Regulation of water vapor circuits of light and heavy water reactors

Abstract

The present invention relates to a method for dynamically controlling corrosion in a steam-water circuit of a nuclear power plant, the method comprising: injecting a compound ethanolamine and optionally ammonia, the system comprising: an injection unit located at a feed point and configured for injecting the compound ethanolamine and ammonia in a fluid circulating in the circuit; and a measurement unit configured for measuring in the loop a parameter pH value and at least one parameter selected from the group consisting of an oxidation-reduction potential and a corrosion potential; the system is characterized in that it further comprises a control unit comprising: a first acquisition module connected to the measurement unit, configured for acquiring a measured value of the parameter, and configured for acquiring at least one setpoint value of said parameter; a command module, connected to the injection unit, configured for commanding the injection of the compounds ethanolamine and ammonia through the injection unit according to at least one setpoint value and a measured value of the acquired parameter, characterized in that ethanolamine is used as a reducing agent. The invention also relates to a system for dynamically controlling corrosion in a steam-water circuit of a nuclear power plant.

Description

Technical Field

[0001] This invention relates to a method and system for dynamically controlling corrosion in the steam-water circuit of a nuclear power plant. Background Technology

[0002] Nuclear power plants are known to include a main coolant loop and a separate steam-water loop. They operate specifically as pressurized water reactors or heavy water reactors. Due to their construction and the materials used, the steam generators of nuclear power plants must operate under reducing conditions to maintain low oxygen concentrations and thus prevent corrosion. Even during plant shutdowns, it is necessary to adjust reducing conditions to protect the sensitive materials on the second side of the steam generator from corrosion. This is also known as shutdown preservation.

[0003] To establish reducing conditions, hydrazine, methanol, or carbonyl hydrazine can be used as reducing agents in the steam-water loop of a nuclear power plant.

[0004] During the electrical operation of a nuclear power plant, for example in the steam-water circuit, hydrazine can cause the following reaction:

[0005] Oxygen is removed through the reaction N₂H₄ + O₂ → N₂ + 2H₂O. The removal of the oxidizing agent O₂, and, if applicable, other oxidizing agents (such as copper ions), facilitates the setting of reduction conditions.

[0006] Reduction conditions were established by additional electrochemical hydrazine oxidation on the component surface according to the reaction N₂H₄ + 4OH⁻ --> N₂ + 4H₂O + 4e⁻. Under standard conditions, the equilibrium electrode potential for this reaction was -330 mV at room temperature relative to the hydrogen electrode.

[0007] The reaction with hydrazine is thermally activated, causing a gradual shift from oxidizing conditions in the condensate and feedwater systems of both light and heavy water reactors to reducing conditions. Hydrazine reacts at a high rate as the feedwater enters the steam generator and circulates in the second side of the steam generator, thus ensuring reducing conditions.

[0008] In power plants operating on conventional energy sources, a small amount of oxygen is used to establish specific oxidation conditions in the condensate and feedwater systems. This is done to reduce iron release from components and also to reduce the introduction of corrosion products into the steam boiler.

[0009] For this reason, the VGB standard (VGB-S-010-T-00; 2011-12.DE) for the quality of feed water, boiler water, and steam in industrial power plants recommends only AVT(O) (oxidizing total volatile treatment) operation mode in specific AVT operating modes, where only ammonia is used for conditioning without the addition of any reducing agent. According to this standard, AVT(R) (reducing total volatile treatment) operation mode, which adds additional volatile reducing agents as oxygen scavengers, should only be used in special circumstances.

[0010] Hydrazine is an excellent oxygen scavenger. Therefore, the known operation of the secondary steam-water loop in a pressurized water reactor with hydrazine added as a reducing agent corresponds to the AVT(R) operating mode. Precise regulation of the oxygen content in the loop system is impossible in a hydrazine-containing medium, thus AVT(O) regulation of the steam-water loop system in both light and heavy water reactors is not possible. Furthermore, hydrazine, as a strong reducing agent, can enhance erosion and corrosion in the loop system.

[0011] Some plants avoid using hydrazine by using less toxic carbonyl hydrazine or methanol; however, the use of ethanolamine as a reducing agent in the steam-water loop of nuclear power plants has not been described or demonstrated in the prior art.

[0012] CN 111362388 discloses a synergistic pH control method using ethanolamine and ammonia in a dual-loop thermodynamic system of a nuclear power plant to meet the pH requirement of 9.0 to 9.8 for the dual-loop thermodynamic system. Therefore, it effectively increases the pH value of the dual-loop thermodynamic system, achieves equilibrium control, significantly reduces the iron content of the dual-loop thermodynamic system, improves the corrosion conditions of the dual-loop thermodynamic system, reduces corrosion of equipment in the dual-loop thermodynamic system, and reduces the transport and deposition of corrosion products to the steam generator. Ammonia and ethanolamine are used to establish the desired pH value, and their concentrations and pH are monitored.

[0013] EP 3 654 350 discloses a method for controlling the corrosion rate of coolant loop equipment in a nuclear power plant using a corrosion inhibitor, wherein hydrazine is used as a reducing agent and a combination of ammonia and organic amines (e.g., ethanolamine) is used as an alkalizing agent to establish the desired pH value.

[0014] DE 10 2015 120 722 discloses a nuclear power plant comprising a main coolant circuit and a separate steam / water circuit, wherein a reducing agent (preferably methanol) containing carbon, oxygen, and hydrogen, other than hydrazine, is introduced into the secondary steam / water circuit. The document only uses ethanolamine as an alkalizing agent.

[0015] The purpose of this invention is to provide effective, user-friendly and non-toxic corrosion protection in the secondary steam-water loop of nuclear power plants (especially pressurized water reactors or heavy water reactors). Summary of the Invention

[0016] To address this objective, the present invention relates to a method for dynamically controlling corrosion in a steam-water circuit of a nuclear power plant, the method comprising:

[0017] - Using an injection unit, the compounds ethanolamine and optionally ammonia are injected into the fluid circulating in the loop; and

[0018] - Use a measurement unit to measure the parameters pH and at least one parameter selected from redox potential and corrosion potential in the loop;

[0019] - Use the acquisition module connected to the measurement unit to acquire the measured value of the parameter;

[0020] - Use the acquisition module to acquire at least one setpoint value of the parameter;

[0021] - Using a command module connected to the injection unit, based on at least one setpoint value and measured value of the acquired parameters, a command is given to inject the compound ethanolamine and optionally ammonia via the feed point through the injection unit.

[0022] Its characteristic feature is that ethanolamine is used as a reducing agent.

[0023] Preferably, the command to inject ethanolamine and optional ammonia via the injection unit through the feed point is executed, taking into account a weighting factor of ethanolamine and optional ammonia determined based on at least two criteria selected from toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency and reduction efficiency.

[0024] Preferably, the acquisition module and the command module form a control unit.

[0025] Preferably, the steam-water circuit includes a water supply container, and the feed point is located downstream of the water supply container.

[0026] Preferably, the steam-water circuit includes a main condensate pump, and the feed point is located downstream of the main condensate pump.

[0027] Preferably, ethanolamine and ammonia are injected into the circulating fluid in the circuit using an injection unit. Preferably, other compounds are injected, wherein the other compounds are selected from methanol, hydrazine, and / or combinations thereof.

[0028] Preferably, the concentration of the compound in the steam-water circuit is continuously measured.

[0029] Preferably, the steam-water circuit includes a steam generator, wherein the steam generator has a circulation space in which circulating water circulates to absorb heat from the main coolant circuit.

[0030] Preferably, the concentration of the compound is measured in the circulating water.

[0031] Preferably, the concentration of ethanolamine in the circulating water is 1×10⁻⁶. -8 mol / kg to 1×10 -3 mol / kg, and the concentration of ammonia in the circulating water is 3.5 × 10⁻⁶. -3 mol / kg or lower. More preferably, the concentration of ammonia in the circulating water is 3.5 × 10⁻⁶ mol / kg or lower. -6 Up to 3.5×10 -3 mol / kg.

[0032] Preferably, the concentration of methanol in the circulating water is 1×10⁻⁶. -7 mol / kg to 1×10 -3 The concentration of hydrazine in the circulating water is 6.25 × 10 mol / kg and / or 6.25 × 10 mol / kg. -7 mol / kg or lower. More preferably, the concentration of hydrazine in the circulating water is 3 × 10⁻⁶ mol / kg or lower. - 9 mol / kg to 6.25×10 -7 mol / kg.

[0033] Preferably, the steam-water circuit includes a feedwater section and a main condensate section.

[0034] Preferably, the concentration of the compound is measured in the water supply section and / or the main condensate section.

[0035] Preferably, a measuring unit is used to measure the values ​​of the parameters pH and redox potential in the circuit. Preferably, a measuring unit is used to measure the values ​​of the parameters pH and corrosion potential in the circuit. Preferably, a measuring unit is used to measure the values ​​of the parameters pH, redox potential, and corrosion potential in the circuit. Preferably, other parameters are measured and acquired, and at least one setpoint value is acquired for these other parameters, which are selected from the group consisting of the concentration of the compounds, the concentration of their decomposition products, and / or combinations thereof.

[0036] Preferably, the parameters in the circuit are continuously measured using a measuring unit. Preferably, the parameters are measured in the circulating water. Preferably, pH and redox potential are measured in the circulating water. Preferably, the corrosion potential is measured on the material surface.

[0037] Preferably, the parameters are measured in the water supply section and / or the main condensate section.

[0038] Preferably, the compound acts as an oxygen scavenger when exposed to gamma radiation.

[0039] This problem is further addressed by providing a system for dynamically controlling corrosion in the steam-water circuit of a nuclear power plant using ethanolamine and optionally ammonia, the system comprising:

[0040] - An injection unit located at the feed point and configured to inject the compound ethanolamine and optionally ammonia into the fluid circulating in the circuit;

[0041] - A measurement unit configured to measure the pH value and the value of at least one parameter selected from redox potential and corrosion potential in a loop;

[0042] The system also includes a control unit, which includes:

[0043] - A first acquisition module, connected to the measurement unit, configured to acquire the measured value of the parameter, and configured to acquire at least one setpoint value of the parameter;

[0044] - A command module, connected to the injection unit and configured to command the injection of the compound ethanolamine and optionally ammonia through the injection unit based on at least one setpoint value and a measured value of the acquired parameters.

[0045] Its characteristic feature is that ethanolamine is used as a reducing agent.

[0046] Preferably, the command module connected to the injection unit is further configured to command the injection of the compound ethanolamine and optional ammonia through the injection unit, taking into account a weighting factor of ethanolamine and optional ammonia determined based on at least two criteria selected from toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency, and reduction efficiency.

[0047] Preferably, the acquisition module and the command module form a control unit.

[0048] Preferably, the steam-water circuit includes a water supply container, and the feed point is located downstream of the water supply container.

[0049] Preferably, the steam-water circuit includes a main condensate pump, and the feed point is located downstream of the main condensate pump.

[0050] Preferably, ethanolamine and ammonia are injected into the fluid circulating in the loop using an injection unit. Preferably, other compounds are injected, wherein the other compounds are selected from methanol, hydrazine, and / or combinations thereof.

[0051] Preferably, the concentration of the compound in the fluid circulating in the steam-water circuit is continuously measured.

[0052] Preferably, the steam-water circuit includes a steam generator, wherein the steam generator has a circulation space in which circulating water circulates to absorb heat from the main coolant circuit.

[0053] Preferably, the concentration of the compound is measured in the circulating water.

[0054] Preferably, the concentration of ethanolamine in the circulating water is 1×10⁻⁶. -8 mol / kg to 1×10 -3 mol / kg, and the concentration of ammonia in the circulating water is 3.5 × 10⁻⁶. -3 mol / kg or lower. More preferably, the concentration of ammonia in the circulating water is 3.5 × 10⁻⁶ mol / kg or lower. -6 Up to 3.5×10 -3 mol / kg.

[0055] Preferably, the concentration of methanol in the circulating water is 1×10⁻⁶. -7 mol / kg to 1×10 -3 The concentration of hydrazine in the circulating water is 6.25 × 10 mol / kg and / or 6.25 × 10 mol / kg. -7 mol / kg or lower. More preferably, the concentration of hydrazine in the circulating water is 3 × 10⁻⁶ mol / kg or lower. - 9 mol / kg to 6.25×10 -7 mol / kg.

[0056] Preferably, the steam-water circuit includes a feedwater section and a main condensate section.

[0057] Preferably, the concentration of the compound is measured in the water supply section and / or the main condensate section.

[0058] Preferably, a measuring unit is used to measure the values ​​of the parameters pH and redox potential in the circuit. Preferably, a measuring unit is used to measure the values ​​of the parameters pH and corrosion potential in the circuit. Preferably, a measuring unit is used to measure the values ​​of the parameters pH, redox potential, and corrosion potential in the circuit. Preferably, other parameters are measured and acquired, and at least one setpoint value is acquired for these other parameters, which are selected from the group consisting of the concentration of the compounds, the concentration of their decomposition products, and / or combinations thereof.

[0059] Preferably, the parameters in the circuit are continuously measured using a measuring unit. Preferably, the parameters are measured in the circulating water. Preferably, pH and redox potential are measured in the circulating water. Preferably, the corrosion potential is measured on the material surface.

[0060] Preferably, the parameters are measured in the water supply section and / or the main condensate section.

[0061] Preferably, the compound acts as an oxygen scavenger when exposed to gamma radiation. Detailed Implementation

[0062] Accordingly, the present invention relates to a method for dynamically controlling corrosion in a steam-water circuit of a nuclear power plant, the method comprising:

[0063] - The compound ethanolamine and optional ammonia are injected into the fluid circulating in the loop using an injection unit;

[0064] - Use a measurement unit to measure the value of the parameter pH and at least one parameter selected from redox potential and corrosion potential in the loop;

[0065] - Use the acquisition module connected to the measurement unit to acquire the measured value of the parameter;

[0066] - Use the acquisition module to acquire at least one setpoint value of the parameter;

[0067] - Using a command module connected to the injection unit, based on at least one setpoint value and measured value of the acquired parameters, a command is given to inject the compound ethanolamine and optionally ammonia via the feed point through the injection unit.

[0068] Its characteristic feature is that ethanolamine is used as a reducing agent.

[0069] Furthermore, the present invention relates to a system for dynamically controlling corrosion in the steam-water circuit of a nuclear power plant using ethanolamine and optionally ammonia, the system comprising:

[0070] - An injection unit located at the feed point and configured to inject the compound ethanolamine and optionally ammonia into the fluid circulating in the circuit;

[0071] - A measurement unit configured to measure the value of parameter pH and at least one parameter selected from redox potential and corrosion potential in a loop;

[0072] The system also includes a control unit, which includes:

[0073] - A first acquisition module, connected to the measurement unit, configured to acquire the measured value of the parameter, and configured to acquire at least one setpoint value of the parameter;

[0074] - A command module, connected to the injection unit and configured to command the injection of the compound ethanolamine and optionally ammonia through the injection unit based on at least one setpoint value and a measured value of the acquired parameters.

[0075] Its characteristic feature is that ethanolamine is used as a reducing agent.

[0076] This invention offers numerous advantages. Establishing reduction conditions according to the invention, with or without hydrazine containing a reduced amount, effectively protects the metallic materials used in the steam generator. This also allows for maximum environmental and occupational safety compatibility and minimizes the required chemicals and resulting reaction products. Furthermore, this invention contains no methanol or contains a reduced amount of methanol.

[0077] Furthermore, strategies applied to water-steam cycle chemistry to date rely on reducing agents such as hydrazine, carbazide, or methanol, as well as ammonia, ethanolamine, or other alternative amines as alkalizing agents. Hydrazine, or carbazide as a hydrazine precursor, and methanol are toxic substances that pose a danger to humans and the environment.

[0078] The method described in DE 10 2015 120 722 uses methanol instead of hydrazine as a substance on the REACH SVHC (Substances of Very High Concern) list, but requires larger quantities due to its higher volatility. Methanol itself is also assessed as a toxic substance. For both hydrazine and methanol, the situation is exacerbated by the strict legal restrictions on the handling and use of these chemicals, resulting in some cases where the concentration of either hydrazine or methanol solution stored and handled in the plant does not exceed 15% (considering toxicity or fire load).

[0079] In the method described in DE 10 2015 120 722, methanol does not significantly reduce the corrosion potential as much as hydrazine or ethanolamine. Furthermore, when methanol is used as a reducing agent, significantly higher dosages are required due to its higher vapor volatility compared to hydrazine or ethanolamine, particularly to protect corrosive areas of the steam generator that are in the liquid phase. Due to the toxicity of hydrazine, its use is strictly limited under the Water Resources Act.

[0080] As illustrated in the examples of this invention, the lowest corrosion potential is achieved in the radiation field when ethanolamine is used. Corrosion protection is a primary reason for adding conditioning chemicals. In this case, the use of ethanolamine represents a significant improvement in corrosion protection. Furthermore, ethanolamine can be used to remove copper from water-steam cycles.

[0081] Compared to the method described in DE 10 2015 120 722, the advantage of using ethanolamine is that the amount of ammonia required can be reduced or even completely eliminated, since ethanolamine is also an alkalizing agent. Furthermore, because the susceptible areas are particularly in contact with the liquid phase, and ethanolamine preferentially accumulates in the liquid phase, the required concentration of ethanolamine is lower than when using methanol alone.

[0082] Preferably, in the method of the present invention, taking into account a weighting factor of ethanolamine and optional ammonia determined based on at least two criteria selected from toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency and reduction efficiency, the method commands the injection of ethanolamine and optional ammonia via the feed point through the injection unit.

[0083] Preferably, in the system of the present invention, the command module connected to the injection unit is further configured to command the injection of the compound ethanolamine and optional ammonia through the injection unit, taking into account a weighting factor of ethanolamine and optional ammonia determined based on at least two criteria selected from toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency and reduction efficiency.

[0084] Therefore, another advantage is that the dynamic equilibrium according to the invention can continuously adjust the amount of injected compound by continuously monitoring and acquiring the redox potential and pH of the circulating fluid in the steam-water loop of the nuclear power plant, as well as the corrosion potential of the engineering materials. The relative weighting factors of the injected compound, determined based on criteria such as toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency, and reduction efficiency, are also considered.

[0085] Preferably, the acquisition module and the command module form a control unit. Those skilled in the art know how to select and implement suitable acquisition modules, command modules, and control units.

[0086] Preferably, the steam-water circuit includes a water supply container, and the feed point is located downstream of the water supply container.

[0087] Preferably, the steam-water circuit includes a main condensate pump, and the feed point is located downstream of the main condensate pump.

[0088] To supply chemicals, existing feed points can be used, or appropriate automatic feed stations can be added, for example, after the main condensate pump.

[0089] Preferably, ethanolamine and ammonia are injected into the circulating fluid in the circuit using an injection unit. Preferably, other compounds are injected, wherein said other compounds are selected from methanol, hydrazine, and / or combinations thereof. In this invention, ethanolamine is used as a reducing agent and a basic reagent. Ammonia is used as an optional additional basic reagent. Optionally, methanol and / or hydrazine may be used as other reducing agents.

[0090] Preferably, in the method of the present invention, the command to inject ethanolamine and optional ammonia via the injection unit through the feed point is executed, taking into account a weighting factor of ethanolamine and optional ammonia determined based on at least two criteria selected from toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency and reduction efficiency, and further weighting factors of methanol, hydrazine and / or combinations thereof.

[0091] Preferably, in the system of the present invention, the command module connected to the injection unit is further configured to command the injection of the compound ethanolamine and optional ammonia through the injection unit, taking into account a weighting factor of ethanolamine and optional ammonia, further methanol, hydrazine and / or combinations thereof, determined based on at least two criteria selected from toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency and reduction efficiency.

[0092] According to the present invention, when determining the required amount of a single compound, a weighting factor based on the above-mentioned criteria for the single compound can be considered.

[0093] The determination of the weighting factor is relative and depends on the operational priorities of the nuclear power plant under discussion and specific national regulations. Some nuclear power plants have fairly stringent standards for the water that can be discharged. Others focus on optimal protection for the nuclear power plant itself, with less emphasis on human and environmental protection. These limitations need to be discussed with each nuclear power plant operator, and the weighting factor is selected based on this assessment. Regardless of the weighting factor chosen, two hard setpoints for corrosion protection must be met: pH and measured potential. Exemplary setpoint values ​​are pH ≥ 9.5 and potential at 280°C (i.e., corrosion potential and / or redox potential) ≤ -100mV. SHE (i.e., measured using a standard hydrogen electrode SHE).

[0094] The relative weighting factor is obtained by multiplying the weights of each individual compound under each criterion considered (for either the original or alkaline conditions), and then setting it as a percentage relationship of substances. The result will be a percentage share, meaning that reducing conditions should be established, for example, with 80% ethanolamine and 20% methanol. Alkaline conditions should be established with 20% ethanolamine and 80% ammonia. This allocation can be double-checked against other parameters, such as the concentration of decomposition products in the medium.

[0095] Therefore, the relative weighting factor is calculated based on the preferences of the nuclear power plant operators, using weights previously applied to each compound and standard. A substance is assigned a high weight if it highly achieves the specific objectives of the nuclear power plant.

[0096] Toxicity: The weighted factor for toxicity takes into account the hazards of pure, undiluted chemicals according to the MSDS (Material Safety Data Sheet), such as toxicity, mutagenicity, and carcinogenicity.

[0097] For example, hydrazine is toxic, carcinogenic, and mutagenic; methanol is moderately toxic; and ethanolamine does not have these three hazards. The weights are toxic hydrazine = 1, methanol and ethanolamine = 10 respectively (a higher weight means the substance should be preferred).

[0098] IEX (ion exchange) scaling: This takes into account the effects of chemicals on the ion exchange resins used in steam circuits (e.g., condensate purification systems, emission purification systems, etc.), excluding hard standards that have already been defined, such as IEX not meeting the requirement of ethanolamine concentration ≥3.0 - 4.5 ppm (mass).

[0099] For example, morpholine can damage IEX resin, ethanolamine only damages IEX resin at concentrations above 3 ppm (by mass), methanol – known to have no damaging effect on IEX resin, ammonia and hydrazine – known to have no damaging effect on IEX resin => weight of ammonia and hydrazine = 10, methanol and ethanolamine (≤3 ppm, by mass) = 5, morpholine = 10.

[0100] Water compatibility / environmental compatibility: National wastewater laws specify the concentrations of chemicals and substances in wastewater (with continuous discharge of water from the steam loop and refilling of the steam loop with fresh treated water); in addition to hard standards (e.g., hydrazine ≤ 2 ppm by mass), the weight can be reduced from 10 to 5 or 1 if the concentration of conditioning agents in wastewater is significant according to national wastewater laws. Another factor affecting the weighting factor is the classification in the MSDS (Material Safety Data Sheet; High Water Hazard, Medium Water Hazard, Low Water Hazard).

[0101] For example, the weighting factor can be determined by taking into account the relevant national or regional wastewater laws (such as the German wastewater law), which are further specific to each federal state.

[0102] Decomposition products: The weighting factor for decomposition products focuses primarily on organic compounds generated through the oxidation of organic conditioners. If the organic conditioner is heat-sensitive, almost all conditioners will decompose in the hot section of the steam loop, resulting in high conductivity (which is limited in steam circulation) and the production of compounds harmful to turbine condenser duct materials.

[0103] For example, morpholine decomposes quite rapidly, producing formic acid and acetic acid, which can damage turbine blades, or ammonia can lead to the formation of nitrates, which can also damage turbine blades.

[0104] Alkalinization efficiency: This weighting factor takes into account the alkalinity constant of the conditioner and its distribution between the vapor and liquid phases. The pH of the liquid phase is crucial for good corrosion protection.

[0105] For example, ammonia has a lower basicity constant than ethanolamine, but it has a higher vapor phase distribution.

[0106] Reduction efficiency: The weighting factor takes into account the open-circuit potential (which is set by adding the appropriate compound) and its distribution between the vapor and liquid phases. Its distribution in the liquid phase is crucial for good corrosion protection. Furthermore, this weighting factor considers the reduction efficiency outside the steam generator (lower temperature, no radiation field) and the reaction rate with oxygen.

[0107] The simplest way to assign weights to individual compounds is the three-part rule: Good / Highly Preferred / Highly Suitable = 10, Medium / Medium Suitable = 5, and Poor / Not Preferred / Unsuitable = 1. This "scoring" principle allows consideration of the specific requirements / preferences of nuclear power plants, as well as the standards for ensuring high corrosion protection and low harmful effects on the system.

[0108] For pH adjustment or alkalization, ethanolamine cannot achieve pH values ​​of, for example, around 9.9 or higher. Ethanolamine can also be somewhat disadvantageous in terms of nuclear power plant compatibility, as ion exchangers are depleted or age more quickly, for example, under proper continuous operation of steam generator blowdown purification. However, ethanolamine has highly advantageous reducing properties and is suitable if the operators of the nuclear power plant in question are concerned with high occupational safety and high environmental compatibility. As with most compounds, there is a trade-off between advantages and disadvantages, and those skilled in the art will choose ethanolamine as a reducing agent if they deem it suitable for their needs.

[0109] Table 1 shows the weights assumed based on the importance of each weighting factor and the performance of each compound. Exemplary weights for ethanolamine, ammonia, methanol, and hydrazine with respect to each standard are shown, which can be used to calculate the relative weighting factors. An arbitrary scale from 1 to 10 is used, where 1 is the least desirable and 10 is the most desirable.

[0110] Table 1

[0111]

[0112] As mentioned above, when considering occupational safety standards, hydrazine and methanol, which require high occupational safety standards, have a weight of 1, while ammonia and ethanolamine, which have low toxicity, have a favorable weight of 10. Regarding the standard of alkalization effectiveness, ammonia is an effective alkalizing compound and has a weight of 10, while methanol and hydrazine, due to their low alkalization effectiveness, have a weight of 1, and so on.

[0113] If we use the weights from the various criteria in Table 1, ethanolamine and ammonia can be obtained with the following relative weighting factors:

[0114] Ethanolamine: 10 (toxicity) × 10 (water compatibility) × 5 (degradation products) × 5 (component compatibility) × 5 (alkalization efficiency) = 12,500

[0115] Ammonia: 10 (toxicity) × 5 (water compatibility) × 10 (degradation products) × 10 (component compatibility) × 10 (alkalization efficiency) = 50.000

[0116] Based on the relative weighting factors, the final proportions used for each component can be calculated as percentages as follows (when calculating the proportions, the determined weighting factors must be divided by the sum of all weighting factors required for the task):

[0117] The proportion used for alkalization (ethanolamine) = 12,500 / (50,000 + 12,500) = 20%.

[0118] The proportion of ammonia used for alkalization = 50,000 / (50,000 + 12,500) = 80%

[0119] Therefore, to achieve a pH ≥ 9.5, ammonia should contribute 4 / 5 to the pH, and ethanolamine should contribute 1 / 5. The system measures the current pH, determines the missing OH concentration, calculates the OH ions generated by the ammonia and ethanolamine feeds respectively, and then adjusts the feed rate so that 4 / 5 of the OH ions come from the ammonia feed and 1 / 5 from the ethanolamine feed.

[0120] Figure 1 It further emphasizes how pH depends on the amounts of ethanolamine and ammonia. Starting at ethanolamine concentrations greater than 4.5 ppm (by mass), it may have an adverse effect on ion exchangers in purification systems (sewage purification systems, condensate purification systems). Figure 1 It was also emphasized that a pH value of 9.9 or higher can only be achieved by using ammonia.

[0121] The relative weighting factor for ethanolamine and optional ammonia is determined based on at least three, more preferably at least four, and even more preferably at least five criteria selected from toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency, and reduction efficiency. Most preferably, the relative weighting factor for ethanolamine and optional ammonia is determined based on criteria for toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency, and reduction efficiency.

[0122] Typically, the weighting factor can be determined as follows:

[0123] Wf i Weighting factor

[0124] i ranges from 1 to x, where x = the amount of conditioning agent used.

[0125] j is from 1 to y, where y = the number of standards used.

[0126] ∏Wf Ri,max =Product of the maximum values ​​of each standard

[0127] Wf Ri,i The relative weighting factor of the chemicals used in the standard.

[0128] Wf R1 =Wf R1,1 ×Wf R1,2 ×……×Wf R1,z =The product of the relative weighting factors of all chemicals used in a standard setting

[0129] Wf i =(Wf Ri,1 ×Wf Ri,2 ×…×Wf Riz ) / ∏Wf Ri,max

[0130] Preferably, the concentration of the compound in the fluid circulating in the steam-water loop is continuously measured.

[0131] Preferably, the steam-water circuit includes a steam generator having a circulation space in which circulating water circulates to absorb heat from the main coolant circuit.

[0132] Preferably, the concentration of the compound is measured in circulating water.

[0133] Preferably, the concentration of ethanolamine in the circulating water is 1×10⁻⁶. -8 mol / kg to 1×10 -3 The concentration of ammonia in the circulating water is 3.5 × 10⁻⁶ mol / kg. -3 mol / kg or lower. More preferably, the concentration of ammonia in the circulating water is 3.5 × 10⁻⁶ mol / kg or lower.-6 Up to 3.5×10 - 3 mol / kg.

[0134] Preferably, the concentration of methanol in the circulating water is 1×10⁻⁶. -7 mol / kg to 1×10 -3 The concentration of hydrazine in the circulating water is 6.25 × 10⁻⁶ mol / kg. -7 mol / kg or lower. More preferably, the concentration of hydrazine in the circulating water is 3 × 10⁻⁶ mol / kg or lower. -9 mol / kg to 6.25×10 -7 mol / kg.

[0135] When only ammonia and ethanolamine (ETA) are used for alkalization, the concentration of ethanolamine can be controlled by pH based on the ammonia concentration. Alternatively, the content of ethanolamine can be definitively determined by ion-exchange chromatography. Furthermore, commercial TOC (Total Organic Matter) flow analyzers can also be used to determine the concentration of ethanolamine (in the absence of other organic compounds such as methanol), and they also offer continuous measurement capabilities.

[0136] The concentration of methanol can be continuously measured using a commercially available TOC flow analyzer based on the concentration of ethanolamine.

[0137] The concentrations of ammonia and hydrazine in a water-steam cycle system can be determined by photometric measurement or an automated flow-through photometer.

[0138] Flow analyzers that have been calibrated for certain compounds (e.g., methanol analyzers) or can be calibrated are also available.

[0139] Furthermore, it is possible to determine the concentration of compounds discontinuously using high-pressure chromatography.

[0140] Preferably, a measuring unit is used to measure the values ​​of the parameters pH and redox potential in the circuit. Preferably, a measuring unit is used to measure the values ​​of the parameters pH and corrosion potential in the circuit. Preferably, a measuring unit is used to measure the values ​​of the parameters pH, redox potential, and corrosion potential in the circuit. Preferably, other parameters are measured and acquired, and at least one setpoint value is acquired for these other parameters, said other parameters being selected from the group consisting of dissolved oxygen content, compound concentration, concentration of their decomposition products, and / or combinations thereof.

[0141] Commercially available pH measurement sensors can be used to continuously monitor the pH value in steam-water circulation systems.

[0142] To monitor the oxygen content in the water-steam cycle system of a pressurized heavy water reactor, oxygen or pH in the main condensate and / or feed water is measured online (i.e., continuously). For this purpose, commercially available oxygen sensors or corresponding pH sensors with very high measurement accuracy (ppb level, ≥0.1 ppb by mass) are used. Digital measurements can be used as input measurements for automated feeding systems.

[0143] The redox potential and corrosion potential in the nuclear steam generator loop can be determined by potential measurement and a suitable reference electrode.

[0144] Preferably, the set point or limit of the oxidation-reduction and / or corrosion potential measured in the steam-water circuit is E(280°C)≤-100mV, that is, the potential at 280°C is ≤-100mV or lower; more preferably E(280°C)≤-200mV; even more preferably E(280°C)≤-300mV.

[0145] Preferably, the set point or limit of pH in the steam-water circuit, especially in the feed water, is pH (25°C) ≥ 9.5, that is, pH is 9.5 or higher; more preferably pH (25°C) ≥ 9.8, and even more preferably pH (25°C) ≥ 9.9.

[0146] Preferably, the set point or limit for the hydrazine concentration in the circulating water is 6.25 × 10⁻⁶. -7 mol / kg or lower, preferably 4.6 × 10 mol / kg -7 mol / kg or lower, more preferably 3×10 -7 mol / kg or lower.

[0147] Preferably, the set point or limit of dissolved O2 concentration in the steam generator is DO (dissolved oxygen) ≤ 20 ppb (by mass), that is, the dissolved oxygen concentration is 20 ppb (by mass) or less; more preferably DO ≤ 5 ppb (by mass); even more preferably DO ≤ 2 ppb (by mass); even more preferably DO ≤ 1 ppb (by mass).

[0148] Therefore, under certain conditions, according to the present invention, it is necessary to solve the following exemplary solution matrix. “Wf” is the product of all relative weighting factors of a compound, and ETA is ethanolamine.

[0149] w(ETA)×Wf(ETA) / Wf(ETA)×Wf(NH3)+w(NH3)×Wf(NH3) / Wf(ETA)×Wf(NH3),

[0150] Here, w is the contribution to alkalization, and the target pH value is higher than the hard set limit of pH ≥ 9.5.

[0151] v(ETA)×Wf(ETA) / [Wf(ETA)×Wf(N2H4)×Wf(MeOH)]+v(MeOH)×Wf(MeOH) / [Wf(ETA)×Wf(N2H4)×Wf(MeOH)]+v(N2H4)×Wf(N2H4) / [Wf(ETA)×Wf(N2H4)×Wf(MeOH)],

[0152] Where v is the contribution of the reduction conditions, and the target redox and / or corrosion potential is -100mV or less.

[0153] This makes one or more of the following conditions satisfied:

[0154] Potential E (280℃) ≤ -300mV

[0155] Dissolved O2 ≤ 5 ppb (by mass)

[0156] N2H4 ≤ 20 ppb (by mass) (≤ 6.25 × 10⁻⁶) -7 mol / kg) or at least N2H4 ≤ 10 ppb (by mass) (≤ 3 × 10 mol / kg) -7 mol / kg

[0157] As described above, parameters can be measured continuously. Based on the continuously monitored and recorded parameters, the required amount of the compound to be fed is constantly recalculated and adjusted. Furthermore, considering weighting factors, the required amount of the compound to be fed is constantly recalculated and adjusted.

[0158] Preferably, the monitoring and acquisition of various parameters and set points, the monitoring of the concentration of each compound, the calculation of the required amount of compound, and the feeding of compound are all automatic.

[0159] Preferably, an automated feeding system is used, which automatically retrieves collected online and discontinuous data and uses them to calculate the feed rate. However, this places demands on the electronic data of the measurements and the corresponding laboratory information management system of the nuclear power plant.

[0160] This can be simplified by using separate software that records data automatically or manually, which can then be used to manually set the feed rate or, in turn, transmit it to an automatic feeding system.

[0161] Based on the specified initial concentrations of ethanolamine and methanol, and the specified general conditions (e.g., hydrazine-free, O2 content, open-circuit potential, etc.), the feed rate of ethanolamine will affect the feed rates of hydrazine and ammonia, and will result in the need to reduce these feed rates. Since each conditioning chemical has an effect on the others, a dynamic equilibrium will be established over time, which is also very flexible for any other changes in the water / steam cycle (e.g., changes in intake air, steam generator scaling, etc.).

[0162] The system can be further simplified by limiting the feed rates of methanol and / or ethanolamine, but this will reduce the optimization effect. Depending on the control and diagnostic parameters, this will have a corresponding impact on ammonia or, possibly, hydrazine.

[0163] Preferably, when exposed to gamma radiation, the compounds, particularly ethanolamine and optionally other methanol and / or hydrazine, act as oxygen scavengers.

[0164] Since oxygen removal is caused solely by gamma radiation present in the steam generator, the oxygen content in the steam-water circuit can be precisely regulated, thus allowing the use of AVT(O) operating mode in the steam-water circuit of light or heavy water reactors. Attached Figure Description

[0165] Figure 1 The pH value depends on the amount of ethanolamine and ammonia in the circuit.

[0166] Figure 2 illustrates the effects of hydrazine, methanol, formaldehyde, and ethanolamine on the oxygen concentration at the inlet and outlet of the test solution, as well as the progression of the potentials (redox potentials) of platinum and four typical steam generator construction materials in a continuously running test loop, thus showing a time range of 1750 to 2750 hours (i.e., 1000 hours) (the redox potential and oxygen concentration of platinum are repeated in each figure): (a) Redox potential of stainless steel 1.4541 (SS); (b) Redox potential of Alloy 800 pre-oxidized before the start of the test; (c) Redox potential of Alloy 800; (d) Redox potential of Alloy 690TT.

[0167] Figure 3 shows the test loop experiment; (a) schematic diagram of the autoclave; (b) calculation of the energy dose rate (DL) of 16 distances (fitting functions); (d) geometry of the autoclave; (e) autoclave clustered into 236 clusters.

[0168] Figure 4 A schematic diagram of a steam-water circuit in a nuclear power plant is shown.

[0169] Example

[0170] Example 1

[0171] Figure 2 shows the redox potentials of platinum, stainless steel 1.4541 (SS), pre-oxidized Alloy 800, Alloy 800, and Alloy 690TT under steam generator conditions (T=280℃, pH=9.5) in a continuously operating test loop. The amounts of the compounds and the time ranges in which they were used are indicated in Figure 2. Figure 2 also highlights the presence or absence of a radiation field.

[0172] The more negative the measured corrosion potential, the better the corrosion protection effect, or the higher the potential of the reduction conditions on the material surface. Two critical cases were distinguished: the steam generator at full power has a corresponding radiation field, and there is no radiation field.

[0173] For steam generators, redox potentials are specified in relevant water chemistry guidelines. Redox potential is understood as the open-circuit potential of platinum, and when using an Ag / AgCl electrode as a reference electrode, this potential is significant for corrosion potential. Corrosion potential is understood as the open-circuit potential of the structural materials used (e.g., Alloy 800 or Alloy 690).

[0174] As shown schematically in Figure 3, the test circuit consists of a heated autoclave and simulates conditions in a steam generator. The autoclave is a reservoir for alkalizing demineralized water and includes injection points for feeding different reducing agents and sensors for monitoring pH, dissolved oxygen, and conductivity.

[0175] Ammonia or ethanolamine is used as the alkalizing agent. The reducing agent (methanol, formaldehyde, hydrazine, or ethanolamine) is injected directly and continuously upstream of the autoclave using a high-performance liquid chromatography (HPLC) pump. The injected chemical is then degassed separately. The injection rate of the reducing agent varies from 0.2 mL / min to 0.5 mL / min.

[0176] The demineralized water is pretreated by alkalizing it to a pH of 9.5 to 10, degassing it, and then exposing it to 20 ppb (by mass) of oxygen. The desired concentration of reducing agent is added immediately before the preheating section. Dissolved oxygen in the medium is measured before the feed point. Oxygen concentration is measured using commercially available oxygen sensors located downstream and upstream of the compressor in the medium flow at 25°C.

[0177] The medium is heated to 280°C in a heating section (not shown) upstream of the autoclave and exists in a single phase (i.e., liquid state). The flow rate through the 2-liter stainless steel autoclave is 8 L / h. In the stainless steel autoclave, sample pieces of different materials are arranged in a ring around an immersion tube located at the center of the autoclave.

[0178] A Cs-137 gamma source with an activity up to 3.7 E11 Bq was inserted into the immersion tube, exposing the pressurizer medium to radioactive radiation. The average energy dose rate was 5.9 Gy / h. The gamma emitter was stored in a shielded container, and the pressurizer was manually and remotely moved in and out of the test pressurizer.

[0179] More specifically, the energy dose rate from the gamma emitter and the gamma energy deposited in the pressurizer container were estimated using the Monte Carlo program MicroShield V9.06, as shown in Figure 3(b). Sixteen different distances were considered, taking into account dose accumulation, attenuation of the corresponding upstream water layer (100 bar / 280 °C), and absorption by the source housing, immersion tube, and extension tip.

[0180] As shown in Figure 3(c), the volume of the autoclave is divided into 1cm sections as shown in Figure 3(d). 2 Clusters were identified, and the absorbed dose rate of 236 clusters and their individual distances to the gamma source were calculated. Considering 236 clusters, the average energy dose rate was 5.9 Gy / h. This equates to 564 Joules of gamma energy deposited over a typical exposure time of approximately 65 hours. The calculations are based on the following values:

[0181] Volume of water in the autoclave: 1958 cm³ 3

[0182] The density of water at 100 bar / 280℃ is 0.756 g / cm³. 3

[0183] Mass of water in the autoclave: 1.48 kg

[0184] After leaving the stainless steel autoclave, the medium was cooled to room temperature and dissolved oxygen and pH were measured.

[0185] All parameters are monitored and recorded using a data logger: conductivity (LF) output, conductivity input, dissolved oxygen (DO) output, DO input, temperature output, temperature input, pH (25°C) output, and pH (25°C) input.

[0186] An externally cooled Ag / AgCl electrode is used as a reference electrode. Platinum sample plates are used to measure the redox potential of the fluid. The working electrodes used to measure the corrosion potential are sample plates made of typical steam generator construction materials. They are made of austenitic stainless steel (1.4541), alloy 800, alloy 800, and alloy 690TT.

[0187] As can be seen from Figure 2, ethanolamine in the radiation field caused the lowest corrosion potential of the tested steam generator material, even lower than that of hydrazine, which is widely used and proven. CH2O (formaldehyde) was chosen as another representative C, H, O compound, and it has better reducing properties than methanol.

[0188] Clearly, ethanolamine induces optimal reduction conditions on the surface of steam generator materials in both the presence and absence of a radiation field. To date, ethanolamine has not been described as an effective reducing agent for nuclear facilities.

[0189] This leads to the following applications: In the simplest applications, ethanolamine and ammonia are sufficient to establish comprehensive corrosion protection in the water-steam cycle of a nuclear power plant. In extended applications, conditioning chemicals methanol and hydrazine can be added (if needed). The required concentration ratio is determined and adjusted dynamically and weighted according to other criteria.

[0190] For example, if relevant regulations exist, the weight of conditioning chemicals can be reduced or disregarded. For instance, national regulations regarding water quality, such as hydrazine-free, TOC limits, etc., could be considered, or operator specifications regarding the most economical operating mode (i.e., the lowest cost) could also be taken into account.

[0191] Here, the required quantities must be specified, including adjustment efficiency and cost per unit quantity, which leads to corresponding weighting. Dynamic balancing can be optimally controlled with appropriate data acquisition and processing, making it ideal to use a computer-controlled system for the acquisition and processing of measurements.

[0192] For example, if the measuring system detects an increase in oxygen in the system due to a condenser leak, the system can calculate the adjusted concentration without delay, i.e., firstly, the reducing agent used can be adjusted according to the weight; then it can be checked whether this affects the pH value, and the alkalinity value can also be adjusted accordingly.

[0193] However, before changing the concentration, it's advisable to check whether rigid standards (such as maximum concentrations in wastewater) or weightings fully allow for the change. The result is a combination of all conditioning chemicals optimized for the nuclear power plant, responding appropriately to changes in the water-steam cycle.

[0194] Example 2

[0195] exist Figure 4 The image shows a nuclear power plant 10, which includes a main coolant circuit 12 and a separate steam-water circuit 14. The nuclear power plant 10 includes a reactor 16 (through which the main coolant circuit 12 flows) and a steam generator 18, a condenser 20, and a feedwater container 22 in the steam-water circuit 14.

[0196] Preferably, reactor 16 is a pressurized water reactor. The heat generated in reactor 16 is transferred to steam generator 18 via main coolant circuit 12, and then to steam-water circuit 14 in steam generator 18. In the first high-pressure turbine 24 and the second low-pressure turbine 26, the thermal energy of the hot water steam is converted into kinetic energy, which is ultimately used to drive a generator (not shown) and thereby generate electricity.

[0197] In condenser 20, cooled water vapor is converted into its liquid phase, forming the main condensate. For this purpose, condenser 20 is cooled by cooling water supply line 28, and warm exhaust gas is discharged via an air suction pump in condenser 30. Losses are compensated by balance water supply line 32.

[0198] The main condensate is transported from the main condensate section 34 (from the condenser 20 via the main condensate pump 36 to the feedwater container 22) into the feedwater container 22. In the feedwater container 22, the main condensate and water from the water separator 38 located between the high-pressure turbine 24 and the low-pressure turbine 26 are collected and retained, and supplied as feedwater to the steam generator.

[0199] In the feedwater section 40 of the feedwater supply line 54 leading from the feedwater container 22 to the steam generator, feedwater is pumped back to the steam generator 18 by the feedwater pump 42, where it is reused to absorb heat, and the secondary steam-water circuit 14 is shut off. In the feedwater section 40, a feed point 44 is located between the feedwater container 22 and the feedwater pump 42, at which ethanolamine is introduced into the steam-water circuit 14 via a feed device 46.

[0200] In steam generator 18, the reducing agent is exposed to gamma radiation and acts as an oxygen scavenger. A device 50 is provided in the circulation space 48 of the steam generator for continuously measuring the reducing agent concentration and redox potential. For this purpose, device 50 includes a potential sensor 58.

[0201] As an alternative or additional measure, the concentration of the reducing agent in the circulating water can be continuously measured by a TOC flow meter 56 in a sampling line 60 leading from the steam generator 18.

[0202] In addition, a sampling line 61 may be provided upstream of the steam generator 18 for water supply line 54 to measure via TOC flow meter 56 and / or potential sensor 58.

[0203] Intermediate heater 52 is located between water separator 28 and low-pressure turbine 26, as well as in main condensate section 34 and feedwater section 40, which are used to return the released heat energy to steam-water circuit 14.

[0204] The following describes the method of operating nuclear power plant 10 using an example of a 1000MW nuclear power plant that uses ethanolamine as a reducing agent.

[0205] For the startup and power operation of reactor 16, the concentration of ethanolamine in the circulating water of the steam generator is set to 3 μg / kg to 10 mg / kg. The concentration of ethanolamine in the feed water is set to 2 to 3 times that in the circulating water to compensate for losses caused by adsorption on the surfaces of the steam-water loop.

[0206] For shutdown preservation, provide 1×10 in the steam generator. -8 Up to 5×10 -2 Ethanolamine concentration in mol / kg.

[0207] The amount of ethanolamine that must be supplied daily during power operation to achieve the appropriate concentration depends on the nuclear power plant's output, ranging from 16 kg / d to 41 kg / d in this case. Therefore, in the case of a conventional reducing agent tank with a volume of 1500 L, a single tank fill is sufficient to supply ethanolamine to the steam-water loop 14 for several weeks before the tank must be refilled. Due to the higher feedwater flow, the ethanolamine usage at the 1300 MW nuclear power plant increased by approximately 25%.

[0208] Injecting ethanolamine into the steam-water circuit allows for adjustment of the oxidation conditions (AVT(O) operation mode) in the steam-water circuit 14 outside the steam generator 18, maintaining the oxygen concentration in the steam-water circuit 14 at less than 0.1 mg / kg according to VGB standards.

[0209] In addition, the pH in the steam-water loop 14 is set to 9.5 or higher. This is further adjusted to an alkaline pH using ammonia.

[0210] Preferably, ethanolamine is introduced into the steam-water circuit 14 from the feed point 44 downstream of the feed water container 22 via the feed device 46, because some of the ethanolamine is lost due to adsorption on the surface in the steam-water circuit, thus allowing the usable ethanolamine to be obtained from the start of the feed.

[0211] In an embodiment of the nuclear power plant 10 without a feedwater container 22 (not shown), it may be advantageous to select an alternative feed point instead of feed point 44, for example, directly upstream of the steam generator 18 or directly downstream of the water separator 38. Multiple feed points 44 may also be provided in the steam-water loop 14. Typically, the most suitable feed point 44 for the specific nuclear power plant should be determined in conjunction with the operator.

[0212] To measure and regulate the concentration of ethanolamine in the steam-water circuit 14, the oxygen content in the main condensate of the main condensate section 34 and the feed water of the feedwater section 40 is monitored. For this purpose, a commercially available sensor with a measurement accuracy in the ppb range (μg / kg) is used for continuous measurement. Because this measurement method is continuous, the measurement signal can be used as an input parameter for process control.

[0213] However, the concentration of ethanolamine in the feed water and circulating water in the circulation space 48 of the steam generator 18 is continuously measured by a commercially available TOC flow meter 56 via sampling lines 60 and 61.

[0214] Preferably, these continuous measurements can be supplemented by other discontinuous analytical methods, for example, which can be used to distinguish various organic compounds.

[0215] Commercially available analytical devices and methods also allow for continuous measurement of the concentration of reducing ethanolamine in circulating water and feed water when exposed to gamma radiation.

[0216] Experience from industrial nuclear power plants shows that ethanolamine is thermally stable in conventional steam boilers, even at temperatures as high as 530°C and pressures as high as 270 bar. However, oxidative decomposition of ethanolamine occurs if an oxidant is also present in a conventional steam boiler. In contrast, the purely thermal decomposition of ethanolamine in the circulating water of steam generator 18 is negligible, allowing for the adjustment and control of the concentration of ethanolamine in the feed water necessary for the corresponding operating conditions of the nuclear power plant based on the current consumption of ethanolamine in the steam generator.

[0217] Therefore, the current ethanolamine consumption in steam generator 18, through the removal of oxygen and other free radicals, is determined by continuous measurements in the circulating water and feed water. The total ethanolamine turnover in steam generator 18 consists essentially of two components:

[0218] (1) Radiolytic decomposition (metabolic rate) by γ radiation acting on the second side of the steam generator 18;

[0219] (2) Radiation-induced decomposition of ethanolamine by oxygen or other oxidizing substances (e.g., copper ions and copper oxides or ferric oxides and hydroxides) in steam generator 18.

[0220] The amount of oxygen introduced into steam generator 18 is known by continuously measuring the oxygen content in the main condensate and feed water. By evaluating operating phases with elevated oxygen content or by specifically increasing the oxygen content in the feed water, the consumption of ethanolamine caused by radiation-induced oxidation can be precisely determined and adjusted, thereby always ensuring the reduction conditions in steam generator 18. This allows for the adjustment of oxidation conditions (AVT(O) operation) in the steam-water circuit 14 outside steam generator 18, while simultaneously ensuring the reduction conditions (AVT(R) operation) in steam generator 18.

[0221] For example, if a rapid and significant increase in oxygen concentration is recorded in the main condensate and feed water, the concentration of reducing agent in the feed water can be increased immediately through this adjustment, thereby immediately increasing the turnover of ethanolamine in the steam generator.

[0222] During power operation, ethanolamine and optionally additional methanol are fed at a feed water concentration of 200 ppb (by mass).

[0223] The newly installed automatic feeding system can be used to feed conditioning chemicals, or the hydrazine feed station can be used alternately with the bidirectional distributor for feeding ethanolamine and methanol, since hydrazine feeding terminates at this point.

[0224] For chemical monitoring of the process, continuous TOC analyzers are installed in the feed water and circulating water sampling systems, and potential measurements are performed in the circulating water of all steam generators.

[0225] The monitored chemical parameters are transmitted to the automated feeding system (actively connected to the I&C network) or input into dedicated software to calculate the required conditioning chemicals (autonomous operation mode). The newly calculated feed rate is automatically set or stored in the system.

[0226] The required daily intake of ethanolamine is initially 35 kg / day.

[0227] For each new measurement of the monitored chemical parameter, in some cases, the amount will be significantly reduced until optimal operating standards are met. The amount of ammonia used also needs to be reduced or adjusted over time.

[0228] By monitoring parameters such as the open circuit potential in the circulating water of the steam generator or on the materials of the steam generator, as well as the oxygen concentration in the circulating water of the steam generator, the reduction conditions in the steam generator are ensured.

[0229] Continuous measurement of the TOC value in the circulating water enabled the determination of the total methanol and ethanolamine consumption in the steam generator. This consumption consists of (1) adsorption on the surface, (2) oxidative degradation due to oxygen or other oxidizing substances (e.g., copper ions and copper oxides or ferric oxides and hydroxides) in the steam generator, and (3) radiolytic degradation caused by incident gamma radiation.

Claims

1. A method for dynamically controlling corrosion in a steam-water circuit of a nuclear power plant, the method comprising: - The compound ethanolamine and optional ammonia are injected into the fluid circulating in the loop using an injection unit; - Use a measurement unit to measure the parameters pH and at least one parameter selected from redox potential and corrosion potential in the loop; - Use the acquisition module connected to the measurement unit to acquire the measured value of the parameter; - Use the acquisition module to acquire at least one setpoint value of the parameter; - Using a command module connected to the injection unit, based on at least one setpoint value and measured value of the acquired parameters, a command is given to inject the compound ethanolamine and optionally ammonia via the feed point through the injection unit. Its characteristic feature is that ethanolamine is used as a reducing agent.

2. The method according to claim 1, wherein, Taking into account the weighting factors of ethanolamine and ammonia determined based on at least two criteria selected from toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency, and reduction efficiency, the command to inject ethanolamine and ammonia through the injection unit via the feed point is executed.

3. The method according to claim 1 or 2, wherein, The acquisition module and the command module form a control unit.

4. The method according to any one of claims 1 to 3, wherein, The steam-water circuit includes a water supply container, and the feed point is located downstream of the water supply container.

5. The method according to any one of claims 1 to 4, wherein, The steam-water circuit includes a main condensate pump, and the feed point is located downstream of the main condensate pump.

6. The method according to any one of claims 1 to 5, wherein, Injecting other compounds, wherein the other compounds are selected from methanol, hydrazine and / or combinations thereof.

7. The method according to any one of claims 1 to 6, wherein, The concentration of the compound in the fluid circulating in the steam-water circuit is continuously measured.

8. The method according to any one of claims 1 to 7, wherein, The steam-water circuit includes a steam generator having a circulation space in which circulating water circulates to absorb heat from the main coolant circuit.

9. The method according to claim 8, wherein, The concentration of the compound was measured in the circulating water.

10. The method according to any one of claims 1 to 9, wherein, The concentration of ethanolamine in the circulating water is 1×10⁻⁶. -8 mol / kg to 1×10 -3 mol / kg, and the concentration of ammonia in the circulating water is 3.5 × 10⁻⁶. -3 The concentration of ammonia in the circulating water is 3.5 × 10⁻⁶ mol / kg or lower, preferably 3.5 × 10⁻⁶ mol / kg or lower. -6 Up to 3.5×10 -3 mol / kg.

11. The method according to any one of claims 6 to 10, wherein, The concentration of methanol in the circulating water is 1×10⁻⁶. -7 mol / kg to 1×10 -3 The concentration of hydrazine in the circulating water is 6.25 × 10 mol / kg and / or 6.25 × 10 mol / kg. -7 The concentration of hydrazine in the circulating water is 3 × 10 mol / kg or lower, more preferably 3 × 10 mol / kg or lower. -9 mol / kg to 6.25×10 -7 mol / kg.

12. The method according to any one of claims 1 to 11, wherein, The steam-water circuit includes a feedwater section and a main condensate section.

13. The method according to claim 12, wherein, The concentration of the compound is measured in the water supply section and / or the main condensate section.

14. The method according to any one of claims 1 to 13, wherein, Measure and acquire other parameters and acquire at least one setpoint value for said other parameters, said other parameters being selected from the group consisting of oxygen concentration, concentration of said compounds, concentration of their decomposition products and / or combinations thereof.

15. The method according to any one of claims 1 to 14, wherein, The parameters in the circuit are continuously measured using a measuring unit.

16. The method according to any one of claims 8 to 15, wherein, The parameter is measured in the circulating water.

17. The method according to any one of claims 12 to 16, wherein, The parameters are measured in the water supply section and / or the main condensate section.

18. The method according to any one of claims 1 to 17, wherein, When exposed to gamma radiation, the compound acts as an oxygen scavenger.

19. A system for dynamically controlling corrosion in a steam-water circuit of a nuclear power plant using ethanolamine and optionally ammonia, the system comprising: - An injection unit located at the feed point and configured to inject the compounds ethanolamine and optionally ammonia into the fluid circulating in the circuit; as well as - A measurement unit configured to measure the value of parameter pH and at least one parameter selected from redox potential and corrosion potential in a loop; The system also includes a control unit, which includes: - A first acquisition module, connected to the measurement unit, configured to acquire the measured value of the parameter, and configured to acquire at least one setpoint value of the parameter; - A command module, connected to the injection unit and configured to command the injection of the compound ethanolamine and optionally ammonia through the injection unit based on at least one setpoint value and a measured value of the acquired parameters. Its characteristic feature is that ethanolamine is used as a reducing agent.

20. The system according to claim 19, wherein, The command module connected to the injection unit is also configured to command the injection of the compounds ethanolamine and ammonia through the injection unit, taking into account a weighting factor for ethanolamine and ammonia determined based on at least two criteria selected from toxicity, water compatibility, decomposition products, IEX scaling, alkalization efficiency, and reduction efficiency.

21. The system according to claim 19 or 20, wherein, The acquisition module and the command module form a control unit.

22. The system according to any one of claims 19 to 21, wherein, The steam-water circuit includes a water supply container, and the feed point is located downstream of the water supply container.

23. The system according to any one of claims 19 to 22, wherein, The steam-water circuit includes a main condensate pump, and the feed point is located downstream of the main condensate pump.

24. The system according to any one of claims 19 to 23, wherein, Injecting other compounds, wherein the other compounds are selected from methanol, hydrazine and / or combinations thereof.

25. The system according to any one of claims 19 to 24, wherein, The concentration of the compound circulating in the steam-water circuit is continuously measured.

26. The system according to any one of claims 19 to 25, wherein, The steam-water circuit includes a steam generator having a circulation space in which circulating water circulates to absorb heat from the main coolant circuit.

27. The system according to claim 26, wherein, The concentration of the compound was measured in the circulating water.

28. The method according to any one of claims 19 to 27, wherein, The concentration of ethanolamine in the circulating water is 1×10⁻⁶. -8 mol / kg to 1×10 -3 mol / kg, and the concentration of ammonia in the circulating water is 3.5 × 10⁻⁶. -3 The concentration of ammonia in the circulating water is 3.5 × 10⁻⁶ mol / kg or lower, preferably 3.5 × 10⁻⁶ mol / kg or lower. -6 Up to 3.5×10 -3 mol / kg.

29. The method according to any one of claims 24 to 28, wherein, The concentration of methanol in the circulating water is 1×10⁻⁶. -7 mol / kg to 1×10 -3 The concentration of hydrazine in the circulating water is 6.25 × 10 mol / kg and / or 6.25 × 10 mol / kg. -7 The concentration of hydrazine in the circulating water is 3 × 10 mol / kg or lower, more preferably 3 × 10 mol / kg or lower. -9 mol / kg to 6.25×10 -7 mol / kg.

30. The method according to any one of claims 19 to 29, wherein, The steam-water circuit includes a feedwater section and a main condensate section.

31. The method according to claim 30, wherein, The concentration of the compound is measured in the water supply section and / or the main condensate section.

32. The method according to any one of claims 19 to 31, wherein, Measure and acquire other parameters and acquire at least one setpoint value for said other parameters, said other parameters being selected from the group consisting of oxygen concentration, concentration of compounds, concentration of their decomposition products and / or combinations thereof.

33. The method according to any one of claims 19 to 32, wherein, The parameters in the circuit are continuously measured using a measuring unit.

34. The method according to any one of claims 26 to 34, wherein, The parameter is measured in the circulating water.

35. The method according to any one of claims 30 to 34, wherein, The parameters are measured in the water supply section and / or the main condensate section.

36. The method according to any one of claims 19 to 35, wherein, When exposed to gamma radiation, the compound acts as an oxygen scavenger.

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