Non-radioactive liquid waste discharge method for conventional island of nuclear power plant

Abstract

The present disclosure belongs to the technical field of nuclear power and specifically relates to a non-waste liquid discharge method for a conventional island of a nuclear power plant. The present disclosure is obtained by modifying the most suitable flow rate of the medium at the outlet of the nozzle of the recirculation pipeline and the insertion depth of the recirculation pipeline through the relationship constraint between the parameters of the non-waste liquid discharge system of the conventional island of the nuclear power plant and the circulating time, and further obtains the optimal circulating time in the verification process. The design has strong universality and is suitable for nuclear power plants at various stages. That is, a nuclear power plant under construction can be optimized according to the method, and a nuclear power plant in operation can be simply optimized and modified according to the method to achieve the effect.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power technology, specifically relating to a method for discharging non-radioactive liquid waste from the conventional island of a nuclear power plant. Background Technology

[0002] In related technologies, non-radical waste liquids from the conventional island of operating nuclear power units in my country are discharged in tanks. Before discharge, the waste liquid in the tank needs to be circulated to ensure that it is mixed evenly before chemical sampling and analysis. Only if the analysis results are qualified (meeting environmental protection requirements) can it be discharged into the environment.

[0003] During major overhauls of nuclear power plants, a large amount of non-radioactive liquid waste needs to be discharged from the conventional island. Due to increasingly stringent environmental regulations in recent years, the non-radioactive liquid waste from the conventional island must undergo a lengthy circulation process before discharge to ensure that all indicators of the discharged non-radioactive liquid meet environmental requirements. This requirement also extends the overhaul period for the conventional island. Significantly shortening the circulation time would shorten the overhaul period and generate more revenue for the power plant. Summary of the Invention

[0004] To overcome the problems existing in related technologies, a method for discharging non-radioactive liquid waste from the conventional island of a nuclear power plant is provided.

[0005] According to one aspect of the present disclosure, a method for discharging non-radiative waste liquid from the conventional island of a nuclear power plant is provided, the method comprising:

[0006] Step 1: Determine the parameters of the non-radioactive waste liquid discharge system of the conventional island of the nuclear power plant, including: the total water volume of the conventional island of the nuclear power plant is V1, the flow rate of the non-radioactive waste liquid transfer pump of the conventional island is Q1, the volume of a single storage tank of the non-radioactive waste liquid discharge system of the conventional island is V2, the total number of non-radioactive waste liquid storage tanks of the conventional island is n, the flow rate of the non-radioactive waste liquid discharge pump of the conventional island is Q2, and the circulation time before the non-radioactive waste liquid storage tank of the conventional island is T.

[0007] Step 2: Based on the parameters of the conventional island non-radioactive waste liquid discharge system of the nuclear power plant, determine the circulation time T. To ensure that the conventional island non-radioactive waste liquid discharge system can continuously receive the wastewater from the conventional island, T must satisfy the condition shown in Equation 1:

[0008]

[0009] Step 3, in the design of the conventional island non-discharge waste liquid discharge system, the discharge pump of the conventional island non-discharge waste liquid discharge system is usually used as the recirculation pump of the conventional island non-discharge waste liquid discharge system storage tank. Therefore, there is a relationship between T and the pump flow rate Q2 as shown in Equation 2:

[0010]

[0011] Where η represents the mixing efficiency of the device, and η is related to the height of the recirculation pipe inserted into the tank and whether there is a nozzle device in the tank.

[0012] Step 3: According to the requirements of the circulation time T shown in Equations 1 and 2, T is made to meet the requirements of Equations 1 and 2 by continuously correcting the structure of the nozzle and changing the flow rate of the medium at the nozzle outlet of the recirculation pipeline and the insertion depth of the recirculation pipeline.

[0013] Step 4: Based on the condition that T satisfies the requirements of Equation 1 and Equation 2, obtain the nozzle structure and recirculation pipeline insertion depth, and modify the on-site recirculation pipeline.

[0014] In one possible implementation, the method further includes:

[0015] Step 5: Test and verify the modified pipeline. Add water of volume V2 to the storage tank. During the water filling process, add sodium hydroxide, ammonia and trisodium phosphate of a predetermined mass.

[0016] Step 6: After the water filling is completed, start the corresponding discharge pump of the storage tank to circulate the water and record the initial time as t1. After time T / 2, start manually sampling and analyzing the concentration of each substance. Perform sampling and analysis once every preset time interval. When the concentration of each substance is stable, record the time when the concentration is first measured as t2, and determine t3 = t2 - t1.

[0017] Step 7: Repeat step 6 to obtain multiple t3s, and determine the average value t4 of the multiple t3s;

[0018] Step 8: If t4 ≤ T, determine t4 or T as the optimal duration for tank circulation.

[0019] In one possible implementation, the method further includes:

[0020] Step 9: Calculate the optimal receiving liquid level of the storage tank based on parameters such as the optimal circulation time, the original design volume and liquid level alarm value of the storage tank, the discharge flow rate of the discharge pump, and the total volume and discharge flow rate of the upstream of the non-discharge liquid discharge system. This ensures that the optimal receiving liquid level of a single storage tank is required for continuous reception and discharge between multiple storage tanks.

[0021] In one possible implementation, the method further includes: determining an operation order based on the optimal receiving liquid level in step 9 to ensure that the non-discharge waste liquid discharge system of the conventional island can continuously receive and discharge the non-discharge waste liquid of the conventional island during overhaul.

[0022] In one possible implementation, the method further includes:

[0023] Step 10: In the later stage of nuclear power plant operation, increase the flow rate Q1 of the non-radical waste liquid transfer pump in the conventional island. Based on Q1, repeat steps 1 to 8 to calculate the circulation time T.

[0024] The beneficial effects of this disclosure are as follows:

[0025] 1. The method disclosed herein proposes a novel process design for the non-radioactive waste liquid discharge system of nuclear power plants. This design is highly versatile and applicable to nuclear power plants at all stages of development. Specifically, nuclear power plants under construction can be optimized using this method, and operating nuclear power plants can achieve the same effect through simple optimization and modification.

[0026] 2. The implementation of the method disclosed herein can help nuclear power plants improve the discharge efficiency of non-radiative waste liquid systems by 40%, currently each storage tank in the power plant has a volume of 500m³. 3 The discharge pump flow rate is approximately 170 m³ / h. 3 Before the design improvement, the total time for each storage tank to circulate and discharge water after it is filled was 8 hours. After the improvement with this method, the total time for circulation and discharge is 4.8 hours.

[0027] 3. The method disclosed herein provides an effective verification method. After the nuclear power plant improves its non-radioactive waste liquid discharge system by referring to the method disclosed herein, the verification method can assist the nuclear power plant in effectively measuring the optimal cycle time, which facilitates more precise optimization of the plant's operation.

[0028] 4. The method disclosed herein proposes a new system operation mode to achieve uninterrupted emissions from the conventional island of a nuclear power plant during major overhauls;

[0029] 5. The method disclosed herein provides a calculation method for process system design. Using this method, designers can optimize detailed designs according to different emission requirements to ensure that the new process design can perfectly match the emission requirements of the power plant.

[0030] Shortening the circulation time of non-radioactive waste liquid discharge systems in the conventional island of nuclear power plants before non-radioactive waste liquid discharge can shorten the overhaul period of the conventional island and create higher operational efficiency for the power plant. Addressing the current issue of long circulation times before non-radioactive waste liquid discharge in various nuclear power plants, a new process design method is proposed, which can improve the non-radioactive waste liquid discharge efficiency by 40%. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a conventional island non-discharge liquid discharge system.

[0032] Figure 2 This is a schematic diagram of the storage tank structure. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Figure 1 This is a schematic diagram of the conventional island non-emission waste liquid discharge process, such as... Figure 1 As shown, the main source of non-discharge waste liquid in the conventional island is the medium 1 that needs to be emptied from the equipment by various users of the conventional island during daily operation or major overhaul due to maintenance needs. The medium 1 is collected by the non-discharge waste liquid collection system 2 of the conventional island and transported to the storage tank 4 of the non-discharge waste liquid discharge system of the conventional island through the non-discharge waste liquid transfer pump 3.

[0035] For a megawatt-class pressurized water reactor nuclear power plant, it is typically designed with three 500m³-12 ... 3 Storage tanks. For example... Figure 2 Each storage tank corresponds to a non-discharge waste liquid discharge pump 5. The non-discharge waste liquid discharge pump 5 circulates the medium within the storage tank through a recirculation pipeline 8 and multiple nozzles 7 installed on the recirculation pipeline 8, ensuring thorough and uniform mixing. Discharge is only permitted after chemical sampling and verification of compliance. In related technologies, the discharge standards for conventional island non-discharge waste liquid discharge systems are designed as follows: a) continuous circulation mixing time of waste liquid greater than 3 hours; b) pH value of waste liquid between 6 and 9; c) total γ specific activity less than 0.4 MBq / m³. 3 .

[0036] The above requirements make the conventional island non-discharge waste liquid discharge system take a long time to process after receiving waste liquid, including circulation and discharge. The discharge time is only affected by the discharge pump flow rate, and there is no other means except to replace the discharge pump.

[0037] Step 1: For nuclear power plants under construction or in operation that have completed their design, determine the parameters of the non-radioactive waste liquid discharge system of the conventional island of the nuclear power plant, including: the total water volume of the conventional island of the nuclear power plant is V1, the flow rate of the non-radioactive waste liquid transfer pump of the conventional island is Q1, the volume of a single storage tank of the non-radioactive waste liquid discharge system of the conventional island is V2, the total number of non-radioactive waste liquid storage tanks of the conventional island is n, the flow rate of the non-radioactive waste liquid discharge pump of the conventional island is Q2, and the circulation time before discharge of the non-radioactive waste liquid from the conventional island storage tank is T.

[0038] Step 2: Based on the parameters of the conventional island non-radioactive waste liquid discharge system of the nuclear power plant, determine the circulation time T. To ensure that the conventional island non-radioactive waste liquid discharge system can continuously receive the wastewater from the conventional island, T must satisfy the condition shown in Equation 1:

[0039]

[0040] Step 3, in the design of the conventional island non-discharge waste liquid discharge system, the discharge pump of the conventional island non-discharge waste liquid discharge system is usually used as the recirculation pump of the conventional island non-discharge waste liquid discharge system storage tank. Therefore, there is a relationship between T and the pump flow rate Q2 as shown in Equation 2:

[0041]

[0042] Wherein, η represents the mixing efficiency of the device, and η is related to the height of the recirculation pipe inserted into the tank and whether there is a nozzle device in the tank.

[0043] Step 3: Based on the required circulation time T shown in Equations 1 and 2, establish a model. Set the initial position of the radioactive salt particles at the bottom of the storage tank. Add a momentum source term to simulate the power supplied by the pump to the conventional island non-radioactive waste liquid discharge system. Use an Euler two-phase flow model to determine the interaction forces between radioactive salt particles and water, and between radioactive salt particles themselves, thereby obtaining the mixing efficiency of the device. Figure 2 As shown, by continuously correcting the structure of nozzle 7 to change the flow rate of the medium at the nozzle 7 outlet, and by continuously correcting the insertion depth of the recirculation line 8, T is made to meet the requirements of Equation 1 and Equation 2.

[0044] Step 4: Based on the condition that T satisfies the requirements of Equation 1 and Equation 2, obtain the nozzle structure and recirculation pipeline insertion depth, and modify the on-site recirculation pipeline.

[0045] Step 5: Test and verify the modified pipeline. Add water of volume V2 to the storage tank. During the water filling process, add sodium hydroxide, ammonia and trisodium phosphate of a predetermined mass.

[0046] Step 6: After the water filling is completed, start the corresponding discharge pump of the storage tank to circulate the water and record the initial time as t1. After time T / 2, start manually sampling and analyzing the concentration of each substance. Perform sampling and analysis every preset time interval (e.g., 5 min). When the concentration of each substance is stable, record the time when the first concentration is measured as t2, and determine t3 = t2 - t1.

[0047] Step 7: Repeat step 6 to obtain multiple t3s, and determine the average value t4 of the multiple t3s;

[0048] Step 8: If t4 ≤ T, determine t4 or T as the optimal duration for tank circulation.

[0049] In one possible implementation, the method disclosed herein further includes:

[0050] Step 9: Calculate the optimal receiving liquid level for the storage tank based on parameters such as the optimal circulation time, the original design volume (bottom area, height) of the storage tank, the liquid level alarm value, the discharge flow rate of the discharge pump, and the total volume and discharge flow rate of the non-discharge waste liquid discharge system upstream. This ensures the optimal receiving liquid level for each individual storage tank required for continuous reception and discharge between multiple storage tanks. Based on the optimal receiving liquid level from Step 9, determine the operation plan to ensure that the non-discharge waste liquid discharge system of the conventional island can continuously receive and discharge non-discharge waste liquid during the overhaul period.

[0051] Step 10: If, in the later stages of operation of the nuclear power plant, it is necessary to further improve the efficiency of the non-radioactive waste liquid discharge system of the conventional island, then the flow rate Q1 of the non-radioactive waste liquid transfer pump of the conventional island should be increased first, and the circulation time T should be recalculated according to the capacity of Q1 and the method of this disclosure.

[0052] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for discharging non-radioactive waste liquid from the conventional island of a nuclear power plant, characterized in that, The method includes: Step 1: Determine the parameters of the non-radioactive waste liquid discharge system of the conventional island of the nuclear power plant, including: the total water volume of the conventional island of the nuclear power plant is V1, the flow rate of the non-radioactive waste liquid transfer pump of the conventional island is Q1, the volume of a single storage tank of the non-radioactive waste liquid discharge system of the conventional island is V2, the total number of non-radioactive waste liquid storage tanks of the conventional island is n, the flow rate of the non-radioactive waste liquid discharge pump of the conventional island is Q2, and the circulation time before the non-radioactive waste liquid storage tank of the conventional island is T. Step 2: Based on the parameters of the conventional island non-radioactive waste liquid discharge system of the nuclear power plant, determine the circulation time T. To ensure that the conventional island non-radioactive waste liquid discharge system can continuously receive the wastewater from the conventional island, T must satisfy the condition shown in Equation 1: Step 3, in the design of the conventional island non-discharge waste liquid discharge system, the discharge pump of the conventional island non-discharge waste liquid discharge system is usually used as the recirculation pump of the conventional island non-discharge waste liquid discharge system storage tank. Therefore, there is a relationship between T and the pump flow rate Q2 as shown in Equation 2: Where η represents the mixing efficiency of the device, and η is related to the height of the recirculation pipe inserted into the tank and whether there is a nozzle device in the tank. Step 3: According to the requirements of the circulation time T shown in Equations 1 and 2, T is made to meet the requirements of Equations 1 and 2 by continuously correcting the structure of the nozzle and changing the flow rate of the medium at the nozzle outlet of the recirculation pipeline and the insertion depth of the recirculation pipeline. Step 4: Based on the condition that T satisfies the requirements of Equation 1 and Equation 2, obtain the nozzle structure and recirculation pipeline insertion depth, and modify the on-site recirculation pipeline.

2. The method according to claim 1, characterized in that, The method further includes: Step 5: Test and verify the modified pipeline. Add water of volume V2 to the storage tank. During the water filling process, add sodium hydroxide, ammonia and trisodium phosphate of a predetermined mass. Step 6: After the water filling is completed, start the corresponding discharge pump of the storage tank to circulate the water and record the initial time as t1. After time T / 2, start manually sampling and analyzing the concentration of each substance. Perform sampling and analysis once every preset time interval. When the concentration of each substance is stable, record the time when the concentration is first measured as t2, and determine t3 = t2 - t1. Step 7: Repeat step 6 to obtain multiple t3s, and determine the average value t4 of the multiple t3s; Step 8: If t4 ≤ T, determine t4 or T as the optimal duration for tank circulation.

3. The method according to claim 2, characterized in that, The method further includes: Step 9: Calculate the optimal receiving liquid level of the storage tank based on parameters such as the optimal circulation time, the original design volume and liquid level alarm value of the storage tank, the discharge flow rate of the discharge pump, and the total volume and discharge flow rate of the upstream of the non-discharge liquid discharge system. This ensures that the optimal receiving liquid level of a single storage tank is required for continuous reception and discharge between multiple storage tanks.

4. The method according to claim 3, characterized in that, The method further includes: determining the operation order based on the optimal receiving liquid level in step 9, to ensure that the non-discharge waste liquid discharge system of the conventional island can continuously receive and discharge the non-discharge waste liquid of the conventional island during the overhaul.

5. The method according to claim 1, characterized in that, The method further includes: Step 10: In the later stage of nuclear power plant operation, increase the flow rate Q1 of the non-radical waste liquid transfer pump in the conventional island. Based on Q1, repeat steps 1 to 8 to calculate the circulation time T.

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