TWI543939B - Automatic extraction analysis method of trans-uranium element - Google Patents

Description

Automatic extraction analysis method for transuranic elements

The invention relates to an automatic extraction and analysis method for transuranic elements, which uses an automated solid phase extraction system to automatically separate and purify liquid detection materials containing transuranic elements, and then measures the transuranic elements by using an Alpha spectrometer.

Radioactive nucleus is one of the important products of nuclear reaction. In order to ensure the safe operation of nuclear energy facilities and protect the environment from radiation pollution, it is necessary to understand and evaluate the concentration, distribution and influence of radioactive products. Therefore, since the development and application of nuclear energy technology, related radioactivity The analysis and identification of nuclear species has always been an essential technology for the nuclear energy industry.

The manufacture of Trans-Uranium Element in radioactive nucleus can be basically divided into two methods: (1) After the neutron captures the neutron, the atomic sequence is increased by β ^- decay (for example, after the uranium element is irradiated by neutrons) It will produce transuranic elements, neutrons impact uranium-238 to produce 钸-239, uranium-238 is the parent nucleus of 钸-239); (2) accelerate the charged particles to strike the parent nucleus with a charge accelerator (eg mother nucleus 244-244 via The cyclotron accelerates the carbon-13 impact to make 鍩-251). In the nuclear fuel cycle facilities, transuranic radioactive waste, called transuranic waste, is generally produced. The transuranic waste contains roughly various substances such as cement and organic matter. The transuranic element has a half-life of hundreds of thousands of years and is easily soluble in water. It is not easy to be adsorbed, has high mobility in the environment, and has a wide and long-lasting impact on the environment, and most of the transuranic elements release the radiation of the Alpha (α) particles, which are physiologically toxic, if ingested. The body will cause irreversible damage. According to China (Republic of China) low-level radioactive waste final disposal and its facility safety management rules, low-level radioactive waste can be classified into Class A, Class B, Class C and Super according to its radioactive nuclear species concentration. In category C, TRU nucleus (transuranic arsenic nucleus with a half-life of more than 5 years) has been listed as one of the main nuclear species for radiation waste control, and its single long half-life nucleus concentration value is 3.7kBq/g as a classification standard and radioactive waste. According to the packaging of the goods, domestic nuclear power plants, radioactive waste storage sites and the environment require long-term monitoring, so the TRU analysis method is continuously improved to achieve better scores. The results of its necessity.

In the past few decades, China has used radioanalytical methods (RA method) and alpha ray spectrometer to analyze the transuranium waste.

Ultra-uranium waste usually requires pre-treatment before performing radiochemical analysis. The pre-treatment includes: melting, ion exchange and coprecipitation. The common disadvantage of these pretreatments is time-consuming and usually takes several days. It can take several weeks to be used for radiochemical analysis. In addition to affecting the timeliness of analysis, in the high-activity sample analysis, the operator will receive a considerable amount of radiation exposure during the pre-treatment step, resulting in operational safety issues. . In addition, because the transuranic element is easily soluble in water, especially Pu is easy to remain in the container wall, and the previous treatment of the transuranium element analysis usually requires several heating, dilution and container transfer, which will cause the transuranic element to Loss during operation, resulting in low analytical results, even need to be concentrated before being detected by instruments (such as the Alvar spectrometer).

The early column flow washing operation was mainly performed manually by the operator. Because the column volume was limited, and the pipe column liquid was slowly flowed out by gravity alone, the personnel had to stand slowly beside the extraction column, each one The steps must be waited for before the first-stage washing liquid is washed before the next step of the washing liquid is added, so the operator waits for a long time, and the relative exposure dose is increased.

In view of the above problems, the inventors of the present invention have conducted research on how to perform analysis in a shorter time and with a smaller amount of reagents, thereby suppressing cost, and found that by using Automatic Soild phase extraction (ASPE). System automation After purification, the measurement can be carried out by using the Ava spectrometer, and the above object can be achieved, and by controlling by computer program, the operation error can be reduced and the radiation exposure dose of the analyst can be reduced, thereby completing this invention.

The invention relates to an automatic extraction analysis method for transuranic elements, which uses an automated solid phase extraction system to automatically separate and purify liquid detection materials, and then measures the transuranic elements by using an Alpha spectrometer.

The term "transuranic material" as used in the present invention means a radioactive element having an atomic order exceeding U-92, and is exemplified by, for example, Am, Cm, Pu, and the like.

The automatic extraction analysis method of the transuranic element of the invention comprises the following steps: (1) moving the liquid sample to be tested and evaporating to a beaker, and adding 1M~3M (preferably 2M) nitric acid and 0.1M~0.5M thereto. (preferably 0.3 M) ascorbic acid is made into a volume to obtain a mixture. This step is to reduce the various valences of Pu to asPu ⁺³ with various valences of Pu present in the sample, which will help the TRU resin to adsorb Pu and discharge other interferents; (2) about 5~ 15dpm/g (preferably 10dpm/g) Am-243 and Pu-242 tracer agent are added to the mixture obtained in the step (1), and the mixture is injected into the TRU resin of the automated solid phase extraction system. In the column, the tracer in this step selects the isotope of the element to be analyzed. The isotope is similar in chemical properties to the element to be analyzed, so the sample to be tested can be pushed back by measuring the recovered tracer recovery rate. The content of the transuranic element in the medium; (3) sequential washing with the following solvent: (3a) 1M ~ 3M HNO ₃ solution containing 0.1M ~ 0.5M ascorbic acid, flow washing TRU resin; (3b 1M~3M (preferably 2M) HNO ₃ solution containing 0.05M~0.3M (preferably 0.1M NaNO ₂ ) to convert Pu ⁺³ to Pu ⁺⁴ to avoid the use of HCl flow in the next step The Pu will be washed out at the same time, so that Pu can still be adsorbed in the TRU resin; (3c) 3M~5M (better 4M) HCl, and the tracer Am-243 is eluted, in the sample to be tested in this step. When Cm is contained, Cm will be washed out with Am, and Cm can be analyzed at the same time; (3d) Pu is eluted with 0.05M~0.2M (preferably 0.1M) NH ₄ HC ₂ O ₄ aqueous solution. (4) then adding the Am and/or Cm-containing solution obtained in the step (3c) and the Pu-containing solution obtained in the step (3d) to each of the test pieces (which may be stainless steel 316 or 304) The plating device of the round test piece (model: GPS-3030DD, INSTEK, China) is plated for 0.5 to 1.0 hour (preferably 0.8A) for 1 to 3 hours (2 hours is preferred) to obtain the plated piece. The detailed plating conditions are as follows: (4a) the Am and/or (Cm)-containing solvent solution obtained in the above steps (3c) and (3d) and the Pu-containing solution are evaporated to dryness, and then added thereto. After 0.5~2M (preferably 1M) H ₂ SO ₄ and evaporated to dryness, a few drops of the indicator thymol blue were added to obtain an electrodeposition solution. (4b) The above electrodeposition solution was adjusted to have a pH of 2 to 3 with concentrated NH ₄ OH, at which time the solution was orange. (4c) The stainless steel sheet was first washed with alcohol and charged into an electrodeposition tank, with a platinum wire as an anode and an electrodeposited sheet as a cathode, and fixedly assembled after adjusting the distance therebetween. (4d) Pour the electrodeposition solution obtained in the step (4c) into the electrodeposition bath, electrodeposite at 0.8 A for 120 minutes, and add a few drops (3 drops of preferably) 30% NH ₄ OH to adjust the electrodeposition before the end of electrodeposition. The pH value of the liquid helps the test nucleus to adhere to the electroplated sheet, and waits for 1 minute to remove the platinum anode; and (5) the electroplated sheet obtained in the step (4) is measured by an argon spectrometer, and the measurement is performed. After completion, open the spectrum according to the energy circle selection peak (additional tracer Am-243 energy is 5.27MeV, Am-241 energy is 5.48MeV, Pu-238 energy is 5.49MeV, Pu-239+Pu-240 energy is 5.15/ 5.168MeV, and the added tracer Pu-242 energy is 4.9MeV), record the count value of each nuclear species and tracer and the efficiency of the measurement chamber, calculate the recovery rate and the activity of each nucleus, and find the transuranic activity in the sample. degree.

In the automatic extraction analysis method of the present invention, when the sample to be tested is in a solid state, before the step (1), the following steps are further carried out: adding concentrated nitric acid to the solid sample to be tested and Hydrochloric acid was placed in a microwave digestion apparatus (Microwave Digestion System, MARS 5, CEM, USA) for digestion to obtain a liquid sample to be tested for the aforementioned step (1).

The automatic extraction analysis method of the present invention, wherein before the sample is injected into the TRU resin column of the automated solid phase extraction system in the step (2), the following dissolution is performed: 0.1M to 0.5M (preferably 0.3M) ascorbic acid 1M ~ 3M (preferably 2M) HNO ₃ solution, the elution TRU resin, the resin may TRU to interfere with the exhaust.

In the automatic extraction analysis method of the present invention, the sample to be tested may be a trans-uranium waste such as a dry uranium waste, a waste resin, a sediment waste, a filter paper or a damaged soil.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing an embodiment of the automatic extraction analysis method of the present invention.

The invention is further illustrated by the following examples, which are intended to be illustrative only and not to limit the scope of the invention, and the scope of the invention is limited by the scope of the claims.

[Example 1]

The automatic extraction analysis method of the transuranic element of the present invention is carried out in the following procedure. In this embodiment, the sample to be tested is taken as a solid sample as an example.

1. Prepare the liquid test substance: cement: 71.54%, NaCl: 12.61%, Ba(OH) ₂ : 6.00%, Na ₂ SO ₄ : 4.50%, NaOH: 3.15%, NaNO ₃ : 1.18%, Na ₂ CO ₃ : 0.62%, Na ₃ PO ₄ : 0.26%, NaHCO ₃ : 0.14% was sufficiently mixed with water to prepare a cement block as a solid sample. Then, 0.25 g of the solid sample was weighed and placed in a digestion bottle, and 9 ml of concentrated nitric acid and 4 ml of hydrochloric acid were added. In order to prevent the gas from being produced by the acidic solution, the digested bottle was allowed to stand for one minute without being covered, and then the digestive bottle was covered. After standing for 20 minutes, it was pre-nitrated and placed in a microwave digestion unit. In this experiment, two samples of one sample were digested at one time to illustrate the parameters of the digestion unit: the highest power of the digestion unit was 300 W, and the operating power was 56% of the highest power. The temperature was raised for 5.5 minutes, the temperature was raised from room temperature to a temperature of 180 ° C, and maintained at this temperature for 11.5 minutes. After obtaining the digestive juice, the digested juice was transferred to a beaker and steamed to about dryness.

2. The dried solution containing ascorbic acid was 0.3M to 2M nitric acid until the capacity of 15mL, reducing the number of samples to be tested in a variety of monovalent Pu to Pu ^+3, to obtain a mixture. If there are clearly visible impurities or suspensions in the resulting mixture, it is necessary to use a filter paper, for example, filtration using Whatman No. 42, and then add Am-243 and Pu-242, respectively, at about 10 dpm/g as a tracer.

3. Using 2ml of TRU resin (particle size 100~150μm) produced by Eichrom Technology, put it into the filling column in the Automatic Solid Phase Extraction system (SPE, Biotage RapidTrace ⁺ , Sweden), first use 20mL The 2M nitric acid containing 0.3 M L-ascorbic acid was subjected to a flow wash at a flow rate of 3 ml/min to discharge possible interferences in the TRU resin.

4. Periodically elute sequentially using the following solvent: (a) 20 mL of 2 M nitric acid containing 0.3 M L-ascorbic acid was flow-washed at a flow rate of 3 ml/min; (b) 5 mL The 2M HNO ₃ solution containing 0.1 M NaNO ₂ was subjected to flow washing at a flow rate of 3 ml/min, and Pu ^{+3 was} converted to Pu ⁺⁴ ; (c) 20 mL of 4 M HCl was dissolved at a flow rate of 3 ml/min. Tracer Am-243; and (d) 0.1M NH ₄ HC ₂ O ₄ aqueous solution at a flow rate of 10 ml / min to wash the column to dissolve Pu;

5. Next, the Pu-containing solution obtained in the step 4. was subjected to electroplating on a stainless steel 316 round test piece by electroplating for 2 hours using a plating apparatus (Model: GPS-3030DD, INSTEK, China) to obtain an electroplated sheet. The detailed plating conditions are as follows: 1M H ₂ SO ₄ and evaporation of the near dry liquid are respectively added to the Am-containing solution obtained in the above step (c) and the Pu-containing solution obtained in the step (d). After re-dissolving, a few drops of the indicator thymol blue were added to obtain an electrodeposition solution. (4b) Adjust the pH of each electrodeposition solution to 2 to 3 with concentrated NH ₄ OH, at which time the solution is orange. (4c) The stainless steel sheet was first washed with alcohol and charged into an electrodeposition tank, with a platinum wire as an anode and an electrodeposited sheet as a cathode, and fixedly assembled after adjusting the distance therebetween. (4d) Pour each electrodeposition liquid obtained in the step (4c) into each electrodeposition bath, electrodeposite at 0.8 A for 2 hours, add 3 drops of 30% NH ₄ OH before the end of electrodeposition, and wait for 1 minute to remove Platinum anode.

6. The plated piece obtained in step 5. is measured by a multi-channel Ava spectrometer. After the measurement is completed, the spectrum is selected according to the energy circle (the energy of the tracer Am-243 added is 5.27 MeV, Am-241). The energy is 5.48 MeV, the energy of Pu-238 is 5.49 MeV, the energy of Pu-239+Pu-240 is 5.15/5.168 MeV, and the energy of the added tracer Pu-242 is 4.9 MeV), and the counts of each nuclear species and tracer are recorded separately. The numerical value and the efficiency of the measurement chamber were calculated, and the recovery rate and the activity of each nucleus were calculated to determine the activity of the transuranic element in the sample. As a result, the recovery of Am-243 was 67 ± 10%, and the recovery of Pu-242 was 42 ± 10%.

[Embodiment 2]

In this example, except for the liquid sample to be tested in the first step of the embodiment 1, 1 ml of pure water was added to 10 mL of 2 M nitric acid of 0.3 M ascorbic acid, and then 1 mL of Am-243 and 1 mL of Pu-242 were added (the activity was about The liquid mixture was subjected to an experimental test as a sample to be tested at about 10 dpm, and the same operation as in Example 1 was carried out to obtain an Am-243 recovery rate of 85 ± 5% and a Pu-242 system of 65 ± 5%.

The above steps 3 and 4 of the present invention are all carried out in an automated solid phase extraction system, and each elution parameter such as the elution flow rate can be controlled by a computer, thereby reducing the dose of radiation received by the operator.

The automatic extraction analysis method of the transuranic element of the invention is automated separation and purification by an automated solid phase extraction system, and then measured by an Ava spectrometer, and is a fully automatic extraction and purification analysis method for analyzing the transuranic element. The invention can greatly shorten the operation time, reduce the use of reagents, and effectively reduce the cost, and automatically controls the extraction and purification operation through the computer program, can reduce the operation error of the personnel, and can reduce the radiation exposure dose received by the analyst. The automated solid phase extraction system of the invention is a closed system, and the transuranic element is not easy to escape during the analysis, and the original transuranium can be preserved compared with the conventional method. Elements to ensure the correctness of the analysis results. Based on the above advantages, the present invention is well suited for use in nuclear power plants, nuclear waste storage sites, and environmental monitoring and utilization.

Claims (5)

An automatic extraction analysis method for transuranic elements, comprising the following steps: (1) moving a liquid sample to be tested and evaporating to a beaker, and adding 1 M to 3 M nitric acid and 0.1 M to 0.5 M ascorbic acid to make a certain volume , obtaining a mixture, (2) adding 5 to 15 dpm/g of Am-243 and Pu-242 tracer agent to the mixture obtained in the step (1), and injecting the mixture into the automated solid phase extraction system. (Automatic Soild phase extraction, ASPE) in the TRU resin column, (3) sequential washing with the following solvent: (a) 1M~3M HNO ₃ solution containing 0.1M~0.5M ascorbic acid, Flow-washing TRU resin; (b) 1M~3M HNO ₃ solution containing 0.05M~0.3M to convert Pu ⁺³ to P ⁺⁴ ; (c) 3M~5M HCl, eluting tracer Am-243 (d) eluting Pu with 0.05 M to 0.2 M aqueous solution of NH ₄ HC ₂ O ₄ ; (4) subsequently preparing the Am-containing solution obtained in step (3) (c) and step 3 (d) The obtained Pu-containing solution is separately electroplated on a test piece by electroplating for 0.5 to 1.0 A for 1 to 3 hours to obtain each plated sheet; and (5) each of the plated sheets obtained in the step (4) is The Alvar spectrometer performs the measurement and the measurement is completed. , Circle pattern corresponding to each element in the energy peaks are recorded for each tracer nuclide and the count value of the efficiency and the measurement chamber, and various radionuclides activity recovery was calculated to determine the activity of the sample super transuranium elements. For the automatic extraction analysis method of the transuranic element of claim 1, wherein when the sample to be tested is solid, before the step (1), the following steps are further carried out: adding concentrated nitric acid and hydrochloric acid to the solid sample to be tested and placing Digestion is carried out in a microwave digestion apparatus to obtain a liquid sample to be tested for carrying out the aforementioned step (1). An automatic extraction analysis method for the transuranic element of claim 1, wherein the energy peak corresponding to each element in the map: the energy of the tracer Am-243 added is 5.27 MeV, Am- The energy of 241 is 5.48 MeV, the energy of Pu-238 is 5.49 MeV, the energy of Pu-239+Pu-240 is 5.15/5.168 MeV, and the energy of the added tracer Pu-242 is 4.9 MeV. An automatic extraction analysis method for the transuranic element of claim 1, wherein in the step (3), if the sample to be tested contains the element Cm, the Cm is eluted with the Am after the dissolution in the step (3c). , while the element Cm can be quantified simultaneously. An automatic extraction analysis method for the transuranic element of claim 1, wherein before the sample is injected into the TRU resin column of the automated solid phase extraction system in step (2), the following dissolution is performed: 0.1M to 0.5M ascorbic acid is contained. The 1M~3M HNO ₃ solution is used to rinse the TRU resin to remove possible interferences from the TRU resin.