Device and method for monitoring flow accelerated corrosion thinning through radioactive tracer method

Abstract

The invention belongs to the field of flow accelerated corrosion testing of nuclear power plant secondary circuit pipeline materials, and particularly discloses a device and method for monitoring flow accelerated corrosion thinning through a radioactive tracer method.The device comprises a test pipe section embedded with 60Co, and the mass fraction of cobalt in the pipe is 0.1%-1.0%; the fluid circulation system is used for forming simulation fluid with preset temperature and pressure and comprises a steam generator, and a turbocharging module, a fluid circulation pump and a spray control unit which are integrated in the steam generator; the gamma-ray monitoring system is provided with a plurality of NaI detectors; the cobalt interception module is used for blocking 60Co recirculation interference and comprises ion exchange resin and a filter; and the downstream pipeline is also connected with an environment detection module and a water chemical regulation system. The problems that in the prior art, the corrosion amount cannot be monitored in real time, and an electrochemical method is poor in reliability are solved, real-time monitoring of the corrosion amount is achieved, the measurement reliability under the conditions of the high flow speed and the gas-liquid two-phase flow is improved, and the activity signal and the actual corrosion amount are accurately correlated.

Description

Technical Field

[0001] The present invention relates to the field of flow accelerated corrosion testing of secondary circuit pipeline materials in nuclear power plants, and particularly to a device for monitoring flow accelerated corrosion thinning by radioactive tracer method. Background Art

[0002] Flow Accelerated Corrosion (FAC) refers to the phenomenon of local accelerated corrosion of pipelines under the action of single-phase liquid flow or gas-liquid two-phase flow. It is one of the main failure modes of secondary circuit pipelines in nuclear power plants. The secondary circuit pipelines in nuclear power plants are continuously scoured by high-temperature and high-pressure water or wet steam for a long time, and the wall thickness will gradually thin, thus seriously affecting the safe and stable operation of the circuit.

[0003] At present, there are deficiencies in the corrosion rate monitoring of flow accelerated corrosion test devices. For example, the patent with the publication number CN106124393A discloses a flow accelerated corrosion test device, which studies the law of pipeline thickness thinning by setting test sections such as elbows, reducers, and tees. However, it measures the corrosion rate with a thickness gauge and cannot achieve real-time monitoring of the corrosion amount. Another patent with the publication number CN105223128A discloses a flow accelerated corrosion simulation experiment device using an electrochemical measurement method. Although it can measure the corrosion rate online, the reliability of electrochemical measurement is poor under high flow rate and gas-liquid two-phase flow conditions. This is because bubbles, impurities, or corrosion product suspensions in the gas-liquid two-phase flow may interfere with the contact on the electrode surface, thus affecting the stability and accuracy of the electrochemical signal.

[0004] Non-destructive γ-ray measurement technology has been widely used in the fields of nuclear energy and radiation protection. The patent with the publication number CN119716959A discloses a non-destructive γ measurement device based on a NaI detector, which is suitable for rapid non-destructive detection of samples such as work shoes of nuclear power plant workers and has a high release control accuracy. However, the existing technology fails to effectively integrate the decay correction algorithm and the corrosion release separation algorithm, resulting in the inability to accurately correlate the activity signal with the actual corrosion amount, which limits its application in the field of corrosion monitoring.

[0005] Therefore, it is necessary to provide a real-time monitoring device and method for the thinning rate of metal pipelines in a high-temperature and high-pressure environment based on radioactive isotope tracer technology to solve the above technical problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a device and method for monitoring flow accelerated corrosion thinning by radioactive tracer method, to supplement and improve the existing experimental devices, systems, and experimental methods, so as to more accurately simulate the actual working conditions, monitor the corrosion dynamic data, and effectively control the experimental conditions, thereby providing more reliable technical support for the corrosion research and safety assessment of secondary circuit pipelines in nuclear power plants.

[0007] To achieve the above object, in one aspect, the present invention provides a device for monitoring flow-accelerated corrosion thinning by a radioactive tracer method, comprising:

[0008] A test pipe section, in which radioactive 60 Co is uniformly embedded, the cobalt mass fraction of the test pipe section is 0.1%-1.0%, and the test pipe section is detachably connected to the pipeline;

[0009] A fluid circulation system, connected to the upstream pipeline of the test pipe section, including a steam generator and a turbocharging module, a fluid circulation pump and a spray control unit integrated in the steam generator, for forming a simulated fluid at a preset temperature and pressure;

[0010] A γ-ray monitoring system, including a plurality of NaI detectors arrayed on the test pipe section;

[0011] A cobalt retention module, connected to the downstream pipeline of the test pipe section, for blocking 60 Co recirculation interference; the cobalt retention module includes an ion exchange resin and a filter, the ion exchange resin is used for adsorbing Co in the solution 2+ ,and the filter intercepts cobalt-containing particles in the solution;

[0012] On the downstream pipeline of the test pipe section, there is also connected an environmental detection module for monitoring pH value, conductivity, 60 Co residual activity, and a water chemistry regulation system for maintaining experimental conditions based on the monitored values.

[0013] In some alternative embodiments of the present invention, a radioactive shielding device is provided on the side of the test pipe section away from the γ-ray monitoring system.

[0014] Further, the radioactive shielding device adopts a multi-layer shielding structure, including a lead shielding layer and a concrete layer.

[0015] In some alternative embodiments of the present invention, the cobalt mass fraction of the test pipe section is 0.5%.

[0016] In some alternative embodiments of the present invention, the test pipe section is connected to the pipeline through a standard flange interface.

[0017] In some alternative embodiments of the present invention, the radioactive 60 Co enters the test pipe section by smelting incorporation or high-temperature diffusion process.

[0018] Further, the ion exchange resin in the cobalt retention module adopts Chelex-100 resin to adsorb Co in the solution 2+ .

[0019] In some alternative embodiments of the present invention, a thermometer is connected inside the steam generator to detect and display the temperature of the steam during the experiment.

[0020] In some alternative embodiments of the present invention, a flow meter is provided on the pipeline from the steam generator to the test pipe section to measure the fluid velocity in the pipeline.

[0021] In some alternative embodiments of the present invention, a pressure gauge is provided on the pipeline from the steam generator to the test pipe section to detect and display the internal pressure of the pipeline.

[0022] In some alternative embodiments of the present invention, a re-purification circuit is connected between the pipeline at the front end of the water chemistry regulation system and the pipeline at the front end of the cobalt interception module.

[0023] In some alternative embodiments of the present invention, a ball valve is installed on the pipeline at the front end of the water chemistry regulation system to control the wet steam reflux. When 60 the residual activity of Co reaches a preset value, the valve closes to prevent the 60 Co content in the water chemistry circuit from affecting the experimental results.

[0024] In some alternative embodiments of the present invention, the environmental detection module includes a pH monitor, a conductivity meter, and a radioactivity detector for 60 precisely monitoring the residual activity of Co to ensure the reliability of experimental data and strictly control the radioactive risk.

[0025] In some alternative embodiments of the present invention, the NaI detector array of the γ-ray monitoring system is uniformly arranged around the outer wall of the test pipe section and is parallel to the axis of the test pipe section.

[0026] In some alternative embodiments of the present invention, a regenerative heat exchanger is further included, which is connected between the water chemistry regulation system and the steam generator. The regenerative heat exchanger is communicated with the steam generator through an upper charging pipeline and a lower discharging pipeline to achieve a heat cycle.

[0027] On the other hand, the present invention provides a method for monitoring flow-accelerated corrosion thinning by radioactive tracer method. According to the device for monitoring flow-accelerated corrosion thinning by radioactive tracer method described in any one of the above, the method includes the following steps:

[0028] S1. Measure the surface area of the test pipe section, denoted as S; record the pipe material density of the test pipe section, denoted as ρ; determine the mass fraction of cobalt in the pipe material, denoted as w Co ; measure the initial total mass of radioactive cobalt, denoted as m0; determine 60 the specific activity of Co, denoted as S A ; calculate 60 the initial activity of Co, denoted as A0, where A0 = S A ·m0;

[0029] S2. High-temperature and high-pressure wet steam flows into the test pipe section from below and out from above. After the temperature, flow rate, and pressure are all stable, the flow-accelerated corrosion test is started. At this time, the timing is t0, and the measurement of the 60 counting rate corresponding to the initial activity of Co is recorded as C0;

[0030] S3. After the corrosion experiment has been carried out for a time t, the counting rate corresponding to the activity of Co in the test section is measured again and recorded as C(t); 60

[0031] S4. According to the dynamic decay correction and corrosion release separation algorithm, calculate the thickness loss Δd(t) and thinning rate R(t) of the pipe material.

[0032] Furthermore, the dynamic decay correction and corrosion release separation algorithm includes the following steps:

[0033] S41. Calculate the activity A decay (t) after time t according to the natural decay formula:

[0034] A decay (t) = A0·e -λt

[0035] where A decay (t) is the activity after time t; λ is the decay constant, ln2 / T 1 / 2 , T 1 / 2 is the half-life of the isotope, 5.27 years (46165 h), and λ can be obtained as 1.5×10 -5 h -1 ; t is the test running time;

[0036] S42. Calculate the activity loss caused by corrosion release according to the actually measured activity A measured (t) and the natural decay activity A decay (t);

[0037] S43. Calculate the decrease in the counting rate caused by corrosion release according to the relationship that the counting rate C measured by the detector is proportional to the activity;

[0038] S44. Calculate the total mass loss of the pipe material according to the proportional relationship between the mass of cobalt Δm(t) released by corrosion and the total mass loss Δm tube(t) of the pipe material. The formula is:

[0039]

[0040] S45. Calculate the thickness loss Δd(t) and thinning rate R(t) of the pipe material according to the total mass loss of the pipe material. The formula is:

[0041] ​

[0042] Further, the radioactive detector monitors in real time 60 the residual activity of 60 Co. When the residual activity reaches a preset value, the ball valve is closed to prevent the

[0043] content of

[0044] Co in the water chemical loop from affecting the experimental results. 60 Further, the fluid circulation system simulates the actual operating environment of the secondary loop of a nuclear power plant and supports various flow conditions such as single-phase liquid flow and gas-liquid two-phase flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0046] Figure 1 is a structural diagram of the device for monitoring flow-accelerated corrosion thinning by the radioactive tracer method of the present invention;

[0047] In the figure: 1. test pipe section; 2. steam generator; 3. γ-ray monitoring system; 4. radioactive shielding device; 5. ion exchange resin; 6. filter; 7. pH monitor; 8. conductivity meter; 9. radioactive detector; 10. ball valve; 11. repurification loop; 12. charging pipe; 13. letdown pipe; 14. regeneration heat exchanger; 15. water chemistry regulation system; 16. thermometer; 17. pressure gauge; 18. flowmeter; 19. precooling device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0049] In the prior art, flow-accelerated corrosion is one of the main failure modes of the secondary circuit pipes in nuclear power plants. The long-term erosion by high-temperature and high-pressure water or wet steam leads to the thinning of the pipe wall. Existing test devices have problems with insufficient corrosion rate monitoring. For example, thickness gauges cannot monitor in real time, and electrochemical measurements have poor reliability in high-flow or gas-liquid two-phase flows. Although the non-destructive γ-ray measurement technology has demodulation accuracy, it does not integrate the decay correction algorithm and the corrosion release separation algorithm, resulting in inaccurate correlation between the activity signal and the actual corrosion amount. Therefore, there are problems such as insufficient in-situ real-time performance, limited sensitivity, and poor adaptability to complex working conditions in the technology.

[0050] To solve the above problems, the inventors found that the principle of radioactive isotope tracing can be used to establish a direct correlation between the corrosion amount and the activity change. By uniformly embedding radioactive cobalt in the test pipe section, cooperating with the γ-ray monitoring system to capture the activity change in real time, setting up a fluid circulation system to simulate the real working conditions, and using the downstream interception module to block the interference of cobalt recycling. To achieve the accurate correlation between the activity signal and the corrosion amount, it is necessary to develop a dynamic decay correction and corrosion release separation algorithm to solve the influence of natural decay on the measurement data. In addition, the water chemistry regulation system and the environmental detection module work together to maintain a stable corrosion environment and control the radioactive risk.

[0051] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] Refer to Figure 1 As shown, the embodiments of the present invention provide a device for monitoring flow-accelerated corrosion thinning by radioactive tracing, including a test pipe section 1, a fluid circulation system, a γ-ray monitoring system, a cobalt interception module, an environmental detection module, and a water chemistry regulation system 15. Among them, radioactive 60 Co is uniformly embedded in the test pipe section 1, and the cobalt mass fraction is controlled within the range of 0.1%-1.0%, and it can be detachably connected to the pipeline; the fluid circulation system includes a steam generator 2 and integrated pressurization, circulation, and spray units; the γ-ray monitoring system uses an array-distributed NaI detector, and the NaI detector array is uniformly arranged around the outer wall of the test pipe section 1 and is parallel to the axis of the test pipe section 1; the cobalt interception module includes an ion exchange resin 5 and a filter 6; the downstream pipeline is connected to the environmental detection module and the water chemistry regulation system 15.

[0053] Specifically, the test pipe section 1 refers to a metal pipe with 60 60 Co incorporated. Specifically, the uniform distribution of cobalt can be achieved by smelting incorporation or high-temperature diffusion processes. The mass fraction range can ensure both detection sensitivity and avoid excessive radioactive contamination. The fluid circulation system refers to a device that simulates a high-temperature and high-pressure wet steam environment. Specifically, a turbocharging module can be used to adjust the fluid pressure, and a spray control unit can be used to adjust the humidity, providing flow conditions similar to real working conditions for the corrosion test. The γ-ray monitoring system refers to a non-destructive testing device based on a NaI detector. Specifically, an array layout parallel to the axis of the pipe section can be adopted to monitor the activity changes at different positions on the pipe wall in real time. The cobalt interception module refers to a device that blocks the recirculation of cobalt. Specifically, Chelex-100 resin can be used to adsorb dissolved cobalt ions, and a filter 6 can be used to intercept particulate cobalt, ensuring that the subsequent monitoring data only reflects the current corrosion state. The environmental detection module refers to a device that detects the pH value, conductivity, and 60 60 Co residue in real time. Specifically, a pH monitor 7, a conductivity meter 8, and a radioactive detector 9 can be linked to provide feedback control signals for the water chemistry regulation system 15. A ball valve 10 is installed on the pipeline at the front end of the water chemistry regulation system 15 to control the wet steam reflux. When the 60 60 Co residual activity reaches a preset value, the valve closes to prevent the 60 60 Co content in the water chemistry loop from affecting the experimental results.

[0054] As the main body where corrosion occurs, the uniformly distributed 60 60 Co dissolves into the fluid with the metal during the corrosion process, resulting in a decrease in the radioactive activity inside the pipe section. The fluid circulation system generates a simulated fluid with specific temperature, pressure, and phase state through turbocharging and spray control, scouring the test pipe section 1 to form accelerated corrosion. The array-distributed NaI detectors collect the γ-ray intensity changes in real time, and the wall thickness loss is inferred by the change in activity. The downstream cobalt interception module prevents cobalt-containing corrosion products from re-entering the circulation system to interfere with the detection data through a dual mechanism of adsorption and filtration. The environmental detection module continuously detects the fluid chemical parameters, links with the water chemistry regulation system 15 to maintain a stable corrosion environment, and at the same time monitors the residual activity through the radioactive detector 9, triggering a protection mechanism when the threshold is reached. Each subsystem forms a closed-loop detection system through pipeline series connection, and together with the dynamic decay correction algorithm, realizes the online continuous monitoring of the corrosion thinning rate.

[0055] Through the above technical solution, the present application realizes the real-time online monitoring of the corrosion thinning rate of metal pipelines in high-temperature and high-pressure environments. Under single-phase liquid flow or gas-liquid two-phase flow conditions, the γ-ray monitoring system can stably capture the activity change, overcoming the signal distortion problem of the electrochemical measurement method under high-flow conditions. The dynamic decay correction algorithm effectively distinguishes the activity loss caused by natural decay and corrosion release, reducing the thickness loss calculation error to within 5%. The synergistic effect of the cobalt interception module and the water chemistry regulation system 15 controls the fluctuation range of fluid chemical parameters within ±0.3 pH units during the experiment, ensuring the repeatability of the corrosion process. The entire set of devices can continuously operate for more than 2000 hours without interrupting the fluid circulation, meeting the long-term monitoring requirements of the secondary circuit pipelines in nuclear power plants.

[0056] In a further optimized solution, a radioactive shielding device 4 is provided on the side of the test pipe section 1 away from the γ-ray monitoring system.

[0057] Among them, the radioactive shielding device 4 is a physical barrier constructed by high-density materials. Specifically, a combined structure of a lead shielding layer and a concrete layer can be used to achieve it. The lead layer can block the penetration of medium and low-energy γ-rays, and the concrete layer provides supplementary shielding and enhances the structural stability. Among them, the side away from the γ-ray monitoring system is to arrange the shielding device at the symmetric position of the detector array based on the spatial orientation plan. Specifically, it can be achieved through the optimization of the axial layout of the pipe section to ensure an azimuth angle interval of 180° between the shielding body and the detector.

[0058] Specifically, the radioactive shielding device 4 extends axially along the test pipe section 1, and its coverage area forms a spatial complementary relationship with the detector array of the γ-ray monitoring system. When 60 the γ-rays released by Co penetrate the pipe wall, the rays in the direction of the detector are used for corrosion monitoring, while the rays in the direction away from the detector are absorbed by the shielding device. This layout method divides the spatial radiation path, retaining the ray flux required for monitoring while eliminating the radiation leakage in the non-monitoring direction. The thickness of the lead layer of the shielding device can be adjusted according to 60 the activity intensity of Co. For example, 5-15 mm lead plates are used to meet the radiation protection requirements of different experimental conditions.

[0059] Through the above structure with directional shielding design, while ensuring radiation safety, the detection efficiency of the γ-ray monitoring system is maintained, solving the inherent contradiction between the fully enclosed shielding structure and the monitoring requirements, realizing the effective isolation of radioactive substances during the experiment, reducing the radiation dose in the operation area to below the safety limit, and at the same time ensuring the integrity of the signals received by the γ-ray detector. The directional shielding structure avoids the attenuation interference of the traditional fully enclosed shielding on the monitoring signals, controlling the acquisition error of the corrosion activity data within 3%.

[0060] For a further optimized solution, the radioactive shielding device 4 adopts a multi-layer shielding structure, including a lead shielding layer and a concrete layer. Among them, the lead shielding layer is a radiation protection layer composed of high-density metal materials. Specifically, it can be formed by welding lead plates with a thickness of 5-20 mm, and the primary shielding is achieved by using the high-efficiency attenuation characteristics of lead atoms for γ rays. Among them, the concrete layer is a composite building material layer with portland cement as the matrix and heavy aggregates incorporated. Specifically, it can be formed by casting heavy concrete containing barium sulfate or magnetite, and it provides secondary shielding and structural support functions by virtue of the hydrogen element and high-density characteristics inside it.

[0061] Specifically, the lead shielding layer, as the first protection structure directly wrapped outside the test pipe section 1, rapidly attenuates the radiation intensity through the photoelectric effect and Compton scattering of lead atomic nuclei and high-energy γ rays. The concrete layer is arranged outside the lead shielding layer. The bound water and mineral components in its internal crystal structure can effectively absorb the neutrons generated by secondary radiation, and at the same time maintain the overall stability of the shielding device through its own rigid support characteristics. The thickness ratio of the lead layer to the concrete layer is controlled within the range of 1:3 to 1:5, which not only avoids the installation difficulties caused by the excessive weight of the pure lead structure, but also avoids the problem of the overly large volume required for the pure concrete structure to achieve the same shielding effect. Through the combined arrangement of the lead layer and the concrete layer in this solution, the overall weight is reduced by about 40% under the same shielding efficiency, and at the same time the external dimensions of the device are reduced by more than 30%.

[0062] For a further optimized solution, the cobalt mass fraction of the test pipe section 1 is 0.5%. Among them, the cobalt mass fraction is the mass ratio of cobalt element in the material of the test pipe section 1. Specifically, radioactive 60 Co can be uniformly embedded in the pipe matrix through smelting incorporation or high-temperature diffusion process. This parameter directly affects 60 the initial activity of Co and the structural stability of the pipe material, and it is necessary to ensure the radioactive signal intensity while avoiding the deterioration of the mechanical properties of the material.

[0063] Specifically, within the broad range of 0.1%-1.0%, by simulating the correlation experiment between the corrosion rate measurement sensitivity and the pipe material's anti-deformation ability under different flow rates and temperature conditions, it is found that a cobalt mass fraction of 0.5% can make the γ-ray signal generated by the radioactive activity reach the effective measurement threshold of the detector, and at the same time the pipe material does not show a decrease in yield strength or an exacerbation of intergranular corrosion under the erosion of high-temperature, high-pressure wet steam. The selection of this value is based on the optimized calculation of the cobalt distribution uniformity per unit surface area of the pipe material. By controlling the diffusion depth and concentration gradient of cobalt element during the smelting process, 60 a linear correspondence relationship is formed between the activity change amount of Co during the corrosion release process and the wall thickness reduction amount of the pipe wall.

[0064] Compared with the prior art, the existing test pipe section 1 only defines the range of cobalt mass fraction without specifying the specific optimized value, resulting in the risk of insufficient radioactive signal or premature failure of the material in practical applications. By precisely defining the cobalt mass fraction as 0.5%, the problem of stress corrosion cracking of the pipe caused by high cobalt content is avoided, and the defect of large activity measurement error caused by low cobalt content is overcome. The effectiveness of the parameters is verified under the typical operating conditions of 8 MPa in the secondary circuit of a nuclear power plant and a temperature of 280 °C.

[0065] Through the above technical solution, the present application achieves the best balance between the radioactive tracer sensitivity and the service reliability of the pipe, controls the measurement error of the flow accelerated corrosion thinning rate within ±5%, and at the same time, the test pipe section 1 still maintains 98% of the original tensile strength after continuous operation for 3000 hours, providing a stable basic condition for the long-term monitoring of the corrosion behavior of metal pipes in high-temperature and high-pressure environments.

[0066] In a further optimized solution, the test pipe section 1 is connected to the pipeline through a standard flange interface. The standard flange interface is a pipeline connection structure that is butt-jointed through prefabricated bolt holes and a sealing gasket, and specifically, a flange conforming to the ASME B16.5 or GB / T9119 standard can be used. It forms a rigid connection through bolt fastening, can withstand the mechanical stress and thermal stress generated by high-temperature and high-pressure fluids, and avoids leakage at the connection due to vibration or pressure fluctuation.

[0067] Specifically, the standardized design of the flange interface enables the test pipe section 1 and the pipeline system to be quickly disassembled and assembled without welding or customized processing, and only by matching flanges of the same specification. For example, in a high-temperature and high-pressure experimental environment, the sealing gasket of the flange can be a graphite wound gasket or a metal ring gasket to ensure fluid tightness. By evenly tightening the bolts, a stable pressing force is formed between the flange end faces, suppressing the pipeline vibration caused by fluid turbulence, thereby ensuring that the γ-ray detector and the outer wall of the pipe section maintain a fixed relative position and avoiding activity monitoring errors caused by connection loosening. In addition, test pipe sections 1 of different specifications can reuse the same set of pipeline systems by replacing the adapted flanges, significantly shortening the experimental preparation time.

[0068] In a further optimized solution, radioactive 60 Co enters the test pipe section 1 through smelting incorporation or high-temperature diffusion process.

[0069] Among them, the smelting incorporation process directly incorporates cobalt elements into the metal smelting process to achieve uniform distribution of cobalt atoms in the material matrix during the solidification stage of the liquid metal. Specifically, it can be achieved by adding cobalt isotope powder or cobalt alloy raw materials to the smelting raw materials and casting after stirring and melting mixing. Among them, the high-temperature diffusion process utilizes the principle of solid-state diffusion to allow cobalt atoms to penetrate into the lattice of the pipe at high temperatures. Specifically, induction heating or tube furnace heating methods can be used to cover the surface of the pipe section with a cobalt-containing coating in a protective atmosphere, and heat activation is used to promote the migration of cobalt atoms into the metal interior.

[0070] Specifically, in the smelting incorporation process, cobalt elements are uniformly dissolved in the liquid alloy during the metal smelting stage. After cooling and solidification, cobalt atoms are locked inside the metal lattice to form a stable solid solution structure. The high-temperature diffusion process allows cobalt atoms to diffuse into the pipe interior along grain boundaries or lattice interstices through heat treatment to form a metallurgical bonding layer with a gradient distribution. Both of these processes can ensure an atomic-level bonding between cobalt elements and the pipe matrix, avoiding problems of insufficient bonding force caused by mechanical mixing or surface attachment. During the flow-accelerated corrosion process, the corrosion thinning amount of the pipe is linearly corresponding to the release amount of cobalt elements. Thus, the activity change signal captured by the γ-ray monitoring system can accurately reflect the wall thickness loss.

[0071] Compared with the prior art, the traditional radioactive tracer addition methods mostly use surface plating or mechanical mixing methods, which are prone to tracer shedding due to scouring effects. However, the smelting incorporation and high-temperature diffusion processes adopted in this application deeply embed cobalt elements into the pipe interior through metallurgical bonding, significantly improving the bonding strength between the tracer and the matrix material, and ensuring that the release rate of the tracer is strictly synchronized with the pipe thinning rate during corrosion.

[0072] Through the above technical solutions, this application solves the problem of distorted monitoring signals caused by uneven distribution or weak bonding of radioactive isotopes in the pipe section, effectively avoiding the radioactive pollution risk caused by tracer shedding. The two process options meet the requirements of different material pipe sections. For example, the high-temperature diffusion process is particularly suitable for the subsequent treatment of formed pipes, and stable bonding of the tracer can be achieved without re-smelting.

[0073] In a further optimized solution, the ion exchange resin 5 in the cobalt interception module uses Chelex-100 resin to adsorb Co in the solution 2+ . Among them, Chelex-100 resin is a chelating ion exchange material containing iminodiacetic acid groups, which forms stable coordination bonds with cobalt ions through nitrogen and oxygen atoms in its molecular structure. This resin can maintain its adsorption capacity within the pH range of 3 - 12, and the upper limit of the working temperature can reach 80°C. Among them, Co 2+Adsorption efficiency is the ability of unit mass of resin to capture cobalt ions in the mobile phase and can be optimized by adjusting the resin packing density and contact time.

[0074] Specifically, in a high temperature and high pressure wet steam environment, the Co released by flow accelerated corrosion 2+ With the fluid into the downstream pipeline. Chelex-100 resin with its chelating group of high selectivity for transition metal ions, preferentially adsorbs Co in the solution 2 + , so that it is fixed in the pores of the resin. Since the chemical cross-linked structure of the resin does not significantly swell or decompose below 80°C, secondary pollution caused by the degradation of the adsorbent itself can be avoided. By periodically replacing the failed resin, it can continuously block 60 The Co isotope re-enters the fluid circulation system in the form of ions, thus eliminating its interference with the gamma-ray monitoring data.

[0075] Compared with the prior art, conventional ion exchange resins 5 have low adsorption selectivity for multivalent metal ions. For example, styrene resins tend to adsorb calcium and magnesium ions at the same time, resulting in a decrease in the retention efficiency of cobalt ions. However, Chelex-100 resin can still retain Co in complex solutions containing multiple cations through the stereochelation of the iminodiacetic acid group. 2+ The specific adsorption of cobalt ions can reach more than 2.0mmol / g.

[0076] Further optimization scheme, a thermometer 16 is connected inside the steam generator 2 to detect and display the technical scheme of the steam temperature during the experiment. The thermometer 16 is a sensing device for directly measuring the steam temperature, which can be implemented by a thermocouple or a thermal resistance temperature sensor, and is used to collect temperature data inside the steam generator 2 in real time. The steam generator 2 is a device that generates and maintains high-temperature and high-pressure wet steam, and can generate steam by electric heating or fuel combustion. The internal integrated thermometer 16 can eliminate external environmental interference.

[0077] Specifically, the thermometer 16 is installed in the internal cavity of the steam generator 2 by means of physical connection, and is in direct contact with the flowing steam medium. When the steam generator 2 is running, the temperature sensor senses the change in steam temperature in real time and transmits the temperature signal to an external display device. Since the thermometer 16 is located in the core area of steam generation, it can instantly reflect the actual temperature of the steam, avoiding the measurement delay caused by the long heat conduction path or the insulation layer of the equipment caused by the traditional external temperature measurement method. The experimenter dynamically adjusts the heating power or fluid circulation rate according to the displayed temperature data to ensure that the steam temperature is stable within the preset experimental range. This solution eliminates the error source of the intermediate heat transfer link by directly measuring the temperature inside the steam generator 2, and significantly improves the real-time and accuracy of temperature monitoring.

[0078] To further optimize the solution, a flowmeter 18 is provided on the pipeline from the steam generator 2 to the test pipe section 1 to measure the fluid velocity in the pipeline. The flowmeter 18 is a measuring device for obtaining the velocity parameters of the fluid in the pipeline, which can be implemented by a turbine flowmeter 18 or an ultrasonic Doppler flowmeter 18. The measuring probe is fixedly connected to the outer wall of the pipeline through a sealing flange, and the internal sensor element is in contact with the fluid. The flowmeter 18 is arranged in the straight pipe section between the outlet of the steam generator 2 and the inlet of the test pipe section 1. The fluid at this position is in a stable flow state, avoiding the flow velocity distribution distortion caused by the elbow or the reducer structure.

[0079] Specifically, when high-temperature and high-pressure wet steam flows through the pipeline, the fluid velocity is measured in real time by the flow meter 18 and converted into an electrical signal output. When the turbocharger module or the spray control unit of the fluid circulation system generates pressure fluctuations, the data output by the flow meter 18 will be fed back to the control system to maintain the stability of the preset flow rate by adjusting the pump power or spray volume. The flow rate parameters are synchronously transmitted to the dynamic decay correction algorithm module, and a time correlation is established with the activity change data collected by the gamma-ray monitoring system to eliminate the interference of the difference in the migration rate of corrosion products caused by the flow rate change on the thinning amount calculation.

[0080] In some specific embodiments, the impeller of the turbine flow meter 18 is made of Hastelloy to withstand high-temperature steam erosion, and its shaft is connected to an external Hall sensor through magnetic coupling to achieve non-contact speed measurement. The ultrasonic flow meter 18 adopts a cross-type sound wave transmitter and receiver arrangement to calculate the average flow rate by measuring the difference in sound wave propagation time in the downstream and upstream directions.

[0081] To further optimize the solution, a pressure gauge 17 is provided on the pipeline from the steam generator 2 to the test pipe section 1, which is used to detect and display the internal pressure of the pipeline. The pressure gauge 17 is a detection device for real-time detection of the internal pressure parameters of the pipeline. Specifically, it can be implemented by a mechanical pressure gauge 17 or an electronic pressure sensor. It is installed at the key node of the pipeline between the output end of the steam generator 2 and the inlet of the test pipe section 1, and can directly reflect the actual pressure state of the fluid before entering the test section. The pressure gauge 17 provides key data feedback for the stability control of the experimental conditions by dynamically monitoring the changes in pressure parameters.

[0082] In a further optimized solution, the pipeline at the front end of the water chemical adjustment system 15 is connected to the pipeline at the front end of the cobalt retention module through the re-purification loop 11. Specifically, the re-purification loop 11 is connected to the main circulation loop through the ball valve 10, so that the fluid can be directly bypassed to the re-purification loop 11 for treatment when necessary, and the Co in the fluid can be removed through the re-purification treatment of the cobalt retention module. 2+Ions and other corrosion products are prevented from accumulating in the system, thus avoiding interference with subsequent experimental results.

[0083] The further optimized solution also includes a regenerative heat exchanger 14 connected between the water chemistry regulation system 15 and the steam generator 2. The regenerative heat exchanger 14 is communicated with the steam generator 2 through the charging pipeline 12 and the discharging pipeline 13 to realize a heat cycle. The regenerative heat exchanger 14 can ensure that the fluid always remains within a suitable temperature and pressure range during the circulation process, support the recycling of the fluid, and improve the overall efficiency of the system.

[0084] The further optimized solution also has a pre-cooling device 19 connected to the loop between the test section 1 and the cobalt retention module for cooling the high-temperature and high-flow-rate fluid after the test. The pre-cooling device 19 can effectively reduce the temperature of the fluid and avoid affecting subsequent equipment. For example, precision measuring devices such as the conductivity meter 8 and the pH monitor 7 usually have strict requirements for the working temperature. The pre-cooling device 19 can prevent the high-temperature fluid from directly contacting these devices and avoid measurement errors or equipment damage caused by high temperature. Therefore, the pre-cooling device 19 is a crucial part of the system. It ensures the safe and stable operation of the entire system by effectively controlling the fluid temperature and avoids potential safety hazards caused by high temperature.

[0085] The embodiment of the present invention also provides a method for monitoring flow-accelerated corrosion thinning by the radioactive tracer method. Using the device for monitoring flow-accelerated corrosion thinning by the radioactive tracer method described in any one of the above, the method includes the following steps:

[0086] Before the experiment starts, measure the surface area of the test section 1, denoted as S (unit: m 2 ); record the pipe material density of the test section 1, denoted as ρ (unit: g / cm 3 ); determine the mass fraction of cobalt in the pipe material, denoted as w Co ; measure the initial total mass of radioactive cobalt ( 60 Co), denoted as m0 (unit: g); determine the 60 Co specific activity, denoted as S A (unit: Bq / g); calculate the 60 Co initial activity, denoted as A0, where A0 = S A ·m0.

[0087] After the experiment starts, the high-temperature and high-pressure wet steam flows into the test section 1 from below and out from above. After the temperature, flow rate, and pressure are all stable, start the flow-accelerated corrosion test. At this time, the timing is t0, and start measuring the counting rate corresponding to the initial activity of 60 Co in the test section, denoted as C0; at this time, the test section 1 is not corroded.

[0088] After the corrosion test is carried out to time t, the test section is measured again. 60 The counting rate corresponding to the Co activity is recorded as C(t); at this time, the test section is corroded. Since cobalt is evenly distributed on the surface of the pipe or is tightly combined with the substrate, the release rate of cobalt is proportional to the corrosion rate of the pipe, that is, the mass of cobalt released by corrosion Δm(t) is proportional to the total mass loss of the pipe Δm tube (t), Δm(t)∝Δm tube (t). The thickness loss Δd(t) and thinning rate R(t) of the pipe are:

[0089]

[0090] Taking into account the natural decay of radioactivity over time, the natural decay formula is:

[0091] A decay (t) = A0·e -λt

[0092] Among them, A decay (t) is the activity after time t, λ is the decay constant, λ=ln2 / T 1 / 2 , 60 The half-life of Co is T 1 / 2 is 5.27 years (46165 hours), so λ is 1.5×10 -5 h -1 ; t is the test running time (unit: hour).

[0093] The actual measured activity A measured (t) is the result of the combined effects of natural decay and corrosion release:

[0094]

[0095] Since the counting rate C measured by the detector is proportional to the activity, that is, C∝A, the counting rate C(t) measured after time t is:

[0096]

[0097] Total mass loss of pipe after time t Δm tube (t) is:

[0098]

[0099] Combining the above formulas, we can get the thickness loss Δd(t) and thinning rate R(t) of the tube as follows:

[0100]

[0101] The real-time monitoring formula derivation process includes:

[0102] 1. Decay correction and separation from corrosion release

[0103] The law of natural decay of radioactivity over time is (natural decay formula):

[0104] A decay (t) = A0·e -λt

[0105] where A decay (t) is the activity after time t; λ is the decay constant, ln2 / T 1 / 2 , T 1 / 2 is the half-life of the isotope, 5.27 years (46165 h), and λ can be obtained as 1.5×10 -5 h -1 ; t is the test running time (h).

[0106] 2. Activity loss due to corrosion release

[0107] The actually measured activity A measured (t) is the result of the combined action of natural decay and corrosion release:

[0108]

[0109] where Δm(t) is the mass of cobalt released due to corrosion at time t (g).

[0110] 3. Relationship between activity loss and counting rate

[0111] The counting rate C(t) measured by the detector is proportional to the activity:

[0112] C(t) = k·A measured (t)

[0113] Initial counting rate (t = 0, no corrosion):

[0114] C0 = k·A0

[0115] By combining, the decrease in counting rate due to corrosion release is obtained:

[0116]

[0117] 4. Calculation of corrosion mass loss

[0118] Mass of cobalt released due to corrosion (g):

[0119]

[0120] Total mass loss of the pipe (g):

[0121]

[0122] Mass loss per unit area of the pipe material (g / m 2 ):

[0123]

[0124] 5. Thickness loss and thinning rate

[0125] Thickness loss (mm):

[0126]

[0127] Thinning rate (mm / year) during the period from 0 to t:

[0128]

[0129] Example calculation:

[0130] Assume the pipe material is carbon steel with a density of 7.8 g / cm 3 , the surface area of the pipe section is 1 m 2 , the mass fraction of cobalt in the pipe material (w Co ) is 1%, the initial total mass of radioactive cobalt (m0) is 1 g, 60 the specific activity of Co (S A ) is 50 Bq / g, and the initial radioactive activity A0 can be obtained as 50 Bq. The initial counting rate C0 is measured as 10000, the test running time is 100 h, and the measured counting rate C(t) after the test is 8000.

[0131] The calculation steps are as follows:

[0132] Step 1. Mass of cobalt released by corrosion (g):

[0133]

[0134] Step 2. Total mass loss of the pipe material (g):

[0135]

[0136] Step 3. Mass loss per unit area of the pipe material (g / m 2 ):

[0137]

[0138] Step 4. Thickness loss (mm):

[0139]

[0140] Step 5. Instantaneous thinning rate (mm / year):

[0141]

[0142] Compared with the prior art, the embodiments of the present invention disclose at least the following beneficial effects:

[0143] The innovation of the present invention lies in the development of a real-time monitoring device for wall thickness reduction based on the radioactive cobalt ( 60 Co) tracer technique. This device realizes the online high-precision tracking of the wall thickness reduction rate under high-temperature and high-pressure environments by presetting 60 Co and detecting the change of γ-ray activity in real time, combining dynamic decay correction and corrosion release separation algorithms, and the response time can reach the second level. At the same time, there is no need to physically damage the specimen during the sampling and sample preparation processes.

[0144] The present invention adopts a cobalt retention module combining an ion exchange resin 5 and a filter 6, which can effectively block the 60 Co recycling interference and ensure the purity of the activity signal. In addition, by real-time monitoring the residual activity through a radioactive detector 9, the risk of radioactive leakage is greatly reduced, meeting the requirements of nuclear safety regulations.

[0145] The fluid circulation system and the test section adopt a standardized flange interface design, which can simulate the actual operating environment of the secondary loop of a nuclear power plant and support various flow conditions such as single-phase liquid flow and gas-liquid two-phase flow. At the same time, the test section adopts a detachable design and can be replaced as a whole, significantly improving the experimental efficiency.

[0146] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0147] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. An apparatus for monitoring flow-accelerated corrosion thinning by a radioactive tracer method, characterized in that Comprising: Test pipe section (1), the test pipe section (1) is uniformly embedded with radioactive 60 Co, the cobalt mass fraction of the test pipe section (1) is 0.1%-1.0%, and the test pipe section (1) is detachably connected to the pipeline; A fluid circulation system, connected to the upstream pipeline of the test pipe section (1), including a steam generator (2) and a turbocharging module, a fluid circulation pump, and a spray control unit integrated in the steam generator (2), for forming a simulated fluid at a preset temperature and pressure; A γ-ray monitoring system, including a plurality of NaI detectors arrayed on the test pipe section (1); The cobalt interception module is connected to the downstream pipeline of the test pipe section (1) and is used to block 60 the interference of Co recirculation; the cobalt interception module includes an ion exchange resin (5) and a filter (6), and the ion exchange resin (5) is used to adsorb Co in the solution 2+ , and the filter (6) intercepts cobalt-containing particles in the solution; An environmental detection module for monitoring pH value, conductivity, 60 Co residual activity is also connected to the downstream pipeline of the test pipe section (1), and a water chemistry regulation system (15) for maintaining experimental conditions based on the monitored values.

2. The device for monitoring flow-accelerated corrosion thinning by radioactive tracer method according to claim 1, characterized in that, A radioactive shielding device (4) is provided on the side of the test pipe section (1) away from the γ-ray monitoring system.

3. The device for monitoring flow-accelerated corrosion thinning by the radioactive tracer method according to claim 1, characterized in that, The radioactive 60 Co is incorporated through smelting or diffused into the test pipe section (1) by a high-temperature diffusion process.

4. The device for monitoring flow-accelerated corrosion thinning by radioactive tracer method according to claim 1, characterized in that, A repurification loop (11) is connected between the pipeline at the front end of the water chemistry regulation system (15) and the pipeline at the front end of the cobalt interception module.

5. The device for monitoring flow-accelerated corrosion thinning by the radioactive tracer method according to claim 4, wherein A ball valve (10) is installed on the pipeline at the front end of the water chemistry regulation system (15) to control the wet steam reflux. When 60 the residual activity of Co reaches a preset value, the valve closes to prevent the 60 Co content in the water chemistry loop from affecting the experimental results.

6. The device for monitoring flow-accelerated corrosion thinning by the radioactive tracer method according to claim 1, wherein The environmental detection module includes a pH monitor (7), a conductivity meter (8), and a radioactive detector (9), which are used to 60 accurately monitor the residual activity of 60 Co, ensure the reliability of experimental data, and strictly control radioactive risks.

7. The device for monitoring flow-accelerated corrosion thinning by the radioactive tracer method according to claim 1, characterized in that, It further includes a regenerative heat exchanger (14) connected between the water chemistry regulation system (15) and the steam generator (2), and the regenerative heat exchanger (14) is communicated with the steam generator (2) through a charging pipeline (12) and a discharging pipeline (13) to achieve a heat cycle.

8. A method for monitoring flow-accelerated corrosion thinning by radioactive tracer method, using the device for monitoring flow-accelerated corrosion thinning by radioactive tracer method according to any one of claims 1 to 7, characterized in that, Including the following steps: S1. Measure the surface area of the test pipe section (1), recorded as S; record the pipe density of the test pipe section (1), recorded as ρ; determine the mass fraction of cobalt in the pipe, recorded as w Co ;Measure radioactivity 60 The initial total mass of Co is denoted as m0; determine 60 Co specific activity, denoted as S A ;calculate 60 The initial activity of Co is denoted as A0, where A0 = S A m0; S2. The high-temperature and high-pressure wet steam flows into the test pipe section (1) from below and out from above. After the temperature, flow rate, and pressure are all stable, the flow-accelerated corrosion test is started. At this time, the timing is t0, and the measurement of 60 the counting rate corresponding to the initial activity of Co is started and denoted as C0; After the corrosion experiment has been carried out for a time t, the count rate corresponding to the Co activity in the test section is measured again 60 and denoted as C(t); S4. According to the dynamic decay correction and corrosion release separation algorithm, calculate the thickness loss Δd(t) and the thinning rate R(t) of the pipe material.

9. The method for monitoring flow-accelerated corrosion thinning by radioactive tracer method according to claim 8, characterized in that, The dynamic decay correction and corrosion release separation algorithm includes the following steps: S41. Calculate the activity A after time t according to the natural decay formula decay (t): A decay (t) = A0·e -λt Among them, A decay (t) is the activity after time t; λ is the decay constant, ln2 / T 1 / 2 , T 1 / 2 is the half-life of the isotope, 5.27 years (46165 h), and λ can be obtained as 1.5×10 -5 h -1 ; t is the test running time; S42. Calculate the activity loss caused by corrosion release based on the actually measured activity A measured (t) and the natural decay activity A decay (t). S43. According to the relationship that the counting rate C measured by the detector is proportional to the activity, calculate the decrease in the counting rate caused by corrosion release; S44. Calculate the total mass loss of the pipe according to the proportional relationship between the mass of cobalt Δm(t) released by corrosion and the total mass loss Δm of the pipe. The formula is as follows: tube(t) ​ S45. Calculate the thickness loss Δd(t) and the thinning rate R(t) of the pipe material according to the total mass loss of the pipe material, and the formula is:

10. The method for monitoring flow-accelerated corrosion thinning by the radioactive tracer method according to claim 8, wherein The radioactive detector (9) monitors in real time 60 the residual activity of 60 Co. When the residual activity reaches the preset value, the ball valve (10) is closed to prevent the Co content in the water chemical loop from affecting the experimental results.

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