A method and apparatus for predicting corrosion fouling deposits on fuel rod cladding

Abstract

The application provides a method and device for predicting corrosion fouling deposition layer of fuel rod cladding, the method comprising: performing neutron physical field analysis calculation on the pellets of the fuel rod to obtain the volume heat release rate of the pellets; on the basis of the current cladding surface temperature, calculating the deposition thickness of the corrosion fouling deposition layer of the fuel rod cladding and the thickness of the oxide layer generated by the oxidation corrosion of the cladding; determining the temperature field distribution information of the cladding, the pellets and the gap between the cladding and the pellets of the fuel rod based on the volume heat release rate, the deposition thickness and the thickness of the oxide layer; performing deformation iteration calculation on the cladding and the pellets based on the temperature field distribution information of the cladding, the pellets and the gap until the temperature and size of the gap reach convergence to obtain the size of the gap; and performing fission gas behavior analysis based on the temperature field distribution information of the cladding, the pellets and the gap and the size of the gap to obtain the gas pressure in the gap between the cladding and the pellets. The application has important reference value for predicting the integrity of the fuel rod.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear reactors, in particular to a method and device for predicting the corrosion fouling deposit layer of fuel rod cladding. BACKGROUND

[0002] Chalk River Unidentified Deposit (CRUD) is a corrosion product generated by the core and steam generator, which is deposited on the surface of the fuel rod. At the end of the fuel cycle, the average thickness of CRUD can reach 60-70 or even thicker. The deposition of CRUD has a complex impact on fuel performance and reactor safety, including CRUD-induced power shift (CIPS), deteriorated heat transfer, CRUD-induced local corrosion (CILC), etc. Under operating conditions, fuel failure is mainly caused by pellet-cladding chemical interaction (PCCI), pellet-cladding mechanical interaction (PCMI), cladding creep and CRUD growth. Evaluating the impact of CRUD on fuel failure risk is crucial for fuel design and predicting fuel performance. However, existing CRUD deposition prediction techniques usually only consider the additional thermal resistance caused by the presence of CRUD by considering CRUD thickness or CRUD deposition rate, and cannot fully consider the comprehensive impact of CRUD deposition on fuel rod temperature and mechanics. They lack the ability to fully simulate the complex CRUD deposition process or accurately capture the comprehensive impact on fuel performance. SUMMARY

[0003] Therefore, the present application aims to provide a method and device for predicting the corrosion fouling deposit layer of fuel rod cladding, which can fully reflect the comprehensive impact of the growth of the corrosion fouling deposit layer of fuel rod cladding on fuel performance, and has important reference value for predicting the integrity of fuel rods and preventing the leakage of radioactive substances to improve the safety of the reactor.

[0004] To achieve the above-mentioned purpose, the technical solutions adopted by the embodiments of the present application are as follows:

[0005] In a first aspect, embodiments of the present invention provide a method for predicting corrosion fouling deposits on fuel rod cladding, comprising: step S102, performing neutron physics field analysis on the fuel rod pellet to obtain the volumetric heat release rate of the pellet; step S104, calculating the deposition thickness of the corrosion fouling deposit layer on the fuel rod cladding and the thickness of the oxide layer generated by the oxidation corrosion of the cladding based on the current cladding surface temperature; step S106, determining the temperature field distribution information of the fuel rod cladding, pellet, and the gap between the cladding and pellet based on the volumetric heat release rate, the deposition thickness, and the oxide layer thickness; wherein, the temperature field distribution... The information includes the surface temperature of the cladding, the surface temperature of the core, and the temperature distribution of the gap; Step S108: Based on the temperature field distribution information of the cladding, the core, and the gap, perform deformation iterative calculations on the cladding and the core until the temperature and size of the gap converge, and obtain the size of the gap; Step S110: Based on the temperature field distribution information of the cladding, the core, and the gap, and the size of the gap, perform fission gas behavior analysis to obtain the gap gas pressure between the cladding and the core; Repeat steps S104 to S110 until the gap gas pressure converges.

[0006] Furthermore, the present invention provides a first possible implementation of the first aspect, wherein the step of performing neutron physics field analysis calculation on the fuel rod pellet to obtain the volumetric heat release rate of the pellet includes: calculating the neutron flux distribution of the pellet based on the shape of the pellet to obtain the neutron flux density of the pellet; and calculating the volumetric heat release rate distribution of the pellet based on the neutron flux density.

[0007] Furthermore, the present invention provides a second possible implementation of the first aspect, wherein the step of calculating the deposition thickness of the corrosion fouling deposit layer on the fuel rod cladding and the thickness of the oxide layer generated by the cladding oxidation corrosion includes: simulating the concentration mass transfer process of the corrosion fouling deposit layer on the fuel rod cladding based on the primary loop water chemical corrosion theory to obtain the deposition thickness of the deposit layer on the surface of the fuel rod in the core; and simulating the oxidation corrosion process of the cladding based on a preset semi-empirical model to obtain the thickness of the oxide layer generated by the cladding.

[0008] Furthermore, the present invention provides a third possible implementation of the first aspect, wherein the step of determining the temperature field distribution information of the fuel rod cladding, pellet, and the gap between the cladding and the pellet based on the volumetric heat release rate, the deposition thickness, and the oxide layer thickness includes: solving the energy balance equation of the pellet based on the volumetric heat release rate of the pellet and the finite volume method to determine the temperature field distribution information of the pellet; establishing a temperature heat transfer model of the cladding and pellet regions based on the deposition thickness, the oxide layer thickness, and Fourier's law, and calculating the temperature field distribution information of the cladding and the temperature field distribution information of the gap between the cladding and the pellet.

[0009] Furthermore, this embodiment of the invention provides a fourth possible implementation of the first aspect, wherein the step of performing deformation iterative calculations on the shell and the core block based on the temperature field distribution information of the shell, the core block, and the gap includes: performing characteristic deformation calculations on the core block and the shell; performing elastoplastic mechanical analysis on the shell and the core block based on the temperature field distribution information of the shell, the core block, and the gap and the characteristic deformation calculation results, until the temperature and size of the gap converge, and calculating the size of the gap and the interaction force between the shell and the core block.

[0010] Furthermore, this embodiment of the invention provides a fifth possible implementation of the first aspect, wherein the step of calculating the characteristic deformation of the core and the cladding includes: calculating the characteristic deformation of the core based on the temperature field distribution information of the core to obtain the strain parameters of the core; wherein the characteristic deformation of the core includes irradiation swelling, thermal expansion, and densification phenomena; calculating the characteristic deformation of the cladding based on the temperature field distribution information of the cladding to obtain the strain rate parameters of the cladding; wherein the characteristic deformation calculation of the cladding includes creep and thermal expansion phenomena of the cladding.

[0011] Furthermore, the present invention provides a sixth possible implementation of the first aspect, wherein the step of performing fission gas behavior analysis based on the temperature field distribution information of the cladding, the core, and the gap, and the size of the gap, to obtain the gap gas pressure between the cladding and the core, includes: constructing an ideal gas equation for the generation and release process of the fission gas based on the temperature field distribution information of the cladding, the core, and the gap, and calculating the gap gas pressure between the cladding and the core.

[0012] Secondly, embodiments of the present invention also provide a device for predicting corrosion fouling deposits on fuel rod cladding, comprising: a first calculation module for performing neutron physics field analysis calculations on the fuel rod pellet to obtain the volumetric heat release rate of the pellet; a second calculation module for calculating, based on the current cladding surface temperature, the deposition thickness of the corrosion fouling deposit on the fuel rod cladding and the thickness of the oxide layer generated by the oxidative corrosion of the cladding; and a third calculation module for determining, based on the volumetric heat release rate, the deposition thickness, and the oxide layer thickness, the cladding of the fuel rod, the pellet, and the gap between the cladding and the pellet. Temperature field distribution information; wherein, the temperature field distribution information includes the surface temperature of the cladding, the surface temperature of the core, and the temperature distribution of the gap; a fourth calculation module is used to perform deformation iterative calculations on the cladding and the core based on the temperature field distribution information of the cladding, the core, and the gap until the temperature and size of the gap converge to obtain the size of the gap; a fifth calculation module is used to perform fission gas behavior analysis based on the temperature field distribution information of the cladding, the core, and the gap and the size of the gap to obtain the gap gas pressure between the cladding and the core.

[0013] Thirdly, embodiments of the present invention provide an electronic device, including: a processor and a storage device; the storage device stores a computer program, which, when executed by the processor, performs the method as described in any of the first aspects.

[0014] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, performs the steps of the method described in any of the first aspects above.

[0015] This invention provides a method and apparatus for predicting corrosion fouling deposits on fuel rod cladding. The method determines the temperature field distribution between the cladding and the pellet based on the pellet's volumetric heat release rate, the deposition thickness of the corrosion fouling deposits, and the oxide layer thickness of the cladding. It also analyzes the deformation of the cladding and pellet based on this temperature field distribution, comprehensively analyzing the multi-physical effects of fuel rod cladding corrosion fouling deposit growth on fuel. By calculating the gap size and interstitial gas pressure between the cladding and the pellet, the method can fully reflect the comprehensive impact of fuel rod cladding corrosion fouling deposit growth on fuel performance. This provides important reference value for predicting fuel rod integrity and preventing radioactive material leakage, thus improving reactor safety.

[0016] Other features and advantages of the embodiments of the present invention will be set forth in the following description, or some features and advantages may be inferred from the description or determined without doubt, or may be learned by practicing the techniques described above in the embodiments of the present invention.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 A flowchart of a method for predicting corrosion fouling deposits on fuel rod cladding provided by an embodiment of the present invention is shown.

[0020] Figure 2 A schematic diagram of a discrete scheme used in calculating the temperature distribution of a core block provided by an embodiment of the present invention is shown.

[0021] Figure 3 This invention provides a schematic diagram of the mesh for the axial segment of a fuel rod in a mechanical calculation.

[0022] Figure 4 A logic diagram of a calculation method for corrosion fouling deposits on fuel rod cladding provided in an embodiment of the present invention is shown.

[0023] Figure 5 A schematic diagram of a device for predicting corrosion fouling deposits on fuel rod cladding provided in an embodiment of the present invention is shown. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0025] Fuel rods in nuclear reactors encounter extreme conditions of high temperature, radiation, and chemical corrosion over 3-4 fuel cycles. The fuel cladding is the primary barrier preventing the release of radioactive fission products, and fuel performance is a key factor in evaluating the safety and economic feasibility of a nuclear reactor. Under operating conditions, fuel failure is mainly caused by pellet-cladding chemical interactions (PCCI), pellet-cladding mechanical interactions (PCMI), cladding creep, and CRUD (creep deposit) growth. According to statistics on fuel failure causes in US light water reactors, CRUD deposition accounted for 39.7% of fuel rod damage in the 1990s.

[0026] CRUD (Crew Root Unstable Deposition) is a corrosion product generated in the core and steam generator, deposited on the surface of fuel rods. At the end of the fuel cycle, the average thickness of CRUD can reach 60–70 mm or even more. CRUD deposition has complex effects on fuel performance and reactor safety, including CRUD-induced power offset (CIPS), deteriorated heat transfer, and CRUD-induced localized corrosion (CILC). CIPS, also known as axial offset anomaly (AOA), is caused by the non-uniform distribution of boron concentration due to CRUD deposition. CIPS increases localized thermal stress in the fuel rods, significantly affecting safety margins and fuel integrity. CRUD deposition increases cladding surface temperature, not only imposing additional thermal stress on the cladding but also altering the heat transfer mechanism between the cladding and coolant, leading to incorrect predictions of the critical heat flux (CHF). Given their practical importance, CIPS and CILC have become topics of extensive research from multiple perspectives, including water chemistry, reactor physics, computational fluid dynamics (CFD), and boron dynamics.

[0027] Assessing the impact of CRUD on fuel failure risk is crucial for fuel design and performance prediction. However, directly measuring the impact of CRUD under nuclear reactor operating conditions remains challenging. Currently, there are few studies using multiphysics coupling methods to investigate the impact of CRUD deposition on fuel performance. Existing fuel performance analysis techniques either do not consider the impact of CRUD or can only account for its presence by considering a predetermined CRUD thickness, lacking the ability to fully simulate the complex CRUD deposition process or accurately capture its comprehensive impact on fuel performance.

[0028] Current simulation techniques for corrosion product deposition mainly focus on the transport and metering distribution of corrosion products, with limited quantitative assessment of the impact of oxidative corrosion product growth on fuel performance, such as heat transfer and mechanical degradation of the cladding. Therefore, there is an urgent need for a predictive technique applicable to the impact of CRUD deposition on fuel performance, revealing the laws governing the influence of oxidative corrosion products on core safety.

[0029] To address the aforementioned problems, this invention provides a method and apparatus for predicting corrosion fouling deposits on fuel rod cladding. The following provides a detailed description of this invention.

[0030] This embodiment provides a method for predicting corrosion fouling deposits on fuel rod cladding. This method can be applied to electronic devices such as computers. See [link to documentation]. Figure 1 The flowchart shown illustrates a method for predicting corrosion fouling deposits on fuel rod cladding. This method includes the following steps:

[0031] Step S102: Perform neutron physics field analysis and calculation on the fuel rod pellets to obtain the volumetric heat release rate of the pellets;

[0032] Fuel pellets are typically cylindrical or toroidal, and their circumferential neutron flux distribution can be approximated as uniform. The axial neutron flux distribution is controlled by the axial power factor, using the cos(z) distribution by default. The radial neutron flux distribution is obtained by solving the one-dimensional diffusion theory of a single group. The neutron flux density of the pellet is calculated based on the radial neutron flux distribution. The volumetric heat release rate distribution of the pellet is calculated based on burnup and neutron flux density to obtain the normalized radial volumetric heat release rate distribution.

[0033] Step S104: Based on the current cladding surface temperature, calculate the deposition thickness of the corrosion fouling deposit layer on the fuel rod cladding and the thickness of the oxide layer generated by the cladding oxidation corrosion.

[0034] Based on the solubility of corrosive fouling as temperature changes, the process of fouling in the reactor core precipitating, crystallizing, and settling from the coolant under the drive of supercooled boiling is calculated, and the CRUD deposition thickness is determined.

[0035] The CRUD deposition process can be modeled using a three-node model, in which the nuclear reactor is divided into three regions: the core, the coolant, and the steam generator (S / G). Under steady-state conditions, assuming that the mass transfer rate is equal to the deposition rate and the release rate, and that thermal diffusion and erosion effects are neglected due to their small impact on the CRUD transport process, the deposition rate and CRUD layer thickness in the core can be solved by the concentration balance of CRUD.

[0036] Oxidation and corrosion of the cladding will produce an oxide layer. The formation of the oxide layer will cause the heat transfer on the cladding surface to deteriorate and affect the growth mechanism of the CRUD layer. In order to accurately estimate the oxidation and corrosion rate and obtain the correct oxide layer thickness, the EPRI / KWU / CE model is used to calculate the cladding oxide layer thickness.

[0037] Step S106: Determine the temperature field distribution information of the fuel rod cladding, pellets, and the gap between the cladding and pellets based on the volumetric heat release rate, deposition thickness, and oxide layer thickness; wherein, the temperature field distribution information includes the surface temperature of the cladding, the surface temperature of the pellets, and the temperature distribution of the gap.

[0038] Based on the principles of heat transfer, the temperature field distribution of the fuel rod under the influence of CRUD is obtained by solving Newton's cooling formula, Fourier's law of heat conduction, and the effective volume method for the steady-state heat conduction differential equation.

[0039] The temperature field is calculated segmented along the axial direction, and the temperature field of primary concern can be divided into three regions: the cladding, the interstitial space, and the core. For the cladding and core regions, the temperature distribution is calculated sequentially based on Fourier's law, Newton's law of cooling, and related equations for the CRUD layer, oxide layer, cladding, and interstitial space. For the core, assuming that the neutron flux is only a function of the axial height and radial position, the temperature distribution of the core can be modeled using a one-dimensional energy conservation equation and solved using the finite volume method (FVM).

[0040] Step S108: Based on the temperature field distribution information of the cladding, core, and gap, perform deformation iterative calculations on the cladding and core until the temperature and size of the gap converge, and obtain the size of the gap.

[0041] Based on the solved temperature field, an elastoplastic mechanical analysis was performed on the core and cladding. The thermo-elastoplastic constitutive equations were solved using finite element techniques and regression mapping methods. The deformation of the cladding and core was calculated and the influence of CRUD was analyzed. At the same time, it was determined whether PCMI occurred and the contact stress was solved using an accelerated iteration method.

[0042] The mechanical calculations are divided into three parts: characteristic deformation calculation, constitutive equation solution, and contact stress iteration. Behaviors that are difficult to characterize by constitutive equations, such as core densification and repositioning, and cladding creep and irradiation elongation, are calculated using empirical relationships to obtain the corresponding deformations. The obtained characteristic deformations are substituted into the elastoplastic constitutive equations as additional plastic deformations for calculation. The solution is obtained using the finite element method, back mapping, and Newton-Raphson iteration methods. Finally, the cladding gap closure is checked, and the mechanical contact condition of the core and cladding is obtained through trial stress and contact stress iteration.

[0043] Step S110: Based on the temperature field distribution information of the cladding, core, and gap, and the size of the gap, the fission gas behavior is analyzed to obtain the gap gas pressure between the cladding and the core.

[0044] Using a physics-based multiscale fission gas behavior model, the diffusion, nucleation, migration, and release behavior of fission gas were simulated, and the fission gas release amount of the core and the interstitial gas pressure between the cladding and the core were obtained at the corresponding CRUD deposition thickness.

[0045] Repeat steps S104 to S110 until the interstitial gas pressure converges.

[0046] The method for predicting corrosion and fouling deposits on fuel rod cladding provided in this embodiment determines the temperature field distribution between the cladding and the pellet based on the volumetric heat release rate of the pellet, the deposition thickness of the corrosion and fouling deposits on the fuel rod cladding, and the oxide layer thickness of the cladding. It also analyzes the deformation of the cladding and pellet based on this temperature field distribution, comprehensively analyzing the multi-physical effects of the growth of the corrosion and fouling deposits on the fuel. By calculating the gap size and interstitial gas pressure between the cladding and the pellet, it can comprehensively reflect the comprehensive impact of the growth of the corrosion and fouling deposits on fuel performance. This method has important reference value for predicting fuel rod integrity and preventing radioactive material leakage, thus improving reactor safety.

[0047] In one embodiment, this embodiment provides a specific implementation method for performing neutron physics field analysis and calculation on fuel rod pellets to obtain the volumetric heat release rate of the pellets:

[0048] The neutron flux distribution of the pellet is calculated based on its shape to obtain the neutron flux density of the pellet; the burnup depth of the pellet is calculated, and the volumetric heat release rate distribution of the pellet is calculated based on the neutron flux density.

[0049] The shape of the core includes solid cylindrical cores and toroidal cores. The neutron flux distribution in the circumferential direction of the core can be approximated as the same. The axial neutron flux distribution is controlled by the axial power factor, and the default is to use the cos(z) distribution. The radial neutron flux distribution is obtained by solving the one-dimensional diffusion theory of a single group.

[0050] For a solid cylindrical core, the formula for calculating its neutron flux density is:

[0051] φ(r)=CI0(κr) Formula 1 For a toroidal core, the formula for calculating the neutron flux density is:

[0052]

[0053]

[0054]

[0055]

[0056] Where φ(r) is the neutron flux density, I0 is the modified Bessel function of the first kind, K0 is the modified Bessel function of the second kind, C is a constant, κ is the reciprocal of the neutron diffusion length, D is the neutron diffusion coefficient, r is the radial coordinate, R0 is the outer radius of the core, and ∑ a For the total macroscopic absorption cross section, σ a For the microscopic absorption cross section, σ s For the microscopic scattering cross section, ∑ sThis represents the total macroscopic scattering cross section. This represents the average concentration of particles in the core.

[0057] Solve the burnup equation to calculate the burnup depth of the pellet, considering the pellet material as follows: 235 U、 238 U、 239 Pu、 240 Pu、 241 Pu and 242 The fuel consumption equation for Pu is:

[0058]

[0059]

[0060]

[0061] Where, the subscript j is 239 Pu、 240 Pu、 241 Pu and 242 Pu is an isotope of plutonium. for 235 The number of U nuclides, for 238 The number of U nuclides, σ a,235 for 235 The absorption cross section of U, σ a,238 for 235 The absorption cross section of U, σ c,j-1 Let σ be the total cross section of a nuclide with mass number j-1. a,j Let be the absorption cross section of a nuclide with mass number j.

[0062] By substituting time into a variable and using fuel consumption to represent the change in time, the volumetric heat release rate can be calculated.

[0063]

[0064] Thus, Formula 5 can be written as follows:

[0065]

[0066]

[0067]

[0068]

[0069] Where q″′ is the volumetric heat release rate, dbu is the fuel consumption increment, and ρ fuel Let F(r) be the fuel density, F(r) be the radial distribution function of plutonium, and σ be the radial distribution function of plutonium. fLet A be the microscopic fission cross section, and σ be a constant coefficient. a,239 for 239 The absorption cross section of Pu, σ f,k Let N be the fission cross section of a nuclide with mass number k, α be a constant coefficient, and N be the cross section of a nuclide with mass number k. 239 (r) is 239 The number of nuclides at r in Pu, N j (r) represents the number of nuclides with mass number j at position r, σ c,j-1 For the total cross section of a nuclide with mass number j-1, N j-1 Let r be the number of nuclides with mass number j-1 at position r.

[0070] At the end of each time step, the fuel consumption is updated according to the above increments.

[0071]

[0072]

[0073] The constraint condition for f(r) is that the volume mean is 1, and r out Let p1 be the outer radius of the fuel, p2 be a constant coefficient, p3 be a constant coefficient, and r be the radial coordinate.

[0074] σ a =σ f +σ c Formula 11

[0075] The volumetric heat release rate distribution of the pellet is obtained based on the calculation results of burnup and neutron flux. The normalized radial volumetric heat release rate distribution can be obtained using the following formula:

[0076] q″′(r)=α∑ j σ f,j N j φ Formula 12

[0077] Where the subscript j represents 239 Pu、 240 Pu、 241 Pu and 242 Pu is an isotope of plutonium. For the axial distribution of volumetric heat release rate, simply multiply by the corresponding axial power factor (default is cos(z) distribution).

[0078] In one embodiment, this embodiment provides a specific implementation method for calculating the deposition thickness of the corrosion fouling deposit layer on the fuel rod cladding and the thickness of the oxide layer generated by cladding oxidation corrosion:

[0079] The concentration mass transfer process of the corrosion fouling deposit layer on the fuel rod cladding was simulated and calculated based on the primary loop water chemical corrosion theory to obtain the deposition thickness of the deposit layer on the surface of the fuel rods in the core. The oxidation corrosion process of the cladding was simulated and calculated based on a preset semi-empirical model to obtain the thickness of the oxide layer produced by the cladding.

[0080] The deposition process of CRUD can be modeled using a three-node model, in which the nuclear reactor is divided into three regions: the core, the coolant, and the steam generator (S / G). Under steady-state conditions, it is assumed that the mass transfer rate is equal to the deposition rate and the release rate. Thermal diffusion and erosion effects are neglected because they have little impact on the CRUD transport process.

[0081] CRUD is primarily composed of nickel and iron oxides or nickel-cobalt-iron oxides, with the stoichiometric coefficient of nickel or the sum of nickel and cobalt ranging from 0.45 to 0.75. The solubility of CRUD at different temperatures is calculated using the chemical dissociation reaction of CRUD and the saturation concentration of iron ions. The solubility of iron is derived from the Lindsay equation and corrected by fitting measured values ​​of nickel-iron oxide solubility, as shown below:

[0082]

[0083] Reaction constant K i It is a function of the Gibbs free energy change, which is related to temperature. Through the correspondence, we can obtain the following formula:

[0084]

[0085]

[0086]

[0087]

[0088] Where S is the solubility, and K0, K1, K2, and K3 are constant coefficients. For hydrogen ion concentration, A c Here, A0, A1, A2, B0, B1, and B2 are the stoichiometric coefficients of the solid oxides, and T is the temperature in Kelvin. w γ is the ion product of water, z is the hydrogen ion concentration, γ0 is the activity coefficient of neutral particles, and γ1 is the activity coefficient of monovalent particles.

[0089] The precise mass transfer coefficient can only be obtained through the correlation of experimental data. Due to the uncertainty of the boundary layer eddy diffusion coefficient, it is difficult to derive the analytical equation for the mass transfer factor. The mass transfer coefficient was calculated using an analogy to heat transfer. In heat transfer, the Prandtl number is the ratio of momentum diffusion coefficient to thermal diffusion coefficient, and the Schmidt number is the ratio of momentum diffusion coefficient to mass diffusion coefficient in mass transfer. In the simulation equations, the Schmidt number is used instead of the Prandtl number, and the Nusselt number is used instead of the Sherwood number. Based on the Dittus-Boelter correlation coefficient and the Berger-Hau correction method, the mass transfer coefficient is expressed as follows:

[0090]

[0091] The mass transfer factor is proportional to the surface area of ​​the relevant nodes, and can be written as,

[0092]

[0093] By using the concentration balance of CRUD, the deposition rate and CRUD layer thickness in the core can be determined. The CRUD transport balance equation in the core can be expressed as follows:

[0094]

[0095] Where h is the mass transfer coefficient, and D ab Let D be the diffusion coefficient of CRUD. e Where ρ is the hydraulic diameter of the flow channel, ρ is the density of the coolant, V is the flow velocity of the coolant, m is the mass flow rate of the coolant, μ is the viscosity of the coolant, and k is the viscosity of the coolant. i Mass transfer factor For surface area, I core For core CRUD stock, k S / G k is the mass transfer factor for soluble CRUD in S / G. core The mass transfer factor for soluble CRUD in the reactor core. The mass transfer coefficient of particle CRUD in S / G, S is the mass transfer coefficient of the CRUD of particles in the reactor core. S / G S represents the saturation concentration of CRUD in S / G. core S represents the saturation concentration of CRUD in the reactor core. coolant This represents the saturation concentration of CRUD during cooling.

[0096] Based on the calculated core CRUD stock I core The CRUD layer thickness, i.e., the deposition thickness of the corrosion fouling deposit layer on the fuel rod cladding, can be calculated. This thickness = I core * Total coolant volume / Deposit density / Total surface area of ​​fuel rods.

[0097] Oxidation corrosion of the cladding produces an oxide layer, which deteriorates heat transfer on the cladding surface and affects the growth mechanism of the CRUD layer. To accurately estimate the oxidation corrosion rate and obtain the correct oxide layer thickness, the EPRI / KWU / CE model is used to calculate the oxide layer thickness produced by the cladding. EPRI / KWU / CE is a two-stage semi-empirical model where the oxide growth rate equation differs before and after reaching the transition oxide thickness. The thickness of the transition oxide is calculated using the following formula:

[0098]

[0099] Among them, S trans For oxide transition thickness, T om The temperature at which the oxide layer meets the cladding is denoted as , where D3 and E3 are constants, Q3 is a constant coefficient, and R is the ideal gas constant.

[0100] Before reaching the transition thickness, the oxidation corrosion rate follows a cubic root relationship, gradually slowing down as oxidation corrosion progresses, which can be expressed as:

[0101]

[0102] Once the transition thickness is reached, the oxidation corrosion kinetics become linear, and the oxidation corrosion rate increases significantly. The formula for calculating the thickness of the oxide layer produced by the cladding is:

[0103]

[0104] Where S is the oxide layer thickness, S0 is the initial oxide layer thickness, Δt is the time step, and k1, k2, Q1 and Q2 are constants.

[0105] In one embodiment, this embodiment provides a specific implementation method for determining the temperature field distribution information of the fuel rod cladding, pellets, and the gap between the cladding and pellets based on volumetric heat release rate, deposition thickness, and oxide layer thickness:

[0106] The temperature field distribution information of the chip is determined by solving the energy balance equation of the chip based on the volumetric heat release rate and the finite volume method.

[0107] A temperature and heat transfer model for the cladding and core regions was established based on the deposition thickness, oxide layer thickness, and Fourier's law. The temperature field distribution information of the cladding and the temperature field distribution information of the gap between the cladding and the core were calculated.

[0108] The temperature field is calculated in segments along the axial direction, and the main temperature field calculated can be divided into three regions: the cladding, the gap, and the core. For the cladding and core regions, the temperature distribution model is based on Fourier's law, Newton's law of cooling, and related equations, calculating the temperature distribution of the CRUD layer, oxide layer, cladding, and gap sequentially. For the core, assuming that the neutron flux is only a function of the axial height and radial position, the temperature distribution of the core can be modeled using a one-dimensional energy conservation equation and solved using the finite volume method (FVM).

[0109] The temperature drop of the CRUD layer and oxide layer is calculated using Fourier's law. The deposition thickness (i.e., CRUD thickness) and oxide layer thickness, calculated using formulas 20-23 above, are then used to calculate the temperature drop of the CRUD layer and oxide layer.

[0110]

[0111]

[0112] Where, ΔT cr For the temperature drop of the CRUD layer, ΔT ox For the temperature drop of the oxide layer, δ cr (z) represents the CRUD layer thickness (based on the aforementioned core CRUD inventory I). core The CRUD layer thickness can be calculated, q″(z) is the heat flux density on the core surface, and k cr δ is the equivalent thermal resistance of the CRUD layer. ox (z) represents the oxide layer thickness (i.e., S in Formula 23 above), k ox is the thermal conductivity of the oxide layer.

[0113] Calculate the cladding surface temperature. Heat transfer between the fuel cladding surface and the coolant occurs in two modes: forced convection and nucleation boiling. After the coolant flows into the fuel assembly, its temperature rises as heat is continuously transferred from the fuel to the coolant. When the coolant temperature exceeds the saturation temperature, the heat transfer mode changes from forced convection to nucleation boiling. Heat transfer models are established for both modes to calculate the cladding surface temperature. The minimum value calculated by the two heat transfer models is used to determine whether the heat transfer model is forced convection or nucleation boiling. Based on the assumption that coolant boiling occurs within the CRUD layer, the Jens-Lottes correlation is used for calculation when nucleation boiling occurs. The corresponding cladding surface temperature calculation formula is shown below:

[0114] T co (z)=T b (z)+ΔT f (z)+ΔT cr (z)+ΔT ox(z) Formula 26

[0115] T co (z)=T sat +ΔT JL +ΔT ox (Z) Formula 27

[0116]

[0117] Among them, z co (z) represents the surface temperature of the cladding, T b (z) represents the coolant volume temperature, ΔT f (z) represents the temperature difference of the forced convection heat transfer film, T sat ΔT is the coolant saturation temperature. JL P represents the nucleus boiling temperature drop at the cladding surface, and P represents the coolant pressure.

[0118] Calculating the gap temperature difference reveals that heat conduction in the core-cladding gap is complex, and can be divided into three parts: thermal irradiation, convective heat transfer of the gap gas, and direct heat conduction after PCMI occurs.

[0119]

[0120] Where, ΔT gap (z) represents the temperature drop between the core and the cladding, and r represents the irradiation heat transfer coefficient. gas The gas convection heat transfer coefficient is... solid The equivalent PCMI thermal conductivity is given.

[0121] For the radiative heat transfer coefficient, a simplified gray-body form of the irradiation heat transfer equation was adopted:

[0122]

[0123] Based on the equivalent thermal resistance coefficient, the convective heat transfer coefficient of the gas within the gap was obtained:

[0124]

[0125] Where σ is the Stephen Boltzmann constant, F is the geometric factor, and T fs T represents the outer surface temperature of the core. ci K represents the temperature of the inner surface of the casing. gas Δx is the thermal conductivity of the gas filling the gap, and Δx is the gap size.

[0126] The equivalent thermal conductivity introduced by PCMI generation was calculated using the improved Mikic-Todreas model.

[0127]

[0128] Among them, Km P is the geometric mean thermal conductivity. rel Where is the contact stress, and E is the roughness coefficient.

[0129] Calculate the temperature distribution within the fuel pellet. Finite interpolation will be used to calculate the temperature distribution within the fuel region. Variable mesh spacing will be used, and the spatial dependence of internal heat sources allows for variation at each mesh interval. Boundary layer meshes are considered during the discretization process; see [reference needed]. Figure 2 The diagram shows the discrete scheme used in the calculation of the core temperature distribution. A schematic diagram of the discrete structure is shown below. Figure 2 As shown, a one-dimensional steady-state heat conduction differential equation with active terms and variable coefficients is first established for the core:

[0130]

[0131] in, It serves as the internal heat source generated by fission. It satisfies the volumetric heat release rate q”'(r,z) distribution. ρ is the thermal conductivity of the fuel rod pellet, and s is the control volume surface area. It is the unit vector of the surface normal vector. V represents the temperature of the fuel rod pellets, and V represents the volume of the control volume.

[0132] Introducing boundary conditions: (1) fuel rod surface temperature; (2) the fuel rod axis and symmetrical parts are adiabatic. Then, formula 33 is discretized, and the discretization format is as follows. First, the coefficients are defined as follows:

[0133]

[0134]

[0135]

[0136] Where δ is the length of the control volume, x m To control the center coordinates of the control volume, subscript l represents the left element, subscript r represents the right element, and subscript m indicates that the current element is the m-th element. The index direction is from the first cell node being the core's central axis to the last cell node being the outermost wall. Superscript s represents area, superscript v represents volume, and superscript b represents the boundary.

[0137] Then, a difference approximation is performed on the internal nodes. For the left side of Equation 33:

[0138]

[0139] For the source term:

[0140]

[0141] Where k is the thermal conductivity of the node, P f Let P be the axial power factor, P be the power function distribution, and Q(x) be the radial position correlation coefficient. For the right side of Equation 33:

[0142]

[0143] The difference equation for the m-th node can be expressed as:

[0144]

[0145] The simplified representation is as follows:

[0146] a m T m-1 +b m T m +c m T m+1 =d m

[0147]

[0148]

[0149] Where a, b, c, and d are constant coefficients, and the thermal conductivity of the core is calculated using a modified NFI model. This model considers the effects of temperature, fuel consumption, porosity, and irradiation.

[0150]

[0151] Among them, K 95 denoted as 95% standard density fuel thermal conductivity, BU as burnup, f(BU) as the coefficient characterizing the fission product effect, g(BU) as the coefficient representing the influence of irradiation defects, (T) as the temperature dependence coefficient during irradiation defect annealing, gad as the weight fraction of gadolinium, and A, a, B, E, and F as thermophysical constants.

[0152] In one embodiment, this embodiment provides an implementation method for performing deformation iterative calculations on the cladding and core based on the temperature field distribution information of the cladding, core, and gap. The specific steps are as follows:

[0153] Step (1): Perform characteristic deformation calculations on the core block and cladding;

[0154] In one specific implementation, characteristic deformation calculations are performed on the core block based on the temperature field distribution information of the core block to obtain the strain parameters of the core block; wherein, the characteristic deformation of the core block includes irradiation swelling, thermal expansion and densification phenomena; characteristic deformation calculations are performed on the cladding shell based on the temperature field distribution information of the cladding shell to obtain the strain rate parameters of the cladding shell; wherein, the characteristic deformation calculation of the cladding shell includes the creep and thermal expansion phenomena of the cladding shell.

[0155] The characteristic deformation of the core was calculated, including irradiation swelling, thermal expansion, and densification. The irradiation swelling behavior of the core includes gaseous expansion caused by the diffusion of gaseous fission products and solid particle expansion caused by the accumulation of solid fission products. To determine the effect of gas swelling on the amount of permanent cladding deformation generated in the high-burnup rod, a gas swelling model based on Mogensen data is expressed as follows:

[0156]

[0157] Where, ε gs Let T be the gas expansion strain, a be a constant related to fuel consumption, and T be the gas expansion strain. p This represents the core temperature.

[0158] The expansion of solid pellet particles caused by solid fission products was calculated using the Ruschel and Gilder model.

[0159]

[0160] in, The fraction of volume change caused by fuel expansion due to solid fission products, and BU is the burnup depth.

[0161] The thermal expansion of the chip is characterized using the MATPRO model, modified based on data from Baldock et al., and can be expressed as follows:

[0162] ε t =K1T p -K2+K3exp(-E D / kT p ) Formula 43

[0163] Formula 43 is based on the assumption that the thermal expansion of fuel is isotropic. It can be used for uranium dioxide fuel, UO2-PuO2 mixed fuel, and PuO2 fuel, requiring only a change in the correlation coefficient K. i (K1, K2, K3). Where ε t For thermal strain, T p E represents the core temperature. D The energy required to form a defect, k is the Boltzmann constant.

[0164] The densification of fuel pellets is primarily caused by the migration of uranium and oxygen elements induced by irradiation. Based on observations from in-pile irradiation experiments, the densification rate gradually decreases with increasing burnup, eventually reaching zero within a burnup range of 5–10 GWd / MTU. At this point, the remaining porosity in the fuel pellets is mainly filled with fission gases. Thus, pellet densification can be modeled using a semi-empirical formula, which can be expressed as:

[0165]

[0166] Furthermore, microstructural parameters, including grain size and porosity distribution, also play a crucial role in the densification process of fuel particles. Therefore, a graphical solution method, combined with the sintering temperature formula, is used to improve the aforementioned densification formula, resulting in an improved densification formula. The improvement primarily considers the initial deformation introduced by the inherent properties of the material, termed chimney shortening, denoted as...

[0167]

[0168] in, T represents elongation. SINT ρ is the core sintering temperature, and ρ is the core density.

[0169] Calculate the characteristic deformation of the cladding. The characteristic deformation of the cladding includes creep and thermal expansion. For the creep behavior of the cladding material, based on Norton's creep law, a modified creep limit model is used to calculate the thermal creep and irradiation creep of the cladding:

[0170]

[0171]

[0172] in, For thermal strain rate, φ is the irradiation strain rate, φ is the neutron flux density, R is the gas constant, and σ is the irradiation strain rate. eff Where W is the effective stress, E is the creep energy, T is the temperature, and a is the creep stress. i is the material coefficient, n is a constant coefficient, Q is the activation energy, and C0, C1, and C2 are constant coefficients.

[0173] The thermal expansion of the cladding was calculated using a two-stage empirical formula, employing the correlation proposed by Megan and Wiesinger to describe the thermal expansion behavior of the cladding. For temperatures between 1073 K and room temperature, the following equation was used:

[0174] ε 33 = -2.506 × 10 -5 +4.441×10 -6 T cFormula 48

[0175] ε 11 = -2.373 × 10 -5 +6.721×10 -6 T c For temperatures above 1073 K, Equation 49 calculates the thermal expansion of the cladding using the following equation.

[0176] ε 33 = -8.3 × 10 -3 +9.7×10 -6 T c Formula 50

[0177] ε 11 = -6.8 × 10 -5 +9.7×10 -6 T c Formula 51, where ε 11 ε is the axial component of the thermal strain of the cladding. 33 T represents the radial component of the thermal strain of the cladding. c This refers to the cladding temperature.

[0178] Step (2): Based on the temperature field distribution information and characteristic deformation calculation results of the shell, core and gap, perform elastoplastic mechanical analysis on the shell and core until the temperature and size of the gap converge, and calculate the size of the gap and the interaction force between the shell and the core.

[0179] The elastoplastic constitutive equations are solved using the finite element method to calculate the stress, strain, and displacement of the fuel rod cladding and fuel pellets. To more accurately estimate the mechanical properties of the fuel, the elastoplastic constitutive relations are used, and the strain field is calculated as follows:

[0180]

[0181] Where, ε ij Let σ be the strain tensor. ij Let be the stress tensor, v be Poisson's ratio, E be the elastic modulus, and ∫αdT be the thermal strain. For the plastic strain tensor and the plastic strain increment tensor, For the plastic strain increment, δ ij For the Kronark operator, σ kk This is axial stress.

[0182] The thermal strain ∫αdT on the right side of Equation 52 above is related to the temperature field distribution of the fuel rod. The temperature field of the fuel rod can be obtained by solving the finite volume method, that is, the cladding surface temperature T can be calculated. co (z) Temperature drop ΔT between the core cladding gap gap (z) and core temperature Afterwards, the temperature field of the fuel rod is formed. After interpolation, the thermal expansion value of each node is calculated. Substituting this value into the αdT thermal expansion term on the right side of the constitutive equation formula 52 in the mechanical calculation, the constitutive equation can be solved.

[0183] The stress tensor σ on the right side of the above formula 52 ij Based on fission gas behavior analysis, the fission gas release amount is calculated. The gas pressure between the cladding and core blocks is calculated using the ideal gas equation. Since this pressure is applied to both the inner side of the cladding and the outer side of the core blocks, this pressure value is also included as the stress received by the material in the right-hand side of equation 47, σ. ij middle.

[0184] The Prandtl-Royce flow law is used to characterize the relationship between the partial stress tensor and the plastic strain increment tensor:

[0185]

[0186] The hardening equation and yield function of the cladding are taken from the relevant equations used by MATPRO.

[0187]

[0188] in, For the plastic strain increment tensor, For the plastic strain tensor, S ij Let dε be the deviatoric stress tensor. p For an effective plastic strain increment, σ e Where K is the effective stress, K is the strength coefficient (a function of temperature, fast neutron flux, cold work, and alloy composition), n is the strain hardening exponent (a function of temperature and fast neutron flux), m is the strain rate exponent (a function of temperature only), and σ is the stress. For the strain increment, For total strain.

[0189] In the finite element analysis, an improved Newton-Raphson iterative method was used to solve this elastoplastic problem. To ensure the stability, efficiency, and accuracy of the CIFF, triangular axisymmetric elements were employed in the finite element calculations. In the iterative scheme of the model, the fuel rod was divided into multiple axial segments, and each axial segment was further subdivided in the axial and radial directions during the finite element solution of the mechanical calculations. See [reference needed]. Figure 3 The diagram shown is a schematic representation of the mesh for the axial segment of the fuel rod in the mechanical calculations. Figure 3 An example of mesh generation for a typical pressurized water reactor fuel rod axial section cross-section using mechanical calculations is shown.

[0190] The pellet-cladding contact condition is calculated. To handle pellet-cladding mechanical interaction (PCMI), a gap interaction pressure iteration module was developed. In the model, the interaction pressure of each axial layer in the finite element submesh is initially assumed to be zero. Once the PCMI effect occurs, the gap interaction pressure iteration module is used. In this module, the interaction pressure is updated using the following formula. The updated interaction pressure is then used as the boundary of the finite element analysis to calculate the new deformation field under the updated interaction pressure. This process is repeated until the interaction distance between the fuel and cladding is below a given error, typically chosen as the roughness of the pellet and cladding.

[0191]

[0192] in, For the updated interaction pressure, The interaction pressure is defined before the update, δ is the gap size under the applied force after the update, δ0 is the manufactured gap size, and ΔP and α are constants chosen to accelerate the convergence speed of the iteration process.

[0193] In one embodiment, this embodiment provides a specific implementation method for analyzing fission gas behavior based on the temperature field distribution information of the cladding, core, and gap, as well as the size of the gap, to obtain the gap gas pressure between the cladding and the core:

[0194] Based on the temperature field distribution information of the cladding, core, and gap, an ideal gas equation is constructed to determine the generation and release process of fission gas, and the gas pressure in the gap between the cladding and core is calculated.

[0195] The behavior of fissile gases includes their generation, accumulation, and release. Modeling this behavior is based on a cross-scale model of 0D physics. The fissile gas is divided into intraparticle and interparticle components, and its behavior is modeled based on molecular dynamics rate theory and related equations. For intramolecular fissile gases, their nucleation rate, resolution, and capture rate are derived using molecular dynamics theory. The diffusion of intraparticle fissile gases is calculated using the classic Booth model. Based on Speight's assumptions, the diffusion equation can be expressed as:

[0196]

[0197] The intergranular fission gas behavior model is based on Pastore's theory, in which the evolution of gas concentration is described as follows:

[0198]

[0199] The source term is the first term on the right side of formula 57. This represents the flux of atoms diffusing from fuel particles. D is the diffusion coefficient of a single molecule, α is the solubility, β is the capture rate, y is the rate of fission gas production, F is the fission rate of the fuel rod, and t is time. D is the effective diffusion coefficient, c1 is the concentration of monatomic gas, m is the gas concentration of intracrystalline bubbles, q is the intercrystalline gas concentration, R is the fission gas release rate, r is the radial coordinate, a is a constant coefficient, and R ig υ represents the intergranular gas concentration, and υ is a constant coefficient.

[0200] Based on the temperature field distribution information of the cladding, core, and gaps, an ideal gas equation is constructed to calculate the interstitial gas pressure by analyzing the generation and release process of fission gas.

[0201] PV = nRT (Formula 58)

[0202] Where P is the interstitial gas pressure, V is the volume, n is the amount of substance, R is the ideal gas constant, and T is the temperature.

[0203] The method for predicting CRUD corrosion and fouling deposits on fuel rod cladding provided in this embodiment includes a CRUD growth model based on diffusion kinetics, chemical equilibrium, and deposition models. This model can comprehensively describe the generation, deposition, and growth process of CRUDs, accurately reconstructing their distribution in the reactor core and describing their axial non-uniformity caused by core temperature distribution. Furthermore, through a multi-physics coupled solution method, the impact of CRUDs is comprehensively characterized, including behaviors such as cladding surface heat transfer deterioration, localized cladding corrosion, localized cladding thermal stress, and premature PCMI caused by CRUD deposition. This eliminates the need for empirical correlations to correct for CRUD correlations in the physical fields for each effect, significantly improving the accuracy of impact analysis and fuel performance calculations, and enabling better analysis and evaluation of fuel performance impacts under different CRUD deposition levels.

[0204] Based on the foregoing embodiments, this embodiment provides an example of applying the aforementioned method for predicting corrosion fouling deposits on fuel rod cladding, see, for example... Figure 4 The diagram shown illustrates the logic method for calculating corrosion and fouling deposits on the fuel rod cladding. The specific steps are as follows:

[0205] Step 1: Read the input file, initialize all variables, and discretize the core structure into grids and subgrids.

[0206] Step 2: At the current time step and axial node, perform neutron physics calculations on the fuel rod to solve for the fuel rod burn-out depth, nuclide content change, and volumetric heat release rate.

[0207] Step 3: Based on the solubility of corrosive fouling as temperature changes, calculate the process of fouling in the core precipitating, crystallizing, and settling from the coolant under the drive of supercooled boiling, solve for the CRUD deposition thickness, and calculate the oxide layer thickness generated by cladding oxidation corrosion.

[0208] Step 4: Based on the principles of heat transfer, the temperature field distribution of the fuel rod under the influence of CRUD is obtained by solving Newton's cooling formula, Fourier's law of heat conduction, and the effective volume method of the steady-state heat conduction differential equation.

[0209] Step 5: Based on the solved temperature field, perform elastoplastic mechanical analysis on the core and cladding. Use finite element method and regression mapping method to solve the thermo-elastoplastic constitutive equation, calculate the deformation of the cladding and core, and analyze the influence of CRUD. At the same time, determine whether PCMI occurs and use accelerated iteration method to solve for contact stress and core-cladding gap size.

[0210] Step 6: Correct the temperature field, return to step 4, calculate the thermal resistance of the core cladding gap and the gap temperature drop, until the gap temperature and gap size converge.

[0211] Step 7: Using a physics-based cross-scale fission gas behavior model, simulate the diffusion, nucleation, migration and release behavior of fission gas to obtain the fission gas release and core cladding interstitial gas pressure of the core at the corresponding CRUD deposition thickness. Return to step 4 above to update the temperature field distribution until the gas pressure converges.

[0212] The method described in this embodiment, based on a 1.5D model framework, can simulate CRUD deposition and the resulting changes in cladding temperature, cladding corrosion, and fuel deformation across different axial cross sections of the fuel. This analytical method comprises six modules: physical field, temperature field, mechanical field, cladding corrosion, CRUD deposition, and fission gas release. The coupling of these modules is achieved through a four-layer iterative loop, and the accuracy of the calculation results is ensured through convergence of iterative errors for key variables. Specifically, the temperature field and mechanical field are solved using the finite volume method and finite element method, respectively, employing submesh technology, back-mapping algorithms, and Newton-Raphson iterations. For the fission gas release, cladding corrosion, and CRUD deposition modules, molecular dynamics, oxidation kinetics, chemical equilibrium, and crystallography are used. This analytical method can quantitatively assess the impact of CRUD deposition on heat transfer, cladding corrosion, internal interstitial pressure, and fuel deformation. Furthermore, this method can also separate and analyze the increased fuel failure risk caused by CRUD deposition using relevant fuel performance parameters from different physical fields.

[0213] Corresponding to the method for predicting fuel rod cladding corrosion fouling deposits provided in the above embodiments, this invention provides a device for predicting fuel rod cladding corrosion fouling deposits. (See attached image) Figure 5 The diagram shows a structural schematic of a device for predicting corrosion fouling deposits on fuel rod cladding. The device includes the following modules:

[0214] The first calculation module 51 is used to perform neutron physics field analysis and calculation on the fuel rod pellets to obtain the volumetric heat release rate of the pellets.

[0215] The second calculation module 52 is used to calculate the deposition thickness of the corrosion fouling deposit layer on the fuel rod cladding and the thickness of the oxide layer generated by the oxidation corrosion of the cladding, based on the current cladding surface temperature.

[0216] The third calculation module 53 is used to determine the temperature field distribution information of the fuel rod cladding, pellet, and the gap between the cladding and the pellet based on the volumetric heat release rate, the deposition thickness, and the oxide layer thickness; wherein the temperature field distribution information includes the surface temperature of the cladding, the surface temperature of the pellet, and the temperature distribution of the gap;

[0217] The fourth calculation module 54 is used to perform deformation iterative calculations on the shell and the core based on the temperature field distribution information of the shell, the core and the gap, until the temperature and size of the gap converge, and to obtain the size of the gap;

[0218] The fifth calculation module 55 is used to perform fission gas behavior analysis based on the temperature field distribution information of the shell, the core and the gap and the size of the gap, and to obtain the gap gas pressure between the shell and the core.

[0219] The device for predicting corrosion and fouling deposits on fuel rod cladding provided in this embodiment determines the temperature field distribution between the cladding and the pellet based on the volumetric heat release rate of the pellet, the deposition thickness of the corrosion and fouling deposits on the fuel rod cladding, and the oxide layer thickness of the cladding. It also analyzes the deformation of the cladding and pellet based on the temperature field distribution, comprehensively analyzing the multi-physical effects of the growth of the corrosion and fouling deposits on the fuel. By calculating the gap size and interstitial gas pressure between the cladding and the pellet, it can comprehensively reflect the comprehensive impact of the growth of the corrosion and fouling deposits on fuel performance. This device has important reference value for predicting fuel rod integrity and preventing radioactive material leakage, thus improving reactor safety.

[0220] The device provided in this embodiment has the same implementation principle and technical effect as the aforementioned embodiments. For the sake of brevity, any parts not mentioned in the device embodiment can be referred to the corresponding content in the aforementioned method embodiment.

[0221] This invention provides an electronic device, which includes a processor and a memory. The memory stores a computer program that can run on the processor. When the processor executes the computer program, it implements the steps of the method provided in the above embodiments.

[0222] This invention provides a computer-readable medium storing computer-executable instructions. When these computer-executable instructions are invoked and executed by a processor, they cause the processor to implement the methods described in the above embodiments.

[0223] The computer program product of the method and apparatus for predicting corrosion fouling deposits on fuel rod cladding provided in this embodiment of the invention includes a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the preceding method embodiments. For specific implementation details, please refer to the method embodiments, which will not be repeated here.

[0224] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0225] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for predicting the deposition of corrosion fouling layers on fuel rod cladding, characterized by, The method comprises the following steps: In step S102, a neutron physical field analysis calculation is performed on the pellets of the fuel rod to obtain a volumetric heat release rate of the pellets; In step S104, a deposition thickness of a corrosion and deposition layer of the fuel rod cladding and an oxidation layer thickness generated by oxidation corrosion of the cladding are calculated based on a current cladding surface temperature; In step S106, temperature field distribution information of the cladding, the pellets and the gap between the cladding and the pellets is determined based on the volumetric heat release rate, the deposition thickness and the oxidation layer thickness; wherein the temperature field distribution information comprises a surface temperature of the cladding, a surface temperature of the pellets and a temperature distribution of the gap; In step S108, deformation iteration calculation is performed on the cladding and the pellets based on the temperature field distribution information of the cladding, the pellets and the gap, until the temperature and size of the gap reach convergence, to obtain the size of the gap; In step S110, a fission gas behavior analysis is performed based on the temperature field distribution information of the cladding, the pellets and the gap and the size of the gap to obtain a gap gas pressure between the cladding and the pellets; The steps S104 to S110 are repeatedly performed until the gap gas pressure converges.

2. The method of claim 1, wherein, The step of performing the neutron physical field analysis calculation on the pellets of the fuel rod to obtain the volumetric heat release rate of the pellets comprises the following steps: A neutron flux distribution calculation is performed on the pellets based on a shape of the pellets to obtain a neutron flux density of the pellets; A volumetric heat release rate distribution of the pellets is calculated based on the neutron flux density.

3. The method of claim 1, wherein, The step of calculating the deposition thickness of the corrosion and deposition layer of the fuel rod cladding and the oxidation layer thickness generated by oxidation corrosion of the cladding comprises the following steps: A simulation calculation is performed on a concentration mass transfer process of the deposition layer of the fuel rod cladding based on a primary loop water chemical corrosion theory to obtain a deposition thickness of the deposition layer on the surface of the fuel rod in the reactor core; An oxidation corrosion process of the cladding is simulated based on a preset semi-empirical model to obtain an oxidation layer thickness generated by the cladding.

4. The method of claim 1, wherein, The step of determining the temperature field distribution information of the cladding, the pellets and the gap between the cladding and the pellets based on the volumetric heat release rate, the deposition thickness and the oxidation layer thickness comprises the following steps: A temperature field distribution information of the pellets is determined by solving an energy balance equation of the pellets based on the volumetric heat release rate of the pellets and a finite volume method; A temperature heat transfer model of the cladding and the pellets is established based on the deposition thickness, the oxidation layer thickness and Fourier's law to calculate the temperature field distribution information of the cladding and the temperature field distribution information of the gap between the cladding and the pellets.

5. The method of claim 1, wherein, The step of performing deformation iteration calculation on the cladding and the pellets based on the temperature field distribution information of the cladding, the pellets and the gap comprises the following steps: Characteristic deformation calculation is performed on the pellets and the cladding; Performing elastic-plastic mechanics analysis on the cladding and the pellet based on the temperature field distribution information of the cladding, the pellet and the gap and the characteristic deformation calculation result until the temperature and size of the gap converge, and calculating the size of the gap and the interaction force between the cladding and the pellet.

6. The method of claim 5, wherein, The step of performing characteristic deformation calculation on the pellet and the cladding comprises: Performing characteristic deformation calculation on the pellet based on the temperature field distribution information of the pellet to obtain strain parameters of the pellet; wherein the characteristic deformation of the pellet comprises irradiation swelling, thermal expansion and densification phenomena; Performing characteristic deformation calculation on the cladding based on the temperature field distribution information of the cladding to obtain strain rate parameters of the cladding; wherein the characteristic deformation calculation of the cladding comprises creep and thermal expansion phenomena of the cladding.

7. The method of claim 1, wherein, The step of performing fission gas behavior analysis based on the temperature field distribution information of the cladding, the pellet and the gap and the size of the gap to obtain the gap gas pressure between the cladding and the pellet comprises: Constructing an ideal gas equation based on the generation and release process of the fission gas according to the temperature field distribution information of the cladding, the pellet and the gap to calculate the gap gas pressure between the cladding and the pellet.

8. An apparatus for predicting corrosion fouling deposition layer of a fuel rod cladding, characterized by, Comprise: A first calculation module for performing neutron physical field analysis calculation on the pellet of the fuel rod to obtain the volumetric heat release rate of the pellet; A second calculation module for calculating the deposition thickness of the corrosion and deposition layer of the fuel rod cladding and the thickness of the oxidation layer generated by the oxidation corrosion of the cladding based on the current surface temperature of the cladding; A third calculation module for determining the temperature field distribution information of the cladding, the pellet and the gap between the cladding and the pellet of the fuel rod based on the volumetric heat release rate, the deposition thickness and the oxidation layer thickness; wherein the temperature field distribution information comprises the surface temperature of the cladding, the surface temperature of the pellet and the temperature distribution of the gap; A fourth calculation module for performing deformation iteration calculation on the cladding and the pellet based on the temperature field distribution information of the cladding, the pellet and the gap until the temperature and size of the gap reach convergence to obtain the size of the gap; A fifth calculation module for performing fission gas behavior analysis based on the temperature field distribution information of the cladding, the pellet and the gap and the size of the gap to obtain the gap gas pressure between the cladding and the pellet.

9. An electronic device, comprising: Comprise: A processor and a storage device; The storage device stores a computer program, which, when executed by the processor, performs the method of any one of claims 1 to 7.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program, when executed by the processor, performs the steps of the method of any one of claims 1 to 7.

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