A fluorescein sodium detection method for high efficiency filter efficiency detection

Abstract

The application discloses a fluorescein sodium detection method for high-efficiency filter efficiency detection, and relates to the technical field of radioactive waste gas treatment. The method comprises the following steps: S1, injecting fluorescein sodium on the upstream of a ventilation system, and setting a sampling clamp provided with a filter membrane at the upstream and downstream sampling ports of a high-efficiency filter to carry out sampling; S2, after sampling, soaking the filter membrane in the sampling clamp in a weak alkaline solution to form a fiber suspension liquid; S3, after soaking, adjusting the PH value of the fiber suspension liquid to be alkaline by using an alkaline reagent; S4, adding an appropriate amount of a coprecipitation reagent to the fiber suspension liquid, uniformly stirring the solution, and then standing, so that the fiber suspension liquid is precipitated or aggregated; and S5, after standing the solution, taking an appropriate amount of the clear and transparent soaking liquid in the middle layer, and measuring the content of the fluorescein sodium in the soaking liquid by using a fluorescence spectrophotometer. The method provided by the application can make the fiber suspension liquid be precipitated or aggregated, so that the fluorescein sodium concentration in the filtrate can be accurately measured.

Description

Technical Field

[0001] This invention relates to the field of radioactive waste gas treatment technology, and specifically to a method for detecting sodium fluorescein for detecting the efficiency of high-efficiency filters. Background Technology

[0002] Nuclear power plants generate large amounts of gases containing radioactive nuclides during operation. These radioactive gases require pre-treatment through ventilation, including high-efficiency filters, iodine filters, and retention beds, to ensure they meet emission standards before being released into the atmosphere. After long-term operation, the ventilation filters and equipment in nuclear power plants need regular efficiency testing to ensure that emissions meet safety standards. Efficiency testing of nuclear power plant ventilation equipment is crucial for the safe and stable operation of the plant. Determining the equipment's service life based on the efficiency results not only saves costs but also scientifically and effectively reduces the generation of radioactive waste.

[0003] High-efficiency particulate air (HEPA) filters are widely used in nuclear power plant ventilation, and the fluorescein sodium method is the most common and effective method for testing HEPA filter efficiency. By injecting fluorescein sodium upstream of the ventilation system, and sampling the HEPA filter upstream and downstream using filter membranes, the actual operating efficiency of the HEPA filter can be easily calculated using a fluorescence spectrophotometer after soaking, as the fluorescein sodium content in the filtrate is determined. However, in traditional experimental testing methods, the sampled filter membranes are easily damaged during soaking after prolonged exposure to hot, dry air, forming a fiber suspension that is difficult to settle, interfering with subsequent measurement results. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for detecting sodium fluorescein in high-efficiency filters. This method enables fiber suspensions to settle or aggregate, thereby accurately measuring the concentration of sodium fluorescein in the filtrate.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for detecting sodium fluorescein for high-efficiency filter efficiency includes the following steps:

[0007] S1. Inject sodium fluorescein upstream of the ventilation system, and place the sampling clip with the filter membrane installed at the upstream and downstream sampling ports of the high-efficiency filter for sampling;

[0008] S2. After sampling, immerse the filter membrane in the sampling clip in a weakly alkaline solution to form a fiber suspension.

[0009] S3. After soaking, use an alkaline reagent to adjust the pH of the fiber suspension to be alkaline.

[0010] S4. Add an appropriate amount of co-precipitant to the fiber suspension, stir the solution evenly and let it stand. The fiber suspension will settle or aggregate.

[0011] S5. After the solution has been allowed to stand, take an appropriate amount of the clear and transparent intermediate layer of the soaking solution and use a fluorescence spectrophotometer to measure the content of sodium fluorescein in the soaking solution.

[0012] Furthermore, in the sodium fluorescein detection method for HEPA filter efficiency testing as described above, sodium fluorescein is injected using a sodium fluorescein generator in step S1, and an appropriate generation rate is set according to the system air volume.

[0013] Furthermore, in the sodium fluorescein detection method for detecting the efficiency of high-efficiency filters as described above, the sampling flow rate in step S1 is 32-40 L / h.

[0014] Furthermore, in the sodium fluorescein detection method for detecting the efficiency of high-efficiency filters as described above, the weakly alkaline solution used in step S2 is ammonia water with a concentration of 0.5-1%, and the soaking time is 15-20 minutes.

[0015] Furthermore, in the sodium fluorescein detection method for detecting the efficiency of high-efficiency filters as described above, the volume of ammonia water used in step S2 is 20 ml.

[0016] Furthermore, in the sodium fluorescein detection method for detecting the efficiency of high-efficiency filters as described above, in step S3, a potassium hydroxide solution with a concentration of 1 mol / L is used to adjust the pH of the fiber suspension to 9-12.

[0017] Furthermore, in the sodium fluorescein detection method for detecting the efficiency of high-efficiency filters as described above, the co-precipitant added in step S4 is selected from one or more of the following: ammonium aluminum sulfate NH4Al(SO4)2, alum AL2(SO4)3.K2SO4.24H2O, or aluminum sulfate AL2(SO4)3.18H2O.

[0018] Furthermore, in the sodium fluorescein detection method for detecting the efficiency of high-efficiency filters as described above, the amount of co-precipitant added in step S4 is 0.001 ml to 0.005 ml.

[0019] Furthermore, in the sodium fluorescein detection method for high efficiency filter testing as described above, in step S5, 3-5 ml of the clear and transparent soaking solution in the middle is taken out using a dropper, the soaking solution is placed in a cuvette, and the content of sodium fluorescein is measured using a fluorescence spectrophotometer.

[0020] Compared with existing technologies, the sodium fluorescein detection method for high-efficiency filter efficiency provided by this invention has the following advantages:

[0021] In this invention, after the sampling filter membrane is soaked in the filtrate, the soaking solution presents as a fiber suspension. After adjusting the solution to a suitable pH and adding an appropriate amount of ammonium aluminum sulfate precipitant, the fiber suspension in the original soaking solution co-precipitates with the aluminum hydroxide colloid formed in the solution. After allowing the solution to stand, the clear, transparent middle layer of the filtrate is taken, and the content of sodium fluorescein is measured using a fluorescence spectrophotometer. This method, by adding a co-precipitation reagent that does not affect the fluorescein measurement results, enables the fiber suspension to settle or aggregate, thereby accurately measuring the concentration of sodium fluorescein in the filtrate. Attached Figure Description

[0022] Figure 1 This is a flowchart of a sodium fluorescein detection method for detecting the efficiency of a high-efficiency filter provided in an embodiment of the present invention;

[0023] Figure 2 It is the fiber suspension that appears in the soaking filtrate after step two in Example 1;

[0024] Figure 3 It refers to the fiber suspension in the original soaking solution after steps three and four in Example 1. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 The following is a flowchart illustrating a method for detecting sodium fluorescein in high-efficiency filters according to an embodiment of the present invention. The method includes the following steps:

[0027] S1. Inject sodium fluorescein upstream of the ventilation system, and place the sampling clip with the filter membrane installed at the upstream and downstream sampling ports of the high-efficiency filter for sampling;

[0028] S2. After sampling, immerse the filter membrane in the sampling clip in a weakly alkaline solution to form a fiber suspension. The weakly alkaline solution is ammonia or other solutions.

[0029] S3. After soaking, use an alkaline reagent to adjust the pH of the fiber suspension to be alkaline.

[0030] The alkaline reagent is potassium hydroxide or other alkaline reagent.

[0031] S4. Add an appropriate amount of co-precipitant to the fiber suspension, stir the solution evenly and let it stand. The fiber suspension will settle or aggregate.

[0032] The coprecipitant can be selected from one or more of the following: ammonium aluminum sulfate (NH4Al(SO4)2), alum (AL2(SO4)3·K2SO4·24H2O), or aluminum sulfate (AL2(SO4)3·18H2O). The amount of coprecipitant used is 0.001 ml to 0.005 ml. After the coprecipitant is added, a colloid is first formed in the solution, and the fiber suspension in the original soaking solution coprecipitates with the colloid formed in the solution.

[0033] S5. After the solution has been allowed to stand, take an appropriate amount of the clear and transparent intermediate layer of the soaking solution and use a fluorescence spectrophotometer to measure the content of sodium fluorescein in the soaking solution.

[0034] Example 1

[0035] Step 1: Connect a sodium fluorescein generator upstream of the ventilation system. Set an appropriate generation rate according to the system air volume. Place the sampling clip with the filter membrane installed at the upstream and downstream sampling ports of the high-efficiency filter for sampling. Set the sampling flow rate to 32-40 L / h and the sampling time to 30 min.

[0036] Step 2: Remove the filter membrane from the sampling clip and soak it in 20ml of 0.5-1% ammonia water for 15-20 minutes;

[0037] Step 3: Use a 1 mol / L potassium hydroxide solution to adjust the pH of the soaking solution to a range of 9-12;

[0038] Step 4: Add 0.2-1.1g of ammonium aluminum sulfate, stir with a glass rod to mix evenly, and let stand on the lab bench for about 5 minutes;

[0039] Step 5: Use a dropper to take out 3-5 ml of the clear and transparent soaking solution from the middle part, place the filtrate in a cuvette, and use a fluorescence spectrophotometer to measure the content of sodium fluorescein.

[0040] Figure 2 After step two, the filtrate becomes a fibrous suspension that fails to settle effectively even after a period of time. The low density of the wood fibers causes them to form a colloid and remain suspended in the solution. If the concentration of sodium fluorescein is measured directly using a fluorescence spectrophotometer without further treatment, the damaged filter membrane will absorb radiation in a band similar to that of sodium fluorescein. This will cause the measurement results to change with the turbidity of the soaking solution, resulting in inaccurate measurements.

[0041] Figure 3After steps three and four, the fiber suspension in the original soaking solution, upon the addition of ammonium aluminum sulfate precipitant, co-precipitates with the aluminum hydroxide colloid formed in the solution. Due to some bubbles generated during stirring, the precipitate aggregates separate into upper and lower layers, clearly separated from the aqueous solution. Experimental tests show that the precipitate aggregates formed in this process do not enrich sodium fluorescein in the aqueous solution and have a negligible impact on the concentration measurement of sodium fluorescein.

[0042] This invention provides a method for detecting sodium fluorescein in high-efficiency filters. After soaking the sampled filter membrane in a filtrate, the filtrate becomes a fiber suspension. The solution is adjusted to a suitable pH, and an appropriate amount of ammonium aluminum sulfate precipitant is added. This causes the fiber suspension in the original soaking solution to co-precipitate with the aluminum hydroxide colloid formed in the solution. After allowing the solution to stand, the clear, transparent middle layer of the filtrate is taken, and the sodium fluorescein content is measured using a fluorescence spectrophotometer. This method, by adding ammonium aluminum sulfate, a co-precipitant reagent that does not affect the fluorescein measurement results, allows the fiber suspension to settle or aggregate, thereby accurately measuring the sodium fluorescein concentration in the filtrate.

[0043] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A method for detecting sodium fluorescein for detecting the efficiency of high-efficiency filters, comprising the following steps: S1. Inject sodium fluorescein upstream of the ventilation system, and place the sampling clip with the filter membrane installed at the upstream and downstream sampling ports of the high-efficiency filter for sampling; S2. After sampling, immerse the filter membrane in the sampling clip in a weakly alkaline solution to form a fiber suspension. S3. After soaking, use an alkaline reagent to adjust the pH of the fiber suspension to be alkaline. S4. Add an appropriate amount of co-precipitant to the fiber suspension, stir the solution evenly and let it stand. The fiber suspension will settle or aggregate. S5. After the solution has been allowed to stand, take an appropriate amount of the clear and transparent intermediate layer of the soaking solution and use a fluorescence spectrophotometer to measure the content of sodium fluorescein in the soaking solution. The weak alkaline solution used in step S2 is ammonia water with a concentration of 0.5-1%, and the soaking time is 15-20 minutes; the volume of ammonia water is 20 ml. In step S3, the pH of the fiber suspension is adjusted to 9-12 using a 1 mol / L potassium hydroxide solution. The coprecipitant added in step S4 is selected from one or more of the following: ammonium aluminum sulfate NH4Al(SO4)2, alum AL2(SO4)3.K2SO4.24H2O or aluminum sulfate AL2(SO4)3.18H2O; In step S5, use a dropper to take out 3-5 ml of the clear and transparent soaking solution from the middle part, place the soaking solution in a cuvette, and use a fluorescence spectrophotometer to measure the content of sodium fluorescein.

2. The method for detecting sodium fluorescein for detecting the efficiency of high-efficiency filters according to claim 1, characterized in that, In step S1, sodium fluorescein is injected using a sodium fluorescein generator, and the appropriate generation rate is set according to the system air volume.

3. The method for detecting sodium fluorescein for detecting the efficiency of high-efficiency filters according to claim 2, characterized in that, The sampling flow rate in step S1 is 32-40 L / h.

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