High-Barrier Packaging Apparatus and Packaging Material for UO₂ Powder

Abstract

The present invention relates to packaging technology for uranium oxide (UO₂) powder used in a nuclear fuel manufacturing process, and more specifically, to a high-barrier packaging material and a packaging device applying the same that can maintain the chemical stability of the UO₂ powder by preventing reaction with oxygen and moisture in the external air. The packaging device of the present invention comprises: a buffer hopper (110) in which UO₂ powder is temporarily stored; a feeder hopper (120) into which UO₂ powder is fed from the buffer hopper (10); and a first packing part (130) that fills a predetermined amount of UO₂ powder discharged from the buffer hopper (10) into a first pouch (210). It includes a second packing section (140) for performing secondary packing on the first pouch (210) delivered from the first packing section (30), wherein the buffer hopper (10) and the feeder hopper (120) are maintained in an inert atmosphere with an oxygen concentration of 1% or less, and the first pouch (210) and the second pouch (220) are formed of a high-barrier packaging material with limited oxygen and moisture permeability, so that UO₂ powder is filled and sealed without coming into contact with external air.

Description

Technology Field

[0001] The present invention relates to packaging technology for uranium oxide (UO₂) powder used in nuclear fuel manufacturing processes, and more specifically, to a high-barrier packaging material and a packaging device applying the same that can maintain the chemical stability of UO₂ powder by preventing reaction with oxygen and moisture in the external air. Background Technology

[0002] Uranium oxide (UO₂) powder used in the nuclear fuel manufacturing process is a material with a very high affinity for oxygen and the property of oxidizing easily even in the atmosphere. UO₂ powder readily reacts with oxygen in the air to convert into higher-order oxides such as U₄O₅ or U₃O₅, and this oxidation reaction is also accelerated by moisture. Generally, the degree of oxidation of UO₂ powder is expressed by the oxygen-to-uranium ratio (O / U ratio); as this value exceeds 2.0, chemical stability decreases, making it difficult to obtain the desired sintering characteristics during the manufacture of nuclear fuel pellets. Therefore, it is very important to minimize the ingress of external oxygen and moisture during the storage and handling of UO₂ powder.

[0003] UO₂ powder for nuclear fuel is typically produced through a conversion or reduction process, followed by granulation, molding, and sintering steps for manufacturing pellets. However, it often needs to be stored or transported for a certain period before being fed into these subsequent processes. In particular, facilities producing nuclear fuels with different uranium enrichment levels often require the storage of UO₂ powder of a specific enrichment level for a certain period; there have been reports of cases where the quality deteriorates and the powder is disposed of if oxidation or aggregation occurs during long-term storage. Therefore, storage and packaging technologies capable of reliably protecting UO₂ powder from oxidation and moisture adsorption are essential.

[0004] Conventionally, a method of measuring the dew point in a nitrogen atmosphere inside a cooling hopper has been proposed as a technique for managing the moisture content of UO₂ powder (e.g., Registered Patent No. 10-2117493). While this technique is useful for quality control by measuring moisture content in real time while cooling high-temperature UO₂ powder discharged from the conversion furnace, it is limited to moisture measurement during the manufacturing process and cannot fundamentally prevent external air infiltration during long-term storage or the packaging stage for export. In other words, if oxygen or moisture from the air remains during the packaging process following cooling and measurement, the UO₂ powder undergoes oxidation and aggregation over time, leading to problems such as reduced powder fluidity, uneven mixing, and decreased strength of the sintered body.

[0005] Meanwhile, various film materials are used across industries for the storage and packaging of powdered materials, but films with a general polyamide / polyethylene (NY / PE) structure are difficult to satisfy the oxygen and moisture barrier performance required for nuclear fuel powders. Since UO₂ powders undergo chemical reactions even with trace amounts of moisture or oxygen, permeability levels comparable to those of general food and pharmaceutical packaging materials are insufficient. In particular, a water vapor transmission rate (WVTR) of 0.1 g / m²·day or less and an oxygen vapor transmission rate (OTR) of 1 cc / m²·day·atm or less are required.

[0006] However, current technology remains at the level of addressing the barrier performance of packaging materials or the automation of the packaging process individually, and dedicated packaging systems optimized for the characteristics of UO₂ powder have rarely been proposed. In particular, safety standards for nuclear fuel manufacturing facilities require that the packaging equipment itself ensure nuclear criticality safety and satisfy specific safety requirements.

[0007] Therefore, there is a need to develop high-barrier packaging materials that can shield UO₂ powder discharged from the nuclear fuel manufacturing process from external oxygen and moisture and maintain chemical stability during long-term storage or export, as well as packaging devices capable of automatically filling and sealing them. Such technology is significant not only for improving storage efficiency but also for ensuring quality consistency in nuclear fuel production and enhancing radiation safety. Prior art literature

[0008] Registered Patent Publication No. 10-2117493 (Date of publication: June 1, 2020) The problem to be solved

[0009] The present invention aims to improve upon these problems by providing a high-barrier packaging material and a packaging device applying the same, which prevents the reaction of uranium oxide (UO₂) powder used in the nuclear fuel manufacturing process with oxygen and moisture in the external air to maintain the chemical stability of the UO₂ powder. means of solving the problem

[0010] A high-barrier packaging device for UO₂ powder according to the present invention for achieving the above purpose comprises a buffer hopper in which UO₂ powder is temporarily stored, a feeder hopper into which UO₂ powder is transferred and fed from the buffer hopper; a first packing section for filling a predetermined amount of UO₂ powder supplied from the feeder hopper into a first pouch; and a second packing section for performing secondary packaging on the first pouch filled in the first packing section, wherein the buffer hopper and the feeder hopper are maintained in an inert atmosphere with an oxygen concentration of 1% or less, and the first pouch and the second pouch are formed of a high-barrier packaging material having limited oxygen and moisture permeability, so that the UO₂ powder is filled and sealed without coming into contact with external air.

[0011] Preferably, the buffer hopper and feeder hopper are configured to maintain an inert atmosphere by supplying nitrogen (N₂) gas.

[0012] Preferably, a metering unit for measuring a precise amount of UO₂ powder is installed at the bottom of the feeder hopper, and more preferably, the first packing unit is configured to perform primary sealing by a heat sealing method after filling the metered UO₂ powder into a first pouch.

[0013] More preferably, the first packing part and the second packing part are both installed within a sealed room, and the sealed room is maintained in a negative pressure state so as to prevent the external scattering of UO₂ powder.

[0014] Next, the high-barrier packaging material for UO₂ powder is formed as a multilayer film in which a polymer film layer, a metal barrier layer, and a heat-sealable layer are laminated sequentially from the outside, wherein the polymer film layer is formed of at least one of polyamide (PA), polyethylene terephthalate (PET), or vinylidene chloride (PVDC), the metal barrier layer is formed of aluminum (Al) or aluminum oxide (ALOx), and the heat-sealable layer is formed of polyethylene (PE) and sealed by heat sealing, wherein the packaging material has a barrier performance with an oxygen permeability of 1 cc / m²·day·atm or less and a moisture permeability of 0.1 g / m²·day or less, and is characterized by being sealed in a double-packaged state by applying two or more layers of the packaging material made of the same material.

[0015] Preferably, each layer of the packaging material consists of a polyamide layer, an aluminum foil layer, and a polyethylene layer from the outside. Effects of the invention

[0016] According to the present invention, the following direct and specific effects can be obtained.

[0017] First, by maintaining the buffer hopper and feeder hopper under an inert atmosphere filled with nitrogen gas, contact between the UO₂ powder and oxygen or moisture in the air during the filling process can be effectively blocked. Consequently, oxidation reactions (U₃O₅ conversion) or hydration reactions of the powder can be fundamentally prevented, thereby maintaining chemical stability even during long-term storage after packaging.

[0018] Second, by sequentially performing primary packaging in the first packing section and secondary packaging in the second packing section, the UO₂ powder is doubly blocked from the external environment. In particular, by applying the first pouch and the second pouch made of the same high-barrier packaging material, the permeation of oxygen and moisture can be significantly suppressed, and durability against external impact or mechanical damage during transport is also improved.

[0019] Third, as the sealed room is maintained under negative pressure, it prevents the external scattering of fine UO₂ powder that may occur during the packaging process, and simultaneously prevents worker exposure and environmental pollution by purifying the internal air through a HEPA filter before discharge.

[0020] Fourth, by supplying a precise amount of powder through the metering unit, uniformity of the packaging weight can be ensured, which enables precise control of the input amount required in the nuclear fuel molding process.

[0021] Fifth, by applying a heat-sealing sealing structure, the packaging can be hermetically sealed without the use of separate adhesives or solvents, and internal residual oxygen can be minimized by simultaneously performing a gas exchange process during this process.

[0022] Sixth, since the packaging process is performed in a sealed space under an inert atmosphere and negative pressure, worker safety and process consistency are improved, and key safety requirements for environments handling radioactive powder can be satisfied. Brief explanation of the drawing

[0023] FIG. 1 is a configuration diagram of a high-barrier packaging device for UO₂ powder according to an embodiment of the present invention. Specific details for implementing the invention

[0024] The specific structural or functional descriptions presented in the embodiments of the present invention are merely illustrative for the purpose of explaining embodiments according to the concept of the present invention, and embodiments according to the concept of the present invention may be implemented in various forms. Furthermore, it should not be interpreted as being limited to the embodiments described herein, but should be understood to include all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention.

[0025] Meanwhile, the terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to specify the existence of the implemented features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0027] FIG. 1 is a configuration diagram of a high-barrier packaging device for UO₂ powder according to an embodiment of the present invention.

[0028] Referring to FIG. 1, a high-barrier packaging device for UO₂ powder according to an embodiment of the present invention (hereinafter also abbreviated as "packaging device") comprises a buffer hopper (110) in which UO₂ powder is temporarily stored, a feeder hopper (120) into which UO₂ powder is fed from the buffer hopper (10), a first packing section (130) for filling a predetermined amount of UO₂ powder discharged from the buffer hopper (10) into a first pouch (210), and a second packing section (140) for performing secondary packing on the first pouch (210) delivered from the first packing section (30). The buffer hopper (110) and the feeder hopper (120) are maintained in an inert atmosphere with an oxygen concentration of 1% or less, and the first pouch (210) and the second pouch (220) are formed of a high-barrier packaging material having limited oxygen and moisture permeability, so that the UO₂ powder It is characterized by being filled and sealed without contact with external air.

[0029] The buffer hopper (110) is a container in which UO₂ powder is temporarily stored before being transferred to the packaging process, and its capacity is typically set to a range of about 1.0 to 1.5 m³, and nitrogen (N₂) gas is supplied inside to maintain the oxygen concentration at 1% or less.

[0030] The upper part of the buffer hopper (110) has a cylindrical shape, and the lower part has a cone-shaped structure that is narrowed. The angle of inclination of the lower cone is set to a range of approximately 25° to 35° so that powder is discharged smoothly without residue. The outer wall of the buffer hopper (110) is made of stainless steel with a thickness of 4 mm or more, and an oxygen sensor for monitoring oxygen concentration is installed inside, and a nitrogen supply line and a pressure relief valve are provided at the top. With this configuration, the buffer hopper (110) is designed so that the effective multiplication factor (k_eff) is maintained at 0.95 or less in accordance with the nuclear criticality safety standard (ANSI / ANS-8.1), and safety is ensured under conditions where the moisture content of the powder is managed at 4.7 wt% or less.

[0031] A feeder hopper (120) is connected to the lower part of the buffer hopper (110) and performs the function of temporarily storing UO₂ powder supplied from the buffer hopper (110) and then transferring it in a fixed amount through the lower metering unit (121).

[0032] The feeder hopper (120) is maintained under an inert nitrogen atmosphere, just like the buffer hopper, and the internal oxygen concentration is controlled to 1% or less.

[0033] The weighing unit (121) can be configured as a load sensor-based electronic weighing device or a screw feeder, and automatically adjusts the amount of powder conveyed according to the target weight value input from the control unit.

[0034] By combining the feeder hopper (120) and the weighing unit (121) in this way, the weight variation of the packaged UO₂ powder can be minimized, and the quality uniformity of the subsequent packaging process can be ensured, and the weighed UO₂ powder is transferred to the first packing unit (130).

[0035] The first packing section (130) consists of a process of filling powder into the first pouch (210) and sealing it by a heat sealing method, and gas exchange is performed during the filling process to prevent the mixing of oxygen or moisture during packaging.

[0036] That is, the inside of the filling chamber is flushed with nitrogen gas to expel internal air, and the oxygen concentration is maintained at about 0.5 to 1.0% or less. The heat sealing part operates under conditions of a temperature of about 150 to 180°C and a compression pressure of about 0.3 to 0.5 MPa to melt the heat-fusion layer (PE layer) of the first pouch (210) and seal it airtightly.

[0037] The packaging material used at this time is a high-barrier film with a three-layer structure consisting of a polyamide layer, an aluminum foil layer, and a polyethylene layer, having an oxygen permeability of 1 cc / m²·day·atm or less and a moisture permeability of 0.1 g / m²·day or less.

[0038] The first pouch (210) sealed in the first packing section (130) is transferred to the second packing section (140) and received in the second pouch (220).

[0039] The second packing section (140) is an external packaging process that wraps the first pouch, uses the same high-barrier packaging material, and performs secondary sealing with heat sealing under the same conditions as the first pouch.

[0040] Due to the double packaging structure, the internal UO₂ powder remains completely sealed off from external air or moisture, preventing oxidation (U₃O₅ conversion) or hydration reactions during transport and storage.

[0041] Additionally, the second packing section (140) may be equipped with an exhaust line to remove residual air that may occur during packaging, and may be configured to maintain a constant internal pressure of the pouch after packaging.

[0042] The first packing section (130) and the second packing section (140) are both installed inside the sealed room (101). The sealed room (101) is maintained in a negative pressure state to prevent the external leakage of fine UO₂ powder that may be scattered during the packaging process, and generally maintains a pressure difference of about -5 to -10 mmAq. Preferably, the air inside the sealed room (101) is exhausted through a HEPA filter, and if necessary, an activated carbon filter is added to block the external emission of radioactive particles. Such a sealed room structure serves as an important technical means to ensure the safety of packaging workers and prevent contamination of the external environment.

[0043] Meanwhile, the packaging film supply unit (102) is a device that supplies roll-shaped packaging material to the first packing unit (130) and the second packing unit (140), and can be used in common in both packing units.

[0044] The film supply unit (102) can be configured to continuously supply packaging material while maintaining a constant tension and to automatically correct alignment errors of the film during heat sealing.

[0045] Finally, the UO₂ powder package (200), which has been double-sealed in the second packing section (140), can be placed in an external transport container (CAN) within a sealed room. While placed, a weight inspection device checks whether the total weight of the package is within the specified range, and if an abnormal weight is detected, repackaging or re-inspection is performed.

[0046] The packaging (200) manufactured through this series of processes is discharged outside the sealed room (101).

[0047] The present invention described above is not limited by the aforementioned embodiments and attached drawings, and it will be obvious to those skilled in the art that various substitutions, modifications, and changes are possible within the scope of the technical concept of the present invention. Explanation of the symbols

[0048] 101: Sealed room 102: Packaging material film supply unit 110 : Buffer Hopper 120 : Feeder Hopper 121: Weighing section 130: First packing section 140 : 2nd packing section 200 : UO2 powder packaging body 210 : 1st pouch 220 : 2nd pouch

Claims

Claim 1 A high-barrier packaging material for Uranium Oxide (UO₂) powder, characterized in that the packaging material is formed as a multilayer film in which a polymer film layer, a metal barrier layer, and a heat-sealable layer are laminated sequentially from the outside, wherein the polymer film layer is formed of at least one of polyamide (PA), polyethylene terephthalate (PET), or vinylidene chloride (PVDC), the metal barrier layer is formed of aluminum (Al) or aluminum oxide (ALOx), and the heat-sealable layer is formed of polyethylene (PE) and sealed by heat sealing, wherein the packaging material has a barrier performance with an oxygen permeability of 1 cc / m²·day·atm or less and a moisture permeability of 0.1 g / m²·day or less, and a pouch made of the same packaging material is applied in two or more layers to be sealed in a double-packaged state. Claim 2 A packaging material according to claim 1, characterized in that each layer of the packaging material is composed of a polyamide layer, an aluminum foil layer, and a polyethylene layer from the outside. Claim 3 A high-barrier packaging device for UO₂ powder using the packaging material of claim 1 or 2, wherein UO₂ powder is temporarily stored, a cone portion is formed at the bottom, and an internal effective multiplication factor (k eff A high-barrier packaging device for UO₂ powder, comprising: a buffer hopper designed to maintain the value of ) at 0.95 or less; a feeder hopper including a metering unit (121) for the amount of UO₂ powder transferred and fed from the buffer hopper; a first packing unit for filling the UO₂ powder supplied from the feeder hopper into a first pouch; and a second packing unit for receiving the first pouch sealed in the first packing unit into a second pouch, wherein the buffer hopper and the feeder hopper are maintained in an inert atmosphere with an oxygen concentration of 1% or less, and the first pouch and the second pouch are formed of the packaging material such that the oxygen and moisture permeability is limited, so that the UO₂ powder is filled and sealed without contact with external air. Claim 4 A high-barrier packaging device for UO₂ powder according to paragraph 3, characterized in that the buffer hopper and feeder hopper are configured to maintain an inert atmosphere by supplying nitrogen (N₂) gas. Claim 5 A high-barrier packaging device for UO₂ powder according to claim 4, characterized in that the first packing part is configured to perform primary sealing by a heat sealing method after filling the metered UO₂ powder into the first pouch. Claim 6 A high-barrier packaging device for UO₂ powder according to claim 5, characterized in that the first packing part and the second packing part are both installed within a sealed room, and the sealed room is maintained in a negative pressure state so as to prevent external scattering of UO₂ powder. Claim 7 delete

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