A rapid analysis method of Fe-55 in water

Abstract

The present invention relates to the technical field of radioactivity monitoring, and specifically discloses a method for rapid analysis of Fe-55 in water, comprising the following steps: Step 1: 55 Enrichment of Fe and other Fe isotopes; Step 2: 55 Purification of Fe and other Fe isotopes; Step 3: 55 The method of the present invention can quickly complete the enrichment of Fe-55 in water samples, the purification of Fe-55 and the measurement of the radioactivity of Fe-55.

Description

Technical Field

[0001] The invention belongs to the technical field of radioactive monitoring, and in particular relates to a rapid analysis method of Fe-55 in water. Background Art

[0002] The Technical Specifications for Radioactive Monitoring of Effluents from Nuclear Power Plants (National Nuclear Safety Administration

[2020] No. 44) requires nuclear power plants to carry out radioactive monitoring of liquid effluents from September 1, 2020. 55 However, my country has not yet established a monitoring system for Fe in liquid effluents. 55 Rapid analysis method for Fe 59 The analysis of Fe is in GB / T 15220-1994 Analysis Method of Iron-59 in Water. 59 Fe and 55 Although the analysis methods of Fe have some similarities in sample enrichment and purification steps, there are substantial differences in the measurements, and the differences are significant. 59 The Fe analysis was applied to 55 Analysis of Fe.

[0003] The current international common radioactive iron analysis methods are as follows:

[0004] Table 1 Common international analysis methods for radioactive iron

[0005]

[0006] (1) Hydroxide precipitation combined with anion exchange method

[0007] Many domestic and foreign standards and methods recommend the use of hydroxide precipitation combined with anion exchange to separate and purify iron. Among them, ASTM D4922-2009 uses hydroxide precipitation to enrich elements such as Co, Ni, and Fe, and separates Fe from interfering elements such as Mn, Zr, Nb, and Cs through an anion exchange column.

[0008] The analysis process proposed by ISO / DIS 22515, which is being drafted, is as follows: 1) Adding carriers and counter-carriers (including Fe carriers and counter-carriers of elements such as Sb, Cs, Ca, Cr, Co, and Mn); 2) Ammonia adjustment, precipitation, centrifugation, and desorption; 3) Nitric acid dissolution to separate and purify Fe; 4) Adding Na 2 HPO 4 The solution and ammonia water are then precipitated, desorbed, dissolved with HCl and placed in a counting bottle, and measured on a liquid scintillation spectrometer. The standard recommends two separation and purification methods, including separation using anion exchange resin (such as AG1-X8) and separation using extraction resin (such as TEVA, TRU, UTEVA).

[0009] The above analytical process of hydroxide precipitation combined with anion exchange method has many steps of precipitation, centrifugation and column treatment, and generally requires three days of radiochemical analysis, which is time-consuming.

[0010] (2) TRU resin extraction chromatography

[0011] TRU resin is prepared by coating CMPO extractant and TBP extractant together on an inert support (polyethylene or acrylate). This resin has relative selectivity for Fe.

[0012] Eichrom's standard procedure "Eichrom analytical procedure (FEW01): iron-55 in water" is to evaporate the water sample, dissolve the evaporated residue with 8M nitric acid solution, load the TRU resin column with 8mol / L nitric acid solution system, and desorb with 2mol / L nitric acid solution to obtain a purified iron solution. ISO / DIS 22515, which is being drafted, recommends the separation method of extraction resins (such as TEVA, TRU, and UTEVA). However, for large-volume samples, traditional evaporation operations take a lot of time.

[0013] Therefore, it is urgent to propose a rapid analysis method of Fe-55 in water to solve the above problems. Summary of the invention

[0014] The purpose of the present invention is to provide a method for rapid analysis of Fe-55 in water, which can rapidly and accurately analyze radioactivity.

[0015] The technical solution of the present invention is as follows:

[0016] A method for rapid analysis of Fe-55 in water comprises the following steps:

[0017] Step 1: 55 Enrichment of Fe and other Fe isotopes

[0018] 1.1 Prepare the iron carrier solution, i.e. 56 FeCl 3 Mixed with HCl solution;

[0019] 1.2 Add iron carrier solution to the sample and adjust the pH of the water sample to 10. Under this condition, 55 Fe forms hydroxide colloids with other Fe isotopes;

[0020] 1.3 Heat the above sample to make the colloid condense and precipitate quickly;

[0021] 1.4 Filter, discard the supernatant, and use HNO 3 Dissolve the precipitate in small amounts several times and transfer it into a beaker to obtain 55Enriched solutions of Fe and other Fe isotopes;

[0022] Step 2: 55 Purification of Fe and other Fe isotopes

[0023] 2.1 Prepare purification materials, including TRU resin, the stationary phase of which is a mixture of carbamoyl-methylphosphine derivative and tributyl phosphate;

[0024] 2.2 Add HNO to the TRU resin column 3 Pre-balance, then slowly load the enriched solution onto the column and add HNO 3 Rinse and discard the effluent. The resin that has completed the exchange turns red due to the adsorption of Fe;

[0025] 2.3 Use of HNO 3 Desorbing, collecting the desorbed liquid, heating and evaporating the desorbed liquid to dryness to obtain the purified Fe residue;

[0026] 2.4 Add phosphoric acid to the above residue to dissolve the residue, then transfer it to a volumetric flask and dilute it to the mark with deionized water to obtain 55 Purified solutions of Fe and other Fe isotopes;

[0027] Step 3: 55 Measurement of Fe activity

[0028] pass 55 Fe and 59 Fe standard material calibration to obtain liquid scintillation spectrometer 55 Fe and 59 The detection efficiency and quenching correction curve of Fe. After the purified solution was measured by liquid scintillation spectrometer, the concentration of Fe in the purified solution was calculated by setting different regions of interest. 55 Radioactivity concentration of Fe AC Fe-55 , the calculation formula is as follows:

[0029]

[0030] Where:

[0031] AC Fe-55 — 55 Radioactivity concentration of Fe, Bq / L;

[0032] R n,Fe-55 — 55 Fe Net count rate in the region of interest, counts per second, s -1 ;

[0033] R n,Fe-59 — 59 Fe Net count rate in the region of interest, counts per second, s -1 ;

[0034] XT—From 59 The cross-talk factor obtained from the Fe quenching calibration curve;

[0035] ε Fe-55 — 55 Fe detection efficiency;

[0036] Y—chemical recovery rate;

[0037] V s —purification liquid volume, L;

[0038] DF—decay factor, e -λt ;

[0039] λ— 55 Fe decay constant;

[0040] t—The time difference between the reference date and the middle moment of the experimental counting.

[0041] Step 1.1, preparation of siderophore solution 56 The Fe element content is 5 mg / mL.

[0042] In step 1.2, the pH of the water sample was adjusted to 10 using NaOH solution.

[0043] In step 1.4, filter through a Buchner funnel.

[0044] In step 2.1, the prepared TRU resin particles have a diameter of 100 to 150 μm.

[0045] In step 2.2, the flow rate of the Fe-enriched solution is controlled at 0.5-1 mL / min.

[0046] In step 2.3, HNO 3 The flow rate is 0.5 mL / min.

[0047] In step 2.4, if the dissolution effect is poor, heat on an electric stove to improve the solubility.

[0048] The entire purification process of step 2 takes no more than 1 hour.

[0049] In step 3, take the purified solution into a low potassium glass bottle, add Hisafe III scintillation liquid, and use a liquid scintillation counter to measure the 55 Fe and 59 The net count rate of Fe in the region of interest is calculated as 55 The radioactivity concentration of Fe.

[0050] The remarkable effects of the present invention are:

[0051] (1) The present invention adopts a rapid iron coagulation and precipitation method, which can quickly complete the enrichment of Fe-55 in water samples.

[0052] (2) The method of the present invention uses TRU resin to selectively adsorb iron, which can quickly purify Fe-55 in water samples.

[0053] (3) The method of the present invention adopts a liquid scintillation spectrometer to measure the radioactivity of Fe-55 in water in a conservative way, which can quickly and accurately complete the measurement of the radioactivity of Fe-55 in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Flow chart of the analytical method. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] like Figure 1 A rapid analysis method for Fe-55 in water is shown, comprising the following steps:

[0057] Step 1: 55 Enrichment of Fe and other Fe isotopes

[0058] 1.1 Prepare the iron carrier solution, i.e. 56 FeCl 3 Mixed with HCl solution, 56 The Fe element content is 5 mg / mL, as a non-radioactive nuclide, 56 Fe will not affect the final measurement results;

[0059] 1.2 Add 0.3 mL of iron carrier solution to 500 mL of sample and adjust the pH of the water sample to 10 using 10 mol / L NaOH solution. Under this condition, 55 Fe forms hydroxide colloids with other Fe isotopes;

[0060] 1.3 Use an electric furnace to heat the above sample. As the temperature rises, the movement of the colloid particles intensifies, and the chances of collision between them increase, which weakens the adsorption of ions by the colloid nucleus, weakens the stability of the colloid, and causes the colloid to condense and precipitate quickly;

[0061] 1.4 Filter through a Buchner funnel, discard the supernatant, and use 8 mol / L HNO 3 Dissolve the precipitate in small amounts several times and transfer it into a 50 mL beaker to obtain 55 Enriched solutions of Fe and other Fe isotopes;

[0062] Step 2: 55 Purification of Fe and other Fe isotopes

[0063] 2.1 Prepare purification materials, wherein the TRU resin particle size is 100-150 μm, which is a product of Eichrom Company of the United States; the stationary phase is a mixture of carbamoyl-methylphosphine derivative (CMPO) and tributyl phosphate (TBP);

[0064] 2.2 Add 5 mL 8 mol / L HNO to the TRU resin column 3 Pre-balance for 5 minutes, slowly load the enriched solution onto the column, and add 16 mL 8 mol / L HNO 3 Rinse and discard the effluent. The resin that has completed the exchange turns red due to adsorption of Fe. It should be noted that the flow rate of the Fe-enriched solution should be controlled at 0.5-1 mL / min to ensure that the enriched solution reacts fully with the TRU resin and avoid the red ribbon moving too fast.

[0065] 2.3 Use 5 mL 0.1 mol / L HNO 3 Desorb at a flow rate of 0.5 mL / min, collect the desorbed liquid in a beaker, place the desorbed liquid on an electric furnace, and evaporate to dryness to obtain the purified Fe residue.

[0066] 2.4 Add 4 mL of 1 mol / L phosphoric acid to the above residue to dissolve the residue. If the dissolution effect is poor, heat it on an electric stove to increase the solubility. Then transfer it to a 5 mL volumetric flask and dilute it to the mark with deionized water to obtain 55 Purified solutions of Fe and other Fe isotopes;

[0067] The entire purification process takes no more than 1 hour;

[0068] Step 3: 55 Measurement of Fe activity

[0069] After neutron activation, iron-containing components in nuclear power plant reactors will produce 55 Fe and 59 Fe. 55 The half-life of Fe is 2.7 years, and after orbital electron capture, it emits characteristic X-rays of manganese with an energy of 5.9 keV; 59 The half-life of Fe is 44.5 days. It emits β and γ rays. The energy of β rays is 475keV (51.2%) and 273keV (48.5%), and the energy of γ rays is 1.29MeV (43%) and 1.09MeV (57%). The β ray spectrum is a continuous spectrum. When measuring liquid scintillation, 59 The high energy β rays emitted by Fe will have an impact on the low energy end. 55 Fe should be considered 59 Contribution of Fe;

[0070] pass 55 Fe and 59Fe standard material calibration to obtain liquid scintillation spectrometer 55 Fe and 59 The detection efficiency and quenching correction curve of Fe. After the purified solution was measured by liquid scintillation spectrometer, the concentration of Fe in the purified solution was calculated by setting different regions of interest. 55 Radioactivity concentration of Fe AC Fe-55 , the calculation formula is as follows:

[0071]

[0072] Where:

[0073] AC Fe-55 — 55 Radioactivity concentration of Fe, Bq / L;

[0074] R n,Fe-55 — 55 Fe Net count rate in the region of interest, counts per second, s -1 ;

[0075] R n,Fe-59 — 59 Fe Net count rate in the region of interest, counts per second, s -1 ;

[0076] XT—From 59 The cross-talk factor obtained from the Fe quenching calibration curve;

[0077] ε Fe-55 — 55 Fe detection efficiency;

[0078] Y—chemical recovery rate;

[0079] V s —purification liquid volume, L;

[0080] DF—decay factor, e -λt ;

[0081] λ— 55 Fe decay constant;

[0082] t—The time difference between the reference date and the middle moment of the experimental counting.

[0083] Take 4.0mL of Fe purified solution in a low potassium glass bottle, add 16mL of HisafeⅢ scintillation liquid, and use a liquid scintillation counter to measure the 55 Fe and 59 The net count rate of Fe in the region of interest is calculated as 55 The radioactivity concentration of Fe.

[0084] Example

[0085] The present invention adds excess iron carrier to the sample, adjusts the pH by NaOH, and heats the sample to make the 55 Fe and other Fe isotopes are rapidly precipitated and then dissolved. 55 Rapid enrichment of Fe and other Fe isotopes from water. The enriched solution was separated by TRU resin column to obtain 55 Fe and other Fe isotope purified solutions are used, and finally the purified solution is measured using a liquid scintillation counter, and the sample is calculated 55 Activity of Fe.

[0086] This method was used to conduct an inter-laboratory comparison at Fuqing Nuclear Power Plant, Suzhou Institute of Radiation and Environmental Supervision, and Fujian Province Radiation Environment Supervision Station. The 7ZLD liquid effluent spiked samples of Fuqing Nuclear Power Plant were used. After receiving the comparison samples, the three laboratories conducted 55 Fe analysis was performed using the prepared 7ZLD liquid effluent 55 Fe samples were used as background count rates, and all three laboratories reported 55 The spiked activity concentration of Fe. According to the requirements of "Statistical Methods for Proficiency Testing Using Inter-laboratory Comparison" (GB / T 28043-2019) and "Guidelines for Statistical Processing of Proficiency Testing Results and Proficiency Evaluation" (CNAS-GL002), the En value method and Z ratio method were used for evaluation. The comparison results and evaluation results are shown in Table 2.

[0087] The evaluation results of the En value method showed that there was no significant difference between the analysis results of each laboratory and the specified value at a confidence probability of 95%, confirming the accuracy of the analysis method and the accuracy of the analysis results of the three laboratories; the evaluation results of the Z ratio score method showed that the comparison results of the three laboratories were all satisfactory, confirming the Fe-55 analysis capabilities of Fuqing Nuclear Power and the other two laboratories.

[0088] Table 2 Inter-laboratory comparison and evaluation results of effluent Fe-55 analysis (I) E n Evaluation results of value method

[0089]

[0090] (II) Evaluation results of Z-ratio method

[0091]

[0092] Note: Activity concentration y c is the spiked activity concentration measured by each laboratory.

[0093] The above shows and describes the basic principles, main features and advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claim involved.

[0094] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for rapid analysis of Fe-55 in water, characterized in that it comprises the following steps: Step 1: 55 Enrichment of Fe and other Fe isotopes 1.1 Prepare the iron carrier solution, i.e. 56 FeCl3 and HCl mixed solution; 1.2 Add iron carrier solution to the sample and adjust the pH of the water sample to 10. Under this condition, 55 Fe forms hydroxide colloids with other Fe isotopes; 1.3 Heat the above sample to make the colloid condense and precipitate quickly; 1.4 Filter and discard the supernatant, dissolve the precipitate with HNO3 in small amounts several times and transfer it into a beaker to obtain 55 Enriched solutions of Fe and other Fe isotopes; Step 2: 55 Purification of Fe and other Fe isotopes 2.1 Prepare purification materials, including TRU resin, the stationary phase of which is a mixture of carbamoyl-methylphosphine derivative and tributyl phosphate; 2.2 Add HNO3 to the TRU resin column for pre-equilibration, then slowly load the enriched liquid onto the column and elute with HNO3, discard the effluent, and the resin that has completed the exchange will turn red due to the adsorption of Fe; 2.3 Use HNO3 to desorb, collect the desorbed liquid, and heat and evaporate the desorbed liquid to dryness to obtain the purified Fe residue; 2.4 Add phosphoric acid to the above residue to dissolve the residue, then transfer it to a volumetric flask and dilute it to the mark with deionized water to obtain 55 Purified solutions of Fe and other Fe isotopes; Step 3: 55 Measurement of Fe activity pass 55 Fe and 59 Fe standard material calibration to obtain liquid scintillation spectrometer 55 Fe and 59 The detection efficiency and quenching correction curve of Fe. After the purified solution was measured by liquid scintillation spectrometer, the concentration of Fe in the purified solution was calculated by setting different regions of interest. 55 Fe radioactivity concentration AC Fe-55 , the calculation formula is as follows: Where: AC Fe-55 — 55 Radioactivity concentration of Fe, Bq / L; R n,Fe-55 — 55 Fe Net count rate in the region of interest, counts per second, s -1 ; R n,Fe-59 — 59 Fe Net count rate in the region of interest, counts per second, s -1 ; XT—From 59 The cross-talk factor obtained from the Fe quenching calibration curve; ε Fe-55 — 55 Fe detection efficiency; Y—chemical recovery rate; V s —purification liquid volume, L; DF—decay factor, e -λt ; λ— 55 Fe decay constant; t—the time difference from the reference date to the middle moment of the experimental counting; Take 4.0mL of Fe purified solution in a low potassium glass bottle, add 16mL of HisafeⅢ scintillation liquid, and use a liquid scintillation counter to measure the 55 Fe and 59 The net count rate of Fe in the region of interest is calculated as 55 The radioactivity concentration of Fe.

2. A method for rapid analysis of Fe-55 in water as claimed in claim 1, characterized in that: Step 1.1, preparation of siderophore solution 56 The Fe element content is 5 mg / mL.

3. A method for rapid analysis of Fe-55 in water as claimed in claim 1, characterized in that: In step 1.2, the pH of the water sample was adjusted to 10 using NaOH solution.

4. A method for rapid analysis of Fe-55 in water as claimed in claim 1, characterized in that: In step 1.4, filter through a Buchner funnel.

5. A method for rapid analysis of Fe-55 in water as claimed in claim 1, characterized in that: In step 2.1, the prepared TRU resin particles have a diameter of 100 to 150 μm.

6. A method for rapid analysis of Fe-55 in water as claimed in claim 1, characterized in that: In step 2.2, the flow rate of the Fe-enriched solution is controlled at 0.5-1 mL / min.

7. A method for rapid analysis of Fe-55 in water as claimed in claim 1, characterized in that: In step 2.3, the flow rate of HNO3 during desorption was 0.5 mL / min.

8. A method for rapid analysis of Fe-55 in water as claimed in claim 1, characterized in that: In step 2.4, if the dissolution effect is poor, heat on an electric stove to improve the solubility.

9. A method for rapid analysis of Fe-55 in water as claimed in claim 1, characterized in that: The entire purification process of step 2 takes no more than 1 hour.

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