Method for treating ultralimit problem of dissolved oxygen content in desalting and deoxidizing water tank of pressurized water reactor nuclear power station

Abstract

The invention particularly relates to a method for treating the problem of overrun of the content of dissolved oxygen in a desalting and deoxidizing water tank of a pressurized water reactor nuclear power plant. The method comprises the following steps: eliminating other reasons except for an overflow pipeline; closing a recirculation pipeline isolation valve of the drainage pump, and checking whether the problem is caused by an overflow pipeline or not; after the reason of the problem is determined to be the overflow pipeline, siphoning oxygen-containing water in the overflow pipeline through a water pumping pipeline or heating the overflow pipeline through a heat tracing band; and when a problem occurs again, checking whether the water pumping pipeline or the heat tracing belt works normally, if not, recovering the water pumping pipeline and / or the heat tracing belt to work normally, and if so, checking whether the desalting and deoxidizing water tank and the recirculation pipeline of the draining pump are abnormal. The problem that the dissolved oxygen content of the desalting and deoxidizing water tank exceeds the limit is solved, the treatment cost is low, the treatment effect is good, the treatment efficiency is high, the space needed by on-site implementation is small, and on-site implementation is easy.

Description

Technical Field

[0001] The invention relates to the technical field of treatment of excessive dissolved oxygen content in a desalting and deoxygenating water tank in the operation and commissioning phase of a reactor boron and water replenishment system of a pressurized water reactor nuclear power plant, and in particular to a treatment method for excessive dissolved oxygen content in a desalting and deoxygenating water tank in a pressurized water reactor nuclear power plant. Background Art

[0002] In a pressurized water reactor nuclear power plant, the reactor boron and water supply system is equipped with two desalinated and deoxygenated water tanks with a capacity of 300 cubic meters for storing desalinated and deoxygenated water; when the reactor primary loop coolant needs to be supplied with water, the reactor boron and water supply system takes desalinated and deoxygenated water from the desalinated and deoxygenated water tanks and supplies it to the chemical and volume control system.

[0003] The desalination and deoxygenation water tank is equipped with an overflow pipeline. The interface between the overflow pipeline and the desalination and deoxygenation water tank is at the bottom of the desalination and deoxygenation water tank. The other end of the overflow pipeline is directly connected to the atmosphere, so that the water in the overflow pipeline can directly contact the oxygen in the air. During the normal operation of the unit, the oxygen dissolved in the water in the overflow pipeline will enter the desalination and deoxygenation water tank when the water level of the desalination and deoxygenation water tank drops, causing the dissolved oxygen content in the desalination and deoxygenation water tank to exceed the limit.

[0004] The desalting and deoxygenating water tank does not have the deoxygenating capacity and once the dissolved oxygen content in the desalting and deoxygenating water tank exceeds the limit, the water can only be replaced, and the discharged water cannot be recycled, resulting in serious waste of water resources. At present, a small number of nuclear power plants in China have installed deoxygenation devices for desalting and deoxygenating water tanks to address this problem. The deoxygenation device can deoxygenate the water in the desalting and deoxygenating water tank when the dissolved oxygen content in the desalting and deoxygenating water tank exceeds the limit, avoiding the waste of water resources caused by water replacement and the problem of the unit being unable to replenish water and dilute the reactor primary circuit due to insufficient desalting and deoxygenating water.

[0005] Although adding a deoxygenation device can effectively solve the problem of excessive dissolved oxygen content in the desalination and deoxygenation tank, this method requires a large investment cost and plant space. Summary of the invention

[0006] One of the purposes of the present invention is to provide a method for treating the problem of excessive dissolved oxygen content in a desalting and deoxygenating water tank of a pressurized water reactor nuclear power plant, so as to solve the problem of waste of water resources caused by failure to treat the problem of excessive dissolved oxygen content in the desalting and deoxygenating water tank, achieve treatment of the problem of excessive dissolved oxygen content in the desalting and deoxygenating water tank, and avoid waste of water resources.

[0007] The second purpose of the present invention is to provide a method for treating the problem of excessive dissolved oxygen content in the desalting and deoxygenating water tank of a pressurized water reactor nuclear power plant, so as to solve the problems of high treatment cost and large space required for on-site implementation when installing a deoxygenating device in the desalting and deoxygenating water tank to treat the problem of excessive dissolved oxygen content in the desalting and deoxygenating water tank. The method has the characteristics of low treatment cost, good treatment effect, high treatment efficiency, small space required for on-site implementation and simple on-site implementation.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant comprises the following steps:

[0010] Step 101: When the dissolved oxygen content in the desalination and deoxygenation water tank exceeds the limit during the operation of the pressurized water reactor nuclear power plant, check and eliminate other causes of the dissolved oxygen content in the desalination and deoxygenation water tank other than the overflow pipeline;

[0011] Step 102, close the isolation valve of the recirculation pipeline of the drainage pump, and check whether the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank is the overflow pipeline;

[0012] Step 103, after determining that the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank is the overflow pipeline, siphon the oxygenated water in the overflow pipeline through the pumping pipeline or heat the overflow pipeline through the heating tape;

[0013] Step 104: During the operation phase of the pressurized water reactor nuclear power plant, if the dissolved oxygen content in the desalination and deoxygenation water tank exceeds the limit again, check whether the pumping pipeline or the heating belt is working properly;

[0014] If not, restore the pumping pipeline and / or heating cable to normal operation;

[0015] If normal, check whether there is any abnormality in the recirculation pipeline of the desalination and deoxygenation water tank and the drain pump.

[0016] As one of the feasible ways, in step 1, other reasons for the excessive dissolved oxygen content in the desalination and deoxygenation tank besides the overflow line include:

[0017] a. The valve on the top of the desalination and deoxygenation tank is leaking or the capsule is damaged;

[0018] b. The sealing ring in the middle of the desalination and deoxygenation water tank leaks;

[0019] c. The drain valve or instrument valve at the bottom of the desalination and deoxygenation water tank is leaking;

[0020] d. There is a leak in the recirculation pipeline of the drainage pump at the bottom of the desalination and deoxygenation tank;

[0021] The cause of the problem of excessive dissolved oxygen content in the desalination and deoxygenation water tank was eliminated through maintenance.

[0022] As one of the achievable methods, in step 102, if any of the following conditions is met, it is determined that the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank is the overflow pipeline:

[0023] Condition 1: When the water level in the desalination and deoxygenation water tank does not change, the dissolved oxygen content in the desalination and deoxygenation water tank does not change; the drainage pump is running (20-30)m 3 / h of drainage, the dissolved oxygen content in the desalination and deoxygenation tank increases;

[0024] Condition 2: The problem of excessive dissolved oxygen content in the desalination and deoxygenation tank occurs in winter.

[0025] As one possible implementation method, when it is determined through condition one that the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank is the overflow line, oxygenated water in the overflow line is siphoned through a pumping line.

[0026] As one of the achievable methods, a water pumping pipeline is composed of a transparent hose and a stop valve matched with the transparent hose; siphoning oxygenated water in an overflow pipeline through the water pumping pipeline includes the following steps:

[0027] One end of the transparent hose is inserted from the top of the overflow pipeline into the middle of the overflow pipeline, and the other end is connected to the pit in the room where the desalination and deoxygenation water tank is located; the stop valve 7 is seamlessly fitted on the transparent hose on the pit side;

[0028] Open the stop valve and use the vacuum equipment to pump water downstream of the stop valve of the transparent hose to create a siphon in the transparent hose, and pump the oxygenated water in the overflow pipeline to the pit in the plant where the desalination and deoxygenation water tank is located.

[0029] As one achievable manner, the transparent hose is inserted into the middle of the overflow pipeline from the opening of the elbow at the top of the overflow pipeline.

[0030] As one of the feasible ways, after it is determined through condition 2 that the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank is the overflow pipeline, the overflow pipeline is heated by a heating tape.

[0031] As one of the feasible ways, a heating tape is installed on the overflow pipeline from the bottom to two-thirds of the height of the overflow pipeline. The power of the heating tape needs to ensure that the temperature of the water in the overflow pipeline is (30-35)°C.

[0032] As one possible implementation method, step 104, checking whether there is an abnormality in the desalination and deoxygenation water tank, includes the following steps:

[0033] 1. If there is no water supply to the desalination and deoxygenation water tank, drain the desalination and deoxygenation water tank, and check the valve and capsule on the top of the desalination and deoxygenation water tank and the sealing ring in the middle of the desalination and deoxygenation water tank;

[0034] 2. If the desalination and deoxygenation water tank is supplying water, close the isolation valve of the recirculation pipeline of the drainage pump to ensure that the water at the outlet of the drainage pump will not return to the desalination and deoxygenation water tank, and eliminate the relationship between the excessive dissolved oxygen content in the desalination and deoxygenation water tank and the recirculation pipeline of the drainage pump;

[0035] After closing the isolation valve of the drainage pump's recirculation pipeline, observe for one day to confirm that the dissolved oxygen content in the desalination and deoxygenation water tank is no longer over the limit. This means that the over-limit problem of dissolved oxygen content in the desalination and deoxygenation water tank is related to the drainage pump's recirculation pipeline. Directly inspect the drainage pump's recirculation pipeline.

[0036] 3. When the dissolved oxygen content in the desalination and deoxygenation water tank is 100ppb, fill and drain the desalination and deoxygenation water tank;

[0037] 4. Use a hose to connect the gooseneck pipe on the top of the desalination and deoxygenation water tank to pump water, and continue the pumping operation during the filling and drainage operation of the desalination and deoxygenation water tank;

[0038] 5. Use the drain valve at the bottom of the desalting and deoxygenating water tank to drain the water. The drainage rate should be within 1m / h. During the drainage period, connect the dissolved oxygen meter on site to continuously monitor the change trend of the dissolved oxygen content in the desalting and deoxygenating water tank to the water level of the desalting and deoxygenating water tank;

[0039] 6. If the dissolved oxygen content in the desalting and deoxygenating water tank remains unchanged as the water level in the desalting and deoxygenating water tank drops, it proves that there is no abnormality in the valve and capsule at the top of the desalting and deoxygenating water tank and the sealing ring in the middle of the desalting and deoxygenating water tank. The reason for the excessive dissolved oxygen content in the desalting and deoxygenating water tank is that the oxygenated water in the overflow pipeline enters the desalting and deoxygenating water tank or oxygen enters the desalting and deoxygenating water tank through the capsule at the top of the desalting and deoxygenating water tank;

[0040] 7. If the dissolved oxygen content in the desalting and deoxygenating water tank exceeds the limit during the drainage of the desalting and deoxygenating water tank, check the valve and capsule on the top of the desalting and deoxygenating water tank and the sealing ring in the middle of the desalting and deoxygenating water tank when the water level in the desalting and deoxygenating water tank reaches 5m;

[0041] After the inspection is completed, the water level in the desalination and deoxygenation water tank is drained to 1m, and then the desalination and deoxygenation water tank is filled and drained;

[0042] During the filling and draining of the desalination and deoxygenation water tank, the overflow pipeline and gooseneck pipe pumping operations are continuously carried out, and the dissolved oxygen content in the desalination and deoxygenation water tank is monitored at the same time.

[0043] As one possible implementation method, step 104, checking whether there is an abnormality in the recirculation pipeline of the drainage pump, includes the following steps:

[0044] 1. The phenomenon of oxygen leakage in the recirculation pipeline of the drainage pump is that the dissolved oxygen content in the desalination and deoxygenation water tank exceeds the limit. After closing the isolation valve of the recirculation pipeline of the drainage pump, the dissolved oxygen content in the desalination and deoxygenation water tank no longer exceeds the limit;

[0045] 2. Flush the drainage pump to discharge the oxygenated water in the pump cavity and some pipelines of the drainage pump;

[0046] 3. Tighten the flange, diaphragm valve and instrument interface on the recirculation pipeline of the drainage pump, and wrap the film;

[0047] 4. Monitor the dissolved oxygen content of the recirculation line of the drainage pump through a dissolved oxygen meter and manually measure the oxygen content of the REA water tank;

[0048] 5. By observing the changing trend of the dissolved oxygen content in the recirculation pipeline of the drainage pump during the startup of the drainage pump, determine whether there is a leak in the recirculation pipeline of the drainage pump; if the dissolved oxygen content in the recirculation pipeline of the drainage pump does not change, it is determined that there is no leak in the recirculation pipeline of the drainage pump, and the recirculation pipeline isolation valve of the drainage pump is opened.

[0049] Beneficial technical effects of the present invention:

[0050] The method for treating the problem of excessive dissolved oxygen content in a desalting and deoxygenating water tank of a pressurized water reactor nuclear power plant of the present invention rapidly suppresses oxygen in the air from entering the desalting and deoxygenating water tank by adding a pumping pipeline or a heating belt to an overflow pipeline, rapidly treats the problem of excessive dissolved oxygen in the desalting and deoxygenating water tank, can immediately treat the problem when the excessive dissolved oxygen content in the desalting and deoxygenating water tank is found during the operation of the pressurized water reactor nuclear power plant, and can complete the treatment within 3-5 hours of the occurrence of the problem at the earliest, thereby avoiding the problem from worsening and affecting the safe operation of the unit, and having good treatment effect and high treatment efficiency; treating the problem of excessive dissolved oxygen content in the desalting and deoxygenating water tank by adding a pumping pipeline or a heating belt to an overflow pipeline, requires little space for on-site implementation, is simple to implement on-site, can be assembled flexibly, and does not require subsequent maintenance work; can reduce the discharge of 100 cubic meters of desalting and deoxygenating water each time while achieving the same treatment effect, thereby reducing water resource waste, and saving energy and reducing emissions; can reduce the treatment cost of 4 million yuan each time while achieving the same treatment effect, and has low treatment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 A schematic structural diagram of an embodiment of a desalination and deoxygenation water tank for a pressurized water reactor nuclear power plant;

[0052] Figure 2 The present invention is a schematic diagram of an embodiment of a method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant.

[0053] In the figure, 1. valve; 2. desalination and deoxygenation water tank; 3. overflow pipeline; 4. drainage pump; 5. heating belt; 6. transparent hose; 7. stop valve; 8. pit. DETAILED DESCRIPTION

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0055] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0056] See also Figure 1 In a pressurized water reactor nuclear power plant, a deoxygenated and desalted water tank 2 is provided with a capsule and a valve 1 at the top, a sealing ring in the middle, a drainage pump 4 at the bottom, and an overflow pipeline 3 at the bottom of the side.

[0057] See also Figure 2 This embodiment provides a method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant, comprising the following steps:

[0058] Step 101, when the dissolved oxygen content in the desalination and deoxygenation water tank 2 exceeds the limit during the operation phase of the pressurized water reactor nuclear power plant, check and eliminate other causes of the dissolved oxygen content in the desalination and deoxygenation water tank 2 except for the overflow pipeline 3;

[0059] Step 102, close the recirculation pipeline isolation valve of the drainage pump 4 to ensure that the water at the outlet of the drainage pump 4 will not return to the desalination and deoxygenation water tank 2, and check whether the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank 2 is the overflow pipeline 3;

[0060] Step 103: after determining that the cause of the excessive dissolved oxygen content in the desalted and deoxygenated water tank 2 is the overflow pipeline 3, siphon the oxygenated water in the overflow pipeline 3 through the pumping pipeline, thereby preventing the oxygenated water in the overflow pipeline 3 from entering the desalted and deoxygenated water tank 2; or heat the overflow pipeline 3 through the heating belt 5, thereby reducing the oxygenated water content in the overflow pipeline 3;

[0061] Step 104: During the operation phase of the pressurized water reactor nuclear power plant, if the dissolved oxygen content in the desalination and deoxygenation water tank 2 exceeds the limit again, check whether the pumping pipeline or the heating belt is working properly;

[0062] If it is not normal, restore the pumping pipeline and or heating cable 5 until it works normally;

[0063] If normal, check whether there is any abnormality in the recirculation pipeline of the desalination and deoxygenation water tank 2 and the drainage pump 4.

[0064] In this embodiment, as one of the achievable methods, in step 1, the problem of excessive dissolved oxygen content in the desalination and deoxygenation water tank 2 may be caused by other reasons besides the overflow line 3:

[0065] a. The valve 1 on the top of the desalination and deoxygenation water tank 2 leaks or the capsule is damaged;

[0066] b. The sealing ring in the middle of desalination and deoxygenation water tank 2 leaks;

[0067] c. The drain valve or instrument valve at the bottom of desalination and deoxygenation water tank 2 is leaking;

[0068] d. There is a leak in the recirculation pipeline of the drainage pump 4 at the bottom of the desalination and deoxygenation water tank 2;

[0069] The cause ad of the problem of excessive dissolved oxygen content in desalination and deoxygenation water tank 2 was eliminated through maintenance.

[0070] According to the structure of the desalting and deoxygenating water tank 2, the inventors analyzed the reasons for the excessive dissolved oxygen content in the desalting and deoxygenating water tank 2:

[0071] a. The valve 1 on the top of the desalting and deoxygenating water tank 2 leaks or the capsule is damaged. When this problem occurs, during the drainage of the desalting and deoxygenating water tank 2, the dissolved oxygen content of the desalting and deoxygenating water tank 2 gradually increases as the water level of the desalting and deoxygenating water tank 2 decreases, and the dissolved oxygen content of the desalting and deoxygenating water tank 2 even reaches the ppm level;

[0072] b. The middle sealing ring of the desalting and deoxygenating water tank 2 leaks. When this problem occurs, the dissolved oxygen content of the desalting and deoxygenating water tank 2 first rises and then falls during the drainage period;

[0073] c. The drain valve or instrument valve at the bottom of the desalting and deoxygenating water tank 2 leaks. When this problem occurs, the dissolved oxygen content in the desalting and deoxygenating water tank 2 gradually decreases during the drainage of the desalting and deoxygenating water tank 2, and even gradually reaches a qualified level with the increase of drainage volume;

[0074] d. There is leakage in the recirculation pipeline of the drainage pump 4 at the bottom of the desalination and deoxygenation water tank 2. If the drainage pump 4 at the bottom of the desalination and deoxygenation water tank 2 has been overhauled, there may be leakage in the flange, diaphragm valve and instrument interface on the recirculation pipeline of the drainage pump 4. When this problem occurs, it can be confirmed by closing the isolation valve of the recirculation pipeline of the drainage pump 4 at the bottom of the desalination and deoxygenation water tank 2;

[0075] e. The capsule on the top of the desalting and deoxygenating water tank 2 leaks, and oxygen enters the desalting and deoxygenating water tank 2 through the capsule. When this problem occurs, a thorough dynamic water change can be performed after the desalting and deoxygenating water tank 2 has been running for a certain period of time;

[0076] f. The oxygenated water in the overflow pipeline 3 at the bottom of the side of the desalting and deoxygenating water tank 2 enters the desalting and deoxygenating water tank 2. When this problem occurs, the oxygenated water in the overflow pipeline 3 enters the desalting and deoxygenating water tank 2 during the filling and drainage of the desalting and deoxygenating water tank 2.

[0077] Reason e has little impact on the problem of excessive dissolved oxygen content in the desalting and deoxygenating water tank 2 and can be basically ignored. Reason ad is less likely to occur under normal operation and maintenance of the desalting and deoxygenating water tank 2, and its occurrence is often accompanied by leakage of the desalting and deoxygenating water tank 2. Inspection personnel or maintenance personnel can easily find these reasons when inspecting or checking the desalting and deoxygenating water tank 2, and can eliminate the impact of these reasons on the problem of excessive dissolved oxygen content in the desalting and deoxygenating water tank 2 through simple maintenance.

[0078] Reason f contributes most to the problem of excessive dissolved oxygen content in the desalting and deoxygenating water tank 2; the overflow pipeline 3 is in direct contact with the air, and the oxygen in the air dissolves in the water in the overflow pipeline 3; the overflow pipeline 3 is connected to the bottom of the side of the desalting and deoxygenating water tank 2. When the first circuit of the reactor needs to be replenished or replaced, the water level of the desalting and deoxygenating water tank 2 drops, and the oxygen-containing water in the overflow pipeline 3 enters the desalting and deoxygenating water tank 2.

[0079] Reason f is particularly evident when the water level in the desalination and deoxygenation water tank 2 is low and the water flow is large or in winter. Since reason f cannot be directly checked, every time the dissolved oxygen content in the desalination and deoxygenation water tank 2 exceeds the limit, the desalination and deoxygenation water tank 2 needs to be thoroughly inspected to determine whether the problem of excessive dissolved oxygen in the desalination and deoxygenation water tank 2 is caused by reason f.

[0080] In this embodiment, as one of the achievable methods, in step 102, if any of the following conditions is met, it is determined that the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank 2 is the overflow pipeline 3:

[0081] Condition 1: When the water level in the desalination and deoxygenation water tank 2 does not change, the dissolved oxygen content in the desalination and deoxygenation water tank 2 does not change; the drainage pump 4 is running at (20-30) m 3 After the high flow rate of / h is discharged, the dissolved oxygen content in the desalination and deoxygenation tank 2 increases;

[0082] Condition 2: The problem of excessive dissolved oxygen content in desalination and deoxygenation tank 2 occurs in winter.

[0083] In this embodiment, as one of the achievable ways, after it is determined through condition 1 that the cause of the excessive dissolved oxygen content in the desalted and deoxygenated water tank 2 is the overflow pipeline 3, the oxygenated water in the overflow pipeline 3 is siphoned through the pumping pipeline, thereby preventing the oxygenated water in the overflow pipeline 3 from entering the desalted and deoxygenated water tank 2;

[0084] The water pumping pipeline is composed of a transparent hose 6 and a stop valve 7 matched with the transparent hose 6; the oxygenated water in the overflow pipeline 3 is siphoned through the water pumping pipeline, thereby preventing the oxygenated water in the overflow pipeline 3 from entering the desalination and deoxygenation water tank 2, including the following steps:

[0085] One end of the transparent hose 6 is inserted from the top of the overflow pipeline 3 into the middle of the overflow pipeline 3, and the other end is connected to the pit 8 in the room where the desalination and deoxygenation water tank 2 is located; the stop valve 7 is seamlessly fitted on the transparent hose 6 on the side of the pit;

[0086] Open the stop valve 7, and use the vacuum equipment to pump water downstream of the stop valve 7 of the transparent hose 6, so that a siphon is established in the transparent hose 6, and the oxygenated water in the overflow pipeline 3 is pumped to the pit 8 of the factory building where the desalination and deoxygenation water tank 2 is located.

[0087] In this embodiment, as one of the feasible ways, in order to prevent the pit 8 from overflowing, it is necessary to confirm that the drainage facilities of the pit 8 are available to ensure that the water in the pit 8 can be discharged in time.

[0088] In this embodiment, as one of the achievable ways, a dissolved oxygen meter is provided at the downstream outlet of the isolation valve 7 to measure the dissolved oxygen content of the discharged water.

[0089] In this embodiment, as one of the feasible ways, the vacuuming device is a vacuum pump, a peristaltic pump or a peristaltic sampling gun.

[0090] In this embodiment, as one of the feasible ways, the transparent hose is inserted into the middle of the overflow pipeline from the opening of the bend at the top of the overflow pipeline 3 .

[0091] In this embodiment, as one of the achievable ways, after it is determined through condition 2 that the cause of the excessive dissolved oxygen content in the desalted and deoxygenated water tank 2 is the overflow pipeline 3, the overflow pipeline 3 is heated by the heating belt 5, thereby reducing the oxygen-containing water content in the overflow pipeline 3;

[0092] A heating belt 5 is installed on the overflow pipeline 3 from the bottom to two-thirds of the height of the overflow pipeline 3. The power of the heating belt 5 needs to ensure that the temperature of the water in the overflow pipeline 3 is (30-35)°C.

[0093] In this embodiment, as one of the achievable methods, step 104, checking whether the desalination and deoxygenation water tank 2 has an abnormality, includes the following steps:

[0094] 1. If there is no water supply to the desalting and deoxygenating water tank 2, drain the desalting and deoxygenating water tank 2, and check the valve 1 and capsule on the top of the desalting and deoxygenating water tank 2 and the sealing ring in the middle of the desalting and deoxygenating water tank 2;

[0095] 2. If the desalination and deoxygenation water tank 2 is supplying water, close the isolation valve of the recirculation pipeline of the drainage pump 4 to ensure that the water at the outlet of the drainage pump 4 will not return to the desalination and deoxygenation water tank 2, and eliminate the relationship between the excessive dissolved oxygen content in the desalination and deoxygenation water tank 2 and the recirculation pipeline of the drainage pump 4;

[0096] After closing the isolation valve of the recirculation pipeline of the drainage pump 4, observe for one day to confirm that the dissolved oxygen content in the desalination and deoxygenation water tank 2 is no longer exceeded, then it is confirmed that the excessive dissolved oxygen content in the desalination and deoxygenation water tank 2 is related to the recirculation pipeline of the drainage pump 4, and the recirculation pipeline of the drainage pump 4 is directly inspected;

[0097] 3. When the dissolved oxygen content in the desalting and deoxygenating water tank 2 is 100 ppb, the desalting and deoxygenating water tank 2 is filled and drained;

[0098] 4. Use a hose to connect the gooseneck pipe on the top of the desalination and deoxygenation water tank 2 to pump water, and continue the pumping operation during the filling and drainage operation of the desalination and deoxygenation water tank 2;

[0099] 5. Use the drain valve at the bottom of the desalting and deoxygenating water tank 2 to drain the desalting and deoxygenating water tank 2. The drainage rate is within 1m / h. During the drainage, connect the dissolved oxygen meter on site to continuously monitor the change trend of the dissolved oxygen content in the desalting and deoxygenating water tank 2 to the water level of the desalting and deoxygenating water tank 2;

[0100] 6. If the dissolved oxygen content of the desalting and deoxygenating water tank 2 remains unchanged as the water level of the desalting and deoxygenating water tank 2 drops, it proves that there is no abnormality in the valve 1 and the capsule at the top of the desalting and deoxygenating water tank 2 and the sealing ring in the middle of the desalting and deoxygenating water tank 2. The reason for the excessive dissolved oxygen content in the desalting and deoxygenating water tank 2 is that the oxygenated water in the overflow pipeline 3 enters the desalting and deoxygenating water tank 2 or oxygen enters the desalting and deoxygenating water tank 2 through the capsule at the top of the desalting and deoxygenating water tank 2;

[0101] 7. If the dissolved oxygen content of the desalting and deoxygenating water tank 2 exceeds the limit during the drainage of the desalting and deoxygenating water tank 2, when the water level of the desalting and deoxygenating water tank 2 reaches 5m, check the valve and capsule at the top of the desalting and deoxygenating water tank 2 and the sealing ring in the middle of the desalting and deoxygenating water tank 2;

[0102] After the inspection is completed, the water level of the desalination and deoxygenation water tank 2 is drained to 1m, and then the desalination and deoxygenation water tank 2 is filled and drained;

[0103] During the filling and draining of the desalting and deoxygenating water tank 2, the overflow line 3 and the gooseneck pipe are continuously pumped, and the dissolved oxygen content of the desalting and deoxygenating water tank 2 is monitored at the same time.

[0104] In this embodiment, as one of the achievable methods, step 104, checking whether there is an abnormality in the recirculation pipeline of the drainage pump 4, includes the following steps:

[0105] 1. The phenomenon of oxygen leakage in the recirculation pipeline of the drainage pump 4 is that the dissolved oxygen content in the desalination and deoxygenation water tank 2 exceeds the limit. After closing the isolation valve of the recirculation pipeline of the drainage pump 4, the dissolved oxygen content in the desalination and deoxygenation water tank 2 is no longer exceeded;

[0106] 2. Flush the drainage pump 4 to discharge the oxygenated water in the pump cavity and part of the pipeline of the drainage pump 4;

[0107] 3. Tighten the flange, diaphragm valve and instrument interface on the recirculation pipeline of the drainage pump 4, and wrap the film;

[0108] 4. Monitor the dissolved oxygen content of the recirculation line of the drain pump 4 by using a dissolved oxygen meter and manually measure the oxygen content of the REA water tank;

[0109] 5. By observing the change trend of the dissolved oxygen content in the recirculation pipeline of the drainage pump 4 during the startup of the drainage pump 4, it is determined whether there is a leak in the recirculation pipeline of the drainage pump 4;

[0110] If the dissolved oxygen content of the recirculation line of the drainage pump 4 does not change, it is determined that there is no leakage in the recirculation line of the drainage pump 4, and the isolation valve of the recirculation line of the drainage pump 4 is opened.

[0111] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant, characterized in that: The steps include: Step 101: When the dissolved oxygen content in the desalting and deoxygenating water tank (2) exceeds the limit during the operation of the pressurized water reactor nuclear power plant, check other causes of the dissolved oxygen content in the desalting and deoxygenating water tank (2) other than the overflow pipeline (3) and eliminate them; Step 102, close the isolation valve of the recirculation pipeline of the drainage pump (4), and check whether the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank (2) is the overflow pipeline (3); Step 103, after determining that the cause of the excessive dissolved oxygen content in the desalted and deoxygenated water tank (2) is the overflow pipeline (3), siphon the oxygenated water in the overflow pipeline (3) through the pumping pipeline or heat the overflow pipeline (3) through the heating belt (5); Step 104: During the operation phase of the pressurized water reactor nuclear power plant, when the dissolved oxygen content in the desalination and deoxygenation water tank (2) exceeds the limit again, check whether the pumping pipeline or the heating belt is working properly; If not, restore the pumping line and / or heating cable (5) to normal operation; If normal, check whether there is any abnormality in the recirculation pipeline of the desalination and deoxygenation water tank (2) and the drainage pump (4).

2. The method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: In step 1, the other reasons for the excessive dissolved oxygen content in the desalting and deoxygenating water tank (2) besides the overflow pipeline (3) include: a. leakage of the top valve (1) of the desalting and deoxygenating water tank (2) or damage to the capsule; b. leakage of the middle sealing ring of the desalting and deoxygenating water tank (2); c. leakage of the bottom drain valve or instrument valve of the desalting and deoxygenating water tank (2); d. leakage of the recirculation pipeline of the drain pump (4) at the bottom of the desalting and deoxygenating water tank (2); the reasons ad for the excessive dissolved oxygen content in the desalting and deoxygenating water tank (2) are eliminated through maintenance.

3. The method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: Step 102, if any of the following conditions is met, it is determined that the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank (2) is the overflow pipeline (3): Condition 1: When the water level in the desalting and deoxygenating water tank (2) does not change, the dissolved oxygen content in the desalting and deoxygenating water tank (2) does not change; the drainage pump (4) is running for (20-30) m 3 After the water is discharged at a rate of / h, the dissolved oxygen content in the desalination and deoxygenation tank (2) increases; Condition 2: Desalination and deoxygenation water tank (2) The problem of excessive dissolved oxygen content occurs in winter.

4. The method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant according to claim 3 is characterized in that: When it is determined through condition 1 that the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank (2) is the overflow pipeline (3), the oxygenated water in the overflow pipeline (3) is siphoned through the pumping pipeline.

5. The method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant according to claim 4, characterized in that: The water pumping pipeline is composed of a transparent hose (6) and a stop valve (7) matched with the transparent hose (6); the oxygenated water in the overflow pipeline (3) is siphoned through the water pumping pipeline, comprising the following steps: One end of the transparent hose (6) is inserted from the top of the overflow pipeline (3) into the middle of the overflow pipeline (3), and the other end is connected to the pit (8) in the room where the desalination and deoxygenation water tank (2) is located; the stop valve (7) is seamlessly fitted on the transparent hose (6) on the side of the pit (8); The stop valve (7) is opened, and a water pumping operation is performed on the downstream of the stop valve (7) of the transparent hose (6) through a vacuum pumping device, so that a siphon is established in the transparent hose (6), and the oxygenated water in the overflow pipeline (3) is pumped to the pit (8) of the factory building where the desalination and deoxygenation water tank (2) is located.

6. The method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant according to claim 5, characterized in that: The transparent hose is inserted into the middle of the overflow pipeline (3) from the opening position of the bend pipe at the top of the overflow pipeline (3).

7. The method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant according to claim 3, characterized in that: When it is determined through condition 2 that the cause of the excessive dissolved oxygen content in the desalination and deoxygenation water tank (2) is the overflow pipeline (3), the overflow pipeline (3) is heated by the heating belt (5).

8. The method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant according to claim 7, characterized in that: A heating tape (5) is installed on the overflow pipeline (3) from the bottom to two-thirds of the height of the overflow pipeline (3). The power of the heating tape (5) needs to ensure that the temperature of the water in the overflow pipeline (3) is (30-35)°C.

9. The method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: Step 104, checking whether the desalination and deoxygenation water tank (2) has any abnormality, comprises the following steps: Step 1: If the desalting and deoxygenating water tank (2) is not supplied with water, the desalting and deoxygenating water tank (2) is drained, and at the same time, the valve (1) and the capsule at the top of the desalting and deoxygenating water tank (2) and the sealing ring in the middle of the desalting and deoxygenating water tank (2) are checked; Step 2: If the desalination and deoxygenation water tank (2) is supplying water, close the isolation valve of the recirculation pipeline of the drainage pump (4) to ensure that the water at the outlet of the drainage pump (4) will not return to the desalination and deoxygenation water tank (2), and eliminate the relationship between the excessive dissolved oxygen content in the desalination and deoxygenation water tank (2) and the recirculation pipeline of the drainage pump (4); After closing the isolation valve of the recirculation pipeline of the drainage pump (4) and observing for one day, if the dissolved oxygen content in the desalination and deoxygenation water tank (2) no longer exceeds the limit, it is confirmed that the excessive dissolved oxygen content in the desalination and deoxygenation water tank (2) is related to the recirculation pipeline of the drainage pump (4), and the recirculation pipeline of the drainage pump (4) is directly inspected; Step 3, when the dissolved oxygen content in the desalting and deoxygenating water tank (2) is 100 ppb, the desalting and deoxygenating water tank (2) is filled and drained; Step 4: Use a hose to connect the gooseneck pipe on the top of the desalination and deoxygenation water tank (2) to pump water, and continue the pumping operation during the filling and drainage operation of the desalination and deoxygenation water tank (2); Step 5, drain the desalting and deoxygenating water tank (2) using the drain valve at the bottom of the desalting and deoxygenating water tank (2), with the drainage rate being within 1 m / h. During the drainage, a dissolved oxygen meter is connected on site to continuously monitor the change trend of the dissolved oxygen content in the desalting and deoxygenating water tank (2) with respect to the water level in the desalting and deoxygenating water tank (2); Step 6: If the dissolved oxygen content in the desalting and deoxygenating water tank (2) remains unchanged as the water level in the desalting and deoxygenating water tank (2) decreases, it is proved that there is no abnormality in the valve (1) and the capsule at the top of the desalting and deoxygenating water tank (2) and the sealing ring in the middle of the desalting and deoxygenating water tank (2). The reason for the excessive dissolved oxygen content in the desalting and deoxygenating water tank (2) is that the oxygen-containing water in the overflow pipeline (3) enters the desalting and deoxygenating water tank (2) or oxygen enters the desalting and deoxygenating water tank (2) through the capsule at the top of the desalting and deoxygenating water tank (2); Step 7: If the dissolved oxygen content of the desalting and deoxygenating water tank (2) exceeds the limit during the drainage of the desalting and deoxygenating water tank (2), when the water level of the desalting and deoxygenating water tank (2) reaches 5 m, check the valve (1) and the capsule at the top of the desalting and deoxygenating water tank (2) and the sealing ring in the middle of the desalting and deoxygenating water tank (2); After the inspection is completed, the water level in the desalting and deoxygenating water tank (2) is drained to 1m, and then the desalting and deoxygenating water tank (2) is filled and drained; During the filling and draining of the desalting and deoxygenating water tank (2), the overflow pipeline (3) and the gooseneck pipe are continuously pumped, and the dissolved oxygen content in the desalting and deoxygenating water tank (2) is monitored at the same time.

10. The method for treating excessive dissolved oxygen content in a desalination and deoxygenation water tank of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: Step 104, checking whether the recirculation pipeline of the drainage pump (4) has any abnormality, comprises the following steps: Step 1: The phenomenon of oxygen leakage in the recirculation pipeline of the drainage pump (4) is that the dissolved oxygen content in the desalination and deoxygenation water tank (2) exceeds the limit. After closing the isolation valve of the recirculation pipeline of the drainage pump (4), the dissolved oxygen content in the desalination and deoxygenation water tank (2) no longer exceeds the limit. Step 2, flushing the drainage pump (4) to discharge the oxygenated water in the pump cavity and part of the pipeline of the drainage pump (4); Step 3, tighten the flange, diaphragm valve and instrument interface on the recirculation pipeline of the drainage pump (4), and wrap the film; Step 4, monitor the dissolved oxygen content of the recirculation line of the drainage pump (4) by a dissolved oxygen meter, and manually measure the oxygen content of the REA water tank; Step 5, by observing the change trend of the dissolved oxygen content in the recirculation pipeline of the drainage pump (4) during the startup of the drainage pump (4), it is determined whether there is a leak in the recirculation pipeline of the drainage pump (4); If the dissolved oxygen content of the recirculation line of the drainage pump (4) does not change, it is determined that there is no leakage in the recirculation line of the drainage pump (4), and the isolation valve of the recirculation line of the drainage pump (4) is opened.

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