of the invention.
[0015] FIG. 8 is a cross-sectional view of the test tool of FIG. 6
installed in a lattice site.
[0016] FIG. 9 is a cross-sectional view of an enclosed volume generated
when the test tool of
FIG. 6 is installed in a lattice site.
[0017] FIG. 10 is a graph of a vacuum decay trend resulting from a vacuum
decay leak test
performed by the test tool of FIG. 6.
[0018] FIG. 11 is a graph of a vacuum decay trend resulting from a vacuum
decay leak test
performed by the test tool of FIG. 6 and an ambient helium trend resulting
from an ambient
helium leak test performed by the test tool of FIG. 6.
[0019] FIG. 12 is a cross-sectional view of areas supplied with helium
using the test tool of
FIG. 6 to test one or more seals of the test tool.
[0020] FIG. 13 is a graph of helium readings associated with a leaking seal
of the test tool of
FIG. 6.
[0021] FIG. 14 is a perspective view of a helium leak detector used with
the test tool of FIG.
6 according to some embodiments of the invention.
3

= CA 2766465 2017-03-01
Attorney Docket No. 027813-9061-CA00
[0022] FIG. 15 is a perspective view of a service cart used with the test
tool of FIG. 6
according to some embodiments of the invention.
DETAILED DESCRIPTION
[0023] 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.
[0024] 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.
[0025] 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 insert 34
within each bore is used to secure the CT 32 to the tube sheet 18 and form a
rolled joint
assembly.
[0026] 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 gas are part of an annulus gas system. The annulus gas system has two
primary functions.
4

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
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.
[0027] 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.
[0028] As also shown in FIG. 2, an end fitting 50 is attached around 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.
[0029] Coolant from the inlet feeder assembly flows along a 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 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.
[0030] 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

1
. . . , CA 2766465 2017-03-01
Attorney Docket No. 027813-9061-CA00
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.
[0031] 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.
[0032] 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.
[0033] During the retubing process, many of the components of the
reactor 6 are removed
and replaced. In particular, new fuel channel assemblies 28 are placed in the
reactor 6 after the
existing fuel channel assemblies 28 have been removed. In some embodiments,
the PTs 36 and
the CTs 32 are made from zirconium alloys and the end fittings 50 and the
calandria 10 are made
of stainless steel. Therefore, because welding zirconium to steel is not
possible, a mechanical
joint is used to attach the PTs 36 and the CTs 32 to the end-fittings 50 and
the calandria 10. In
particular, as noted above, a rolled joint assembly is used to secure the CT
32 to the tube sheet
18. Although not discussed in detail below, it should be understood that the
rolled joint
assembly used to secure the CTs 32 to the tube sheets 18 can be similar to a
rolled joint assembly
used to secure the PTs 36 to the end-fittings 50, and the methods and
apparatus discussed below
with respect to the rolled joint assembly used with the CTs 32 can also be
used to test the leak
tightness of a rolled joint assembly used with the PTs 36.
[0034] FIG. 3 illustrates a rolled joint ("RJ") assembly 90 used to
secure the CT 32 to the
tube sheet 18. As shown in FIG. 3, the RJ assembly 90 includes the CT 32, the
tube sheet 18,
and the CT insert 34. The CT insert 34 can be constructed from stainless steel
and can include
an insert flange 100 and a shoulder 102. The flange 100 abuts an outward face
104 of the tube
6

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
sheet 18, and the shoulder 102 abuts an inner surface area 106 of a bore in
the tube sheet 18. The
inner surface area 106 can include one or more grooves 110 that abut the
shoulder 102 of the CT
insert 34. As shown in FIG. 3, a gap 112 between the shoulder 102 and the
inner surface area
106 accepts the CT 32.
[0035] After the CT 34 is placed in the bore of the tube sheet 18 and the
CT 32 is positioned
within the gap 112, a rolling tool is used to deform and extend the CT insert
34, the tube sheet
18, and the CT 32 to sandwich the CT 32 between the CT insert 34 and the tube
sheet 18 and
form a mechanical joint between these components. As shown in FIG. 4, after
rolling the CT
insert 34, the flange 100 is deformed against the outward face 104 of the tube
sheet 18 and the
shoulder 102 extrudes into the grooves 110. Furthermore, the CT 32 is deformed
into the gap
112 between the CT insert 34 and the tube sheet 18.
[0036] FIG. 5 illustrates an installed RJ assembly 90. As shown in FIG. 5,
there are potential
leak paths 110 through the assembly 90. For example, the leak paths 110 can
include a path
between the CT 32 and the tube sheet 18 bore, where the moderator would leak
from the
calandria 10 into the lattice tube site, and a path between the CT 32 and the
CT insert 34, where
the moderator would leak from the calandria 10 into the CT 32.
[0037] In some embodiments, the newly-fabricated RJ assembly 90 must meet
leak tightness
criteria to ensure that the mechanical joint is tight enough for reactor
operation. Therefore, once
the RJ assembly 90 is installed (and before the PT 36 is installed inside the
CT 32), a test is
performed to verify the leak tightness of the RJ assembly 90. For example,
using a leak test as
described below, a RJ assembly 90 leak rate can be accurately quantified in a
range from
approximately 5x10-5 cc/s to approximately 5x10-3 cc/s. Therefore, the leak
test can be used to
identify RJ assemblies 90 having a leak rate outside of required engineering
specifications,
which can then be inspected and, in some situations, replaced to ensure proper
reactor operation.
[0038] The leak tightness of the installed RJ assembly can be tested using
a CT RJ leak test
tool. FIG. 6 illustrates a CT RJ leak test tool 200 according to one
embodiment of the invention.
In some embodiments, the test tool 200 is approximately 70.0 inches long and
includes a tool
head 202. The tool head 202 includes at least two seals 204. For example, as
shown in FIG. 6,
in some embodiments, the tool head 202 includes an inboard seal 204a and an
outboard or face
7

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
seal 204b. The seals 204a and 204b can be constructed from rubber and can
include o-rings.
The inboard seal 204a seals axially onto an inner diameter of the CT 32 and
the outboard seal
204b seals on the outward face 104 of the tube sheet 18. As described below in
more detail, the
tool head 202 is inserted inside the CT 32 and the seals 204 are used to
create an enclosed
volume around the RJ assembly 90.
[0039] As shown in FIG. 6, the tool head 202 is attached to a vacuum tube
206. The vacuum
tube 206 is used to create the vacuum in an enclosed area around the RJ
assembly 90. In
particular, as shown in FIG. 6, the tool head 202 includes an inlet 208 that
connects with the
vacuum tube 206 and is used to draw the vacuum around the RJ assembly 90. One
or more
shield plugs 210 (e.g., split shield plugs) can be used to support the vacuum
tube 206 and the tool
head 202. The shield plugs 210 can also be used to balance the weight of the
tool 200 and keep
the tool 200 straight as the tool 200 is inserted into a lattice site. The
shield plugs 210 can also
be used to provide shielding from radiation escaping through the lattice site.
[0040] The tool 200 also includes one or more valves 212 used to draw and
stop drawing the
vacuum around the RJ assembly 90. In addition, as shown in FIG. 6, the tool
200 includes one
or more pressure gauges 213 (e.g., Pirani Gauges). The pressure gauges 213
provide a pressure
reading within the vacuum tube 206 and, subsequently, a pressure reading
within the enclosed
area around the RJ assembly 90. The pressure gauges 213 can also be used to
verify that one or
both valves 212 have closed or opened properly. For example, each valve 212
can be associated
with a pressure gauge and, when one valve 212 should be opened or closed, the
pressure valve
associated with the other valve 212 can be used to verify that valve 212
opened or closed
properly. Providing this diagnostic functionality allows issues with the test
tool 200 to be
identified as soon as possible and allows issues to be corrected before test
readings are generated.
In some embodiments, the valves 212 are operated automatically by various
automated
controllers. In other embodiments, the valves 212 are operated manually by one
or more human
operators. Similarly, readings from the pressure gauge(s) 213 can be collected
manually or can
be automatically logged or transmitted to a control system.
[0041] The vacuum tube 206 is also connected to a helium leak detector 214
(e.g., an Alcatel
Helium Leak Detector) that includes a pump, such as a turbo pump or a roughing
pump. The
8

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
pump is used to create the vacuum around the RJ assembly 90. The helium leak
detector 214
also detects a level of helium in the gas drawn from around the RJ assembly 90
to create the
vacuum. The vacuum tube 206 can be connected to the helium leak detector 214
by a flexible
hose 216, such as a bellows hose.
[0042] As shown in FIGS. 6 and 8, the test tool 200 can also include a
threaded rod or lead
screw 218 contained within a hollow tube 220. The hollow tube 220 can be used
to support and
shield the components of the tool 200, such as the threaded rod or lead screw
218. The shield
plugs 210 can also support the hollow tube 220.
[0043] The threaded rod or lead screw 218 is used to expand and retract the
inboard seal
204a. In particular, to allow the tool head 202 to be inserted into the
lattice site, the inboard seal
204a can be positioned in a retracted position. After the tool head 202 is
inserted in the CT 32,
the threaded rod or lead screw 218 can be actuated (e.g., rotated) to radially
expand the inboard
seal 204a to create a tight seal between the seal 204a and the CT 32. A handle
or wrench 224
located at a tool face 222 can allow an operator (or automated controllers) to
actuate the threaded
rod or lead screw 218.
[0044] The test tool 200 can also include a pair of stainless steel tubes
230. As described
below in more detail, the stainless steel tubes 230 supply a helium gas
mixture to one or more
areas of the tool head 202. In particular, a first stainless steel tube 230a
can supply helium gas to
the inside of the CT 32 inboard of the inboard seal 204a (toward the center of
the calandria 10).
The second stainless steel tube 230b can supply a helium gas mixture to the
lattice site outboard
of the outboard seal 204b (toward the face of the reactor 6). As described in
more detail below,
the helium supplied by the stainless steel tubes 230a and 230b are used to
test the seals 204a and
204b of the test tool 200. The stainless steel tubes 230a and 230b can be
connected to one or
more supply bottles of a helium gas mixture (e.g., 1% helium nitrogen) (see
FIG. 15).
[0045] FIG. 7 illustrates a method of using the test tool 200 to test the
leak tightness of a RJ
assembly 90. As shown in FIG. 7, to start the method, the test tool 200 is
inserted into the CT 32
after the RJ assembly 90 has been installed but before the PT 36 is installed
(at 300). FIG. 8
illustrates the test tool 200 inserted into the CT 32. As shown in FIG. 8, the
test tool head 202 is
inserted into the CT 32 until the outboard seal 204b engages the outward face
104 of the tube
9

CA 02766465 2012-01-16
= Attorney Docket No. 027813-9061-CA00
sheet 18. Therefore, the outboard seal 204b engages with the outward face 104
of the tube sheet
18 to create one side of the volume to be vacuumed. The inboard seal 204a
engages with an
inner diameter of the CT 32 and, as noted above, can be engaged with the CT 32
using the
threaded rod or lead screw 218. It should be understood that using the
threaded rod or lead
screw 218 to expand the seal 204a is optional, and, in some embodiments, the
inboard seal 204a
is not selectively expandable and is inserted into the CT 32 in an expanded
position. In addition,
in some embodiments, the outboard seal 204b can also be selectively expanded
and retracted
using the threaded rod or lead screw 218 or a similar actuating mechanism.
[0046] As shown in FIG. 8, with the test tool 200 inserted in the
CT 32, the seals 204a and
204b define an enclosed volume 310 around a perimeter of the inside diameter
of the CT 32 that
surrounds the RJ assembly 90. Returning to FIG. 8, once the test tool 200 is
inserted into the CT
32, a vacuum decay test is performed. As shown in FIG. 8, the vacuum decay
test includes using
the vacuum tube 206 and the pump included in the helium leak detector 214 to
draw a vacuum
on the enclosed volume 310 (at 310). In some embodiments, the vacuum is drawn
for
approximately two to five minutes. FIG. 9 illustrates the test tool 200 with a
vacuum drawn on
the enclosed area 310.
[0047] After the vacuum is drawn, the vacuum is no longer drawn for
a period of time (a
"decay period") (e.g., approximately two minutes) while the enclosed volume
310 remains
sealed (i.e., the pump included in the helium leak detector 214 is turned off
or disconnected from
the tool 200, such as through the use of the valves 212) (at 312). For
example, one or both of the
valves 212 are closed during the decay period, which stops the pump from
drawing a vacuum in
the enclosed volume 310. During the decay period, the vacuum decays (i.e., the
enclosed
volume 310 begins to re-pressurize) due to ambient air leaking through the RJ
assembly 90
(along one or more of the leak paths 110) at a rate that depends on the size
of the leak. In
particular, the higher pressure of the ambient air is drawn through the leak
paths 110 due to the
lower pressure inside the enclosed volume 310. As ambient air leaks through
the leak paths 110,
the pressure inside the enclosed area 310 increases. Therefore, during the
decay period and/or at
the end of the decay period, the pressure inside the enclosed volume 310 is
measured (e.g., using
the pressure gauges 213) (at 314). The change in pressure within the enclosed
volume 310
during the decay period, the length of time of the decay period, and the
volume of the enclosed

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
volume 310 is used to calculate a vacuum decay leak rate. In particular, a
vacuum decay leak
rate can be calculated using the following equation:
[0048] q = V dP
di'
Where q is the decay leak rate and V is the volume of the enclosed volume 310.
[0049] As shown in FIG. 7, the vacuum decay test described above can be
repeated one or
more times to obtain a vacuum decay trend. In particular, after the decay
period, the vacuum can
be redrawn (e.g., by reopening one or both of the valves 212) for
approximately two to five
minutes (at 310) and then can be allowed to decay again for the decay period
(at 312) while the
pressure of the enclosed volume 310 is measured (at 314). With each repeated
vacuum decay
leak test, the calculated vacuum decay lake rate gravitates toward an actual
or equilibrium leak
rate.
[0050] For example, FIG. 10 illustrates a vacuum decay trend 400 that
illustrates the
measured pressure (in Torres) within the enclosed volume 310 as the vacuum is
drawn and then
allowed to decay numerous times. As shown in FIG. 10, the pressure (in Torres)
can be
measured substantially continuously or can be measured at predetermined time
intervals. As also
shown in FIG. 10, the pressure rises during each decay period (e.g., at 300
seconds, at 600
seconds, at 900 seconds, etc.). Similarly, after the decay period has ended
and one or both of the
valves 212 are reopened (e.g., at 400 seconds, at 700 seconds, at 1000
seconds, etc.), the pressure
decreases as the vacuum is redrawn on the enclosed volume 310. As shown in
FIG. 10, the
slopes of the pressures changes during each vacuum decay leak test decrease
over time due to the
evacuation of cavities included in the enclosed volume 310 and due to reduced
off-gassing. Off-
gassing occurs when a vacuum is drawn in the enclosed volume 310 and draws
molecules off the
surface of components of the test tool 200, the CT 32, and/or other components
included in the
reactor 6. The drawn molecules take on a gaseous form that add to the volume
of gas within the
enclosed volume 310, which results in an increased pressure within the
enclosed area 310.
Therefore, pressure rises due to off-gassing can provide a false indication of
a high leak rate for a
RJ assembly 90. However, as shown in FIG. 9, the effect of off-gassing
decreases over time
with each vacuum decay test. Therefore, running multiple vacuum decay tests
reduces the effect
11

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
of off-gassing in the results of the test. Furthermore, observing a decreasing
linear trend in the
off-gassing effect ensures an operator that the RJ assembly 90 is operating
properly and provides
a faster result than other vacuum decays tests that are run only once for an
extended period of
time. In addition, observing the trend of the off-gassing effect can provide
diagnostic
information to an operator. For example, the trend or shape of the off-gassing
effect can signify
whether other (e.g., non-metal) debris is located inside the CT 32 and/or
other locations of the
reactor that may cause operational concerns.
[0051] Returning to FIG. 7, in some embodiments, the test tool 200 can also
be used to
perform an ambient helium leak test. Also, as illustrated in FIG. 7, in some
embodiments, the
ambient helium leak test can be performed simultaneously with the vacuum decay
test. For
example, while the vacuum decay test is being performed, the helium leak
detector 214 can
measure the amount of helium inside the enclosed volume 310 (at 320). The
measured amount
of helium can be compared to the amount of ambient helium in the air
surrounding the reactor 6
(e.g., approximately 5.2 ppm). Therefore, the amount of helium measured in the
enclosed
volume 310 will depend on the leak size. In particular, the larger the size of
the leak, the closer
the amount of helium measured in the enclosed volume 310 will be to the
ambient helium
amount. For example, an ambient helium leak rate can be calculated using the
following
equation:
[0052] = ____________
Helium Reading
q
AmbientHelium
[0053] As shown in FIG. 7, the ambient helium leak test can be repeated
(e.g., repeated each
time the vacuum decay test is performed) to obtain multiple leak rate
calculations. For example,
FIG. 11 illustrates a helium leak rate trend 500 graphed over vacuum decay
rates. As illustrated
in FIG. 11, over time, the ambient helium leak rate approaches the vacuum
decay leak rate.
Therefore, both rates reach a leak rate that represents a true or equilibrium
leak rate for the RJ
assembly 90. The time before the rates reach the equilibrium leak rate depends
on the size of the
leak. For example, the larger the leak, the faster the rates will reach the
equilibrium leak rate.
The equilibrium leak rate can be compared to engineering specifications to
ensure that the RJ
assembly 90 is properly installed and ready for operational use.
12

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
[0054] Executing the ambient helium leak test and the vacuum decay leak
test
simultaneously as described above allows a user to ensure accuracy of the
result, and the ambient
helium leak test provides secondary confirmation of the test results of the
vacuum decay leak
test. Furthermore, running the two tests simultaneously creates a leak rate
measurement
approximately every five minutes. Therefore, if an acceptable leak rate is
reached early in the
test, the test duration is shortened. Furthermore, the transient trend from
the vacuum decay leak
test allows the test to be optimized with respect to the duration of the test.
The transient trend
from the vacuum decay leak test also provides additional information about the
conditions under
testing, such as off-gassing as described above.
[0055] Returning to FIG. 7, in some embodiments, the test tool 200 can be
tested to ensure
that it is properly installed in the lattice site. For example, if the seals
204 of the test tool 200 are
not tight, the vacuum decay leak test and the ambient helium leak test cannot
be performed
successfully. In particular, if one or both of the seals 204 are not secure, a
large pressure rise
will be measured during the vacuum decay test and an ambient helium amount
will be measured
during the ambient helium leak test, both of which will result in a false leak
rate for the RJ
assembly 90.
[0056] To prevent these false leak rates, after the test tool 200 is
installed, the seals 204a and
204b can be tested (at 330). In particular, the stainless steel tubes 230 can
be used to supply
helium to areas outside of the enclosed volume 310 (e.g., each end of the
enclosed volume 310 as
defined by the seals 204a and 204b). For example, FIG. 12 illustrates the test
tool 200 and the
stainless steel tubes 230. With the test tool 200 installed in the lattice
site, the first stainless steel
tube 230a extends past the inboard seal 204a and supplies helium to an area
600 between the
inboard seal 204a and the end of the test tool 200 inserted into the CT 32. If
the inboard seal
204a is not properly sealed to the CT 32, the supplied helium will leak into
the enclosed volume
310 and will be detected by the helium leak detector 214. Similarly, as shown
in FIG. 12, the
second stainless steel tube 230b supplies helium to an area 610 between the
outboard seal 204b
and the tool face 222. If the outboard seal 204b is not properly sealed to the
tube sheet 18, the
supplied helium will leak into the enclosed volume 310 and will be detected by
the helium leak
detector 214.
13

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
100571 As described above, because the ambient helium leak test uses only
ambient helium
(as compared to supplied helium as used in existing helium leak tests), a
large amount of helium
detected by the helium leak detector 214 (i.e., an amount greater than the
ambient helium
amount) indicates that one or both of the seals 204a and 204b is leaking and
the test should be
stopped and restarted (e.g., the test tool 200 should be repositioned) to
ensure a proper leak test is
performed. For example, FIG. 13 illustrates a graph 700 of sample helium
readings from the
helium leak detector 214 when the inboard seal 204a is leaking. As illustrated
in FIG. 13, when
the inboard seal 204a leaks, the helium leak detector 214 detects a high level
of helium when the
vacuum is drawn on the enclosed volume 310 (e.g., at approximately 400
seconds) because the
supplied helium at the area 600 has leaked into the enclosed volume 310.
[0058] As illustrated in FIG. 7, the seal test (at 330) can be performed
simultaneously with
the vacuum decay leak test and the ambient helium leak test. In fact, because
the ambient helium
leak test detects the amount of helium in the enclosed area 310 (at 320), the
helium
measurements taken for the ambient helium leak test are the same measurements
needed to
perform the seal test (at 330). In some embodiments, the seals 204a and 204b
are tested before
beginning the decay period. However, the seals 204 can be tested at any stage
when the pump
valve drawing the vacuum is open (i.e., anytime the vacuum is being drawn).
Also, in some
embodiments, the helium supplied through the stainless steel tubes 230 can be
controlled (e.g.,
automatically or manually) to turn the helium supply on and off For example,
in some
embodiments, the helium supplied through the stainless steel tubes 230 is
turned on when the
vacuum is drawn on the enclosed volume 310 and is turned off when the vacuum
is no longer
drawn (i.e., during the vacuum decay period). Also, in some embodiments, the
helium supplied
by each stainless steel tube 230 can be controlled independently and turned on
and off to test
each seal 204 separately. Testing each seal 204 separately can identify which
of the two seals
204 (if either) is leaking. It should be understood that the stainless steel
tubes 230 are optional
and, in some embodiments, only one stainless steel tube 230 is used to supply
helium to one or
multiple areas to test the tightness of one or both seals 204 of the test tool
200. For example, in
some embodiments, only one stainless steel tube 230 is used to test the
tightness of the outboard
seal 204b.
14

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
[0059] In some embodiments, the helium leak detector 214 can be installed
on a cart 800 as
illustrated in FIG. 14. The cart 800 can include a handle and wheels that
allow the cart 800 to be
positioned as needed during the leak testing of a RJ assembly 90. In some
embodiments, the cart
800 is installed on a larger cart 900 as illustrated in FIG. 15. The larger
cart 900 can hold the
cart 800 and one or more supply bottles 902 that supply a helium gas mixture
to the stainless
steel tubes 230. The cart 900 can be approximately 55.0 inches long,
approximately 24.0 inches
wide, and approximately 54.0 inches high.
[0060] The carts 800 and 900 can include connections for connecting the
test tool 200 to the
carts 800 and 900 and/or the components carried on the carts 800 and 900. In
some
embodiments, the cart 800 and/or the cart 900 can also include the valves 212
and the pressure
gauges 213 (or valves and gauges in addition to the valves 212 and gauges 213
on the test tool
200). The cart 800 and/or the cart 900 can also include a local control panel
("LCP") unit that
allows an operator to program the helium leak detector 214 and/or other
components carried on
the cart 800 and/or the cart 900. In some embodiments, the LCP unit can also
provide a data log
and summary report file of the vacuum decay leak test, the ambient helium leak
test, and/or the
seal test.
[0061] It should be understood that in practice, multiple test tools 200
(and associated carts
800 and 900) can be used to test the leak tightness of a RJ assembly 90. For
example, in some
embodiments, thirty-eight test tools 200 can be used, including twenty-four
for production use,
twelve for use a spares, and two for training purposes. Similarly, six carts
900 can be used,
including two for production use, two for use as spares, and two for training
purposes. Using the
multiple test tools 200 and carts 900 separates the testing process into semi-
independent batch-
type operations, which increases efficiency. For example, using multiple test
tools 200 and
associated carts allows RJ assemblies 90 at multiple lattice sites on the same
or opposite end of
the reactor 6 to be tested in parallel.
[0062] Also, maintenance can be performed on the test tool 200 to ensure
that the test tool
200 functions properly over time. For example, in some embodiments, the seals
204a and 204b
of the test tool 200 can become worn with use and can be replaced regularly to
maintain the
quality and consistency of the test. In some embodiments, the seals 204 can be
replaced after

CA 02766465 2012-01-16
Attorney Docket No. 027813-9061-CA00
every five test operations. The pressure gauges 213 of the tool 200 can also
be calibrated
annually. In addition, the helium leak detector 214 can include a calibrated
leak sensor, which
can be replaced or re-calibrated as recommended by the manufacturer.
[0063] It should be understood that although the above testing methods and
systems are
described as being used during a retubing process, the same methods and
systems can be used to
perform maintenance and tests of operating reactors. For example, if a
particular fuel channel
assembly 28 is malfunctioning in a reactor, the tightness of the RJ assembly
90 can be tested to
identify whether the RJ assembly 90 is malfunctioning. In this situation, the
PT 36 can be
removed to allow the test tool 200 to access to the RJ assembly 90.
[0064] Thus, embodiments of the present invention provide, among other
things, methods
and tools for testing the leak tightness of a RJ assembly. 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, the inserts, and/or the
reactor being retubed.
[0065] Various features and advantages of the invention are set forth in
the following claims.
16

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

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Administrative Status

Title Date
Forecasted Issue Date 2018-01-02
(22) Filed 2012-01-16
(41) Open to Public Inspection 2012-07-17
Examination Requested 2016-10-20
(45) Issued 2018-01-02

Abandonment History

There is no abandonment history.

Maintenance Fee

Last Payment of $263.14 was received on 2023-12-21


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Next Payment if small entity fee 2025-01-16 $125.00
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Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $400.00 2012-01-16
Maintenance Fee - Application - New Act 2 2014-01-16 $100.00 2014-01-03
Maintenance Fee - Application - New Act 3 2015-01-16 $100.00 2015-01-13
Maintenance Fee - Application - New Act 4 2016-01-18 $100.00 2016-01-04
Request for Examination $800.00 2016-10-20
Maintenance Fee - Application - New Act 5 2017-01-16 $200.00 2017-01-04
Final Fee $300.00 2017-11-09
Maintenance Fee - Application - New Act 6 2018-01-16 $200.00 2017-12-15
Maintenance Fee - Patent - New Act 7 2019-01-16 $200.00 2019-01-15
Maintenance Fee - Patent - New Act 8 2020-01-16 $200.00 2020-01-10
Maintenance Fee - Patent - New Act 9 2021-01-18 $204.00 2021-01-08
Maintenance Fee - Patent - New Act 10 2022-01-17 $255.00 2021-12-16
Maintenance Fee - Patent - New Act 11 2023-01-16 $254.49 2022-12-16
Maintenance Fee - Patent - New Act 12 2024-01-16 $263.14 2023-12-21
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
ATOMIC ENERGY OF CANADA LIMITED
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Abstract 2012-01-16 1 22
Description 2012-01-16 16 854
Claims 2012-01-16 4 114
Representative Drawing 2012-03-13 1 42
Cover Page 2012-07-10 1 78
Final Fee 2017-11-09 2 69
Representative Drawing 2017-12-04 1 28
Cover Page 2017-12-04 1 63
Assignment 2012-01-16 5 178
Request for Examination 2016-10-20 1 50
Prosecution-Amendment 2016-10-28 1 28
Examiner Requisition 2016-12-01 5 323
Amendment 2017-03-01 268 1,807
Amendment 2017-03-02 8 187
Claims 2017-03-01 4 112
Description 2017-03-01 16 857
Drawings 2017-03-02 14 445