A method for analyzing total alpha in boric acid-containing water

Abstract

This invention belongs to the field of water quality radioactivity detection technology, specifically relating to a method for total alpha analysis in boric acid-containing water. The sample liquid surface in a stainless steel sample measuring pan is heated using an infrared dryer to evaporate the moisture. When crystallization begins to occur in the water sample, or when the water sample is viscous and about to crystallize, ethanol is added to the sample and heating continues. This process of adding ethanol and heating is repeated until the sample is completely evaporated and no crystals are formed. The alpha specific activity is then measured. This invention uses surface heating of the sample, which prevents splashing during the heating process of boric acid-containing samples, avoiding the loss of alpha radionuclides due to liquid splashing, resulting in more accurate measurement results. Ethanol treatment causes the boric acid in the sample to volatilize, avoiding the influence of boric acid on the sample measurement, thus ensuring more accurate results.

Description

Technical Field

[0001] This invention belongs to the field of water quality radioactivity detection technology, specifically relating to a method for total α analysis in boric acid-containing water. Background Technology

[0002] When a fuel cladding breach occurs in a pressurized water reactor nuclear power plant, fuel may be released from the fuel assemblies into the coolant. Alpha radionuclides, primarily transuranic elements, can cause alpha contamination of the system, equipment, and work site, increasing the risk of alpha contamination for workers. When this is suspected, total alpha radioactivity in the coolant needs to be measured to accurately assess the condition of the nuclear fuel assemblies and guide radiation protection measures against alpha radionuclides.

[0003] Currently, my country's standard analytical methods for total alpha include: the international standard ISO 9696-2007 "Water quality - Determination of total alpha in anhydrous water - Thick source method", the national recommended standard GB / T 5750.13-2023 "Standard examination methods for drinking water - Part 13: Radioactivity indicators", and the environmental standard HJ 898-2017 "Determination of total alpha radioactivity in water - Thick source method". The main steps of these methods are similar: the acidified water sample is heated and evaporated to near dryness, the residue is burned at high temperature and ground into powder, the powder is placed in a measuring pan, and the alpha specific activity is measured using a low background alpha measurement system.

[0004] Pressurized water reactor nuclear power plants contain high concentrations of boric acid in their coolants. Using existing standard methods to process samples will produce a large amount of boric acid crystals. Solutions containing boric acid crystals are prone to splashing during heating, and the loss of alpha radionuclides due to splashing will cause inaccurate measurement results. Furthermore, the presence of boric acid crystals in the residue will affect sample preparation and measurement. Therefore, existing methods are not suitable for the total alpha measurement of samples containing boric acid. Summary of the Invention

[0005] The purpose of this invention is to provide a method for total α analysis in boric acid-containing water, so as to solve the problems existing in the current standard total α analysis method for measuring boric acid-containing samples.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for analyzing total α in boric acid-containing water involves heating the surface of the sample liquid in a stainless steel sample measuring pan using an infrared dryer to evaporate the water. When the water sample begins to crystallize or becomes viscous and is about to crystallize, ethanol is added to the sample and heating continues. This process of adding ethanol and heating is repeated until the sample is completely evaporated and no crystals are produced. The α specific activity is then measured.

[0008] Instrument background determination: Take an unused and uncontaminated sample measuring plate, wash it, rinse it with anhydrous ethanol and dry it, and place it on a low background α and β measuring instrument to continuously measure the total α background count rate of the instrument for more than 2 hours.

[0009] Determination of the standard source: Place the sample measuring pan in the drying pan of the infrared dryer, accurately add 5 Bq to 10 Bq of standard substance to the center of the sample measuring pan, add 3 mL of anhydrous ethanol to the sample measuring pan, gently shake the drying pan to make the standard source cover the bottom of the sample measuring pan, put the drying pan into the infrared dryer and heat it to evaporate the liquid in the sample measuring pan, remove the drying pan and let it cool naturally for 3 minutes, measure the total α count rate of the standard source measuring pan on a low background α and β measuring instrument, measure at least three times, each time for 60 minutes, record the average value of the standard source count rate, and record the counting time.

[0010] Preparation of the sample: Place the sample measuring pan in the drying pan of the infrared dryer. Accurately measure 10 mL of sample and slowly add it to the center of the sample measuring pan. Gently shake the sample measuring pan to make the sample cover the bottom of the sample measuring pan. Place the drying pan in the infrared dryer and heat until crystals begin to precipitate. Remove the drying pan and let it cool naturally for 5 minutes. Add 3 mL of anhydrous ethanol to the sample measuring pan and gently shake the drying pan to dissolve the boric acid in the sample. Heat it again in the infrared dryer for 1 minute. Observe carefully during the heating process. When crystals begin to precipitate in the sample measuring pan or the liquid area shrinks, remove the drying pan and use the residual heat of the drying pan to evaporate the remaining ethanol. Let it cool naturally for 3 minutes. Repeat the step of adding anhydrous ethanol and heating until there are no visible crystals. Then repeat the step of adding anhydrous ethanol and heating twice to ensure that the boric acid crystals are completely evaporated.

[0011] Sample determination: After the sample is dried, the total α count rate is measured immediately on a low background α and β measuring instrument. The measurement is performed at least three times, each time for 60 minutes. The average count rate of the standard source is recorded, and the counting time is also recorded.

[0012] Total α activity concentration: A—total α radioactivity concentration in the sample; N s —Sample count rate; N b — Background count rate; E— Detector efficiency; V—Volume of sample evaporated in the measuring disk, detector efficiency Activity data measured on the same day from the α-241Am standard source.

[0013] The results indicate that when the measured result is less than 0.1 Bq / L, three decimal places are retained; when the measured result is greater than or equal to 0.1 Bq / L, three significant figures are retained.

[0014] The beneficial effects achieved by this invention are as follows:

[0015] This invention employs a method of heating the sample surface, which prevents splashing during the heating process of boric acid-containing samples, avoiding the loss of alpha radionuclides due to liquid splashing, and resulting in more accurate measurement results. Ethanol treatment causes the boric acid in the sample to evaporate, avoiding the influence of boric acid on the sample measurement, and resulting in more accurate measurement results. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a method for analyzing total α in boric acid-containing water;

[0017] In the diagram: 1-Infrared dryer; 2-Sand tray; 3-Sample measuring tray. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0019] A method for total α analysis in boric acid-containing water involves heating the surface of the sample liquid in a stainless steel sample measuring pan using an infrared dryer to evaporate the water. When crystallization begins or the sample becomes viscous and is about to crystallize, ethanol is added to the sample, and heating continues. This process of adding ethanol and heating is repeated until the sample is completely evaporated and no crystals are formed. The α specific activity is then measured using a low-background α measurement system. The specific operating procedure is as follows:

[0020] Instrument background determination: Take an unused and uncontaminated sample measuring plate, wash it, rinse it with anhydrous ethanol and dry it, and place it on a low background α and β measuring instrument to continuously measure the total α background count rate of the instrument for more than 2 hours.

[0021] Determination of the standard source: Place the sample measuring pan in the drying pan of the infrared dryer. Accurately add 5 Bq to 10 Bq of standard substance to the center of the sample measuring pan, add 3 mL of anhydrous ethanol to the sample measuring pan, and gently shake the drying pan to ensure the standard source covers the bottom of the sample measuring pan. If the diameter of the sample measuring pan is large, the amount of anhydrous ethanol can be increased appropriately. Place the drying pan in the infrared dryer, turn on the instrument to heat it, and evaporate the liquid in the sample measuring pan to dryness. Remove the drying pan and let it cool naturally for 3 minutes. Measure the total α count rate of the standard source measuring pan on a low-background α and β measuring instrument, at least three times, each time for 60 minutes, record the average value of the standard source count rate, and record the counting time.

[0022] Sample preparation: Place the sample measuring pan in the drying pan of the infrared dryer. Accurately measure 10 mL of sample and slowly add it to the center of the sample measuring pan. Gently shake the sample measuring pan to ensure the sample covers the bottom of the pan. If the diameter of the sample measuring pan is large, the amount of sample can be increased appropriately. Place the drying pan in the infrared dryer, turn on the instrument and heat until crystallization begins, then remove the drying pan and allow it to cool naturally for 5 minutes. Add 3 mL of anhydrous ethanol to the sample measuring pan and gently shake the drying pan to dissolve the boric acid in the sample. Heat again in the infrared dryer for 1 minute, observing carefully during the heating process. When crystallization begins to occur in the sample measuring pan or the liquid area decreases, remove the drying pan and use the residual heat of the drying pan to evaporate the remaining ethanol. Allow it to cool naturally for 3 minutes. Repeat the steps of adding anhydrous ethanol and heating until no crystals are visible to the naked eye. Then repeat the steps of adding anhydrous ethanol and heating twice more to ensure that the boric acid crystals are completely evaporated.

[0023] Sample determination: After the sample is dried, the total α count rate is measured immediately on a low background α and β measuring instrument. The measurement is performed at least three times, each time for 60 minutes. The average count rate of the standard source is recorded, and the counting time is also recorded.

[0024] Detector efficiency: Where: α—activity data Bq measured on the same day from the 241Am standard source; total α activity concentration: Where: A—total α radioactivity concentration in the sample (MBq / m³) 3 );N s —Sample count rate (counts / second, cps); N b — Background count rate (counts / second, cps); E— Detector efficiency (%); V—Volume of sample evaporated in the measuring disk (cm³) 3 ).

[0025] The results indicate that when the measured result is less than 0.1 Bq / L, three decimal places are retained; when the measured result is greater than or equal to 0.1 Bq / L, three significant figures are retained.

[0026] This invention uses an infrared dryer to heat the surface of the liquid sample to prevent liquid splashing; ethanol is added to the sample and heated to cause the boric acid in the sample to evaporate.

Claims

1. A method for total α analysis in boric acid-containing water, characterized in that: The surface of the sample liquid in the stainless steel sample measuring pan is heated with an infrared dryer to evaporate the water. When the water sample begins to crystallize or when the water sample is viscous and about to crystallize, ethanol is added to the sample and heating is continued. Ethanol is added and heated repeatedly when the water sample begins to crystallize or when the water sample is viscous and about to crystallize, until the sample is completely evaporated and no crystals are produced. The α specific activity is then measured. Instrument background determination: Take an unused and uncontaminated sample measuring plate, wash it, rinse it with anhydrous ethanol and dry it, and place it on a low background α and β measuring instrument to continuously measure the total α background count rate of the instrument for more than 2 hours; Determination of the standard source: Place the sample measuring pan in the drying pan of the infrared dryer, accurately add 5 Bq to 10 Bq of standard substance to the center of the sample measuring pan, add 3 mL of anhydrous ethanol to the sample measuring pan, gently shake the drying pan to make the standard source cover the bottom of the sample measuring pan, put the drying pan into the infrared dryer and heat it to evaporate the liquid in the sample measuring pan, take out the drying pan and let it cool naturally for 3 minutes, measure the total α count rate of the standard source measuring pan on a low background α and β measuring instrument, measure at least three times, each time for 60 minutes, record the average value of the standard source count rate, and record the counting time; Preparation of the sample to be tested: Place the sample measuring plate in the drying tray of the infrared dryer, accurately measure 10 mL of sample and slowly add it to the center of the sample measuring plate, gently shake the sample measuring plate to make the sample cover the bottom of the sample measuring plate, put the drying plate into the infrared dryer and heat until crystals begin to precipitate, then remove the drying plate and let it cool naturally for 5 minutes. Add 3 mL of anhydrous ethanol to the sample measuring plate, gently shake the drying plate to dissolve the boric acid in the sample, and then heat it in the infrared dryer for 1 minute. During the heating process, observe carefully. When crystals begin to precipitate in the sample measuring plate or the liquid area shrinks, remove the drying plate and use the residual heat of the drying plate to evaporate the remaining ethanol. Let it cool naturally for 3 minutes, and repeat the step of adding anhydrous ethanol and heating until there are no visible crystals. Then repeat the step of adding anhydrous ethanol and heating twice to ensure that the boric acid crystals are completely evaporated. Total α activity concentration: A—total α radioactivity concentration in the sample; N s —Sample count rate; N b — Background count rate; E— Detector efficiency; V—Volume of sample evaporated in the measuring disk, detector efficiency Activity data measured on the same day from the α-241Am standard source.

2. The method for total α analysis in boric acid-containing water according to claim 1, characterized in that: Sample determination: After the sample is dried, the total α count rate is measured immediately on a low background α and β measuring instrument. The measurement is performed at least three times, each time for 60 minutes. The average count rate of the standard source is recorded, and the counting time is also recorded.

3. The method for total α analysis in boric acid-containing water according to claim 1, characterized in that: The results indicate that when the measured result is less than 0.1 Bq / L, three decimal places are retained; when the measured result is greater than or equal to 0.1 Bq / L, three significant figures are retained.

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