Ag-110m purification system and method for nuclear power plant

Abstract

The present invention belongs to the field of nuclear power plant control technology, specifically relating to a nuclear power plant Ag-110m purification system and method. The system includes a reactor assembly, a primary main pipeline, a reactor special drainage system, a chemical and volumetric control system, a primary coolant temporary storage system, a primary coolant temporary storage system cation filter, a primary coolant temporary storage system resin trap, and a chemical and volumetric control system charging valve. The present invention's implementation window matches the unit status and overhaul critical path, does not affect the isolation and maintenance of other operating systems, effectively utilizes the resin's purification capacity during its lifespan, and does not generate additional radioactive waste. By establishing a closed-loop purification method for the primary circuit, the system avoids primary circuit medium loss and generates no additional radioactive liquid waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear power plant control, and in particular relates to an Ag-110m purification system and method for a nuclear power plant. Background Art

[0002] Nuclear power plants have historically primarily reduced radiation fields by controlling nickel and cobalt sources, as the radiation fields from large-diameter piping and other systems are primarily caused by Co-58 and Co-60. However, data indicates that after controlling Co-58 and Co-60, Ag-110m has become the primary contributor to radiation fields after shutdowns at some nuclear power plants. In some pressurized water reactor (PWR) plants, Ag-110m's contribution to radiation fields during shutdowns has even reached over 80%. It is estimated that Ag-110m contamination contributes 10-15% of the collective dose in nuclear power plants, posing significant challenges and difficulties in controlling the collective dose at these plants. Furthermore, significant Ag-110m impacts on radiation fields have been discovered during overhauls at several nuclear power plants in China. For example, during the first overhaul of Unit 3 at Tianwan Nuclear Power Plant, Ag-110m activity was found to account for over 80% of the total gamma activity in the primary circuit, making it the primary source of radioactivity. The purification efficiency of traditional purification systems for Ag-110m nuclides is less than 20%, resulting in a significant increase in radiation levels in primary circuit equipment and related areas.

[0003] Therefore, it is necessary to provide a nuclear power plant Ag-110m purification system and method to solve the problems existing in the prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a nuclear power plant Ag-110m purification system and method to reduce the primary circuit Ag-110m radiation source item during reactor outage, thereby reducing the radiation level in the maintenance area and reducing the radiation exposure dose to personnel.

[0005] The technical solution for achieving the purpose of the present invention is as follows:

[0006] A Ag-110m purification system for a nuclear power plant comprises a reactor device, a primary circuit main pipeline, a reactor special drainage system, a chemical and volume control system, a primary circuit coolant temporary storage system, a primary circuit coolant temporary storage system cation filter, a primary circuit coolant temporary storage system resin trap, and a chemical and volume control system charging valve. The reactor device, the primary circuit main pipeline, the reactor special drainage system, the chemical and volume control system, the primary circuit coolant temporary storage system, the primary circuit coolant temporary storage system cation filter, the primary circuit coolant temporary storage system resin trap, and the chemical and volume control system charging valve are connected in sequence, and the chemical and volume control system charging valve is further connected to the primary circuit main pipeline.

[0007] The combined operation mode of the system is as follows:

[0008] When the unit is in maintenance cold shutdown status, the medium in the primary main pipeline is discharged into the reactor special drainage system water tank through the reactor special drainage system downflow drainage valve and pipeline, and then the medium is introduced into the chemical and volume control system deaerator, and the primary coolant temporary storage system water pump is used to introduce the medium into the primary coolant temporary storage system cation filter and the primary coolant temporary storage system resin trap for medium purification, and the purified medium is returned to the primary main pipeline through the chemical and volume control system filling valve, thereby realizing Ag-110m medium purification.

[0009] A method for purifying Ag-110m in a nuclear power plant, the method comprising the following steps:

[0010] Step 1: Confirm that the unit is in maintenance cold shutdown, that the primary circuit is connected to the atmosphere, install pulse control on the valves of the reactor special drainage system, check the status of the equipment involved in the system, and conduct operation verification to ensure that the equipment is available;

[0011] Step 2: Evaluate the purification capacity of the cationic filter in the primary coolant storage system;

[0012] Step 3: Start the water delivery pump of the primary coolant temporary storage system, pulse open the valve of the reactor special drainage system, and maintain the stable liquid level of the degasser of the chemical and volume control systems through the regulating valve;

[0013] Step 4: Take a chemical sample in the first circuit and analyze the current Ag-110m radioactivity A t and compare it with the set purification target A0;

[0014] Step 5: Continue to purify the primary circuit medium, monitor the primary circuit liquid level, track the purification effect of Ag-110m and other corrosion activation products in the primary circuit, evaluate the purification efficiency of the resin bed, track the unit status, stop the purification before the reactor cover is lifted out, stop the pump group, restore the system valve status, restore the system equipment to a safe standby state, and complete the purification.

[0015] The method for evaluating the purification capacity of the cationic filter of the primary coolant temporary storage system in step 2 is:

[0016] C 剩 =C0-C 用

[0017] Among them, C 剩 Indicates the current available purification capacity of the cationic filter of the primary coolant temporary storage system. C0 indicates the initial purification capacity of the cationic filter of the primary coolant temporary storage system. C 用 Indicates that the purification capacity of the primary coolant temporary storage system cation filter has been used.

[0018] The initial purification capacity of the cationic filter of the primary coolant temporary storage system is 2100 mol / m 3 .

[0019] In the step 3, the valve of the reactor drainage system is opened by pulse, and the discharge flow is controlled at 4 kg / s.

[0020] The purification target A0 set in step 4 is 2.0E+04Bq / L.

[0021] The radioactivity of Ag-110m in step 4 is A t The method for comparing with the set purification target A0 is:

[0022] If A t >A0, then execute step 3 and increase the downstream flow rate to 5kg / s;

[0023] If A t <A0, then execute step 5.

[0024] The beneficial technical effects of the present invention are:

[0025] 1) The present invention operates through a combined process system, requiring no modification or additional equipment. It achieves effective purification of Ag-110m in the primary circuit for the first time, with significant purification effects. Using this method, other corrosion activation products, such as Co-58 and Co-60, can be simultaneously removed, with a purification effect approaching 100%. The radiation index of the primary circuit's main equipment, auxiliary equipment, and related areas is significantly reduced, effectively addressing the problem of increased sulfate levels caused by cationic resins during purification of the primary circuit medium and significantly reducing the time required for primary circuit water quality adjustment.

[0026] 2) The implementation window of the present invention matches the unit status and overhaul critical path, does not affect the isolation operation and maintenance work of other operating systems, can effectively utilize the purification capacity of the resin during its service life, and does not generate additional radioactive waste. By establishing a single-loop closed-loop purification method, it will not cause primary loop medium loss and will not generate additional radioactive waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of an Ag-110m purification system for a nuclear power plant provided by the present invention; DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of them. Based on the embodiments described in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, the present invention provides a nuclear power plant Ag-110m purification system, which includes a reactor unit, a primary main pipeline, a reactor special drainage system, a chemical and volume control system, a primary coolant temporary storage system, a primary coolant temporary storage system cation filter, a primary coolant temporary storage system resin trap, and a chemical and volume control system charging valve. The reactor unit, primary main pipeline, reactor special drainage system, chemical and volume control system, primary coolant temporary storage system, primary coolant temporary storage system cation filter, primary coolant temporary storage system resin trap, and chemical and volume control system charging valve are connected in sequence, and the chemical and volume control system charging valve is further connected to the primary main pipeline.

[0030] Through the combined operation of the above systems and equipment, an Ag-110m purification system is provided to achieve the purpose of Ag-110m purification control. The specific system combination operation mode is as follows:

[0031] When the unit is in maintenance cold shutdown status, the combined system operation is started, and the medium in the primary main pipeline is discharged into the reactor special drainage system water tank through the reactor special drainage system downflow drainage valve and pipeline, and the medium is introduced into the chemical and volume control system deaerator using the pipeline connected to the system pump group and the chemical and volume control system, and the medium is introduced into the primary coolant temporary storage system cation filter and the primary coolant temporary storage system resin trap using the primary coolant temporary storage system water pump and the deaerator connecting pipeline for medium purification, and the purified medium is returned to the primary main pipeline through the chemical and volume control system charging valve, thereby realizing Ag-110m medium purification.

[0032] The present invention also provides a method for purifying Ag-110m in a nuclear power plant, the method comprising the following steps:

[0033] Step 1: Confirm that the unit is in maintenance cold shutdown, that the primary circuit is connected to the atmosphere, install pulse control on the valves of the reactor special drainage system, check the status of the equipment involved in the system, and conduct operation verification to ensure that the equipment is available;

[0034] Step 2: Evaluate the purification capacity of the cationic filter of the primary coolant temporary storage system. The capacity evaluation method is as follows: C 剩 =C0-C用 , C 剩 Indicates the current available purification capacity of the cationic filter of the primary coolant temporary storage system. C0 indicates the initial purification capacity of the cationic filter of the primary coolant temporary storage system. C 用 Indicates that the purification capacity of the cationic filter of the primary coolant temporary storage system has been used;

[0035] The initial purification capacity of the cationic filter of the primary coolant temporary storage system is 2100 mol / m 3 .

[0036] Step 3: Start the water pump of the primary coolant storage system, pulse open the valve of the reactor special drainage system, control the discharge flow at 4 kg / s, and maintain the stable liquid level of the chemical and volume control system degasser through the regulating valve;

[0037] Step 4: Take a chemical sample in the first circuit and analyze the current Ag-110m radioactivity A t and compare it with the set purification target A0. The comparison method is as follows:

[0038] If A t >A 0， Then execute step 3 and increase the downstream flow rate to 5kg / s;

[0039] If A t <A 0， Then execute step 5;

[0040] The set purification target A0 is 2.0E+04Bq / L.

[0041] Step 5: Continue to purify the primary circuit medium, monitor the primary circuit liquid level, track the purification effect of Ag-110m and other corrosion activation products in the primary circuit, evaluate the purification efficiency of the resin bed, track the unit status, stop the purification before the reactor cover is lifted out, stop the pump group, restore the system valve status, restore the system equipment to a safe standby state, and complete the purification.

[0042] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. However, the present invention is not limited to the above embodiments. Various modifications can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Any content not described in detail in the present invention may be adapted from existing technologies.

Claims

1. A nuclear power plant Ag-110m purification system, characterized by: The system includes a reactor device, a primary circuit main pipeline, a reactor special drainage system, a chemical and volume control system, a primary circuit coolant temporary storage system, a primary circuit coolant temporary storage system cation filter, a primary circuit coolant temporary storage system resin trap, and a chemical and volume control system charging valve; wherein the reactor device, the primary circuit main pipeline, the reactor special drainage system, the chemical and volume control system, the primary circuit coolant temporary storage system, the primary circuit coolant temporary storage system cation filter, the primary circuit coolant temporary storage system resin trap, and the chemical and volume control system charging valve are connected in sequence, and the chemical and volume control system charging valve is further connected to the primary circuit main pipeline; The system's combined operation is as follows: When the unit is in maintenance cold shutdown status, the medium in the primary main pipeline is discharged into the reactor special drainage system water tank through the reactor special drainage system downflow drainage valve and pipeline, and then the medium is introduced into the chemical and volume control system deaerator, and the primary coolant temporary storage system water pump is used to introduce the medium into the primary coolant temporary storage system cation filter and the primary coolant temporary storage system resin trap for medium purification, and the purified medium is returned to the primary main pipeline through the chemical and volume control system filling valve, thereby realizing Ag-110m medium purification.

2. The purification method of the Ag-110m purification system of a nuclear power plant according to claim 1, characterized in that: The method includes the following steps: Step 1: Confirm that the unit is in maintenance cold shutdown, that the primary circuit is connected to the atmosphere, install pulse control on the valves of the reactor special drainage system, check the status of the equipment involved in the system, and conduct operation verification to ensure that the equipment is available; Step 2: Evaluate the purification capacity of the cationic filter in the primary coolant storage system; Step 3: Start the water delivery pump of the primary coolant temporary storage system, pulse open the valve of the reactor special drainage system, and maintain the stable liquid level of the degasser of the chemical and volume control systems through the regulating valve; Step 4: Take a chemical sample in the first circuit and analyze the current Ag-110m radioactivity A t and compare it with the set purification target A0; Step 5: Continue to purify the primary circuit medium, monitor the primary circuit liquid level, track the purification effect of Ag-110m and other corrosion activation products in the primary circuit, evaluate the purification efficiency of the resin bed, track the unit status, stop the purification before the reactor cover is lifted out, stop the pump group, restore the system valve status, restore the system equipment to a safe standby state, and complete the purification.

3. The Ag-110m purification method for a nuclear power plant according to claim 2, characterized in that: The method for evaluating the purification capacity of the cationic filter and the resin trap of the primary coolant temporary storage system in step 2 is: C 剩 =C0-C 用 Among them, C 剩 Indicates the current available purification capacity of the cationic filter of the primary coolant temporary storage system. C0 indicates the initial purification capacity of the cationic filter of the primary coolant temporary storage system. C 用 Indicates that the purification capacity of the primary coolant temporary storage system cation filter has been used.

4. The Ag-110m purification method for a nuclear power plant according to claim 3, characterized in that: The initial purification capacity of the cationic filter of the primary coolant temporary storage system is 2100 mol / m 3 .

5. The Ag-110m purification method for a nuclear power plant according to claim 4, characterized in that: In the step 3, the valve of the reactor drainage system is opened by pulse, and the discharge flow is controlled at 4 kg / s.

6. The Ag-110m purification method for a nuclear power plant according to claim 5, characterized in that: The purification target A0 set in step 4 is 2.0E+04Bq / L.

7. The Ag-110m purification method for a nuclear power plant according to claim 6, characterized in that: The radioactivity of Ag-110m in step 4 is A t The method for comparing with the set purification target A0 is: If A t >A0, then execute step 3 and increase the downstream flow rate to 5kg / s; If A t <A0, then execute step 5.

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