A method for feedwater treatment of a high temperature gas cooled reactor steam generator

Abstract

The present application relates to nuclear power technology field, specifically to a kind of high temperature gas cooled reactor steam generator feedwater treatment method, comprising: before starting, using first reducing full volatile treatment mode to treat feedwater;During starting, using second reducing full volatile treatment mode to treat feedwater;When running and after completing two-phase flow transition in steam generator secondary side, using oxidizing full volatile treatment mode to treat feedwater;When stable operation, using oxygen treatment mode to treat feedwater;When shutdown and before entering two-phase flow in steam generator secondary side, using second reducing full volatile treatment mode to treat feedwater;During shutdown stage and after completing two-phase flow transition to become liquid phase in steam generator secondary side, using third reducing full volatile treatment mode to treat feedwater;When unscheduled shutdown, adding hydrazine and ammonia water in feedwater;The present application selects appropriate feedwater treatment mode by different state of high temperature gas cooled reactor, reduces corrosion product generation, prevents and slows down deposition, ensures safe and stable operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear power, in particular to a feedwater treatment method for a high-temperature gas-cooled reactor steam generator. BACKGROUND

[0002] The high-temperature gas-cooled reactor steam generator is generally a direct-current vertical assembly structure, each steam generator is composed of a plurality of heat exchange assemblies, each heat exchange assembly comprises a plurality of heat transfer pipes. The heat transfer pipe is generally a spiral coil structure, mainly made of T22 alloy material and Incoloy 800H heat-resistant alloy material. The shell side of the heat transfer pipe is generally a primary coolant, and the coolant is generally helium; the tube side of the heat transfer pipe is generally a secondary water or steam. In order to ensure the stability of the high-temperature gas-cooled reactor steam generator during operation, and to ensure uniform distribution of flow, a throttling assembly is installed at the inlet of each heat transfer pipe, and the inner diameter of the throttling hole of the throttling assembly is generally 2.5-3 mm. Because the throttling hole of the throttling assembly has a very small inner diameter, the corrosion products in the feedwater are easily deposited in the throttling hole and the heat transfer pipe when the feedwater flows through the throttling hole, which causes blockage and corrosion of the heat transfer pipe, and seriously affects the safe and stable operation of the high-temperature gas-cooled reactor. SUMMARY

[0003] Therefore, the technical problem to be solved by the present application is to overcome the defects of the high-temperature gas-cooled reactor steam generator, because the throttling hole of the throttling assembly has a very small inner diameter, the corrosion products in the feedwater are easily deposited in the throttling hole and the heat transfer pipe when the feedwater flows through the throttling hole, which causes blockage, and seriously affects the safe and stable operation of the high-temperature gas-cooled reactor.

[0004] In order to solve the above problems, the present application provides a feedwater treatment method for a high-temperature gas-cooled reactor steam generator, comprising:

[0005] Before the high-temperature gas-cooled reactor is started, the feedwater of the steam generator is treated by using a first reducing full evaporation treatment method;

[0006] During the starting of the high-temperature gas-cooled reactor, the feedwater of the steam generator is treated by using a second reducing full evaporation treatment method;

[0007] When the high-temperature gas-cooled reactor is running, and after the two-phase flow transition is completed on the secondary side of the steam generator, the feedwater of the steam generator is treated by using an oxidizing full evaporation treatment method;

[0008] When the high-temperature gas-cooled reactor is running stably, the feedwater of the steam generator is treated by using an oxygenation treatment method;

[0009] During the stopping of the high-temperature gas-cooled reactor, and before the two-phase flow is entered on the secondary side of the steam generator, the feedwater of the steam generator is treated by using a second reducing full evaporation treatment method;

[0010] In the shutdown stage of the high-temperature gas cooled reactor, and after the two-phase flow transition into liquid phase is completed on the secondary side of the steam generator, a third reducing full volatilization treatment method is used to treat the feedwater of the steam generator;

[0011] In the non-planned shutdown stage of the high-temperature gas cooled reactor, hydrazine and ammonia water are added to the feedwater of the steam generator.

[0012] Optionally, the first reducing full volatilization treatment method and the second reducing full volatilization treatment method both refer to adding ammonia water and hydrazine to the feedwater of the steam generator.

[0013] Optionally, in the first reducing full volatilization treatment method, the pH of the feedwater of the steam generator ranges from 9.3 to 9.8, and the concentration of hydrazine is greater than or equal to 100 μg / L.

[0014] Optionally, in the second reducing full volatilization treatment method, the pH of the feedwater of the steam generator ranges from 9.6 to 9.8, the concentration of hydrazine ranges from 30 μg / L to 100 μg / L, and the dissolved oxygen concentration of the feedwater of the steam generator is less than or equal to 3 μg / L.

[0015] Optionally, the oxidizing full volatilization treatment method refers to adding only ammonia water to the feedwater of the steam generator; in the oxidizing full volatilization treatment method, the pH of the feedwater of the steam generator ranges from 9.3 to 9.8, and the dissolved oxygen concentration of the feedwater of the steam generator is less than or equal to 10 μg / L.

[0016] Optionally, the third reducing full volatilization treatment method refers to adding ammonia water and hydrazine to the feedwater of the steam generator; in the third reducing full volatilization treatment method, the pH of the feedwater of the steam generator ranges from 9.6 to 10, and the concentration of hydrazine is greater than or equal to 100 μg / L.

[0017] Optionally, the oxygenation treatment method refers to adding ammonia water and oxygen to the feedwater of the steam generator; in the oxygenation treatment method, the pH of the feedwater of the steam generator ranges from 9.0 to 9.3, and the dissolved oxygen concentration of the feedwater of the steam generator ranges from 10 μg / L to 30 μg / L.

[0018] Optionally, in the first reducing full volatilization treatment method, the second reducing full volatilization treatment method, the oxidizing full volatilization treatment method, and the third reducing full volatilization treatment method, the feedwater in the downcomer of the deaerator is treated; in the oxygenation treatment method, oxygenation is performed on both the downcomer of the deaerator and the high-pressure heater side, and the deaerator is connected to the steam generator of the high-temperature gas cooled reactor.

[0019] Optionally, in the non-planned shutdown stage of the high-temperature gas cooled reactor, the pH of the feedwater of the steam generator is greater than or equal to 9.6, and the concentration of hydrazine is greater than or equal to 100 μg / L.

[0020] Optionally, in the second reducing full evaporation treatment mode, the hydrogen conductivity of the feed water of the steam generator at 25 degrees Celsius is ≤0.15 μS / cm, the chlorine ion concentration, the sulfate ion concentration, the copper concentration, and the sodium concentration of the feed water of the steam generator are all ≤2 μg / L, the silicon dioxide concentration and the iron concentration of the feed water of the steam generator are both ≤5 μg / L, and the TOC concentration of the feed water of the steam generator is ≤100 μg / L.

[0021] The above technical solution of the present application has the following advantages compared with the prior art:

[0022] 1. The feed water treatment method of the steam generator of the high-temperature gas cooled reactor provided by the present application comprises: before starting the high-temperature gas cooled reactor, treating the feed water of the steam generator by using a first reducing full evaporation treatment mode; during starting the high-temperature gas cooled reactor, treating the feed water of the steam generator by using a second reducing full evaporation treatment mode; when the high-temperature gas cooled reactor is running, and after completing the two-phase flow transition of the secondary side of the steam generator, treating the feed water of the steam generator by using an oxidizing full evaporation treatment mode; when the high-temperature gas cooled reactor is stably running, treating the feed water of the steam generator by using an oxygen addition treatment mode; during stopping the high-temperature gas cooled reactor, and before entering the two-phase flow of the secondary side of the steam generator, treating the feed water of the steam generator by using the second reducing full evaporation treatment mode; during the stopping running stage of the high-temperature gas cooled reactor, and after completing the two-phase flow transition of the secondary side of the steam generator to become a liquid phase, treating the feed water of the steam generator by using a third reducing full evaporation treatment mode; during the non-planned shutdown stage of the high-temperature gas cooled reactor, adding hydrazine and ammonia water into the feed water of the steam generator; the present application adopts the above technical solution, selects a suitable feed water treatment mode in different states of the high-temperature gas cooled reactor, reduces the generation of corrosion products, prevents and slows down the deposition of corrosion products in the throttle hole and the heat transfer tube, effectively controls the corrosion degree of the heat transfer tube of the steam generator, and has great significance for the safe and stable running of the high-temperature gas cooled reactor.

[0023] 2. The first reducing full evaporation treatment mode and the second reducing full evaporation treatment mode both refer to adding ammonia water and hydrazine into the feed water of the steam generator; the present application adopts the above technical solution, specifically limits the first reducing full evaporation treatment mode and the second reducing full evaporation treatment mode, and ensures that the feed water does not use the oxidizing full evaporation treatment mode or the oxygen addition treatment mode during the starting process of the high-temperature gas cooled reactor.

[0024] 3. The third reducing full volatilization treatment mode of the application refers to adding ammonia water and hydrazine into the feed water of the steam generator; under the third reducing full volatilization treatment mode, the pH of the feed water of the steam generator ranges from 9.6 to 10, and the concentration of the hydrazine is greater than or equal to 100 μg / L; the application adopts the above technical scheme to ensure that the feed water does not adopt the oxidizing full volatilization treatment mode or the oxygen adding treatment mode during the shutdown stage of the high temperature gas cooled reactor. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0026] Figure 1 The flow step schematic diagram of the feed water treatment method of the high temperature gas cooled reactor steam generator provided in the embodiments of the application. DETAILED DESCRIPTION

[0027] The technical solutions of the application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are some of the embodiments of the application, rather than all the embodiments. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0028] In the description of the application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0029] In the description of the application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0030] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] For high-temperature gas-cooled reactor steam generators, accelerated corrosion from feedwater flow leads to pipe corrosion and high iron concentration. Increasing the dissolved oxygen concentration in the feedwater can, to some extent, inhibit accelerated corrosion. Using an oxidizing total volatile treatment method (AVT(O)) or an oxygenation treatment method (OT) can alter the structure and morphology of the oxide film on the metal surface, making the oxide film more robust and dense, slowing down or even preventing accelerated corrosion from feedwater flow, and reducing the migration and deposition of corrosion products. The superheated section of the heat transfer tubes in the high-temperature gas-cooled reactor steam generator uses Incoloy 800H heat-resistant alloy material. During the start-up and shutdown of the high-temperature gas-cooled reactor, the Incoloy 800H heat-resistant alloy material is in the liquid phase. During this stage, the feedwater cannot be treated using AVT(O) or OT; a suitable feedwater treatment method must be selected based on the operating conditions of the steam generator. During shutdown, as the unit load decreases, the superheated section of the steam generator will transition from the steam phase to the water phase. Salt deposited on the tube walls dissolves in the water, causing salt re-dissolution and leading to an increase in localized salt concentration in the water. To inhibit corrosion of the steam generator during shutdown, the feedwater treatment method needs to be adjusted. Based on these considerations, this application proposes a feedwater treatment method for a high-temperature gas-cooled reactor steam generator.

[0032] like Figure 1 A specific embodiment of the feedwater treatment method for the high-temperature gas-cooled reactor steam generator shown includes the following steps:

[0033] S1. During the secondary loop flushing process before the high-temperature gas-cooled reactor starts up, the feedwater of the steam generator is treated using a first reducing and volatile treatment method. Specifically, the first reducing and volatile treatment method involves adding ammonia and hydrazine to the feedwater of the steam generator. Under this method, the pH range of the feedwater is 9.3–9.8, and the concentration of hydrazine is ≥100 μg / L.

[0034] S2, in the process of increasing power in the start-up stage of the high temperature gas cooled reactor, the feed water of the steam generator is treated by using a second reducing full evaporation treatment mode. Specifically, the second reducing full evaporation treatment mode refers to adding ammonia water and hydrazine into the feed water of the steam generator to adjust the water quality of the feed water and reduce the dosage of hydrazine; under the second reducing full evaporation treatment mode, the pH of the feed water of the steam generator ranges from 9.6 to 9.8, the concentration of hydrazine ranges from 30 μg / L to 100 μg / L, and the dissolved oxygen concentration of the feed water of the steam generator is ≤3 μg / L; the hydrogen conductivity of the feed water of the steam generator at 25 degrees Celsius is ≤0.15 μS / cm, the concentration of chloride ions, the concentration of sulfate ions, the concentration of copper and the concentration of sodium in the feed water of the steam generator are all ≤2 μg / L, the concentration of silicon dioxide and the concentration of iron in the feed water of the steam generator are both ≤5 μg / L, and the TOC concentration of the feed water of the steam generator is ≤100 μg / L.

[0035] S3, when the high temperature gas cooled reactor is in stable operation and the two-phase flow transition on the secondary side of the steam generator is completed, the feed water of the steam generator is treated by using an oxidizing full evaporation treatment mode. Specifically, the oxidizing full evaporation treatment mode refers to adding only ammonia water into the feed water of the steam generator and stopping adding hydrazine; under the oxidizing full evaporation treatment mode, the pH of the feed water of the steam generator ranges from 9.3 to 9.8, and the dissolved oxygen concentration of the feed water of the steam generator is ≤10 μg / L.

[0036] S4, when the high temperature gas cooled reactor is in stable operation and the hydrogen conductivity of the feed water reaches 0.10 μS / cm and shows a downward trend, the feed water of the steam generator is treated by using an oxygen adding treatment mode to increase the dissolved oxygen content of the feed water. Specifically, the oxygen adding treatment mode refers to adding ammonia water and oxygen into the feed water of the steam generator; compared with steps S1, S2 and S3, the concentration of added ammonia water is reduced. Under the oxygen adding treatment mode, the pH of the feed water of the steam generator ranges from 9.0 to 9.3, and the dissolved oxygen concentration of the feed water of the steam generator ranges from 10 μg / L to 30 μg / L.

[0037] S5, in the process of stopping operation and reducing power of the high temperature gas cooled reactor and before the two-phase flow on the secondary side of the steam generator, the oxygen adding is stopped, the feed water of the steam generator is treated by using the second reducing full evaporation treatment mode, and the concentration of added ammonia water is increased.

[0038] S6, in the shutdown stage of the high temperature gas cooled reactor, and after the two-phase flow transition into liquid phase is completed on the secondary side of the steam generator, a third reducing full volatilization treatment method is used to treat the feed water of the steam generator. Specifically, the third reducing full volatilization treatment method refers to adding ammonia water and hydrazine into the feed water of the steam generator; and increasing the concentration of the ammonia water and hydrazine. Under the third reducing full volatilization treatment method, the pH of the feed water of the steam generator ranges from 9.6 to 10, and the concentration of the hydrazine is greater than or equal to 100 μg / L.

[0039] S7, in the non-planned shutdown stage of the high temperature gas cooled reactor, oxygen addition is immediately stopped, hydrazine and ammonia water are added into the feed water of the steam generator, and the concentration of the ammonia water is increased. Specifically, the pH of the feed water of the steam generator is greater than or equal to 9.6, and the concentration of the hydrazine is greater than or equal to 100 μg / L.

[0040] Specifically, in the first reducing full volatilization treatment method, the second reducing full volatilization treatment method, the oxidizing full volatilization treatment method and the third reducing full volatilization treatment method, the feed water in the downcomer of the deaerator is treated; in the oxygen addition treatment method, oxygen is added into the downcomer of the deaerator and the high pressure heater side, and the deaerator is connected with the steam generator of the high temperature gas cooled reactor.

[0041] Obviously, the above embodiments are only examples for clearly illustrating the present application, and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments do not need to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method of feedwater treatment for a high temperature gas cooled reactor steam generator, characterized by, The application relates to a method for treating feedwater of a steam generator of a high-temperature gas cooled reactor. Before the high-temperature gas cooled reactor is started, the feedwater of the steam generator is treated by using a first reducing full evaporation treatment mode; During the starting of the high-temperature gas cooled reactor, the feedwater of the steam generator is treated by using a second reducing full evaporation treatment mode; When the high-temperature gas cooled reactor is running and after the two-phase flow transition on the secondary side of the steam generator is completed, the feedwater of the steam generator is treated by using an oxidizing full evaporation treatment mode; When the high-temperature gas cooled reactor is stably running, the feedwater of the steam generator is treated by using an oxygen adding treatment mode; During the stopping of the high-temperature gas cooled reactor, before the two-phase flow on the secondary side of the steam generator is entered, the feedwater of the steam generator is treated by using the second reducing full evaporation treatment mode; During the stopping of the high-temperature gas cooled reactor, after the two-phase flow transition on the secondary side of the steam generator is completed and becomes liquid phase, the feedwater of the steam generator is treated by using a third reducing full evaporation treatment mode; During the non-planned shutdown of the high-temperature gas cooled reactor, hydrazine and ammonia water are added into the feedwater of the steam generator.

2. The high temperature gas cooled reactor steam generator feedwater treatment method according to claim 1, characterized by, The first reducing full evaporation treatment mode and the second reducing full evaporation treatment mode both refer to adding ammonia water and hydrazine into the feedwater of the steam generator.

3. The high temperature gas cooled reactor steam generator feedwater treatment method according to claim 2, characterized by, In the first reducing full evaporation treatment mode, the pH of the feedwater of the steam generator ranges from 9.3 to 9.8, and the concentration of the hydrazine is greater than or equal to 100 mu g / L.

4. The high temperature gas cooled reactor steam generator feedwater treatment method according to claim 2, characterized by, In the second reducing full evaporation treatment mode, the pH of the feedwater of the steam generator ranges from 9.6 to 9.8, the concentration of the hydrazine ranges from 30 mu g / L to 100 mu g / L, and the dissolved oxygen concentration of the feedwater of the steam generator is less than or equal to 3 mu g / L.

5. The high temperature gas cooled reactor steam generator feedwater treatment method according to any one of claims 1 to 4, characterized by, The oxidizing full evaporation treatment mode refers to adding only ammonia water into the feedwater of the steam generator; in the oxidizing full evaporation treatment mode, the pH of the feedwater of the steam generator ranges from 9.3 to 9.8, and the dissolved oxygen concentration of the feedwater of the steam generator is less than or equal to 10 mu g / L.

6. The high temperature gas cooled reactor steam generator feedwater treatment method according to any one of claims 1 to 4, characterized by, The third reducing full evaporation treatment mode refers to adding ammonia water and hydrazine into the feedwater of the steam generator; in the third reducing full evaporation treatment mode, the pH of the feedwater of the steam generator ranges from 9.6 to 10, and the concentration of the hydrazine is greater than or equal to 100 mu g / L.

7. The high temperature gas cooled reactor steam generator feedwater treatment method according to any one of claims 1 to 4, characterized by, The oxygen adding treatment mode refers to adding ammonia water and oxygen into the feedwater of the steam generator; in the oxygen adding treatment mode, the pH of the feedwater of the steam generator ranges from 9.0 to 9.3, and the dissolved oxygen concentration of the feedwater of the steam generator ranges from 10 mu g / L to 30 mu g / L.

8. The high temperature gas cooled reactor steam generator feedwater treatment method according to claim 7, characterized by, In the first reducing full evaporation treatment mode, the second reducing full evaporation treatment mode, the oxidizing full evaporation treatment mode and the third reducing full evaporation treatment mode, the feedwater in the descending pipe of the deaerator is treated; in the oxygen adding treatment mode, oxygen is added into the descending pipe of the deaerator and the steam side of the high-pressure heater, and the deaerator is connected with the steam generator of the high-temperature gas cooled reactor.

9. The high temperature gas cooled reactor steam generator feedwater treatment method according to any one of claims 1 to 4, characterized by, During the non-planned shutdown of the high-temperature gas cooled reactor, the pH of the feedwater of the steam generator is greater than or equal to 9.6, and the concentration of the hydrazine is greater than or equal to 100 mu g / L.

10. The high temperature gas cooled reactor steam generator feedwater treatment method according to any one of claims 1 to 4, characterized by, In the second reducing total evaporation treatment mode, the hydrogen conductivity of the feed water of the steam generator at 25 degrees Celsius is ≤0.15 μS / cm, the chlorine ion concentration, the sulfate ion concentration, the copper concentration, and the sodium concentration of the feed water of the steam generator are all ≤2 μg / L, the silicon dioxide concentration and the iron concentration of the feed water of the steam generator are both ≤5 μg / L, and the TOC concentration of the feed water of the steam generator is ≤100 μg / L.

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