Method for measuring thermodynamic parameters of corrosion product under zinc injection

Abstract

The invention relates to a method for measuring thermodynamic parameters of a corrosion product under zinc injection, which comprises the following steps: detecting the characteristic peak position of the corrosion product through Raman spectrum, comparing with a standard Raman spectrum database to obtain the chemical structure of the corrosion product, calibrating the peak intensity of a standard sample, and obtaining the concentration of the corrosion product according to the relationship between the peak intensity and the concentration of the standard sample. The conductivity of the coolant containing the corrosion product is detected through alternating current conductivity, and the ionization constant of the corrosion product is obtained in combination with concentration information provided by the Raman spectrum. According to the invention, the thermodynamic parameters of the corrosion product under the chemical condition of zinc injection water can be measured in situ, including the chemical structure, concentration and equilibrium constant of the corrosion product, and the problem of lack of the thermodynamic parameters of the corrosion product under the current chemical condition of zinc injection water is solved; and a foundation is laid for accurate prediction of the corrosion product deposition law and model development under the zinc injection water chemical condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reactor control, and particularly relates to a method for measuring thermodynamic parameters of corrosion products under zinc injection. BACKGROUND

[0002] Due to the limitation of existing experimental techniques, the thermodynamic parameters of corrosion products under the water chemical condition of zinc injection are currently calculated by the Helgeson-Kirkham-Flowers (HKF) model and the Pitzer formula, but the standard partial molar Gibbs free energy parameters of Fe, Ni and Zn components under the operating conditions of a pressurized water reactor loop are missing in the HKF model, so that the Gibbs free energy change and the equilibrium constant of various chemical reactions involving the corrosion products in the primary loop cannot be accurately calculated, and the HKF model does not have the ability to analyze the structure and concentration balance, the conductivity, and the in-situ adaptability under high temperature and high pressure. SUMMARY

[0003] The present application provides a method for measuring thermodynamic parameters of corrosion products under zinc injection, which can measure the thermodynamic parameters of corrosion products under the water chemical condition of zinc injection in-situ, including the chemical structure, concentration and equilibrium constant of the corrosion products, solves the problem of the lack of thermodynamic parameters of corrosion products under the water chemical condition of zinc injection, and lays a foundation for accurately predicting the deposition rule of corrosion products under the water chemical condition of zinc injection and developing a model.

[0004] The present application is implemented by the following technical solutions:

[0005] The present application relates to a method for measuring thermodynamic parameters of corrosion products under zinc injection, which compares the characteristic peak position of the corrosion products detected by Raman spectroscopy with a standard Raman spectroscopy database to obtain the chemical structure of the corrosion products and calibrate the peak intensity of the standard sample, and then obtains the concentration of the corrosion products according to the relationship between the standard sample peak intensity and the concentration. The conductivity of the coolant containing the corrosion products is detected by alternating current conductivity, and the ionization constant of the corrosion products is obtained in combination with the concentration information provided by the Raman spectroscopy.

[0006] The present application relates to a kind of corrosion product thermodynamic parameter measurement system for realizing above-mentioned method, including: Raman detection unit, concentration analysis unit, conductivity measurement unit and ionization constant calculation unit, wherein: Raman detection unit extracts the characteristic peak of corrosion product according to the Raman spectrum information of the coolant sample to be measured, obtains the chemical structure information of corrosion product by comparing standard Raman spectrum database and carrying out spectrum identification process;Concentration analysis unit obtains the quantitative concentration of target corrosion product by carrying out concentration inversion process in combination with the concentration-peak intensity relationship curve of standard sample calibrated in advance according to the characteristic peak intensity information provided by Raman detection unit;Conductivity measurement unit obtains the total conductivity of coolant system by carrying out conductivity response analysis process according to the alternating current conductivity signal of corrosion product-containing coolant;Ionization constant calculation unit obtains the ionization constant of target corrosion product by establishing ion dissociation equilibrium model through thermodynamic inversion process according to the corrosion product concentration information provided by concentration analysis unit and the total conductivity data provided by conductivity measurement unit.

[0007] Technical effects

[0008] The present application combines Raman spectrum and alternating current conductivity to detect the thermodynamic parameters of corrosion product in coolant under the condition of zinc injection of pressurized water reactor;The quantitative relationship between Raman characteristic peak and corrosion product concentration is established by combining standard sample calibration curve, which solves the problem that corrosion product concentration cannot be accurately identified;The ionization constant of corrosion product is inversely deduced by linking conductivity and Raman concentration analysis, and the key thermodynamic data of pressurized water reactor primary loop water chemistry is formed.Compared with prior art, the present application can identify the type of corrosion product in coolant, measure concentration and evaluate ionization behavior, information is comprehensive, and measurement efficiency and accuracy are improved;It can be used for online or in-situ detection, avoids the error caused by cooling and transfer of pressurized water reactor coolant, is more suitable for actual application requirements under high temperature and high pressure, and the detection system structure is simple, measurement is fast, the behavior change of corrosion product can be dynamically evaluated, which helps to assist in formulating pressurized water reactor primary loop water chemistry control strategy. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 It is the structure schematic diagram / flow chart of the present application;

[0010] Figure 2 It is the Raman characteristic peak position and peak intensity of zinc-free corrosion product;

[0011] Figure 3 It is the Raman characteristic peak position and peak intensity diagram of zinc injection corrosion product. DETAILED DESCRIPTION

[0012] As Figure 1 Shown, it is a kind of corrosion product thermodynamic parameter measurement method under zinc injection involved in the present embodiment, specifically including:

[0013] Step 1: After measuring the characteristic peak position and peak intensity of the corrosion product by Raman spectroscopy, the change of the type and concentration of the corrosion product under the zinc injection water chemistry is determined by comparing the relationship between the peak intensity and concentration of the standard sample.

[0014] The Raman spectroscopy measurement refers to: when the laser irradiates, the molecules / ions undergo inelastic scattering, the frequency change of the scattered light reflects the Raman activity of the specific chemical bond or molecular structure, the Raman scattered light is received by the CCD (charge coupled device) detector after filtering the stray light and the light signal is converted into an electrical signal, which is processed by signal amplification and analog-to-digital conversion (A / D) and then enters the spectrum processing module, and finally the characteristic peak position and intensity of the Raman spectrum are output.

[0015] As shown in Figure 2 and 3 , the abscissa wavelength corresponds to the characteristic peak position of the corrosion product, and the ordinate corresponds to the characteristic peak intensity of the corrosion product. By comparing the standard Raman spectrum database, the chemical structure of the corrosion product corresponding to the Raman characteristic peak position in Figure 2 and Figure 3 is obtained, and the change of the chemical structure of the corrosion product under the zinc injection water chemistry is determined by comparison.

[0016] Step 2, the conductivity probe measures the alternating current conductivity of the corrosion product, specifically including:

[0017] 2.1 The alternating current conductivity technology measurement is based on the change of the number of mobile ions and the conductivity in the solution system due to ionization reaction. The hydrolysis and ionization of the corrosion product under the zinc injection water chemistry will cause the change of the number of mobile ions in the solution, which is characterized by the change of the real part and the imaginary part of the solution resistivity under the zinc injection corrosion product, specifically: , wherein: the real part of the solution resistance , the alternating current angular frequency, the resistance of the solution, and are fitting parameters.

[0018] 2.2 The conductivity of the solution is obtained according to the resistance of the solution , wherein: is the conductivity of the standard solution; when calculating the conductivity of the corrosion product solution under the zinc injection water chemistry, the ionization effect of the solution water is further considered, specifically: , according to the theoretical conductivity equation, the equivalent conductivity of the solution , wherein: the equivalent concentration , C is the molar concentration, and Z is the ion charge.

[0019] 2.3 For the ionization reaction A - +B + AB, the ionization equilibrium constant , according to the mass conservation, , wherein: C= is the initial corrosion product concentration, is the dissolved fraction. The ionization equilibrium constant can be further expressed as wherein: is the average activity coefficient of the ion pair, is the average activity coefficient of the corrosion product.

[0020] 2.4 Expressing the equivalent conductivity of the solution by the dissolved fraction wherein: the total conductivity of the free ions i (determined by the corrosion product chemical structure) , , is the ion equivalent conductivity of the infinitely diluted solution, and are the electrophoretic correction considering the free ions and the relaxation effect of the free ions, respectively.

[0021] 2.5 The expression that can be shown according to the above steps to obtain the dissolved fraction ; according to the corrosion product chemical structure and concentration obtained by Raman spectrum and the corrosion product solution conductivity obtained by alternating conductivity, the average activity coefficient of the chemical structure corrosion product ion pair and the average activity coefficient of the corrosion product are calculated by iterative execution of steps 2.3-2.5, and finally the ionization equilibrium constant K is obtained.

[0022] Through specific actual experiments, Raman spectrum measurement of corrosion products in pressurized water reactor coolant was carried out under the conditions of no zinc injection and zinc injection, and alternating conductivity was recorded synchronously during the experiment to assist in judging the ionization behavior of the corrosion products, as follows:

[0023] As shown in Figure 2 , the Raman spectrum measured in the coolant system without adding zinc ions is shown. It can be seen from the figure that the main characteristic peak intensity of the corrosion product is low and the peak shape is wide, indicating that in the absence of zinc, the corrosion product coexists in multiple low stability coordination structures, and the proportion of free ions in the system is relatively high. The alternating conductivity measurement results show that the conductivity increases nonlinearly with the concentration at this stage, indicating that the corrosion product does not form a stable complex structure.

[0024] As shown in Figure 3 , the Raman spectrum measured after injecting a certain concentration of zinc ions into the system is shown. Compared with Figure 2, multiple characteristic peaks (e.g. ~750 cm⁻¹ and ~860 cm⁻¹) were significantly enhanced, and the spectrum shape was more clear and sharp, which indicated that the introduction of zinc ions promoted the formation of more stable coordination complexes of corrosion products. The synchronous measurement of alternating current conductivity showed that the overall ion mobility of the system decreased, and the free ion concentration decreased, which verified the regulation effect of zinc on the corrosion product complexation-precipitation equilibrium.

[0025] Compared with the prior art, the method can obtain the changes of the chemical structure and concentration of the corrosion products and the ionization equilibrium constant of the corrosion products under the zinc injection water chemical condition.

[0026] The above specific embodiments can be adjusted in different ways by those skilled in the art without departing from the principles and purposes of the present application, the protection scope of the present application is subject to the claims and is not limited by the above specific embodiments, and each implementation scheme within the scope is subject to the present application.

Claims

1. A method for measuring the thermodynamic parameters of corrosion products under zinc injection, characterized in that, After detecting the characteristic peak positions of the corrosion products by Raman spectroscopy, the chemical structure of the corrosion products is obtained by comparing with the standard Raman spectroscopy database to calibrate the peak intensity of the standard sample. Then, the concentration of the corrosion products is obtained based on the relationship between the peak intensity and concentration of the standard sample. The conductivity of the coolant containing the corrosion products is detected by AC conductivity. Combined with the concentration information provided by Raman spectroscopy, the ionization constant of the corrosion products is obtained.

2. The method for measuring the thermodynamic parameters of corrosion products under zinc injection according to claim 1, characterized in that, The characteristic peak positions of the corrosion products are detected in the following way: When irradiated by laser, molecules / ions undergo inelastic scattering. The change in the frequency of the scattered light reflects the Raman activity of specific chemical bonds. After the Raman scattered light is filtered to remove stray light, it is passed through a CCD (charge-coupled device) detector, a signal amplification and analog-to-digital conversion (A / D) module, and a spectral processing model to complete photoelectric signal conversion, signal amplification and analog-to-digital conversion, and spectral analysis, and finally outputs the characteristic peak positions and intensities of the Raman spectrum.

3. The method for measuring the thermodynamic parameters of corrosion products under zinc injection according to claim 1, characterized in that, The AC conductivity of the corrosion products was detected by the following method: 3.1 AC conductivity measurement is based on the principle that ionization reactions alter the number of migratable ions and conductivity in a solution system. Under zinc injection hydration chemistry conditions, the hydrolysis and ionization of corrosion products cause changes in the number of migratable ions in the solution, which are characterized by changes in the real and imaginary parts of the resistivity of the zinc injection corrosion product solution. Specifically: Where: the real resistance of the solution , Alternating current angular frequency, The resistance of the solution and All are fitted parameters; 3.2 Obtaining the conductivity of a solution based on its resistance. ,in: The conductivity is that of the standard solution. When calculating the conductivity of the solution containing the chemical corrosion products of zinc injection water, the effect of water ionization in the solution is further considered, specifically: According to the theoretical conductivity equation, the equivalent conductivity of the solution is... Where: equivalent concentration C is the molar concentration, and Z is the ionic charge; 3.3 Ionization reaction of corrosion products A - +B + AB, its ionization equilibrium constant According to the law of conservation of mass, , Where: C= The initial concentration of corrosion products. The dissolution fraction; the ionization equilibrium constant can be further expressed as ,in: The average activity coefficient of the ion pair. The average activity coefficient of the corrosion products; 3.4 The equivalent conductivity of the solution is expressed using the solubility fraction. Wherein: the total conductivity of free ion i (determined by the chemical structure of corrosion products) , , The ionic equivalent conductivity of the infinitely diluted solution. and These are considered in relation to the electrophoretic correction of free ions and the relaxation effect of free ions, respectively. 3.5 The dissolved fraction obtained according to the above steps can be displayed. Based on the chemical structure and concentration of the corrosion products obtained from Raman spectroscopy and the conductivity of the corrosion product solution obtained from AC conductivity, the average activity coefficient of the chemical structure corrosion product ion pairs and the average activity coefficient of the corrosion products are calculated by iteratively executing steps 3.3-3.5, and finally the ionization equilibrium constant K is obtained.

4. A system for measuring the thermodynamic parameters of corrosion products according to any one of claims 1-3, comprising: The system comprises a Raman detection unit, a concentration analysis unit, a conductivity measurement unit, and an ionization constant calculation unit. Specifically: the Raman detection unit extracts the characteristic peak positions of corrosion products based on the Raman spectrum information of the coolant sample, and performs spectral identification processing by comparing it with a standard Raman spectral database to obtain the chemical structure information of the corrosion products; the concentration analysis unit performs concentration inversion processing based on the characteristic peak intensity information provided by the Raman detection unit, combined with a pre-calibrated standard sample concentration-peak intensity relationship curve, to obtain the quantitative concentration of the target corrosion product; the conductivity measurement unit performs conductivity response analysis processing based on the AC conductivity signal of the coolant containing corrosion products to obtain the total conductivity of the coolant system; and the ionization constant calculation unit performs thermodynamic inversion processing based on the corrosion product concentration information provided by the concentration analysis unit and the total conductivity data provided by the conductivity measurement unit, establishes an ion dissociation equilibrium model, and obtains the ionization constant of the target corrosion product.

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