Identification gas capsules with a heat-based emission system

Abstract

An identification gas capsule utilizes a heat-based release system to allow the identification gas to flow through the fuel pin and to detect leakage within the fuel pin. An identification gas capsule equipped with an escape passage for the identification gas is fabricated, and the escape passage is sealed by a heat-sensitive material. During fabrication, the heat-sensitive material is melted into the identification gas capsule and seals the flow hole within the identification gas capsule. The capsule is then filled with identification gas and sealed to prevent the escape of the identification gas. Once the capsule is installed within the fuel pin, the capsule can be heated to melt the heat-sensitive material and expose the flow hole. The identification gas can then flow out of the flow hole and into the fuel pin.

Description

Technology Field

[0001] Government license authority

[0002] The present invention was made with government support pursuant to DOE Cooperation Agreement DE-NE0009054 granted by the U.S. Department of Energy. The government holds specific rights in the present invention.

[0003] References

[0004] This application claims the benefit of priority to U.S. provisional patent application No. 63 / 621,097, filed January 15, 2024, titled “Identification gas capsule having a heat-based emission system,” the entire contents of which are incorporated herein by reference.

[0005] Field of the present disclosure

[0006] The present disclosure relates to an identification gas capsule for detecting leaks within nuclear fuel pins, which provides simple fabrication, installation, and operation. Background Technology

[0007] Identification gases are utilized within fuel pins as components of safety and monitoring systems within a nuclear reactor. Fuel pins contain fissile material, typically enriched uranium, plutonium, or thorium, which undergoes a fission reaction to generate heat for power production. Identification gases, such as helium or xenon, are introduced into the fuel pins during the manufacturing process. These gases serve as tracers or indicators that can be monitored to assess the integrity of the fuel pins over time.

[0008] Fuel pin leaks are a concern in nuclear reactors because they can compromise the containment of radioactive materials and pose safety hazards. Rapid detection of leaks is essential to ensure the safe operation of the reactor. Identification gases play a critical role in leak detection because they are selected for their inert nature and low reactivity with other materials. In the event of a fuel pin rupture or leak, identification gases are released, and their presence can be monitored using sensitive detectors. The concentration and isotopic composition of these identification gases provide valuable information regarding the location and severity of the leak.

[0009] The process of identifying gas leak detection involves the periodic sampling and analysis of reactor coolant or gas from the containment system. Specialized monitoring systems are employed to detect the presence of identifying gases and to quantify their concentrations. The use of identifying gases in leak detection enhances the reliability of safety measures in the reactor, enabling operators to identify potential problems and resolve them before they become severe. This proactive approach to monitoring ensures the continuous, safe, and efficient operation of nuclear power plants, contributing to the overall stability and security of nuclear energy as a viable power source.

[0010] Historically, identification gas capsules used for leak detection rely on moving parts, such as needles that move by magnetic force to puncture the capsule containing the identification gas. Once the needle punctures the identification gas capsule, the identification gas is released into the fuel fins, allowing it to escape in the event of a fuel fin leak. The moving parts cause the identification gas capsule to require a length to accommodate the movement of the needle, which impacts the entire plenum volume of the fuel fin assembly and leads to a tall core assembly. Furthermore, the capsule must be manufactured, transported, handled, and installed carefully to prevent unintended puncture of the capsule. The problem to be solved

[0011] It would be advantageous if the identification gas capsule were smaller than historical capsules, more efficient to manufacture, did not contain moving parts, and was not susceptible to rupture during manufacturing, transportation, handling, and installation procedures. These and other advantages will be readily apparent to those skilled in the art by reference to the following description and attached drawings. means of solving the problem

[0012] An identification gas capsule comprises: a capsule tube having a first end and a second end; a first end cap coupled to the capsule tube and sealing the first end of the capsule tube; a second end cap coupled to the capsule tube and sealing the second end of the capsule tube; a flow hole formed in one or more of the capsule tube, the first end cap, and the second end cap; an identification gas disposed inside the capsule tube; and a thermally sensitive material disposed inside the identification gas capsule to block the flow hole, the thermally sensitive material configured to melt at a temperature below the reactor operating temperature to expose the flow hole and allow the identification gas to escape through the flow hole.

[0013] The heat-sensitive material may be sodium, tin, or other required material that can be melted at an appropriate temperature and is compatible with the environment and materials in which the heat-sensitive material is used.

[0014] In some cases, the flow holes are small to reduce the cross-section of the exposed heat-sensitive material, and in some cases, have a diameter of 0.8 mm, or 1 mm, or 1.2 mm, or 1.5 mm or more.

[0015] The identification gas capsule can be configured to be inserted into the nuclear fuel pin, and in some cases, has an outer diameter of less than 6.35 mm.

[0016] In some embodiments, a flow hole is formed at a location near the upper end of the identification gas capsule so that the heat-sensitive material flows downward and is trapped inside the identification gas capsule once it is melted. In this way, the heat-sensitive material is retained inside the identification gas capsule even after it has melted.

[0017] In some examples, a flow hole is formed at the bottom end of the identification gas capsule so that the heat-sensitive material flows out of the identification gas capsule once it has melted. In this case, the heat-sensitive material may flow into the fuel fin and be trapped inside the fuel fin.

[0018] A method for forming an identification gas capsule comprises the steps of: coupling a first end cap to a first end of a capsule tube to seal a first end of a capsule tube; inserting a heat-sensitive material into a capsule tube; applying heat to melt the heat-sensitive material and to cause the heat-sensitive material to flow into the first end cap; cooling the heat-sensitive material to cause the heat-sensitive material to solidify; inserting an identification gas into a capsule tube; and coupling a second end cap to a second end of a capsule tube to seal a second end of the capsule tube and to form an identification gas capsule.

[0019] The first end cap may include a flow hole formed therein, and the step of applying heat to melt a heat-sensitive material may further include a step of causing the heat-sensitive material to flow into the first end cap and block the flow hole.

[0020] In some cases, the flow hole is formed prior to the step of inserting the heat-sensitive material into the capsule tube. In other cases, the flow hole may be formed after the heat-sensitive material is inserted into the capsule tube. For example, once the heat-sensitive material is melted and flows into the end cap, the hole may be drilled through the end cap to expose the diameter of the solidified heat-sensitive material.

[0021] The heat-sensitive material may be selected from sodium and tin. Of course, the heat-sensitive material may be any suitable material that can be melted to cause the heat-sensitive material to flow and subsequently cooled to block the flow holes.

[0022] The first end of the capsule tube may be an upper end, and coupling a second end cap may include coupling a second end cap to the upper end of the capsule tube. In this way, the heat-sensitive material may form a plug near the lower end of the capsule tube.

[0023] In some cases, the first end of the capsule tube is the lower end, and coupling the second end cap involves coupling the second end cap to the lower end of the capsule tube. In this way, the heat-sensitive material may be able to form a plug near the upper end of the capsule tube.

[0024] The method may further include the step of inserting an identification gas capsule into the fuel pin. In some cases, the method includes coupling the identification gas capsule to the upper end cap of the fuel pin.

[0025] In some embodiments, the first end cap is the upper end cap of the fuel pin. This arrangement eliminates the separate end caps of the identification gas capsule, and the upper end cap of the fuel pin becomes an integral part of the identification gas capsule.

[0026] The method may further include the step of causing the heat-sensitive material to flow away from the first end cap by applying heat to melt the heat-sensitive material, thereby exposing a flow hole formed in the first end cap to allow the identification gas to escape the identification gas capsule through the flow hole.

[0027] According to some embodiments, a method for detecting a leak in a fuel pin comprises the steps of: providing an identification gas capsule in a fuel pin, wherein the identification gas capsule is formed to have a flow hole formed in the identification gas capsule, a heat-sensitive plug blocking the flow hole, and an identification gas inside the identification gas capsule; heating the fuel pin and the identification gas capsule to melt the heat-sensitive plug so as to unblock the flow hole and allow the identification gas to flow out of the identification gas capsule and into the fuel pin; sampling a primary coolant or cover gas of a reactor; and detecting the presence of the identification gas in the primary coolant or cover gas.

[0028] The heat-sensitive plug may be sodium, tin, or other required material that can be melted at an appropriate temperature and is compatible with the environment and / or materials in which the heat-sensitive plug is used.

[0029] A method for forming an identification gas capsule may include the steps of: coupling a first end cap to the first end of a capsule tube to seal the first end of the capsule tube; inserting a heat-sensitive material into the capsule tube; applying heat to melt the heat-sensitive material and to cause the heat-sensitive material to flow into the first end cap; cooling the heat-sensitive material to cause the heat-sensitive material to solidify; and coupling a second end cap to the second end of the capsule tube to seal the second end of the capsule tube and to form an identification gas capsule. The identification gas may be inserted into the capsule in a subsequent step, or by a different company. For example, the first company may manufacture the capsule but may not fill the capsule with identification gas. This may be done later by another company. The identification gas capsule may be filled by creating a hole in the identification gas capsule, for example, as in a plug, by filling the identification gas capsule with gas, and then sealing the hole. In some cases, forming and sealing holes may be performed by a laser. Brief explanation of the drawing

[0030] FIG. 1 illustrates various components of a nuclear reactor according to some embodiments. FIG. 2 is a schematic cross-sectional view of the core of a sodium-cooled fast reactor according to some embodiments. FIG. 3 is an exploded view of a core assembly according to some embodiments. FIG. 4 illustrates an exemplary embodiment of an identification gas capsule installed inside a fuel pin near an upper end cap, having an identification gas escape passage at the lower end of the identification gas capsule according to some embodiments. FIG. 5 illustrates an exemplary embodiment of an identification gas capsule installed inside a fuel pin, having an escape passage through the side of the capsule according to some embodiments. FIG. 6 illustrates an exemplary embodiment of an identification gas capsule integrated with an upper end cap according to some embodiments. FIG. 7 illustrates a process flow diagram showing a sample process for manufacturing an identification gas capsule according to some embodiments. Specific details for implementing the invention

[0031] The present disclosure generally relates to a method and system for an identification gas capsule that is simple to manufacture and install, does not have moving parts, and is passively activated. These results are achieved by creating an identification gas capsule that relies on a heat-based release system. According to some embodiments, a small identification gas capsule having an escape passage, such as a flow hole, for the identification gas is manufactured, and the escape passage is sealed by a heat-sensitive material. For example, the heat-sensitive material may be a material that melts at a temperature below or near the operating temperature of a reactor. Such suitable materials may include, but are not limited to, tin and / or sodium.

[0032] A small thermal plug or fuse may be added to the end of the capsule, and identification gas may be released from the capsule into the fuel pin by melting the plug or fuse by external heat after the fuel pin is manufactured. The plug or fuse may be formed to be very small, particularly compared to previous identification gas capsules, and the entire identification gas capsule may be significantly smaller than previous identification gas capsules. This may cause the overall fuel assembly length to be reduced compared to previous attempts, or the extra space saving may be used for other purposes, such as additional plenum volume for a longer life of the fuel pin.

[0033] Referring to FIG. 1, for additional context, many components and sub-assemblies of a representative reactor (100) are illustrated. For example, a reactor head (102), a reactor vessel (106) and a protective vessel (104), and many auxiliary reactor components such as structural members, flanges, cover plates, piping, rails, frames, connecting rods, and supports are illustrated. It should be recognized that while the illustrated reactor (100) is a sodium-cooled fast reactor (SFR), the components and embodiments described herein may be applied to any suitable reactor configuration. For example, the identification gas capsule embodiments described herein may be utilized in any reactor utilizing fuel pins that may experience rupture or leakage.

[0034] The reactor (100) is designed to hold a number of nuclear fuel pins (not shown) within a reactor core (108) located near the bottom of the reactor vessel (106). The reactor head (102) seals radioactive materials within the reactor vessel (106) and the protective vessel (104). In the illustrated embodiment, the reactor core (108) can be accessed only through the reactor head (102). For example, an in-vessel fuel handling machine (116) is provided. The fuel handling machine (116) allows the fuel pins and other core components and tools to be lifted from the core (108) and removed from the vessel (106) via a set of large and small rotary plugs (118) located within the reactor head (102). This design allows the reactor vessel (106) to be unified and without any penetration.

[0035] In some cases, sodium, which is liquid at reactor operating temperature, is the primary coolant for removing heat from the reactor core (108). The reactor vessel (106) is filled with sodium circulated through the reactor core (108) using pumps (110) up to a certain level. In some embodiments, two or more sodium pumps (110), which may be electromagnetic pumps, are provided. In some cases, one or more pumps (110) may include an impeller that can extend through the reactor head section (102) to a location above the reactor head section (102).

[0036] In some embodiments, pumps (110) are configured to circulate sodium through one or more intermediate heat exchangers (IHX) (112) located inside the reactor vessel (106). Sodium from a cold pool (122) near the bottom of the reactor vessel (106) is pumped into the core (108), where the sodium is heated by a nuclear fission reaction occurring inside the core. The heated sodium moves out of the core and into a hot pool (124) above the core. The sodium flows upward by natural circulation as the heated sodium has a lower density than the cold sodium in the cold pool, and also by forced pressure from one or more pumps (110). The heated sodium in the hot pool is introduced into the intermediate heat exchangers (112), which transfer heat from the primary sodium coolant to the secondary coolant flowing through the intermediate heat exchangers. A new secondary coolant is piped through the reactor head section (102) via one or more heat transfer loop pipes (120) to intermediate heat exchangers (112), where it is heated. The heated secondary coolant then flows out of the reactor head section (102) through the heat transfer loop pipes (120). In some embodiments, the heated secondary coolant is used to generate steam that is delivered to a power generation system. The secondary coolant may be a salt coolant, such as a sodium coolant or a magnesium sodium coolant.

[0037] FIG. 2 is a schematic cross-sectional view of the core (200) of an SFR. The core (200) is schematically illustrated and includes a central core area (202) having a plurality of core assemblies (204). The core assemblies (204) may include fissile fuel assemblies, fuel assemblies capable of being converted into fissile material, shielding assemblies, reflector assemblies, control assemblies, and pre-stacking assemblies, or material test assemblies. Generally, the contents of the assemblies (e.g., fissile material, control material, etc.) identify a specific assembly. The structural components of the assemblies holding such materials may be identical to facilitate mixing the core assemblies at any location around the core as required. The periphery core area (206) includes in-vessel storage pots (208). Throughout the entire lifespan of the core (200), fissile fuel assemblies and fuel assemblies capable of being converted into fissile material (as well as certain other assemblies) are mixed between the central core zone (202) and the periphery core zone (206). This is performed at various stages of the core lifespan as required or requested to initiate, maintain, accelerate, or terminate a nuclear reaction or generation, and / or for safety reasons.

[0038] The assemblies (204) are accommodated by the upper plate (210) of the core support structure (212) at locations sized and configured to accommodate the core assemblies (204). Sodium coolant is pumped into a plenum (214) positioned below the upper plate (210) and flows upward into the core assemblies (204), where the sodium coolant is heated by a nuclear reaction occurring inside the core (200). Structures guiding the flow of sodium through the core (202) and into the various assemblies are described below.

[0039] FIG. 3 is an exploded view of a core assembly (300). The core assembly (300) includes an elongated duct (302) having an axis (A). In some cases, the duct (302) has a hexagonal cross-section. A handling socket (304) having an internal flow passage is fixed to a first end (306) of the duct (302) and has an internal or external feature that allows the core assembly (300) to be raised, lowered, and otherwise moved into, out of, or inside the core by a mechanism inside the reactor vessel.

[0040] An inlet nozzle (308) is fixed to a second end (310) of the duct (302). A plurality of bearing rings (312) and retaining rings (314) are used to attach the handling socket (304) and the inlet nozzle (308) to the duct (302). When configured as a fuel assembly, a bundle of fuel pins (320) may be inserted into the duct (302). The fuel pins (320) are formed as a sheathing tube filled with fuel rods. The nuclear fuel rods may contain fissile fuel or fuel that can be converted into fissile material. A plurality of locking plates (316) (two in this example) and a plurality of pin strip rails (318) may be included near the end of the inlet nozzle (308). Locking fixing plates (316) and pin strip rails (318) together connect the pin bundle (320) to the inlet nozzle (308). Sealing rings (322) and a flow limiter (324) may also be integrated. The nozzle (308) defines a plurality of coolant inlet windows (326) that are in a state of flow communication with an internal flow chamber (not shown) extending through the nozzle (308). Thus, the windows (326) provide a path for sodium to flow into the nozzle (308) and into the duct (302), around the pin bundle (320) disposed therein. The sodium flow continues out of the handling socket (304). Generally, the core assemblies (300) are inserted into the reactor core such that the inlet nozzle (308) is first inserted into the reactor core and is positioned at the lower end of the core assembly and the handling socket (304) is positioned at the upper end of the core assembly.

[0041] FIG. 4 illustrates an exemplary identification gas capsule (400) according to some embodiments. In some cases, the identification gas capsule (400) comprises a capsule tube (402) having an upper end connector (404) at a first end and a bottom end plug (406) at a second end of the capsule tube (402). The bottom end plug (406) may be firmly coupled to the capsule tube and, in some cases, may be coupled to the capsule tube (402) by welding, such as laser welding or resistance pressure welding (RPW). The bottom end plug (406) may have a flow hole (408) formed therein, configured to allow the identification gas to escape once the flow hole (408) is exposed to form a flow path for the identification gas. The capsule tube (402) and the bottom end plug (406) may subsequently be filled with a small slug, which may be a temperature-sensitive material. While there are many temperature-sensitive materials available and suitable for use in the embodiments disclosed herein, for efficiency, the description will use sodium as an example of a suitable plug material. It should be understood and recognized that the use of sodium in the examples described throughout this disclosure is not limited. Once the sodium is inserted into the capsule tube (402), the sodium may be heated while the capsule tube is positioned vertically to melt the sodium, and thus the sodium flows into the bottom end plug (406). The flow hole (408) of the bottom end plug (406) may be closed during this filling process to prevent the molten sodium from leaking out of the flow hole (408). Once a sufficient amount of sodium is melted and the flow hole (408) is blocked, the sodium is cooled and solidified to create a sodium plug (410) that seals the flow hole (408).

[0042] In some embodiments, the identification gas capsule is installed within a fuel pin (412) having a covering (414) formed as a tube, an upper end cap (416) sealing one end of the covering, and a shielding slug closing the lower end of the covering (414). The identification gas capsule (400) may be positioned near the upper end cap (416) and may be molded to work with the upper end cap (416) to hold the identification gas capsule (400) in place. In some cases, the identification gas capsule (400) is fitted into a recess within the upper end cap (416) and thereby held in place. The identification gas capsule (400) may have an outer diameter smaller than the inner diameter of the covering (414) so ​​that an annular space exists between the identification gas capsule (400) and the inner diameter of the covering (414). This annular space will allow the identification gas to reach all welds, connections, and components constituting the fuel pin (412) once the identification gas escapes from the identification gas capsule (400). In some embodiments, the outer diameter of the identification gas capsule is less than 1 / 4 (6.35 mm) so that it fits inside the fuel pin. Of course, other dimensions are expected and are indicated only by the inner diameter of the fuel pin in which the identification gas capsule is installed.

[0043] After adding sodium to block the flow hole (408), the upper end connector (404) may be coupled to the capsule tube (402), for example, by welding. In some cases, connecting the upper end connector (404) may be performed in an atmosphere of identification gas so that the identification gas is captured inside the capsule tube (402) when the upper end connector (404) is attached, thereby capturing the identification gas inside the capsule tube (402). In some examples, a seal weld hole is formed at the interface between the upper end connector (404) and the capsule tube (402), and the identification gas may be inserted through the seal weld hole, and the seal weld hole may then be filled to capture the identification gas inside the capsule tube (402).

[0044] Once the identification gas capsule is formed, the sodium oxidation of the sodium plug (410) is relatively small due to the small diameter of the sodium plug exposed by the flow hole (408). In some cases, the flow hole (408) is formed with a diameter suitable for allowing the identification gas to escape, and may be about 1 / 32" (0.8 mm). In some cases, the flow hole has a diameter of less than 1 mm and provides a sufficient opening to allow the identification gas to escape. Of course, the disclosed diameter is given as an example, and it should be recognized that any suitable flow hole diameter may be used with the concepts and embodiments of the invention described herein. In some cases, the identification gas is pressurized inside the identification gas capsule such that its pressure is higher than the pressure of the fuel pin environment. In this way, the identification gas may be encouraged to flow out of the identification gas capsule once the plug (410) is removed from the flow hole (408).

[0045] In some cases, the fuel fin is heated before the fuel fin is installed in the fuel assembly, or before the fuel assembly is installed in the reactor, or after the fuel assembly is installed in the reactor. In any case, when the fuel fin is heated, which may be performed during fuel loading (e.g., sodium attachment) or heat treatment, the sodium plug (410) will melt and flow into the fuel fin and ultimately flow downward to the bottom of the fuel fin near the shielding slug that seals the bottom of the fuel fin. Of course, the sodium plug (410) may also melt during the operation of the reactor.

[0046] In some embodiments, the bottom end plug (406) and the capsule tube (402) may be formed as a single component, and accordingly, the step of coupling the bottom end plug (406) to the capsule tube (402) may be omitted. The disclosed components may be formed of any suitable material and, in some cases, may include stainless steel, HT9 steel, or any other suitable material compatible with the reactor core environment.

[0047] It should be recognized that the identification gas capsules described herein may be inserted into any core assembly. For example, an identification gas capsule may be inserted into a control pin within a control assembly and may be used to monitor the integrity of the control pin. This provides assurance that any material inside the control pin, such as neutron-absorbing material, will not leak out due to a failure of the control pin.

[0048] FIG. 5 illustrates another embodiment of the identification gas capsule (400). In the illustrated embodiment, a sodium plug (502) may be formed inside the upper end connector (404) of the identification gas capsule (400). In making this embodiment, the upper end connector (404) may first be coupled to the capsule tube (402) by any suitable method, and then sodium may be inserted into the capsule tube (402) while the capsule tube is inverted. The capsule tube (402) and the upper end connector (404) may then be heated to melt the sodium, and the material will flow into and settle into the space inside the upper end connector (404). The upper end connector may be formed to have one or more flow holes (504) that are blocked by the molten sodium before the molten sodium solidifies into the sodium plug (502). In some cases, a single flow hole (504) is sufficient to allow the identification gas to escape once the sodium plug is melted, although it should be obvious that additional flow holes (504) may be provided to allow the identification gas to escape more quickly. In some cases, two, three, four, or six holes are formed radially within the upper end connector (404).

[0049] Once the sodium plug (502) is formed, the capsule can be filled with identification gas, and the bottom end plug (506) can be attached to the capsule tube (402). In some cases, the bottom end plug (506) may be formed to have a small hole that can be used to fill the identification gas after the bottom end plug (506) is coupled to the capsule tube, and the small hole can be closed, for example, by photo-laser welding, once the identification gas is added to the capsule tube (402). By using the bottom end plug (506) as illustrated, when the sodium plug is melted while placed in the illustrated orientation, the sodium will flow down the capsule tube until it settles against the bottom end plug (506) and will not be able to enter the fuel pin.

[0050] FIG. 6 illustrates another embodiment of an identification gas capsule (400) in which the upper end cap (416) of the fuel pin (412) is formed integrally with the identification gas capsule (400). In this embodiment, the upper end cap of the identification gas capsule (400) shown in the previous embodiment may be omitted, and the capsule tube (402) may be directly coupled to the upper end cap (416) of the fuel pin (412).

[0051] The upper end cap (416) may have a first section (602) having a first diameter equal to the diameter of the covering (414) to facilitate joining the upper end cap (416) to the covering (414). The upper end cap (416) and the covering (414) may be coupled together by any suitable method, including welding. The upper end cap (416) may further include a second section (604) having a second diameter smaller than the first diameter and configured to allow the second section (604) to be inserted into the covering (414). The second section (604) may have a hollow space (606) (e.g., a counterbore) configured to accommodate a sodium plug (502).

[0052] The second section (604) of the upper end cap (416) may be formed to have one or more flow holes (504) through the sidewalls of the second section (604) to allow identification gas to escape through it upon melting of the sodium plug (502). During manufacturing, the weld of the upper end cap (416) and the capsule tube (402) may be inverted, and solid sodium, which may be in an amount sufficient to fill the hollow space (606) within the second section (604) of the upper end cap (416), may be placed therein. The weld may then be heated to liquefy the sodium, and thus the sodium flows to occupy the hollow space (606). The second section (604) of the upper end cap (416) may subsequently be drilled to create one or more flow holes (504) for the identification gas to escape the identification gas capsule (400) once the sodium plug (502) is melted. Of course, the flow holes (504) may be created before the sodium is inserted or after the sodium plug is formed.

[0053] Once the sodium plug (502) is placed in place, the capsule tube (402) can be filled with identification gas, and the bottom end cap (506) can then be attached to the capsule tube (402). After fabrication, the combination of the capsule tube (402) and the bottom end cap (506) of the upper end cap (416) can together form an identification gas capsule (400) that can be inserted into the fuel fin covering (414) and permanently attached to the fuel fin covering (414).

[0054] As with any of the embodiments described herein, the identification gas capsule provides identification gas inside the fuel fin, which is released only when the identification gas capsule is exposed to heat to melt the sodium plug and to release the identification gas so that the identification gas flows inside the fuel fin. Then, in the event of a leak in the fuel fin, the identification gas will escape the fuel fin through the leak, which can be detected in the primary coolant or in the cover gas inside the reactor vessel.

[0055] In any of the embodiments described herein, the identification gas may be pressurized to facilitate the flow of the identification gas out of the capsule and into the fuel pin. In some embodiments, the fuel pin has an internal pressure of about 1 atmosphere, and the identification gas capsule may be pressurized to slightly above 1 atmosphere, such as 1.1 atmosphere, 1.2 atmosphere, 1.3 atmosphere, 1.5 atmosphere, or higher atmospheres. This may be achieved, for example, by inserting the identification gas capsule into a chamber pressurized by the identification gas, by perforating a hole to allow the pressurized identification gas to flow through the hole, and then sealing the hole. In some cases, the entire identification gas capsule is fabricated and sealed without the identification gas. In a subsequent step, the identification gas capsule may be perforated, filled with identification gas, and then resealed. As described above, this can be achieved by placing an identification gas capsule inside a chamber pressurized by identification gas, perforating the capsule, and then sealing the perforation inside the chamber.

[0056] FIG. 7 illustrates a process flowchart illustrating a sample process (700) for producing identification gas capsules described herein. In block (702), a capsule tube is provided.

[0057] The capsule tube may have a circular cross-section, but may also have other cross-sectional shapes, such as hexagonal, octagonal, elliptical, or some other suitable shape.

[0058] In block (704), a first end cap is coupled to the capsule tube to seal the first end of the capsule tube. The first end cap may be coupled by any suitable method, such as welding, adhesive, screwing, or other methods.

[0059] In block (706), a heat-sensitive material is inserted into a capsule tube. The heat-sensitive material may be any suitable material that is solid at ambient temperature and can be melted by applied heat. Such suitable materials may include, but are not limited to, sodium, tin, tin-containing alloys, or other metallic or non-metallic materials having a melting temperature lower than the operating temperature of a nuclear reactor. In some cases, the heat-sensitive material is first melted and then poured into the capsule tube, where the heat-sensitive material flows to the bottom of the capsule tube and takes the shape of a first end cap. In some cases, where a flow hole is already formed within the first end cap, the heat-sensitive material does not escape through the flow hole due to the size of the flow hole combined with the viscosity of the molten heat-sensitive material, based on the surface tension of the heat-sensitive material or a combination thereof. In some cases, the flow hole may be blocked from the outside of the capsule tube to prevent the heat-sensitive material from flowing out of the flow hole.

[0060] In block (708), heat is applied to the capsule tube to melt the heat-sensitive material and to cause the heat-sensitive material to flow into the first end cap. In some cases, the first end cap includes a recess into which the heat-sensitive material flows. Additionally, the first end cap may also be formed to have one or more flow holes. The flow holes may be formed before the heat-sensitive material is added to the capsule tube, or after the heat-sensitive material is added to the capsule tube.

[0061] In block (710), identification gas is inserted into the capsule tube. In some cases, the identification gas is inserted at a predetermined pressure greater than 1 atmosphere to pressurize the identification gas inside the capsule tube.

[0062] In block (712), a second end cap is coupled to the capsule tube to seal the second end of the capsule tube. The second end cap may be coupled by any suitable method, such as welding, adhesive, screwing, interference, or any other suitable coupling method. In some cases, either the first end cap or the second end cap may be the upper end cap of the fuel clad tube and may be used to seal the end of the fuel clad tube. In other cases, the first end cap or the second end cap may be coupled to the upper end cap of the fuel clad tube and may be held in place by any suitable method, such as welding, adhesive, friction, screwing, pin fixing, or others.

[0063] In block (714), an identification gas capsule is inserted into the fuel pin. For example, the identification gas capsule may be attached to the upper end cap of the fuel pin and, when the upper end cap is attached to the fuel cladding, it may be inserted into the fuel cladding.

[0064] In block (716), the fuel pin is heated, which melts the heat-sensitive material, and the heat-sensitive material then flows downward by gravity and exposes one or more flow holes through which the identification gas escapes into the fuel pin and around the fuel volume accompanying the fuel pin. In some cases, this step of melting the heat-sensitive material and causing the identification gas to flow out of the identification gas capsule and into the fuel pin is performed during the manufacture of the fuel pin and before the fuel pin is integrated into the fuel assembly. The identification gas capsule may be inspected for proper operation by performing an eddy current test that shows a magnetic cross-sectional response, which can, for example, identify a sodium plug blocking the flow hole and further identify the point in time when the sodium plug melted and exposed the flow hole.

[0065] Eddy current testing is a non-destructive testing method used to evaluate the integrity of conductive materials. It relies on the generation of eddy currents (circulating currents induced by a changing magnetic field). An alternating current is passed through a coil to generate this magnetic field. When the coil is moved near a conductive material, such as metal, the coil induces eddy currents within the material.

[0066] Subsequently, the interaction between these induced currents and the properties of the material is analyzed. Changes in the material's electrical conductivity, permeability, or geometry, which are often associated with defects such as cracks or corrosion, affect the eddy currents. Inspections are typically performed using probes or sensor coils, and specialized tools measure parameters such as impedance and phase angle to identify and characterize defects. Eddy current testing can, accordingly, determine whether the sodium plug is located at a position to block the flow hole, or whether the sodium plug has melted and moved to a location where the flow hole is not blocked.

[0067] Subsequently, during reactor operation, if a fuel fin leak or rupture occurs, the identification gas will escape the fuel fin and be detected outside the fuel fin.

[0068] While some examples describe adding an identification gas capsule to the upper end of a fuel pin, it is expected that the identification gas capsule may be installed near the lower end of the fuel pin or at any location along the fuel pin. However, in many cases, the identification gas capsule is installed at one end of the fuel pin or at the other end of the fuel pin. In some examples, each fuel pin within the fuel assembly is prepared to have an identification gas capsule.

[0069] The foregoing description of specific embodiments will sufficiently reveal the general nature of the embodiments of the present disclosure, so that others, by applying the knowledge of those skilled in the art, can easily modify and / or adapt such specific embodiments for various applications without departing from the general concept of the embodiments of the present disclosure and without excessive experimentation. Accordingly, such adaptation and modification are intended to be placed within the meaning and scope of equivalents of the disclosed embodiments based on the teachings and guidelines set forth in this specification. The phrases or terms of this specification are for illustrative purposes only and are not intended to be limiting, and the terms or phrases of this specification should be interpreted by those skilled in the art in light of the teachings and guidelines set forth in this specification.

[0070] The breadth and scope of the embodiments of the present disclosure should not be limited by any of the exemplary embodiments described above, but instead should be limited solely by the following claims and their equivalents.

[0071] Above all, conditional language such as “able to,” “able to,” “will be able to,” or “will be able to,” is generally intended to convey that certain embodiments include certain features, elements, and / or operations, among which other embodiments do not include, unless otherwise specifically stated or otherwise understood within the context in which they are used. Accordingly, such conditional language is generally not intended to imply that features, elements, and / or operations are required in any way for one or more embodiments, or that one or more embodiments necessarily include logic for determining, with or without user input, whether these features, elements, and / or operations should be included or performed in any particular embodiment.

[0072] Throughout this specification, the term “substantially” referring to a given parameter, attribute, or condition may mean, and may include, an extent to which a person skilled in the art understands that the given parameter, attribute, or condition is satisfied with a small degree of variation, such as within acceptable manufacturing tolerances. For example, depending on a particular parameter, attribute, or condition that is substantially satisfied, the parameter, attribute, or condition may be satisfied at least approximately 90%, at least approximately 95%, or even at least approximately 99%.

[0073] As used herein, the terms “about” and “approximately” indicate, in some examples, a variability of up to ±5% of the associated figure, e.g., up to ±2%, or up to ±1%.

[0074] Those skilled in the art will recognize that any process or method disclosed herein may be modified in many ways. The order of process parameters and steps described and / or illustrated herein is given merely as an example and may be changed as needed. For example, steps illustrated and / or described herein may be shown or discussed in a specific order, but these steps do not necessarily have to be performed in the order described or discussed.

[0075] Various exemplary methods described and / or illustrated in this specification may also omit one or more of the steps described or illustrated in this specification, or may include additional steps in addition to the disclosed steps. Additionally, any step of any method as disclosed in this specification may be combined with any one or more steps of any other method as disclosed in this specification.

[0076] Of course, it is impossible to describe every conceivable combination of elements and / or methods for the purpose of describing the various features of the present disclosure, but those skilled in the art recognize that many additional combinations and substitutions of the disclosed features are possible. Accordingly, various modifications may be made to the present disclosure without departing from the scope or spirit of the present disclosure. Additionally, other embodiments of the present disclosure may become apparent from consideration of the present specification and the accompanying drawings and from the practice of the disclosed embodiments as presented in the present specification. The examples presented in the present specification and the accompanying drawings should be considered, in all respects, illustrative and non-limiting. Although specific terms are used herein, they are used only in a general and descriptive sense and are not intended for limiting purposes.

[0077] Unless otherwise noted, the term “indefinite article” as used herein shall be interpreted to mean “at least one of”. Finally, for convenience of use, the terms “comprising” and “having” (and their derivatives) as used herein are interchangeable with and have the same meaning as the word “comprising”.

[0078] From the foregoing and the accompanying drawings, it will be recognized that, although specific embodiments have been described herein for illustrative purposes, various modifications may be made without departing from the spirit and scope of the appended claims and the elements incorporated herein. Additionally, while specific embodiments are presented below in specific claim forms, the inventors anticipate various embodiments of any available claim forms. For example, only some embodiments may be referred to as being currently implemented in specific configurations, but other embodiments may likewise be implemented in such a way. As will be apparent to those skilled in the art having an interest in this disclosure, various modifications and changes may be made. This is intended to accommodate all such modifications and changes, and accordingly, the foregoing description should be considered in an illustrative sense rather than a restrictive one.

Claims

Claim 1 An identification gas capsule comprising: a capsule tube having a first end and a second end; a first end cap coupled to the capsule tube and sealing the first end of the capsule tube; a second end cap coupled to the capsule tube and sealing the second end of the capsule tube; a flow hole formed in one or more of the capsule tube, the first end cap, and the second end cap; an identification gas disposed inside the capsule tube; and a thermally sensitive material disposed inside the identification gas capsule to block the flow hole, the thermally sensitive material comprising a thermally sensitive material configured to melt at a temperature below the reactor operating temperature to expose the flow hole and allow the identification gas to escape through the flow hole. Claim 2 In paragraph 1, the heat-sensitive material is sodium, an identification gas capsule. Claim 3 In paragraph 1, the identification gas capsule, wherein the heat-sensitive material is tin or a tin-containing alloy. Claim 4 An identification gas capsule according to claim 1, wherein the flow hole is formed to have a diameter of less than 1 mm. Claim 5 In paragraph 1, the identification gas capsule is configured to be inserted into a nuclear fuel pin. Claim 6 In paragraph 5, the identification gas capsule is an identification gas capsule having an outer diameter of less than 6.35 mm. Claim 7 An identification gas capsule according to claim 1, wherein the flow hole is formed at a location near the upper end of the identification gas capsule so that the heat-sensitive material flows downward and is captured inside the identification gas capsule once it is melted. Claim 8 An identification gas capsule according to claim 1, wherein the flow hole is formed at the bottom end of the identification gas capsule so that the heat-sensitive material flows out of the identification gas capsule once it is melted. Claim 9 A method for forming an identification gas capsule, comprising the steps of: coupling a first end cap to a first end of a capsule tube to seal a first end of a capsule tube; inserting a heat-sensitive material into a capsule tube; applying heat to melt the heat-sensitive material and to cause the heat-sensitive material to flow into the first end cap; cooling the heat-sensitive material to cause the heat-sensitive material to solidify; inserting an identification gas into a capsule tube; and coupling a second end cap to a second end of a capsule tube to seal a second end of the capsule tube and to form an identification gas capsule. Claim 10 A method for forming an identification gas capsule according to claim 9, wherein the first end cap comprises a flow hole formed therein, and the step of applying heat to melt a heat-sensitive material further comprises causing the heat-sensitive material to flow into the first end cap and blocking the flow hole. Claim 11 A method for forming an identification gas capsule according to claim 10, wherein the flow hole is formed prior to the step of inserting a heat-sensitive material into a capsule tube. Claim 12 A method for forming an identification gas capsule according to claim 9, wherein the heat-sensitive material is selected from sodium and tin. Claim 13 A method for forming an identification gas capsule according to claim 9, wherein the first end of the capsule tube is an upper end, and coupling the second end cap includes coupling the second end cap to the lower end of the capsule tube. Claim 14 A method for forming an identification gas capsule according to claim 9, wherein the first end of the capsule tube is a lower end, and coupling the second end cap includes coupling the second end cap to the upper end of the capsule tube. Claim 15 A method for forming an identification gas capsule according to claim 9, further comprising inserting the identification gas capsule into a fuel pin. Claim 16 A method for forming an identification gas capsule according to claim 9, further comprising coupling the identification gas capsule to the upper end cap of the fuel pin. Claim 17 A method for forming an identification gas capsule according to claim 9, wherein the first end cap is the upper end cap of the fuel pin. Claim 18 A method for forming an identification gas capsule according to claim 9, further comprising the step of causing the heat-sensitive material to flow away from the first end cap by applying heat to melt the heat-sensitive material, thereby exposing a flow hole formed in the first end cap to allow the identification gas to escape the identification gas capsule through the flow hole. Claim 19 A leak detection method comprising: providing an identification gas capsule within a fuel pin, wherein the identification gas capsule is formed to have a flow hole formed within the identification gas capsule, a heat-sensitive plug blocking the flow hole, and an identification gas within the identification gas capsule; heating the fuel pin and the identification gas capsule to melt the heat-sensitive plug to unblock the flow hole and allow the identification gas to flow out of the identification gas capsule and into the fuel pin; sampling a primary coolant or cover gas of a reactor; and detecting the presence of the identification gas within the primary coolant or cover gas. Claim 20 In paragraph 19, the leak detection method, wherein the heat-sensitive plug is sodium, tin, or a tin-containing alloy.

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