Double-channel sealing structure for lead-bismuth fast reactor pressure vessel and test method of double-channel sealing structure

Abstract

The invention belongs to the technical field of reactor pressure vessels of lead-bismuth fast reactors, and particularly relates to a double-sealing structure for a lead-bismuth fast reactor pressure vessel and a test method of the double-sealing structure. The sealing ring comprises an inner ring and an outer ring, the inner ring and the outer ring are located between an upper flange and a lower flange, a groove is formed in the contact face of the upper flange, and the inner ring and the outer ring are located in the groove. According to the invention, the sealing of the internal medium of the lead-bismuth fast reactor RPV can be ensured, the leakage of radioactive substances is avoided, and the normal operation of the reactor is ensured.

Description

Technical Field

[0001] This invention belongs to the field of reactor pressure vessel technology for lead-bismuth fast reactors, specifically relating to a double-sealed structure for a lead-bismuth fast reactor pressure vessel and its testing method. Background Technology

[0002] The most widely used and technologically mature reactor type is the pressurized water reactor (RPV). The design temperature of the medium inside the sealing ring of a typical RPV pressure vessel is 343°C, the design pressure is 17.23 MPa, and the design life of the sealing ring is 18 months. The RPV sealing structure typically consists of double C-rings or double O-rings.

[0003] The C-type sealing ring consists of three parts: the inner layer is an aged GH4145 spring (corresponding to the foreign brand Inconel X750), the middle layer is a solution-treated NS3102 alloy (corresponding to the foreign brand Inconel 600) with an outer layer (opening outwards), and the outer layer is pure silver (Ag) (opening outwards).

[0004] O-rings are made by bending GH4169 (corresponding to the foreign brand Inconel 718) thin-walled steel pipe into a circle, welding the joints together to form a closed ring, and then plating the outer surface of the closed ring with silver.

[0005] When developing pressurized water reactor RPV sealing rings (C-rings or O-rings), scaled-down test pieces (e.g., test pieces with a diameter of Φ318mm) are typically used to conduct room temperature compression rebound tests (also called sealing characteristic curve tests), room temperature leakage rate tests (or helium leak detection tests), room temperature water pressure tests, and hot and cold cycle tests.

[0006] Sealing rings are also required between the top cover and the shell of a lead-bismuth fast reactor (RPV), or between the large top cover and the small top cover. Unlike pressurized water reactors (PWRs), the RPV of a RPV contains a high-temperature (typically 350℃~500℃) liquid lead-bismuth alloy. Above the liquid lead-bismuth alloy is a high-temperature, low-pressure inert covering gas, which may contain lead-bismuth vapor. Furthermore, the sealing rings are designed for a lifespan of several years or even decades. Since the pure silver (Ag) on ​​the surface of the PWR sealing ring is not resistant to lead-bismuth vapor corrosion, and the existing testing methods for PWR sealing rings are insufficient to meet the higher requirements of RPVs for high-temperature resistance, stress relaxation resistance, and cyclic deformation resistance in RPVs, a new dual-seal structure needs to be designed specifically for the high-temperature gas sealing environment of RPVs in RPVs. A reasonable testing method should also be proposed to verify the sealing ring performance, especially its high-temperature performance. Summary of the Invention

[0007] The technical problem solved by this invention is to provide a double-sealing structure and its testing method for a pressure vessel of a lead-bismuth fast reactor (RPV), which can ensure the sealing of the internal medium of the RPV, prevent the leakage of radioactive materials, and ensure the normal operation of the reactor.

[0008] The technical solution adopted in this invention is as follows:

[0009] A double-sealing structure for a pressure vessel for a lead-bismuth fast reactor includes an inner ring and an outer ring, which are located between an upper flange and a lower flange. The upper flange has a groove on its contact surface, and the inner and outer rings are located within the groove.

[0010] The inner ring and the outer ring have the same structure, both including a covering layer, a middle layer and an inner layer, which are nested together in sequence.

[0011] The inner ring's cladding layer is a C-shaped structure formed from Cu or Pt strip, the middle layer of the inner ring is a C-shaped alloy cladding formed from GH4169 strip, and the inner layer of the inner ring is a metal spring or metal rubber wound from GH4169 wire.

[0012] The outer ring's cladding layer is a C-shaped structure formed from Ag strip, and the rest of the structure is the same as the inner ring 3.

[0013] The opening directions of the covering layer and the intermediate layer are consistent, and the opening angles are θ1 and θ2, respectively. θ1 and θ2 are controlled within the range of 20° to 60°, and θ1 is greater than θ2.

[0014] The surface roughness Ra of the coating layer and intermediate layer materials is ≤0.8μm, and the outer surface of the coating layer should be polished circumferentially along the sealing ring.

[0015] A test method for a sealing structure includes the following steps:

[0016] Step 1: Determine the scaled-down dimensions of the test specimen;

[0017] Step 2: Conduct compression rebound tests on the test specimens at room temperature and design temperature to obtain the compression line load under different compression amounts;

[0018] Step 3: Conduct cyclic compression and rebound tests on the test piece at the design temperature. The number of cycles should be no less than the number of deformations within the service life of the sealing ring. Record the compression and rebound curve, the corresponding compression amount and compression line load for each test, and plot the curves of total rebound amount, effective rebound amount and compression line load as a function of the number of cycles.

[0019] Step 4: Conduct a room temperature hydrostatic test on the double-ring test specimen. The hydrostatic test pressure shall not be less than 1.25 times the design pressure, and the pressure holding time shall not be less than 30 minutes. The water quality shall be deionized water. A leak detection hole shall be set between the inner and outer rings to detect whether there is a leak in the inner ring.

[0020] Step 5: Conduct a pneumatic pressure test on the scaled-down test piece of the double-track test at the design temperature and design pressure. The pressure holding time of the pneumatic pressure test shall not be less than 30 minutes. The gas medium is helium. A leak detection hole shall be set between the inner and outer rings to check whether the leakage rate of the inner ring meets the requirements.

[0021] Step 6: Conduct a hot and cold cycle test on the dual-track scaled-down test specimen using helium as the test medium. Specify the maximum temperature during heating, the minimum temperature during cooling, the heating rate, the cooling rate, the maximum test pressure, the holding time, and the number of cycles as required. The number of cycles should be no less than the number of hot and cold cycles the reactor undergoes during the lifespan of the sealing ring. A leak detection hole is installed between the inner and outer rings to check whether the leakage rate of the inner ring meets the requirements.

[0022] Step 7: Conduct a life assessment test on the test piece from step one.

[0023] The beneficial effects of this invention are:

[0024] 1. The present invention provides a double-sealing structure for a pressure vessel of a lead-bismuth fast reactor. The inner ring can seal the lead-bismuth vapor and most of the inert gas inside the lead-bismuth fast reactor, and the outer ring can further seal the inert gas. At the same time, it can isolate the air outside and prevent the inner ring coating layer from being oxidized. The leakage rate per unit circumference of the sealing ring is ≤1.0×10-6Pa·m3 / s.

[0025] 2. The present invention provides a double-sealing structure for a pressure vessel of a lead-bismuth fast reactor, wherein the opening angle of the cladding layer is greater than that of the intermediate layer, which can prevent the cladding layer from being cut off by the intermediate layer during the use of the sealing ring.

[0026] 3. The present invention provides a double-sealing structure for a pressure vessel of a lead-bismuth fast reactor, wherein the effective rebound amount of the sealing ring at room temperature is not less than 0.20 mm and the effective rebound amount at high temperature is not less than 0.15 mm, which can meet the flange separation requirements.

[0027] 4. The present invention provides a test method for a double-sealed structure for a lead-bismuth fast reactor pressure vessel, which provides compression and rebound characteristics at room temperature and design temperature, allowing designers to further begin sealing analysis and structural design.

[0028] 5. The present invention provides a test method for a double-seal structure for a lead-bismuth fast reactor pressure vessel, which verifies the sealing performance of the sealing ring under cyclic compression and springback deformation, alternating hot and cold cycles and long-term high-temperature service, providing technical support and data reference for engineering design. Attached Figure Description

[0029] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in describing the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments recorded in the present invention. Those skilled in the art can derive other drawings from the following drawings without any creative effort.

[0030] Figure 1 A schematic diagram of a double-seal structure for a pressure vessel used in a lead-bismuth fast reactor provided by the present invention;

[0031] Figure 2 This is a schematic diagram of a C-type sealing ring structure;

[0032] Figure 3 This is a schematic diagram of the coating layer structure;

[0033] Figure 4 This is a schematic diagram of the intermediate layer structure;

[0034] Figure 5 This is a schematic diagram of the inner structure;

[0035] Figure 6 This is a schematic diagram of the sealing characteristic curve;

[0036] Figure 7 The solubility of different elements in lead-bismuth alloy at 800K;

[0037] Wherein: 1-upper flange; 2-lower flange; 3-inner ring; 4-outer ring; 5-cladding layer; 6-intermediate layer; 7-inner layer. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0039] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., refer to the orientation or positional relationship shown in the accompanying drawings, and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0040] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or a connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] like Figure 1-5 As shown, the present invention provides a double-sealing structure for a lead-bismuth fast reactor pressure vessel, comprising an inner ring 3 and an outer ring 4, wherein the inner ring 3 and the outer ring 4 are located between an upper flange 1 and a lower flange 2, the upper flange 1 having a groove on the contact surface, and the inner ring 3 and the outer ring 4 being located within the groove.

[0042] The inner ring 3 has the same structure as the outer ring 4, both including a covering layer 5, an intermediate layer 6, and an inner layer 7. The covering layer 5, the intermediate layer 6, and the inner layer 7 are sequentially fitted together. The covering layer 5 of the inner ring 3 is a C-shaped structure formed from pure copper (Cu) or pure platinum (Pt) strip. The intermediate layer 6 of the inner ring 3 is a C-shaped alloy cladding formed from GH4169 strip. The inner layer 7 of the inner ring 3 is a metal spring or metal rubber wound from GH4169 wire.

[0043] The outer ring 4 has a cladding layer 5 that is a C-shaped structure formed from pure silver (Ag) strip, and the rest of the structure is the same as the inner ring 3.

[0044] like Figure 7 As shown, among the soft metals commonly used for sealing, Ag, Au, Ni, Cu, and Pt, the solubility of Ag, Au, and Ni in lead-bismuth alloys is about 1 to 2 orders of magnitude higher than that of Cu and Pt. Considering the possible presence of lead-bismuth vapor in the cover gas of a lead-bismuth fast reactor, Cu or Pt is selected as the surface soft metal material for the RPV sealing ring.

[0045] The opening directions of the covering layer 5 and the intermediate layer 6 are consistent, and the opening angles are θ1 and θ2, respectively. θ1 and θ2 are controlled within the range of 20° to 60°, and θ1 is greater than θ2.

[0046] The GH4169 material in the intermediate layer 6 and the inner layer 7 are both in an aged state.

[0047] The surface roughness Ra of the materials of the covering layer 5 and the intermediate layer 6 is ≤0.8μm, and pits, indentations or mechanical damage are not allowed. The outer surface of the covering layer 5 should be polished circumferentially along the sealing ring.

[0048] Each of the cladding layer 5 and the intermediate layer 6 is allowed to have only one weld joint; the thickness of the weld joint of the cladding layer 5 and the intermediate layer 6 should be ground to within ±0.02mm of the initial thickness of the base material.

[0049] The tensile strength Rm and elongation A% of the welded joint of the cladding layer 5 should be between 90% and 110% of the measured values ​​of the base material; the tensile strength Rm, yield strength Rp0.2, and elongation A% of the welded joint of the intermediate layer 6 should be between 90% and 110% of the measured values ​​of the base material.

[0050] When the inner layer 7 uses a metal spring, the diameter of the spring wire needs to be adjusted according to the required compressive load of the sealing ring; when the inner layer 7 uses metal rubber, the wire diameter and the tightness of the winding need to be adjusted according to the required compressive load of the sealing ring.

[0051] The present invention provides a test method for a sealing structure, comprising the following steps:

[0052] Step 1: Determine the scaled-down dimensions of the test specimen.

[0053] Provide the above-mentioned test piece, ensuring that the cross-sectional dimensions of the test piece are completely consistent with the prototype sealing ring;

[0054] Based on the diameter of the prototype sealing ring, the diameter of the test piece is appropriately scaled down;

[0055] That is, simulation calculations are carried out using a sealing ring with a smaller diameter. Under the same nominal compression, when the compression line load (the line load refers to the ratio of the total compression load to the circumference of the sealing ring, in N / mm) of the smaller diameter scaled-up sealing ring deviates from the compression line load of the larger diameter prototype sealing ring by less than 10%, the deformation characteristics of the smaller diameter scaled-up sealing ring are considered to be equivalent to those of the larger diameter prototype sealing ring. In other words, the former can be used to represent the latter for subsequent tests.

[0056] Step 2: Conduct compression rebound tests (sealing characteristic curve tests) on the test specimens at room temperature and design temperature to obtain the compression line load under different compression amounts, such as... Figure 6 As shown. The critical point of seal failure needs to be determined through a helium leak detection test.

[0057] Step 3: Conduct a cyclic compression and springback test at the design temperature on the test piece (i.e., repeat the above compression and springback test). The number of cycles should not be less than the number of deformations within the service life of the sealing ring. Record the compression and springback curve, the corresponding compression amount and compression line load for each test, and then plot the curves of total springback, effective springback and compression line load as a function of the number of cycles.

[0058] Step 4: Conduct a room temperature hydrostatic test on the double-ring test specimen. The hydrostatic test pressure shall not be less than 1.25 times the design pressure, and the pressure holding time shall not be less than 30 minutes. The water quality shall be deionized water. A leak detection hole shall be set between the inner and outer rings to detect whether there is a leak in the inner ring.

[0059] Step 5: Conduct a pneumatic pressure test on the scaled-down test piece of the double-track test at the design temperature and design pressure. The pressure holding time of the pneumatic pressure test shall not be less than 30 minutes. The gas medium is helium. A leak detection hole shall be set between the inner and outer rings to check whether the leakage rate of the inner ring meets the requirements.

[0060] Step 6: Conduct a hot and cold cycle test on the dual-track scaled-down test specimen, using helium as the test medium. Specify the maximum temperature during heating, the minimum temperature during cooling, the heating rate, the cooling rate, the maximum test pressure, the holding time, and the number of cycles, according to specific requirements. The number of cycles should not be less than the number of hot and cold cycles the reactor will undergo during the lifespan of the sealing ring. A leak detection hole is installed between the inner and outer rings to check whether the leakage rate of the inner ring meets the requirements.

[0061] Step 7: Conduct a life assessment test on the test piece of the first test, that is, simulate the long-term service state of the sealing ring under the design temperature and nominal compression, measure the compression line load of the sealing ring at regular intervals (at least four time points), and finally fit the curve of the compression line load changing with time, and extrapolate it to the compression line load at the design life.

[0062] Example 1

[0063] This invention provides a double-seal structure for a pressure vessel used in a lead-bismuth fast reactor.

[0064] The cladding layer 5 is made of pure copper or pure platinum. The inner diameter D1 is the inner diameter D of the C-type sealing ring, which is determined according to the flange size and is usually in the range of Φ1000mm~Φ6000mm. The outer diameter d1 is the outer diameter d of the C-type sealing ring, d1=Φ12.7mm. The thickness t1=0.7mm. The opening angle θ1=50° and the opening faces outward. The surface roughness Ra of the material is ≤0.8μm, and the outer surface is polished along the circumference of the sealing ring. No pits, indentations or mechanical damage are allowed.

[0065] The intermediate layer 6 is made of GH4169, with an inner diameter D2 determined based on the dimensions of the cladding layer 5 and the inner layer 7; the outer diameter of the cross-section d2 = Φ11.3 mm; the thickness t2 = 0.8 mm; the opening angle θ2 = 40°, and the opening faces outwards; the surface roughness Ra ≤ 0.8 μm, and pits, indentations, or mechanical damage are not permitted. The GH4169 material of the intermediate layer 6 is ultimately in an aged state.

[0066] The inner layer 7 is made of GH4169, which can be a metal-rubber made of wire with a diameter of 0.3mm or a spring made of wire with a diameter of 1mm; the inner diameter D3 is determined according to the dimensions of the covering layer 5 and the intermediate layer 6; the outer diameter of the cross section d3 = 9.7mm. The GH4169 material of the inner layer 7 is ultimately in an aged state.

[0067] The specific test method for the above-mentioned sealing structure is as follows:

[0068] Step 1: Determine the scaled-down dimensions of the test piece. First, the cross-sectional dimensions of the test piece are identical to those of the prototype sealing ring. Through simulation calculations, the compression line load deviation between the prototype sealing ring (diameter Φ2000mm) and the scaled-down sealing ring (diameter Φ318mm) under a compression of 1.2mm is 6%. Therefore, it is considered that the deformation characteristics of the scaled-down sealing ring are comparable to those of the prototype sealing ring, meaning the former can be used to represent the latter in subsequent tests.

[0069] Step 2: Conduct compression rebound tests (sealing characteristic curve tests) on the test specimens at room temperature and design temperature to obtain the compression line load under different compression amounts, such as... Figure 6 As shown. The critical point of seal failure needs to be determined through a helium leak detection test.

[0070] Step 3: Conduct a cyclic compression and springback test at the design temperature on the test piece (i.e., repeat the above compression and springback test), with 200 cycles. Record the compression and springback curve, corresponding compression amount, and compression line load for each cycle, and then plot the curves of total springback, effective springback, and compression line load as a function of the number of cycles.

[0071] Step 4: Conduct a room temperature hydrostatic test on the double-ring test specimen. The test pressure is 30 MPa, and the pressure holding time is not less than 30 minutes. The water quality is deionized water. A leak detection hole is set between the inner and outer rings to check for leaks in the inner ring.

[0072] Step 5: Conduct a pneumatic pressure test on the dual-track test piece at the design temperature and design pressure. The pressure holding time for the pneumatic pressure test shall not be less than 30 minutes, and the gas medium shall be helium. A leak detection hole shall be set between the inner and outer rings to check whether the leakage rate of the inner ring meets the requirements.

[0073] Step 6: Conduct a hot-cold cycle test on the dual-ring test piece using helium as the test medium. The number of cycles is 200. A leak detection hole is installed between the inner and outer rings to check whether the leakage rate of the inner ring meets the requirements.

[0074] Step 7: Conduct a life assessment test on the test piece. Simulate the long-term service state of the sealing ring at the design temperature and 1.2 mm compression. Measure the compression line load of the sealing ring on day 1, day 10, day 30, day 60, and day 180. Finally, fit the curve of the compression line load over time and extrapolate it to the compression line load at the design life. When the compression line load at the design life is still greater than the required line load for sealing, the design life of the sealing ring is verified.

[0075] While those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention, the embodiments should be considered illustrative and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and therefore all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0076] Furthermore, it should be understood that although the present invention is described according to embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A double-sealing structure for a pressure vessel of a lead-bismuth fast reactor, characterized in that, It includes an inner ring (3) and an outer ring (4), which are located between the upper flange (1) and the lower flange (2). The upper flange (1) has a groove on the contact surface, and the inner ring (3) and the outer ring (4) are located in the groove.

2. The double-sealing structure for a lead-bismuth fast reactor pressure vessel according to claim 1, characterized in that, The inner ring (3) has the same structure as the outer ring (4), both including a covering layer (5), a middle layer (6) and an inner layer (7), which are sequentially fitted together.

3. The double-sealing structure for a lead-bismuth fast reactor pressure vessel according to claim 2, characterized in that, The inner ring (3) has a cladding layer (5) formed from Cu or Pt strips in a C-shape, the middle layer (6) of the inner ring (3) is a C-shape alloy cladding formed from GH4169 strips, and the inner layer (7) of the inner ring (3) is a metal spring or metal rubber wound from GH4169 wire.

4. The double-sealing structure for a lead-bismuth fast reactor pressure vessel according to claim 3, characterized in that, The outer ring (4) has a covering layer (5) that is a C-shaped structure formed from Ag strip, and the rest of the structure is the same as the inner ring 3.

5. The double-sealing structure for a lead-bismuth fast reactor pressure vessel according to claim 4, characterized in that, The opening directions of the covering layer (5) and the intermediate layer (6) are consistent, and the opening angles are θ1 and θ2 respectively. θ1 and θ2 are controlled within the range of 20° to 60°, and θ1 is greater than θ2.

6. The double-sealing structure for a lead-bismuth fast reactor pressure vessel according to claim 5, characterized in that, The surface roughness Ra of the materials of the covering layer (5) and the intermediate layer (6) is ≤0.8μm, and the outer surface of the covering layer (5) should be polished circumferentially along the sealing ring.

7. A test method for a sealing structure, characterized in that, Includes the following steps: Step 1: Determine the scaled-down dimensions of the test specimen; Step 2: Conduct compression rebound tests on the test specimens at room temperature and design temperature to obtain the compression line load under different compression amounts; Step 3: Conduct cyclic compression and rebound tests on the test piece at the design temperature. The number of cycles should be no less than the number of deformations within the service life of the sealing ring. Record the compression and rebound curve, the corresponding compression amount and compression line load for each test, and plot the curves of total rebound amount, effective rebound amount and compression line load as a function of the number of cycles. Step 4: Conduct a room temperature hydrostatic test on the double-ring test specimen. The hydrostatic test pressure shall not be less than 1.25 times the design pressure, and the pressure holding time shall not be less than 30 minutes. The water quality shall be deionized water. A leak detection hole shall be set between the inner and outer rings to detect whether there is a leak in the inner ring. Step 5: Conduct a pneumatic pressure test on the scaled-down test piece of the double-track test at the design temperature and design pressure. The pressure holding time of the pneumatic pressure test shall not be less than 30 minutes. The gas medium is helium. A leak detection hole shall be set between the inner and outer rings to check whether the leakage rate of the inner ring meets the requirements. Step 6: Conduct a hot and cold cycle test on the dual-track scaled-down test specimen using helium as the test medium. Specify the maximum temperature during heating, the minimum temperature during cooling, the heating rate, the cooling rate, the maximum test pressure, the holding time, and the number of cycles as required. The number of cycles should be no less than the number of hot and cold cycles the reactor undergoes during the lifespan of the sealing ring. A leak detection hole is installed between the inner and outer rings to check whether the leakage rate of the inner ring meets the requirements. Step 7: Conduct a life assessment test on the test piece from step 1.

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