CN113433058A - Test device and method for simulating metal corrosion in humidifying process of high-compaction bentonite - Google Patents
Test device and method for simulating metal corrosion in humidifying process of high-compaction bentonite Download PDFInfo
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- 239000000440 bentonite Substances 0.000 title claims abstract description 160
- 229910000278 bentonite Inorganic materials 0.000 title claims abstract description 160
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 title claims abstract description 160
- 238000005056 compaction Methods 0.000 title claims abstract description 127
- 230000007797 corrosion Effects 0.000 title claims abstract description 55
- 238000005260 corrosion Methods 0.000 title claims abstract description 55
- 238000000034 method Methods 0.000 title claims abstract description 55
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 31
- 239000002184 metal Substances 0.000 title claims abstract description 31
- 238000012360 testing method Methods 0.000 title claims abstract description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 28
- 238000004088 simulation Methods 0.000 claims abstract description 14
- 238000000840 electrochemical analysis Methods 0.000 claims abstract description 11
- 239000010935 stainless steel Substances 0.000 claims description 41
- 229910001220 stainless steel Inorganic materials 0.000 claims description 41
- 238000005520 cutting process Methods 0.000 claims description 30
- 239000004575 stone Substances 0.000 claims description 11
- 238000001035 drying Methods 0.000 claims description 8
- 238000001764 infiltration Methods 0.000 claims description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 8
- 238000010998 test method Methods 0.000 claims description 8
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 6
- 238000005303 weighing Methods 0.000 claims description 6
- 229910021607 Silver chloride Inorganic materials 0.000 claims description 5
- 239000008367 deionised water Substances 0.000 claims description 5
- 229910021641 deionized water Inorganic materials 0.000 claims description 5
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims description 5
- 238000009736 wetting Methods 0.000 claims description 5
- 229910052697 platinum Inorganic materials 0.000 claims description 4
- 239000003153 chemical reaction reagent Substances 0.000 claims description 3
- 229910052564 epsomite Inorganic materials 0.000 claims description 3
- 238000001914 filtration Methods 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 239000011780 sodium chloride Substances 0.000 claims description 3
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Inorganic materials [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims description 3
- 238000003860 storage Methods 0.000 claims description 3
- 238000005485 electric heating Methods 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 22
- 238000009375 geological disposal Methods 0.000 abstract description 11
- 239000002927 high level radioactive waste Substances 0.000 abstract description 10
- 239000003673 groundwater Substances 0.000 abstract description 7
- 238000011065 in-situ storage Methods 0.000 abstract description 7
- 238000012544 monitoring process Methods 0.000 abstract description 3
- 229910003322 NiCu Inorganic materials 0.000 description 7
- 238000011160 research Methods 0.000 description 5
- 239000002699 waste material Substances 0.000 description 4
- 229910000851 Alloy steel Inorganic materials 0.000 description 3
- 241000282414 Homo sapiens Species 0.000 description 3
- 230000008595 infiltration Effects 0.000 description 3
- 238000011282 treatment Methods 0.000 description 3
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- 229910000831 Steel Inorganic materials 0.000 description 2
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- 239000000956 alloy Substances 0.000 description 2
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- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
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- 230000005518 electrochemistry Effects 0.000 description 1
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- 238000004519 manufacturing process Methods 0.000 description 1
- 238000011369 optimal treatment Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
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- G01N17/006—Investigating resistance of materials to the weather, to corrosion, or to light of metals
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The invention belongs to the field of corrosion electrochemical tests, and particularly relates to a test device and a method for simulating metal corrosion in a humidifying process of high-compaction bentonite. The test device comprises a bentonite compaction die, a constant volume expansion-permeation electrolytic cell device and an electrochemical workstation, wherein the constant volume expansion-permeation electrolytic cell device is provided with a high-compaction bentonite bearing cabin, a three-electrode system, a high-compaction bentonite block and a cuboid balance sheet. Firstly, burying a three-electrode system into a reserved position of a high-compaction bentonite block, and filling the high-compaction bentonite block into a constant volume-expansion permeation electrolytic cell device. Subsequently, groundwater simulation solution was injected and electrochemical in situ monitoring was performed using an electrochemical workstation. The method provided by the invention truly and accurately simulates the corrosion environment of the high-level radioactive waste deep geological disposal buffer material, namely bentonite, in the process of being soaked by the underground water simulation solution, and is used for researching the corrosion evolution behavior of the high-level radioactive waste deep geological disposal container candidate material in the process of simulating the high-compaction bentonite humidification.
Description
Technical Field
The invention belongs to the field of corrosion electrochemical test, and particularly relates to a test device and a method for simulating metal corrosion in a high-compaction bentonite humidifying process, which are suitable for researching the corrosion behavior of a candidate material of a high-level radioactive waste geological disposal container in the process of simulating the high-compaction bentonite humidifying process of a buffer material.
Background
The development and utilization of nuclear energy create great benefits for human beings, and simultaneously, a large amount of nuclear waste is inevitably generated. If these nuclear wastes (especially high level nuclear wastes) cannot be disposed of with reasonable safety, the nuclear radiation they produce will seriously jeopardize the human living environment. At present, high level waste disposal schemes have been proposed including deep sea, ice cap, rock fusion, space, and deep geological disposal, among others. Among them, deep geological treatment is internationally widely recognized as the optimal treatment solution. The deep geological disposal scheme is to bury the high-level nuclear waste in a deep geological layer 500-1000 m away from the earth surface by adopting a multi-barrier system, so as to be far away from the living environment of human beings. The multiple barrier system includes surrounding rock, a buffer backfill material, a metal disposal container, and a glass solidification body, wherein the metal disposal container is an important safety barrier to prevent high level waste nuclide leakage. During the treatment process of thousands of years or even thousands of years, the high-compaction bentonite can be gradually infiltrated by the underground water until the high-compaction bentonite is saturated, and at the moment, the metal treatment container is easily subjected to Cl in the underground water-、SO4 2-And HCO3 -And the like, face serious corrosion problems. Therefore, the research on the corrosion behavior of the candidate material of the disposal container in the high-compaction bentonite humidifying process is very important for accurately predicting the safe service life of the candidate material.
In recent years, a number of researchers have conducted extensive research into the corrosion behavior of disposal container candidate materials in groundwater simulation solutions and high compaction bentonite environments. Research finds that the corrosion mode and corrosion rate of candidate materials for disposal containers are closely related to the evolution of the surrounding corrosive environment, such as ionic composition, dissolved oxygen concentration, and bentonite properties in groundwater. However, during actual deep geological processing, groundwater gradually penetrates into the buffer material around the tank, high compacted bentonite, to a saturated state. In this process, aggressive ions in groundwater will also gradually pass through the highly compacted bentonite to the surface of the tank, thereby greatly affecting the corrosion pattern and corrosion rate of the candidate material for disposal of the container. Therefore, in order to further study the influence of the corrosion environment evolution in the humidifying process of the high-compaction bentonite on the corrosion evolution rule of the candidate material of the disposal container, it is necessary to carry out simulation study on the corrosion environment in the drying-humidifying-saturating process of the high-compaction bentonite and in-situ electrochemical test on the corrosion behavior of the candidate material.
Disclosure of Invention
The invention aims to solve the problems that: provides a test device and a method for simulating metal corrosion in a humidifying process of high-compaction bentonite. The device and the method can truly simulate the corrosion environment from drying to saturation of the buffer backfill material, namely the high-compaction bentonite, in the high-level radioactive waste deep geological disposal library along with the infiltration of underground water, and carry out in-situ electrochemical test on the corrosion behavior of the candidate material of the disposal container in the corrosion environment.
In order to achieve the purpose, the invention adopts the following technical scheme:
the utility model provides a test device of simulation high compaction bentonite humidification process metal corrosion, this test device includes bentonite compaction mould, constant volume expansion-infiltration electrolytic cell device and electrochemistry workstation, and constant volume expansion-infiltration electrolytic cell device is equipped with high compaction bentonite and bears cabin, three electrode system, high compaction bentonite piece, cuboid balance piece, and concrete structure is as follows:
the high-compaction bentonite bearing cabin mainly comprises a stainless steel base, a water-permeable stone, a positioning ring, a cutting ring, a sleeve ring and a round stainless steel cover with a raised head, wherein the stainless steel barrel is arranged on a cuboid balance sheet, the stainless steel base is arranged at the inner bottom of the stainless steel barrel, the water-permeable stone is arranged in a groove in the upper surface of the stainless steel base, the positioning ring is arranged on the water-permeable stone, the lower end of the cutting ring is inserted into the positioning ring, the sleeve ring is arranged at the upper end of the cutting ring, a high-compaction bentonite block is positioned in an inner cavity formed by the cutting ring and the sleeve ring, the round stainless steel cover with the raised head is covered and buckled at the top of the sleeve ring, and the round;
the high-compaction bentonite bearing cabin is clamped between a cuboid balancing piece with a central hole and a cuboid balancing piece, the cuboid balancing piece with the central hole is positioned at the top of the high-compaction bentonite bearing cabin, and the cuboid balancing piece is positioned at the bottom of the high-compaction bentonite bearing cabin;
the working electrode, the reference electrode and the counter electrode are sequentially embedded into a high-compaction bentonite block to form a three-electrode system, and a lead connected with the three-electrode system sequentially penetrates through a circular stainless steel cover with a raised head and a cuboid balance sheet with a central hole to be connected with an electrochemical workstation.
The test device for simulating metal corrosion in the high-compaction bentonite humidifying process is characterized in that the bentonite block compacting die consists of a die sleeve, a die base and a die pressure head, a cutting ring and a lantern ring are placed on the die base together in an inverted mode during use, the die sleeve is sleeved on the die base, and the die pressure head corresponds to bentonite in inner cavities of the cutting ring and the lantern ring.
The test device for simulating metal corrosion in the humidifying process of the high-compaction bentonite fixes the position of a high-compaction bentonite block taken by a cutting ring and a lantern ring in a high-compaction bearing cabin through a positioning ring.
The testing device for simulating metal corrosion in the high-compaction bentonite humidifying process is characterized in that a cuboid balancing piece with a central hole corresponds to four corners of the cuboid balancing piece, the cuboid balancing piece and the cuboid balancing piece are fixedly connected through inner hexagonal screws and nuts which are matched with each other, a raised head at the center of the top of a circular stainless steel cover with a raised head penetrates through the central hole of the cuboid balancing piece with the central hole, the raised head protrudes out of the upper surface of the cuboid balancing piece with the central hole, and the cuboid balancing piece with the central hole are used for controlling constant volume expansion in the high-compaction bentonite humidifying process.
The test device for simulating metal corrosion in the humidifying process of the high-compaction bentonite is characterized in that the electrochemical workstation is provided with an electrochemical workstation case and an electrode wire, and the electrode wire is connected with a three-electrode system.
The test device for simulating metal corrosion in the humidifying process of the high-compaction bentonite is characterized in that a working electrode is a metal electrochemical sensor, a reference electrode is an Ag/AgCl reference electrode, and a counter electrode is a platinum sheet.
A test method for simulating metal corrosion in a high-compaction bentonite humidifying process comprises the following steps:
(1) accurately weighing a required analytically pure reagent by using an analytical balance according to the components of the underground water solution, and then adding deionized water to prepare a simulated solution;
(2) filtering bentonite by using a 100-mesh filter screen, placing the sieved bentonite in an electric heating air blast drying box, drying for 6-10 hours at a constant temperature of 100-110 ℃, immediately placing the bentonite in a sealing bag, and vacuumizing for storage;
(3) calculating the mass of the required dry bentonite according to the dry density and the volume of a preset high-compaction bentonite block, and then weighing by using the analytical balance;
(4) installing a compaction mould sleeve on a compaction mould base, inversely placing a cutting ring and a lantern ring into the compaction mould sleeve of the bentonite block compaction mould, then placing the weighed dry bentonite, and compacting by using a compaction mould pressure head to obtain a high-compaction bentonite block;
(5) sequentially embedding a working electrode, a reference electrode and a counter electrode into the high-compaction bentonite block to form a three-electrode system;
(6) placing the high-compaction bentonite block provided with the three-electrode system in a high-compaction bentonite bearing cabin, and sequentially passing a lead connected with the three-electrode system through a round stainless steel cover with a raised head and a cuboid balance sheet with a central hole;
(7) four inner hexagonal screws respectively penetrate: the bearing cabin is characterized by comprising round holes at four corners of a cuboid balance sheet positioned at the bottom of the high-compaction bentonite bearing cabin, and round holes at four corners of the cuboid balance sheet with a central hole positioned at the top of the high-compaction bentonite bearing cabin, wherein a rotary nut and a hexagonal screw are connected and fixed with the bearing cabin of the high-compaction bentonite through threads;
(8) and a lead of the three-electrode system is connected with an electrochemical workstation, and underground water simulation solution is injected into the stainless steel sleeve to carry out an electrochemical test.
The test method for simulating metal corrosion in the humidifying process of the high-compaction bentonite comprises the following simulated solution components: CaCl2，0.5792mg/L；MgSO4·7H2O，0.5716mg/L；Na2SO4，1.5777mg/L；NaHCO3，0.1384mg/L；NaNO30.0372 mg/L; KCl, 0.0382 mg/L; NaCl, 1.4876 mg/L; deionized water and the balance.
The simulated high compactionA test method for metal corrosion in a bentonite humidifying process is to prepare a bentonite block with a dry density of 1.60g/cm according to corrosion test conditions and sizes of a bentonite block compacting die, a cutting ring and a lantern ring3The high compacted bentonite cake of (a).
The design idea of the invention is as follows:
in order to simulate the humidifying process from drying to saturation of a high radioactive waste deep geological buffer material, namely high compaction bentonite along with groundwater infiltration and research the corrosion evolution law of a candidate material of a disposal container in the environment, the invention designs a constant volume expansion-infiltration electrolytic cell device, a working electrode, a reference electrode and a counter electrode are sequentially embedded into a high compaction bentonite tablet and are connected with an external electrochemical workstation through a lead, and after an underground water simulation solution is injected, the in-situ electrochemical test of the candidate material of the disposal container in the humidifying process of the high compaction bentonite is realized.
The invention has the advantages and positive effects that:
1. the test device provided by the invention is simple to build, the operation method is simple, the obtained experimental data is reliable, and the repeatability is good.
2. The invention simulates the evolution of the corrosive environment in the humidifying process of the high-compaction bentonite more truly and accurately according to the characteristics of the chemical composition of underground water.
3. The invention simulates the corrosion environment of the humidification process of the high-compaction bentonite by naturally permeating the underground water into the high-compaction bentonite.
4. The test device and the test method can realize the in-situ electrochemical test of the candidate material of the high-level radioactive waste geological disposal container in the corrosive environment in the humidifying process of the high-pressure compacted bentonite.
Drawings
Figure 1 is a schematic view of a bentonite block compaction tool. In the figure, 1, a compaction tool sleeve, 2, a compaction tool base, 3 and a compaction tool ram.
FIG. 2 is a schematic view of a constant volume expansion-permeation cell unit. In the figure, 4, a nut, 5, a cuboid balance sheet with a central hole, 6, a stainless steel cylinder, 7, an inner hexagonal screw, 8, a simulation solution, 9, a water seepage stone, 10, a cuboid balance sheet, 11, a stainless steel base, 12, a positioning ring, 13, a cutting ring, 14, a high-compaction bentonite block, 15, a lantern ring, 16, a round stainless steel cover with a raised head, 17, a reference electrode, 18, a working electrode, 19 and a counter electrode.
Figure 3 is a schematic diagram of an electrochemical workstation. In the figure, 20, electrode wires, 21, electrochemical workstation chassis.
FIG. 4 is a graph showing the evolution of the open circuit potential of NiCu low alloy with time during the humidification of high compacted bentonite. In the figure, the abscissa Time represents Time (day) and the ordinate E represents open circuit potential (V vs. Ag/AgCl).
FIG. 5 is the evolution curve of the electrochemical impedance modulus-frequency spectrogram of NiCu low alloy steel with time during the humidification process of high compaction bentonite. In the figure, the abscissa Frequency represents the Frequency (Hz), and the ordinate | Z | represents the electrochemical impedance mode value (ohm cm)2)。
The specific implementation mode is as follows:
in the specific implementation process, the test device for simulating metal corrosion in the high-compaction bentonite humidification process comprises a bentonite compaction die, a filter sieve, an electrothermal blowing drying box, a weighing balance, a cutting ring, a constant-volume expansion-permeation electrolytic cell device, an electrochemical workstation and the like. The test method of the device is as follows: firstly, the bentonite is filtered by a 100-mesh filter sieve, dried for 8 hours at a constant temperature of 105 ℃ and then used for preparing high-compaction bentonite blocks. Embedding a metal electrochemical sensor, a platinum sheet and an Ag/AgCl reference electrode into a reserved position of the high-compaction bentonite block, loading the high-compaction bentonite block into a constant-volume expansion infiltration electrolytic cell device, and fixing a balance clamping sheet to ensure that the volume of the high-compaction bentonite block is not changed when the high-compaction bentonite block absorbs water and expands. Subsequently, the prepared groundwater simulation solution was injected into the electrolyzer unit and electrochemical in situ monitoring was performed using an electrochemical workstation. The method provided by the invention truly and accurately simulates the corrosion environment of the high-level radioactive waste deep geological disposal buffer material, namely bentonite, in the process of being soaked by the underground water simulation solution, and is used for researching the corrosion evolution behavior of the high-level radioactive waste deep geological disposal container candidate material in the process of simulating the high-compaction bentonite humidification.
As shown in fig. 1, the bentonite block compacting mould consists of a mould sleeve 1, a mould base 2 and a mould press head 3, wherein a cutting ring 13 and a lantern ring 15 are placed on the mould base 2 in an inverted mode, the mould sleeve 1 is sleeved on the mould base 2, bentonite with a certain mass is added into the mould sleeve 1, and the mould press head 3 is utilized to manufacture a high-compaction bentonite block 14.
As shown in fig. 2, the constant volume expansion-permeation electrolytic cell device mainly comprises a high-compaction bentonite bearing cabin, a three-electrode system, high-compaction bentonite blocks, cuboid balance pieces and the like, and has the following specific structure:
the high compaction bentonite bearing cabin mainly comprises a stainless steel base 11, a water seepage stone 9, a positioning ring 12, a cutting ring 13, a sleeve ring 15 and a circular stainless steel cover 16 with a raised head, wherein the stainless steel barrel 6 is arranged on a cuboid balance sheet 10, the stainless steel base 11 is arranged at the inner bottom of the stainless steel barrel, the water seepage stone 9 is arranged in a groove on the upper surface of the stainless steel base 11, the positioning ring 12 is arranged on the water seepage stone 9, the cutting ring 13 is an annular stainless steel blade, the lower end of the cutting ring 13 is inserted into the positioning ring 12, a high compaction bentonite block 14 taken by the cutting ring 13 and the sleeve ring 15 can be fixed at the position of the high compaction bearing cabin through the positioning ring 12, the sleeve ring 15 is arranged at the upper end of the cutting ring 13, the high compaction bentonite block 14 is positioned in an inner cavity formed by the cutting ring 13 and the sleeve ring 15, the circular stainless steel cover 16 with the raised head is covered and buckled at the top of the sleeve ring 15, and the circular stainless steel cover 16 with the raised head is sealed.
The high compaction bentonite bearing cabin is clamped between a cuboid balance sheet 5 with a central hole and a cuboid balance sheet 10, the cuboid balance sheet 5 with the central hole is positioned at the top of the high compaction bentonite bearing cabin, the cuboid balance sheet 10 is positioned at the bottom of the high compaction bentonite bearing cabin, the cuboid balance sheet 5 with the central hole corresponds to the four corners of the cuboid balance sheet 10, and is fixedly connected through a matched inner hexagonal screw 7 and a nut 4, a raised head at the center of the top of a round stainless steel cover 16 with the raised head passes through a central hole of a cuboid balancing piece 5 with a central hole and protrudes out of the upper surface of the cuboid balancing piece 5 with the central hole, used for preventing the cuboid balancing sheet 5 with a central hole from sliding caused by the expansive force generated in the humidifying process of the highly compacted bentonite, the constant volume expansion of the high-compaction bentonite in the humidifying process is controlled by a cuboid balance sheet 5 with a central hole and a cuboid balance sheet 10.
A working electrode 18, a reference electrode 17 and a counter electrode 19 are sequentially embedded into a high-compaction bentonite block 14 by tools such as an art designer knife and an electric drill to form a three-electrode system, and a lead connected with the three-electrode system sequentially penetrates through a round stainless steel cover 16 with a raised head and a cuboid balance sheet 5 with a central hole. The simulated solution 8 of the underground water is poured into the stainless steel cylinder 6 to be naturally permeated, and water can be permeated from the stainless steel base 11 to the high-compaction bentonite block 14 from the side surface through the gap at the joint of the cutting ring 13 and the lantern ring 15 by virtue of the water seepage stone 9 for simulating the humidification process of the high-compaction bentonite. Meanwhile, an electrochemical workstation is started to carry out electrochemical test.
As shown in fig. 3, the electrochemical workstation mainly comprises an electrochemical workstation chassis 21 and an electrode wire 20, one end of the electrode wire 20 is connected to the three-electrode system, and the other end of the electrode wire 20 is connected to the electrochemical workstation chassis 21, so as to start the electrochemical workstation for performing an electrochemical test.
The apparatus and method of the present invention are further described below in conjunction with the following specific embodiments, the preferred embodiments of which are detailed below:
example 1
As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4 and FIG. 5, the electrochemical test for simulating the corrosion of NiCu low alloy steel in the wetting process of high-compaction bentonite in the embodiment includes the following specific experimental steps:
(1) according to the components of the underground water solution, accurately weighing the required analytically pure reagent by using an analytical balance, wherein the specific preparation components are as follows in sequence: CaCl2，0.5792mg/L；MgSO4·7H2O，0.5716mg/L；Na2SO4，1.5777mg/L；NaHCO3，0.1384mg/L；NaNO30.0372 mg/L; KCl, 0.0382 mg/L; NaCl, 1.4876 mg/L. Deionized water was then added to make up the simulated solution.
(2) Filtering bentonite with 100 mesh filter sieve, drying the sieved bentonite in an electrothermal blowing dry box at a constant temperature of 105 ℃ for 8 hours, immediately placing the bentonite in a sealing bag, and vacuumizing for storage.
(3) According to the corrosion test conditions,The size of the bentonite block compacting mould, the cutting ring 13 and the lantern ring 15 is to prepare the bentonite block compacting mould with the diameter of 6.18cm, the height of 3.5cm and the dry density of 1.60g/cm3The mass of the dry bentonite required is calculated to be 167.9g and then weighed using the analytical balance.
(4) Installing a compaction mould sleeve 1 on a compaction mould base 2, inversely placing a cutting ring 13 and a lantern ring 15 into the compaction mould sleeve 1 of the bentonite block compaction mould, then loading weighed dry bentonite, and compacting by using a compaction mould pressure head 3 to obtain a high-compaction bentonite block 14.
(5) A working electrode 18 (a metal electrochemical sensor), an Ag/AgCl reference electrode 17 and a counter electrode 19 (a platinum sheet) are sequentially embedded in the high-compaction bentonite block 14 by using tools such as an art designer knife, an electric drill and the like to form a three-electrode system.
(6) The high-compaction bentonite block 14 provided with the three-electrode system is placed in a high-compaction bentonite bearing cabin, and a lead connected with the three-electrode system sequentially passes through a round stainless steel cover 16 with a raised head and a cuboid balance sheet 5 with a central hole.
(7) Four socket head cap screws 7 respectively pass through: the rectangular balance piece 10 four-corner round hole located at the bottom of the high-compaction bentonite bearing cabin and the rectangular balance piece 5 four-corner round hole located at the top of the high-compaction bentonite bearing cabin and provided with a center hole are screwed up by the adjustable wrench after the rotary nut 4 passes through the threads of the hexagonal screw 7 to fix the bearing cabin of the high-compaction bentonite.
(8) The lead of the three-electrode system is connected with an electrochemical workstation, underground water simulation solution 8 is injected into the stainless steel sleeve 6, then open-circuit potential in-situ monitoring is carried out, and electrochemical impedance test is carried out at intervals.
As shown in fig. 4, it can be seen from the evolution curve of the open-circuit potential of the NiCu low alloy with time in the process of humidifying the high compaction bentonite that the open-circuit potential in the initial stage of the experiment vibrates violently, which indicates that the moisture content in the bentonite on the surface of the electrode is low and the electrode is in an incomplete conduction state. With the time being prolonged, the simulation solution continuously permeates to the surface of the electrode, and the open-circuit potential gradually tends to be stable.
As shown in FIG. 5, it can be seen from the evolution curve of the electrochemical impedance modulus-frequency spectrogram of NiCu low alloy steel along with time in the process of high compaction bentonite humidification that the high frequency impedance and the low frequency impedance modulus of the initial stage of the experiment are both relatively high, which indicates that the bentonite medium on the surface of the electrode has relatively high resistance and the corrosion rate of the NiCu steel is relatively low. With time, the water content at the NiCu steel/bentonite interface increases, the dielectric resistance decreases, and corrosion accelerates.
The results of the above embodiments show that the invention can truly and accurately simulate the corrosion environment evolution in the humidifying process of the deep geological disposal buffer material-high compacted bentonite, and can realize the research on the corrosion behavior of the candidate material of the high-level radioactive waste deep geological disposal container in the humidifying process of the simulated high compacted bentonite.
The above embodiments are only one embodiment of the present invention, and not all embodiments. Based on the above embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without any creative effort belong to the protection scope of the present invention.
Claims (9)
1. The utility model provides a test device of simulation high compaction bentonite humidification process metal corrosion, its characterized in that, this test device includes bentonite compaction mould, permanent volume expansion-infiltration electrolytic bath device and electrochemical workstation, and permanent volume expansion-infiltration electrolytic bath device is equipped with high compaction bentonite and bears cabin, three electrode system, high compaction bentonite piece, cuboid balance piece, and concrete structure is as follows:
the high-compaction bentonite bearing cabin mainly comprises a stainless steel base, a water-permeable stone, a positioning ring, a cutting ring, a sleeve ring and a round stainless steel cover with a raised head, wherein the stainless steel barrel is arranged on a cuboid balance sheet, the stainless steel base is arranged at the inner bottom of the stainless steel barrel, the water-permeable stone is arranged in a groove in the upper surface of the stainless steel base, the positioning ring is arranged on the water-permeable stone, the lower end of the cutting ring is inserted into the positioning ring, the sleeve ring is arranged at the upper end of the cutting ring, a high-compaction bentonite block is positioned in an inner cavity formed by the cutting ring and the sleeve ring, the round stainless steel cover with the raised head is covered and buckled at the top of the sleeve ring, and the round stainless steel cover with the raised head is sealed;
the high-compaction bentonite bearing cabin is clamped between a cuboid balancing piece with a central hole and a cuboid balancing piece, the cuboid balancing piece with the central hole is positioned at the top of the high-compaction bentonite bearing cabin, and the cuboid balancing piece is positioned at the bottom of the high-compaction bentonite bearing cabin;
the working electrode, the reference electrode and the counter electrode are sequentially embedded into a high-compaction bentonite block to form a three-electrode system, and a lead connected with the three-electrode system sequentially penetrates through a circular stainless steel cover with a raised head and a cuboid balance sheet with a central hole to be connected with an electrochemical workstation.
2. The test device for simulating metal corrosion during humidification of highly compacted bentonite as recited in claim 1, wherein the bentonite block compacting die comprises a die sleeve, a die base, and a die ram, wherein the cutting ring and the sleeve ring are placed on the die base in an inverted manner during use, the die sleeve is sleeved on the die base, and the die ram corresponds to the bentonite in the inner cavity of the cutting ring and the sleeve ring.
3. The test device for simulating metal corrosion in the wetting process of highly compacted bentonite as claimed in claim 2, wherein the position of the highly compacted bentonite block taken by the cutting ring and the lantern ring in the high-compaction load-bearing chamber is fixed by a positioning ring.
4. The testing device for simulating metal corrosion in the humidification process of high-compaction bentonite according to claim 1, wherein the cuboid balancing piece with the central hole corresponds to four corners of the cuboid balancing piece and is fixedly connected through a hexagon socket screw and a nut which are matched with the cuboid balancing piece, the raised head at the center of the top of the circular stainless steel cover with the raised head penetrates through the central hole of the cuboid balancing piece with the central hole and protrudes out of the upper surface of the cuboid balancing piece with the central hole, and the constant volume expansion in the humidification process of high-compaction bentonite is controlled through the cuboid balancing piece with the central hole and the cuboid balancing piece.
5. The test rig for simulating metal corrosion during humidification of highly compacted bentonite as recited in claim 1, wherein the electrochemical workstation is provided with an electrochemical workstation housing and an electrode wire, the electrode wire being connected to a three-electrode system.
6. The test device for simulating metal corrosion in the humidification process of highly compacted bentonite as recited in claim 1, wherein the working electrode is a metal electrochemical sensor, the reference electrode is an Ag/AgCl reference electrode, and the counter electrode is a platinum sheet.
7. A test method for simulating metal corrosion during wetting of highly compacted bentonite using the apparatus of any of claims 1 to 6, comprising the steps of:
(1) accurately weighing a required analytically pure reagent by using an analytical balance according to the components of the underground water solution, and then adding deionized water to prepare a simulated solution;
(2) filtering bentonite by using a 100-mesh filter screen, placing the sieved bentonite in an electric heating air blast drying box, drying for 6-10 hours at a constant temperature of 100-110 ℃, immediately placing the bentonite in a sealing bag, and vacuumizing for storage;
(3) calculating the mass of the required dry bentonite according to the dry density and the volume of a preset high-compaction bentonite block, and then weighing by using the analytical balance;
(4) installing a compaction mould sleeve on a compaction mould base, inversely placing a cutting ring and a lantern ring into the compaction mould sleeve of the bentonite block compaction mould, then placing the weighed dry bentonite, and compacting by using a compaction mould pressure head to obtain a high-compaction bentonite block;
(5) sequentially embedding a working electrode, a reference electrode and a counter electrode into the high-compaction bentonite block to form a three-electrode system;
(6) placing the high-compaction bentonite block provided with the three-electrode system in a high-compaction bentonite bearing cabin, and sequentially passing a lead connected with the three-electrode system through a round stainless steel cover with a raised head and a cuboid balance sheet with a central hole;
(7) four inner hexagonal screws respectively penetrate: the bearing cabin is characterized by comprising round holes at four corners of a cuboid balance sheet positioned at the bottom of the high-compaction bentonite bearing cabin, and round holes at four corners of the cuboid balance sheet with a central hole positioned at the top of the high-compaction bentonite bearing cabin, wherein a rotary nut and a hexagonal screw are connected and fixed with the bearing cabin of the high-compaction bentonite through threads;
(8) and a lead of the three-electrode system is connected with an electrochemical workstation, and underground water simulation solution is injected into the stainless steel sleeve to carry out an electrochemical test.
8. The test method for simulating metal corrosion during wetting of highly compacted bentonite as claimed in claim 7, wherein the simulated solution comprises: CaCl2，0.5792mg/L；MgSO4·7H2O，0.5716mg/L；Na2SO4，1.5777mg/L；NaHCO3，0.1384mg/L；NaNO30.0372 mg/L; KCl, 0.0382 mg/L; NaCl, 1.4876 mg/L; deionized water and the balance.
9. The test method for simulating metal corrosion during wetting of highly compacted bentonite as claimed in claim 7, wherein a dry density of 1.60g/cm is prepared based on the corrosion test conditions, the dimensions of the bentonite block compacting die, the cutting ring and the collar3The high compacted bentonite cake of (a).
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| CN202110633732.4A CN113433058A (en) | 2021-06-07 | 2021-06-07 | Test device and method for simulating metal corrosion in humidifying process of high-compaction bentonite |
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