Zinc injection control method for primary loop of nuclear power plant

Abstract

The invention discloses a nuclear power plant primary loop zinc injection control method, and the method comprises the steps: carrying out sampling detection, determining that the detected primary loop water chemical parameters meet the thermal state function test zinc injection conditions, and preparing a zinc ion solution; monitoring the zinc ion concentration of the primary loop, filling the zinc ion solution and adjusting the adding rate; monitoring is carried out, and zinc injection is stopped when abnormal conditions occur; after passivation timing is finished, zinc injection is stopped before boronizing; the unit commercial operation zinc injection control method comprises the steps that sampling detection is carried out to determine that hydrochemical parameters meet unit commercial operation zinc injection conditions; monitoring the zinc ion concentration of the primary loop, and filling a zinc ion solution; and zinc injection is continued after abnormal conditions are processed, and zinc injection is stopped when the conditions are met. According to the invention, primary side stress corrosion cracking can be relieved, and the external radiation field of the reactor core and the collective dose during unit overhaul can be reduced.

Description

Technical Field

[0001] The present application belongs to the field of nuclear power technology and relates to a primary circuit water chemistry control method, and in particular to a primary circuit zinc injection control method for a nuclear power plant. Background Art

[0002] The corrosion products generated by the corrosion of the primary circuit equipment of a nuclear power plant migrate in the primary circuit with the flow of the reactor primary circuit coolant and deposit on the core surface. After being activated, the corrosion products deposited on the core surface migrate with the primary circuit coolant and deposit on the surface of the primary circuit equipment, thus forming hot spots and causing radioactive source items. During the overhaul, the equipment maintenance personnel in the reactor building were exposed to the radioactive hot spots, resulting in an increase in the collective dose. At the same time, it also caused stress corrosion cracking on the primary side. Summary of the invention

[0003] The technical problem to be solved by the present application is to provide a method for controlling zinc injection in the primary circuit of a nuclear power plant, which can alleviate stress corrosion cracking on the primary side and reduce the radiation field outside the core and the collective dose during the overhaul of the unit, in view of the above-mentioned defects of the prior art.

[0004] The technical solution adopted by the present application to solve the technical problem is: construct a zinc injection control method for a nuclear power plant primary circuit, including a hot function test zinc injection control method and / or a unit commercial operation zinc injection control method;

[0005] Wherein, the hot functional test zinc injection control method comprises the following steps:

[0006] R1. Take samples to test various water chemical parameters in the primary circuit, make sure that the water chemical parameters of the primary circuit tested meet the zinc injection conditions for the hot functional test, and prepare the zinc ion solution;

[0007] R2. Monitor the zinc ion concentration in the primary circuit, and add the zinc ion solution at different set addition rates according to the monitoring data of the zinc ion concentration in the primary circuit. During the addition process, adjust the addition rate according to the monitoring data;

[0008] R3. Monitor the concentration of silicon ions and aluminum ions in the primary circuit. When the concentration of silicon ions in the primary circuit is greater than 0.8 mg / kg or / and the concentration of aluminum in the primary circuit is greater than 1 mg / kg, it is an abnormal situation. Stop zinc injection. Continue zinc injection after resolving the abnormal situation.

[0009] R4. Stop zinc injection after the hot functional test passivation timing ends and 24 hours before boronization;

[0010] The commercial operation zinc injection control method of the unit comprises the following steps:

[0011] S1. Take samples to test various water chemical parameters in the primary circuit, and make sure that the water chemical parameters of the primary circuit tested meet the zinc injection conditions for commercial operation of the unit;

[0012] S2, monitoring the zinc ion concentration of the primary circuit, filling the zinc ion solution according to the addition rate set corresponding to the monitoring data of the zinc ion concentration of the primary circuit, and calculating the zinc loss amount of the purification circuit to determine the concentration of the zinc ion solution to be filled;

[0013] S3. Simultaneously monitor the concentrations of zinc ions, silicon ions, nickel ions and neutron flux diagram in the primary circuit. When any of the following situations occurs, it is considered an abnormal situation:

[0014] The zinc ion concentration in the first circuit is greater than 0.015 mg / kg;

[0015] The nickel ion concentration in the first circuit is greater than 0.006 mg / kg;

[0016] The silicon ion concentration in the first circuit is greater than 1.0 mg / kg;

[0017] The difference between the predicted axial power excursion and the measured axial power excursion exceeds ±3%;

[0018] Stop zinc injection if abnormal situation occurs, and continue zinc injection after dealing with the abnormal situation;

[0019] S4. End of zinc injection: 24 hours before unit shutdown.

[0020] Furthermore, in the primary-loop zinc injection control method for a nuclear power plant, preferably in step R1 or S1, the various water chemical parameters include primary-loop dissolved hydrogen concentration, primary-loop silicon ion concentration, primary-loop nickel ion concentration, primary-loop aluminum concentration, primary-loop calcium concentration and primary-loop magnesium concentration.

[0021] Furthermore, in the method for controlling zinc injection in the primary circuit of a nuclear power plant, preferably in step R1, the zinc injection conditions for the hot function test are:

[0022] The unit meets the following conditions at the same time:

[0023] The residual heat removal system is exited, and the primary circuit temperature is ≥177℃;

[0024] The concentration of dissolved hydrogen in the first circuit is >5mL / kg (STP);

[0025] The silicon ion concentration in the first circuit is less than 0.8 mg / kg;

[0026] The nickel ion concentration in the first circuit is less than 0.1 mg / kg;

[0027] The aluminum concentration in the primary circuit is less than 1 mg / kg;

[0028] The calcium concentration in the first circuit is less than 1 mg / kg;

[0029] The magnesium concentration in the primary circuit is less than 1 mg / kg.

[0030] Furthermore, in the method for controlling zinc injection in the primary circuit of a nuclear power plant, preferably in step R1, a zinc ion solution with a concentration of 1.8-2.0 g / L is prepared.

[0031] Furthermore, in the method for controlling zinc injection in the primary circuit of a nuclear power plant, preferably in step R2, the addition rate is:

[0032] When the zinc ion concentration in the primary circuit is ≤0.002 mg / kg, the zinc ion solution is injected into the primary circuit at an addition rate of 8-10 L / h, and the monitoring frequency is 1-2 times / 2h;

[0033] or / and, when 0.002 mg / kg<the zinc ion concentration of the primary circuit ≤ 0.05 mg / kg, inject zinc ion solution into the primary circuit at an addition rate of 5-9 L / h, and the monitoring time frequency is 1-2 times / 2h;

[0034] or / and, when 0.05 mg / kg<the zinc ion concentration of the primary circuit ≤ 0.08 mg / kg, inject zinc ion solution into the primary circuit at an addition rate of 2-5 L / h, and the monitoring time frequency is 1-2 times / 4h;

[0035] Or / and, when 0.08 mg / kg<the zinc ion concentration in the primary circuit ≤ 0.1 mg / kg, zinc ion solution is injected into the primary circuit at a rate of 1-2 L / h, and the monitoring frequency is 1-2 times / day.

[0036] Furthermore, in the method for controlling zinc injection in the primary circuit of a nuclear power plant, preferably in step R3, the abnormal situation is solved by exchanging water in the primary circuit, and when the monitored silicon ion concentration is less than 0.8 mg / kg and the aluminum concentration in the primary circuit is less than 1 mg / kg, the zinc injection conditions are met.

[0037] Furthermore, in the method for controlling zinc injection in the primary circuit of a nuclear power plant, preferably in step S1, the zinc injection condition for commercial operation of the unit is: zinc injection starts when the unit satisfies the following conditions at the same time:

[0038] The silicon ion concentration in the first circuit is less than 1.0 mg / kg;

[0039] The nickel ion concentration in the first circuit is less than 0.006 mg / kg;

[0040] After fuel risk assessment, there is no risk of core axial power distribution deviation.

[0041] Furthermore, in the method for controlling zinc injection in the primary circuit of a nuclear power plant, preferably in step S2, when the zinc ion concentration in the primary circuit is ≤0.002 mg / kg, a zinc ion solution is injected into the primary circuit at a concentration of 0.25 g / L and an addition rate of 0.2 L / h, and the monitoring time frequency is 1-3 times / day;

[0042] or / and, when the zinc ion concentration in the primary circuit is 0.002 mg / kg < ≤ 0.005 mg / kg, a zinc ion solution is injected into the primary circuit at a concentration of 0.625 g / L and an addition rate of 0.2 L / h, and the monitoring frequency is 1-3 times / day;

[0043] Or / and, when the zinc ion concentration in the primary circuit is 0.005 mg / kg < 0.015 mg / kg, zinc ion solution is injected into the primary circuit at a concentration of 1.875 g / L and an addition rate of 0.2 L / h, and the monitoring frequency is 1-2 times / day.

[0044] Furthermore, in the method for controlling zinc injection in the primary circuit of a nuclear power plant, preferably in step S3, abnormal situation processing is as follows: monitoring, analyzing and comparing corresponding zinc ion concentrations, silicon ion concentrations and nickel ion concentrations, confirming the analysis results, and then resampling, analyzing and comparing; confirming the zinc injection concentration and flow rate; or / and confirming the core parameters; or / and confirming the primary circuit makeup water quality parameters; or / and confirming the neutron flux measurement and corrosion product sampling; analyzing historical data to determine whether it is related to zinc injection.

[0045] Furthermore, in the method for controlling zinc injection in the primary circuit of a nuclear power plant, preferably in step S1, the fuel risk assessment includes an assessment of scale-induced axial power displacement and an assessment of scale-induced local corrosion.

[0046] The implementation of this application has the following beneficial effects:

[0047] The present application adopts the method of primary circuit zinc injection to form a denser oxide film on the surface of the primary circuit equipment, reduce the corrosion rate of the equipment, and alleviate stress corrosion cracking, thereby reducing the amount of corrosion products generated. The reduction in the amount of corrosion product generation means that the corrosion products deposited on the core surface due to the flow of the primary circuit coolant are reduced, thereby reducing the amount of activated corrosion products, reducing the source term of the unit, and thus reducing the collective dose.

[0048] And because the risks of zinc injection during the hot functional test and after the unit is put into commercial operation are different, the corresponding zinc addition strategies, prerequisites, and emergency plans are not exactly the same. This application can carry out zinc injection according to different periods, solving the requirements for zinc injection in different periods. During the period, the amount of zinc addition is adjusted according to the monitoring results of the primary water chemical parameters and the status of the unit. This application determines the prerequisites, zinc injection and dosing strategies and emergency plans for zinc injection of the unit during the hot functional test of the unit and after the unit is put into commercial operation, thereby providing technical guidance and operation plans for the subsequent application of zinc injection technology for the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work. In the drawings:

[0050] Figure 1a-1b is Zn in some embodiments of the present invention 2+ SEM photos of the treated samples;

[0051] Figure 2a-2d is Zn in some embodiments of the present invention 2+ STEM photo of the cross-section sample after treatment;

[0052] Figure 3a-3f is Zn in some embodiments of the present invention 2+ TEM image of the cross-section sample after treatment;

[0053] Figure 4a-4g is Zn in some embodiments of the present invention 2+ TEM-EDS images of the treated samples;

[0054] Figure 4h is Zn in some embodiments of the present invention 2+ Mass distribution diagram of O, Cr, Fe, Ni, and Zn after deducting Pt from the treated sample. DETAILED DESCRIPTION

[0055] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0056] A method for controlling zinc injection in a primary circuit of a nuclear power plant includes a method for controlling zinc injection in a hot functional test or / and a method for controlling zinc injection in a commercial operation of a unit; due to the different operating conditions and requirements of the hot functional test and the commercial operation of the unit, different control methods are adopted. Moreover, the control methods in the hot functional test and the commercial operation of the unit can be carried out independently or in coordination. The following is a detailed description of the two control methods:

[0057] Hot functional test is an important stage before the formal operation of nuclear power plants. Hot functional test is a comprehensive test of unit performance before loading. The main purpose is to conduct comprehensive inspection and verification of various systems and equipment of nuclear power plants under simulated actual operating conditions, and verify the reliability of nuclear island, conventional island equipment and systems during hot operation, and whether the relevant parameters meet the design requirements. Through hot functional test, it can ensure that nuclear power plants can work safely and reliably in actual operation, and lay a solid foundation for subsequent loading and commercial operation.

[0058] A 300-hour passivation time is required during the hot functional test. Therefore, in the hot functional test, passivation zinc injection is performed during the 300-hour passivation stage of hot operation to form a dense oxide film.

[0059] The hot function test zinc injection control method comprises the following steps:

[0060] R1. Take samples to test various water chemical parameters in the primary circuit, make sure that the water chemical parameters of the primary circuit tested meet the zinc injection conditions for the hot functional test, and prepare the zinc ion solution;

[0061] Specifically, the water chemical parameters sampled and tested include primary circuit dissolved hydrogen concentration, primary circuit silicon ion concentration, primary circuit nickel ion concentration, primary circuit aluminum concentration, primary circuit calcium concentration and primary circuit magnesium concentration. Primary circuit sampling and chemical testing is a routine project of nuclear power and will not be described here. After the test is completed, the test results are analyzed to determine whether they meet the zinc injection conditions for the hot functional test.

[0062] The hot functional test zinc injection conditions are:

[0063] The unit meets the following conditions at the same time:

[0064] 1) The waste heat removal system is exited, and the primary circuit temperature is ≥177℃;

[0065] 2) The concentration of dissolved hydrogen in the first circuit is >5mL / kg (STP); STP refers to the standard pressure of 100KPa and the standard temperature of 0℃

[0066] 3) The silicon ion concentration in the primary circuit is less than 0.8 mg / kg;

[0067] 4) The nickel ion concentration in the first circuit is less than 0.1 mg / kg;

[0068] 5) The aluminum concentration in the primary circuit is less than 1 mg / kg;

[0069] 6) The calcium concentration in the first circuit is less than 1 mg / kg;

[0070] 7) The magnesium concentration in the primary circuit is less than 1 mg / kg.

[0071] Zinc injection can only begin when all the above conditions are met.

[0072] If the test results do not meet the above conditions, water changes are required until the above requirements are met before zinc injection.

[0073] Before zinc injection, a zinc ion solution must be prepared, specifically using depleted zinc acetate dihydrate and water to prepare a zinc ion solution with a concentration of 1.8-2.0 g / L. Any zinc ion solution within this concentration range can be used, specifically 1.8, 1.85, 1.9, 1.95, 2.0 g / L.

[0074] R2. During the entire zinc injection process, it is necessary to monitor the zinc ion concentration in the first circuit, that is, to regularly sample and test the water in the first circuit, and obtain the monitoring data of the zinc ion concentration in the first circuit based on the sampling and test results. The zinc ion solution is injected at the corresponding different addition rates. During the injection process, the addition rate is adjusted according to the monitoring data.

[0075] Specifically, during the hot functional test, the expected value and limit of zinc concentration in the primary circuit are 0.05 mg / kg and 0.1 mg / kg respectively. That is, during the zinc injection process, the expected zinc concentration of 0.05 mg / kg is the preferred controlled concentration, and the limit of zinc concentration is 0.1 mg / kg, and the addition rate is controlled to avoid exceeding the above limit.

[0076] During the whole zinc injection process, different stages have different addition rates. The specific addition rates are as follows:

[0077] When the zinc ion concentration of the primary circuit is ≤0.002 mg / kg, the zinc ion solution is injected into the primary circuit at an addition rate of 8-10 L / h, and the monitoring time frequency is 1-2 times / 2h; according to the above addition rate, the daily zinc injection amount is 345.6-480 g;

[0078] When 0.002 mg / kg<the zinc ion concentration of the primary circuit≤0.05 mg / kg, the zinc ion solution is injected into the primary circuit at an addition rate of 5-9 L / h, and the monitoring time frequency is 1-2 times / 2h; according to the above addition rate, the daily zinc injection amount is 216-432 g;

[0079] When 0.05 mg / kg<the zinc ion concentration of the primary circuit≤0.08 mg / kg, the zinc ion solution is injected into the primary circuit at an addition rate of 2-5 L / h, and the monitoring time frequency is 1-2 times / 4h; according to the above addition rate, the daily zinc injection amount is 86.4-240 g;

[0080] When 0.08 mg / kg<primary circuit zinc ion concentration≤0.1 mg / kg, zinc ion solution is injected into the primary circuit at a rate of 1-2 L / h, and the monitoring frequency is 1-2 times / day; according to the above addition rate, the daily zinc injection amount is 43.2-96 g.

[0081] By selecting the above-mentioned different addition rates, at the initial stage of addition, the zinc ion concentration in the first circuit is very low. A higher addition rate can quickly reach the concentration requirement for deposition and quickly reach an equilibrium. Then, the equilibrium can be maintained and the addition rate can be gradually reduced.

[0082] R3. This step is a monitoring step and an abnormal situation handling step, that is, during the zinc injection process, if the concentrations of silicon ions and aluminum ions in the primary circuit are monitored, when the silicon ion concentration in the primary circuit is greater than 0.8 mg / kg or the aluminum concentration in the primary circuit is greater than 1 mg / kg, it is an abnormal situation and zinc injection is stopped. In the above abnormal situation, excessive silicon ion concentration in the primary circuit may cause the risk of zinc silicate deposition on the fuel surface, and excessive aluminum concentration may also cause primary circuit abnormality. The measures to solve the abnormal situation are: replace the water in the primary circuit until the concentrations of silicon ions and aluminum ions are all lower than the above concentration conditions, and then continue to inject zinc;

[0083] This step is for handling abnormal situations. If there is no abnormal situation, this step can be skipped.

[0084] R4. After the hot functional test passivation timing ends and 24 hours before boronization, stop zinc injection; the general passivation time is 300 hours. After passivation, it is followed by boronization. Since zinc injection forms an oxide film, it needs to be stopped before boronization. Therefore, it is recommended to stop zinc injection 24 hours before boronization.

[0085] The commercial operation zinc injection control method of the unit comprises the following steps:

[0086] S1. Sampling and testing various water chemical parameters in the primary circuit to determine whether the detected water chemical parameters of the primary circuit meet the conditions for zinc injection in commercial operation of the unit; in step S1, various water chemical parameters include primary circuit dissolved hydrogen concentration, primary circuit silicon ion concentration, primary circuit nickel ion concentration, primary circuit aluminum concentration, primary circuit calcium concentration and primary circuit magnesium concentration. After the various water chemical parameters are sampled on site, they are tested item by item to obtain parameter results.

[0087] The zinc injection conditions for commercial operation of the unit are: zinc injection starts when the unit meets the following conditions at the same time:

[0088] 1) The silicon ion concentration in the primary circuit is less than 1.0 mg / kg;

[0089] 2) The nickel ion concentration in the primary circuit is less than 0.006 mg / kg;

[0090] After fuel risk assessment, there is no risk of core axial power distribution deviation.

[0091] The fuel risk assessment specifically includes an assessment of scale-induced axial power deviation and an assessment of scale-induced localized corrosion.

[0092] Crud-induced power shift (CIPS) and crud-induced localized corrosion (CILC) are closely related to the safe operation of pressurized water reactors (PWRs). The oxidation corrosion products produced in the primary loop system of a PWR are deposited on the surface of the fuel rods under the action of supercooled boiling to form fuel fouling. These foulings not only contain metal oxides such as Ni, Fe, and Cr, but can also adsorb soluble boron in the coolant, thereby causing abnormal axial power shift of the core and affecting the safety and operation of the core. The neutron calculation model of the fuel fouling layer is established by the Monte Carlo method. Considering its strong neutron absorption effect and spatial self-screening effect, the calculation accuracy of different equivalent simulation methods of the fuel fouling layer can be evaluated, and the simulation method of fuel fouling can be determined. The impact of zinc injection in the primary loop on the risk of CIPS: zinc injection can reduce the total amount of fouling and the amount of boron precipitation, thereby reducing the risk of axial power shift caused by fouling.

[0093] Crud-Induced Localized Corrosion (CILC) refers to the corrosion products (also called dirt) released in the primary loop system of a pressurized water reactor (PWR) that are deposited on the surface of the fuel cladding, causing the local temperature of the fuel cladding surface to rise, thereby causing the cladding oxidation to accelerate, and in severe cases, leading to the corrosion failure of the fuel cladding. A large amount of dirt deposition can not only cause abnormal axial power deviation of the core, but also cause the local temperature of the fuel cladding surface to rise, thereby causing the cladding oxidation to accelerate. Fuel cladding scale-induced localized corrosion is one of the important reasons for the failure of fuel rods. PWR coolant parameters such as pH, dissolved hydrogen concentration, and dissolved oxygen concentration are key indicators of coolant chemical conditions. These parameters have a significant effect on the fouling on the surface of fuel elements. After zinc injection, the thickness of the inner oxide layer becomes thinner, forming a more protective ZnCr2O4, which slows down the early fouling deposition.

[0094] S2. Monitor the zinc ion concentration in the primary circuit, add zinc ion solution at the set addition rate according to the monitoring data of the zinc ion concentration in the primary circuit, calculate the zinc removal loss in the purification circuit, and determine the concentration of the added zinc ion solution; the expected value and limit value of the zinc concentration in the primary circuit are 0.008-0.012 mg / kg and 0.005-0.015 mg / kg, respectively. That is, when the unit is in commercial operation, during the zinc injection process, the expected value of zinc concentration of 0.008-0.012 mg / kg is used as the preferred range for control, and the limit values ​​of zinc concentration are the lower limit of 0.005 mg / kg and the upper limit of 0.015 mg / kg, respectively. The addition rate is controlled to avoid exceeding the above limit values.

[0095] The calculation of zinc loss in the purification circuit is used as a balance for zinc. The added zinc ions are equal to the zinc ions adsorbed on the surface of the primary circuit equipment + the zinc ions removed by the purification circuit. The zinc loss in the purification circuit is calculated based on the flow rate of the primary circuit purification downstream system and the zinc ion monitoring data. For example: the zinc ion monitoring data is 10μg / kg, and the purification flow rate is 13.6m 3 / h, the daily zinc injection amount (in terms of zinc) should be 10μg / kg×13.6m 3 / h×24h / d=3.264g / d.

[0096] According to the above requirements and monitoring results, the zinc ion addition rates are:

[0097] When the zinc ion concentration of the primary circuit is ≤0.002 mg / kg, a zinc ion solution is injected into the primary circuit at a concentration of 0.25 g / L and an addition rate of 0.2 L / h, and the monitoring time frequency is 1-3 times / day; the zinc injection process is basically a continuous process, and according to the above addition rate, the zinc injection amount is 1.2 g per day;

[0098] This step is the beginning of zinc injection. The zinc adding pump should be run continuously as much as possible to achieve zinc balance as soon as possible and gradually increase the zinc concentration in the first circuit to the desired value.

[0099] When the zinc ion concentration in the primary circuit is 0.002 mg / kg < ≤ 0.005 mg / kg, a zinc ion solution is injected into the primary circuit at a concentration of 0.625 g / L and an addition rate of 0.2 L / h, and the monitoring frequency is 1-3 times / day; according to the above addition rate, the daily zinc injection amount is 3 g;

[0100] When the zinc ion concentration in the first circuit is 0.005 mg / kg<≤0.015 mg / kg, zinc ion solution is injected into the first circuit at a concentration of 1.875 g / L and an addition rate of 0.2 L / h. The monitoring frequency is 1-2 times / day. According to the above addition rate, the daily zinc injection amount is 9 g.

[0101] S3. This step is a monitoring step and an abnormal situation handling step. During the unit operation and zinc injection process, the zinc ion, silicon ion, nickel ion concentration and neutron flux diagram in the primary circuit are monitored simultaneously. When any of the following situations occurs, it is determined to be an abnormal situation, and zinc injection is stopped. After the abnormal situation is handled, zinc injection is continued:

[0102] The zinc ion concentration in the first circuit is greater than 0.015 mg / kg;

[0103] The nickel ion concentration in the primary loop is greater than 0.006 mg / kg; among them, the increase in the nickel parameters in the primary loop may cause corrosion products to deposit on the core surface, causing the risk of local corrosion caused by fuel fouling.

[0104] The silicon ion concentration in the first loop is greater than 1.0 mg / kg; among them, the increase of silicon parameters in the first loop may lead to the risk of zinc silicate deposition on the fuel surface.

[0105] The difference between the predicted axial power excursion and the measured axial power excursion exceeds ±3%;

[0106] This step is for handling abnormal situations. If there are no abnormal situations, this step can be skipped.

[0107] Abnormal situation handling is: monitoring and analyzing the corresponding zinc ion concentration, silicon ion concentration, or nickel ion concentration, confirming the analysis results, and then re-sampling, analyzing and comparing; confirming the zinc injection concentration and flow rate; or / and confirming the core parameters; or / and confirming the primary loop water quality parameters; or / and confirming the neutron flux measurement and corrosion product sampling; analyzing historical data to determine whether it is related to zinc injection. The above analysis can be carried out independently or in full, depending on the actual situation.

[0108] Specifically, the abnormal situations and treatment measures of this step are as follows:

[0109] 1. When the zinc ion concentration in the first circuit is abnormal, that is, the zinc concentration in the first circuit exceeds 0.015 mg / kg, stop injecting zinc. Take the following measures:

[0110] 1) Confirm the analysis results of the previous steps;

[0111] 2) Resample and reanalyze, and compare with the previous analysis results to confirm whether there are any abnormalities in the analysis results and process;

[0112] 3) Confirm whether the concentration of the drug in the dosing box is correct;

[0113] 4) Confirm whether the desalting bed performance and purification flow are normal and whether the dosing flow is abnormal;

[0114] 5) Whether the dosing device operates normally;

[0115] After checking the above measures, find out the problem, solve it according to the problem, and resume normal zinc injection. 2. When the nickel ion concentration in the first circuit is abnormal, and the nickel ion concentration in the first circuit is greater than 0.006mg / kg, stop zinc injection and adjust the nickel sampling frequency to 3 times / week. And take the following measures:

[0116] 1) Confirm the analysis results of the previous steps;

[0117] 2) Resample, analyze, and compare with the previous analysis results to confirm whether there are any abnormalities in the analysis results and process;

[0118] 3) Confirm whether the dosing flow is abnormal;

[0119] 4) Confirm whether the core parameters are abnormal; core parameters include thermal and hydraulic parameters;

[0120] After checking the above measures, find out the problem, solve it according to the problem, and resume normal zinc injection. 3. When the silicon ion concentration in the first circuit is abnormal and exceeds 1.0 mg / kg, stop zinc injection, adjust the analysis frequency to once a week, and take the following measures:

[0121] 1) Confirm the analysis result data;

[0122] 2) Confirm the water quality parameters of the primary feed water loop; mainly including calcium ion, magnesium ion and silicon ion data.

[0123] 4. Neutron flux diagram: If the difference ΔAO between the predicted axial power offset (AO) and the measured axial power offset (AO) exceeds ±3%, CIPS is considered to have occurred and zinc injection is stopped; confirm neutron flux measurement and corrosion product sampling; analyze historical data to determine whether it is related to zinc injection.

[0124] After checking the above measures separately, find out the problem, solve it according to the problem, and resume normal zinc injection.

[0125] S4. End of zinc injection: 24 hours before the unit is shut down. When the unit needs to be shut down for overhaul, the zinc injection of the unit's commercial operation process is completed, and the zinc injection end time is 24 hours before the unit is shut down.

[0126] The following specific experiments are used to verify the implementation results of this application method:

[0127] During the hot functional test of the unit, a polished and surface-treated test piece is installed in the reactor and fixed with a special fixture. After the hot functional test, the test piece is taken out and FIB cross-section sample preparation, TEM, STEM and other characterization analyses are carried out. The sample body is 690TT.

[0128] 1. FIB cross-section sample preparation:

[0129] Figure 1a For the present application method, Zn 2+ Scanning electron microscope photo of the sample after treatment. After treatment, a uniform coating is formed on the surface of the material, and the coating looks smooth and flat, which is inferred to be composed of nanoparticles <1um. The rectangular area in the figure is about 8×1μm. This area was subjected to focused ion beam milling (FIB) and the cross-sectional sample was made from this area. Figure 1b This is the completed FIB cross-section sample. As can be seen from the picture: the cross-section is smooth and clear without any contamination.

[0130] 2. STEM characterization of FIB cross-section samples:

[0131] Figure 2a-2d Zn 2+ STEM photos of processed FIB cross-section samples at different magnifications (1μm, 500nm, 200nm, 100nm). Figure 2a , Figure 2b The photo in the middle is a lower magnification photo. It can be seen that the surface of the sample is covered with a nano-scale oxide film, and there is no underlying alloy exposed outside. Figure 2c , Figure 2d From the photos taken at higher magnifications, it can be seen that the thickness of the oxide film ranges from 30 to 80 nm, and the continuity and uniformity of the surface oxide film are good.

[0132] 3. TEM characterization of FIB cross-section samples:

[0133] Figure 3a-3f Figure 2 is a transmission electron microscope photo of a FIB cross-section sample at different magnifications. The TEM mode is used to observe the particle size and morphology of the surface film. Figure 3a , Figure 3b The middle is a low-magnification photo (2μm, 500nm), which clearly shows that the surface of the sample is covered with a continuous oxide film. The particle size and morphology of the oxide film are significantly different from the alloy structure of the main body. Figure 3c , Figure 3d These are medium magnification photos (200nm, 100nm), showing that the surface film is formed by dense accumulation of spherical or nearly spherical nanoparticles, and the particle size is generally less than 100nm. Figure 3e and Figure 3f The middle is a high-magnification photo (20nm, 10nm), which clearly shows that the nanoparticles in the surface film have good crystallinity. Figure 3e and Figure 3f Obvious lattice fringes were observed in the ZnO2 film. In addition, the oxide film and the alloy body were closely bonded, and no obvious gaps were found. This phenomenon further proves that after ZnO22+ Treatment can form an oxide film in situ on the surface of the sample to prevent continued oxidation and corrosion of the sample.

[0134] 4. TEM-EDS scan of FIB cross-section sample:

[0135] An area was selected for TEM-EDS scanning of the cross-section sample. Figure 4a The representative sample area was selected. Figure 4b-4g They are the distribution of Zn, O, Fe, Cr, Ni and Pt elements in the entire plane, represented by green, light blue, purple, yellow, orange and blue respectively. Figure 4b In the samples, Zn element was obviously enriched on the surface. In addition to the surface enriched Zn, Zn element signals were also found in other parts of the sample. This is because the Zn content in the sample is too low (0.3%, Figure 4h ), the influence of noise is greater. Similar to Zn element, Figure 4c It can be seen that oxygen is also enriched on the surface, which is consistent with the location where the surface film is formed. Figure 4d-4f As shown in the figure, Fe, Cr and Ni are the main components of the bulk 690 alloy, which are evenly distributed in the bulk of the sample. Among them, there are some single-phase particles of Cr, which do not form an alloy phase with Fe and Ni. Figure 4g As shown, no Pt element was observed in the bulk and surface of the sample, but more Pt appeared on the sample. Figure 4h This is the mass distribution of O, Cr, Fe, Ni, and Zn after deducting Pt. O and Zn are mostly present in the surface layer, with a total content of about 0.5% and 0.3%. The mass contents of Cr, Fe, and Ni are 28.6%, 10.6%, and 60%, which are consistent with the main metal element contents of 690 alloy.

[0136] In summary, the present application adopts the method of primary circuit zinc injection, which not only forms a denser oxide film on the surface of the primary circuit equipment during the hot functional test, but also continues to inject zinc after the unit is put into commercial operation, maintaining the primary circuit zinc ion equilibrium state, reducing the equipment corrosion rate, and relieving stress corrosion cracking, thereby reducing the amount of corrosion products generated. The reduction in the amount of corrosion product generation means that the corrosion products deposited on the core surface with the flow of the primary circuit coolant are reduced, thereby reducing the amount of activated corrosion products, reducing the unit source term, and thus reducing the collective dose.

[0137] It can be understood that the above embodiments only express the preferred implementation methods of the present application, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present application; it should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, the above-mentioned technical features can be freely combined, and several deformations and improvements can be made, which all belong to the protection scope of the present application; therefore, all equivalent changes and modifications made to the scope of the claims of the present application should fall within the scope of the claims of the present application.

Claims

1. A method for controlling zinc injection in a primary circuit of a nuclear power plant, characterized in that: Including hot function test zinc injection control method and / or unit commercial operation zinc injection control method; Wherein, the hot functional test zinc injection control method comprises the following steps: R1. Take samples to test various water chemical parameters in the primary circuit, make sure that the water chemical parameters of the primary circuit tested meet the zinc injection conditions for the hot functional test, and prepare the zinc ion solution; R2. Monitor the zinc ion concentration in the primary circuit, and add the zinc ion solution at different set addition rates according to the monitoring data of the zinc ion concentration in the primary circuit. During the addition process, adjust the addition rate according to the monitoring data; R3. Monitor the concentration of silicon ions and aluminum ions in the primary circuit. When the concentration of silicon ions in the primary circuit is greater than 0.8 mg / kg or / and the concentration of aluminum in the primary circuit is greater than 1 mg / kg, it is an abnormal situation. Stop zinc injection. Continue zinc injection after resolving the abnormal situation. R4. Stop zinc injection after the hot functional test passivation timing ends and 24 hours before boronization; The commercial operation zinc injection control method of the unit comprises the following steps: S1. Take samples to test various water chemical parameters in the primary circuit, and make sure that the water chemical parameters of the primary circuit tested meet the zinc injection conditions for commercial operation of the unit; S2, monitoring the zinc ion concentration of the primary circuit, filling the zinc ion solution according to the addition rate set corresponding to the monitoring data of the zinc ion concentration of the primary circuit, and calculating the zinc loss amount of the purification circuit to determine the concentration of the zinc ion solution to be filled; S3. Simultaneously monitor the concentrations of zinc ions, silicon ions, nickel ions and neutron flux diagram in the primary circuit. When any of the following situations occurs, it is considered an abnormal situation: The zinc ion concentration in the first circuit is greater than 0.015 mg / kg; The nickel ion concentration in the first circuit is greater than 0.006 mg / kg; The silicon ion concentration in the first circuit is greater than 1.0 mg / kg; The difference between the predicted axial power excursion and the measured axial power excursion exceeds ±3%; Stop zinc injection if abnormal situation occurs, and continue zinc injection after dealing with the abnormal situation; S4. End of zinc injection: 24 hours before unit shutdown.

2. The method for controlling zinc injection in the primary circuit of a nuclear power plant according to claim 1, characterized in that: In the step R1 or S1, the various water chemical parameters include a first-loop dissolved hydrogen concentration, a first-loop silicon ion concentration, a first-loop nickel ion concentration, a first-loop aluminum concentration, a first-loop calcium concentration and a first-loop magnesium concentration.

3. The method for controlling zinc injection in the primary circuit of a nuclear power plant according to claim 1, characterized in that: In step R1, the hot functional test zinc injection conditions are: The unit meets the following conditions at the same time: The residual heat removal system is exited, and the primary circuit temperature is ≥177℃; The concentration of dissolved hydrogen in the first circuit is >5mL / kg; The silicon ion concentration in the first circuit is less than 0.8 mg / kg; The nickel ion concentration in the first circuit is less than 0.1 mg / kg; The aluminum concentration in the primary circuit is less than 1 mg / kg; The calcium concentration in the first circuit is less than 1 mg / kg; The magnesium concentration in the primary circuit is less than 1 mg / kg.

4. The method for controlling zinc injection in the primary circuit of a nuclear power plant according to claim 1, characterized in that: In the step R1, a zinc ion solution with a concentration of 1.8-2.0 g / L is prepared.

5. The method for controlling zinc injection in the primary circuit of a nuclear power plant according to claim 1, characterized in that: In step R2, the addition rate is: When the zinc ion concentration in the primary circuit is ≤0.002 mg / kg, the zinc ion solution is injected into the primary circuit at an addition rate of 8-10 L / h, and the monitoring frequency is 1-2 times / 2h; or / and, when 0.002 mg / kg<the zinc ion concentration of the primary circuit ≤ 0.05 mg / kg, inject zinc ion solution into the primary circuit at an addition rate of 5-9 L / h, and the monitoring time frequency is 1-2 times / 2h; or / and, when 0.05 mg / kg<the zinc ion concentration of the primary circuit ≤ 0.08 mg / kg, inject zinc ion solution into the primary circuit at an addition rate of 2-5 L / h, and the monitoring time frequency is 1-2 times / 4h; Or / and, when 0.08 mg / kg<the zinc ion concentration in the primary circuit ≤ 0.1 mg / kg, zinc ion solution is injected into the primary circuit at a rate of 1-2 L / h, and the monitoring frequency is 1-2 times / day.

6. The method for controlling zinc injection in the primary circuit of a nuclear power plant according to claim 1, characterized in that: In step R3, the abnormal situation is solved by replacing water in the first circuit, and when the silicon ion concentration is monitored to be less than 0.8 mg / kg and the aluminum concentration in the first circuit is less than 1 mg / kg, the zinc injection conditions are met.

7. The method for controlling zinc injection in the primary circuit of a nuclear power plant according to claim 1, characterized in that: In step S1, the zinc injection condition for commercial operation of the unit is: zinc injection starts when the unit meets the following conditions at the same time: The silicon ion concentration in the first circuit is less than 1.0 mg / kg; The nickel ion concentration in the first circuit is less than 0.006 mg / kg; After fuel risk assessment, there is no risk of core axial power distribution deviation.

8. The method for controlling zinc injection in the primary circuit of a nuclear power plant according to claim 1, characterized in that: In the step S2, when the zinc ion concentration of the primary circuit is ≤0.002 mg / kg, a zinc ion solution is injected into the primary circuit at a concentration of 0.25 g / L and an addition rate of 0.2 L / h, and the monitoring time frequency is 1-3 times / day; or / and, when the zinc ion concentration in the primary circuit is 0.002 mg / kg < ≤ 0.005 mg / kg, a zinc ion solution is injected into the primary circuit at a concentration of 0.625 g / L and an addition rate of 0.2 L / h, and the monitoring frequency is 1-3 times / day; Or / and, when the zinc ion concentration in the primary circuit is 0.005 mg / kg < 0.015 mg / kg, zinc ion solution is injected into the primary circuit at a concentration of 1.875 g / L and an addition rate of 0.2 L / h, and the monitoring frequency is 1-2 times / day.

9. The method for controlling zinc injection in the primary circuit of a nuclear power plant according to claim 1, characterized in that: In step S3, the abnormal situation is handled as follows: monitoring, analyzing and comparing the corresponding zinc ion concentration, silicon ion concentration and nickel ion concentration, confirming the analysis results, and then resampling, analyzing and comparing; confirming the zinc injection concentration and flow rate; or / and confirming the core parameters; or / and confirming the primary loop water quality parameters; Or / and confirm neutron flux measurement and corrosion product sampling; analyze historical data to determine whether it is related to zinc injection.

10. The method for controlling zinc injection in the primary circuit of a nuclear power plant according to claim 7, characterized in that: In the step S1, the fuel risk assessment includes an assessment of scale-induced axial power deviation and an assessment of scale-induced localized corrosion.

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