An in-situ multiple scratching electrode system for simulating boiling nitric acid in spent fuel reprocessing

Abstract

A system for in-situ multiple off-site scratching of electrodes in boiling nitric acid for simulating spent fuel reprocessing, belonging to the field of corrosion simulation experiments and scratching electrode systems for spent fuel reprocessing, includes a boiling nitric acid electrolytic cell, a working electrode clamping device, an electrolytic cell top cover, a boiling nitric acid working electrode, a boiling nitric acid reference electrode, a boiling nitric acid counter electrode, a special cylinder, a scratching motion axis, a scratching head device, a temperature control system, an electrochemical testing system, and a tail gas treatment system. Compared with the existing scratching electrode technology, the present invention can simulate the scratching-repassivation behavior on the surface of metal specimens in the boiling nitric acid environment of spent fuel reprocessing, can precisely control the scratching speed and pressure, and can independently control off-site scratching while conducting in-situ electrochemical monitoring. One installation of a specimen can conduct multiple scratching experiments.

Description

Technical Field

[0001] The invention belongs to the field of spent fuel post-processing corrosion simulation experiments and scratch electrode systems, and in particular relates to an in-situ and multiple-times-out-of-place scratching electrode system simulating spent fuel post-processing boiling nitric acid. Background Art

[0002] Spent fuel dissolvers and various evaporators are key equipment for spent fuel reprocessing. Their main materials are corrosion-resistant materials such as titanium alloys, stainless steel and zirconium alloys. In a boiling nitric acid environment with high radioactivity and high oxidizing ions, a passivation film will be formed on the surface of these materials, thereby reducing the corrosion rate of the substrate. However, when the passivation film on the surface of the material is damaged by external forces, fresh metal will be exposed. When the repassivation ability of the material is high, the fresh metal will quickly passivate to form a new passivation film, but when the degree of damage to the passivation film (depassivation ability) is significantly higher than the repassivation ability, the damaged passivation film is difficult to repair, resulting in a significant acceleration of material corrosion. Therefore, in-depth research on the repassivation kinetics of metal materials under boiling nitric acid, revealing the passivation behavior of the material, and quantitatively evaluating the repassivation ability of the material can provide theoretical guidance for the selection of key equipment for spent fuel reprocessing and the design of new corrosion-resistant materials.

[0003] To this end, researchers at home and abroad have designed devices with different mechanical principles and methods to measure the repassivation dynamics: Han Enhou et al. designed a high-temperature and high-pressure in-situ multi-pass rapid scratch electrode system to achieve three scratches at a time under high temperature and high pressure, but only one test can be carried out after installing a sample, and the load cannot be guaranteed to be consistent each time; Zhou Honghui et al. designed a thin film breaking device to obtain a fresh surface, and used the movement of a tapping rod to break the thin film deposited on the glass to expose the cross section. Although the exposure time is very short, it is only suitable for thin film materials, and special processes are required to make samples; Pyun and Lee et al. designed a friction The abrasion method is a process of removing the passivation film through mechanical friction between the sample and the friction disk. However, when the solution penetrates into the gap between the abrasive and the sample, oxidation occurs on the newly exposed surface. Due to the disorder of surface oxidation during the abrasion process, it is difficult to unify the starting point of time using mathematical methods. Sun Dongbai and others designed a fully automatic controlled abrasion device, which abrades the sample in an oxygen-free environment and immerses the abraded section into the electrolytic cell solution through cylinder movement. However, this method is not suitable for boiling nitric acid systems that are highly volatile and corrosive. Nitric acid vapor evaporates and corrodes devices such as motor grinding discs in vacuum equipment.

[0004] In summary, the main problems of existing defilming technology are: one sample can only be installed once for one experiment, which is inefficient, and the experimental load cannot be accurately displayed and controlled. And so far, there is no device that can achieve the defilming function in boiling nitric acid (strongly corrosive and highly volatile). These difficulties limit people's understanding of the true repassivation process of materials in boiling concentrated nitric acid and the testing of repassivation electrochemical parameters. Therefore, it is necessary to design a device that can abandon the above shortcomings and simply and controllably measure the repassivation performance of materials in boiling concentrated nitric acid. Summary of the invention

[0005] The purpose of the present invention is to provide an electrode system for multiple in-situ scratching in different places in a simulated spent fuel reprocessing boiling nitric acid, which solves many deficiencies of the existing methods, including unifying the starting point of the repassivation time, accurately controlling the scratching load and the scratching speed. At the same time, it can realize the function of multiple scratching in different places in boiling nitric acid, install a sample once and do multiple scratching experiments, realize scratching in different places and realize in-situ electrochemical experiments at the same time, and the scratching time interval can be controlled automatically.

[0006] In order to solve the above technical problems, the following technical solutions are adopted:

[0007] A system for simulating in-situ and multiple out-of-place scratching of an electrode by boiling nitric acid in spent fuel reprocessing, comprising a boiling nitric acid electrolytic cell, a working electrode clamping device, an electrolytic cell top cover, a boiling nitric acid working electrode, a boiling nitric acid reference electrode, a boiling nitric acid counter electrode, a special cylinder, a scratching motion axis, a scratching head device, a temperature control system, an electrochemical test system and an exhaust gas treatment system.

[0008] The bottom plate of the boiling nitric acid electrolytic cell is fixed on a base equipped with two mutually perpendicular slide rails by bolt assembly. A knob with a scale is respectively provided on the side and front of the base. The front fine-tuning knob I can control the boiling nitric acid electrolytic cell to move forward and backward on the horizontal plane, and one scale of the knob represents 1mm. The side fine-tuning knob II can control the electrolytic cell to move left and right on the horizontal plane, and one scale of the knob represents 0.01mm. The material of the boiling nitric acid electrolytic cell is polytetrafluoroethylene.

[0009] The working electrode clamping device is divided into a lower clamp fixing part and an upper working electrode fixing part. The clamp fixing part is installed on the bottom plate of the boiling nitric acid electrolytic cell through threads and fixed by bolts; the working electrode is fixed in the groove of the working electrode fixing part, the groove is added with a clamping plate, the clamping plate is added with fixing bolts, and a gasket is placed behind the working electrode to adjust the position. The gasket ensures that there is no raised step between the working electrode and the clamping plate. The working electrode is fixed on the left and right with fixed buckles to strengthen the fixation. The entire working electrode clamping device is made of polytetrafluoroethylene that is insulated and resistant to corrosion by boiling concentrated nitric acid.

[0010] The electrolytic cell top cover is installed with a boiling nitric acid working electrode seat, a boiling nitric acid counter electrode seat, a salt bridge of a boiling nitric acid reference electrode, a heating device and a temperature sensor, a condenser, and a scratching motion shaft. The electrolytic cell top cover is made of quartz glass. The electrolytic cell top cover and the boiling nitric acid electrolytic cell are locked by stud bolts and polytetrafluoroethylene-coated washers.

[0011] The copper wire of the boiling nitric acid working electrode is welded to the cylindrical part of the working electrode by laser spot welding. The cylindrical part of the working electrode is first sealed by high-temperature sintering sealing technology of a polytetrafluoroethylene hose, and then the entire structure is sealed with a polytetrafluoroethylene sleeve. The wire of the working electrode is led out from the working electrode seat, and a polytetrafluoroethylene-coated rubber plug is provided in the electrode seat.

[0012] The platinum sheet and the platinum wire of the boiling nitric acid counter electrode are welded together by laser electric welding. The polytetrafluoroethylene rod is expanded by high temperature heating, and the platinum wire passes through the polytetrafluoroethylene rod with a through hole. The connecting part between the platinum sheet and the platinum wire is partially sealed, and the wire of the counter electrode is led out from the counter electrode seat, and a polytetrafluoroethylene-coated rubber plug is provided in the electrode seat.

[0013] The salt bridge of the boiling nitric acid reference electrode has a small hole for filling a certain amount of nitric acid solution. The small hole is sealed with a polytetrafluoroethylene sealing plug. One end of the salt bridge is inserted into the test electrolytic cell, and the other end is inserted into a container with a saturated calomel electrode and filled with saturated potassium nitrate solution.

[0014] The electrochemical test system is composed of an electromagnetic shielding box, an electrochemical workstation and connecting wires. The electrochemical workstation is placed in the electromagnetic shielding box and is connected to three electrodes of the test part through small holes on the side of the electromagnetic shielding box.

[0015] The tail gas treatment system is provided with a condenser and a tail gas treatment device, one end of the condenser is connected to the upper end of the condenser, and the other end is connected to a container filled with sodium hydroxide solution, and the water inlet and outlet of the condenser are connected to a circulating water tank.

[0016] The temperature control system consists of a heating device in which a heating wire is placed in a quartz glass test tube filled with methyl silicone oil and a temperature sensor also fixed on the top cover of the electrolytic cell, which is used to set the target temperature and control the heating speed, so that the working temperature in the electrolytic cell is controlled in the range of 0 to 300°C and the heating rate is 3 to 10°C / minute.

[0017] The special cylinder is installed on a column with a lifting system. The cylinder can set its stroke independently. The hydraulic cylinder of the lifting system controls the vertical position adjustment of the entire cylinder. The scratching speed is adjusted by adjusting the cylinder pressure through the throttle valve. The manual reversing valve controls the reciprocating motion of the scratching movement rod. A high-precision time sensor is installed on the scratching movement axis to accurately record the single movement time of the cylinder. By twisting the fine-tuning knob I, multiple ectopic scratches can be achieved. The maximum number of scratches is determined by the size of the working electrode and the scratch spacing set for each experiment.

[0018] The scratching motion shaft adopts high-temperature sintering sealing of polytetrafluoroethylene hose, an alloy rod resistant to high-temperature nitric acid corrosion is used inside the shaft body, and a polytetrafluoro hose is used to seal the alloy rod outside. A polytetrafluoro sealing gasket and a polytetrafluoro coating belt are used to seal the moving shaft hole at the contact with the electrolytic cell top cover. The upper end of the scratching motion shaft is connected to the pneumatic piston rod in the cylinder, and the lower end of the motion shaft is connected to the scratching head device.

[0019] The scratching head device is composed of a scratching needle and a scratching needle slot. The scratching needle is made of insulating and hard diamond, and different scratching needles can be replaced. A load measuring device is arranged in the scratching needle slot, and the load size can be changed and measured in real time by twisting the fine-tuning knob II.

[0020] During the experiment, nitric acid is placed in the boiling nitric acid electrolytic cell and made to boil. Therefore, the boiling nitric acid electrolytic cell, the scratching movement rod, the working electrode clamping device and other structures are required to withstand long-term corrosion and prevent nitric acid vapor from leaking. In addition to the above-selected materials, other suitable materials that can withstand high-temperature nitric acid corrosion can also be used for each part of the structure.

[0021] The present invention has the following advantages and beneficial effects:

[0022] 1. The present invention realizes the in-situ scratch electrochemical test of the passivation film in boiling nitric acid. The three-electrode system manufactured by a special process can realize in-situ electrochemical testing in boiling concentrated nitric acid while scratching.

[0023] 2. The present invention can achieve multiple scratches at different locations and perform in-situ electrochemical tests simultaneously through the coordinated movement of the cylinder and the slide rail, and can install a sample once to perform multiple scratch tests, which is more efficient than the existing scratching device.

[0024] 3. The present invention can achieve accurate control and measurement of load size.

[0025] 4. The present invention can control the speed of the scratching motion axis and record the single scratching time of the scratching motion axis. The timing resolution of the high-precision timer is 0.1ms.

[0026] 5. The present invention adopts special sealing design and special material selection, which will not corrode the external equipment of the electrolytic cell while ensuring safety.

[0027] 6. The present invention ensures that each experiment is not affected by changes in sample thickness through a specially designed clamping device.

[0028] 7. The present invention adopts modular design, and each part of the device can be easily disassembled, combined and modified. It also adopts a circulating water tank and an exhaust gas treatment device to achieve the purpose of water saving and environmental protection.

[0029] 8. The devices of the present invention are interrelated in technology and coordinated in use. The independent control and coordinated actions of each component can be completed through the control panel buttons and manual switches. The cylinder movement time, heating temperature, and load size are converted into digital signals through ADC, which improves the controllability of the experiment, the effectiveness of the results, and the evaluability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a schematic diagram of the structure. It includes: a base with a slide rail 1, a fine-tuning knob I 2, a fine-tuning knob II 3, a bottom plate of a boiling nitric acid electrolytic cell 4, a side wall of a boiling nitric acid electrolytic cell 5, a working electrode clamping device 6, an electrolytic cell top cover 7, a boiling nitric acid working electrode 8, a polytetrafluoroethylene gasket 9, a nitrate bridge 10, a heating device 11, a scratching needle 12, a scratching device 13, a temperature sensor 14, a condenser 15, a stud bolt 16, a polytetrafluoroethylene coated gasket 17, a circulating water tank 18, a container filled with sodium hydroxide solution 19, a saturated calomel electrode 20, a pressure display 21, a column 22, a counter electrode seat 23, a special cylinder 24, a speed measurement system 25, a manual reversing valve 26, a boiling nitric acid counter electrode 27, a container filled with a saturated potassium nitrate solution 28, a scratching motion shaft 29, a polytetrafluoroethylene sealing plug 30, a polytetrafluoroethylene coated belt 31, a working electrode seat 32, and a lifting system 33.

[0031] Figure 2 It is a schematic diagram of the clamping surface of the working electrode, including the working electrode 8, the stylus positioning scale line 34, the working electrode cylindrical part 35, the cylindrical fixing buckle 36, the clamping plate fastening bolt 37, the clamping plate 38, and the working electrode fixing buckle 39.

[0032] Figure 3 It is a schematic diagram of a scratching device, which includes a scratching needle 12, a scratching motion axis 29, and a pressure sensor 40.

[0033] Figure 4 It is a schematic diagram of the boiling nitric acid working electrode of the present invention, wherein the working electrode cylindrical portion 35, the polytetrafluoroethylene hose 41, the polytetrafluoroethylene sleeve 42, and the copper wire 43.

[0034] Figure 5 Schematic diagram of boiling nitric acid counter electrode of the present invention, including platinum sheet 44, platinum wire 45, polytetrafluoroethylene rod 46. DETAILED DESCRIPTION

[0035] like Figure 1-Figure 5 As shown, the present invention provides an in-situ multiple-time different-location scratching electrode system for simulating spent fuel post-processing boiling nitric acid, which mainly comprises: a base 1 with a slide rail, a fine-tuning knob I 2, a fine-tuning knob II 3, an electrolytic cell bottom plate 4, an electrolytic cell side wall 5, a working electrode clamping device 6, an electrolytic cell top cover 7, a working electrode 8, a polytetrafluoroethylene gasket 9, a nitrate bridge 10, a heating device 11, a scratching needle 12, a scratching device 13, a temperature sensor 14, a condenser 15, a stud bolt 16, a polytetrafluoroethylene coated gasket 17, a circulating water tank 18, a container filled with sodium hydroxide solution 19, a saturated calomel electrode 20, a pressure display 21, a column 22. Counter electrode holder 23. Special cylinder 24. Speed ​​measuring system 25. Manual reversing valve 26. Counter electrode 27. Container filled with saturated potassium nitrate solution 28. Scratched moving shaft 29. Polytetrafluoroethylene sealing plug 30. Polytetrafluoroethylene covering tape 31. Working electrode holder 32. Lifting system 33. Scribing needle positioning scale line 34. Working electrode cylindrical part 35. Cylindrical fixing buckle 36. Clamp plate fastening bolt 37. Clamp plate 38. Working electrode fixing buckle 39. Pressure sensor 40. Polytetrafluoroethylene hose 41. Polytetrafluoroethylene sleeve 42. Copper wire 43. Platinum sheet 44. Platinum wire 45. Polytetrafluoroethylene rod 46.

[0036] The specific structure is as follows:

[0037] The boiling nitric acid electrolytic cell consists of an electrolytic cell bottom plate 4 and a side wall 5. The bottom plate 4 is fixed to a base 1 equipped with two mutually perpendicular slide rails by bolt assembly. A knob with a scale is respectively provided on the side and front of the base. The front fine-tuning knob Ⅰ2 can control the electrolytic cell to move forward and backward on the horizontal plane, and one scale of the knob represents 1mm. The side fine-tuning knob Ⅱ3 can control the electrolytic cell to move left and right on the horizontal plane, and one scale of the knob represents 0.01mm. The electrolytic cell material is polytetrafluoroethylene.

[0038] The working electrode clamping device 6 is divided into a clamp fixing part and a working electrode fixing part. The clamp fixing part is installed on the bottom plate 4 of the electrolytic cell by threads and fixed to the bottom plate 4 of the electrolytic cell by bolts. The working electrode 8 is fixed in the groove of the working electrode fixing part. A polytetrafluoroethylene gasket 9 is placed behind the working electrode to adjust the position of the working electrode. A card plate 38 is added to the groove. The card plate 38 is fixed by a card plate fastening bolt 37. The gasket ensures that there is no raised step between the working electrode 8 and the card plate 38. The left and right sides of the working electrode 8 are respectively strengthened by using working electrode fixing buckles 39. The cylindrical fixing buckle 36 fastens the cylindrical part 35 of the working electrode. The entire working electrode clamping device is made of insulating polytetrafluoroethylene that is resistant to corrosion by boiling concentrated nitric acid.

[0039] A boiling nitric acid working electrode holder 32, a boiling nitric acid counter electrode holder 23, a salt bridge 10 of a boiling nitric acid reference electrode, a heating device 11, a temperature sensor 14, a condenser 15, and a scratching motion shaft 29 are installed on the electrolytic cell top cover 7. The electrolytic cell top cover 7 is made of quartz glass, and the electrolytic cell top cover 7 and the electrolytic cell side wall 5 are locked by stud bolts 16 and polytetrafluoroethylene coated washers 17.

[0040] The boiling nitric acid working electrode 8 is welded to the end of the working electrode cylindrical part 35 by laser spot welding with a copper wire 43. The cylindrical part of the working electrode is first sealed by high-temperature sintering with a polytetrafluoroethylene hose 41, and then the entire structure is sealed with a polytetrafluoroethylene sleeve 42. The wire of the working electrode 8 is led out from the working electrode seat 32, and a polytetrafluoroethylene-coated rubber plug is provided in the electrode seat.

[0041] The platinum sheet 44 and the platinum wire 45 of the boiling nitric acid counter electrode are welded together by laser welding. The polytetrafluoroethylene rod 46 is expanded by high temperature heating, so that the platinum wire 45 passes through the polytetrafluoroethylene rod 46 with a through hole. Finally, the connection between the platinum sheet 44 and the platinum wire 45 is partially sealed, and the wire of the counter electrode 27 is led out from the counter electrode seat 23, and a polytetrafluoroethylene-coated rubber plug is provided in the electrode seat.

[0042] The salt bridge 10 of the boiling nitric acid reference electrode has a small hole for filling with nitric acid solution and is sealed with a polytetrafluoroethylene rubber plug 30. One end of the salt bridge 10 is inserted into the test electrolytic cell, and the other end is inserted into a container 28 containing a saturated calomel electrode 20 and filled with saturated potassium nitrate solution.

[0043] The electrochemical test system consists of an electromagnetic shielding box, an electrochemical workstation and connecting wires. The electrochemical workstation is placed in the electromagnetic shielding box. The electrochemical workstation is connected to the three electrodes of the test part (i.e., working electrode, counter electrode, and reference electrode) through small holes on the side of the electromagnetic shielding box.

[0044] The tail gas treatment system is provided with a condenser 15 and a tail gas treatment device (i.e., a container filled with sodium hydroxide solution). The lower end of the condenser 15 extends into the boiling nitric acid electrolysis cell, one end of the condenser tube is connected to the upper end of the condenser 15, and the other end of the condenser tube is connected to the container 19 filled with sodium hydroxide solution. The water inlet and outlet of the condenser are connected to the circulating water tank 18.

[0045] The temperature control system consists of a heating device 11 in which a heating wire is placed in a quartz glass test tube filled with methyl silicone oil and a temperature sensor 14 also fixed on the top cover 7 of the electrolytic cell. It is used to set the target temperature and control the heating speed, so that the temperature control range in the electrolytic cell is 0 to 300°C and the heating rate is 3 to 10°C / minute.

[0046] The special cylinder 24 is installed on the column 22 with the lifting system 33. The hydraulic cylinder of the lifting system 33 can control the position adjustment of the special cylinder 24 in the vertical direction, and the scratching speed can be adjusted by adjusting the cylinder pressure through the throttle valve. The manual reversing valve 26 can control the reciprocating motion of the scratching movement rod. The speed measuring system 25 with a high-precision time sensor is installed on the scratching movement shaft 29 to accurately record the single movement time of the cylinder. By twisting the fine-tuning knob Ⅰ2, multiple ectopic scratches can be achieved. The number of scratches is determined by the scratch spacing set for each experiment.

[0047] The scratching motion shaft 29 is sealed by high-temperature sintering of a polytetrafluoroethylene hose, an alloy rod resistant to high-temperature nitric acid corrosion is used inside the shaft body, and a polytetrafluoroethylene hose is used to seal the alloy rod outside. A polytetrafluoroethylene sealing gasket and a polytetrafluoroethylene coating tape 31 are used to seal the moving shaft hole at the contact with the electrolytic cell top cover 7. The upper end of the scratching motion shaft 29 is connected to the pneumatic piston rod in the special cylinder 24, and the lower end of the scratching motion shaft 29 is connected to the scratching head device 13.

[0048] The scratching head device 13 consists of a scratching needle 12 and a scratching needle slot. Before the test, the position of the scratching needle 12 is adjusted to the scratching needle positioning scale line 34. The scratching needle 12 is made of insulating and hard diamond, and different scratching needles can be replaced. A load measuring device is arranged in the scratching needle slot. The load measuring device consists of a pressure sensor 40 and a pressure display 21. The pressure sensor 40 contacts the tail end of the scratching needle 12. The scratching needle 12 contacts the working electrode to generate pressure. The pressure sensor 40 receives the pressure signal. The load system connecting line is led out from the middle of the scratching motion axis 29. The fine-tuning knob Ⅱ3 is twisted to adjust the contact pressure between the working electrode 8 and the scratching needle 12, so as to change the load size and display the load in real time on the pressure display 21.

[0049] In the present invention, the maximum operating temperature is 260° C., which is not only applicable to boiling concentrated nitric acid systems, but also can simulate corrosion tests of other systems, such as strong acid, strong alkali and other harsh corrosion systems.

[0050] In the present invention, the devices are technically related to each other and cooperate with each other in use. The switches of the special cylinder 24, the temperature sensor 14, the heating wire 11, and the pressure sensor 40 are all controlled by independent relays and integrated in the control box. During implementation, the independent control and coordinated actions of each component can be completed through the control panel buttons and the manual switch valve. The cylinder movement time, heating temperature, and load size are converted into digital signals through ADC to improve the controllability of the experiment, the effectiveness of the results, and the evaluability.

[0051] The working process of the electrode system for simulating boiling nitric acid in spent fuel reprocessing multiple times in situ and at different locations of the present invention is as follows:

[0052] 1. The copper wire 43 is welded to the end of the cylindrical part 35 of the working electrode by laser spot welding, and the cylindrical part 35 of the working electrode is sealed by high-temperature sintering sealing technology of a polytetrafluoroethylene hose 41. Then, the entire structure is sealed with a polytetrafluoroethylene sleeve 42 to form a working electrode 8. The working electrode 8 is placed in the groove of the working electrode fixing part at the upper end of the working electrode clamping device 6, and a card plate 38 is placed. The number of polytetrafluoroethylene gaskets 9 is controlled to ensure that there is no raised step between the working electrode 8 and the card plate 38. The card plate 38 is fixed with a card plate fastening bolt 37. The left and right sides of the working electrode 8 are respectively strengthened with working electrode fixing buckles 39, and then the working electrode cylindrical part 35 is fastened with a working electrode cylindrical fixing buckle 36. The fixture fixing part of the entire working electrode clamping device 6 is installed on the bottom plate 4 of the electrolytic cell by threads, and is fixed to the bottom plate 4 of the electrolytic cell by bolts. The bottom plate 4 of the electrolytic cell is fixed to the base 1 equipped with two mutually perpendicular slide rails by bolt assembly.

[0053] 2. Lead the working electrode 8 wire out of the working electrode holder 32, install the counter electrode 27, the salt bridge 10 of the reference electrode, the heating device 11 and the temperature sensor 14, the condenser 15, and the scratching motion shaft 29 on the electrolytic cell top cover 7 respectively, lead the counter electrode wire out of the counter electrode holder 23, install the scratching needle 12 into the scratching needle slot, and adjust the height of the scratching motion shaft 29 with the scratching head device 13 to the scratching needle positioning scale line 34 through the lifting system 33 installed on the column 22, adjust the micro-knob II3 to set the scratch load, add concentrated nitric acid solution at room temperature, adjust the electrolytic cell body and the electrolytic cell top cover 7 to a suitable height, and then use the stud bolts 16 and the polytetrafluoroethylene coated gasket 17 to lock the electrolytic cell top cover 7 and the electrolytic cell side wall 5.

[0054] 3. Fill the circulating water tank 18 with cooling water, turn on the heating device 11, heat to the specified temperature, and then passivate for the specified time.

[0055] 4. The throttle valve adjusts the pressure in the special cylinder 24 to change the speed of the scratching motion shaft 29. At the same time, the speed measuring system 25 is turned on, and the manual reversing valve 26 is pressed. The upper part of the special cylinder 24 is quickly inflated, pushing the scratching motion shaft 29 downward to scratch the surface of the working electrode 8 at the set speed, producing a scratch and destroying the passivation film on the surface of the working electrode 8. At the same time, the electrochemical test system monitors the electrochemical signal in real time.

[0056] 5. Press the time reset button in the speed measurement system 25, adjust the micro knob Ⅰ2, control the working electrode 8 to move outward a specified distance, wait for a certain period of time, press the manual reversing valve 26, and the lower part of the special cylinder 24 is quickly inflated to push the scratching motion shaft 29 to scratch the surface of the working electrode 8 upward at the set speed, producing a scratch, and measure and record the electrochemical signal of the re-film formation process of the passivation film on the surface of the working electrode 8 again.

[0057] 6. Repeat step 4 to scratch at different locations again. The interval time, scratching load and scratching speed can be controlled by yourself.

[0058] 7. Repeat step 5 to scratch at different locations again. The interval time, scratch load and scratch speed can be controlled by yourself.

[0059] The above is only the best example of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A system for simulating multiple in-situ scratching of electrodes in different locations by boiling nitric acid in spent fuel reprocessing. It is characterized in that It includes a boiling nitric acid electrolytic cell, a working electrode clamping device, an electrolytic cell top cover, a boiling nitric acid working electrode, a boiling nitric acid reference electrode, a boiling nitric acid counter electrode, a special cylinder, a scratching motion axis, a scratching head device, a temperature control system, an electrochemical testing system and an exhaust gas treatment system; wherein the boiling nitric acid electrolytic cell is composed of an electrolytic cell bottom plate and a side wall, wherein the bottom plate is assembled and fixed on a base equipped with two mutually perpendicular slide rails by bolts, and a knob with a scale is respectively provided on the side and front of the base, wherein the fine-tuning knob I on the front controls the electrolytic cell to move forward and backward on the horizontal plane, and the fine-tuning knob II on the side controls the electrolytic cell to move left and right on the horizontal plane, and the electrolytic cell material is polytetrafluoroethylene; the special cylinder is installed on a column with a lifting system, the hydraulic cylinder of the lifting system controls the position adjustment of the special cylinder in the vertical direction, and the scratching speed is adjusted by adjusting the cylinder pressure through a throttle valve, the manual reversing valve controls the reciprocating motion of the scratching motion rod, and a speed measurement system with a high-precision time sensor is installed on the scratching motion The scratching motion axis is sealed by high-temperature sintering of a polytetrafluoroethylene hose, and a polytetrafluoroethylene sealing gasket and a polytetrafluoroethylene coated belt are used to seal the moving axis hole at the contact with the top cover of the electrolytic cell. The upper end of the scratching motion axis is connected to a pneumatic piston rod in a special cylinder, and the lower end of the scratching motion axis is connected to a scratching head device. The scratching head device is composed of a scratching needle and a scratching needle slot. Before the test, the position of the scratching needle is adjusted to the scratching needle positioning scale line. The scratching needle is made of diamond and can be replaced with different scratching needles. A load measuring device is arranged in the scratching needle slot. The load measuring device is composed of a pressure sensor and a pressure display. The pressure sensor contacts the tail end of the scratching needle, and the scratching needle contacts the working electrode to generate pressure. The pressure sensor receives the pressure signal. The load system connection line is led out from the middle of the scratching motion axis. The contact pressure between the working electrode and the scratching needle is adjusted by twisting the fine-tuning knob II to change the load size and display the load in real time on the pressure display.

2. According to claim 1, a system for simulating boiling nitric acid in spent fuel reprocessing to scratch an electrode multiple times in situ, It is characterized in that For fine-tuning knob I, one scale division represents 1mm, and for fine-tuning knob II, one scale division represents 0.01mm.

3. The electrode system for simulating boiling nitric acid in spent fuel reprocessing and scratching multiple times in different places according to claim 1, It is characterized in that The working electrode clamping device is divided into a clamp fixing part and a working electrode fixing part. The clamp fixing part is installed on the bottom plate of the electrolytic cell through threads and fixed to the bottom plate of the electrolytic cell through bolts. The working electrode is fixed in the groove of the working electrode fixing part. A polytetrafluoroethylene gasket is placed behind the working electrode to adjust the position of the working electrode. A card plate is added to the groove, and the card plate is fixed with a card plate fastening bolt. The gasket ensures that there is no raised step between the working electrode and the card plate. The left and right sides of the working electrode are respectively strengthened with working electrode fixing buckles, and the cylindrical fixing buckle fastens the cylindrical part of the working electrode. The entire working electrode clamping device is made of polytetrafluoroethylene material.

4. The electrode system for simulating boiling nitric acid in spent fuel reprocessing and scratching multiple times in different places according to claim 1, It is characterized in that The electrolytic cell top cover is installed with a boiling nitric acid working electrode seat, a boiling nitric acid counter electrode seat, a salt bridge of a boiling nitric acid reference electrode, a heating device, a temperature sensor, a condenser, and a scratching motion axis. The electrolytic cell top cover is made of quartz glass, and the electrolytic cell top cover is locked with a side wall of the electrolytic cell by stud bolts and a polytetrafluoroethylene-coated gasket.

5. The electrode system for simulating boiling nitric acid in spent fuel reprocessing and scratching multiple times in different places according to claim 1, It is characterized in that The boiling nitric acid working electrode is welded with a copper wire at the end of the cylindrical part of the working electrode by laser spot welding, the cylindrical part of the working electrode is first sealed by a polytetrafluoroethylene hose high-temperature sintering sealing technology, and then the entire structure is sealed with a polytetrafluoroethylene sleeve, the wire of the working electrode is led out from the working electrode seat, and the electrode seat is provided with a polytetrafluoroethylene coated rubber plug; the platinum sheet and platinum wire of the boiling nitric acid counter electrode are welded together, the platinum wire passes through a polytetrafluoroethylene rod with a through hole, and then the connection between the platinum sheet and the platinum wire is partially sealed, the wire of the boiling nitric acid counter electrode is led out from the counter electrode seat, and the electrode seat is provided with a polytetrafluoroethylene coated rubber plug; the salt bridge of the boiling nitric acid reference electrode is provided with a small hole for filling with nitric acid solution, the small hole is sealed with a polytetrafluoroethylene rubber plug, one end of the salt bridge is inserted into a test electrolytic cell, and the other end is inserted into a container with a saturated calomel electrode and filled with saturated potassium nitrate solution.

6. The electrode system for simulating boiling nitric acid in-situ multiple scratches at different locations in spent fuel reprocessing according to claim 1, It is characterized in that The electrochemical test system is composed of an electromagnetic shielding box, an electrochemical workstation and connecting wires. The electrochemical workstation is placed in the electromagnetic shielding box and is connected to three electrodes of the test part through small holes on the side of the electromagnetic shielding box.

7. The electrode system for simulating boiling nitric acid in-situ multiple scratches at different locations in spent fuel reprocessing according to claim 1, It is characterized in that The tail gas treatment system is provided with a condenser and a tail gas treatment device. The lower end of the condenser extends into a boiling nitric acid electrolytic cell. One end of the condenser tube is connected to the upper end of the condenser. The other end of the condenser tube is connected to a container filled with sodium hydroxide solution. The water inlet and outlet of the condenser are connected to a circulating water tank.

8. The electrode system for simulating boiling nitric acid in spent fuel reprocessing and scratching multiple times in different places according to claim 1, It is characterized in that The described temperature control system consists of a heating device with a heating wire placed in a quartz glass test tube filled with methyl silicone oil and a temperature sensor, and is used for setting the target temperature and controlling the heating rate, achieving a temperature control range of 0 to 300 °C and a heating rate of 3 to 10 °C per minute in the electrolytic cell.

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