Device and method for measuring neutron shielding capability of concrete at high temperature

Abstract

The invention relates to a device and a method for measuring neutron shielding capability of concrete at high temperature, the device comprises a neutron emitter, a shielding device and a neutron receiver, the neutron emitter is located at a first side of the shielding device, and the neutron receiver is located at a second side, opposite to the first side, of the shielding device; the shielding device comprises a support and samples, the samples are arranged on the support, the samples comprise three test samples and a measurement environment background sample, the three test samples are a control group, a cylindrical concrete test piece and a detection piece group in sequence, and the cylindrical concrete test piece group is arranged on the support. An ultrahigh heat-conducting polymer film layer and a stainless steel alloy sleeve layer are sequentially arranged on the outer side of the cylindrical concrete test piece, and the detection piece comprises a temperature sensor and a strain gauge. The neutron shielding capability is measured by adopting the measuring device, so that the neutron shielding capability of the new-generation molten salt reactor nuclear energy system warehouse concrete is effectively measured, and the thickness design of the neutron shielding concrete in engineering construction is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and in particular relates to a device and method for measuring the neutron shielding ability of concrete at high temperature. Background Art

[0002] The molten salt reactor nuclear energy system is an important development direction in the field of new generation nuclear fission energy, and is of great significance to ensuring national energy security. At the same time, the molten salt reactor has outstanding advantages such as less nuclear waste, failure safety, compact structure, high temperature output, and strong regional adaptability. Due to the different operating modes, there are also great differences in the construction of molten salt reactors and traditional pressurized water reactors and heavy water reactors, especially in terms of nuclear radiation-proof building materials, which poses severe challenges. It is mainly reflected in:

[0003] First, the two main types of radiation from nuclear reactors are neutrons and gamma. The pressure vessels of traditional reactors contain a large amount of water as a moderator, which can shield the generated neutrons. Therefore, the protection requirements for neutrons are relatively low, and heavy concrete or ordinary concrete can be used to cast the containment to protect against gamma rays. The heat transfer medium used in molten salt reactors is molten salt, which is a "dry reactor". The shielding effect is not enough for the neutron moderation of the graphite layer alone. A small amount of fast neutrons and a large amount of thermal neutrons will be radiated, and the neutrons need to be further shielded by the stack concrete.

[0004] Second, the internal operating temperature of the molten salt reactor is above 600°C, while the temperature of the traditional reactor is around 300°C. The temperature of the inner surface of the thorium-based molten salt reactor concrete will also reach above 100°C, and it is necessary to consider the loss of bound water, drying shrinkage and cracking of concrete under high temperature for a long time. At the same time, the drying shrinkage behavior of concrete will affect its thickness and affect the determination of concrete neutron transmittance.

[0005] Therefore, how to provide a device and method for measuring the neutron shielding ability of molten salt reactor warehouse concrete at high temperature to determine the type of concrete in order to promote the construction of a new generation of nuclear energy systems is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] The present invention provides a device and method for measuring the neutron shielding capability of molten salt reactor bunker concrete under high temperature conditions, aiming to effectively measure the neutron shielding capability of bunker concrete of a new generation of molten salt reactor nuclear energy system, which is helpful for the thickness design of neutron shielding concrete in engineering construction.

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

[0008] A device for measuring the neutron shielding ability of concrete at high temperature, comprising: a neutron emitter, a shielding device and a neutron receiver, wherein the neutron emitter is located on a first side of the shielding device, and the neutron receiver is located on a second side of the shielding device opposite to the first side;

[0009] The shielding device includes a bracket and a sample, the sample is arranged on the bracket, and the sample includes three test samples and one measurement environment background sample, the three test samples are a control group, a cylindrical concrete specimen and a detection piece group, and a cylindrical concrete specimen group, respectively, an ultra-high thermal conductive polymer film layer and a stainless steel alloy casing layer are arranged in sequence on the outside of the cylindrical concrete specimen, and the detection piece includes a temperature sensor and a strain gauge.

[0010] Furthermore, the temperature sensor and the strain gauge in the cylindrical concrete specimen and the detection piece group are pre-buried in the cylindrical concrete specimen, and the temperature sensor is equipped with a temperature display screen, which is located outside the cylindrical concrete specimen.

[0011] Furthermore, the measurement environmental background sample is 12 cm thick boron-containing polyethylene.

[0012] The present invention also provides a method for determining the neutron shielding ability of concrete at high temperature, the method comprising the following steps:

[0013] Step S1, providing the aforementioned device for measuring the neutron shielding ability of concrete at high temperature for standby use;

[0014] Step S2, heating the stainless steel alloy casing layer by an electric coil, thereby continuously heating the cylindrical concrete specimen and maintaining its temperature at 100-150° C.;

[0015] Step S3, irradiating the sample with a neutron source having an energy range consistent with the inner side of the molten salt reactor through an electron accelerator neutron source, counting the energy of the collected neutrons by a neutron receiver, and calculating the neutron shielding performance of the sample using the neutron flux before and after the irradiation.

[0016] Furthermore, nine temperature sensors were embedded in the cylindrical concrete specimen at 3×3 points and connected to a temperature display screen to control and display the internal temperature of the concrete at each point. The internal temperature of the concrete was conducted from the outside to the inside, and the heat transfer coefficient was calculated by formula (1) according to the gradient distribution of cylinders with different radii and a height of 80 mm:

[0017]

[0018] Among them, T' is the heat transfer coefficient, T1, T2...T9 are the temperatures measured by nine temperature sensors respectively;

[0019] The average temperature inside the cylindrical concrete specimen is calculated by formula (2):

[0020]

[0021] in, is the average temperature inside the cylindrical concrete specimen, and r is the radius of the cylindrical concrete specimen.

[0022] Furthermore, the neutron energy-flux curve at high temperature was obtained through experiments. As time goes by, the neutron energy of the device increases. There is a certain functional relationship between the neutron energy and the measurement time, which is calculated by formula (3):

[0023] t=k(x) (3);

[0024] It can be seen from the strain gauge that there is a certain functional relationship between the concrete strain value and time in the cylindrical concrete specimen, which can be calculated by formula (4):

[0025] ε1=L(t)

[0026] ε2=L'(t) (4);

[0027] Among them, x is the neutron energy, t is the test time, ε1 and ε2 are the strain values ​​of the two strain gauges respectively;

[0028] Neutron shielding is calculated by formula (5):

[0029]

[0030] Among them, μ T is the neutron shielding rate of concrete at high temperature, N 0(x) is the neutron flux before shielding, N (x) is the neutron flux after shielding, N E(x) To determine the neutron flux of environmental background samples, a and b are the minimum and maximum neutron energy, respectively;

[0031] The attenuation coefficient of high temperature for concrete neutron shielding efficiency is calculated by formula (6):

[0032]

[0033] μ' is the attenuation coefficient of high temperature neutron shielding rate of concrete, μ N is the neutron shielding rate of concrete at room temperature, T N The temperature is normal temperature.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] The present invention provides a device for measuring the neutron shielding ability of concrete at high temperature, comprising: a neutron emitter, a shielding device and a neutron receiver, wherein the neutron emitter is located at a first side of the shielding device, and the neutron receiver is located at a second side of the shielding device opposite to the first side; the shielding device comprises a bracket and a sample, wherein the sample is arranged on the bracket, and the sample comprises three test samples and a test environment background sample, wherein the three test samples are a control group, a cylindrical concrete specimen and a detection piece group, and a cylindrical concrete specimen group, wherein an ultra-high thermal conductive polymer film layer and a stainless steel alloy casing layer are arranged on the outer side of the cylindrical concrete specimen, and the detection piece comprises a temperature sensor and a strain gauge. The neutron shielding ability is measured by using the above-mentioned device for measuring the neutron shielding ability of concrete at high temperature, thereby realizing an effective measurement of the neutron shielding ability of the warehouse concrete of the new generation molten salt reactor nuclear energy system, and facilitating the thickness design of the neutron shielding concrete in engineering construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic structural diagram of a device for measuring the neutron shielding ability of concrete at high temperature according to an embodiment of the present invention;

[0037] Figure 2 It is a schematic structural diagram of a shielding device in a device for measuring the neutron shielding ability of concrete at high temperature according to an embodiment of the present invention;

[0038] Figure 3 The diagram is a schematic structural diagram of the distribution of samples on a bracket in a device for measuring the neutron shielding ability of concrete at high temperature according to an embodiment of the present invention.

[0039] In the figure:

[0040] 1-temperature sensor, 2-temperature display screen, 3-cylindrical concrete specimen, 4-stainless steel alloy casing layer, 5-ultra-high thermal conductive polymer film layer, 6-strain gauge, 7-bracket, 8-environmental background measurement sample, 9-rolling belt, 10-neutron emitter, 11-neutron receiver. DETAILED DESCRIPTION

[0041] The following is a further detailed description of a device and method for measuring the neutron shielding ability of concrete at high temperatures provided by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will become clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. For the convenience of description, the "upper" and "lower" described below are consistent with the upper and lower directions of the accompanying drawings, but this cannot be a limitation of the technical solution of the present invention.

[0042] Embodiment 1

[0043] A device for measuring the neutron shielding ability of concrete at high temperature comprises: a neutron emitter 10, a shielding device and a neutron receiver 11, wherein the neutron emitter 10 is located at a first side of the shielding device, and the neutron receiver 11 is located at a second side of the shielding device opposite to the first side; the shielding device comprises a bracket 7 and a sample, wherein the sample is arranged on the bracket 7, and the sample comprises three test samples and a measurement environment background sample 8, wherein the three test samples are a control group, a cylindrical concrete specimen and a detection piece group, and a cylindrical concrete specimen group, which are No. 1, No. 2, and No. 3 respectively; an ultrahigh thermal conductive polymer film layer 5 and a stainless steel alloy casing layer 4 are arranged on the outer side of the cylindrical concrete specimen 3 in sequence, and the detection piece comprises a temperature sensor 1 and a strain gauge 6.

[0044] In this embodiment, more preferably, the temperature sensor 1 and the strain gauge 6 in the cylindrical concrete specimen and the detection piece group are pre-buried in the cylindrical concrete specimen 3 , and the temperature sensor 1 is equipped with a temperature display screen 2 , which is located outside the cylindrical concrete specimen 3 .

[0045] In this embodiment, more preferably, the environmental background sample 8 is a 12 cm thick boron-containing polyethylene.

[0046] Please continue to refer to Figures 1 to 3 , a method for determining the neutron shielding ability of concrete at high temperature, the method comprising the following steps:

[0047] Step S1, providing the aforementioned device for measuring the neutron shielding ability of concrete at high temperature for standby use;

[0048] Step S2, heating the stainless steel alloy casing layer 4 by an electric coil, thereby continuously heating the cylindrical concrete specimen 3 and maintaining its temperature at 100-150° C.;

[0049] Step S3, irradiating the sample with a neutron source having an energy range consistent with the inner side of the molten salt reactor through an electron accelerator neutron source, counting the energy of the collected neutrons by a neutron receiver, and calculating the neutron shielding performance of the sample using the neutron flux before and after the irradiation.

[0050] In this embodiment, more preferably, nine temperature sensors are respectively embedded in the cylindrical concrete specimen 3 at points of 3 mm×3 mm, and connected to the temperature display screen 2 to control and display the internal temperature of the concrete at each point. The internal temperature of the concrete is conducted from the outside to the inside, and is distributed in a gradient manner in the form of cylinders with different radii at a height of 80 mm. The heat transfer coefficient is calculated by formula (1):

[0051]

[0052] Wherein, T' is the heat transfer coefficient, T1, T2...T9 are the temperatures measured by the nine temperature sensors 1 respectively; the average temperature inside the cylindrical concrete specimen 3 is calculated by formula (2):

[0053]

[0054] in, is the average temperature inside the cylindrical concrete specimen 3, and r is the radius of the cylindrical concrete specimen 3. The size of the stainless steel alloy casing layer 4 is φ62×80mm. The stainless steel alloy casing layer 4 is heated by an electric coil to transfer the temperature to the inside of the concrete. The intermediate pores between the stainless steel alloy casing layer 4 and the cylindrical concrete specimen 3 are filled with an ultra-high thermal conductive polymer film layer 5. The ultra-high thermal conductive polymer film layer 5 is mainly composed of graphene and carbon nanotubes. Two strain gauges 6 are buried inside the cylindrical concrete specimen 3 to measure the longitudinal deformation of the concrete at high temperature.

[0055] Considering that the internally added detection parts: temperature sensor 1 and strain gauge 6 will affect the determination of concrete neutron flux, a cylindrical concrete specimen group is used to carry out the neutron radiation test.

[0056] In this embodiment, more preferably, a neutron energy-flux curve at high temperature is obtained through experiments. As time goes by, the neutron energy of the device increases, and there is a certain functional relationship between the neutron energy and the measurement time, which is calculated by formula (3):

[0057] t=k(x) (3);

[0058] It can be seen from the strain gauge that there is a certain functional relationship between the concrete strain value and time in the cylindrical concrete specimen 3, which can be calculated by formula (4):

[0059] ε1=L(t)

[0060] ε2=L'(t) (4);

[0061] Among them, x is the neutron energy, t is the test time, ε1 and ε2 are the strain values ​​of the two strain gauges respectively;

[0062] Neutron shielding is calculated by formula (5):

[0063]

[0064] Among them, μ T is the neutron shielding rate of concrete at high temperature, N 0(x) is the neutron flux before shielding, N (x) is the neutron flux after shielding, N E(x) To determine the neutron flux of environmental background samples, a and b are the minimum and maximum neutron energy, respectively;

[0065] The attenuation coefficient of high temperature for concrete neutron shielding efficiency is calculated by formula (6):

[0066]

[0067] μ' is the attenuation coefficient of high temperature neutron shielding rate of concrete, μ N is the neutron shielding rate of concrete at room temperature, T N The temperature is normal temperature.

[0068] During the measurement, a combination of a stainless steel alloy casing layer 4 + an ultra-high thermal conductive polymer film layer 5 is fixed at position 1 of the bracket 7 as an empty bottom to eliminate the influence of the stainless steel alloy casing layer 4 and the ultra-high thermal conductive polymer film layer 5 on the neutron shielding performance of the cylindrical concrete specimen 3.

[0069] A concrete sample with a temperature sensor 1 and a strain gauge 6 is fixed at position 2 of the bracket 7. The heat is transferred to the concrete by electromagnetic heating of the stainless steel alloy casing layer 4. The current of the electromagnetic heating is adjusted by the digital temperature display to ensure that the temperature inside the concrete is within the range of 100-150°C. (Only the temperature and strain are measured for the test block at this position, and the neutron transmittance is not measured).

[0070] A cylindrical concrete specimen 3 is fixed at position 3 of the bracket 7 to measure the neutron transmittance of the concrete at high temperature.

[0071] A 12 cm thick boron-containing polyethylene environmental background sample 8 is fixed at position 4 of the bracket 7 to deduct the environmental background.

[0072] The rack 7 can be moved by the upper rolling belt 9 to neutron irradiate different samples.

[0073] A magnetite concrete was used for the test. The cylindrical concrete specimen 3 had a height of 80 mm and a diameter of 60 mm.

[0074] The temperature measured by temperature sensor 1 is T1=150°C, T2=150°C, T3=150°C, T4=100°C, T5=100°C, T6=100°C, T7=150°C, T8=150°C, T9=150°C.

[0075] According to formulas (1) and (2), the heat transfer coefficient T' = 1.67; the average temperature in the concrete

[0076] The strain gauge 6 data and neutron test data show that ε1 = L(k(x)) = -80x, ε2 = -76x, and the neutron energy range is 10 -8 ~10 -4MeV, calculated from the neutron energy-flux curve:

[0077]

[0078] Calculate μ using formula (5): T =88.89%;

[0079] The room temperature is 20℃, and the concrete neutron shielding rate μ at room temperature is obtained through experiments. N =92.56%. The attenuation coefficient of high temperature for concrete neutron shielding efficiency can be calculated by formula (6), μ' = -0.0325.

[0080] The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. The above embodiments only express several embodiments of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A device for measuring the neutron shielding ability of concrete at high temperature, characterized in that: include: A neutron emitter, a shielding device, and a neutron receiver, wherein the neutron emitter is located on a first side of the shielding device, and the neutron receiver is located on a second side of the shielding device opposite to the first side; The shielding device includes a bracket and a sample, the sample is arranged on the bracket, and the sample includes three test samples and one measurement environment background sample, the three test samples are a control group, a cylindrical concrete specimen and a detection piece group, and a cylindrical concrete specimen group, respectively, an ultra-high thermal conductive polymer film layer and a stainless steel alloy casing layer are arranged in sequence on the outside of the cylindrical concrete specimen, and the detection piece includes a temperature sensor and a strain gauge.

2. The device for measuring the neutron shielding ability of concrete at high temperature according to claim 1, characterized in that: The temperature sensor and strain gauge in the cylindrical concrete specimen and the detection piece group are pre-buried in the cylindrical concrete specimen, and the temperature sensor is equipped with a temperature display screen, which is located outside the cylindrical concrete specimen.

3. The device for measuring the neutron shielding ability of concrete at high temperature according to claim 1, characterized in that: The environmental background sample for determination is 12 cm thick boron-containing polyethylene.

4. A method for determining the neutron shielding capability of concrete at high temperatures, characterized in that: The steps include: Step S1, providing a device for measuring the neutron shielding ability of concrete at high temperature as described in any one of claims 1 to 3 for standby use; Step S2, heating the stainless steel alloy casing layer by an electric coil, thereby continuously heating the cylindrical concrete specimen and maintaining its temperature at 100-150° C.; Step S3, irradiating the sample with a neutron source having an energy range consistent with the inner side of the molten salt reactor through an electron accelerator neutron source, counting the energy of the collected neutrons by a neutron receiver, and calculating the neutron shielding performance of the sample using the neutron flux before and after the irradiation.

5. The measuring method according to claim 4, characterized in that Nine temperature sensors were embedded in the cylindrical concrete specimen at 3×3 points and connected to a temperature display screen to control and display the internal temperature of the concrete at each point. The internal temperature of the concrete was conducted from the outside to the inside, and the heat transfer coefficient was calculated by formula (1) according to the gradient distribution of cylinders with different radii and a height of 80 mm: Among them, T' is the heat transfer coefficient, T1, T2...T9 are the temperatures measured by nine temperature sensors respectively; The average temperature inside the cylindrical concrete specimen is calculated by formula (2): in, is the average temperature inside the cylindrical concrete specimen, and r is the radius of the cylindrical concrete specimen.

6. The measuring method according to claim 5, characterized in that The neutron energy-flux curve at high temperature was obtained through experiments. As time goes by, the neutron energy of the device increases. There is a certain functional relationship between the neutron energy and the measurement time, which is calculated by formula (3): t=k(x) (3); It can be seen from the strain gauge that there is a certain functional relationship between the concrete strain value and time in the cylindrical concrete specimen, which can be calculated by formula (4): ε1=L(t) ε2=L'(t) (4); Among them, x is the neutron energy, t is the test time, ε1 and ε2 are the strain values ​​of the two strain gauges respectively; Neutron shielding is calculated by formula (5): Among them, μ T is the neutron shielding rate of concrete at high temperature, N 0(x) is the neutron flux before shielding, N (x) is the neutron flux after shielding, N E(x) To determine the neutron flux of environmental background samples, a and b are the minimum and maximum neutron energy, respectively; The attenuation coefficient of high temperature for concrete neutron shielding efficiency is calculated by formula (6): μ' is the attenuation coefficient of high temperature neutron shielding rate of concrete, μ N is the neutron shielding rate of concrete at room temperature, T N The temperature is normal temperature.

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