Method for Determining Ammonia Nitrogen Content in Fluoride-Containing Radioactive Wastewater

Abstract

The method for determining the ammonia nitrogen content in fluorine-containing radioactive wastewater is applied to a measuring system, wherein the measuring system includes a carrier gas supply device, a gas-liquid separation device, a gas phase molecular absorption spectrometer and a computer; the steps are as follows: 1. Defluorination treatment of water sample: take 1 volume portion of water sample, add an appropriate amount of anhydrous calcium chloride and stir to make the F in the water ‑ 1. Convert it into CaF2 precipitate, and then filter out the CaF2 precipitate in the water sample; 2. Remove other interference items in the water sample; 3. Draw an ammonia nitrogen standard curve; 4. Determine the ammonia nitrogen content in the water sample. The present invention is suitable for detecting the ammonia nitrogen content in the wastewater produced in the process of nuclear fuel preparation, and has simple operation, easy implementation, and good accuracy and precision.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater component determination methods, in particular to a method for determining ammonia nitrogen content in fluorine-containing radioactive wastewater. Background Art

[0002] my country has always had strict requirements on the ammonia nitrogen content in industrial wastewater. At present, relevant enterprises mainly test the ammonia nitrogen content in wastewater based on HJ / T195-2005 "Water Quality-Determination of Ammonia Nitrogen-Gas Phase Molecular Absorption Spectrometry". However, this set of testing standards is not applicable to certain special fields / industries and has certain limitations.

[0003] In the nuclear industry, the preparation of nuclear fuel is at the upstream of the entire industrial chain. The nuclear fuel preparation process will go through two steps: uranium purification and uranium conversion. Uranium purification refers to the production process from uranium ore concentrate to refined UO2, and uranium conversion refers to the production process from refined UO2 to UF6.

[0004] A certain amount of fluorine-containing radioactive wastewater is produced in the nuclear fuel preparation process. On the one hand, the wastewater contains trace amounts of radioactive uranium elements, and on the other hand, the fluorine in the wastewater exists in the form of hydrofluoric acid (HF). At this time, if HJ / T195-2005 "Water Quality - Determination of Ammonia Nitrogen - Gas Phase Molecular Absorption Spectrometry" is used to detect the ammonia nitrogen content in the wastewater produced in the nuclear fuel preparation process, there will be the following problems that need to be overcome: 1. The hydrofluoric acid (HF) in the wastewater is highly corrosive and will corrode the internal pipes of the gas phase molecular spectrometer; 2. Whether the trace amount of radioactive uranium elements in the wastewater will interfere with the detection of ammonia nitrogen content, thereby affecting the accuracy of ammonia nitrogen content detection, there is no relevant research report yet. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for determining the ammonia nitrogen content in fluorine-containing radioactive wastewater, which solves the problem that the currently widely used HJ / T195-2005 "Water Quality-Determination of Ammonia Nitrogen-Gas Phase Molecular Absorption Spectrometry" is not suitable for detecting the ammonia nitrogen content in wastewater generated in the nuclear fuel preparation process.

[0006] The technical scheme of the present invention is: a method for determining the ammonia nitrogen content in fluorine-containing radioactive wastewater is applied to a measuring system, wherein the measuring system comprises a carrier gas supply device, a gas-liquid separation device, a gas-phase molecular absorption spectrometer and a computer; the carrier gas supply device is connected to the gas-liquid separation device through an air pipe, the gas-liquid separation device is connected to the gas-phase molecular absorption spectrometer through an air pipe, and the computer is electrically connected to the gas-phase molecular absorption spectrometer; the steps are as follows:

[0007] S01, water sample defluorination treatment:

[0008] a. Collect the water sample in a sample bottle, add sulfuric acid until the pH is less than 2, and store at 2-5°C for later use;

[0009] b. Take 1 volume of water sample, add appropriate amount of anhydrous calcium chloride and stir to make the F in the water - Converted into CaF2 precipitate, and then filtered out the CaF2 precipitate in the water sample;

[0010] S02, remove other interferences in the water sample: add 3 volumes of the mixed solution to the above defluorinated water sample, add pure water to make it 1000ml, and then heat and boil the water sample to remove the following interferences: NO2 - 、SO3 2- and sulfides;

[0011] S03, draw the ammonia nitrogen standard curve:

[0012] a. Open the valve of the carrier gas supply device to allow the carrier gas to pass through the gas-liquid separation device and the gas phase molecular absorption spectrometer in sequence to purify the measurement system;

[0013] b. Prepare a nitrite standard working solution with a concentration of 4.0 ml / L, wherein the solvent of the nitrite standard working solution is water and the solute is spectral sodium nitrite dried at 105-110° C. for 4 hours;

[0014] c. Take different volumes of nitrite standard solution and prepare the following nitrite dilution solutions with gradient concentrations: 0ppm, 0.2ppm, 0.5ppm, 1ppm, 1.5ppm, 2ppm;

[0015] d. Use gas phase molecular absorption spectrometer to measure the absorbance of nitrite dilutions of different concentrations in turn, and draw a standard curve based on the absorbance and the corresponding ammonia nitrogen content;

[0016] S04, determination of ammonia nitrogen content in water samples:

[0017] First, a blank sample is measured by gas phase molecular absorption spectrometer to perform blank correction; a certain amount of water sample with interference components removed is placed in a gas-liquid separation device, and the ammonia nitrogen content in the water sample is measured by gas phase molecular absorption spectrometer;

[0018] Ammonia nitrogen content η (mg / L) is calculated according to the following formula:

[0019] In the formula, m is the amount of ammonia nitrogen in the water sample calculated according to the standard curve, um; m0 is the blank amount calculated according to the standard curve, ug; V is the sampling volume, ml.

[0020] The technical scheme of the present invention is: a method for verifying whether uranium element affects the accuracy of ammonia nitrogen determination results of water samples, which is applied to a measuring system, wherein the measuring system comprises a carrier gas supply device, a gas-liquid separation device, a gas-phase molecular absorption spectrometer and a computer; the carrier gas supply device is connected with the gas-liquid separation device through an air pipe, the gas-liquid separation device is connected with the gas-phase molecular absorption spectrometer through an air pipe, and the computer is electrically connected with the gas-phase molecular absorption spectrometer;

[0021] Here are the steps:

[0022] S01, draw the ammonia nitrogen standard curve:

[0023] a. Open the valve of the carrier gas supply device to allow the carrier gas to pass through the gas-liquid separation device and the gas phase molecular absorption spectrometer in sequence to purify the measurement system;

[0024] b. Prepare a nitrite standard working solution with a concentration of 4.0 ml / L, wherein the solvent of the nitrite standard working solution is water and the solute is spectral sodium nitrite dried at 105-110° C. for 4 hours;

[0025] c. Take different volumes of nitrite standard solution and prepare the following nitrite dilution solutions with gradient concentrations: 0ppm, 0.2ppm, 0.5ppm, 1ppm, 1.5ppm, 2ppm;

[0026] d. Use gas phase molecular absorption spectrometer to measure the absorbance of nitrite dilutions of different concentrations in turn, and draw a standard curve based on the absorbance and the corresponding ammonia nitrogen content;

[0027] S02, prepare water samples and defluorinate them:

[0028] a. Prepare four water samples with uranium content of 0, 10, 50, and 100 mg / L, and the ammonia nitrogen content of each concentration of water sample is 4 mg / L;

[0029] b. Collect water samples of different concentrations in different sample bottles, add sulfuric acid until the pH is less than 2, and store at 2-5°C for later use;

[0030] c. Take 1 volume of water sample of each concentration, add appropriate amount of anhydrous calcium chloride and stir to make the F in the water - Converted into CaF2 precipitate, and then filtered out the CaF2 precipitate in the water sample;

[0031] S03, remove other interferences in the water sample: add 3 volumes of the mixed solution to the above defluorinated water samples of each concentration, add pure water to make the volume 1000ml, and then heat and boil the water sample to remove the following interference components: and sulfides;

[0032] S04, determine the ammonia nitrogen content in water samples of different concentrations and compare them horizontally:

[0033] First, a blank sample is measured by gas phase molecular absorption spectrometer for blank correction; then a certain amount of water sample with interfering components removed is placed in a gas-liquid separation device, and the ammonia nitrogen content in each concentration of water sample is measured by gas phase molecular absorption spectrometer; finally, the measurement results of four concentrations of water samples with uranium content of 0, 10, 50, and 100 mg / L are compared horizontally, and the percentage difference between the actual measured ammonia nitrogen concentration and the configured ammonia nitrogen concentration of the four concentrations of water samples is compared. When the difference does not exceed ±5%, it is considered that the uranium content in the water sample is between 0 and 100 mg / L and does not affect the accuracy of the measurement result of the ammonia nitrogen content in the water sample.

[0034] Ammonia nitrogen content η (mg / L) is calculated according to the following formula:

[0035] In the formula, m is the amount of ammonia nitrogen in the water sample calculated according to the standard curve, um; m0 is the blank amount calculated according to the standard curve, ug; V is the sampling volume, ml.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] 1. It is suitable for detecting the ammonia nitrogen content in the wastewater produced during the preparation of nuclear fuel. It is simple to operate, easy to implement, and has good accuracy and precision. On the one hand, it removes the fluorine element in the water sample through simple pretreatment, avoiding the corrosion of the pipes in the measurement system by the water sample containing hydrofluoric acid. On the other hand, it verifies that when the uranium content in the wastewater is between 0 and 100 mg / L, it will not affect the accuracy of the ammonia nitrogen measurement results.

[0038] 2. It is suitable for the determination of ammonia nitrogen in fluorine-containing radioactive surface water, groundwater, domestic sewage and industrial sewage, with a minimum detection limit of 0.005 mg / L. DETAILED DESCRIPTION

[0039] Embodiment 1:

[0040] The method for determining the ammonia nitrogen content in fluorine-containing radioactive wastewater is applied to a measuring system, wherein the measuring system comprises a carrier gas supply device, a gas-liquid separation device, a gas-phase molecular absorption spectrometer and a computer; the carrier gas supply device is connected to the gas-liquid separation device through an air pipe, the gas-liquid separation device is connected to the gas-phase molecular absorption spectrometer through an air pipe, and the computer is electrically connected to the gas-phase molecular absorption spectrometer.

[0041] The steps are as follows:

[0042] S01, water sample defluorination treatment:

[0043] a. Collect the water sample in a sample bottle, add sulfuric acid until the pH is less than 2, and store at 2-5°C for later use;

[0044] b. Take 1 volume of water sample, add appropriate amount of anhydrous calcium chloride and stir to make the F in the water - Converted into CaF2 precipitate, and then filter out the CaF2 precipitate in the water sample.

[0045] In sub-step a of this step, the sample bottle is a polyethylene bottle or a glass bottle; when collecting wastewater and acidifying, avoid the water sample absorbing ammonia in the air and being contaminated; the storage period of the water sample is only 24 hours.

[0046] In sub-step b of this step, the reaction that occurs is as follows: 2F+CaCl2→CaF2↓+2Cl.

[0047] In sub-step b of this step, the amount of anhydrous calcium chloride added and the fluoride ion content in the water sample have the following corresponding relationship: when the fluoride ion content is between 5000 and 10000 mg / L, the amount of anhydrous calcium fluoride added is 0.5 g; when the fluoride ion content is between 10000 and 20000 mg / L, the amount of anhydrous calcium fluoride added is 1.0 g; when the fluoride ion content is between 20000 and 50000 mg / L, the amount of anhydrous calcium fluoride added is 2.0 g.

[0048] S02, remove other interferences in the water sample: add 3 volumes of the mixed solution to the above defluorinated water sample, add pure water to make it 1000ml, and then heat and boil the water sample to remove the following interferences: NO2 - 、SO3 2- and sulfides.

[0049] In this step, the mixed solution is prepared by mixing 25% v / v hydrochloric acid and anhydrous ethanol in a volume ratio of 5:1. After the mixed solution is prepared, it is left open for 24 hours and then sealed and stored for later use.

[0050] S03, draw the ammonia nitrogen standard curve:

[0051] a. Open the valve of the carrier gas supply device to allow the carrier gas to pass through the gas-liquid separation device and the gas phase molecular absorption spectrometer in sequence to purify the measurement system;

[0052] b. Prepare a nitrite standard working solution with a concentration of 4.0 ml / L, wherein the solvent of the nitrite standard working solution is water and the solute is spectral sodium nitrite dried at 105-110° C. for 4 hours;

[0053] c. Take different volumes of nitrite standard solution and prepare the following nitrite dilution solutions with gradient concentrations: 0ppm, 0.2ppm, 0.5ppm, 1ppm, 1.5ppm, 2ppm;

[0054] d. Use gas phase molecular absorption spectrometer to measure the absorbance of nitrite dilutions of different concentrations in turn, and draw a standard curve based on the absorbance and the corresponding ammonia nitrogen content.

[0055] In this step, the carrier gas is nitrogen with a purity of 99.999%.

[0056] S04, determination of ammonia nitrogen content in water samples:

[0057] First, a blank sample is measured by gas phase molecular absorption spectrometer to perform blank correction; a certain amount of water sample with interfering components removed is placed in a gas-liquid separation device, and the ammonia nitrogen content in the water sample is measured by gas phase molecular absorption spectrometer.

[0058] Ammonia nitrogen content η (mg / L) is calculated according to the following formula:

[0059] In the formula, m is the amount of ammonia nitrogen in the water sample calculated according to the standard curve, um; m0 is the blank amount calculated according to the standard curve, ug; V is the sampling volume, ml.

[0060] Description of the defluoridation effect of water samples:

[0061] When fluoride-containing water samples are distilled and separated, the fluoride-containing vapor will cause serious corrosion to glassware and other equipment, making it difficult to eliminate interference. Taking advantage of the fact that calcium fluoride is insoluble in water, an appropriate amount of calcium chloride is added to the water sample to convert all fluorides into calcium fluoride precipitation for removal. Because calcium fluoride is slightly soluble in inorganic acids, the water sample is first adjusted to neutral, then an appropriate amount of calcium chloride is added, and finally the water sample is filtered or allowed to stand, and the supernatant is extracted for measurement on the machine.

[0062] Sodium fluoride standard solution was used to prepare two water samples with fluoride ion content of 10000mg / L and 15000mg / L respectively. 1g calcium chloride was added to each of the two water samples with different fluoride ion concentrations to remove fluoride ions in the water samples. The test results showed that after adding calcium chloride, the fluoride ion concentration in the water samples decreased from 10000mg / L and 15000mg / L to 11.41mg / L and 11.84mg / L respectively, and the fluoride ion separation effect was obvious.

[0063] Explanation on the accuracy of ammonia nitrogen content determination after defluorination of water samples:

[0064] After fluoride ion separation, 4.0 mg / L ammonia nitrogen standard solution was added to water sample 1 and water sample 2, respectively, and the ammonia nitrogen content was determined (water sample 1 and water sample 2 were determined 4 times respectively). The results are shown in Tables 1 and 2.

[0065] Table 1: Determination results of ammonia nitrogen in water sample 1 after separation of fluoride ions

[0066]

[0067] Table 2: Determination results of ammonia nitrogen in water sample 2 after separation of fluoride ions

[0068]

[0069]

[0070] The measurement results show that the ammonia nitrogen content in the water samples after fluoride removal is stable. After statistical calculation of the data, the error of the conclusion is acceptable, indicating that this method has high precision when measuring samples.

[0071] Instructions for verifying whether uranium affects the accuracy of ammonia nitrogen determination results in water samples:

[0072] In the fluorine-containing radioactive wastewater generated in the nuclear fuel preparation process, the main components of the matrix are uranyl and fluoride ions. Fluoride ions are separated by precipitation using calcium chloride to eliminate interference and corrosion; the interference of uranium elements on the measurement needs to be verified. In the above wastewater, the uranium content usually ranges from 1mg / L to 100mg / L. Therefore, four water samples with uranium content in a concentration gradient (0, 10, 50, 100mg / L) were prepared for verification. The verification results are shown in Tables 3, 4, 5, and 6.

[0073] Table 3: Determination results of ammonia nitrogen in water samples containing uranium (10 mg / L)

[0074]

[0075] Table 4: Determination results of ammonia nitrogen in water samples containing uranium (50 mg / L)

[0076]

[0077] Table 5: Determination results of ammonia nitrogen in water samples containing uranium (100 mg / L)

[0078]

[0079] Table 5: Determination results of ammonia nitrogen in water samples containing uranium (0 mg / L)

[0080]

[0081] The measurement results show that the differences between the actual measured ammonia nitrogen concentrations of the four water samples and the configured ammonia nitrogen concentrations do not exceed ±2%. Therefore, it is believed that the uranium content in the water samples between 0 and 100 mg / L does not affect the accuracy of the measurement results of the ammonia nitrogen content in the water samples.

[0082] The verification steps are as follows:

[0083] 1. Draw the ammonia nitrogen standard curve:

[0084] a. Open the valve of the carrier gas supply device to allow the carrier gas to pass through the gas-liquid separation device and the gas phase molecular absorption spectrometer in sequence to purify the measurement system;

[0085] b. Prepare a nitrite standard working solution with a concentration of 4.0 ml / L, wherein the solvent of the nitrite standard working solution is water and the solute is spectral sodium nitrite dried at 105-110° C. for 4 hours;

[0086] c. Take different volumes of nitrite standard solution and prepare the following nitrite dilution solutions with gradient concentrations: 0ppm, 0.2ppm, 0.5ppm, 1ppm, 1.5ppm, 2ppm;

[0087] d. Use gas phase molecular absorption spectrometer to measure the absorbance of nitrite dilutions of different concentrations in turn, and draw a standard curve based on the absorbance and the corresponding ammonia nitrogen content;

[0088] In this step, the carrier gas is nitrogen with a purity of 99.999%.

[0089] 2. Prepare water samples and defluorinate them:

[0090] a. Prepare four water samples with uranium content of 0, 10, 50, and 100 mg / L, and the ammonia nitrogen content of each concentration of water sample is 4 mg / L;

[0091] b. Collect water samples of different concentrations in different sample bottles, add sulfuric acid until the pH is less than 2, and store at 2-5°C for later use;

[0092] c. Take 1 volume of water sample of each concentration, add appropriate amount of anhydrous calcium chloride and stir to make the F in the water - Converted into CaF2 precipitate, and then filtered out the CaF2 precipitate in the water sample;

[0093] In sub-step b of this step, the sample bottle is a polyethylene bottle or a glass bottle; when collecting wastewater and acidifying, avoid the water sample absorbing ammonia in the air and being contaminated; the storage time limit of the water sample is only 24 hours;

[0094] In sub-step b of this step, the reaction that occurs is as follows: 2F+CaCl2→CaF2↓+2Cl;

[0095] In sub-step b of this step, the amount of anhydrous calcium chloride added and the fluoride ion content in the water sample have the following corresponding relationship: when the fluoride ion content is between 5000 and 10000 mg / L, the amount of anhydrous calcium fluoride added is 0.5 g; when the fluoride ion content is between 10000 and 20000 mg / L, the amount of anhydrous calcium fluoride added is 1.0 g; when the fluoride ion content is between 20000 and 50000 mg / L, the amount of anhydrous calcium fluoride added is 2.0 g.

[0096] 3. Remove other interferences in the water sample: Add 3 volumes of the mixed solution to the above defluorinated water samples of each concentration, and then add pure water to make up to 1000ml, then heat and boil the water sample to remove the following interference components: NO2 - 、SO3 2- and sulfides;

[0097] In this step, the mixed solution is prepared by mixing 25% v / v hydrochloric acid and anhydrous ethanol in a volume ratio of 5:1. After the mixed solution is prepared, it is left open for 24 hours and then sealed and stored for later use.

[0098] 4. Determine the ammonia nitrogen content in water samples of different concentrations and make a horizontal comparison:

[0099] First, a blank sample is measured by a gas phase molecular absorption spectrometer to perform blank correction; then a certain amount of water sample with interference components removed is placed in a gas-liquid separation device, and the ammonia nitrogen content in each concentration of the water sample is measured by a gas phase molecular absorption spectrometer; finally, the measurement results of the four concentrations of water samples with uranium content of 0, 10, 50, and 100 mg / L are compared horizontally, and the percentage difference between the actual measured ammonia nitrogen concentration of the four concentrations of water samples and the ammonia nitrogen configuration concentration is compared. When the difference does not exceed ±5%, it is considered that the uranium content in the water sample is between 0 and 100 mg / L and does not affect the accuracy of the measurement result of the ammonia nitrogen content in the water sample;

[0100] Ammonia nitrogen content η (mg / L) is calculated according to the following formula:

[0101] In the formula, m is the amount of ammonia nitrogen in the water sample calculated according to the standard curve, um; m0 is the blank amount calculated according to the standard curve, ug; V is the sampling volume, ml.

Claims

1. A method for determining the ammonia nitrogen content in fluorine-containing radioactive wastewater, applied to a measuring system, wherein the measuring system comprises a carrier gas supply device, a gas-liquid separation device, a gas-phase molecular absorption spectrometer and a computer; the carrier gas supply device is connected to the gas-liquid separation device through an air pipe, the gas-liquid separation device is connected to the gas-phase molecular absorption spectrometer through an air pipe, and the computer is electrically connected to the gas-phase molecular absorption spectrometer; Its characteristic is that the steps as follows: S01, water sample defluorination treatment: a. Collect the water sample in a sample bottle, add sulfuric acid until the pH is less than 2, and store at 2-5°C for later use; b. Take 1 volume of water sample, add appropriate amount of anhydrous calcium chloride and stir to make the F in the water - Converted into CaF2 precipitate, and then filtered out the CaF2 precipitate in the water sample; In step a of this step, the sample bottle is a polyethylene bottle or a glass bottle; when collecting wastewater and acidifying, avoid the water sample absorbing ammonia in the air and being contaminated; the storage time limit of the water sample is only 24 hours; In sub-step b of this step, the reaction that occurs is as follows: 2F+CaCl2→CaF2↓+2Cl; S02, remove other interferences in the water sample: add 3 volumes of the mixed solution to the above defluorinated water sample, add pure water to make it 1000ml, and then heat and boil the water sample to remove the following interferences: NO2 - 、SO3 2- and sulfides; In this step, the mixed solution is prepared by mixing 25% v / v hydrochloric acid and anhydrous ethanol in a volume ratio of 5:

1. After the mixed solution is prepared, it is left open for 24 hours and then sealed and stored for later use. S03, draw the ammonia nitrogen standard curve: a. Open the valve of the carrier gas supply device to allow the carrier gas to pass through the gas-liquid separation device and the gas phase molecular absorption spectrometer in sequence to purify the measurement system; b. Prepare a nitrite standard working solution with a concentration of 4.0 ml / L, wherein the solvent of the nitrite standard working solution is water and the solute is spectral sodium nitrite dried at 105-110° C. for 4 hours; c. Take different volumes of nitrite standard solution and prepare the following nitrite dilution solutions with gradient concentrations: 0ppm, 0.2ppm, 0.5ppm, 1ppm, 1.5ppm, 2ppm; d. Use gas phase molecular absorption spectrometer to measure the absorbance of nitrite dilutions of different concentrations in turn, and draw a standard curve based on the absorbance and the corresponding ammonia nitrogen content; S04, determination of ammonia nitrogen content in water samples: First, a blank sample is measured by gas phase molecular absorption spectrometer to perform blank correction; a certain amount of water sample with interference components removed is placed in a gas-liquid separation device, and the ammonia nitrogen content in the water sample is measured by gas phase molecular absorption spectrometer; The ammonia nitrogen content η is calculated according to the following formula: In the formula, m is the amount of ammonia nitrogen in the water sample calculated according to the standard curve, um; m0 is the blank amount calculated according to the standard curve, ug; V is the sampling volume, ml.

2. The method for determining the ammonia nitrogen content in fluorine-containing radioactive wastewater according to claim 1, characterized in that: In sub-step b of step S01, the amount of anhydrous calcium chloride added and the fluoride ion content in the water sample have the following corresponding relationship: when the fluoride ion content is between 5000 and 10000 mg / L, the amount of anhydrous calcium fluoride added is 0.5 to 0.55 g; when the fluoride ion content is between 10000 and 20000 mg / L, the amount of anhydrous calcium fluoride added is 1.0 to 1.1 g; when the fluoride ion content is between 20000 and 50000 mg / L, the amount of anhydrous calcium fluoride added is 2.0 to 2.2 g.

3. The method for determining the ammonia nitrogen content in fluorine-containing radioactive wastewater according to claim 2, characterized in that: In sub-step b of step S01, the amount of anhydrous calcium chloride added and the fluoride ion content in the water sample have the following corresponding relationship: when the fluoride ion content is between 5000 and 10000 mg / L, the amount of anhydrous calcium fluoride added is 0.5 g; when the fluoride ion content is between 10000 and 20000 mg / L, the amount of anhydrous calcium fluoride added is 1.0 g; when the fluoride ion content is between 20000 and 50000 mg / L, the amount of anhydrous calcium fluoride added is 2.0 g.

4. The method for determining the ammonia nitrogen content in fluorine-containing radioactive wastewater according to claim 3, characterized in that: In step S03, the carrier gas is nitrogen with a purity of 99.999%.

5. A method for verifying whether uranium element affects the accuracy of the ammonia nitrogen determination result of a water sample, which is applied to a measuring system, wherein the measuring system comprises a carrier gas supply device, a gas-liquid separation device, a gas-phase molecular absorption spectrometer and a computer; the carrier gas supply device is connected to the gas-liquid separation device through an air pipe, the gas-liquid separation device is connected to the gas-phase molecular absorption spectrometer through an air pipe, and the computer is electrically connected to the gas-phase molecular absorption spectrometer; Its characteristic is that the steps as follows: S01, draw the ammonia nitrogen standard curve: a. Open the valve of the carrier gas supply device to allow the carrier gas to pass through the gas-liquid separation device and the gas phase molecular absorption spectrometer in sequence to purify the measurement system; b. Prepare a nitrite standard working solution with a concentration of 4.0 ml / L, wherein the solvent of the nitrite standard working solution is water and the solute is spectral sodium nitrite dried at 105-110° C. for 4 hours; c. Take different volumes of nitrite standard solution and prepare the following nitrite dilution solutions with gradient concentrations: 0ppm, 0.2ppm, 0.5ppm, 1ppm, 1.5ppm, 2ppm; d. Use gas phase molecular absorption spectrometer to measure the absorbance of nitrite dilutions of different concentrations in turn, and draw a standard curve based on the absorbance and the corresponding ammonia nitrogen content; In this step, the carrier gas is nitrogen with a purity of 99.999%; S02, prepare water samples and defluorinate them: a. Prepare four water samples with uranium content of 0, 10, 50, and 100 mg / L, and the ammonia nitrogen content of each concentration of water sample is 4 mg / L; b. Collect water samples of different concentrations in different sample bottles, add sulfuric acid until the pH is less than 2, and store at 2-5°C for later use; c. Take 1 volume of water sample of each concentration, add appropriate amount of anhydrous calcium chloride and stir to make the F in the water - Converted into CaF2 precipitate, and then filtered out the CaF2 precipitate in the water sample; In sub-step b of this step, the sample bottle is a polyethylene bottle or a glass bottle; when collecting wastewater and acidifying, avoid the water sample absorbing ammonia in the air and being contaminated; the storage time limit of the water sample is only 24 hours; In sub-step b of this step, the reaction that occurs is as follows: 2F+CaCl2→CaF2↓+2Cl; In sub-step b of this step, the amount of anhydrous calcium chloride added and the fluoride ion content in the water sample have the following corresponding relationship: when the fluoride ion content is between 5000 and 10000 mg / L, the amount of anhydrous calcium fluoride added is 0.5 g; when the fluoride ion content is between 10000 and 20000 mg / L, the amount of anhydrous calcium fluoride added is 1.0 g; when the fluoride ion content is between 20000 and 50000 mg / L, the amount of anhydrous calcium fluoride added is 2.0 g; S03, remove other interferences in the water sample: add 3 volumes of the mixed solution to the above defluorinated water samples of each concentration, and then add pure water to make the volume 1000ml, and then heat and boil the water sample to remove the following interference components: and sulfides; In this step, the mixed solution is prepared by mixing 25% v / v hydrochloric acid and anhydrous ethanol in a volume ratio of 5:

1. After the mixed solution is prepared, it is left open for 24 hours and then sealed and stored for later use. S04, determine the ammonia nitrogen content in water samples of different concentrations and compare them horizontally: First, a blank sample is measured by a gas phase molecular absorption spectrometer to perform blank correction; then a certain amount of water sample with interference components removed is placed in a gas-liquid separation device, and the ammonia nitrogen content in each concentration of the water sample is measured by a gas phase molecular absorption spectrometer; finally, the measurement results of the four concentrations of water samples with uranium content of 0, 10, 50, and 100 mg / L are compared horizontally, and the percentage difference between the actual measured ammonia nitrogen concentration of the four concentrations of water samples and the ammonia nitrogen configuration concentration is compared. When the difference does not exceed ±5%, it is considered that the uranium content in the water sample is between 0 and 100 mg / L and does not affect the accuracy of the measurement result of the ammonia nitrogen content in the water sample; The ammonia nitrogen content η is calculated according to the following formula: In the formula, m is the amount of ammonia nitrogen in the water sample calculated according to the standard curve, um; m0 is the blank amount calculated according to the standard curve, ug; V is the sampling volume, ml.

Images