Annulus spacer for fuel channel assembly of a nuclear reactor and methods of detecting same

Abstract

An annulus spacer for a fuel channel assembly of a nuclear reactor is provided. The annulus spacer comprises a girdle wire forming a loop around a pressure tube of the reactor. The girdle wire has an expansion mechanism and defines a first circumference when the expansion mechanism is in a first configuration and a second circumference when the expansion mechanism is in a second configuration. The girdle wire transitions from the first configuration to the second configuration during diametral expansion of the pressure tube, where the expansion mechanism maintain a first end and a second end of the girdle wire in electrical communication in both the first and second configurations to maintain the loop of the girdle wire as a continuous electrical circuit. A garter spring defines the girdle wire within the garter spring and maintain a gap between the calandria tube and the pressure tube.

Description

ANNULUS SPACER FOR FUEL CHANNEL ASSEMBLY OF A NUCLEAR REACTOR AND METHODS OF DETECTING SAMECROSS REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY

[0001] The present application claims priority to U.S. provisional patent application no. 63 / 660,633 filed on June 17, 2024, the entire contents of which are hereby incorporated by reference.TECHNICAL FIELD

[0002] The disclosure relates generally to fuel channels of a nuclear reactor and more particularly to an annulus spacer for use in the fuel channel of a heavy water nuclear reactor.BACKGROUND

[0003] Annulus spacers are positioned around pressure tubes of heavy water nuclear reactors, also known as Pressurized Heavy Water Reactors (PHWR), between the pressure tube and its respective calandria tube. Annulus spacers are required to roll along the pressure tube during operation of the nuclear reactor as the pressure tube expands in length relative to the surrounding calandria tube. However, as the pressure tube undergoes diametric expansion of the pressure tube, the girdle wire of the annulus spacer may pinch against the inside surface of the coil of the garter spring which restricts the annulus spacer from rolling along the pressure tube. Diametric expansion of the pressure tube may even break the girdle wire of the annulus spacer which may prevent the annulus spacer from being located by eddy current testing which is a preferred method for determining the location of the annulus spacer.SUMMARY

[0004] An annulus spacer for a fuel channel assembly of a nuclear reactor and methods of detecting same are described in this disclosure. These systems and methods may be employed at a nuclear reactor.

[0005] In an aspect, an annulus spacer for a fuel channel assembly of a nuclear reactor is provided. The fuel channel assembly comprises a calandria tube and a pressure tube positioned at least partially within the calandria tube, the annulus spacer comprising: a girdle wire comprising an expansion mechanism, the girdle wire forming a loop around the pressure tube, the girdle wire having a first end and a second end, the girdle wire defining a first circumference when the expansion mechanism is in a first configuration and a second circumference when the expansion mechanism is in a second configuration, the girdle wire transitioning from the first configuration tothe second configuration during diametral expansion of the pressure tube, the expansion mechanism maintaining first end and the second end in electrical communication in both the first and second configurations for maintaining the loop of the girdle wire as a continuous electrical circuit; and a garter spring defining the girdle wire within the garter spring, the garter spring configured to surround a portion of the pressure tube to maintain a gap between the calandria tube and the pressure tube.

[0006] In an embodiment, the girdle wire forms a unitary loop in the first configuration.

[0007] In another embodiment, the expansion mechanism comprises a notched portion proximate to the first end which is secured to secured to the girdle wire, the notched portion configured to break during diametral expansion of the pressure tube as the girdle wire transitions from the first configuration to the second configuration, wherein the girdle wire does not form a unitary loop when the notched portion breaks.

[0008] In another embodiment, the expansion mechanism comprises a sleeve receiving the second end to form the loop. In an example, the second end is slidably received within the sleeve, the second end retracting within the sleeve when the girdle wire transitions from the first configuration to the second configuration.

[0009] In another embodiment, the expansion mechanism comprises a flexible portion configured to straighten when the girdle wire transitions from the first configuration to the second configuration during diametral expansion of the pressure tube. In an example, the flexible portion is proximate the first end, and wherein the first end is coupled to girdle wire. In another example, the flexible portion is a braided wire, coil, or curved wire. In another example, the flexible portion is welded or brazed to a connector. In another example, the first end is welded or brazed to a portion of the girdle wire such as second end. In another example, the braided wire portion comprises between about 10-270 degrees of the loop and / or about 270 degrees of the loop.

[0010] In another embodiment, the expansion mechanism comprises a plurality of kinks defining wave-shaped pattern, the plurality of kinks defining a first angle between adjacent kinks in the first configuration and a second angle between adjacent kinds in the second configuration, the second angle greaterthan the first angle. In an example, the plurality of kinks defined at least 270 degrees of the loop.

[0011] In another embodiment, the expansion mechanism comprises a spring, where the first end of the girdle wire is coupled to one end of the spring of the expansion mechanism and the second end of the girdle wire is coupled to a second end of the expansion mechanism.

[0012] In another embodiment, the girdle wire comprises a coating, the coating comprising at least one of zirconium nitrite (ZrN), titanium nitride (TiN), nickel, chromium, rhenium, ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold.

[0013] In another embodiment, the girdle wire comprises stainless steel, nickel alloy, copper alloy, zirconium alloy, and aluminum bronze.

[0014] In another embodiment, the garter spring comprises stainless steel, nickel alloy, copper alloy, zirconium alloy, and aluminum bronze.

[0015] In another embodiment, at least one of the girdle wire and garter spring are ferromagnetic.

[0016] In another embodiment, the girdle wire is configured to both elastically lengthen and the expansion mechanism is configured to uncoil during transition from the first configuration to the second configuration to increase the first circumference to the second circumference.

[0017] In another embodiment, opposing ends portions of the garter spring are coupled by a structural weld, and wherein the garter spring comprises non-structural welds coupling a first and second portion of the garter spring for maintaining electrical conductivity between the first and second portion.

[0018] In another embodiment, the annulus spacer comprises a connector, connecting joint, or sleeve joint to couple opposing end portions of the garter spring, wherein opposing end portions are coupled by at least one non-structural weld, wherein the connector, connecting joint, or sleeve joint unloads the least one non-structural weld.

[0019] Embodiments may include combinations of the above features.

[0020] In another aspect, a method of detecting a position of an annulus spacer between a calandria tube and a pressure tube of a nuclear reactor is provided. The method comprises: positioning an annulus spacer according to this disclosure around a pressure tube in the first configuration, where the annulus spacer is positioned between the pressure tube and the calandria tube; and detecting a location of the annulus spacer by eddy current testing when the expansion mechanism is in the second configuration.

[0021] In an embodiment, the method comprises determining the location of the annulus spacer when expansion mechanism is in the first configuration.

[0022] In an embodiment, the girdle wire elastically lengthens and the expansion mechanism uncoils during transitioning from the first configuration to the second configuration to increase the first circumference to the second circumference.

[0023] Embodiments may include combinations of the above features.

[0024] In another aspect, a method of locating and repositioning an annulus spacer between a calandria tube and a pressure tube of a nuclear reactor is provided. The method comprises: providing the annulus spacer of according to this disclosure around a pressure tube at a first position along the length of the pressure tube; applying a magnetic field to the annulus spacer; and moving the annulus spacer to a second position along the length of the pressure tube with the magnetic field.

[0025] In an embodiment, the magnetic field is created with a Spacer Locating and Repositioning (SLAR) tool.

[0026] Further details of these and other aspects of the subject matter of this application will be apparent from the detailed description included below and the drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a perspective view of a reactor core of a CANDU-type nuclear reactor.

[0028] FIG. 2 is a cut away view of a CANDU-type nuclear reactor fuel channel assembly.

[0029] FIG. 3 is a perspective view of an annulus spacer installed in the fuel channel of a CANDU- type nuclear reactor.

[0030] FIGs. 4A and 4B are schematic views of an example of annulus spacer lock-up where the girdle wire pinches a garter spring against a pressure tube.

[0031] FIGs. 5A-5B illustrate an plane view of example annulus spacers according to this disclosure. FIG. 5C illustrated an enlarged fragmentary view of a portion of the example annulus spacer shown in FIG. 5B.

[0032] FIGs. 6A is a plan view of another example girdle wire for an annulus spacer. FIG. 6B is a side cut away view of the example girdle wire shown in FIG. 6A. FIG. 6C is an enlarged fragmentary view of detail B of FIG. 6A. FIG. 6D is an enlarged cutaway fragmentary view of detail A in FIG. 6A.

[0033] FIGs. 7A is a plan view of another example embodiment of a girdle wire for an annulus spacer. FIG. 7B is an enlarged fragmentary view of the expansion mechanism shown in FIG. 7A transitioning to a larger circumference.

[0034] FIG. 8A is a plan view of another example embodiment of a girdle wire for an annulus spacer. FIG. 8B is an enlarged fragmentary view of the expansion mechanism shown in FIG. 8A transitioning to a larger circumference.

[0035] FIG. 9A is a plan view of another example embodiment of a girdle wire for an annulus spacer. FIG. 9B is an enlarged fragmentary view of the expansion mechanism shown in FIG. 9A transitioning to a larger circumference.

[0036] FIG. 10A is an enlarged fragmentary view of an example connector of detail B in FIG. 9A. FIG. 10B is a cross-sectional view of the example connector of FIG. 10A. FIG. 10C is an enlarged fragmentary view of an example connector of detail C in FIG. 9A.

[0037] FIGs. 11 A is a plan view of another example embodiment of a girdle wire for an annulus spacer. FIG. 11 B is an enlarged cutaway fragmentary view of the expansion mechanism shown in FIG. 11 A.

[0038] FIG. 12A is a fragmentary view of an example embodiment of an annulus spacer; and FIG. 12B is a cut away view of the annulus spacer of FIG. 12A.

[0039] FIG. 13 is a schematic diagram illustrating an example method of detecting a position of an annulus spacer between a calandria tube and a pressure tube of a nuclear reactor.

[0040] FIG. 14 is a schematic diagram illustrating an example method of locating and repositioning an annulus spacer between a calandria tube and a pressure tube of a nuclear reactor.DETAILED DESCRIPTION

[0041] This disclosure provides annulus spacers comprising a girdle wire having features to mitigate against annulus spacer lock-up where the girdle wire pinches a garter spring against a pressure tube; and / or to improved detectability of the position of the girdle wire on the pressure tube fora longerduration ofthe annulus spacer’s lifecycle within a nuclear reactor. Gartersprings according to this disclosure may also comprises non-structural coil-weld which provide improved moveability ofthe annulus spacer along the pressure tube. Non-structural weld(s) are not loaded and may be provided to maintain the garter spring as a continuous loop for improved electrical / magnetic detection and / or movement rather than structural purposes.

[0042] DEFINITIONS

[0043] Although terms such as “maximize”, “minimize” and “optimize” may be used in the present disclosure, it should be understood that such term may be used to refer to improvements, tuning and refinements which may not be strictly limited to maximal, minimal or optimal.

[0044] The term “connected” or "coupled to" may include both direct coupling (in which two elements that are coupled to each other and contact each other) and indirect coupling (in which at least one additional element is located between the two elements).

[0045] The term “substantially” as used herein may be applied to modify any quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related.

[0046] Terms such as "up to", "at least", "greater than", "less than", "more than", "or more", and the like, include the number recited and such terms refer to ranges that can be subsequently broken down into sub-ranges. In the same manner, all ratios recited herein also include all subratios falling within the broader ratio.

[0047] The singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. The term "and / or" means any one of the items, any combination of the items, or all of the items with which this term is associated.

[0048] The term "about" can refer to a variation oft 5%, ± 10%, ± 20%, or± 25% of the value specified. For example, "about 50" percent can in some embodiments carry a variation from 45 to 55 percent. For integer ranges, the term "about" can include one or two integers greater than and / or less than a recited integer at each end of the range. Unless indicated otherwise herein, the term "about" is intended to include values and ranges proximate to the recited range that are equivalent in terms of the functionality of the composition, or the embodiment.

[0049] The term “unitary loop” describing a girdle wire may mean that the ends of the girdle wire are fixed to another portion of the girdle wire to form an integral loop. A connector may maintain contact between the end, or end portion, of the girdle wire and the other portion of the girdle wire to form the unitary loop. The connector may be a weld, braise, sleeve, connecting joint, sleeve joint, or other coupling member providing a fixed connection. In an example, the ends, or end portion, of the girdle wire may be welded or braised to another part of the girdle wire to form an integral loop, i.e. the unitary loop. In another example, overlapping portions of the girdle wire that are not secured together, e.g. like a key chain, is a non-unitary loop such as the girdle wire of FIG. 3.

[0050] Aspects of various embodiments are described through reference to the drawings.

[0051] FIG. 1 is a perspective of a reactor core of a CANDU-type reactor 6. 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 second end 24. A number of fuel channel assemblies 28 pass through the calandria 10 from the first end 22 to the second end 24.

[0052] 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 channels assemblies 28. A pressure tube (PT) 36 forms an inner wall of the fuel channel assembly 28. The PT 36 provides a conduit for reactor coolant and fuel assemblies 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, 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 indication of a leaking calandria tubes, pressure tubes 36, or their connections via the presence of moisture in the annulus gas.

[0053] An annulus spacer 48 is disposed between the CT 32 and PT 36. Functionally, the annulus spacer 48 serves roles in ensuring the safe, long-term operation of CANDU-type nuclear reactors. 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. More specifically, the annulus spacer 48 substantially minimizes the risk of contact between the CT 32 and PT 36 under Design Level A and B service conditions and Level C transients for the design life of the fuel channel, with the exception of a design basis earthquake with a fueling machine attached. The PT 36 would be inspected after such an earthquake, and if significant permanent deformation or damage has taken place, shall be replaced.

[0054] The annulus spacer 48 limits heat transfer from the PT 36 to the heavy-water moderator during normal operating conditions, thus increasing the thermal efficiency of the reactor, and ensuring that hot PTs 36 are not locally cooled. Thermal gradients in the wall of a PT 36 can permit hydrogen (deuterium) diffusion along the gradient above threshold hydrogen concentrations. High hydrogen concentrations may allow hydride accumulation and the potential for unstable cracking during the PT 36 design life.

[0055] Other functions of the annulus spacer 48 include accommodating relative axial movement between the PT 36 and CT 32 while limiting wear / scratches / deformation / damage to the PTs 36 and CTs 32, so that integrity and performance are maintained throughout the design life of the fuel channel. The annulus spacers 48 are configured to withstand the annulus gas environmental conditions without substantial degradation for the design life of the fuel channel. The annulus spacer 48 is further configured to limit parasitic neutron absorption and thereby reduce the fuel bum-up penalty by careful selection of spacer dimensions, spring cross-section, geometry, connections, and material.

[0056] The performance requirements of the annulus spacer 48 are primarily based upon the functional requirements. In some embodiments, the annulus spacer 48 may withstand the maximum predicted PT 36 to CT 32 vertical interaction load specified in the applicable Fuel Channel Design Specification, without impeding the functional requirements of the spacer design or causing unacceptable deformation to the PT 36 or the CT 32. As shown in FIG. 3, and 6A, annulus spacer 48 may comprise a garter spring which is a coil spring. In some embodiments, the cross-section of the annulus spacer 48 is optimized as a square shape in order to maximize the load bearing capability in bending while minimizing the amount of material used. The annulus spacer 48 may also withstand PT to CT movement caused by the predicted number of thermal cycles and PT axial elongation specified in an applicable Fuel Channel Design Specification without impeding the functional requirements of the annulus spacer design or causing unacceptable deformation / wear to the PT 36 or the CT 32. Additionally, the annulus spacer 48 may withstand a maximum predicted diametral increase of the PT 36 specified in an applicable Fuel Channel Design Specification without nip-up. Nip-up occurs when the limit of unconstrained diametral expansion of the PT 36 at the location of the annulus spacer 48 has been reached. The annulus spacers 48 may also remain in their design location so as to prevent PT 36 to CT 32 contact throughout the life of the fuel channel. In some embodiments, annulus spacer 48 axial positions may be verifiable during fuel channel inspections throughout the life of the reactor, so as to ensure that PT to CT contact will not occur before the end of the next inspection interval.

[0057] From a safety perspective, in some embodiments, the annulus spacer 48 may not result in unacceptable consequences that may affect reactor safeguards analysis. If required by the safety analysis, the annulus spacer 48 may allow contact of a PT 36 with the CT 32 surrounding it over a large enough area to permit a sufficient dissipation of heat for preventing fuel channel failure under a postulated event initiated by an accident condition such as a loss of coolant accident (LOCA). In the illustrated embodiment, the annulus spacer material does not interactwith the PT material at high temperature during transients so as to compromise the integrity of the PT 36. In some embodiments, the annulus spacers 48 may also not cause local stresses in the PT 36 that could initiate premature PT failure. During a severe fuel channel flow blockage event, the annulus spacer 48 may not significantly increase the amount of molten material that might be present in the affected channel. The annulus spacers 48 may allow relatively unimpeded annulus gas flow for leak before break detection purposes.

[0058] In some embodiments, the annulus spacer 48 withstands the fuel channel environmental conditions throughout its design life. As the annulus spacer 48 is located in the fuel channel annulus space 44, its temperature can be influenced by either the hot PT 36 (approximately 300°C) or the cooler CT 32 (approximately 80°C), depending on which component it is contacting. If the annulus spacer 48 is in contact with both tubes it will experience a temperature gradient between the temperatures of the PT 36 and the CT 32. The temperature of the annulus spacer 48 is further influenced by the contribution of gamma heating, although this effect should be small and is dependent on the spacer material selected. Nevertheless, the impact of nuclear heating, which comprises at lease one of neutron, alpha, beta, and gamma heating, on the environmental conditions may be assessed once a spacer material and design are selected.

[0059] The environment within the fuel channel annulus space 44 is primarily circulating carbon dioxide maintained at a low dew point, containing a small addition of oxygen. The annulus space 44 also experiences a relatively high fast neutron and thermal neutron flux. As there is a slow increase in the dew point of the annulus gas over time, the annulus gas system is periodically purged to maintain the sensitivity of its leak detection function. In the case of an abnormal operating occurrence or a Design Basis Accident (such as a fuel channel leak or pressure tube rupture), fuel channels other than the source channel may be exposed to extended periods of low temperature, moist annulus conditions. The annulus spacer 48 can be manufactured from materials that are stable under irradiation and are capable of withstanding the environmental conditions detailed above, such that any change in mechanical properties or geometries will not affect its integrity or location.

[0060] The annulus spacer 48 directly interfaces with the PT 36, the CT 32, and the gas of the annulus gas system. Thus, the annulus spacers 48 should be compatible with these components. The annulus spacers 48 may permit circulation of the annulus gas (comprised of CO2 and small additions of 02) along the fuel channel annulus 44. The annulus spacers 48 can allow the fuel channel annulus to be efficiently dried if water leaks into it. The annulus spacers 48 do not reduce the design life or affect the integrity of the PT 36 or the CT 32 under all normal operatingconditions. The annulus spacers 48 do not significantly interfere with the axial expansion of the PT 36, so as to affect the relative axial loading of the PT 36 or the CT 32. Annulus spacers 48 do not cause the formation of a stress riser on eitherthe PT 36 or CT 32 greaterthan the maximum allowable value determined by the lower bound value for K1 H- This is needed to demonstrate there is an adequate margin against delayed hydride cracking (DHC) initiation in either tube by the design loading conditions.

[0061] FIG. 3 is a more-detailed perspective of a prior art annulus spacer 48 installed within the annulus space 44 between the PT 36 and CT 32. Annulus spacer 48 is described in detail in U.S. Publication No. 20150213908A1 , the entire contents of which are hereby incorporated by reference. The annulus spacer 48 includes a garter spring 52 and a girdle wire 56. The garter spring 52 is formed from a length of coiled wire 60. Two ends 64 and 68 of the coiled wire 60 are connected so that the garter spring 52 forms a toroid 72. The garter spring 52 is dimensioned to fit tightly around the PT 36. The garter spring 52 is resilient so that it may be expanded to a dimension greater than an outside diameter 76 of the PT 32 during installation, yet fit tightly and securely once positioned. In the illustrated embodiment, the garter spring 52 is formed from a nickel-chromium based alloy such as INCONEL X-750. In other embodiments, the garter spring 52 may be formed of other alloys, including zirconium-based alloy such as ZIRCALOY or a zirconium-niobium-copper alloy. In still other embodiments, the garter spring 52 may be formed of an alloy including, but not limited to, a combination of zirconium, niobium, and copper.

[0062] The girdle wire 56 is held within an annular cavity 80 formed by the coiled wire 60 of the garter spring 52. The girdle wire 56 has two functions. First, the girdle wire 56 provides a fail-safe in the event that the garter spring 52 breaks. The girdle wire 56 will capture the separated garter spring 52. Second, in some embodiments the girdle wire 56 improves the ability to detect a position of the annulus spacer 48 using eddy current testing (ECT) techniques. Detecting the position of the annulus spacer 48 is necessary in orderto verify the location ofthe annulus spacer 48 in order to ensure that the annulus spacer 48 meets a variety of functional, performance, safety, environmental and inter-facing system requirements. The girdle wire 56 helps the annulus spacer 48 be detectable by providing a loop of continuous conductivity. In the illustrated embodiment, the girdle wire 56 is formed of a zirconium-based alloy such as ZIRCALOY. In other embodiments, the girdle wire 48 can be formed from a variety of other alloys.

[0063] In the illustrated prior art example shown in FIG. 3, an outer segment 84 of the girdle wire 56 overlaps upon an inner segment 88 of the girdle wire 56. An overlap 92 is provided in order to ensure that the girdle wire 56 forms a continuous loop or overlapping loop within the garterspring 52, in order to ensure that the garter spring 52 is captured in the event of failure. However, overlapping portions of the girdle wire 56 may oxidize or move relative to each other over time and during operation of the reactor, degrading the conductivity, and thereby detectability, of the annulus spacer 48. When corrosion occurs, electrical conductivity may be disrupted such that the gridle wire no longer provides continuous electrical circuit. Corrosion may also physically separate portions of the girdle wire such that it does not provide a unitary loop. As such, annulus spacers including girdle wires with overlaps may include garter springs that are welded into a continuous loop (as shown in FIGS. 8A-8D) to facilitate detection. In other embodiments, ends of the girdle wire 56 may be welded together with substantially no overlap. The conductivity, and thereby detectability, of girdle wires with welded ends typically does not degrade over time or during operation of the reactor. Various types of connectors to connect ends of garter springs (such as those shown in FIGS. 9A-15C) may therefore be employed in annulus spacers having welded girdle wires. In some embodiments, ends of the girdle wire 56 may be both overlapped and welded together. Additionally or alternatively, in some embodiments, both the girdle wire 56 and the garter spring 52 may include ends that are welded together. Prior art girdle wire 56 alleviates a problem known in the nuclear industry as garter spring hang-up. During installation over the PT 36, an overlap 92 of 180 degrees or more could allow the girdle wire 56 to twist upon itself. A twisted girdle wire 56 may, in turn, prevent the garter spring 52 from compressing about the PT 36 when installed. If the garter spring 52 is blocked from compressing due to a twisted girdle wire 56, the functional and performance requirements of the annulus spacer 48 may not be met. In particular, a hung-up garter spring 52 may result in the annulus spacer48 shifting between inspections and overhauls to the point where PT 36 to CT 32 contact could occur. A hang-up may also result in an annulus spacer installation tool jamming or failing. The prior art annulus spacer 48 is illustrated in FIG. 3 which includes features designed to prevent girdle wire twisting. First, the overlap 92 of the girdle wire 56 has been dimensioned in order to minimize the risk of girdle wire twisting. In other words, overlap 92 is long enough to ensure that at least 360 degrees of continuous girdle wire 56 is provided within the coils 60 of the garter spring 52. However, the overlap 92 of the girdle wire 56 of a given configuration is short enough to ensure that the girdle wire 56 is unlikely to twist upon itself. In other words, overlap 92 of the girdle wire 56 remains substantially co-planar with non-overlapping portion of the girdle wire 56 during installation and operation. In the illustrated embodiment, it the girdle wire overlaps of between approximately 1 degree and approximately 179 degrees to minimize the risk of the girdle wire twisting upon itself.

[0064] FIGs. 4A and 4B illustrate an example of annulus spacer lock-up where the girdle wire pinches a garter spring against a pressure tube. During operation, pressure tube 36 may expand longitudinally and / or diametrically at a greater rate relative to calandria tube 32. As a result, annulus spacer lock-up may occur as girdle wire 56 forces garter spring 52 against PT 36 such that the annulus spacer 48 is pinned against PT36 and cannot roll. Annulus spacer lock-up may occur in prior art annulus spacer 48 describe above with respect to FIG. 3. As shown in FIG. 4A, as PT 36 expands, the outer diameter 52d of garter spring 52 may contact CT32 and the resulting net force acting on girdle wire 56 forces it toward PT 36 pinching garter spring 52 against PT 36 at point P. In the illustration, Ncis the normal force exerted between the calandria tube surface and the coil spring; FFC is the frictional force between the calandria tube and the coil spring; Npis the normal force exerted between the pressure tube surface and the coil spring; FFP is the friction force between the pressure tube and the coil spring; Ngwis the normal force exerted between the annulus spacer surface and the girdle wire; and FGW is the friction force between the annulus spacer and the girdle wire. FIG. 4B shows annulus 48 in lock-up against PT 36.

[0065] In an aspect, annulus spacers according to this disclosure may prevent annulus spacer lock-up. FIGs. 5-12B illustrate example annulus spacers configured to prevent annulus spacer lock-up. In another aspect, annulus spacer’s according to this disclosure may be configured to prolong electrical conductivity of the girdle wire as a continuous electrical circuit during operation of the nuclear reactor in which the annulus spacer is installed. Maintaining electrical conductivity may allow the annulus spacer to be more easily detected by establish eddy current testing methods for a longer duration than annulus spacer 48 described above with respect to FIG. 3.

[0066] FIGs 5A-5C illustrate an plane view of an annulus spacer according to this disclosure. As shown in FIGs. 5A and 5B, girdle wires 500A, 500B for an annulus spacer of a fuel channel assembly of a nuclear reactor. Girdle wires 500A, 500B comprises an expansion mechanism 501 . Girdle wire 500A, 500B forms a loop around a pressure tube, e.g. PT 36, where girdle wire 500A, 500B has a first end 502 and a second end 503. As shown, first end 502 and second end 503 may be fixedly coupled end-to-end to form unitary loop. Girdle wire 500A, 500B defines a first circumference 504 when the expansion mechanism 501 is in a first configuration, e.g. when initially installed on the pressure tube, and a second circumference 502 when the expansion mechanism 501 is in a second configuration, e.g. after the pressure tube diametrically expands. Girdle wire 500A, 500B transitions from the first configuration to the second configuration during diametral expansion of the pressure tube. Expansion mechanism 501 maintains first end 502 and second end 503 in electrical communication in both the first and second configurations formaintaining the loop of girdle wire 500A, 500B as a continuous electrical circuit. Similar to FIG. 3, a garter spring 52 defines the girdle wire 500A, 500B within garter spring 52 where the garter spring is configured to surround a portion of the pressure tube to maintain a gap between the calandria tube and the pressure tube.

[0067] In the embodiments shown in FIG. 5A and 5B, expansion mechanism 501 comprises a plurality of kinks 506 defining wave-shaped pattern in the general shape of a circle. As shown in FIG. 5C, the enlarged fragmentary view of the plurality of kinks 506 define a first angle 0 between adjacent kinks in the first configuration and a second angle 0’ between adjacent kinds in the second configuration, the second angle 0’ greater than the first angle 0. In the example shown in FIG. 5A, first angle 0 between adjacent kinks in the first configuration is about 140-150°. In the example shown in FIG. 5B, first angle 0 between adjacent kinks in the first configuration is about 120-130°. Angle p represents the degrees of the loop defined by kinks 506. In some embodiments, the plurality of kinks 506 may define at least 270 degrees of the loop of the girdle wire. In some embodiments, the plurality of kinks 506 may define the entire loop of the girdle wire.

[0068] FIGs. 6A-6C illustrates another embodiment of a girdle wire for an annulus spacer according to this disclosure. As shown in FIG. 6A, girdle wire 600 is defined within garter spring 52 which is configured to surround a portion of the pressure tube to maintain a gap between the calandria tube and the pressure tube. The girdle wire 600 is held within an annular cavity 80 formed by the coiled wire 60 of the garter spring 52. An overlap 692 is provided in order to ensure that the girdle wire 600 forms a continuous loop or overlapping loop within the garter spring 52, in order to ensure that the garter spring 52 is captured in the event of failure. However, overlapping portions of the girdle wire 600 may oxidize or move relative to each other over time and during operation of the reactor, degrading the conductivity, and thereby detectability, of the annulus spacer 648. Girdle wire 600 may comprise expansion mechanism 601 . Girdle wire 600 forms a loop around the pressure tube when installed and has a first end 602 and a second end 603 defining overlap 692. Girdle wire 600 defines a first circumference when the expansion mechanism is in a first configuration, e.g. when initially installed on the pressure tube, as shown in FIG. 6A and a second circumference when the expansion mechanism is in a second configuration, e.g. when the pressure tube diametrically expands. Girdle wire 600 may be a unitary loop in the first configuration. In an example, portions of girdle wire 600 defining overlap 692 may be coupled together, e.g, by braising or welding, such that the overlaped portion of girdle wire 600 cannot move relative to each other up to a threshold force or desired time period. Asshown in FIG. 6C, expansion mechanism 601 is a notched portion 606 proximate to the first end which is secured to secured to the girdle wire. The notched portion 606 configured to break during diametral expansion of the pressure tube as girdle wire 600 transitions from the first configuration to the second configuration. In an example, notched portion 606 may be configured to break after a desired time period or force is applied by the diametric expansion of the pressure tube. In an example, the time period may be an estimated time period when corrosion of the overlapped portion reduces conductivity of the girdle wire. When the notched portion 606 breaks, the girdle wire does not form a unitary loop. In other words, when the notched portion 606 breaks, the portions of the girdle wire which were previously coupled by fixed connection may move relative to each otherwhile maintaining electrical communication. In an example, the portions of the girdle wire which were previously coupled by fixed connection may remain in contact while moving relative to each other. As the girdle wire 600 transitions from the first configuration to the second configuration during diametral expansion of the pressure tube, expansion mechanism 601 maintains first end 602 and second end 603 in electrical communication in both the first and second configurations for maintaining the loop of girdle wire 600 as a continuous electrical circuit.

[0069] In an embodiment, ends of the garter spring 52 may be welded together. These welds may provide electrical connectivity of the garter spring itself leading to detection and movement options. Annulus spacers according to this disclosure, may include garter spring 52 and any girdle wire described herein. In the embodiment illustrated in FIG. 6A, the garter spring 52 may includes two end portions 612, 616 that are turned into each other and welded together so that the garter spring 52 forms a toroid. In some embodiments, the two end portions 612, 616 may be welded at a single location by, for example, a single spot weld 620 (FIG. 6A). In another embodiment, the two end portions 612, 616 may be welded at locations spaced approximately 180 degrees from each other around the coil circumference by, for example, two spot welds 624. Such embodiments may increase the strength and redundancy of the connection while maintaining the flexibility required to enable free rolling of the annulus spacers according to this disclosure between the pressure tube and the calandria tube. In still other embodiments, the end portions 612, 616 may be welded at a plurality of locations by, for example, a plurality of spot welds spaced around the circumference of the garter spring 52. Providing a plurality of welds may allow some of the welds to have reduced load, or be non-load bearing to keep weld load down and reduce the potential of the welds cracking and breaking as the material embrittles with radiation damage over their lifecycles. In some embodiments, a connector, connecting joint, or sleeve joint 650, described in U.S. Patent Publication No. 20150213908A1 , the entire contents ofwhich are hereby incorporated by reference, may be used to couple ends of garter spring 52 together to unload welds 620, 624 as shown in FIG. 6D. As shown, sleeve joint 650 may define an opening 651 through which girdle wire 56 may pass through. By unloading the weld(s) of the garter spring, the weld(s) may maintain their integrity and last longer than a similar loaded weld.

[0070] In another embodiment, girdle wire 600 may forms a loop around the pressure tube when installed and has a first end 602 and a second end 603 defining overlap 692. In the embodiment, at least one of first end 602 and second end 603 may be coupled to garter spring 52, e.g. by welding or brazing. Example welds are shows as 602W, 603W. In an example, as the pressure tube diametrically expands first end 602 and second end 603 may move toward each other pulling a portion of garter spring 52 to expand. By coupling at least one of first end 602 and second end 603 to the garter spring 52 the garter spring may be used to complete the continuous electrical circuit in the event that the girdle wire portions of overlap 692 stop touching.

[0071] FIGs. 7A, 7B illustrates another embodiment of a girdle wire for an annulus spacer according to this disclosure. Like the embodiments described above, girdle wire 700 is configured to be defined within garter spring 52 which is configured to surround a portion of the pressure tube to maintain a gap between the calandria tube and the pressure tube. Girdle wire 700 is held within an annular cavity 80 formed by the coiled wire 60 of the garter spring 52. Unlike some embodiments, there is no overlapping portion of the girdle wire 700; rather, a sleeve 706 is provided in order to ensure that the girdle wire 700 forms a continuous loop and unitary loop within the garter spring 52 to ensure that the garter spring 52 is captured in the event of failure. As shown, sleeve 706 may be positioned at first end 702 and receive second end 703 to form the loop. Sleeve 706 act as a connector which couples both ends of the girdle wire 700. In an embodiment, second end 703 is slidably received within sleeve 706 such that second end 703 may retract and / or advance within the sleeve 706. In an example, second end 703 may retract within sleeve 706 when girdle wire 700 transitions from it first configuration, e.g. an installed preoperation configuration, to its second configuration, e.g. an expanded configuration when the pressure tube diametrically expands.

[0072] Because there are no overlapping portions of the girdle wire 700 oxidization may be reduced relative to designs where there are overlapping portions of girdle wire. Reduced oxidization of girdle wire 700 maintains conductivity, and thereby detectability, of the annulus spacer 648. Girdle wire 700 may comprise expansion mechanism 701. As shown, girdle wire 700 forms a loop around the pressure tube when installed and has a first end 702 and a second end 703. Girdle wire 700 defines a first circumference when the expansion mechanism 701 is ina first configuration, e.g. when initially installed on the pressure tube, as shown in FIG. 7A and a second circumference when the expansion mechanism 701 is in a second configuration, e.g. when the pressure tube diametrically expands. FIG. 7B illustrates girdle wire 700 transitioning to the second circumference as second end 703 retracts through sleeve 706 in direction 706a (illustrated by an arrow) enlarging the circumference of girdle wire 700. As girdle wire 700 transitions from the first configuration to the second configuration during diametral expansion of the pressure tube, expansion mechanism 701 maintains first end 602 and second end 603 in electrical communication in both the first and second configurations for maintaining the loop of girdle wire 700 as a continuous electrical circuit.

[0073] FIGs. 8A-8B illustrates another embodiment of a girdle wire for an annulus spacer according to this disclosure. As described above, girdle wire 800 is defined within a garter spring, e.g. garter spring 52 which is configured to surround a portion of the pressure tube to maintain a gap between the calandria tube and the pressure tube. The girdle wire 800 is held within an annular cavity 80 formed by the coiled wire 60 of the garter spring 52. An overlap 892 is provided in order to ensure that the girdle wire 800 forms a continuous loop or overlapping loop within the garter spring 52, in order to ensure that the garter spring 52 is captured in the event of failure. However, overlapping portions of the girdle wire 800 may oxidize or move relative to each other over time and during operation of the reactor, degrading the conductivity, and thereby detectability, of the annulus spacer 648. Girdle wire 800 may comprise expansion mechanism 801 . Girdle wire 800 forms a loop around the pressure tube when installed and has a first end 802 and a second end 803 defining overlap 692. Girdle wire 800 defines a first circumference when the expansion mechanism is in a first configuration, e.g. when initially installed on the pressure tube, as shown in FIG. 8A and a second circumference when the expansion mechanism is in a second configuration, e.g. when the pressure tube diametrically expands. Girdle wire 800 may be a unitary loop in the first configuration. In an example, portions of girdle wire 800 defining overlap 692 may be coupled together, e.g, by braising or welding. As shown in FIG. 8B, expansion mechanism 801 comprises a flexible portion 806 configured to straighten and lengthen when the girdle wire transitions from the first configuration to the second configuration during diametral expansion of the pressure tube. In an embodiment, the girdle wire is configured to both elastically lengthen and the expansion mechanism is configured to uncoil during transition from the first configuration to the second configuration to increase the first circumference to the second circumference. In an example, flexible portion 806 is coiled around another portion of the girdle wire and straightening causes the coiled portion to at least partially uncoil increasing the lengthof the girdle wire and circumference of the girdle wire. In an embodiment, flexible portion 806 is proximate first end 802. In an example, first end 802 is coupled to girdle wire, e.g. by welding or braising to form a connector fixing the first end 802 to the girdle wire. As shown in exemplary FIGs. 8A, 8B, flexible portion 806 is a coiled wire. In other embodiments, flexible portion 806 may be a braided and / or curved wire. As the girdle wire 800 transitions from the first configuration to the second configuration during diametral expansion of the pressure tube, expansion mechanism 801 maintains first end 802 and second end 803 in electrical communication in both the first and second configurations for maintaining the loop of girdle wire 800 as a continuous electrical circuit. In an embodiment, flexible portion 806 comprises between about 10-270 degrees of the loop.

[0074] FIGs. 9A illustrates another embodiment of a girdle wire for an annulus spacer according to this disclosure. As described above, girdle wire 900 is defined within a garter spring, e.g. garter spring 52, which is configured to surround a portion of the pressure tube to maintain a gap between the calandria tube and the pressure tube. Girdle wire 900 is held within an annular cavity 80 formed by the coiled wire 60 of the garter spring 52. An overlap 992 is provided in order to ensure that the girdle wire 900 forms a continuous loop or overlapping loop within the garter spring 52, in order to ensure that the garter spring 52 is captured in the event of failure. However, overlapping portions of the girdle wire 900 may oxidize or move relative to each other over time and during operation of the reactor, degrading the conductivity, and thereby detectability, of the annulus spacer 648. Girdle wire 900 may comprise expansion mechanism 901 . Girdle wire 900 forms a loop around the pressure tube when installed and has a first end 902 and a second end 903 defining overlap 992. Girdle wire 900 defines a first circumference when the expansion mechanism is in a first configuration, e.g. when initially installed on the pressure tube, as shown in FIG. 9A and a second circumference when the expansion mechanism is in a second configuration, e.g. when the pressure tube diametrically expands. Girdle wire 900 may be a unitary loop in the first configuration. In an example, portions of girdle wire 900 defining overlap 992 may be coupled together, e.g. by braising or welding forming a connector. FIG. 9B shows an enlarged fragmentary view of expansion mechanism 901 along line A-A of FIG. 9A. As shown in FIG. 9B, expansion mechanism 901 comprises a flexible portion 906 configured to straighten and lengthen when the girdle wire transitions from the first configuration to the second configuration during diametral expansion of the pressure tube. In an embodiment, flexible portion 906 is proximate first end 902. In an example, first end 902 is coupled to girdle wire, e.g. by welding or braising. As shown in exemplary FIGs. 9A, 9B, flexible portion 906 is a wave wire made of flexible material configured to straighten and lengthen as pressure tube diametrically expands. As thegirdle wire 900 transitions from the first configuration to the second configuration during diametral expansion of the pressure tube, expansion mechanism 901 maintains first end 902 and second end 903 in electrical communication in both the first and second configurations for maintaining the loop of girdle wire 800 as a continuous electrical circuit. In an embodiment, flexible portion 906 comprises between about 10-270 degrees of the loop. As shown, the embodiments of FIGs. 9A and 9B form a unitary loop in both the first and second configurations.

[0075] FIG. 10A illustrates an example connector of detail B in FIG. 9A, and FIG. 10B illustrates a cross-sectional view of the example connector of FIG. 10A. Connector 1000 may comprise a tubularsleeve 1001 for coupling ends of girdle wire together orfor coupling expansion mechanism 901 to another portion of girdle wire 800, 900. Connector 1000 defines a lumen for receiving expansion mechanism 901 and / or another portion of girdle wire 800, 900. As shown, an end portion of expansion mechanism 901 and girdle wire 800, 900 may be positioned end-to-end within the inner diameter of connector 1000. One of the expansion mechanism 901 or the girdle wire 800, 900 may comprise braided wire that may be brazed to the other of the expansion mechanism 901 or the girdle wire 800, 900 and connector 1000. Braided wire may provide has higher durability and flexibility in comparison solid wire traditionally use for girdle wires.

[0076] FIG. 10C illustrates an example connector of detail C in FIG. 9A. As shown, expansion mechanism 901 and girdle wire 800, 900 may be positioned to form an overlap 1002 between the end portion. One of the expansion mechanism 801 , 901 orthe girdle wire 800, 900 may comprise braided wire that may be brazed or welded to the other of the expansion mechanism 801 , 901 or the girdle wire 800, 900 at the overlap 1002.

[0077] FIG. 11 A illustrates another embodiment of a girdle wire for an annulus spacer according to this disclosure. As described above, girdle wire 1100 is defined within a garter spring, e.g. garter spring 52, which is configured to surround a portion of the pressure tube to maintain a gap between the calandria tube and the pressure tube. Girdle wire 1100 is held within an annular cavity 80 formed by the coiled wire 60 of the garter spring 52. Girdle wire 1100 forms a loop around the pressure tube when installed and comprises an expansion mechanism 1101 . Girdle wire 1 100 defines a first circumference when the expansion mechanism is in a first configuration, e.g. when initially installed on the pressure tube, and a second circumference when the expansion mechanism is in a second configuration, e.g. when the pressure tube diametrically expands. Girdle wire 1100 may be a unitary loop in both the first and second configurations. In an example, portions of girdle wire 1 100, i.e. expansion mechanism 1101 and the remainder of girdle wire 1 100 may be coupled together, e.g. by braising or welding. FIG. 11 B shows an enlargedfragmentary cutaway view of a connection between expansion mechanism 1 101 and another portion of girdle wire 1 100 shown in FIG. 1 1 A. As shown in FIG. 11 B, expansion mechanism 1 101 comprises a braided portion 1106 made of flexible braided wire configured to lengthen when the girdle wire transitions from the first configuration to the second configuration during diametral expansion of the pressure tube. In an embodiment, braided portion 1106 comprises between about 10-270 degrees of the loop. In another embodiment, braided portion 1106 may comprise about 270 degrees of the loop. Expansion mechanism 1 101 may be coupled to another part 1003 of girdle wire 1 100 by welding or braising within a connector 1000 described above. As the girdle wire 1 100 transitions from the first configuration to the second configuration during diametral expansion of the pressure tube, expansion mechanism 1101 maintains first end 902 and second end 903 of girdle wire 1100 in electrical communication in both the first and second configurations for maintaining the loop of girdle wire 800 as a continuous electrical circuit, i.e. a unitary loop.

[0078] FIGs. 12A and 12B illustrates another embodiment of a girdle wire for an annulus spacer according to this disclosure. As described above, FIG. 12A shows girdle wire 1200 defined within a garter spring, e.g. garter spring 52, which is configured to surround a portion of the pressure tube to maintain a gap between the calandria tube and the pressure tube. FIG. 12B shows a cut away view of FIG. 12 illustrating girdle wire 1200 held within an annular cavity 80 formed by the coiled wire 60 of the garter spring 52. Girdle wire 1200 may comprise the features of any one of girdle wires 500A, 500B, 600, 700, 800, 900, 1100 according to this disclosure. Girdle wire 1200 may comprise first end 1202 and second end 1203 of girdle wire 1100 which are coupled to expansion member 1201 , e.g. by welding and / or brazing. As shown, expansion mechanism 1201 may be biasing member 1206, such as a spring, which may expand as the pressure tube diametrically expands. In an example, ends 1202, 1203 may be each be welded or brazed to one of opposing ends 1204, 1205 of expansion mechanism 1201. In an embodiment, a plurality of spot welds may couple end portions of girdle wire 1200 to expansion mechanism 1201. For example, illustrative welds 1204W and 1205W are shown in FIG. 12B. Girdle wire 1200 defines a first circumference when the expansion mechanism is in a first configuration, e.g. when initially installed on the pressure tube, and a second circumference when the expansion mechanism 1201 is in a second configuration, e.g. when the pressure tube diametrically expands. Girdle wire 1200 and expansion mechanism 1201 maintain conductivity of the girdle wire as a continuous electric circuit as a loop around the pressure tube in both the first and second configurations. As shown, girdle wire 1200 is a unitary loop in both the first and second configurations.

[0079] Oxidation of girdle wires reduces conductivity of the material forming the closed loop of the girdle wire which in turn reduces or eliminates the detectability of the girdle wire an annulus spacer. In some aspect, the embodiment of FIGs. 5A-12B may mitigate against oxidation to maintain conductivity of the girdle wire as a continuous electric circuit. However, material selection made also reduce oxidation of girdle wire. In an aspect, girdle wires, including girdle wires according to this disclosure may comprise a coating layer. The coating may comprise at least one of zirconium nitrite (ZrN), titanium nitride (TiN), nickel, chromium, rhenium, ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold. This metal coating may reduce oxidation during and prolong the time the girdle wires may be detectable, e.g. by eddy current testing, during operation of the nuclear reactor.

[0080] Oxidation of girdle wires may also be reduced by making the girdle wires of oxidation resistant material. In an embodiment, girdle wires according to this disclosure may comprise at least one of stainless steel, nickel alloy, copper alloy, zirconium alloy, and aluminum bronze. In an example, the girdle wires may be ferromagnetic, e.g. by selecting ferromagnetic alloys of stainless steel, nickel alloy, copper alloy, zirconium alloy, and / or aluminum bronze. Utilization of ferromagnetic alloys may promote detectability of the girdle wire by eddy current testing and / or its locating and repositioning by a Spacer Locating and Repositioning (SLAR) Tool. These girdle wires materials may be used in combination with the coatings described above and / orthe annulus spacers described with reference to FIGs. 5A-12B. For similar reasons noted above, garter spring 52 according to this disclosure may comprise stainless steel, nickel alloy, copper alloy, zirconium alloy, and / or aluminum bronze. In an example, the garter spring(s) according to this disclosure may comprise ferromagnetic material, e.g. by selecting ferromagnetic alloys of stainless steel, nickel alloy, copper alloy, zirconium alloy, and / or aluminum bronze.

[0081] FIG. 13 is schematic diagram illustrating an example method 1300 of detecting a position of an annulus spacer between a calandria tube and a pressure tube of a nuclear reactor. In an example, method 1300 may utilize any one of the annulus spacers comprising the girdle wires described above with reference to FIGs. 5A-12B.

[0082] At 1302, method 1300 comprises providing an annulus spacer according to this disclosure.

[0083] At 1304, the annulus spacer is positioned around a pressure tube in the first configuration. When in its initial position, the annulus spacer is positioned between the pressure tube and the calandria tube in its non-expanded configuration.

[0084] At 1306, the location of the annulus spacer is detected by eddy current testing when the expansion mechanism is in the second configuration. In an embodiment the location of the annulus spacer may also be detected when expansion mechanism is in the first configuration.

[0085] In an embodiment, the girdle wire elastically lengthens and the expansion mechanism uncoils during transitioning from the first configuration to the second configuration to increase the first circumference to the second circumference.

[0086] FIG. 14 is schematic diagram illustrating an example method 1400 of locating and repositioning an annulus spacer between a calandria tube and a pressure tube of a nuclear reactor. In an example, method 1400 may utilize any one of the annulus spacers comprising the girdle wires described above with reference to FIGs. 5A-12B.

[0087] At 1402, the method comprises providing an annulus spacer according to this disclosure around a pressure tube of a nuclear reactor in a first configuration.

[0088] At 1404, the annulus spacer may be initially at a first position along a length of the pressure tube between the pressure tube and the calandria tube.

[0089] At 1406, a magnetic field may be created and applied to the annulus spacer. In an embodiment, the magnetic field is created with a Spacer Locating and Repositioning (SLAR) tool. The annulus spacer may be in the first or second configuration when the magnetic field is applied to the annulus spacer. An example SLAR tool, and method of using same, is described in Cenanovic, Matija et al. “The AC Device for Repositioning of Garter Springs in CANDU Reactors” Nuclear Journal of Canada, 1 :4, pages 355-358, Ontario Hydro, online:<https: / / ca nteach.candu.org / Content%20Librarv / NJC-1 -4-09. pdf> (accessed June 14, 2024) the entire contents of which are hereby incorporated by reference.

[0090] At 1408, the annulus spacer may be moved to second position along the length of the pressure tube with the magnetic field. The magnetic field may a magnetic force to reposition the annulus spacer to the second position.

[0091] Alternate embodiments

[0092] The above description is meant to be exemplary only, and one skilled in the relevant arts will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. The present disclosure may be embodied in other specific forms without departing from the subject matter of the claims. The present disclosure is intended to cover and embrace all suitable changes in technology. Modifications which fall within the scopeof the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims. Also, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

[0093] As can be understood, the detailed embodiments described above and illustrated are intended to be examples only. The invention is defined by the appended claims.

[0094] The claims are not intended to include, and should not be interpreted to include, means- plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) “means for” or “step for,” respectively.

Claims

CLAIMSWhat is claimed is:1 . An annulus spacer for a fuel channel assembly of a nuclear reactor, the fuel channel assembly comprising a calandria tube and a pressure tube positioned at least partially within the calandria tube, the annulus spacer comprising: a girdle wire comprising an expansion mechanism, the girdle wire forming a loop around the pressure tube, the girdle wire having a first end and a second end, the girdle wire defining a first circumference when the expansion mechanism is in a first configuration and a second circumference when the expansion mechanism is in a second configuration, the girdle wire transitioning from the first configuration to the second configuration during diametral expansion of the pressure tube, the expansion mechanism maintaining first end and the second end in electrical communication in both the first and second configurations for maintaining the loop of the girdle wire as a continuous electrical circuit; and a garter spring defining the girdle wire within the garter spring, the garter spring configured to surround a portion of the pressure tube to maintain a gap between the calandria tube and the pressure tube.

2. The annulus spacer of claim 1 , wherein the girdle wire forms a unitary loop in the first configuration.

3. The annulus spacer of any one of claims 1-2, wherein the expansion mechanism comprises a notched portion proximate to the first end which is secured to secured to the girdle wire, the notched portion configured to break during diametral expansion of the pressure tube as the girdle wire transitions from the first configuration to the second configuration, wherein the girdle wire does not form a unitary loop when the notched portion breaks.

4. The annulus spacer of claim 1 , wherein the expansion mechanism comprises a sleeve receiving the second end to form the loop.

5. The annulus spacer of claim 4 wherein the second end is slidably received within the sleeve, the second end retracting within the sleeve when the girdle wire transitions from the first configuration to the second configuration.

6. The annulus spacer of claim 1 , wherein the expansion mechanism comprises a flexible portion configured to straighten when the girdle wire transitions from the first configuration to the second configuration during diametral expansion of the pressure tube.

7. The annulus spacer of claim 6, wherein the flexible portion is proximate the first end, and wherein the first end is coupled to girdle wire.

8. The annulus spacer of claim 6 or 7 wherein the flexible portion is a braided wire, coil, or curved wire.

9. The annulus spacer of any one of claims 6-8, wherein the flexible portion is welded or brazed to a connector.

10. The annulus spacer of any one of claims 6-9, the first end is welded or brazed to a portion of the girdle wire.1 1 . The annulus spacer of claim 10, wherein the first end is welded or brazed to the second end.

12. The annulus spacer of any one of claims 6-10, wherein the braided wire portion comprises between about 10-270 degrees of the loop.

13. The annulus spacer of claim 12 wherein the braided wire portion comprises about 270 degrees of the loop.

14. The annulus spacer of claim 1 , wherein the expansion mechanism comprises a plurality of kinks defining wave-shaped pattern, the plurality of kinks defining a first angle between adjacent kinks in the first configuration and a second angle between adjacent kinds in the second configuration, the second angle greater than the first angle.

15. The annulus space of claim 14, wherein the plurality of kinks defined at least 270 degrees of the loop.

16. The annulus spacer of claim 1 , wherein the expansion mechanism comprises a spring, wherein the first end of the girdle wire is coupled to one end of the spring of the expansion mechanism and the second end of the girdle wire is coupled to a second end of the expansion mechanism.

17. The annulus spacer of any one of claims 1-16, wherein the girdle wire comprises a coating, the coating comprising at least one of zirconium nitrite (ZrN), titanium nitride (TiN), nickel, chromium, rhenium, ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold.

18. The annulus spacer of any one of claims 1-17, wherein the girdle wire comprises stainless steel, nickel alloy, copper alloy, zirconium alloy, and aluminum bronze.

19. The annulus spacer of any one of claims 1-18, wherein the garter spring comprises stainless steel, nickel alloy, copper alloy, zirconium alloy, and aluminum bronze.

20. The annulus spacer of any one of claims 1-19, wherein at least one of the girdle wire and garter spring are ferromagnetic.

21. The annulus spacer of any one of claims 1 -20, wherein the girdle wire is configured to both elastically lengthen and the expansion mechanism is configured to uncoil during transition from the first configuration to the second configuration to increase the first circumference to the second circumference.

22. The annulus spacer of any one of claims 1 -21 , wherein opposing ends portions of the garter spring are coupled by a structural weld, and wherein the garter spring comprises non- structural welds coupling a first and second portion of the garter spring for maintaining electrical conductivity between the first and second portion.

23. The annulus spacer of any one of claims 1-21 , comprising a connector, connecting joint, or sleeve joint to couple opposing end portions ofthe garter spring, wherein opposing end portions are coupled by at least one non-structural weld, wherein the connector, connecting joint, or sleeve joint unloads the least one non-structural weld.

24. A method of detecting a position of an annulus spacer between a calandria tube and a pressure tube of a nuclear reactor, the method comprising: positioning the annulus spacer of any one of claims 1-23 around a pressure tube in the first configuration, the annulus spacer positioned between the pressure tube and the calandria tube; and detecting a location of the annulus spacer by eddy current testing when the expansion mechanism is in the second configuration.

25. The method of claim 24, comprising determining the location of the annulus spacer when expansion mechanism is in the first configuration.

26. The method of any one of claims 24-25, wherein the girdle wire elastically lengthens and the expansion mechanism uncoils during transitioning from the first configuration to the second configuration to increase the first circumference to the second circumference.

27. A method of locating and repositioning an annulus spacer between a calandria tube and a pressure tube of a nuclear reactor, the method comprising: providing the annulus spacer of any one of claims 1-23 around a pressure tube at a first position along the length of the pressure tube, the annulus spacer positioned between the pressure tube and the calandria tube; and applying a magnetic field to the annulus spacer and moving the annulus spacer to a second position along the length of the pressure tube with the magnetic field.

28. The method of claim 27, wherein the magnetic field is created with a Spacer Locating and Repositioning (SLAR) tool.

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