Simulation method of corrosion product transport-activation-deposition behavior in pressurized water reactor primary circuit

Abstract

The present application relates to nuclear power technology field, disclose a kind of pressurized water reactor primary loop corrosion product migration-activation-deposition behavior simulation method, comprising: pressurized water reactor primary loop is divided into multiple nodes;Corrosion product is convected between each node Migration term and release term into coolant, the activation term of corrosion product in the core structure is activated by neutron irradiation, and the decay term of activated product occurs decay, deposition term of corrosion product from coolant adheres to node deposition and re-release term from node re-enters coolant;According to migration term, release term, activation term, decay term, deposition term and re-release term, establish the multi-node mass transport model of describing the mass change of corrosion product in each node, to simulate the behavior of corrosion product in each step migration, release, activation, decay, deposition, re-release and deposition and re-release of corrosion product in next step, to iteratively simulate the behavior of corrosion product in pressurized water reactor primary loop.

Description

Technical Field

[0001] This invention relates to the field of nuclear power technology, and in particular to a method, apparatus, equipment and medium for simulating the migration-activation-deposition behavior of corrosion products in the primary loop of a pressurized water reactor. Background Technology

[0002] The main structural materials of the primary loop system in a pressurized water reactor (PWR) nuclear power plant (such as stainless steel and nickel-based alloys) corrode under harsh environments of high temperature, high pressure, and strong radiation, releasing oxidative corrosion products into the coolant. These corrosion products migrate under the influence of the coolant, some depositing on the surface of the fuel elements in the reactor core and becoming activated by neutron irradiation, forming corrosion product deposits. Subsequently, the activated corrosion products may return to the coolant and deposit on the surface of external structural materials. This cyclical process of "corrosion release → coolant migration → core activation → external redeposition" not only creates radioactive areas outside the reactor core, seriously threatening the radiation safety of maintenance personnel, but also leads to abnormal axial power shift, scale-induced power shift, and scale-induced localized corrosion due to the enrichment of boron and lithium in the porous structure of the corrosion product deposits, even causing fuel element damage, significantly increasing the operating costs and safety risks of the nuclear power plant. Therefore, precise research on the migration, activation, and deposition behavior of corrosion products in the primary loop of a PWR is of crucial engineering significance.

[0003] Currently, there are two main technical approaches to studying the aforementioned behaviors: numerical simulation and experimental research. In numerical simulation, software for calculating the source term of activated corrosion products is used to divide the primary loop into several nodes based on in-pile and out-of-pile conditions and physical states. Based on a concentration-driven mass balance equation, combined with semi-empirical formulas, the generation, transport, activation, and deposition of corrosion products are simulated. In experimental research, corrosion release is obtained primarily through mass change estimation, hydrochemical analysis of the full zirconium / gold-lined loop, or sampling from actual units. Simultaneously, migration and deposition experiments of corrosion products are conducted using the out-of-pile hydrodynamic loop to obtain quantitative experimental data for influencing factor analysis.

[0004] However, the above methods are fragmented in their study of migration-activation-deposition behavior, and the coupling feedback relationship between the three processes is not systematically reflected, thus failing to truly reflect the complete material cycle within the primary loop. Summary of the Invention

[0005] The purpose of this invention is to provide a method, apparatus, equipment and medium for simulating the migration-activation-deposition behavior of corrosion products in the primary loop of a pressurized water reactor, which can solve the problem of not being able to completely simulate the migration, activation and deposition behavior of corrosion products.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a method for simulating the migration, activation, and deposition behavior of corrosion products in the primary loop of a pressurized water reactor, comprising the following steps: The primary loop of the pressurized water reactor is divided into multiple nodes; Based on the existence form and migration parameters of corrosion products in the primary coolant of a pressurized water reactor obtained through pre-designed migration tests, a migration term describing the convection of corrosion products between nodes and the release term of corrosion products into the coolant are constructed. By modeling the core structure in multiple nodes, the neutron flux within the core structure is simulated, and activation terms and decay terms describing the activation of corrosion products within the core structure due to neutron irradiation and the decay of activated products are constructed based on the neutron flux. Based on the deposition and release parameters of corrosion products at each node obtained through pre-designed deposition experiments, deposition terms describing corrosion products from coolant adhesion to the node and re-release terms describing corrosion products from the node re-entering the coolant. The migration, release, activation, decay, deposition, and re-release terms are coupled to establish a multi-node mass transport model that describes the mass changes of corrosion products in each node. The behavior of corrosion products in the primary loop of a pressurized water reactor is iteratively simulated by using a multi-node mass transport model to simulate the migration, release, activation, decay, deposition, and re-release of corrosion products at each time step, as well as the behavior of deposited and re-released corrosion products in the next time step.

[0007] Furthermore, the corrosion products include non-radioactive corrosion products and radioactive corrosion products; The coupling of migration, release, activation, decay, deposition, and re-release terms to establish a multi-node mass transport model describing the mass changes of corrosion products in each node includes: The migration, release, deposition, and re-release terms are coupled to establish a multi-node mass transport model to describe the mass changes of non-radioactive corrosion products in each node. The migration, release, activation, decay, deposition, and re-release terms are coupled to establish a multi-node mass transport model that describes the mass changes of radioactive corrosion products in each node.

[0008] Furthermore, the simulation of the migration, release, activation, decay, deposition, and re-release of corrosion products at each node using a multi-node mass transport model, as well as the behavior of deposited and re-released corrosion products in the next time step, iteratively simulates the behavior of corrosion products in the primary loop of the pressurized water reactor, including: Within each time step, based on the operator splitting method, the concentrations of corrosion products migrated and released at each node are determined according to the migration and release terms in the multi-node mass transport model. Based on the activation and decay terms in the multi-node mass transport model, and the concentration of corrosion products that migrate and are released at each node, determine the concentration of corrosion products that are activated and decayed at each node. Based on the deposition and re-release terms in the multi-node mass transport model, as well as the concentration of corrosion products activated and decayed at each node, the deposition thickness of corrosion products and the concentration of re-released corrosion products at each node are determined. Based on the deposition thickness of corrosion products at each node, determine the actual flow area of ​​coolant in each node within the next time step; Based on the actual flow area of ​​the coolant and the concentration of the re-released corrosion products, the concentrations of the migrated and released corrosion products at each node in the next time step are determined using migration and release terms, so as to obtain the changes in the concentrations of corrosion products deposited on each node and in the coolant through iterative simulation.

[0009] Furthermore, the coupled multi-node mass transport model corresponding to the non-radioactive corrosion products is as follows: ; In the formula, Let the mass of the corrosion products in node i be . Let be the coolant flow rate from node j to node i. Let J be the concentration of corrosion products in the coolant at node j. The corrosion release rate of the structural material within node i. The deposition rate of corrosion products within node i. Let be the re-release rate of sediment within node i.

[0010] Furthermore, the coupled multi-node mass transport model corresponding to the radioactive corrosion products is as follows: ; In the formula, Let i represent the activity of the radionuclide in node i. Let be the activity of the radionuclide in the coolant at node j. The decay constant is Let i be the number of nucleus atoms in node i. To activate the cross section, Let be the neutron flux at node i.

[0011] Furthermore, the release rate for: ; In the formula, Pre-exponential factor, For activation energy, The gas constant is For temperature, For the wetted area, This refers to the ion concentration in the coolant. The reaction order is [number]. Deposition rate for: ; In the formula, The mass transfer coefficient of sedimentation. This refers to the main concentration in the coolant. For material surface concentration, The deposition area is denoted as .

[0012] Furthermore, after coupling the migration, release, activation, decay, deposition, and re-release terms to establish a multi-node mass transport model describing the mass changes of corrosion products in each node, the model further includes: The corrosion product concentration of each node in the primary loop of the pressurized water reactor was obtained by simulating the corrosion product concentration of each node through a multi-node mass transport model, and a virtual pressurized water reactor primary loop was constructed based on the corrosion product concentration of each node obtained by simulation. Simulate gamma rays passing through multiple key measurement points in the primary loop of a virtual pressurized water reactor to obtain the corresponding dose rate; The simulated dose rate was compared with the actual measured dose rate, and the multi-node mass transport model was corrected based on the comparison results.

[0013] Embodiments of the present invention also provide a device for simulating the migration-activation-deposition behavior of corrosion products in the primary loop of a pressurized water reactor, comprising: The loop partitioning module is used to divide the pressurized water reactor primary loop into multiple nodes; The migration simulation module is used to construct migration terms that describe the convection of corrosion products between nodes and the release of corrosion products into the coolant, based on the existence form and migration parameters of corrosion products in the primary coolant of the pressurized water reactor obtained through pre-designed migration tests. The activation simulation module is used to model the core structure in multiple nodes, simulate the neutron flux within the core structure, and construct activation terms and decay terms to describe the activation of corrosion products within the core structure due to neutron irradiation and the decay of activated products based on the neutron flux. The deposition simulation module is used to construct deposition terms that describe the deposition of corrosion products from coolant to nodes and the re-release terms that describe the re-release of corrosion products from nodes back into the coolant, based on the deposition and release parameters of corrosion products at each node obtained through pre-designed deposition experiments. The model building module is used to couple migration, release, activation, decay, deposition and re-release terms to establish a multi-node mass transport model to describe the mass changes of corrosion products in each node. The model simulation module is used to simulate the behavior of corrosion products at each node in the primary loop of a pressurized water reactor by migrating, releasing, activating, decaying, depositing, and re-releasing at each time step, as well as the behavior of deposited and re-released corrosion products in the next time step, through a multi-node mass transport model.

[0014] Embodiments of the present invention also provide a computer device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the above-described simulation method for the migration-activation-deposition behavior of corrosion products in the primary loop of a pressurized water reactor.

[0015] Embodiments of the present invention also provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described simulation method for the migration-activation-deposition behavior of corrosion products in the primary loop of a pressurized water reactor.

[0016] The simulation method for the migration, activation, and deposition behavior of primary circuit corrosion products in pressurized water reactors provided by this invention has at least the following beneficial effects: This invention first divides the primary loop of a pressurized water reactor into multiple nodes, and then establishes a multi-node mass transport model to describe the behavior of each node in the entire process of convective transport, corrosion release, neutron activation, radioactive decay, deposition, and re-release (re-suspension). This model can simulate the behavior of corrosion products at each node in the migration, release, activation, decay, deposition, and re-release within a time step, as well as the behavior of deposited and re-released corrosion products in the next time step. This simulation process takes into account the influence of the behavior of corrosion products in the previous time step on the behavior in the next time step, thus completely simulating the cyclic behavior of corrosion products inside the primary loop of a pressurized water reactor.

[0017] Furthermore, in the multi-node mass transport model, the migration, release, deposition, and re-release terms are directly and quantitatively measured using a self-designed experimental loop, without relying on existing empirical formulas. The established model terms are more consistent with the actual behavior of corrosion products. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 A schematic diagram of a simulation method for the migration, activation, and deposition behavior of corrosion products in the primary loop of a pressurized water reactor provided by the present invention; Figure 2 A schematic diagram of a technical route provided by the present invention; Figure 3 A schematic diagram of a high-temperature and high-pressure test circuit system provided by the present invention; Figure 4 A schematic diagram of a single-loop node partitioning provided by the present invention; Figure 5 A schematic diagram of a thermal deposition loop system provided by the present invention; Figure 6 A schematic diagram of a key measurement point in a single loop provided by the present invention; Figure 7 This is a geometric schematic diagram of a Monte Carlo dose rate calculation model provided by the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] Existing research on the migration, activation, and deposition behavior of corrosion products in the primary loop of pressurized water reactors suffers from several problems, including a disconnect between numerical simulation and experimental verification, fragmented research on the three key processes (migration, activation, and deposition), a lack of systematic parameter sensitivity analysis, a lack of supporting verification methods for source term calculation software, and a lack of model verification methods based on measured dose rates.

[0022] This invention provides a method for studying the migration, activation, and deposition behavior of corrosion products in the primary loop of a pressurized water reactor. It integrates the three processes of migration, activation, and deposition into a unified research framework, coupling numerical simulation with experimental verification. Furthermore, it introduces a dose rate modeling and calculation method based on Monte Carlo software for key primary loop measurement points, comparing the calculated dose rate with the measured dose rate at the nuclear power plant to accurately verify the activation product source term model. Simultaneously, this method enables cross-scale analysis from microscopic deposition mechanisms to macroscopic loop distribution, systematically revealing the comprehensive influence of water chemical parameters and thermo-hydraulic parameters on corrosion product behavior. It also provides systematic and quantitative experimental data support for the verification of domestically developed source term calculation software.

[0023] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] One embodiment of the present invention relates to a simulation method for the migration, activation, and deposition behavior of corrosion products in the primary loop of a pressurized water reactor. The specific process of the simulation method for the migration, activation, and deposition behavior of corrosion products in the primary loop of a pressurized water reactor in this embodiment can be as follows: Figure 1 As shown, it includes: Step 101: Divide the pressurized water reactor primary loop into multiple nodes; Step 102: Based on the existence form and migration parameters of corrosion products in the primary coolant of the pressurized water reactor obtained through pre-designed migration tests, construct migration terms to describe the convection of corrosion products between nodes and the release terms of corrosion products into the coolant. Step 103: By modeling the core structure in multiple nodes, the neutron flux in the core structure is simulated and obtained. Based on the neutron flux, activation terms are constructed to describe the activation of corrosion products in the core structure due to neutron irradiation and decay terms to describe the decay of activated products. Step 104: Based on the deposition parameters and release parameters of corrosion products at each node obtained through a pre-designed deposition test, construct a deposition term to describe the deposition of corrosion products from coolant to the node and a re-release term to describe the re-entry of corrosion products from the node into the coolant. Step 105: Couple the migration, release, activation, decay, deposition and re-release terms to establish a multi-node mass transport model to describe the mass changes of corrosion products in each node. Step 106: Simulate the behavior of corrosion products in the primary loop of the pressurized water reactor by using a multi-node mass transport model to simulate the migration, release, activation, decay, deposition, and re-release of corrosion products at each time step, as well as the behavior of deposited and re-released corrosion products in the next time step.

[0025] Specifically, the corrosion products in this embodiment include non-radioactive corrosion products and radioactive corrosion products. Therefore, when establishing a multi-node mass transport model to describe the mass change of corrosion products in each node: the migration term, release term, deposition term, and re-release term are coupled to establish a multi-node mass transport model to describe the mass change of non-radioactive corrosion products in each node; the migration term, release term, activation term, decay term, deposition term, and re-release term are coupled to establish a multi-node mass transport model to describe the mass change of radioactive corrosion products in each node.

[0026] To simulate the behavior of radioactive corrosion products in the primary loop of a pressurized water reactor: Within each time step, based on the operator splitting method, the concentrations of corrosion products migrating and releasing at each node are determined according to the migration and release terms in the multi-node mass transport model; the concentrations of activated and decaying corrosion products at each node are determined according to the activation and decay terms in the multi-node mass transport model, as well as the concentrations of corrosion products migrating and releasing at each node; the deposition thickness and re-release concentration of corrosion products at each node are determined according to the deposition thickness of corrosion products at each node; the actual flow area of ​​coolant in each node in the next time step is determined according to the actual flow area of ​​coolant and the concentration of re-released corrosion products; and the concentrations of migration and release corrosion products at each node in the next time step are determined using the migration and release terms, thus obtaining the changes in the concentrations of corrosion products deposited on each node and in the coolant through iterative simulation.

[0027] In some embodiments, after establishing a multi-node mass transport model to describe the mass change of corrosion products in each node: the concentration of corrosion products in each node of the pressurized water reactor primary loop is obtained by simulating the multi-node mass transport model, and a virtual pressurized water reactor primary loop is constructed based on the concentration of corrosion products in each node obtained by simulation; gamma rays are simulated to pass through multiple key measurement points in the virtual pressurized water reactor primary loop to obtain the corresponding dose rate; the dose rate obtained by simulation is compared with the actual measured dose rate, and the multi-node mass transport model is corrected based on the comparison results.

[0028] The following details the implementation of the simulation method for the migration, activation, and deposition behavior of corrosion products in the primary loop of a pressurized water reactor in this embodiment. The following content is only for the convenience of understanding and is not necessary for implementing this solution.

[0029] This embodiment establishes a multi-node mass transport balance equation to couple the three processes of migration, activation, and deposition. It also uses a self-designed experimental loop system to obtain key characteristic parameters. Then, it uses Monte Carlo software to perform dose rate modeling and calculation on key measurement points of the primary loop, and compares and verifies the results with the measured dose rate of a nuclear power plant, thus forming a closed-loop verification research system.

[0030] The overall technical approach of this embodiment is as follows: Figure 2 As shown, it includes the following four stages executed sequentially: Phase 1: Study on the migration behavior of corrosion products – By experimentally determining parameters such as the solubility / particulate distribution and migration rate of corrosion products in the coolant, a multi-node mass transport model is established.

[0031] Phase Two: Study on the Activation Behavior of Corrosion Products – Based on neutron transport calculations, the neutron flux distribution in the reactor core is obtained, and the generation and decay of activation products are calculated using an activation cross-section database.

[0032] Phase 3: Study on the deposition behavior of corrosion products – Deposition rate, re-release rate and microstructure parameters of deposition layer on different material surfaces are obtained through deposition experiments.

[0033] Phase 4: Coupled Modeling and Verification – The three sub-models mentioned above are coupled into a unified computational framework, and Monte Carlo software is used to model the dose rate of key measurement points in the primary loop. The model parameters are then iteratively corrected by comparing the measured dose rate with that of the nuclear power plant.

[0034] Phase 1: Study on the migration behavior of corrosion products: 1. Experimentally determine the distribution of dissolved and particulate states.

[0035] High-temperature and high-pressure test circuit system (see) Figure 3 (Schematic diagram of the high-temperature and high-pressure test circuit system). This circuit mainly includes: a main circulation pump, a preheater, a test section, a cooler, a filter, a sampling valve, a dissolved oxygen / dissolved hydrogen analyzer, a conductivity / pH meter, a pressure sensor, a temperature sensor, and a data acquisition and control system. The main body of the circuit is made of 316L stainless steel, and the inner surface is passivated to reduce interference from the circuit's own corrosion products.

[0036] Experimental steps: (1) Adjust the test loop to simulate the primary loop conditions of a pressurized water reactor: temperature 280~320℃ (typical value 300℃), pressure 15~16 MPa (typical value 15.5 MPa), flow rate 1~5 m / s (adjustable), dissolved hydrogen concentration 25~50 cm³ / kg (typical value 30 cm³ / kg), dissolved oxygen concentration <5 ppb, pH value (measured at room temperature) 6.8~7.2.

[0037] (2) Install the test sample (such as Inconel 690 alloy, 304 stainless steel, etc.) in the test section and start the circuit to run for 168~720 hours.

[0038] (3) Collect coolant samples periodically through the sampling valve. After the samples are cooled to room temperature, filter them with a 0.45 μm filter membrane. Measure the concentration of metal ions in the filtrate (using inductively coupled plasma mass spectrometry ICP-MS) and the content of metal elements in the filter residue (using energy dispersive X-ray fluorescence spectrometry ED-XRF). Calculate the mass fraction of dissolved and particulate states.

[0039] (4) Change the flow rate, temperature, pH, dissolved hydrogen and other parameters, repeat the above experiment to obtain the distribution coefficient under different working conditions.

[0040] 2. Establishment of a multi-node mass transport model.

[0041] The primary loop system is divided into 105 nodes (see...). Figure 4 (Diagram showing the primary circuit node division). Nodes include: core active zone, upper and lower core chambers, cold legs, hot legs, primary side of the steam generator, main pumps, pressurizer, etc. Each node is assumed to have uniform parameters, and mass exchange occurs between nodes via coolant flow.

[0042] Establish the mass conservation equation for corrosion products in the i-th node: For non-radioactive corrosion products (M): ; in: : Mass of corrosion products in node i (kg); : Coolant flow rate (kg / s) from node j to node i; : Concentration of corrosion products in coolant at node j (kg / kg); : Corrosion release rate of structural material within node i (kg / s); : Deposition rate of corrosion products within node i (kg / s); : Resuspension (re-release) rate of sediments within node i (kg / s).

[0043] For radionuclides (such as 58 Co、 60 Co、 54 Mn, etc.), add activation and decay terms: ; in: : Radionuclide activity (Bq) in node i; : Concentration of radionuclide activity in coolant at node j (Bq / kg); Decay constant (s -1 ); : The number of parent nucleus atoms in node i; Activation section (m) 2 ); : Neutron flux at node i (n / (m) 2 ·s)).

[0044] Release rate Using an Arrhenius-type empirical formula: ; in: Pre-exponential factor, For activation energy, The gas constant is For temperature, For the wetted area, This refers to the ion concentration in the coolant. This represents the reaction order. The parameters were obtained by fitting experimental data.

[0045] Deposition rate A model based on the mass transfer coefficient is adopted: ; in: The deposition mass transfer coefficient (calculated using the Chilton-Colburn analogy). This refers to the main concentration in the coolant. For material surface concentration, The deposition area is denoted as .

[0046] The above differential equations are solved using the implicit Runge-Kutta method, with the time step dynamically adjusted according to the operating conditions (1 d in steady state and 1 h in transient state).

[0047] In this embodiment, the primary loop is divided into nodes such as the core active zone, upper and lower chambers, hot and cold legs, steam generator, main pump, and pressurizer. A set of mass conservation differential equations considering convective transport, corrosion release, deposition, resuspension, activation, and decay is established and solved using the implicit Runge-Kutta method, thus realizing a system-level quantitative description of the behavior of corrosion products.

[0048] Phase Two: Study on the Activation Behavior of Corrosion Products 1. Calculation of neutron flux distribution.

[0049] The in-core neutron flux density is modeled and calculated using MCNP. Although the core structure is complex, it exhibits repetition and symmetry. During core MCNP modeling, repeating structure cards (U cards) and filler cards (FIL cards) are used to fill the core regions with components, and rod (tube) fillers are used for each component region.

[0050] Based on the symmetry of the reactor core, the scale of the full core model can be reduced to 1 / 8 of the core to reduce the computational load in subsequent MCNP simulations. Due to the symmetry of the core structure, performing an MCNP simulation on 1 / 8 of the core is equivalent to simulating the full core. The radial structure of the reactor is as follows: core, confining wall, confining wall, and cradle (structures other than the cradle are not considered for now). The axial structure of the reactor is as follows: lower support plate, core, water layer, and upper plate (structures other than the upper plate and the lower support plate are not considered for now). After the above modeling and programming, the model diagram was drawn using the drawing tools provided with MCNP. Based on the MCNP model of 1 / 8 of the core, part of the radial perimeter structure, and part of the axial perimeter, the neutron and gamma distribution of the core fuel assemblies was simulated using the criticality calculation card KCODE. To facilitate the programming of the input card and subsequent data processing, 5574 rod (tube) cells within the range of 0~45° were considered in the simulation. The detection grids for fuel rods are taken from the core block grids, the detection grids for empty guide tubes are taken from the coolant grids inside the tube, and the detection grids for combustible toxic rods are taken from the grids inside the liner tube. If data processing is to be normalized, the flux of the coolant grids inside the guide tube is used as the standard.

[0051] The F4 card was used to count neutrons in the reactor core fuel assemblies. The 26 assemblies involved in 1 / 8 of the core comprised 7514 rods (tubes), including 6864 fuel rods, of which 5774 rods (tubes) were in the 0-45°C range. The simulation calculations were performed under the following conditions: an average core coolant temperature of 305°C, an average outlet coolant temperature of 320°C, and a boric acid concentration of 1000 ppm in the coolant. The calculations were conducted under KCODE 500001300 1000. The reactor structure is complex and large-scale, resulting in a very high neutron flux in the core. However, the neutron flux outside the core gradually decreases, decreasing by approximately 9-10 orders of magnitude to the concrete shield. When calculating the activation products within the reactor's primary loop, the activation of corrosion deposits on some internal components can be disregarded.

[0052] 2. Calculation of activation product formation and decay.

[0053] After corrosion products are deposited in the active zone of the reactor core, under neutron irradiation, the originally stable atomic nuclei are transformed into radioactive nuclides through neutron capture. This radioactivity is called induced radioactivity, and the process is called activation. The main activation reactions are (n, γ), (n, p), and (n, α) reactions. The amount of target atomic nuclei activated by neutron irradiation within the active zone of the reactor core is:

[0054] ; Where: n is the number of activated nuclei generated; V is the effective volume within the active region, in cm. 3 Σ represents the macroscopic cross-section of the activation reaction, in cm. -1 ; The neutron flux density within the pile is given by cm⁻¹. -2 s -1 ; The number of target nuclei per unit volume; For the microscopic cross-section of the activation reaction, cm 2 .

[0055] The radioactive nuclides generated during activation will disappear from the system through two mechanisms: decay and passivation. ; Its rate is: ; Radioactive nuclides all decay according to an exponential law: ; in: is the decay constant.

[0056] Phase 3: Study on the deposition behavior of corrosion products: 1. Deposition test apparatus and procedures.

[0057] Employing a self-designed heating deposition loop system (see...) Figure 5 (Schematic diagram of thermal deposition loop system) mainly includes: autoclave, heating components, sample holder, circulating pump, heat exchanger, water chemistry control system, and online gamma spectrometer.

[0058] Experimental steps: (1) Install deposition samples of different materials (size 50 mm × 30 mm × 2 mm) on the sample holder, including: stainless steel, nickel-based alloy, zirconium alloy, etc.

[0059] (2) Add a solution simulating the primary loop water chemistry of a pressurized water reactor (boric acid 1000~2000 ppm, lithium hydroxide 2~5 ppm, dissolved hydrogen 30 cm³ / kg) to the autoclave.

[0060] (3) A heat flux density of 100~800 kW / m² is generated on the sample surface by heating components to simulate the supercooled nucleation boiling conditions on the fuel rod surface.

[0061] (4) Add a non-radioactive tracer (such as Fe2O3 nanoparticles, concentration 1~10 ppm) to the circuit and run for 168 hours.

[0062] (5) After the test, the sample was removed and the deposition layer was characterized using the following methods: The surface and cross-sectional morphology of the deposited layer were observed using a scanning electron microscope (SEM), and the thickness was measured.

[0063] Transmission electron microscopy (TEM) was used to analyze the crystal structure of the deposited layer.

[0064] X-ray diffraction (XRD) is used to determine the phase composition (Fe3O4, NiFe2O4, etc.).

[0065] X-ray photoelectron spectroscopy (XPS) analysis of elemental valence states.

[0066] (6) The activity change of the radioactive tracer in the online gamma spectrometer monitoring loop was used to calculate the deposition rate by combining the concentration difference of the solution before and after deposition. and re-release rate : ; ; in: This represents the change in the concentration of corrosion products in the coolant before and after the test, i.e., the initial concentration minus the final concentration. This refers to the total volume of coolant in the test circuit; The total surface area of ​​the deposited surface; This represents the main average concentration of corrosion products in the coolant during the test. For time step; The mass of the deposits on the sample surface is the total mass (instantaneous mass at time t). The rate of change of sediment mass over time.

[0067] 2. Calibration of sedimentation model parameters.

[0068] The sedimentation rate, re-release rate, and sediment thickness obtained from the experiment were used to regress sedimentation model parameters (such as mass transfer coefficient and adhesion probability) under different materials and different thermal-hydraulic conditions, and a sedimentation parameter database was established.

[0069] This embodiment employs a self-designed experimental loop system (including a dissolved oxygen / dissolved hydrogen analyzer, an online gamma spectrometer, etc.) to quantitatively determine key parameters such as the dissolved / particulate distribution coefficient, deposition mass transfer coefficient, and re-release rate of corrosion products under different materials and different thermal water chemical conditions through controlled variable experiments, providing systematic and quantitative data support for the coupled model.

[0070] Using multiple characterization methods such as SEM, TEM, XRD, and XPS, combined with real-time monitoring data from an online gamma spectrometer, a quantitative correlation was established between sediment thickness, phase composition, elemental valence state, and sedimentation / re-release kinetic parameters, providing experimental basis for parameter calibration of sedimentation models.

[0071] Phase Four: Modeling the Migration-Activation-Deposition Coupling 1. Coupling strategy.

[0072] The operator splitting method is used to calculate the migration, activation, and deposition processes sequentially within the same time step: (1) First, solve the migration equation (without considering activation and deposition) to obtain the convective diffusion distribution of corrosion products.

[0073] (2) Then solve the activation equation (based on the current neutron flux and nuclide density) to update the activity of radionuclides.

[0074] (3) Finally, solve the deposition equation (based on the current concentration and surface condition) to update the deposition layer quality and thickness.

[0075] (4) Feeding the deposition layer thickness back to the surface area in the migration equation and mass transfer coefficient .

[0076] (5) The radionuclides accumulated in the sediment layer are used as the re-release source term and added to the migration equation of the next time step.

[0077] Iterative convergence criterion: The change in node activity between two adjacent steps is less than 0.1% or the relative error is less than 10. -6 .

[0078] 2. Software implementation.

[0079] Write a coupled computation program using Python or Fortran, and call the following external libraries: SCIPY: Solving systems of differential equations OpenMC or MCNP interface: Obtain neutron flux distribution ENDF / B-VII.1: Nuclear Data Program inputs: primary loop geometric parameters, operating conditions (temperature, pressure, flow rate, power history), water chemistry parameters, material corrosion release parameters, etc. Outputs: changes in nuclide activity concentration over time in the coolant and sediment layer at each node, total activity distribution, sediment layer thickness distribution, etc.

[0080] This embodiment incorporates the migration, activation, and deposition behaviors of corrosion products in the primary loop of a pressurized water reactor into a unified research framework. It achieves iterative coupled calculation of the three processes through multi-node mass transport balance equations and operator splitting method, overcoming the shortcomings of existing technologies that study the three processes separately.

[0081] Phase 5: Monte Carlo Dose Rate Modeling and Experimental Validation 1. Monte Carlo dose rate modeling.

[0082] Select key measuring points below the primary circuit of the pressurized water reactor (see...) Figure 6(Schematic diagram of key measuring points in the primary loop): Measuring point P1: outer surface of reactor pressure vessel; Measuring point P2: outer side of main pump inlet and outlet pipes; Measuring point P3: transition section; Measuring point P4: horizontal section of cold leg; Measuring point P5: horizontal section of cold leg; Measuring point P6: horizontal section of cold leg; Measuring point P7: outer side of primary side inlet tube sheet of steam generator; Measuring point P8: outer side of primary side outlet tube sheet of steam generator.

[0083] A three-dimensional dose rate calculation model was established using MCNP5 software (see [link]). Figure 7 (Geometric schematic diagram of the Monte Carlo dose rate calculation model) Modeling steps: (1) Geometric modeling: Based on the construction drawings of the nuclear power plant, establish the precise geometry of the pressure vessel, pipeline, main pump, steam generator, and shielding layer (concrete, lead, water), and use the combination (cell) description.

[0084] (2) Material assignment: Define the material composition (density, element mass fraction) of each region. The coolant density is 0.71 g / cm³ based on the operating pressure of 15.5 MPa and temperature of 310℃. The sediment density is 85% of the theoretical density (porosity of 15%), and the thickness is the local sediment thickness calculated by the coupled model.

[0085] (3) Source term definition: The activity concentrations of radionuclides in the coolant and sediment layer at each node calculated by the coupled model are mapped to the MCNP geometric model according to their spatial locations. The source distribution adopts a volume source, and the emitted photon energy and intensity are taken from the nuclide decay diagram.

[0086] (4) Transport parameters: The particle type is set to photon, the lower energy cutoff is 10 keV, and the number of transport particles is 1×10 8 To ensure statistical error <3%, the counting method used was an F6 counting card (energy deposition, unit MeV / g), which was then multiplied by a dose rate conversion factor (using ANS 6.1.1-1991 standard) to obtain the γ dose rate (μSv / h).

[0087] 2. Obtaining the measured dose rate at nuclear power plants.

[0088] Under the same operating conditions of the corresponding nuclear power plant (identical to the modeled object) (e.g., end of fuel cycle, 100% thermal power), measurements were taken at the five key measurement points using a calibrated portable dose rate meter (model: FH 40G, energy response range 48 keV~3 MeV). Each measurement point was measured three times, with each measurement lasting one minute, and the average value was taken. Simultaneously, parameters such as reactor power, coolant temperature, boron concentration, and operating time were recorded to ensure consistency with the simulation calculation conditions.

[0089] 3. Comparative verification and closed-loop correction.

[0090] The calculated dose rate from Monte Carlo simulations is compared with the measured dose rate, and the relative deviation δ is calculated: ; The acceptance threshold is set as |δ|≤20%. If all measuring points meet the threshold, the verification is passed; if any measuring point exceeds the threshold, deviation source analysis is performed.

[0091] After correction, the coupled model and Monte Carlo calculations are rerun and compared again until all measurement points meet the threshold requirements, forming a closed-loop verification process of "source term model → dose rate calculation → actual measurement comparison → parameter correction".

[0092] This embodiment uses the source term distribution output by the coupled model as input, uses Monte Carlo software to perform dose rate modeling and calculation on key measurement points of the primary loop, and compares it point by point with the measured dose rate under the same operating conditions of the nuclear power plant. The model parameters are corrected in reverse through deviation analysis, forming a closed-loop verification process of "source term model → dose rate calculation → measured comparison → parameter correction".

[0093] Key measuring points such as the outer surface of the pressure vessel, the inlet and outlet of the main pump, the primary side inlet and outlet of the steam generator, the bottom of the pressurizer, and the horizontal section of the cold leg were selected. A three-dimensional Monte Carlo dose rate calculation model was established based on the actual geometric dimensions, material composition, and source term distribution of the nuclear power plant, and the calculated dose rate was directly compared and verified with the measured value.

[0094] The simulation method for the migration, activation, and deposition behavior of primary circuit corrosion products in pressurized water reactors of the present invention has the following beneficial effects: 1. Full-process coupling, overcoming process fragmentation: Existing technologies treat the migration, activation, and deposition of corrosion products separately, neglecting the mutual feedback among the three. This invention uses a multi-node mass transport equation and operator splitting method to solve the three processes in a unified iterative manner, which can truly reflect the complete cycle of "corrosion release → coolant migration → core activation → off-core redeposition", significantly improving calculation accuracy (verified). 60 The prediction bias for Co activity decreased from ±45% to ±15%.

[0095] 2. Closed-loop verification to address the disconnect between simulation and experiment: Existing technologies often lack systematic experimental data support for numerical models, and verification is mostly based on single comparisons. This invention establishes a closed-loop verification process of "source term model → Monte Carlo dose rate simulation → power plant measured comparison → parameter correction," using real radiation monitoring data from nuclear power plants to iteratively calibrate the model, thus verifying the model's reliability on an engineering scale.

[0096] 3. Parameter Quantification, Filling Data Gaps: Existing models heavily rely on empirical formulas, lacking systematic experimental data for characteristic parameters. This invention, through a self-designed high-temperature and high-pressure experimental circuit, quantitatively measures key parameters such as dissolution / particle partition coefficient, deposition mass transfer coefficient, and re-release rate under different materials and operating conditions, providing a directly accessible basic database for domestic source term calculation software.

[0097] 4. Innovative engineering verification methods with low implementation costs: Existing technologies mostly employ in-core irradiation tests or small loop verification, which are costly and time-consuming. This invention directly utilizes existing dose rate monitoring data from nuclear power plant operations, comparing the results with calculations through Monte Carlo modeling. No additional irradiation tests are required, and the verification results directly reflect real operating conditions, demonstrating significant economic efficiency and engineering practicality.

[0098] In summary, the present invention is superior to the prior art in terms of technical integrity, model accuracy, data support, and engineering applicability.

[0099] The steps of the various methods described above are only for clarity. In practice, they can be combined into one step or some steps can be split into multiple steps. As long as they include the same logical relationship, they are all within the protection scope of this invention. Adding insignificant modifications or introducing insignificant designs to the algorithm or process, without changing the core design of the algorithm and process, are also within the protection scope of this invention.

[0100] Another embodiment of the present invention relates to a simulation device for the migration, activation, and deposition behavior of corrosion products in the primary loop of a pressurized water reactor. The implementation details of this simulation device are described below. The following details are provided for ease of understanding and are not essential for implementing this solution. The simulation device for the migration, activation, and deposition behavior of corrosion products in the primary loop of a pressurized water reactor in this embodiment includes: The loop partitioning module is used to divide the pressurized water reactor primary loop into multiple nodes; The migration simulation module is used to construct migration terms that describe the convection of corrosion products between nodes and the release of corrosion products into the coolant, based on the existence form and migration parameters of corrosion products in the primary coolant of the pressurized water reactor obtained through pre-designed migration tests. The activation simulation module is used to model the core structure in multiple nodes, simulate the neutron flux within the core structure, and construct activation terms and decay terms to describe the activation of corrosion products within the core structure due to neutron irradiation and the decay of activated products based on the neutron flux. The deposition simulation module is used to construct deposition terms that describe the deposition of corrosion products from coolant to nodes and the re-release terms that describe the re-release of corrosion products from nodes back into the coolant, based on the deposition and release parameters of corrosion products at each node obtained through pre-designed deposition experiments. The model building module is used to couple migration, release, activation, decay, deposition and re-release terms to establish a multi-node mass transport model to describe the mass changes of corrosion products in each node. The model simulation module is used to simulate the behavior of corrosion products at each node in the primary loop of a pressurized water reactor by migrating, releasing, activating, decaying, depositing, and re-releasing at each time step, as well as the behavior of deposited and re-released corrosion products in the next time step, through a multi-node mass transport model.

[0101] It is not difficult to see that this embodiment is a device embodiment corresponding to the above method embodiments, and this embodiment can be implemented in conjunction with the above method embodiments. The relevant technical details and technical effects mentioned in the above embodiments are still valid in this embodiment, and will not be repeated here to reduce repetition. Accordingly, the relevant technical details mentioned in this embodiment can also be applied to the above embodiments.

[0102] It is worth mentioning that all modules involved in this embodiment are logical modules. In practical applications, a logical unit can be a physical unit, a part of a physical unit, or a combination of multiple physical units. Furthermore, to highlight the innovative aspects of this invention, this embodiment does not introduce units that are not closely related to solving the technical problem proposed by this invention; however, this does not mean that other units are absent from this embodiment.

[0103] Another embodiment of the present invention relates to a computer device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the simulation method for the migration-activation-deposition behavior of pressurized water reactor primary circuit corrosion products in the above embodiments.

[0104] The memory and processor are connected via a bus, which can include any number of interconnecting buses and bridges, connecting various circuits of one or more processors and memories. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and will not be described further herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by the processor is transmitted over the wireless medium via an antenna, which further receives data and transmits it to the processor.

[0105] The processor manages the bus and general processing, and also provides various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory is used to store data used by the processor during operation.

[0106] Another embodiment of the present invention relates to a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the method embodiments described above.

[0107] That is, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of the present 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.

[0108] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A method for simulating the migration-activation-deposition behavior of corrosion products in the primary loop of a pressurized water reactor, characterized in that, The method includes: The primary loop of the pressurized water reactor is divided into multiple nodes; Based on the existence form and migration parameters of corrosion products in the primary coolant of a pressurized water reactor obtained through pre-designed migration tests, a migration term describing the convection of corrosion products between nodes and the release term of corrosion products into the coolant are constructed. By modeling the core structure in multiple nodes, the neutron flux within the core structure is simulated, and activation terms and decay terms describing the activation of corrosion products within the core structure due to neutron irradiation and the decay of activated products are constructed based on the neutron flux. Based on the deposition and release parameters of corrosion products at each node obtained through pre-designed deposition experiments, deposition terms describing corrosion products from coolant adhesion to the node and re-release terms describing corrosion products from the node re-entering the coolant. The migration, release, activation, decay, deposition, and re-release terms are coupled to establish a multi-node mass transport model that describes the mass changes of corrosion products in each node. The behavior of corrosion products in the primary loop of a pressurized water reactor is iteratively simulated by using a multi-node mass transport model to simulate the migration, release, activation, decay, deposition, and re-release of corrosion products at each time step, as well as the behavior of deposited and re-released corrosion products in the next time step.

2. The simulation method for the migration-activation-deposition behavior of primary loop corrosion products in a pressurized water reactor according to claim 1, characterized in that, The corrosion products include non-radioactive corrosion products and radioactive corrosion products; The coupling of migration, release, activation, decay, deposition, and re-release terms to establish a multi-node mass transport model describing the mass changes of corrosion products in each node includes: The migration, release, deposition, and re-release terms are coupled to establish a multi-node mass transport model to describe the mass changes of non-radioactive corrosion products in each node. The migration, release, activation, decay, deposition, and re-release terms are coupled to establish a multi-node mass transport model that describes the mass changes of radioactive corrosion products in each node.

3. The simulation method for the migration-activation-deposition behavior of primary loop corrosion products in a pressurized water reactor according to claim 2, characterized in that, The method simulates the migration, release, activation, decay, deposition, and re-release of corrosion products at each node within each time step using a multi-node mass transport model, as well as the behavior of deposited and re-released corrosion products in the next time step, to iteratively simulate the behavior of corrosion products in the primary loop of a pressurized water reactor, including: Within each time step, based on the operator splitting method, the concentrations of corrosion products migrated and released at each node are determined according to the migration and release terms in the multi-node mass transport model. Based on the activation and decay terms in the multi-node mass transport model, and the concentration of corrosion products that migrate and are released at each node, determine the concentration of corrosion products that are activated and decayed at each node. Based on the deposition and re-release terms in the multi-node mass transport model, as well as the concentration of corrosion products activated and decayed at each node, the deposition thickness of corrosion products and the concentration of re-released corrosion products at each node are determined. Based on the deposition thickness of corrosion products at each node, determine the actual flow area of ​​coolant in each node within the next time step; Based on the actual flow area of ​​the coolant and the concentration of the re-released corrosion products, the concentrations of the migrated and released corrosion products at each node in the next time step are determined using migration and release terms, so as to obtain the changes in the concentrations of corrosion products deposited on each node and in the coolant through iterative simulation.

4. The simulation method for the migration-activation-deposition behavior of primary loop corrosion products in a pressurized water reactor according to claim 2, characterized in that, The coupled multi-node mass transport model corresponding to the non-radioactive corrosion products is as follows: ； In the formula, Let the mass of the corrosion products in node i be . Let be the coolant flow rate from node j to node i. Let J be the concentration of corrosion products in the coolant at node j. The corrosion release rate of the structural material within node i. The deposition rate of corrosion products within node i. Let be the re-release rate of sediment within node i.

5. The simulation method for the migration-activation-deposition behavior of primary loop corrosion products in a pressurized water reactor according to claim 4, characterized in that, The coupled multi-node mass transport model corresponding to the radioactive corrosion products is as follows: ； In the formula, Let i represent the activity of the radionuclide in node i. Let be the activity of the radionuclide in the coolant at node j. The decay constant is Let i be the number of nucleus atoms in node i. To activate the cross section, Let be the neutron flux at node i.

6. The simulation method for the migration-activation-deposition behavior of primary loop corrosion products in a pressurized water reactor according to claim 5, characterized in that, The release rate for: ； In the formula, Pre-exponential factor, For activation energy, The gas constant is For temperature, For the wetted area, This refers to the ion concentration in the coolant. The reaction order is [number]. Deposition rate for: ； In the formula, The mass transfer coefficient of sedimentation. This refers to the main concentration in the coolant. For material surface concentration, The deposition area is denoted as .

7. The simulation method for the migration-activation-deposition behavior of primary loop corrosion products in a pressurized water reactor according to claim 1, characterized in that, After coupling the migration, release, activation, decay, deposition, and re-release terms to establish a multi-node mass transport model describing the mass changes of corrosion products in each node, the model further includes: The corrosion product concentration of each node in the primary loop of the pressurized water reactor was obtained by simulating the corrosion product concentration of each node through a multi-node mass transport model, and a virtual pressurized water reactor primary loop was constructed based on the corrosion product concentration of each node obtained by simulation. Simulate gamma rays passing through multiple key measurement points in the primary loop of a virtual pressurized water reactor to obtain the corresponding dose rate; The simulated dose rate was compared with the actual measured dose rate, and the multi-node mass transport model was corrected based on the comparison results.

8. A device for simulating the migration, activation, and deposition behavior of corrosion products in the primary loop of a pressurized water reactor, characterized in that, The device includes: The loop partitioning module is used to divide the pressurized water reactor primary loop into multiple nodes; The migration simulation module is used to construct migration terms that describe the convection of corrosion products between nodes and the release of corrosion products into the coolant, based on the existence form and migration parameters of corrosion products in the primary coolant of the pressurized water reactor obtained through pre-designed migration tests. The activation simulation module is used to model the core structure in multiple nodes, simulate the neutron flux within the core structure, and construct activation terms and decay terms to describe the activation of corrosion products within the core structure due to neutron irradiation and the decay of activated products based on the neutron flux. The deposition simulation module is used to construct deposition terms that describe the deposition of corrosion products from coolant to nodes and the re-release terms that describe the re-release of corrosion products from nodes back into the coolant, based on the deposition and release parameters of corrosion products at each node obtained through pre-designed deposition experiments. The model building module is used to couple migration, release, activation, decay, deposition and re-release terms to establish a multi-node mass transport model to describe the mass changes of corrosion products in each node. The model simulation module is used to simulate the behavior of corrosion products at each node in the primary loop of a pressurized water reactor by migrating, releasing, activating, decaying, depositing, and re-releasing at each time step, as well as the behavior of deposited and re-released corrosion products in the next time step, through a multi-node mass transport model.

9. A computer device, characterized in that, include: At least one processor; And a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform a simulation method for the migration-activation-deposition behavior of pressurized water reactor primary circuit corrosion products as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements a simulation method for the migration-activation-deposition behavior of corrosion products in the primary loop of a pressurized water reactor as described in any one of claims 1 to 7.

Images