A device and method for measuring long-term neutron irradiation-induced volume change of concrete

Abstract

The present application relates to a kind of long-term neutron irradiation caused concrete volume change determination device and method, the device includes: the neutron emitter and neutron receiver of matching setting in laboratory interior, test concrete test piece is fixed between neutron emitter and neutron receiver, test concrete test piece is measured temperature by temperature detector;Test chamber is equipped with control concrete test piece, control concrete test piece outside is wrapped up collection mould, setting condenser tube, water vapor collector and high-precision electronic scale.The method: one, the overall expansion rate of concrete test piece is determined by strain measuring device;Two, the self volume change of test concrete test piece in environment;Three, the volume change rate of concrete caused by neutron radiation is calculated in combination with the thermal expansion coefficient of concrete and the drying shrinkage of concrete;Four, the volume change rate of engineering structure shielding concrete with time is inferred by the relationship between the volume expansion rate of experimental concrete and neutron irradiation dose, to ensure the safety of nuclear engineering structure.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and in particular relates to a device and method for measuring concrete volume change caused by long-term neutron irradiation. Background Art

[0002] Concrete, a widely used shielding and structural material in nuclear facilities, is exposed to long-term high-energy neutron radiation. The evolution of its physical and mechanical properties is directly related to the service life and safety of engineering structures. Neutron radiation, through interactions with non-metallic nuclei (e.g., elastic and inelastic scattering, and transmutation reactions), can cause atomic displacements, lattice damage, and changes in elemental composition within concrete aggregates and cement hydration products. This can lead to microcrack propagation, pore structure degradation, and macroscopic volume deformation. These volume changes can degrade the concrete's shielding properties, cause structural stress concentrations, and even cracking, posing a potential threat to the safe operation of nuclear facilities.

[0003] Currently, research on the effects of neutron radiation on concrete has mostly focused on macroscopic performance tests such as strength and elastic modulus after short-term irradiation, or on the use of numerical simulation methods to predict damage accumulation. However, in actual engineering, concrete structures are subject to neutron irradiation for decades, and the long-term cumulative effects differ significantly from the short-term experimental conclusions. Traditional experimental equipment is limited by the intensity of the irradiation source, the uniformity of the irradiation, and the ability to monitor online. It is difficult to simulate the low-flux, long-term irradiation environment in actual working conditions, and lacks high-precision dynamic tracking of small volume changes. For example, existing technologies often use short-term, high-dose irradiation from accelerators to simulate long-term effects, but ignore the time dependence of the material damage mechanism; and offline measurement methods (such as micrometers and laser scanning) cannot capture the continuous deformation during the irradiation process in real time, resulting in discrete data and difficulty in revealing the dynamic laws of volume evolution.

[0004] Furthermore, concrete, as a multiphase composite material, exhibits significant heterogeneity and component-dependence in its irradiation damage. Siliceous aggregates are susceptible to amorphous expansion under neutron irradiation, while cement pastes may experience increased porosity due to gas production from water molecules. Deformation differences between different components further exacerbate the complexity of volume changes. Existing research lacks a comprehensive understanding of the mechanisms of multiphase synergy and lacks specialized testing systems for long-term irradiation conditions. This results in a reliance on conservative assumptions in engineering design, limiting the economic and safety of nuclear facilities.

[0005] Therefore, how to provide a device and method for measuring the volume change of concrete caused by long-term neutron irradiation is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] This invention provides a device and method for measuring concrete volume changes induced by long-term neutron irradiation. These devices and methods can simulate long-term neutron irradiation environments and achieve high-precision in-situ volume change measurement (taking into account the thermal expansion and contraction of concrete due to its own temperature, as well as shrinkage during long-term drying). These devices and methods are of great significance for revealing the mechanisms of concrete irradiation damage and improving the durability design standards for nuclear facilities. Through an innovative integrated irradiation and monitoring design, this application overcomes the temporal and spatial limitations of traditional technologies, providing key technical support for the long-life assessment and safety assurance of nuclear engineering materials.

[0007] In order to solve the above technical problems, the present invention includes the following technical solutions:

[0008] A method for measuring the volume change of concrete caused by long-term neutron irradiation comprises the following steps:

[0009] Step S1, providing a device for measuring the volume change of concrete caused by long-term neutron irradiation;

[0010] Step S2: In a test chamber, neutrons are vertically emitted from a neutron emitter to a neutron receiver, and the neutron flux is recorded. At least five temperature probes are embedded in the center and around the periphery of the concrete specimen, with the spacing between the temperature probes located on the periphery and the boundary of the test concrete specimen controlled to be 5 to 10 mm. At least three sets of strain gauges are evenly fixed on the stainless steel ring and the concrete specimen. A control concrete specimen is placed in the test chamber, and a collection mold is wrapped around the outside of the control concrete specimen. The collection mold is capable of collecting water vapor evaporated from the control concrete specimen under the influence of the environment and neutrons. The water vapor enters a water vapor collector along a matching condenser, and the water mass is measured using a high-precision electronic scale.

[0011] Step S3, turning on the device, measuring the deformation of the concrete specimen by a strain gauge, and calculating the volume expansion coefficient of the concrete specimen by comprehensively calculating the expansion values ​​at each end of the concrete specimen;

[0012] Step S4: Record the temperature of each temperature detector, calculate the temperature of the concrete specimen from the center temperature and the edge temperature; establish a functional relationship between the temperature of the concrete specimen and the thermal expansion coefficient through experiments;

[0013] Step S5: measuring the mass of water and the mass of the control concrete specimen using a high-precision electronic scale, and obtaining a linear relationship between the water loss rate of the control concrete specimen and its drying shrinkage rate at temperatures between 0°C and 200°C through a large number of experimental fittings;

[0014] Step S6: The volume change rate of the concrete specimen caused by neutron radiation is obtained by combining the volume expansion coefficient, the thermal expansion coefficient, and the drying shrinkage rate;

[0015] Step S7: Calculate the exponential relationship between the volume change rate of the concrete specimen and the product of the neutron shielding flux, the weighted energy of the neutrons, and the irradiation time; and infer the volume change of the engineering structure shielding concrete through the exponential relationship.

[0016] Furthermore, in step S3, the expansion values ​​of each end of the concrete specimen are the front end group expansion value E1, the middle end group expansion value E2, and the rear end group expansion value E3. The volume expansion coefficient of the concrete specimen is Calculated by the following formula:

[0017] ,

[0018] Where, It also includes the thermal expansion and contraction of the control concrete specimen itself and the drying shrinkage caused by water loss of concrete in a long-term environment; the unit of the expansion value E is cm.

[0019] Furthermore, in step S4, the temperatures of the five temperature detectors are: the center temperature is T1, and the edge temperatures are T2, T3, T4 and T5, so that the average temperature of the test concrete specimen is:

[0020] ,

[0021] The functional relationship between the concrete temperature T and the thermal expansion coefficient CTE is:

[0022] .

[0023] Furthermore, in step S5, the mass of water is measured to be W1, the mass of the test concrete specimen is W2, and the water loss rate of the test concrete specimen and its volume shrinkage rate have the following relationship:

[0024] ,

[0025] Wherein, the unit of mass W is g.

[0026] Furthermore, in step S6, the concrete volume change rate V caused by neutron radiation is calculated by the following formula:

[0027] .

[0028] Furthermore, during neutron irradiation, the concrete volume change rate V is related to the weighted energy of the neutrons. , I is the incident neutron flux per unit time, I0 is the outgoing neutron flux per unit time, and t is the irradiation time. The following relationship exists:

[0029] ,

[0030] In the formula, K is the correction coefficient, b is the aggregate coefficient, b=0.65~0.75 for siliceous aggregate, b=0.60~0.70 for limestone, and b=0.55~0.65 for lightweight aggregate. This formula can be used to obtain the relationship between the volume expansion rate of experimental concrete and the neutron irradiation dose, thereby inferring the relationship between the volume change rate of engineering structure shielding concrete and time to ensure the safety of nuclear-related engineering structures.

[0031] The present invention also provides a device for measuring the volume change of concrete caused by long-term neutron irradiation, comprising a neutron emitter and a neutron receiver which are arranged in a matched manner inside a test chamber. Neutrons are vertically emitted to the neutron receiver by the neutron emitter, and the neutron flux is recorded by the neutron receiver. A test concrete specimen is fixed between the neutron emitter and the neutron receiver via a stainless steel ring and a stainless steel frame. Temperature detectors are buried in the middle and around the four sides of the test concrete specimen, and a strain measuring device group is provided on the stainless steel ring. A control concrete specimen is provided in the test chamber, and a collection mold is wrapped around the outside of the control concrete specimen. The control concrete specimen is equipped with a condenser, a water vapor collector and a high-precision electronic scale for measuring the water vapor evaporated from the control concrete specimen under the influence of the environment.

[0032] Furthermore, the test concrete specimen is a cylinder with a diameter of 6 cm and a thickness of 4 cm.

[0033] Furthermore, the strain gauge group includes 12 strain gauges, which are divided into a specimen front end group, a specimen middle end group, and a specimen rear end group in groups of 4 and are evenly distributed on the test concrete specimen.

[0034] Furthermore, the collecting mold comprises a cubic structure made of tin.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The device and method for measuring concrete volume changes induced by long-term neutron irradiation, provided by this invention, can simulate a long-term neutron irradiation environment and achieve in-situ, high-precision volume change measurement. This device and method takes into account the thermal expansion and contraction of concrete due to its own temperature, as well as shrinkage during long-term drying. This device and method are of great significance for revealing the mechanisms of concrete irradiation damage and improving the durability design standards for nuclear facilities. Through an innovative integrated irradiation and monitoring design, this application overcomes the temporal and spatial limitations of traditional technologies, providing key technical support for the long-life assessment and safety assurance of nuclear engineering materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A top view of the device for measuring the volume change of concrete caused by long-term neutron irradiation in Example 1;

[0038] Figure 2A front view of the distribution of temperature detectors in the device for measuring the volume change of concrete caused by long-term neutron irradiation in Example 1;

[0039] Figure 3 This is a front view of the distribution of molds collected in the device for measuring the volume change of concrete caused by long-term neutron irradiation in Example 1;

[0040] Figure 4 This is a flow chart of the method for measuring the volume change of concrete caused by long-term neutron irradiation in Example 2.

[0041] In the figure,

[0042] 1-Test chamber; 2-Neutron emitter; 3-Neutron receiver; 4-Stainless steel ring; 5-Stainless steel rack; 6-Test concrete specimen; 7-Temperature detector; 8-Strain gauge; 9-Control concrete specimen; 10-Collection mold; 11-Condenser; 12-Water vapor collector; 13-High-precision electronic scale. DETAILED DESCRIPTION

[0043] The following is a detailed description of the device and method for measuring the volume change of concrete caused by long-term neutron irradiation provided by the present invention, with reference to specific embodiments. The advantages and features of the present invention will become more apparent from the following description.

[0044] Example 1

[0045] The following combination Figures 1 to 3 The apparatus for measuring the volume change of concrete caused by long-term neutron irradiation according to the present invention will be described in detail.

[0046] Please refer to Figures 1 to 3 A device for measuring the volume change of concrete caused by long-term neutron irradiation includes a neutron emitter 2 and a neutron receiver 3, which are arranged in a test chamber 1. Neutrons are vertically emitted to the neutron receiver 3 by the neutron emitter 2, and the neutron flux is recorded by the neutron receiver 3. A test concrete specimen 6 is fixed between the neutron emitter 2 and the neutron receiver 3 via a stainless steel ring 4 and a stainless steel frame 5. Temperature detectors 7 are buried in the middle and around the four sides of the test concrete specimen 6, and a strain gauge group is provided on the stainless steel ring 4. A control concrete specimen 9 is provided in the test chamber 1. The control concrete specimen 9 is wrapped with a collection mold 10. The control concrete specimen 9 is equipped with a condenser 11, a water vapor collector 12, and a high-precision electronic scale 13 for measuring the water vapor evaporated from the control concrete specimen 9 under the influence of the environment.

[0047] In this embodiment, more preferably, the test concrete specimen 6 is a cylinder with a diameter of 6 cm and a thickness of 4 cm.

[0048] In this embodiment, more preferably, the strain gauge group includes 12 strain gauges 8 , and the 12 strain gauges are divided into a specimen front end group, a specimen middle end group, and a specimen rear end group in groups of 4 and are evenly distributed on the test concrete specimen 6 .

[0049] In this embodiment, more preferably, the strain gauge 8 adopts a digital display mode, and the screen is made of lead glass.

[0050] In this embodiment, more preferably, the collecting mold 10 includes a cubic structure made of tin.

[0051] In this embodiment, more preferably, the test concrete specimen 6 and the control concrete specimen 9 have completely identical shapes and materials.

[0052] In this embodiment, more preferably, the test chamber 1 is cast by barite concrete.

[0053] Example 2

[0054] Please continue to refer to Figure 4 The present invention also provides a method for measuring the volume change of concrete caused by long-term neutron irradiation, comprising the following steps:

[0055] Step S1, providing a device for measuring the volume change of concrete caused by long-term neutron irradiation for standby use;

[0056] Step S2: Arrange a neutron emitter 2 and a neutron receiver 3 in the test chamber 1. Neutrons are vertically emitted from the neutron emitter 2 to the neutron receiver 3, and the received neutron flux is recorded by the neutron receiver 3. Five temperature probes 7 are embedded in the center and around the periphery of the test concrete specimen 6. The four temperature probes 7 located on the periphery are 5 mm apart from the boundary of the test concrete specimen 6. Twelve strain gauges 8 are fixed to a stainless steel ring 4 and are evenly distributed on the test concrete specimen 6. Set a control concrete specimen 9 in the test chamber 1. The control concrete specimen 9 is wrapped with a collection mold 10. The collection mold 10 can collect water vapor evaporated from the test concrete specimen 6 under environmental influences. The water vapor enters a water vapor collector 12 through a matching condenser 11, and the water mass is measured by a high-precision electronic scale 13.

[0057] Step S3, start the device, and measure the deformation of the 12 strain gauges 8. The expansion value of the front end group of the specimen is E1, the expansion value of the middle end group is E2, and the expansion value of the rear end group is E3. The volume expansion coefficient of concrete is Calculated by the following formula:

[0058] ,

[0059] Where, It also includes the thermal expansion and contraction of the control concrete specimen itself and the drying shrinkage caused by water loss of concrete in a long-term environment; the unit of expansion value E is cm;

[0060] Step S4: The temperatures of the five temperature detectors 7 are measured in sequence: the center temperature is T1, and the edge temperatures are T2, T3, T4, and T5, so that the average temperature of the test concrete specimen 6 is:

[0061] ,

[0062] By conducting a concrete thermal expansion coefficient test on test concrete specimen 6, the functional relationship between concrete temperature T and thermal expansion coefficient CTE was determined:

[0063] ;

[0064] Step S5: The mass of water is measured as W1 by a high-precision electronic scale 13, and the mass of the test concrete specimen 6 is measured as W2. Through a large number of experiments, it is inferred that when the temperature is between 0 and 200° C., the water loss rate of the test concrete specimen 6 and its volume shrinkage rate have the following relationship:

[0065] ,

[0066] Where, the unit of mass W is g,

[0067] Step S6: The concrete volume change rate V caused by neutron radiation is calculated using the following formula:

[0068] .

[0069] Step S7: During neutron irradiation, the concrete volume change rate V and the weighted energy of neutrons , I is the incident neutron flux per unit time, I0 is the outgoing neutron flux per unit time, and t is the irradiation time. The following relationship exists:

[0070]

[0071] In the formula, K is the correction coefficient and b is the aggregate coefficient (siliceous aggregate b=0.65~0.75, limestone b=0.60~0.70, lightweight aggregate b=0.55~0.65). This formula can be used to obtain the relationship between the volume expansion rate of experimental concrete and the neutron irradiation dose, and to infer the relationship between the volume change rate of engineering structure shielding concrete and time to ensure the safety of nuclear engineering structures.

[0072] Specifically, the method for determining the volume change of concrete caused by long-term neutron irradiation comprises the following steps: 1. determining the overall expansion rate of the concrete test piece by using a strain gauge (i.e. a strain measuring device); 2. determining the self-volume change of the test concrete in the environment; 3. combining the thermal expansion coefficient of the concrete and the drying shrinkage of the concrete to calculate the volume change rate of the concrete caused by neutron irradiation; and 4. determining the volume change rate of the shielding concrete of the nuclear engineering structure over time by extrapolating the relationship between the volume expansion rate of the test concrete and the neutron irradiation dose, so as to ensure the safety of the nuclear engineering structure.

[0073] Embodiment three

[0074] The volume change of a serpentine concrete caused by long-term neutron irradiation is determined through a month-long neutron irradiation test (the neutron energy is between 0.002 eV and 1 MeV, the weighted energy is 5×10 -4 MeV, and the neutron flux is 10 10 n / cm 2 ·s). The expansion values obtained from 12 strain gauges are E1=0.012 cm, E2=0.010 cm, and E3=0.006 cm.

[0075] ,

[0076] The temperatures detected by the temperature detector are T1=22℃, T2=25℃, T3=24℃, T4=23℃, and T5=24℃,

[0077] ,

[0078] The thermal expansion coefficient of the serpentine concrete changes linearly with temperature under normal temperature conditions, and the following relationship can be obtained by fitting the data:

[0079] CTE=0.000625T-0.0125

[0080] The temperature T=23℃ obtained by the temperature detector is substituted into the above formula to calculate the thermal expansion coefficient of the serpentine concrete:

[0081] CTE=0.000625T-0.0125=0.000625×23-0.0125=0.001875%

[0082] The mass of water is W1=0.3g, and the mass of the concrete test piece is W2=260g, which are determined by a high-precision scale.

[0083] ,

[0084] The volume change rate V of the concrete caused by neutron irradiation is:

[0085] .

[0086] The flux I of incident neutrons per unit time is 10 10 n / cm 2 ·s, the flux of outgoing neutrons per unit time is 7×10 9 n / cm 2 ·s, the irradiation time is 2.592×10 6 s (one month), the serpentine concrete generally takes b=0.7, and the correction coefficient K can be obtained:

[0087]

[0088] Thus, by obtaining the parameters such as neutron flux, neutron weighted energy and irradiation time in the nuclear engineering, the relationship between the volume change rate of the serpentine shielding concrete and time can be obtained, as follows:

[0089] The expansion rate of the nuclear concrete structure can be predicted by the formula, so as to predict the safety of the engineering structure.

[0090] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples. The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A method for measuring the volume change of concrete caused by long-term neutron irradiation, characterized in that: The steps include: Step S1: providing a device for measuring the volume change of concrete caused by long-term neutron irradiation; Step S2: In a test chamber, neutrons are vertically emitted from a neutron emitter to a neutron receiver, and the neutron flux is recorded. At least five temperature probes are embedded in the center and around the periphery of the concrete specimen, with the spacing between the temperature probes located on the periphery and the boundary of the test concrete specimen controlled to be 5 to 10 mm. At least three sets of strain gauges are evenly fixed on the stainless steel ring and the concrete specimen. A control concrete specimen is placed in the test chamber, and a collection mold is wrapped around the outside of the control concrete specimen. The collection mold is capable of collecting water vapor evaporated from the control concrete specimen under the influence of the environment and neutrons. The water vapor enters a water vapor collector along a matching condenser, and the water mass is measured using a high-precision electronic scale. Step S3, start the device, measure the deformation of the concrete specimen by the strain gauge, and calculate the volume expansion coefficient of the concrete specimen by the expansion value of each end of the concrete specimen. The expansion values ​​of each end of the concrete specimen are the front end group expansion value E1, the middle end group expansion value E2, the rear end group expansion value E3, and the volume expansion coefficient of the concrete specimen Calculated by the following formula: ， Where, It also includes the thermal expansion and contraction of the control concrete specimen itself and the drying shrinkage caused by water loss of concrete in a long-term environment; the unit of expansion value E is cm; Step S4: Record the temperature of each temperature detector, calculate the temperature of the concrete specimen from the center temperature and the edge temperature; establish a functional relationship between the temperature of the concrete specimen and the thermal expansion coefficient through experiments; Step S5: Using a high-precision electronic scale to measure the mass of water and the mass of the control concrete specimen, a linear relationship between the water loss rate of the control concrete specimen and its drying shrinkage at temperatures between 0°C and 200°C was obtained through extensive experimental fitting. The mass of water was measured as W1, the mass of the test concrete specimen was measured as W2, and the water loss rate of the test concrete specimen and its volume shrinkage had the following relationship: ， Wherein, the unit of mass W is g; Step S6: The volume change rate of the concrete specimen caused by neutron radiation is obtained by combining the volume expansion coefficient, the thermal expansion coefficient, and the drying shrinkage rate. The volume change rate V of the concrete caused by neutron radiation is calculated by the following formula: ； Step S7: Calculate the exponential relationship between the volume change rate of the concrete specimen and the product of the neutron shielding flux, the weighted energy of the neutrons, and the irradiation time; and infer the volume change of the engineering structure shielding concrete through the exponential relationship.

2. The measuring method according to claim 1, wherein In step S4, the temperatures of the five temperature detectors are: the center temperature is T1, and the edge temperatures are T2, T3, T4 and T5, so that the average temperature of the test concrete specimen is: ， The functional relationship between the concrete temperature T and the thermal expansion coefficient CTE is: 。 3. The measuring method according to claim 2, characterized in that In the step S7, during the neutron irradiation process, the concrete volume change rate V and the weighted energy of the neutrons , I is the incident neutron flux per unit time, I0 is the outgoing neutron flux per unit time, and t is the irradiation time. The following relationship exists: ， In the formula, K is the correction coefficient, b is the aggregate coefficient, b=0.65~0.75 for siliceous aggregate, b=0.60~0.70 for limestone, and b=0.55~0.65 for lightweight aggregate. This formula can be used to obtain the relationship between the volume expansion rate of experimental concrete and the neutron irradiation dose, thereby inferring the relationship between the volume change rate of engineering structure shielding concrete and time to ensure the safety of nuclear-related engineering structures.

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