A method for calculating aerosol deposition efficiency in a steel containment microchannel

Abstract

The invention discloses a method for calculating aerosol deposition efficiency in a micro-channel of a steel containment, comprising step 1: judging whether geometric parameters of the micro-channel of the steel containment can be obtained, namely obtaining relevant parameters such as the cross-sectional area, geometric shape, and geometric size of the micro-channel; step 2: if the parameters can be obtained, calculating the aerosol deposition efficiency in the micro-channel by means of a control equation and a flow equation; step 3: if the parameters cannot be obtained, calculating the aerosol deposition efficiency in the micro-channel by means of a containment leakage rate; and step 4: determining the final aerosol deposition efficiency in the micro-channel of the steel containment.

Description

Technical Field

[0001] The invention relates to the field of aerosol calculation, and in particular to a method for calculating aerosol deposition efficiency in a steel containment micro-channel. Background Art

[0002] The containment of a nuclear power plant is the boundary separating the containment atmosphere from the outside environment and is the last safety barrier to prevent the release of fission products into the environment. The surface structure of the steel containment is complex, with a large number of gates, valves, penetrations, connectors and other components. Under complex and harsh working conditions, the integrity of the containment seal is easily damaged, causing the radioactive aerosol inside the shell to leak into the outside atmosphere, causing radioactive contamination.

[0003] The surface components of the containment are prone to cracking and forming micro-channels due to long working hours, harsh working environment, and assembly process. The deposition of aerosols in micro-channels is directly related to the diffusion of radioactive substances in the external environment. Existing studies have not considered the impact of micro-channels on aerosol deposition, resulting in inaccurate source term assessment. Therefore, it is necessary to study the aerosol deposition efficiency of micro-channels formed by cracks in the containment.

[0004] The invention is based on geometric parameters of a steel containment micro-channel and considers various aerosol deposition mechanisms, and proposes a calculation method for aerosol deposition efficiency of a steel containment micro-channel based on geometric parameters. Summary of the invention

[0005] In order to overcome the deficiencies in the prior art, the present invention provides a method for calculating the aerosol deposition efficiency in a micro-channel of a steel containment. On the premise that the steel containment maintains its sealing integrity, the deposition efficiency of the radioactive aerosol through the micro-channel is calculated based on geometric parameters, thereby accurately evaluating the source term.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted to solve the technical problem is as follows:

[0007] A method for calculating aerosol deposition efficiency in a steel containment microchannel comprises the following steps:

[0008] Step 1: Determine whether the geometric parameters of the micro-channel of the steel containment can be obtained, that is, obtain the cross-sectional area, geometric shape, geometric dimensions and other related parameters of the micro-channel;

[0009] Step 2: If it can be obtained, calculate the aerosol deposition efficiency in the microchannel through the control equation and flow equation;

[0010] Step 3: If it cannot be obtained, the aerosol deposition efficiency in the microchannel is calculated by the containment leakage rate;

[0011] Step 4: Determine the aerosol deposition efficiency of the final steel containment microchannel.

[0012] Furthermore, step 2 specifically includes the following steps:

[0013] Step 2.1: According to the flow control equation of the fluid in the micro-channel with equal cross-section, the relationship between the fluid flow velocity v and the friction coefficient f is obtained;

[0014] Step 2.2: Select the friction coefficient according to the cross-sectional geometry of the microchannel;

[0015] Step 2.3: Substitute the friction coefficient selected in step 2.2 into step 2.1 to calculate the fluid flow rate;

[0016] Step 2.4: Calculate the mass flow rate of the micro-channel;

[0017] Step 2.5: Calculate the gravity deposition efficiency based on the different cross-sectional geometries of the microchannel;

[0018] Step 2.6: Calculate the deposition efficiencies of Brownian diffusion, turbulent deposition, thermophoretic deposition, and diffusion migration.

[0019] Furthermore, the flow control equation of the gas in the uniform cross-section micro-channel described in step 2.1 is derived from the control equation, and the specific process is as follows:

[0020] Assuming isothermal gas flow, the width of the microchannel is constant and much smaller than the channel length and height, the fluid is fully developed in the flow channel, and there is no need to consider the end effect. The control equation is as follows:

[0021]

[0022] Where Ma is the Mach number of the fluid, A is the cross-sectional area of ​​the microchannel, W is the width of the microchannel, v is the velocity of the fluid, and c is the local sound speed;

[0023] Based on the control equation, assuming that the micro-channel has a constant cross-section flow dA = 0, the flow control equation of the fluid in the micro-channel with a constant cross-section is as follows:

[0024]

[0025] Where L is the length of the microchannel.

[0026] Further, in step 2.2, if the equivalent diameter of the microchannel is in the order of millimeters or above, the friction coefficient formula is as follows:

[0027]

[0028] Where f is the friction coefficient, Re is the Reynolds number, ρ is the density of the fluid, and d is pis the equivalent diameter of the microchannel, μ is the dynamic viscosity of the fluid;

[0029] If the equivalent diameter of the microchannel is below the millimeter level, the friction coefficient calculation formula is as follows:

[0030]

[0031] Further, in step 2.4, assuming that the inlet loss of the micro-channel is half the dynamic pressure head, the mass flow rate of the micro-channel is calculated, and the calculation formula is as follows:

[0032]

[0033] In the formula, Q m is the mass flow rate of the micro-channel, and P2 is the pressure downstream of the micro-channel;

[0034] Assuming that each deposition mechanism is independent of each other, the total deposition efficiency is the product of the deposition efficiencies of each mechanism.

[0035] Furthermore, in step 2.5, the flow pattern in the microchannel is turbulent. Since different cross-sectional geometric shapes will lead to different projection surfaces of gravity deposition velocity, the gravity deposition efficiency is calculated first:

[0036] v d(sed) =τgsinθ

[0037]

[0038] Circular and other cross-sections:

[0039]

[0040] rectangle:

[0041]

[0042]

[0043] Furthermore, in step 2.6, the Brownian diffusion deposition, turbulent deposition, thermophoretic deposition and diffusion migration deposition efficiencies are calculated respectively:

[0044] (1) Brownian diffusion deposition efficiency:

[0045] η 布朗扩散-湍流 =e (-ξsh)

[0046]

[0047]

[0048]

[0049] Where sh is the Sherwood number, Sc is the Schmidt number, and D is the particle diffusion coefficient;

[0050] (2) Turbulent deposition efficiency:

[0051]

[0052]

[0053] V+=6×10 -4 τ 2 + +2×10 -8 Re f

[0054]

[0055] Where Vt is the turbulent inertial deposition velocity, V+ is the dimensionless deposition velocity, τ+ is the dimensionless particle relaxation time, and Stk is the Stokes constant related to the pipe diameter and the air flow velocity inside the pipe;

[0056] (3) Thermophoretic deposition efficiency:

[0057]

[0058]

[0059] In the formula, C s =1.13, C t =2.63, C m =1.14, Kn is the particle Knudsen number: twice the mean free path of gas molecules divided by the particle diameter d pa , C(kn) is the slip correction coefficient;

[0060] (4) Diffusion migration deposition efficiency

[0061]

[0062]

[0063] In the formula, m1 is the molecular weight of the diffusing substance, m2 is the molecular weight of the stationary substance, γ1 is the amount of substance of the diffusing substance, γ2 is the amount of substance of the stationary substance, is the amount gradient of the diffusing substance.

[0064] Furthermore, step 3 specifically includes the following steps:

[0065] Step 3.1: Select different leakage rates according to the pressure inside the containment to calculate the leakage flow Q1;

[0066] Step 3.2: Determine whether the flow in the microchannel is critical based on the pressure inside the containment and the external environment pressure, and calculate: leakage flow Q2;

[0067] Step 3.3: According to Q1=Q2, calculate the equivalent geometric area A of the total leakage channel of the containment;

[0068] Step 3.4: According to the different geometric shapes of cracks formed by cracking of containment components, the total geometric area of ​​the leakage channel is divided into the sum of the areas of different cross-sectional shapes;

[0069] Step 3.5: Based on the turbulent flow state in the microchannel, the deposition mechanism is gravity deposition, Brownian diffusion deposition, turbulent deposition, thermophoretic deposition and diffusion migration deposition, and the total deposition efficiency of microchannel aerosol is calculated.

[0070] Further, in step 3.1, first determine whether the pressure inside the containment of the nuclear power plant is greater than the design pressure of the containment. If it is less than or equal to the design pressure of the containment, the leakage rate inside the containment is the design leakage rate; if the pressure of the containment is greater than the design pressure, the excessive pressure of the containment will cause the original cracks in the containment to further crack, and the number and size of the leakage channels will change. Therefore, when the pressure is greater than the design pressure of the containment, the correction factor K is introduced to correct the original design leakage rate, reflecting the actual leakage rate of the containment as the pressure increases:

[0071]

[0072] Where, L 泄漏 is the actual leakage rate of the containment, L 设计 is the containment design leakage rate, K is the containment leakage rate correction factor, P 设计压力 Design pressure for containment;

[0073] The leakage mass flow rate of the micro-channel is calculated based on the actual free volume of the containment of the nuclear power plant and the actual leakage rate. The calculation formula is as follows:

[0074]

[0075] Where Q1 is the mass flow rate of leakage in the micro-channel, V 自由 is the free volume of the nuclear power plant containment; L 泄漏 is the actual leakage rate of the nuclear power plant, ρ 混合 is the fluid density in the containment (mixture of air and water vapor), and t is the leakage time.

[0076] Further, in step 3.2, it is determined whether the microchannel is in a critical flow state according to the pressure inside the containment and the pressure outside the containment. If the downstream pressure (pressure outside the containment) P2>P chock , then the microchannel is in a critical flow state; if P2 <Pchock , then the microchannel is in a non-critical flow state; depending on whether the channel is critical, the mass flow calculation formula in the microchannel is different, and the calculation formula is as follows:

[0077]

[0078] Where P chock is the maximum downstream pressure that determines the maximum flow rate through the microchannel, P1 is the upstream pressure of the microchannel (pressure inside the containment), γ is the specific heat capacity of the fluid, C p is the constant pressure specific heat of the fluid, C v is the constant volume specific heat of the fluid;

[0079]

[0080] In the formula, C0 is the flow coefficient, which is 0.75; g c is the acceleration due to gravity, M is the molar mass of the fluid, R g is the ideal gas constant, T0 is the temperature inside the containment, A 等效 is the equivalent area of ​​the micro channel.

[0081] Further, in step 3.4, according to the definition of the design leakage rate of the nuclear power plant and the classification of the actual structural components of the containment, the leakage rate of the containment is divided into two parts: the overall leakage rate and the local leakage rate (penetrations and valves). Therefore, the calculation formula of the containment leakage rate is as follows:

[0082] L 泄漏 =L1+L2+L3

[0083] Where, L2 is the local leakage rate caused by the penetration, and L3 is the local leakage rate caused by the valve;

[0084] The cross-sectional geometric shapes of cracks formed by cracks in different parts of the containment are different. The containment surface cracks due to pressure and other reasons form small circular cracks, annular cracks formed between the penetration and the containment surface, and rectangular cracks formed between the valve seal and the surface. According to the different geometric shapes of the cracks, the total leakage channel equivalent geometric area is divided into the sum of the areas of different cross-sectional shapes:

[0085]

[0086] Where A1 is the equivalent geometric area of ​​small circular cracks on the surface of the containment, A2 is the equivalent area of ​​annular cracks formed between the penetration and the surface of the containment, and A3 is the equivalent area of ​​rectangular cracks formed between the valve seal and the surface of the containment.

[0087] Further, in step 3.5, the flow velocity of the micro-channel fluid is calculated based on the containment leakage mass flow obtained in step 3.1. The flow type in the micro-channel is judged to be turbulent based on the Reynolds number. The deposition mechanism is gravity deposition, Brownian diffusion deposition, turbulent deposition, thermophoresis deposition and diffusion migration deposition. The total deposition efficiency of the micro-channel aerosol is calculated as:

[0088] Qm=ρA 等效 v

[0089]

[0090] (1) Gravity sedimentation efficiency:

[0091] v d(sed) =τgsinθ

[0092]

[0093] Circular microchannel:

[0094]

[0095] Annular microchannel:

[0096]

[0097] Rectangular microchannel:

[0098]

[0099]

[0100] Where V d(sed) is the gravity deposition velocity, θ is the angle between the gas flow direction and gravity, ρ p is the aerosol particle density, d pa is the diameter of aerosol particles, C c is the Cunningham slip correction factor, C is the aerosol mass concentration, r2 is the outer ring diameter of the equivalent annular channel, and r1 is the outer ring diameter of the equivalent annular channel;

[0101] (2) Brownian diffusion deposition:

[0102] η tube,diff =e (-ξsh)

[0103]

[0104]

[0105] (3) Turbulent deposition:

[0106]

[0107]

[0108] V+=6×10 -4 τ 2 + +2×10 -8 Re f

[0109]

[0110] (4) Thermophoretic deposition:

[0111]

[0112]

[0113] (5) Diffusion migration deposition:

[0114]

[0115]

[0116] (6) Total deposition efficiency:

[0117] η 总沉积 =η 重力 ·η 布朗 ·η 湍流 ·η 热泳 ·η 扩散迁移 .

[0118] Further, step 4, the final total deposition efficiency of the micro-channel of the steel containment is determined according to the above steps:

[0119]

[0120] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art:

[0121] 1. This method can solve the aerosol deposition efficiency through the flow equation when the geometric parameters of the micro-channel (channel cross-sectional geometry, size, etc.) are known. When the geometric parameters of the micro-channel are unknown, the aerosol deposition efficiency is calculated according to the actual leakage rate of the containment to accurately evaluate the source term;

[0122] 2. When calculating the gravity deposition efficiency of aerosols through micro-channels, this method divides the geometric shapes of micro-channels into equivalent circles, rectangles and rings according to the different forms of containment leakage, because the containment leakage is caused by surface leakage, local penetration leakage and local valve leakage, instead of uniformly equivalent to circular channels. This solves the problem of different projection surfaces of gravity deposition mechanisms on different cross-sectional geometric shapes and reduces the calculation error of gravity deposition efficiency.

[0123] 3. In the case of unknown geometric parameters, when the containment pressure is higher than the design pressure, this method proposes a K correction factor to correct the design leakage rate to avoid the phenomenon that the number and size of leakage channels change due to excessive pressure, and the leakage flow calculation is inaccurate. In addition, when calculating the flow, whether there is critical flow in the channel is determined based on the upstream and downstream pressures to reduce the flow calculation error. BRIEF DESCRIPTION OF THE DRAWINGS

[0124] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. 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 work. In the drawings:

[0125] Figure 1 It is a flow chart of a method for calculating aerosol deposition efficiency in a steel containment microchannel of the present invention;

[0126] Figure 2 It is a schematic diagram of the circular aerosol gravity deposition projection surface;

[0127] Figure 3 It is a schematic diagram of the rectangular aerosol gravity deposition projection surface;

[0128] Figure 4 Schematic diagram of the circular aerosol gravity deposition projection surface. DETAILED DESCRIPTION

[0129] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0130] like Figure 1 As shown, the present invention is used for the calculation method of aerosol deposition efficiency in a steel containment micro-channel, and the steps are as follows:

[0131] 1. Geometric parameters of the known leaking microchannel (cross-sectional area 3.14×10 -6m 2 , the geometry is a circular channel, the channel length is 1m, and the channel radius is 0.001m)

[0132] Assuming that the fluid in the microchannel is isothermal, the channel width is constant and much smaller than the length and height of the channel, the fluid is fully developed in the flow channel, and the end effect does not need to be considered in the calculation. The flow in the channel is a flow of equal cross-section dA = 0, and the relationship between the Mach number Ma and the friction coefficient f is obtained:

[0133]

[0134] Where, L is the length of the microchannel;

[0135] Given a circular channel,

[0136]

[0137] Assuming that the inlet loss of the micro-channel is half the dynamic pressure head, calculate the mass flow rate in the micro-channel:

[0138]

[0139] In the formula, Q m is the mass flow rate of the micro-channel, and P2 is the pressure downstream of the micro-channel;

[0140] According to the Reynolds number, the flow type in the microchannel is turbulent flow. Assuming that the deposition mechanisms in the microchannel are independent of each other, the total deposition mechanism is gravity deposition, Brownian diffusion deposition, turbulent deposition, thermophoresis deposition and diffusion migration deposition.

[0141] (1) Gravity sedimentation efficiency:

[0142] v d(sed) =τgsinθ

[0143]

[0144]

[0145] (2) Brownian diffusion deposition efficiency:

[0146]

[0147] η 布朗扩散-层流 =0.819e (-3.657ξ) +0.097e (-22.3ξ) +0.032e (-57ξ) ,ξ>0.02

[0148]

[0149] Where D is the particle diffusion coefficient;

[0150] (3) Turbulent deposition efficiency:

[0151]

[0152]

[0153] V+=6×10 -4 τ 2 + +2×10 -8 Re f

[0154]

[0155] Where Vt is the turbulent inertial deposition velocity, V+ is the dimensionless deposition velocity, τ+ is the dimensionless particle relaxation time, and Stk is the Stokes constant related to the pipe diameter and the air flow velocity inside the pipe;

[0156] (4) Thermophoretic deposition efficiency:

[0157]

[0158]

[0159] In the formula, C s =1.13, C t =2.63, C m =1.14, Kn is the particle Knudsen number: twice the mean free path of gas molecules divided by the particle diameter d pa , C(kn) is the slip correction coefficient;

[0160] (5) Diffusion migration deposition efficiency:

[0161]

[0162]

[0163] In the formula, m1 is the molecular weight of the diffusing substance, m2 is the molecular weight of the stationary substance, γ1 is the amount of substance of the diffusing substance, γ2 is the amount of substance of the stationary substance, is the amount gradient of the diffusing substance.

[0164] The total deposition efficiency is the product of the deposition efficiencies of the above-mentioned independent mechanisms;

[0165] η 总沉积 =η 重力 ·η 布朗 ·η 湍流 ·η 热泳 ·η 扩散迁移

[0166] 2. Geometric parameters of unknown leakage microchannels (given the free volume V of the nuclear power plant containment 自由 , design leakage rate L 泄漏 , the pressure inside the containment is greater than the design pressure)

[0167] According to the fact that the pressure inside the containment is greater than the design pressure, the actual leakage rate of the containment is obtained:

[0168] L 泄漏 = k·L 设计

[0169] Where, L 泄漏 is the actual leakage rate of the containment, L 设计 is the containment design leakage rate, K is the containment leakage rate correction factor, P 设计压力 Design pressure for containment;

[0170] The leakage mass flow rate of the tiny channel is calculated based on the actual free volume of the containment of the nuclear power plant and the actual leakage rate:

[0171]

[0172] Where Q1 is the mass flow rate of leakage in the micro-channel, V 自由 is the free volume of the nuclear power plant containment; L 泄漏 is the actual leakage rate of the nuclear power plant, ρ 混合 is the fluid density in the containment (mixture of air and water vapor), and t is the leakage time.

[0173] According to the downstream pressure (pressure outside the containment) P2>P chock , the micro-channel is in a critical flow state, and the mass flow rate in the micro-channel is calculated.

[0174]

[0175]

[0176] Where P chock is the maximum downstream pressure that determines the maximum flow rate through the microchannel, P1 is the upstream pressure of the microchannel (pressure inside the containment), γ is the specific heat capacity of the fluid, C p is the constant pressure specific heat of the fluid, C v is the constant volume specific heat of the fluid;

[0177] According to Q1=Q2, the equivalent geometric area A of the total leakage channel of the containment is calculated. According to the definition of the design leakage rate of the nuclear power plant and the classification of the actual structural components of the containment, the leakage rate of the containment is divided into two parts: the overall leakage rate and the local leakage rate (penetrations and valves). According to existing research, the local leakage rate caused by penetrations is 0.1 of the overall leakage rate, and the local leakage rate caused by valves is 0.5 of the overall leakage rate.

[0178] L 泄漏 =L1+L2+L3

[0179] L2=0.1L 泄漏

[0180] L3=0.5L 泄漏

[0181] L1=L 泄漏 -L2-L3=0.4L 泄漏

[0182] Where, L2 is the local leakage rate caused by the penetration, and L3 is the local leakage rate caused by the valve;

[0183] The cross-sectional geometric shapes of cracks formed by cracks in different parts of the containment are different: small circular cracks formed by cracks on the surface of the containment due to pressure and other reasons, annular cracks formed between the penetration and the surface of the containment, and rectangular cracks formed between the valve seal and the surface. According to the different geometric shapes of the cracks, the total leakage channel equivalent geometric area is divided into the sum of the areas of different cross-sectional shapes.

[0184] A 等效 =0.4A1+0.1A2+0.5A3

[0185] Where A1 is the equivalent geometric area of ​​small circular cracks on the surface of the containment, A2 is the equivalent area of ​​annular cracks formed between the penetration and the surface of the containment, and A3 is the equivalent area of ​​rectangular cracks formed between the valve seal and the surface of the containment.

[0186] According to the containment leakage mass flow rate obtained in step 3.1, the flow velocity of the micro-channel fluid is calculated. According to the Reynolds number, the flow type in the micro-channel is judged to be turbulent, and the deposition mechanism is gravity deposition, Brownian diffusion deposition, turbulent deposition, thermophoresis deposition and diffusion migration deposition. The total deposition efficiency of the micro-channel aerosol is calculated.

[0187] Qm=ρA 等效 v

[0188]

[0189] (1) Gravity sedimentation efficiency:

[0190] v d(sed) =τgsinθ

[0191]

[0192] Circular microchannel:

[0193]

[0194] Annular microchannel:

[0195]

[0196] Rectangular microchannel:

[0197]

[0198]

[0199] Where V d(sed) is the gravity deposition velocity, θ is the angle between the gas flow direction and gravity, ρ p is the aerosol particle density, d pa is the diameter of aerosol particles, C c is the Cunningham slip correction factor, C is the aerosol mass concentration, r2 is the outer ring diameter of the equivalent annular channel, and r1 is the outer ring diameter of the equivalent annular channel;

[0200] (2) Brownian diffusion deposition:

[0201] η tube,diff =e (-ξsh)

[0202]

[0203]

[0204] (3) Turbulent deposition:

[0205]

[0206]

[0207] V+=6×10 -4 τ 2 + +2×10 -8 Re f

[0208]

[0209] (4) Thermophoretic deposition:

[0210]

[0211]

[0212] (5) Diffusion migration deposition:

[0213]

[0214]

[0215] (6) Total deposition efficiency:

[0216] η 总沉积 =η 重力 ·η 布朗 ·η 湍流 ·η 热泳 ·η 扩散迁移

[0217] This method is based on geometric parameters. For the aerosol deposition efficiency of the micro-channel of the steel containment, according to steps 1-4, the aerosol deposition efficiency of the micro-channel under different geometric parameters, different flow states, and different deposition mechanisms is finally determined. The radioactive aerosol deposition efficiency in the steel containment calculated in the end is of great significance for the safety analysis of nuclear power plants and the accurate assessment of source terms.

[0218] It is obvious to those skilled in the art that the method of the present invention is not limited to the details of the above exemplary embodiments, and that the method of the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention.

[0219] Therefore, no matter from which point of view, the embodiments should be regarded as illustrative and non-restrictive, and the scope of the present invention is limited by the appended claims rather than the above description, so it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0220] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for calculating aerosol deposition efficiency in a steel containment microchannel, characterized in that: The following steps are involved: Step 1: Determine whether the geometric parameters of the micro-channel of the steel containment can be obtained, that is, the cross-sectional area, geometric shape, and channel geometric size related parameters of the micro-channel can be obtained; Step 2: If it can be obtained, calculate the aerosol deposition efficiency in the microchannel through the control equation and flow equation; Step 2 specifically includes the following steps: Step 2.1: According to the flow control equation of the fluid in the micro-channel with equal cross-section, the relationship between the fluid flow velocity v and the friction coefficient f is obtained; Step 2.2: Select the friction coefficient according to the cross-sectional geometry of the microchannel; Step 2.3: Substitute the friction coefficient selected in step 2.2 into step 2.1 to calculate the fluid flow rate; Step 2.4: Calculate the mass flow rate of the micro-channel; Step 2.5: Calculate the gravity deposition efficiency based on the different cross-sectional geometries of the microchannel; Step 2.6: Calculate the deposition efficiencies of Brownian diffusion, turbulent deposition, thermophoretic deposition, and diffusion migration; Step 3: If it cannot be obtained, the aerosol deposition efficiency in the microchannel is calculated by the containment leakage rate; Step 3 specifically includes the following steps: Step 3.1: Select different leakage rates according to the pressure inside the containment to calculate the leakage flow Q1; Step 3.2: Determine whether the flow in the microchannel is critical based on the pressure inside the containment and the external environment pressure, and calculate: leakage flow Q2; Step 3.3: According to Q1=Q2, calculate the equivalent geometric area A of the total leakage channel of the containment; Step 3.4: According to the different geometric shapes of cracks formed by cracking of containment components, the total geometric area of ​​the leakage channel is divided into the sum of the areas of different cross-sectional shapes; Step 3.5: Based on the turbulent flow state in the microchannel, the deposition mechanism is gravity deposition, Brownian diffusion deposition, turbulent deposition, thermophoretic deposition and diffusion migration deposition, and the total deposition efficiency of the microchannel aerosol is calculated; Step 4: Determine the aerosol deposition efficiency of the final steel containment microchannel; Step 4: Determine the final total deposition efficiency of the micro-channel of the steel containment according to the above steps:

2. The method for calculating aerosol deposition efficiency in a steel containment microchannel according to claim 1, characterized in that: The flow control equation of the micro-channel gas described in step 2.1 is derived from the control equation, and the specific process is as follows: Assuming isothermal gas flow, the width of the microchannel is constant and much smaller than the channel length and height, the fluid is fully developed in the flow channel, and there is no need to consider the end effect. The control equation is as follows: In the formula, Ma is the Mach number of the fluid, A is the cross-sectional area of ​​the micro-channel, W is the width of the micro-channel, v is the velocity of the fluid, and c is the local sound speed; Based on the control equation, assuming that the micro-channel has a constant cross-section flow dA = 0, the flow control equation of the fluid in the micro-channel with a constant cross-section is as follows: Where L is the length of the microchannel.

3. The method for calculating aerosol deposition efficiency in a steel containment microchannel according to claim 2, characterized in that: Step 2.2, if the equivalent diameter of the microchannel is in the order of millimeters or above, the friction coefficient formula is as follows: Where f is the friction coefficient, Re is the Reynolds number, ρ is the density of the fluid, and d is p is the equivalent diameter of the microchannel, μ is the dynamic viscosity of the fluid; If the equivalent diameter of the microchannel is below the millimeter level, the friction coefficient calculation formula is as follows:

4. The method for calculating aerosol deposition efficiency in a steel containment microchannel according to claim 3, characterized in that: Step 2.4, assuming that the inlet loss of the micro-channel is half the dynamic pressure head, calculate the mass flow rate of the micro-channel, the calculation formula is as follows: In the formula, Q m is the mass flow rate of the micro-channel, and P2 is the pressure downstream of the micro-channel; Assuming that each deposition mechanism is independent of each other, the total deposition efficiency is the product of the deposition efficiencies of each mechanism.

5. A method for calculating aerosol deposition efficiency in a steel containment microchannel according to claim 4, characterized in that: Step 2.5, the flow type in the microchannel is turbulent. Since different cross-sectional geometric shapes will lead to different projection surfaces of gravity deposition velocity, the gravity deposition efficiency is calculated first: v d(sed) =τgsinθ Circular and other cross-sections: rectangle: Where θ is the angle between the gas flow direction and gravity, C c is the Cunningham slip correction factor, C is the aerosol mass concentration, Q m is the mass flow rate of the micro channel.

6. A method for calculating aerosol deposition efficiency in a steel containment microchannel according to claim 5, characterized in that: Step 2.6, calculate the Brownian diffusion deposition, turbulent deposition, thermophoretic deposition and diffusion migration deposition efficiencies respectively: (1) Brownian diffusion deposition efficiency: Where sh is the Sherwood number, Sc is the Schmidt number, and D is the particle diffusion coefficient; (2) Turbulent deposition efficiency: V+=6×10 -4 τ 2 + +2×10 -8 Re f Where Vt is the turbulent inertial deposition velocity, V+ is the dimensionless deposition velocity, τ+ is the dimensionless particle relaxation time, and Stk is the Stokes constant related to the pipe diameter and the air flow velocity inside the pipe; (3) Thermophoretic deposition efficiency: In the formula, C s =1.13, C t =2.63, C m =1.14, Kn is the particle Knudsen number: twice the mean free path of gas molecules divided by the particle diameter d pa , C(kn) is the slip correction coefficient; (4) Diffusion migration deposition efficiency In the formula, m1 is the molecular weight of the diffusing substance, m2 is the molecular weight of the stationary substance, γ1 is the amount of substance of the diffusing substance, γ2 is the amount of substance of the stationary substance, and ▽γ1 is the amount gradient of the diffusing substance.

7. The method for calculating aerosol deposition efficiency in a steel containment microchannel according to claim 1, characterized in that: Step 3.1, first determine whether the pressure inside the containment of the nuclear power plant is greater than the design pressure of the containment. If it is less than or equal to the design pressure of the containment, the leakage rate inside the containment is the design leakage rate; if the pressure of the containment is greater than the design pressure, the excessive pressure of the containment will cause the original cracks in the containment to further crack, and the number and size of the leakage channels will change. Therefore, when the pressure is greater than the design pressure of the containment, the correction factor K is introduced to correct the original design leakage rate, reflecting the actual leakage rate of the containment as the pressure increases: Where, L 泄漏 is the actual leakage rate of the containment, L 设计 is the containment design leakage rate, K is the containment leakage rate correction factor, P 设计压力 Design pressure for containment; The leakage mass flow rate of the micro-channel is calculated based on the actual free volume of the containment of the nuclear power plant and the actual leakage rate. The calculation formula is as follows: Where Q1 is the mass flow rate of leakage in the micro-channel, V 自由 is the free volume of the nuclear power plant containment; L 泄漏 is the actual leakage rate of the nuclear power plant, ρ 混合 is the density of the mixture of air and water vapor in the containment, and t is the leakage time.

8. A method for calculating aerosol deposition efficiency in a steel containment microchannel according to claim 7, characterized in that: Step 3.2, determine whether the microchannel is in a critical flow state based on the pressure inside and outside the containment. If the downstream pressure, i.e., the pressure outside the containment, P2>P chock , then the microchannel is in a critical flow state; if P2 <P chock , then the microchannel is in a non-critical flow state; depending on whether the channel is critical, the mass flow calculation formula in the microchannel is different, and the calculation formula is as follows: Where P chock is the maximum downstream pressure that determines the maximum flow rate through the micro-channel, P1 is the upstream pressure of the micro-channel, that is, the pressure inside the containment, γ is the specific heat capacity of the fluid, C p is the constant pressure specific heat of the fluid, C v is the constant volume specific heat of the fluid; In the formula, C0 is the flow coefficient, which is 0.75; g c is the acceleration due to gravity, M is the molar mass of the fluid, R g is the ideal gas constant, T0 is the temperature inside the containment, A 等效 is the equivalent area of ​​the micro channel.

9. A method for calculating aerosol deposition efficiency in a steel containment microchannel according to claim 8, characterized in that: Step 3.4, according to the definition of nuclear power plant design leakage rate and the classification of actual containment structural components, the containment leakage rate is divided into two parts: overall leakage rate and local leakage rate. The local leakage rate is the sum of the leakage rates caused by penetrations and valves. Therefore, the calculation formula for the containment leakage rate is as follows: <h2 style=";text-align:left;direction:ltr">L<h2 style=";text-align:left;direction:ltr"> 泄漏 <h2 style=";text-align:left;direction:ltr"> (L1+L2+L3) Where, L2 is the local leakage rate caused by the penetration, and L3 is the local leakage rate caused by the valve; The cross-sectional geometric shapes of cracks formed by cracks in different parts of the containment are different. The containment surface cracks due to pressure cause small circular cracks, annular cracks formed between the penetration and the containment surface, and rectangular cracks formed between the valve seal and the surface. According to the different geometric shapes of the cracks, the total leakage channel equivalent geometric area is divided into the sum of the areas of different cross-sectional shapes: Where A1 is the equivalent geometric area of ​​small circular cracks on the surface of the containment, A2 is the equivalent area of ​​annular cracks formed between the penetration and the surface of the containment, and A3 is the equivalent area of ​​rectangular cracks formed between the valve seal and the surface of the containment.

10. A method for calculating aerosol deposition efficiency in a steel containment microchannel according to claim 9, characterized in that: Step 3.5, according to the containment leakage mass flow obtained in step 3.1, the flow velocity of the micro-channel fluid is calculated, and the flow type in the micro-channel is judged to be turbulent according to the Reynolds number. The deposition mechanism is gravity deposition, Brownian diffusion deposition, turbulent deposition, thermophoresis deposition and diffusion migration deposition. The total deposition efficiency of the micro-channel aerosol is calculated: Qm=ρA 等效 v In the formula, Q m is the mass flow rate of the micro-channel; (1) Gravity sedimentation efficiency: v d(sed) =τgsinθ Circular microchannel: Annular microchannel: Rectangular microchannel: Where V d(sed) is the gravity deposition velocity, θ is the angle between the gas flow direction and gravity, ρ p is the aerosol particle density, d p is the diameter of aerosol particles, C c is the Cunningham slip correction factor, C is the aerosol mass concentration, r2 is the outer ring diameter of the equivalent annular channel, and r1 is the outer ring diameter of the equivalent annular channel; (2) Brownian diffusion deposition: or tube,diff =e (-ξsh) (3) Turbulent deposition: V+=6×10 -4 τ 2 + +2×10 -8 Re f (4) Thermophoretic deposition: (5) Diffusion migration deposition: (6) Total deposition efficiency: or 总沉积 =the 重力 ·or 布朗 ·or 湍流 ·or 热泳 ·or 扩散迁移 。

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