Method and system for treating complex liquid radioactive waste for nuclear power plants

Abstract

This invention belongs to the field of radioactive waste treatment, specifically relating to a method and system for treating complex radioactive waste from nuclear power plants. The method includes: Step 1, injecting alkaline chemical reagents and flocculants into the radioactive waste by controlling a PLC module to remove organic matter and radioactive colloids; Step 2, removing ionic nuclides from the radioactive waste by passing it through a resin bed and filter. This invention effectively removes organic matter, colloidal nuclides, and ionic nuclides from radioactive waste from nuclear power plants by purifying radioactive waste containing organic matter and colloidal nuclides, and then further purifying radioactive waste containing ionic nuclides.

Description

Technical Field

[0001] This invention belongs to the field of radioactive waste liquid treatment, specifically relating to a method and system for treating complex radioactive waste liquid used in nuclear power plants. Background Technology

[0002] Fuqing Nuclear Power Plant Units 5 and 6 are demonstration units of the "Hualong One" reactor. Considering the overall design of the units, the decontaminant (organic matter) generated during overhauls is discharged into the process wastewater tank of the ZLT (Zero Liquid Treatment System). However, organic matter can cause ion exchange resins to become ineffective, making it impossible to treat radioactive waste using traditional ion exchange resin methods. The combination of colloidal nuclides (Co-58, Ag-110m, etc.) and ionic nuclides inherent in pressurized water reactor nuclear power plants results in a complex composition of radioactive waste.

[0003] Therefore, considering the actual situation of the Hualong power plant, it is essential to develop a method for treating complex radioactive waste liquids. Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for treating complex radioactive waste liquids used in nuclear power plants. This method and system purify radioactive waste liquids containing organic matter and colloidal nuclides, and then purify radioactive waste liquids containing ionic nuclides, effectively removing organic matter, colloidal nuclides, and ionic nuclides from radioactive waste liquids in nuclear power plants.

[0005] Technical solution to achieve the purpose of this invention:

[0006] A method for treating complex radioactive waste liquid from a nuclear power plant, the method comprising:

[0007] Step 1: Control the chemical metering pumps of alkaline chemical reagents and flocculants through the PLC module to inject alkaline chemical reagents and flocculants into the radioactive waste liquid to remove organic matter and radioactive colloids from the radioactive waste liquid.

[0008] Step 2: Remove ionic nuclides from radioactive waste liquid through a resin bed and filter.

[0009] Further, step 1 includes:

[0010] Step 1.1: Add alkaline chemical reagent to the radioactive waste liquid. The PLC module controls the chemical metering pump of the alkaline chemical reagent according to the pH value of the radioactive waste liquid after the alkaline chemical reagent is injected, and adjusts the injection amount of the alkaline chemical reagent.

[0011] Step 1.2: Remove debris or fragments from the radioactive waste liquid by passing it through a glass fiber pre-filter;

[0012] Step 1.3: Inject flocculant into radioactive waste liquid. The PLC module controls the chemical metering pump of flocculant according to the conductivity of radioactive waste liquid after flocculant injection, and adjusts the injection rate of flocculant.

[0013] Step 1.4: The radioactive waste liquid treated in steps 1.1-1.3 is then treated by an activated carbon filter to remove stable radioactive colloids and adsorb and remove organic matter.

[0014] Further, step 1.1 specifically involves: adding an alkaline chemical reagent to the radioactive waste liquid; the PLC module controlling the injection amount of the alkaline chemical reagent by detecting the pH value of the radioactive waste liquid after injection; a pH meter detecting the pH value of the radioactive waste liquid after injection; the pH meter sending the detected pH value to the PLC module; the PLC module receiving the pH value sent by the pH meter; and controlling the chemical metering pump of the alkaline chemical reagent according to the preset pH control range to adjust the injection amount of the alkaline chemical reagent to make the pH value 7-8.

[0015] Further, step 1.3 specifically involves: injecting flocculant into the radioactive waste liquid; the PLC module controlling the injection rate of flocculant by detecting the conductivity of the radioactive waste liquid after flocculant injection; a conductivity meter detecting the conductivity of the radioactive waste liquid after flocculant injection; the conductivity meter sending the detected conductivity to the PLC module; the PLC module receiving the conductivity sent by the conductivity meter; and controlling the chemical metering pump of the flocculant according to the preset conductivity control range to adjust the injection rate of the flocculant so that the conductivity is 50-500 μS / cm.

[0016] Furthermore, the alkaline chemical reagent is 25% sodium hydroxide.

[0017] Furthermore, in step 1.4, the expected value of the flowing current of the radioactive waste liquid after treatment by the activated carbon filter is 10-200 SCU, and the expected value of the maximum particle count is 100 / mL.

[0018] Further, step 2 includes:

[0019] Step 2.1: Remove radioactive ions from radioactive waste liquid by connecting a series of strong acid cation exchange resin beds and a mixed resin bed of strong acid and strong base.

[0020] Step 2.2: Remove particulates and resin particles from the radioactive waste liquid by passing it through a glass fiber filter cartridge post-filter.

[0021] Furthermore, in step 2.1, the series connection of the strong acid cation exchange resin bed and the mixed resin bed of strong acid and strong base consists of three strong acid cation exchange resin beds and one mixed resin bed of strong acid and strong base connected in series.

[0022] Furthermore, the glass fiber filter element in steps 1.2 and 2.2 is a 25µm glass fiber filter element.

[0023] A complex radioactive waste treatment system for nuclear power plants includes: a process wastewater tank, a transfer pump for the process wastewater tank, an alkaline chemical reagent tank, a metering pump for the alkaline chemical reagent, a flocculant tank, a metering pump for the flocculant, a mixer, an activated carbon filter, a resin bed, a post-filter, a wastewater discharge pipeline, a pH meter, a conductivity meter, a flow ammeter, and a particle counter. The process wastewater tank, the alkaline chemical reagent tank, and the flocculant tank are respectively connected to the mixer via the transfer pump for the process wastewater tank, the metering pump for the alkaline chemical reagent, and the metering pump for the flocculant. The mixer is connected to the activated carbon filter, the activated carbon filter is connected to the post-filter via the resin bed, and the post-filter is connected to the wastewater discharge pipeline. A pH meter and a conductivity meter are installed at the outlet of the mixer, and a flow ammeter and a particle counter are installed at the outlet of the activated carbon filter. The pH meter, conductivity meter, flow ammeter, and particle counter are connected to a particle control and management system.

[0024] Furthermore, the system also includes a premixer and a prefilter. The process wastewater tank and the alkaline chemical reagent tank are connected to the premixer via the transfer pump of the process wastewater tank and the chemical metering pump of the alkaline chemical reagent, respectively. The premixer is connected to the prefilter, and the prefilter is connected to the mixer.

[0025] Furthermore, the resin bed includes three cation resin beds connected in series and one mixed resin bed, and the activated carbon filter is connected to the post-filter via the three cation resin beds connected in series and one mixed resin bed.

[0026] The beneficial technical effects of this invention are as follows:

[0027] 1. Pressurized water reactor nuclear power plant radioactive waste liquid contains a certain amount of colloidal nuclides (Co-58, Ag-110m, etc.) and ionic nuclides, and the removal of colloidal nuclides is difficult. This invention provides a method for treating complex radioactive waste liquid from nuclear power plants. Through flocculation, sedimentation, and filtration steps, colloidal nuclides can be effectively removed; through three cation exchange resin beds and one mixed resin bed connected in series, ionic nuclides can be effectively removed in a single step, thereby reducing the activity level of the radioactive waste liquid from nuclear power plants.

[0028] 2. Organic components in organic detergents can cause ion exchange resins to fail. The present invention provides a method for treating complex radioactive waste liquid in nuclear power plants. By setting up an activated carbon filter, organic matter can be effectively adsorbed, thus avoiding the failure of the ion exchange resin bed caused by complex radioactive waste liquid containing organic matter.

[0029] 3. Fuqing Nuclear Power Plant Units 5 and 6 have accumulated 3 reactor years of operation. The total emission of complex radioactive waste liquid after treatment by the complex radioactive waste liquid treatment method for nuclear power plants provided by this invention is <0.9Mbq / t, which meets the national environmental emission standards. Attached Figure Description

[0030] Figure 1 A process flow diagram of a complex radioactive waste liquid treatment system for nuclear power plants provided by the present invention;

[0031] In the diagram: 1-Process wastewater tank; 2-Transfer pump for process wastewater tank; 3-Alkaline chemical reagent tank; 4-Metering pump for alkaline chemical reagent; 5-Premixer; 6-Pre-filter; 7-Flocculant tank; 8-Metering pump for flocculant; 9-Mixer; 10-Activated carbon filter; 11-Cation resin bed; 12-Mixed resin bed; 13-Post-filter; 14-Waste liquid discharge pipeline; 15-pH meter; 16-Conductivity meter; 17-Flow ammeter; 18-Particle counter. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0033] The present invention provides a method for treating complex radioactive waste liquid from nuclear power plants, which specifically includes the following steps:

[0034] Step 1: Inject alkaline chemical reagents and flocculants into the radioactive waste liquid to remove organic matter and radioactive colloids.

[0035] The Particle Control Management (PMC) system controls the metering pumps for alkaline chemical reagents and flocculants to inject them into the radioactive waste liquid. The metering pumps for the alkaline chemical reagents and flocculants are controlled by the PMC's PLC module.

[0036] Step 1.1: Add alkaline chemical reagent to the radioactive waste liquid. The PLC module controls the metering pump of the alkaline chemical reagent based on the pH value of the radioactive waste liquid after the injection, adjusting the injection volume of the alkaline chemical reagent.

[0037] The alkaline chemical reagent injected into the radioactive waste liquid is 25% sodium hydroxide. The PLC module controls the injection volume of the alkaline chemical reagent by detecting the pH value of the radioactive waste liquid after injection. A pH meter detects the pH value of the radioactive waste liquid after injection and sends the detected pH value to the PLC module. The PLC module receives the pH value from the pH meter and, according to a preset pH control range, controls the chemical metering pump of the alkaline chemical reagent to adjust the injection volume and keep the pH value within the control range. The pH control range is 7-8.

[0038] Step 1.2: Remove debris or fragments from the radioactive waste liquid by passing it through a glass fiber pre-filter.

[0039] The radioactive waste liquid, whose pH has been adjusted in step 1.1, is filtered through a pre-filter with a 25µm glass fiber filter element to remove debris or fragments with a particle size greater than 25µm from the radioactive waste liquid, thus avoiding clogging of the activated carbon filter.

[0040] Step 1.3: Inject flocculant into the radioactive waste liquid. The PLC module controls the flocculant metering pump based on the conductivity of the radioactive waste liquid after flocculant injection, adjusting the flocculant injection rate.

[0041] Flocculants are injected into radioactive waste to promote the flocculation of colloidal substances. The PLC module controls the injection rate of the flocculant by detecting its conductivity after injection. A conductivity meter detects the conductivity of the radioactive waste after flocculant injection and sends the detected conductivity to the PLC module. The PLC module receives the conductivity data and, based on a preset conductivity control range, controls the flocculant metering pump to adjust the flocculant injection rate, ensuring the conductivity remains within the control range. The conductivity control range is 50-500 μS / cm.

[0042] For radioactive waste containing organic matter, colloidal and ionic nuclides, this step adjusts Co-58, Ag-110m, etc., to form a stable colloidal state.

[0043] Step 1.4: The radioactive waste liquid treated in steps 1.1-1.3 is then processed through an activated carbon filter to remove stable radioactive colloids and adsorb and remove organic matter.

[0044] The radioactive waste liquid treated in steps 1.1-1.3 is then processed through an activated carbon filter. The expected value of the flow current of the treated radioactive waste liquid is 10-200 SCU, and the expected value of the maximum particle count is 100 / mL. This process removes steady-state radioactive colloids and organic matter from the radioactive waste liquid, resulting in a radioactive waste liquid with organic matter and radioactive colloids removed.

[0045] Step 2: Remove ionic nuclides from radioactive waste liquid through a resin bed and filter.

[0046] Step 2.1: Remove radioactive ions from radioactive waste liquid by using a series of strongly acidic cation exchange resin beds and a mixed resin bed of strongly acid and strongly alkaline substances.

[0047] The radioactive waste liquid obtained in step 1.4 is passed through three strongly acidic cation exchange resin beds and one strongly acidic and strongly alkaline mixed resin bed connected in series to remove radioactive ions from the waste liquid.

[0048] Step 2.2: Remove particulates and resin particles from the radioactive waste liquid by passing it through a post-filter with a glass fiber filter element.

[0049] The radioactive waste liquid obtained in step 2.1 is passed through a 25µm glass fiber filter to remove particulates and resin particles, resulting in radioactive waste liquid free of organic matter, radioactive colloids, and ionic nuclides.

[0050] like Figure 1 As shown, the present invention also provides a complex radioactive waste liquid treatment system for nuclear power plants. The system includes: a process wastewater tank 1, a transfer pump for the process wastewater tank 2, an alkaline chemical reagent tank 3, a chemical metering pump for the alkaline chemical reagent 4, a premixer 5, a pre-filter 6, a flocculant tank 7, a chemical metering pump for the flocculant 8, a mixer 9, an activated carbon filter 10, a cation exchange resin bed 11, a mixed resin bed 12, a post-filter 13, a waste liquid discharge pipeline 14, a pH meter 15, a conductivity meter 16, a flow ammeter 17, and a particle counter 18.

[0051] The process wastewater tank 1 and the alkaline chemical reagent tank 3 are connected to the premixer 5 via the process wastewater tank transfer pump 2 and the alkaline chemical reagent metering pump 4, respectively. The premixer 5 is connected to the prefilter 6, and the prefilter 6 is connected to the mixer 9. The flocculant tank 7 is connected to the mixer 9 via the flocculant metering pump 8. The mixer 9 is connected to the activated carbon filter 10. The activated carbon filter 10 is connected to the post-filter 13 via three cation exchange resin beds 11 and one mixed resin bed 12 connected in series. The post-filter 13 is connected to the waste liquid discharge pipeline 14. A pH meter 15 and a conductivity meter 16 are installed at the outlet of the mixer 9. A flow ammeter 17 and a particle counter 18 are installed at the outlet of the activated carbon filter 10. The pH meter 15, conductivity meter 16, flow ammeter 17, and particle counter 18 are connected to the particle control management system.

[0052] 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, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. All contents not described in detail in the present invention can be derived from existing technologies.

Claims

1. A method for treating complex radioactive waste liquid from nuclear power plants, characterized in that, The method includes: Step 1: Control the chemical metering pumps of alkaline chemical reagents and flocculants through the PLC module to inject alkaline chemical reagents and flocculants into the radioactive waste liquid to remove organic matter and radioactive colloids from the radioactive waste liquid. Step 2: Remove ionic nuclides from radioactive waste liquid through a resin bed and filter; Step 1 includes: Step 1.1: Add alkaline chemical reagent to the radioactive waste liquid. The PLC module controls the chemical metering pump of the alkaline chemical reagent according to the pH value of the radioactive waste liquid after the alkaline chemical reagent is injected, and adjusts the injection amount of the alkaline chemical reagent. Step 1.2: Remove debris or fragments from the radioactive waste liquid by passing it through a glass fiber pre-filter; Step 1.3: Inject flocculant into radioactive waste liquid. The PLC module controls the chemical metering pump of flocculant according to the conductivity of radioactive waste liquid after flocculant injection, and adjusts the injection rate of flocculant. Step 1.4: The radioactive waste liquid treated in steps 1.1-1.3 is then treated by an activated carbon filter to remove stable radioactive colloids and adsorb and remove organic matter. Step 2 includes: Step 2.1: Remove radioactive ions from radioactive waste liquid by connecting a series of strong acid cation exchange resin beds and a mixed resin bed of strong acid and strong base. Step 2.2: Remove particulates and resin particles from the radioactive waste liquid by passing it through a post-filter with a glass fiber filter element; The method employs a complex radioactive waste liquid treatment system for nuclear power plants, the system comprising: a process wastewater tank (1), a transfer pump (2) for the process wastewater tank, an alkaline chemical reagent tank (3), a chemimetering pump (4) for the alkaline chemical reagent, a flocculant tank (7), a chemimetering pump (8) for the flocculant, a mixer (9), an activated carbon filter (10), a resin bed, a post-filter (13), a waste liquid discharge pipeline (14), a pH meter (15), a conductivity meter (16), a flow ammeter (17), and a particle counter (18); the process wastewater tank (1), the alkaline chemical reagent tank (3), and the flocculant tank (7) are respectively connected by the transfer pump (2) for the process wastewater tank. A chemical metering pump (4) for alkaline chemical reagents and a chemical metering pump (8) for flocculants are connected to a mixer (9). The mixer (9) is connected to an activated carbon filter (10). The activated carbon filter (10) is connected to a post-filter (13) via a resin bed. The post-filter (13) is connected to a waste liquid discharge pipeline (14). A pH meter (15) and a conductivity meter (16) are installed at the outlet of the mixer (9). A flow ammeter (17) and a particle counter (18) are installed at the outlet of the activated carbon filter (10). The pH meter (15), conductivity meter (16), flow ammeter (17), and particle counter (18) are connected to a particle control management system.

2. The method for treating complex radioactive waste liquid from nuclear power plants according to claim 1, characterized in that, Step 1.1 specifically involves: adding an alkaline chemical reagent to the radioactive waste liquid; the PLC module controlling the injection amount of the alkaline chemical reagent by detecting the pH value of the radioactive waste liquid after injection; a pH meter detecting the pH value of the radioactive waste liquid after injection; the pH meter sending the detected pH value to the PLC module; the PLC module receiving the pH value sent by the pH meter; and controlling the chemical metering pump of the alkaline chemical reagent according to the preset pH control range to adjust the injection amount of the alkaline chemical reagent to make the pH value 7-8.

3. The method for treating complex radioactive waste liquid from nuclear power plants according to claim 1, characterized in that, Step 1.3 specifically involves: injecting flocculant into the radioactive waste liquid; the PLC module controlling the injection rate of flocculant by detecting the conductivity of the radioactive waste liquid after flocculant injection; a conductivity meter detecting the conductivity of the radioactive waste liquid after flocculant injection; the conductivity meter sending the detected conductivity to the PLC module; the PLC module receiving the conductivity from the conductivity meter and controlling the chemical metering pump of the flocculant according to the preset conductivity control range, adjusting the injection rate of the flocculant to make the conductivity 50-500 μS / cm.

4. The method for treating complex radioactive waste liquid from nuclear power plants according to claim 1, characterized in that, The alkaline chemical reagent is 25% sodium hydroxide.

5. The method for treating complex radioactive waste liquid from nuclear power plants according to claim 1, characterized in that, In step 1.4, the expected value of the flowing current of the radioactive waste liquid after treatment by the activated carbon filter is 10-200 SCU, and the expected value of the maximum particle count is 100 / mL.

6. The method for treating complex radioactive waste liquid from nuclear power plants according to claim 1, characterized in that, The series connection of the strong acid cation exchange resin bed and the strong acid and strong base mixed resin bed in step 2.1 consists of three strong acid cation exchange resin beds and one strong acid and strong base mixed resin bed connected in series.

7. The method for treating complex radioactive waste liquid from nuclear power plants according to claim 1, characterized in that, The glass fiber filter element in steps 1.2 and 2.2 is a 25µm glass fiber filter element.

8. The method for treating complex radioactive waste liquid from nuclear power plants according to claim 1, characterized in that, The system also includes a premixer (5) and a prefilter (6). The process wastewater tank (1) and the alkaline chemical reagent tank (3) are connected to the premixer (5) via the transfer pump (2) of the process wastewater tank and the chemical metering pump (4) of the alkaline chemical reagent, respectively. The premixer (5) is connected to the prefilter (6), and the prefilter (6) is connected to the mixer (9).

9. A method for treating complex radioactive waste liquid from a nuclear power plant according to claim 1, characterized in that, The resin bed includes three cation resin beds (11) connected in series and one mixed resin bed (12). The activated carbon filter (10) is connected to the post-filter (13) via the three cation resin beds (11) connected in series and one mixed resin bed (12).

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