Method for determining total alpha and total beta in liquid effluent

Abstract

The invention belongs to the technical field of nuclear environmental protection, and particularly relates to a method for measuring total alpha and total beta in liquid effluent. The method comprises the following steps: drying a sample in a sample plate, and ensuring that the thickness of the sample in the sample plate is less than 1mg / cm < 2 >; and measuring the sample in the sample disc by using a low-background alpha-beta measuring instrument to obtain the alpha-radioactivity specific activity and the beta-radioactivity specific activity of the sample. According to the method, the total alpha and the total beta in the liquid effluent of the nuclear facility are analyzed at the same time by adopting a thin-source method, the analysis time is shortened to 2.5-3 hours from original 7-8 hours, the technical indexes meet the monitoring requirements in the operation period of the nuclear facility, and the analysis of the total alpha and the total beta in the liquid effluent of the nuclear facility can be met.

Description

Technical Field

[0001] The present application belongs to the field of nuclear environmental protection technology, and specifically relates to a method for determining total α and total β in liquid effluent. Background Art

[0002] According to relevant requirements, for the monitoring of liquid effluent, sampling should be carried out when wastewater collection in a discharge tank is completed, and data monitoring should be completed before wastewater collection in the standby tank is completed. This places high demands on the timeliness of monitoring, and a rapid analysis method must be established to meet the needs of continuous operation of the production process.

[0003] The current analysis method for total α and total β in water requires evaporation, concentration, sulfation, and combustion of the sample to produce the sample source to be tested. Its technical parameters can meet the technical requirements for monitoring total α and total β in liquid effluents from nuclear facilities, but this method has a long analysis process, and it usually takes 7 to 8 hours to analyze a sample, which cannot meet the relevant requirements. Summary of the Invention

[0004] The purpose of this application is to provide a method for determining the total α and total β in liquid effluent, so as to solve the problem of long analysis process in the prior art.

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

[0006] The present invention provides a method for determining total α and total β in a liquid effluent, the method comprising:

[0007] Place the sample in a sample tray and dry it to ensure that the thickness of the sample in the sample tray is less than 1 mg / cm 2 ;

[0008] The sample in the sample tray is measured using a low-background αβ measuring instrument to obtain the α radioactivity specific activity and the β radioactivity specific activity of the sample.

[0009] Optionally, the sample is placed in a sample tray and dried to ensure that the thickness of the sample in the sample tray is less than 1 mg / cm 2 , specifically including:

[0010] Taking a predetermined amount of the sample into a beaker and adding nitric acid to acidify it;

[0011] Place the beaker on a heater to heat and evaporate, then transfer it to the sample tray so that the thickness of the sample in the sample tray is less than 1 mg / cm 2 .

[0012] Optionally, taking a predetermined amount of the sample into a beaker and acidifying it by adding nitric acid specifically includes:

[0013] 20 ml of the aqueous solution of the sample was measured and placed in a 100 ml beaker, and acidified to pH = 2 with nitric acid.

[0014] Optionally, placing the beaker on a heater for heating and evaporation and then transferring the beaker into the sample tray specifically includes:

[0015] Place the beaker on a heater and heat to evaporate to 5 ml, then transfer it to the φ45 mm sample pan;

[0016] Wash the beaker 2-3 times with distilled water, and transfer the washing solution into the sample tray;

[0017] The sample plate is placed on a hot plate for drying or dried under a drying lamp.

[0018] Optionally, measuring the sample in the sample tray using a low-background αβ measuring instrument to obtain the α radioactivity specific activity and β radioactivity specific activity of the sample specifically includes:

[0019] The sample in the sample tray is placed on the low-background αβ measuring instrument for sample measurement. The measurement time is 80 minutes to obtain the α radioactivity specific activity and β radioactivity specific activity of the sample.

[0020] Optionally, the α radioactivity specific activity and the β radioactivity specific activity of the sample are determined according to the following formulas (1) and (2):

[0021] A α =(n c -n b )×10 3 / 60×η α R α V (1)

[0022] A β =(n c -n b )×10 3 / 60×η β R β V (2)

[0023] Where A α A is the α radioactivity specific activity of the sample; β is the β radioactivity specific activity of the sample; n c is the counting rate of the sample; n b is the background count rate; V is the measurement amount of the sample; η α is the α detection efficiency of the low-background αβ measuring instrument; η β is the β detection efficiency of the low-background αβ measuring instrument; R α is the spike recovery rate of α; R β is the β spike recovery.

[0024] Optionally, the measuring of the sample in the sample tray by using a low-background αβ measuring instrument may also include:

[0025] Perform background measurement on the low-background αβ measuring instrument.

[0026] Optionally, the total time for the background measurement and the sample measurement does not exceed 100 minutes.

[0027] The beneficial technical effects of this application are:

[0028] The present invention provides a method for determining the total α and total β in a liquid effluent, comprising: placing the sample in a sample tray and drying it to ensure that the thickness of the sample in the sample tray is less than 1 mg / cm 2 The sample in the sample tray is measured using a low-background αβ meter to obtain the sample's α and β radioactivity specific activities. This embodiment of the present application employs a thin-source method to simultaneously analyze total α and total β in liquid effluent from nuclear facilities, shortening the analysis time from 7 to 8 hours to 2.5 to 3 hours. The technical specifications meet the requirements for monitoring during nuclear facility operation and can be used for analyzing total α and total β in liquid effluent from nuclear facilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic flow chart of a method for determining total α and total β in a liquid effluent provided in an embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the embodiments described below are only part of the embodiments of the present application, not all of them. Based on the embodiments recorded in this application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0031] See also Figure 1 , which is a schematic flow chart of a method for determining total α and total β in liquid effluent provided in an embodiment of the present application.

[0032] The present invention provides a method for determining total α and total β in a liquid effluent, comprising:

[0033] Step S101: Place the sample in a sample tray and dry it to ensure that the thickness of the sample in the sample tray is less than 1 mg / cm 2 ;

[0034] Step S102: using a low-background αβ measuring instrument to measure the sample in the sample tray to obtain the α radioactivity specific activity and the β radioactivity specific activity of the sample.

[0035] In this application, a thin sample source is prepared for simultaneous measurement of total α and total β. A thin calibration source is also prepared for measuring instrument calibration. The relative measurement method is used to give the α and total β activity concentrations in the sample source. When measuring the total α of a sample using the thin source method, the thickness of the dried sample in the sample tray must be less than 1 mg / cm. 2 At this point, the instrument's detection efficiency can be roughly considered equal to that of a thin α radiation source directly calibrated. This method can effectively reduce analysis time from the original 7 to 8 hours to 2.5 to 3 hours. The total spiked water sample recovery rate is >70% for total α and >80% for total β. The detection limit is MDA. α <5×10 -1 Bq / l, MDA β <5×10 0 Bq / l; accuracy is better than 30%; technical indicators meet the requirements of monitoring during the operation of nuclear facilities and can be used for the analysis of total α and total β in liquid effluents of nuclear facilities.

[0036] In some possible implementations of the embodiments of the present application, step S101 may specifically include:

[0037] Taking a predetermined amount of the sample into a beaker and adding nitric acid to acidify it;

[0038] Place the beaker on a heater to heat and evaporate, then transfer it to the sample tray so that the thickness of the sample in the sample tray is less than 1 mg / cm 2 .

[0039] In one example, taking a predetermined amount of the sample into a beaker and acidifying it with nitric acid may specifically include:

[0040] 20 ml of the aqueous solution of the sample was measured and placed in a 100 ml beaker, and acidified to pH = 2 with nitric acid.

[0041] It is understood that in specific implementation, 50 wastewater samples of a certain type can be randomly selected according to each sampling volume, such as 10ml, 20ml, 30ml, 40ml, and 50ml, and the amount of water sample residue after evaporation, drying, and weighing. The active area area is calculated as 15.9cm according to the φ45 sample plate. 2 The thin source method requires the sample thickness to be less than 1 mg / cm 2 , that is, the sample residue is required to be less than 15.9 mg. According to the statistical results, the volume of the water sample is determined to be 20 ml.

[0042] In another example, placing the beaker on a heater for heating and evaporation and then transferring the beaker into the sample tray may specifically include:

[0043] Place the beaker on a heater and heat to evaporate to 5 ml, then transfer it to the φ45 mm sample pan;

[0044] Wash the beaker 2-3 times with distilled water, and transfer the washing solution into the sample tray;

[0045] The sample plate is placed on a hot plate for drying or dried under a drying lamp.

[0046] In some possible implementations of the embodiments of the present application, step S102 may specifically include:

[0047] The sample in the sample tray is placed on the low-background αβ measuring instrument for sample measurement. The measurement time is 80 minutes to obtain the α radioactivity specific activity and β radioactivity specific activity of the sample.

[0048] In one example, the α radioactivity specific activity and the β radioactivity specific activity of the sample can be determined according to the following formulas (1) and (2):

[0049] A α =(n c -n b )×10 3 / 60×η α R α V(1)

[0050] A β =(n c -n b )×10 3 / 60×η β R β V(2)

[0051] Where A α A is the α radioactivity specific activity of the sample; β is the β radioactivity specific activity of the sample; n c is the counting rate of the sample; n b is the background count rate; V is the measurement amount of the sample; η α is the α detection efficiency of the low-background αβ measuring instrument; η β is the β detection efficiency of the low-background αβ measuring instrument; R α is the spike recovery rate of α; R β is the β spike recovery.

[0052] It should be noted that the background count fluctuations of the radioactive measurement instrument should conform to the Poisson distribution, and the instrument should be tested for Poisson distribution at least once a year to determine the stability of the instrument. Therefore, in another example, the measurement of the sample in the sample tray using the low-background αβ measurement instrument also includes:

[0053] Perform background measurement on the low-background αβ measuring instrument.

[0054] A thin-scale source is used to calibrate the efficiency of the low-background αβ measuring instrument, and an efficiency stability test is performed. The test data is used to draw an efficiency quality control chart for the instrument, and the requirements of the quality control chart are used to determine whether the instrument efficiency is in a controlled state.

[0055] It should also be noted that when measuring the sample, the time for the sample and background measurements needs to be reasonably allocated so as to minimize the error in the measurement results within the specified total measurement time. As an example, the total time for the background measurement and the sample measurement does not exceed 100 minutes.

[0056] The present invention provides a method for determining total α and total β in liquid effluent, which can effectively reduce the analysis time from 7 to 8 hours to 2.5 to 3 hours. The total α recovery rate of the spiked water sample is >70%, and the total β recovery rate is >80%. The method detection limit (MDA) is α <5×10 -1 Bq / l, MDA β <5×10 0 Bq / l; accuracy is better than 30%; technical indicators meet the requirements of monitoring during the operation of nuclear facilities and can be used for the analysis of total α and total β in liquid effluents of nuclear facilities.

[0057] The present application has been described in detail above with reference to the accompanying drawings and embodiments. However, the present application is not limited to the above embodiments. Various modifications can be made within the scope of knowledge possessed by a person skilled in the art without departing from the purpose of the present application. Any content not described in detail in the present application may be based on existing technologies.

Claims

1. A method for determining total α and total β in a liquid effluent, characterized in that: The method comprises: Place the sample in a sample tray and dry it to ensure that the thickness of the sample in the sample tray is less than 1 mg / cm 2 ; The sample in the sample tray is measured using a low-background αβ measuring instrument to obtain the α radioactivity specific activity and the β radioactivity specific activity of the sample.

2. The method for determining total α and total β in liquid effluent according to claim 1, wherein The sample is placed in a sample tray and dried to ensure that the thickness of the sample in the sample tray is less than 1 mg / cm 2 , specifically including: Taking a predetermined amount of the sample into a beaker and adding nitric acid to acidify it; Place the beaker on a heater to heat and evaporate, then transfer it to the sample tray so that the thickness of the sample in the sample tray is less than 1 mg / cm 2 .

3. The method for determining total α and total β in liquid effluent according to claim 2, characterized in that The method of taking a predetermined amount of the sample into a beaker and acidifying it by adding nitric acid specifically includes: 20 ml of the aqueous solution of the sample was measured and placed in a 100 ml beaker, and acidified to pH = 2 with nitric acid.

4. The method for determining total α and total β in liquid effluent according to claim 2, wherein: Placing the beaker on a heater for heating and evaporation, and then transferring the beaker into the sample tray, specifically includes: Place the beaker on a heater and heat to evaporate to 5 ml, then transfer it to the φ45 mm sample pan; Wash the beaker 2-3 times with distilled water, and transfer the washing solution into the sample tray; The sample plate is placed on a hot plate for drying or dried under a drying lamp.

5. The method for determining total α and total β in liquid effluent according to any one of claims 1 to 4, characterized in that: The method of measuring the sample in the sample tray using a low-background αβ measuring instrument to obtain the α radioactivity specific activity and the β radioactivity specific activity of the sample specifically includes: The sample in the sample tray is placed on the low-background αβ measuring instrument for sample measurement. The measurement time is 80 minutes to obtain the α radioactivity specific activity and β radioactivity specific activity of the sample.

6. The method for determining total α and total β in liquid effluent according to claim 5, characterized in that The α radioactivity specific activity and β radioactivity specific activity of the sample are determined according to the following formulas (1) and (2): A α =(n c -n b )×10 3 / 60×η α R α V (1) A β =(n c -n b )×10 3 / 60×η β R β V (2) Where A α A is the α radioactivity specific activity of the sample; β is the β radioactivity specific activity of the sample; n c is the counting rate of the sample; n b is the background count rate; V is the measurement amount of the sample; η α is the α detection efficiency of the low-background αβ measuring instrument; η β is the β detection efficiency of the low-background αβ measuring instrument; R α is the spike recovery rate of α; R β is the β spike recovery.

7. The method for determining total α and total β in liquid effluent according to claim 5, characterized in that The method further comprises: measuring the sample in the sample tray by using a low-background αβ measuring instrument; Perform background measurement on the low-background αβ measuring instrument.

8. The method for determining total α and total β in liquid effluent according to claim 7, characterized in that The total time for the background measurement and the sample measurement does not exceed 100 minutes.

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