Nuclear fuel damage detecting and positioning method

Abstract

The invention discloses a nuclear fuel damage detection and positioning method, and the method comprises the following steps: S100, carrying out the classified coding of a plurality of fuel elements of a reactor core, and enabling the codes of the fuel elements of each heat of the reactor core not to be repeated; s200, selecting different tracers for the fuel elements with different codes of the same heat, wherein the tracers comprise at least one tracing element; s300, filling the fuel rods of the same fuel element with the same tracer in the fuel assembly process of the reactor core; and S400, sampling and detecting fluid of the primary loop of the reactor, judging whether the fuel elements are damaged or not according to a detection result, and confirming the positions and the number of the damaged fuel elements. According to the method, the tracer is firstly filled into the fuel element, and then the loop is sampled and detected, so that whether the fuel element is damaged or not is accurately judged under the condition of no shutdown, and the position of the damaged fuel element is confirmed.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear fuel detection, and particularly to a method for detecting and positioning nuclear fuel breakage. Background Art

[0002] During the operation of nuclear power plants, the first line of defense for nuclear power safety, that is, the cladding of nuclear fuel elements, is damaged due to many reasons, causing the harmful radioactive substances originally enclosed in the cladding to spill out and enter the cooling water in the primary loop, resulting in nuclear radioactive safety hazards. There are various reasons for such accidents; for example, quality defects in the manufacture of the element cladding, damage caused by foreign object impacts, thermal stress damage caused by temperature changes, vibration damage caused by fluids between the fixed grids of the fuel assembly and the periphery of the fuel rod, weakening of the cladding strength after physical and chemical reactions between the inside of the cladding and the fuel pellets, damage caused by the pressure generated by the gas generated by the nuclear fuel atom fission in the cladding, the impact of hydrogen embrittlement on the cladding strength formed by the corrosion products in the water or the hydrides generated by the water itself on the external alloy material of the cladding, and so on.

[0003] Currently, during the operation of the reactor, the technical means for detecting the breakage of the fuel cladding is to regularly sample the cooling water in the primary loop. After the fuel element is damaged, the fission products enter the primary loop. Samples are taken from the primary loop and subjected to radiochemical analysis. Based on the analysis results, it is judged by experience whether the cladding is damaged. Since there are dozens of chemical elements in the analysis results of the samples, and due to the diversity of the reasons for breakage and the wide range of positions of the damaged elements, it is very uncertain to judge whether the fuel element cladding is damaged only based on the radiochemical analysis results of the samples, and the element cannot be located either. And other technical means that can definitely detect breakage require stopping the nuclear reaction before they can be carried out, that is, power generation must be stopped first. However, a shutdown inspection means that huge economic losses may be incurred. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for detecting and positioning nuclear fuel breakage.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a method for detecting and positioning nuclear fuel breakage, which includes the following steps:

[0006] S100. Classify and code several fuel elements in the reactor core, and the codes of the fuel elements in each batch of the reactor core are not repeated;

[0007] S200. Select different tracers for fuel elements with different codes in the same batch, and the tracer includes at least one tracer element;

[0008] S300. During the fuel assembly process in the reactor core, the same tracer is filled into the fuel rods of the same fuel element;

[0009] S400. Sample and detect the fluid in the primary loop of the reactor, and determine whether the fuel element is damaged according to the detection results, and confirm the position and quantity of the damaged fuel element.

[0010] In some embodiments, in step S100, several fuel elements have different enrichments, and the several fuel elements are classified and coded according to the enrichment.

[0011] In some embodiments, in step S200, the tracer includes a tracer element, the tracer element has at least two isotopes, and different isotopes have different abundances.

[0012] In some embodiments, the tracer consists of one isotope; or, the tracer consists of at least two isotopes, and the contents of at least two isotopes in different tracers are different from each other.

[0013] In some embodiments, in step S200, the tracer includes a compound composed of at least two tracer elements, at least one tracer element has at least two isotopes, and different isotopes have different abundances.

[0014] In some embodiments, in different tracers, the contents of at least two isotopes in at least one tracer element are different from each other.

[0015] In some embodiments, in step S200, the tracer element is different from the original elements of the reactor, the tracer element is different from the activation products of the reactor, and the tracer element is different from the elements generated by the fission of uranium oxide.

[0016] In some embodiments, in step S300, the fuel rod includes a cladding, an upper end plug, a lower end plug, and fuel pellets. The upper end plug and the lower end plug are respectively fitted with both ends of the cladding to form a sealed space inside the cladding; the fuel pellets are located inside the cladding, and a cavity is formed between the upper end plug and the fuel pellets, and the tracer is filled in the cavity.

[0017] In some embodiments, in step S300, the fuel rod further includes a spring provided inside the cladding. One end of the spring abuts against the bottom of the upper end plug, and the other end abuts against the top of the fuel pellets. The bottom of the fuel pellets abuts against the top of the lower end plug; the tracer is filled inside the cladding and is located around the spring.

[0018] In some embodiments, in step S400, the fluid in the primary loop of the reactor is sampled, and a corresponding detection method is selected according to the tracer element of the tracer; if the tracer element is detected, it is determined that the fuel element is damaged, and according to the composition of the tracer element, the position and quantity of the damaged fuel element are confirmed; if the tracer element is not detected, resampling and detection are performed.

[0019] In some embodiments, in step S400, if the tracer element is detected, the leaked tracer is determined according to the type of the tracer element or its isotope and the content ratio between the isotopes in different tracer elements, and the position and quantity of the damaged fuel element are confirmed according to the tracer.

[0020] In some embodiments, in step S400, according to the radioactive level of the primary loop of the reactor, the fluid in the primary loop of the reactor is sampled regularly, and the sampling period is 12h to 36h.

[0021] Advantages of the present invention: The nuclear fuel damage detection and positioning method of the present invention classifies and codes the fuel elements in the reactor core, selects different tracers for different fuel elements, fills the tracer in the fuel rods of the fuel elements, samples and detects the primary loop of the reactor, so as to realize non-invasive detection, accurately judge whether the fuel element is damaged without shutting down the reactor, and confirm the position of the damaged fuel element, reducing the economic losses of shutdown inspection and maintenance. Description of the Drawings

[0022] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0023] Figure 1 is a flowchart of the nuclear fuel damage detection and positioning method in some embodiments of the present invention. Detailed Embodiments

[0024] For a clearer understanding of the technical features, objectives and effects of the present invention, the specific embodiments of the present invention will be described in detail below in conjunction with the drawings.

[0025] It should be noted that the flowcharts shown in the drawings are only illustrative and not necessarily include all the contents and operations / steps, nor are they necessarily executed in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may be changed according to the actual situation.

[0026] It should also be noted that, unless otherwise clearly specified and limited, terms such as "installation", "connection", "linkage", "fixation", "setting" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. When a component is referred to as "on" or "under" another component, the component can be "directly" or "indirectly" located above the other component, or there may also be one or more intermediate components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] Figure 1 Some embodiments of the present invention are shown for a method for detecting and locating nuclear fuel damage, which can be used for detecting and locating damage of fuel elements in the reactor core of a nuclear power plant. The method for detecting and locating nuclear fuel damage of the present invention includes the following steps:

[0028] S100. Classify and code a number of fuel elements in the reactor core, and the codes of the fuel elements for each cycle in the reactor core are not repeated.

[0029] In some embodiments, a number of fuel elements have different enrichment degrees, and the number of fuel elements is classified and coded according to the enrichment degree, where the enrichment degree refers to the mass fraction of U-235 (uranium-235) in nuclear fuel. In other embodiments, classification and coding can be performed according to the manufacturer and batch of the fuel elements. For example, according to the factory code of the fuel element, in refueling, the positions of the respective fuel elements in each cycle core are respectively corresponding to the codes of the respective fuel elements. For example, the N05 position in the AN02 cycle of the core corresponds to the code of a fuel element.

[0030] The coding of each fuel element corresponds to the tracer filled in the fuel element. The total number of codings is greater than the total number of tracers, and it is necessary to ensure that the codings of all fuel elements in each operating cycle are non-repetitive. Then, theoretically, the minimum total number of non-repetitive codings N = the number of fuel elements M in the core per cycle. For example, if the number of fuel elements M in the core per cycle = 177, then theoretically the minimum total number of non-repetitive codings N = 177. Specifically, for example, when replacing 1 / 3 of the fuel elements during each refueling, the core is divided into three regions according to the positions of 177 fuel element assemblies, namely Region A, Region B, and Region C, with 59 fuel element assemblies in each region. The three regions correspond to Ux, Vx, and Wx codings (x is from 1 to 59, corresponding to different 59 codings). During refueling in a certain cycle, the spent fuel with Ux coding in Region A is removed, and the newly loaded fuel element with Ux' coding is replaced into Region C. The fuel element with Vx coding in Region B from the previous cycle is replaced into Region A, and the fuel element with Wx coding in Region C from the previous cycle is replaced into Region B. Correspondingly, the Ux' coding of the newly loaded fuel element corresponds to the position of Region C in the core, the Vx coding of the fuel element corresponds to the position of Region A in the core, and the Wx coding of the fuel element corresponds to the position of Region B in the core. Thus, different positions in the core of different cycles correspond to different fuel element codings, and when fuel damage occurs, the position of the damaged fuel element can be accurately located. When the replaced Ux coding is the same as the newly loaded Ux' coding, the minimum total number of codings is 177; if the Ux coding is different from the newly loaded Ux' coding, the total number of codings at this time is 177 + 59 = 236. According to the total number of fuel elements in different cores (such as 157 assemblies, 177 assemblies, 193 assemblies, etc.), when loading fuel in each cycle, select the number of tracer combinations greater than or equal to the total number of fuel elements.

[0031] An operating cycle refers to a fuel cycle, that is, the reactor starts from startup to the next shutdown for refueling. Restarting the reactor after refueling belongs to another operating cycle. The operating cycle includes the first fuel loading cycle (i.e., the first cycle) and subsequent refueling cycles. In the first cycle, the codings of all fuel assemblies in the reactor core are non-repetitive; in subsequent refueling cycles, the fuel elements entering the core and the original fuel elements in the core, that is, the fuel elements in the same operating cycle of the core operation, have non-repetitive codings.

[0032] S200. For fuel elements with different codings in the same operating cycle, different tracers are selected. The tracer includes at least one tracer element.

[0033] The tracer element of the tracer is different from the original elements of the reactor, different from the elements of the activation products of the reactor, and different from the elements generated by the fission of uranium oxide, which is conducive to clearly distinguishing whether the detected elements come from fuel leakage or the original or generated elements of the reactor itself. The tracer element can adopt isotopes different from all the elements contained in the reactor.

[0034] In some embodiments, the tracer includes a tracer element having at least two isotopes with different abundances. The tracer is composed of one of the isotopes of the tracer element; or, the tracer is composed of at least two isotopes of the tracer element, and the contents of at least two isotopes in different tracers are different. The tracer can be a simple substance gas, such as helium (He) or nitrogen (N 2 ), where nitrogen has two isotopes, namely N-14 and N-15. Then the nitrogen tracer can be composed of one or two isotopes, that is 14 N 2 , 14 N 15 N, 15 N 2 . Among them, for the nitrogen tracer 14 N 15 N, 14 N and 15 N, the content ratio can be 1:9, 3:7, 5:5, 6:4, 8:2, etc.

[0035] In other embodiments, the tracer includes at least two tracer elements, and at least one tracer element has at least two isotopes with different abundances. The tracer is composed of at least one isotope of each tracer element. In different tracers, the contents of at least two isotopes in at least one tracer element are different. For example, the tracer includes two tracer elements, one of which has two isotopes, and the content ratio of the two isotopes of this tracer element is different in different tracers.

[0036] For example, the tracer includes two tracer elements, carbon and oxygen. Carbon has three isotopes, namely C-12, C-13, and C-14, and oxygen has three isotopes, namely O-16, O-17, and O-18. The tracer is a carbon dioxide tracer composed of at least one isotope of carbon and at least one isotope of oxygen. For example, it can be 12 C 16 O 2 , 12 C 16 O 17 O, 13 C 16 O 18 O, 14 C 18 O 2etc., or the carbon element in carbon dioxide contains two or three isotopes at the same time, and the oxygen element contains three isotopes at the same time. In addition, different content ratios are adopted for multiple isotopes of the same tracer element in the carbon dioxide tracer. For example, the contents of isotopes C-12 and C-13 in the carbon element are different, and the contents of isotopes O-16 and O-18 in the oxygen element are also different, so that a variety of different carbon dioxide tracers can be combined.

[0037] The tracer can be a gas or a salt that can dissolve in water, preferably a gas. This is because after the fuel element is damaged, the water outside the fuel rod will enter the fuel rod, and the gas is easy to be displaced. The tracer should not be a liquid because the liquid will undergo a phase change at high temperature, increasing the risk of overpressure.

[0038] S300. During the fuel assembly process in the reactor core, the same tracer is filled into the fuel rods of the same fuel element.

[0039] The fuel rod includes a cladding, an upper end plug, a lower end plug, and fuel pellets. The upper end plug and the lower end plug are respectively fitted with both ends of the cladding to form a sealed space inside the cladding. The fuel pellets are located inside the cladding, and a cavity is formed between the upper end plug and the fuel pellets. The tracer is filled in the cavity. In some embodiments, the fuel rod further includes a spring provided inside the cladding. One end of the spring abuts against the bottom of the upper end plug, and the other end abuts against the top of the fuel pellets. The bottom of the fuel pellets abuts against the top of the lower end plug. The space at the top of the fuel pellets inside the cladding, that is, the space where the spring is located, is used to fill the tracer, without the need for complex modification or re-design of the structure of the fuel element. The composition of the tracer can be selected according to the material, structure, etc. of the fuel element. For example, the tracer cannot react with the inner wall of the cladding of the fuel rod and the fuel pellets, so as to avoid environmental interference, ensure the accuracy of the detection results, reduce the risk of polluting the inside of the fuel element at the same time, prevent the influence of the occurring reaction on the performance of the fuel element, and ensure the long-term stability of the fuel element.

[0040] If the filled tracer is a gas, the release rate of the fission gas generated after the reactor operates needs to be considered. The pressure generated by the filled gas and the fission gas together will cause a change in the internal pressure of the fuel, and it is necessary to ensure safety and reliability. Among them, the release rate of the fission gas is related to the burnup depth, and the burnup depth depends on the operation time and power of the reactor. The longer the operation time and the higher the power of the reactor, the higher the release rate of the fission gas. Considering the filled gas tracer and the fission gas generated by the reactor comprehensively, the increased quantity of the fission gas can be calculated. The total pressure of the gas needs to be controlled within a safe range and cannot be overpressurized (such as 2 MPa), so as to ensure that the structure of the fuel rod is not damaged.

[0041] S400. Sample and detect the fluid in the primary loop of the reactor, determine whether the fuel elements are damaged according to the detection results, and confirm the positions and quantities of the damaged fuel elements.

[0042] Among them, when sampling the fluid in the primary loop of the reactor, water samples can be collected or gases can be collected, and corresponding detection methods are selected according to the tracer elements of the tracers. For example, elemental analysis can be carried out using a mass spectrometer. If a tracer element is detected, it is determined that the fuel element is damaged, and according to the composition of the tracer element, the positions and quantities of the damaged fuel elements are confirmed; if no tracer element is detected, resampling and detection are carried out. Specifically, if a tracer element is detected, the components of the leaked tracer are determined according to the types of the tracer element or its isotopes and the content ratio between the isotopes in different tracer elements, and the positions and quantities of the damaged fuel elements are confirmed according to the tracer, so as to effectively realize the damage detection and positioning of several fuel elements in the reactor core.

[0043] In some embodiments, according to the radioactive level of the primary loop of the reactor, the fluid in the primary loop of the reactor is sampled regularly, and the sampling period is 12h to 36h. For example, 12h, 18h, 24h, 30h, 36h, etc. can be selected. The sampling period can also take into account the response time of the tracer element monitoring instrument and be set to different sampling periods according to different actual requirements. For example, it can be less than 12h or more than 36h. The degree of damage of the fuel element will affect the release amount of the tracer. If the release amount is too small, it may be difficult to detect, and the detection sensitivity of the monitoring instrument needs to be improved. As long as the tracer is detected, it means that the fuel element is damaged.

[0044] The present invention classifies and codes the fuel elements in the reactor core, selects the types and content ratios of the tracer elements corresponding to different fuel elements for the tracers, fills the tracers in the fuel rods of the fuel elements, samples and detects the primary loop and analyzes the tracer elements, so as to realize the leakage detection of the fuel elements of the nuclear reactor and locate the leaking fuel elements.

[0045] The method for detecting and positioning nuclear fuel damage of the present invention belongs to a non-invasive method, that is, it is not necessary to add monitoring sensors to the reactor core or the core fuel elements, and it does not affect the thermal-hydraulic calculation and physical calculation. Since the tracer elements of the filled tracers are elements not present in the reactor and are not elements generated by the fission of uranium oxide, the fuel leakage can be accurately detected. According to the composition of the tracer elements of different tracers, the damaged fuel elements can be further located.

[0046] During the operation of a nuclear power plant, if the occurrence of a fuel element breakage event can be accurately determined, even a minor breakage event, the nuclear power plant can arrange the work plan for refueling maintenance in advance, handle and inspect the damaged fuel elements in advance, and improve the maintenance efficiency. The nuclear fuel breakage detection and localization method of the present invention can accurately determine whether the fuel element cladding is damaged without shutting down the reactor, and can confirm the position of the damaged fuel element, reducing the economic losses caused by misjudgment of breakage in terms of reactor shutdown and maintenance. It has double important significances of ensuring nuclear safety and reducing huge economic losses.

[0047] The application of the nuclear fuel breakage detection and localization method of the present invention is not limited to the fuel elements of a nuclear power plant, and can also be used for leakage detection of other reactor elements.

[0048] The following is illustrated by examples:

[0049] Using the nuclear fuel breakage detection and localization method of the present invention, fuel breakage detection is carried out on 177 fuel element assemblies in the core of a nuclear power unit with a capacity of one million kilowatts. The method includes the following steps:

[0050] S100. Classify and code the 177 fuel element assemblies in the reactor core, and the codes of the fuel element assemblies in each cycle of the reactor core are not repeated. Among them, the 177 fuel element assemblies have different U-235 enrichments, and the fuel element assemblies are classified and coded according to the U-235 enrichment. Theoretically, the total number of non-repeating codes is at least 177, which can ensure that different positions in the core of each cycle correspond to different fuel element codes, and when fuel breakage occurs, the position of the damaged fuel element can be accurately located.

[0051] S200. Select different tracers for the fuel element assemblies with different codes in the same cycle. The tracer includes at least one tracer element.

[0052] Taking the first batch as an example, the tracers of this batch include two tracer elements, namely carbon and oxygen. Among them, carbon has three isotopes, namely C-12, C-13, and C-14, and oxygen has three isotopes, namely O-16, O-17, and O-18. The tracer is a carbon dioxide tracer composed of at least one isotope of carbon and at least one isotope of oxygen. The carbon dioxide tracer may include C-12 and / or C-13 and O-16 and / or O-18. The contents of C-12 and C-13 in different carbon dioxide tracers are different, and the contents of O-16 and O-18 are also different. For example, the total content of C-12 and C-13 is 100%. The content of C-12 in the carbon element of different tracers decreases from 100% to 0%, while the content of C-13 in the carbon element of different tracers increases from 0% to 100%. The total content of O-16 and O-18 is 100%. The content of O-16 in the oxygen element of different tracers decreases from 100% to 0%, while the content of O-18 in the oxygen element of different tracers increases from 0% to 100%. The number of combinations of tracer elements in each batch (i.e., the total number of tracers) is greater than the total number of several fuel elements to ensure that the tracers filled in different fuel elements are different.

[0053] S300. During the fuel assembly process in the reactor core, the same tracer is filled into the fuel rods of the same fuel element. Among them, the fuel element adopts an array arrangement of 17×17. Each box of fuel elements includes 24 guide tubes, 1 instrument tube, and 264 fuel rods. Carbon dioxide tracers are filled into the 264 fuel rods in the fuel element.

[0054] Further, the fuel rod includes a cladding, an upper end plug, a lower end plug, and fuel pellets. The upper end plug and the lower end plug are respectively fitted with both ends of the cladding to form a sealed space inside the cladding. The fuel pellets are located inside the cladding. A cavity is formed between the upper end plug and the fuel pellets, and the carbon dioxide tracer is filled in the cavity. In some embodiments, the fuel rod further includes a spring provided inside the cladding. One end of the spring abuts against the bottom of the upper end plug, and the other end abuts against the top of the fuel pellets. The bottom of the fuel pellets abuts against the top of the lower end plug. Then the carbon dioxide tracer is filled in the space at the top of the fuel pellets inside the cladding and is located around the spring. The total pressure of the carbon dioxide tracer and the fission gas generated after the reactor operation is controlled within 2 MPa to ensure that it does not affect the fuel rod itself.

[0055] S400. Sample and detect the fluid in the primary loop of the reactor, and determine whether the fuel element is damaged according to the detection results, and confirm the position and quantity of the damaged fuel elements.

[0056] Among them, the water in the primary circuit of the reactor is sampled regularly, and the sampling period is 24 h. The elements of the sample are analyzed by a mass spectrometer. If a tracer element is detected, it is determined that the fuel element is damaged. Further, according to the type of the tracer element or its isotope and the content ratio between the isotopes in different tracer elements, the leaked tracer is determined, and the position and quantity of the damaged fuel element are confirmed according to the tracer. If no tracer element is detected, the primary circuit is resampled and detected.

[0057] The method for detecting and positioning nuclear fuel damage of the present invention can accurately determine whether the claddings of several fuel elements in the core of a nuclear power unit are damaged without shutting down the reactor, and can confirm the positions of the damaged fuel elements, reducing the economic losses caused by misjudgment of damage for shutdown and maintenance, and having the dual important significance of ensuring nuclear safety and reducing huge economic losses.

[0058] It can be understood that the above embodiments only express the preferred embodiments of the present invention, and the description thereof is relatively specific and detailed, but it cannot be construed as a limitation on the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, all equivalent transformations and modifications made in accordance with the scope of the claims of the present invention shall fall within the scope covered by the claims of the present invention.

Claims

1. A method for detecting and locating nuclear fuel damage, characterized in that: The following steps are involved: S100, classifying and coding a plurality of fuel elements of a reactor core, wherein the codes of the fuel elements of each batch of the reactor core are not repeated; S200, selecting different tracers for the fuel elements with different codes in the same batch, wherein the tracers include at least one tracer element; S300, during the fuel assembly process of the reactor core, filling the fuel rods of the same fuel element with the same tracer; S400, sampling and testing the fluid in the primary loop of the reactor, determining whether the fuel element is damaged based on the test results, and confirming the location and number of the damaged fuel elements.

2. The method for detecting and locating nuclear fuel damage according to claim 1, characterized in that: In the step S100, the plurality of fuel elements have different enrichments, and the plurality of fuel elements are classified and coded according to the enrichments.

3. The method for detecting and locating nuclear fuel damage according to claim 1, characterized in that: In step S200, the tracer includes a tracer element, and the tracer element has at least two isotopes, and different isotopes have different abundances.

4. The method for detecting and locating nuclear fuel damage according to claim 3, characterized in that: The tracer is composed of one isotope; or, the tracer is composed of at least two isotopes, and the contents of at least two isotopes in different tracers are different.

5. The method for detecting and locating nuclear fuel damage according to claim 1, characterized in that: In step S200, the tracer includes at least two tracer elements, at least one of which has at least two isotopes, and different isotopes have different abundances.

6. The method for detecting and locating nuclear fuel damage according to claim 5, characterized in that: In different tracers, the contents of at least two isotopes of at least one tracer element are different.

7. The method for detecting and locating nuclear fuel damage according to claim 1, characterized in that: In the step S200, the tracer element is different from the original element of the reactor, the tracer element is different from the element of the activation product of the reactor, and the tracer element is different from the element produced by the fission of uranium oxide.

8. The method for detecting and locating nuclear fuel damage according to claim 1, characterized in that: In the step S300, the fuel rod includes a cladding, an upper end plug, a lower end plug and a fuel core block, the upper end plug and the lower end plug respectively cooperate with the two ends of the cladding to form a closed space inside the cladding; the fuel core block is located in the cladding, a cavity is formed between the upper end plug and the fuel core block, and the tracer is filled in the cavity.

9. The method for detecting and locating nuclear fuel damage according to claim 8, characterized in that: In the step S300, the fuel rod also includes a spring arranged in the cladding, one end of the spring presses against the bottom of the upper end plug, and the other end presses against the top of the fuel pellet, and the bottom of the fuel pellet presses against the top of the lower end plug; the tracer is filled in the cladding and is located around the spring.

10. The method for detecting and locating nuclear fuel damage according to claim 1, characterized in that: In the step S400, the fluid of the first loop of the reactor is sampled, and a corresponding detection method is selected according to the tracer element of the tracer; if the tracer element is detected, it is determined that the fuel element is damaged, and the position and number of the damaged fuel elements are confirmed based on the composition of the tracer element; if the tracer element is not detected, resampling and detection are performed.

11. The method for detecting and locating nuclear fuel damage according to any one of claims 3 to 6, characterized in that: In step S400, if the tracer element is detected, the leaked tracer is determined based on the type of the tracer element or its isotope and the content ratio between the isotopes in different tracer elements, and the location and number of the damaged fuel elements are confirmed based on the tracer.

12. The method for detecting and locating nuclear fuel damage according to claim 1, characterized in that: In the step S400, the fluid in the primary loop of the reactor is sampled regularly according to the radioactivity level of the primary loop of the reactor, and the sampling period is 12 hours to 36 hours.

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