A device for on-line measurement of surface scale on fuel cladding tubes based on radioisotope tracing

Abstract

This invention relates to the interdisciplinary field of nuclear reactor engineering and corrosion engineering, and in particular to an online measurement device for fouling on the surface of fuel cladding tubes based on radioactive isotope tracing, comprising: an injection control module for injecting radioactive... 59 Fe solution was added to the coolant, and the effect of Fe ion concentration on the coolant was analyzed. 59 Fe content is regulated and controlled; experimental module for use based on injected radioactivity. 59 The Fe solution coolant was used to test the fuel cladding surface; a measurement module was used to collect data on the scale that formed on the fuel cladding surface after the test. 59 Fe radioactivity is used to estimate the surface density of the deposited scale. This invention controls the amount of Fe in the coolant... 59 The Fe content, and its effect on the scale buildup on the fuel cladding surface. 59 Online detection of Fe radioactivity can accurately calculate the corresponding 59 The Fe mass is used to infer the scale mass, and the scale information on the surface of the cladding tube is obtained in real time to reflect the dynamic changes of scale in a timely manner.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear reactor engineering and corrosion engineering, in particular to a fuel cladding tube surface scale online measurement device based on radioactive isotope tracing. BACKGROUND

[0002] The pressurized water reactor primary fuel cladding tube is the first barrier of the pressurized water reactor protection, which prevents the leakage of the reactor core radioactivity while transmitting the large amount of heat released by the nuclear reaction of the reactor core to the outside, and bears the corrosion of high-temperature and high-pressure water. During the long-term operation of the nuclear power plant, the corrosion products of the cladding tube deposit, and the deposition of the scale on the surface of the cladding tube causes the problem of heat conduction performance degradation and corrosion product activation. With the increase of the thickness of the deposited scale, the heat conduction performance decreases, the heat of the reactor core cannot be timely discharged, which leads to the increase of the temperature of the reactor core and further causes the safety problem of the reactor core. Therefore, online detection of the surface scale of the fuel cladding tube is the key to improve the safety of the reactor operation and the service life of the cladding tube.

[0003] The method for detecting the scale usually includes scanning electron microscopy, capacitance method and concentration calculation method. The scanning electron microscopy method for measuring the surface scale of the pressurized water reactor primary fuel cladding tube needs to stop the reactor, take out the fuel cladding tube and cut the cross section, and then the cross section morphology is photographed by a microscope to directly measure the thickness of the scale. However, this method is a destructive detection method, the cladding tube after cutting cannot continue to serve, and only the scale at a single time point can be obtained, which has certain limitations and lacks continuous detection of the scale of the fuel cladding tube. The capacitance method is to place a detection plate on the surface of the measured object. The scale with a certain thickness pollutes the front side scale line of the detection plate, which causes the change of the capacitance. The capacitance change data between the metal electrode plates are collected by a capacitance sensor detector and an LCR bridge digital detector, and the thickness of the scale is calculated. The disadvantage is that it can only detect the scale on the surface of the non-metal material, and the fuel cladding tube is zirconium alloy. Therefore, this method is not suitable for detecting the surface scale of the fuel cladding tube. The concentration calculation method is to detect the pH value and boron concentration of the coolant, predict the stable phase iron-nickel oxide generated on the surface of the cladding tube under the current operating condition, calculate the particle size and concentration of the iron-nickel oxide particles, and calculate the thickness of the scale by the corresponding formula. This method completely relies on theoretical calculation. However, the surface scale of the cladding tube is a complex behavior affected by water chemistry, material and thermal hydraulic together, and the reliability and application range of the theoretical calculation have obvious defects. Therefore, the present application provides a fuel cladding tube surface scale online measurement device based on radioactive isotope tracing. SUMMARY

[0004] The present application aims to provide a fuel cladding tube surface scale online measurement device based on radioactive isotope tracing, which contains radioactive elements 59The corrosion products of Fe are injected into the primary coolant, and the deposits are detected by a scintillation detector containing NaI(Tl) crystals and a photomultiplier tube. 59 The gamma rays generated by Fe decay are collected to measure the radioactivity of the gamma rays and calculate the scale buildup, enabling online monitoring of scale buildup on the fuel cladding surface.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] An online fouling measurement device for fuel cladding pipe surface based on radioactive isotope tracing includes:

[0007] Injection control module, used for injecting radioactivity 59 Fe solution was added to the coolant, and the effect of Fe ion concentration on the coolant was analyzed. 59 Fe content is regulated and controlled;

[0008] Experimental module for use based on injected radioactivity 59 Fe solution was used as a coolant to test the surface of the fuel cladding.

[0009] The measurement module is used to collect data on the fouling deposits generated on the surface of the fuel cladding after the test. 59 Fe radioactivity, used to estimate the surface density of the deposited scale.

[0010] Optionally, the injection control module includes: a booster injection pump, a high-temperature and high-pressure circuit, a preheater, a power circulation pump, a back pressure relief valve, and a water chemistry detection unit;

[0011] The radioactivity 59 Fe solution is injected into the high-temperature, high-pressure circuit via the booster injection pump. The coolant in the high-temperature, high-pressure circuit circulates under the drive of the power circulation pump, and the coolant flows into the water chemistry detection unit at a preset flow rate controlled by the back pressure relief valve. The Fe ion concentration in the coolant is determined by conductivity measurement and ICP-MS analysis. Combined with the flow control of the booster injection pump, the solution is used to monitor the high-temperature, high-pressure circuit. 59 Fe content is adjusted via feedback;

[0012] After the coolant has been regulated, it is heated to a preset temperature by the preheater and then enters the test module.

[0013] Optionally, the test module includes: a pipe, an upper sealing element, a lower sealing element, a fuel casing, and an inner heating rod, wherein the pipe is arranged on the left and right sides, and the upper and lower sealing elements are arranged on the upper and lower sides to form a frame structure; the inner heating rod is placed inside the fuel casing, and the fuel casing is placed inside the frame structure; the upper and lower sealing elements are detachable for inserting and removing the fuel casing and the inner heating rod.

[0014] Optionally, the measuring module comprises a radiation detection device, a moving guide rail and a data acquisition unit, wherein the radiation detection device is connected with the moving guide rail through a tube base, and is used for periodically detecting the radioactive activity of Fe decay and the mass area density of the accumulated scale in different areas. 59 Optionally, the radiation detection device comprises a collimator, a scintillation detector and a photomultiplier tube, wherein the γ rays generated by Fe in the accumulated scale pass through the collimator, the γ rays of horizontal angle are screened out and then penetrate to the scintillation detector, fluorescence photons are generated and reflected to the photomultiplier tube, photoelectrons are generated and the photoelectric signal is amplified by multiplication. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal.

[0015] Optionally, the radiation detection device comprises a collimator, a scintillation detector and a photomultiplier tube, wherein the γ rays generated by Fe in the accumulated scale pass through the collimator, the γ rays of horizontal angle are screened out and then penetrate to the scintillation detector, fluorescence photons are generated and reflected to the photomultiplier tube, photoelectrons are generated and the photoelectric signal is amplified by multiplication. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal.

[0016] Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal.

[0017] Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal.

[0018] Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal.

[0019] Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal.

[0020]

[0021] Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal. Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal.

[0022] Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal. 59 Optionally, the data acquisition unit calculates the radioactive activity of Fe decay and the mass area density of the accumulated scale by using the photoelectric signal.

[0023]

[0024] Where w is the amount of fouling on the surface of the fuel cladding. 59 The mass surface density of Fe, where a is the collimator width, b is the collimator length, and d is the fuel cladding diameter.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention contains radioactive elements 59 The corrosion products of Fe are injected into the primary coolant, and the deposits are detected by a scintillation detector containing NaI(Tl) crystals and a photomultiplier tube. 59 By collecting the gamma rays generated by Fe decay and calculating the radioactivity of gamma rays, the scale quality can be estimated. This allows for real-time acquisition of scale information on the surface of the cladding tube, timely reflection of the dynamic changes in scale, and online monitoring of scale on the fuel cladding surface.

[0027] This invention enhances the spatial flexibility of the radiation detector by using a movable guide rail, enabling omnidirectional detection of fuel cladding deposits. The collimator mounted in front of the scintillation detector filters rays at specific angles, reducing interference from rays in other directions on the detection area. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of an online scale measurement device for the surface of fuel cladding tubes based on radioactive isotope tracing, according to an embodiment of the present invention. Wherein, 1-1: radioactive... 59 Fe solution, 1-2: booster injection pump, 1-3: high temperature and high pressure circuit, 1-4: preheater, 1-5: power circulation pump, 1-6: back pressure relief valve, 1-7: water chemistry detection unit, 2-1: test section pipeline, 2-2: upper end seal of test section, 2-3: lower end seal of test section, 2-4: fuel cladding, 2-5: internal heating rod, 3-1: collimator, 3-2: NaI(Tl) crystal, 3-3: nickel-iron alloy barrier, 4-1: photocathode, 4-2: focusing electrode, 4-3: dinter electrode, 4-4: shielding plate, 4-5: anode, 5-1: moving guide rail, 5-2: data acquisition unit;

[0030] Figure 2 This is a schematic diagram of the detection area according to an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] This embodiment provides an online measurement device for fouling on the surface of fuel cladding tubes based on radioactive isotope tracing, including:

[0034] Injection control module, used for injecting radioactivity 59 Fe solution was added to the coolant, and the effect of Fe ion concentration on the coolant was analyzed. 59 Fe content is regulated and controlled;

[0035] Experimental module for use based on injected radioactivity 59 Fe solution was used as a coolant to test the surface of the fuel cladding.

[0036] The measurement module is used to collect data on the fouling deposits generated on the surface of the fuel cladding after the test. 59 Fe radioactivity, used to estimate the surface density of the deposited scale.

[0037] Specifically, this embodiment uses radioactive isotopes. 59 Fe serves as a tracer element and is also a source of corrosion products in the primary coolant and fuel cladding of pressurized water reactors. Its characteristic of depositing fouling on the fuel cladding surface allows for the control of a constant concentration of Fe in the coolant. 59 Fe content, detected in scale 59 Fe radioactivity is used to estimate the surface density of scale buildup, thereby enabling online monitoring of scale buildup.

[0038] Furthermore, the injection control module includes: a booster injection pump, a high-temperature and high-pressure circuit, a preheater, a power circulation pump, a back pressure relief valve, and a water chemistry detection unit;

[0039] The radioactivity 59 Fe solution is injected into the high-temperature, high-pressure circuit via the booster injection pump. The coolant in the high-temperature, high-pressure circuit circulates under the drive of the power circulation pump, and the coolant flows into the water chemistry detection unit at a preset flow rate controlled by the back pressure relief valve. The Fe ion concentration in the coolant is determined by conductivity measurement and ICP-MS analysis. Combined with the flow control of the booster injection pump, the solution is used to monitor the high-temperature, high-pressure circuit. 59Fe content is adjusted via feedback;

[0040] After the coolant has been regulated, it is heated to a preset temperature by the preheater and then enters the test module.

[0041] Furthermore, the test module includes: a pipe, an upper sealing element, a lower sealing element, a fuel casing, and an inner heating rod. The pipe is arranged on the left and right sides, and the upper and lower sealing elements are arranged on the upper and lower sides to form a frame structure. The inner heating rod is placed inside the fuel casing, and the fuel casing is placed inside the frame structure. The upper and lower sealing elements are detachable for inserting and removing the fuel casing and the inner heating rod.

[0042] Furthermore, the measurement module includes: a radiation detection device, a moving guide rail, and a data acquisition unit, wherein the radiation detection device is connected to the moving guide rail via a tube socket and is used to periodically detect the amount of deposits in different areas. 59 Fe generates gamma rays, which are processed into photoelectric signals and transmitted to the data acquisition unit for calculation. 59 Radioactivity of Fe decay and surface density of deposits.

[0043] Furthermore, the radiation detection device includes: a collimator, a scintillation detector, and a photomultiplier tube, wherein the accumulated dirt... 59 The gamma rays generated by Fe pass through the collimator, and the horizontal gamma rays are filtered out before penetrating the scintillation detector, generating fluorescent photons, which are then reflected to the photomultiplier tube to generate photoelectrons and amplify the photoelectric signal.

[0044] Furthermore, the data acquisition unit calculates 59 The radioactivity of Fe decay and the surface density of the deposit include:

[0045] Calculation based on the photoelectric signal 59 The radioactivity of Fe decay, after deducting 59 The basic background activity of Fe decay is used to obtain the effective radioactivity.

[0046] Based on the effective radioactivity, the deposition on the fuel cladding surface is calculated. 59 Fe mass, combined with collimator and fuel cladding diameter, is used to estimate the scale buildup on the fuel cladding surface. 59 Mass surface density of Fe.

[0047] Furthermore, based on the effective radioactivity, the deposition on the fuel cladding surface is calculated. 59 Fe mass includes:

[0048]

[0049] Wherein, W(T) represents the amount of fuel deposited on the surface of the fuel cladding during time period T. 59 The total mass of Fe, where m is the mass of each atom, A(t) is the effective radioactivity at time t, and A(T) is the effective radioactivity over time period T. It is the half-life, and ln2 is the natural logarithm of 2.

[0050] Furthermore, by combining the collimator and fuel cladding diameter dimensions, the surface fouling on the fuel cladding can be estimated. 59 The mass surface density of Fe includes:

[0051]

[0052] Where w is the amount of fouling on the surface of the fuel cladding. 59 The mass surface density of Fe, where a is the collimator width, b is the collimator length, and d is the fuel cladding diameter.

[0053] The following is combined with Figure 1 , Figure 2 This embodiment provides a detailed description of an online scale measurement device for fuel cladding tubes based on radioactive isotope tracing, as follows:

[0054] The injection control module includes: radioactivity 59 Fe solution 1-1, booster injection pump 1-2, high temperature and high pressure circuit 1-3, preheater 1-4, power circulation pump 1-5, back pressure relief valve 1-6, water chemistry detection unit 1-7.

[0055] Constant concentration of radioactivity 59 Fe solution 1-1 is injected into the high-temperature, high-pressure circuit 1-3 via booster injection pump 1-2, serving as a source of corrosion products. The coolant in the high-temperature, high-pressure circuit 1-3 circulates under the drive of the power circulation pump 1-5. A small amount of coolant flows into the water chemistry detection unit 1-7 under the control of the back pressure relief valve 1-6. The Fe ion concentration is determined by conductivity measurement and ICP-MS analysis. Combined with the flow control of the booster injection pump 1-2, the high-temperature, high-pressure circuit 1-3 is regulated. 59 Feedback regulation of Fe content.

[0056] In the high-temperature and high-pressure circuit 1-3, most of the coolant is heated to the specified temperature after passing through the preheater 1-4 and then enters the test module.

[0057] The test module includes: test section pipe 2-1, test section upper end seal 2-2, test section lower end seal 2-3, fuel casing 2-4, and inner heating rod 2-5. The test section upper end seal 2-2 and test section lower end seal 2-3 can be disassembled to allow the fuel casing 2-4 and inner heating rod 2-5 to be inserted and removed.

[0058] The measuring module comprises a radiation detection device, a moving guide rail 5-1 and a data acquisition unit 5-2, and the radiation detection device is composed of a collimator 3-1, a scintillation detector and a photomultiplier tube.

[0059] The collimator 3-1 is made of lead-tungsten alloy and is cast by folding around, which is located in front of the CZT crystal and is used for limiting the direction and range of the gamma rays entering the crystal.

[0060] The scintillation detector is a sodium iodide (NaI) crystal doped with thallium (Tl), i.e. a NaI (Tl) crystal 3-2, which can generate photons under the action of gamma rays.

[0061] The photomultiplier tube is composed of a photocathode 4-1, a focusing electrode 4-2, a dynode 4-3, a shield plate 4-4 and an anode 4-5.

[0062] The radiation detection device is further wrapped by a nickel-iron alloy barrier 3-3 outside, which provides a low magnetic resistance path to guide the magnetic field lines to bypass the inside of the photomultiplier tube, so as to protect the photomultiplier tube from the interference of the strong magnetic field.

[0063] The bottom of the radiation detection device is connected with the moving guide rail 5-1 through a tube seat, and is connected with the data acquisition unit 5-2 through a data line.

[0064] The coolant flows through the surface of the heated fuel cladding, and the corrosion product source term in the coolant 59 Fe deposits on the surface of the fuel cladding and forms a certain thickness of Fe-containing 59 Fe scale.

[0065] 59 Fe undergoes beta decay (half-life of 44.495 days) and decays into 59 Co, and then reaches a stable state accompanied by the emission of gamma rays, releasing 56.59% of 1.0993 MeV photons and 43.21% of 1.2916 MeV photons (high-penetration gamma rays).

[0066] On the outside of the test section pipe 2-1, a scintillation detector for detecting gamma rays is arranged. 59 Fe in the scale produces high-energy gamma rays, which pass through the collimator 3-1 in front of the scintillation detector, screening out the gamma rays at the horizontal angle to avoid the interference of the gamma rays from the scale at the upper and lower ends of the test section. After the gamma rays penetrate into the NaI (Tl) crystal 3-2 in the scintillation detector, the molecules obtain energy excitation, and fluorescence photons are generated when the excitation is deactivated. The photons are reflected by the reflection layer, reach the photocathode 4-1 of the photomultiplier tube, and generate photoelectrons through photoelectric effect. After passing through the focusing electrode 4-2, the photoelectrons are converged into a narrower beam, and the photoelectric signal is amplified by the dynode 4-3 after the photoelectron multiplication. The data acquisition unit 5-2 acquires the electric signal to calculate 59 the radioactivity of the decayed Fe.

[0067] Excluding the coolant when not heated 59 The baseline background activity for Fe decay is used to determine the deposition on the surface of the fuel cladding in the test section. 59 The radioactivity of Fe is calculated using the following formula for the deposition that occurs after time T. 59 Fe mass:

[0068]

[0069] Where m is the mass of each atom, and A(t) is the effective radioactivity at time t. It is the half-life.

[0070] The above formula gives the deposition that occurs on the surface of the fuel cladding within time T. 59 The total mass of Fe, including the amount that has decayed in the scale. 59 Fe atoms and still present in the grime 59 Number of Fe atoms

[0071] Based on the scale buildup on the fuel coating surface 59 The mass of Fe and the collimator 3-1, along with the diameter of the fuel cladding, can be used to estimate the scale buildup on the surface of the fuel cladding. 59 Mass surface density of Fe. For example Figure 2 As shown, assuming the collimator 3-1 has a width of a, a length of b, and a fuel cladding diameter of d, the arc length of the detection area of ​​the collimator 3-1 directly facing the fuel cladding is:

[0072]

[0073] The area of ​​the detection zone is:

[0074]

[0075] The amount of dirt per unit area in the test area 59 The mass of Fe is:

[0076]

[0077] The above formula gives the value of the scale calculated from the radioactivity. 59 The mass surface density of Fe. 59 The mass fraction of Fe in the deposits can be used to obtain the surface density of the deposits in real time. During the experiment, the deposit condition in different areas is periodically detected by moving the guide rail, allowing for a comprehensive analysis of the deposit condition of the entire fuel cladding. In addition, after the experiment, the cladding tube can be removed for destructive testing of the surface dirt to obtain the composition, density, and thickness of the dirt, enabling verification and correction of the test results.

[0078] The device provided in the embodiment can control the content of Fe in the coolant 59 Fe, and detect the radioactivity of Fe in the surface scale of the fuel cladding, calculate the corresponding mass of Fe, further infer the mass of the scale, and obtain the scale information of the surface of the cladding tube in real time, and reflect the dynamic change of the scale in time. 59 59 The device provided in the embodiment can control the content of Fe in the coolant

[0079] The device provided in the embodiment can control the content of Fe in the coolant

[0080] The above-described embodiments are only descriptions of the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements to the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.​

Claims

1. An online measurement device for fouling on the surface of fuel cladding pipe based on radioactive isotope tracing, characterized in that, include: Injection control module, used for injecting radioactivity 59 Fe solution was added to the coolant, and the effect of Fe ion concentration on the coolant was analyzed. 59 Fe content is regulated and controlled; Experimental module for use based on injected radioactivity 59 Fe solution was used as a coolant to test the surface of the fuel cladding. The measurement module is used to collect data on the fouling deposits generated on the surface of the fuel cladding after the test. 59 Fe radioactivity, used to estimate the surface density of the accumulated scale; The measurement module includes a radiation detection device, a moving guide rail, and a data acquisition unit. The radiation detection device is connected to the moving guide rail via a tube socket and is used to periodically detect the amount of deposits in different areas. 59 Fe generates gamma rays, which are processed into photoelectric signals and transmitted to the data acquisition unit for calculation. 59 The radioactivity of Fe decay and the surface density of the deposit mass; The data acquisition unit calculates 59 The radioactivity of Fe decay and the surface density of the deposit include: Calculation based on the photoelectric signal 59 The radioactivity of Fe decay, minus 59 The basic background activity of Fe decay is used to obtain the effective radioactivity. Based on the effective radioactivity, the deposition on the fuel cladding surface was calculated. 59 Fe mass, combined with collimator and fuel cladding diameter, is used to estimate the scale buildup on the fuel cladding surface. 59 Mass surface density of Fe.

2. The online measurement device for fouling on the surface of fuel cladding tubes based on radioactive isotope tracing as described in claim 1, characterized in that, The injection control module includes: a booster injection pump, a high-temperature and high-pressure circuit, a preheater, a power circulation pump, a back pressure relief valve, and a water chemistry detection unit; The radioactivity 59 Fe solution is injected into the high-temperature, high-pressure circuit via the booster injection pump. The coolant in the high-temperature, high-pressure circuit circulates under the drive of the power circulation pump, and the coolant flows into the water chemistry detection unit at a preset flow rate controlled by the back pressure relief valve. The Fe ion concentration in the coolant is determined by conductivity measurement and ICP-MS analysis. Combined with the flow control of the booster injection pump, the solution is used to monitor the high-temperature, high-pressure circuit. 59 Fe content is adjusted via feedback; After the coolant has been regulated, it is heated to a preset temperature by the preheater and then enters the test module.

3. The online measurement device for fouling on the surface of fuel cladding tubes based on radioactive isotope tracing as described in claim 1, characterized in that, The test module includes: a pipe, an upper sealing element, a lower sealing element, a fuel casing, and an inner heating rod. The pipe is arranged on the left and right sides, and the upper and lower sealing elements are arranged on the upper and lower sides, forming a frame structure. The inner heating rod is placed inside the fuel casing, and the fuel casing is placed inside the frame structure. The upper and lower sealing elements are detachable for inserting and removing the fuel casing and the inner heating rod.

4. The online measurement device for fouling on the surface of fuel cladding tubes based on radioactive isotope tracing as described in claim 1, characterized in that, The radiation detection device includes: a collimator, a scintillation detector, and a photomultiplier tube, wherein, in the accumulated dirt... 59 The gamma rays generated by Fe pass through the collimator, and the horizontal gamma rays are filtered out before penetrating the scintillation detector, generating fluorescent photons, which are then reflected to the photomultiplier tube to generate photoelectrons and amplify the photoelectric signal.

5. The online measurement device for fouling on the surface of fuel cladding pipe based on radioactive isotope tracing according to claim 1, characterized in that, Based on the effective radioactivity, the deposition on the fuel cladding surface was calculated. 59 Fe mass includes: ； in, For fuel cladding surface deposition during time period T 59 Total mass of Fe, It is the mass of each atom. It is the effective radioactivity at time t. This refers to the effective radioactivity during time period T. It is the half-life. It is the natural logarithm of 2.

6. The online measurement device for fouling on the surface of fuel cladding tubes based on radioactive isotope tracing according to claim 5, characterized in that, Based on the collimator and fuel cladding diameter, the surface fouling of the fuel cladding can be estimated. 59 The mass surface density of Fe includes: ； in, It is the scale buildup on the surface of the fuel cladding 59 Mass surface density of Fe a It is the collimator width. b It is the collimator length. d It is the diameter of the fuel cladding.

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