Radiochemical Procedure Research Articles

A radiochemistry laboratory exercise: determination of uranium in tap water by solvent extraction and liquid scintillation counting

Environmental radiochemistry is a key pillar of the education of nuclear engineering students and young professionals. Teaching the fundamentals of this multidisciplinary field is best performed also through well-designed hands-on experiments. A simple and fast radiochemical procedure has been developed to determine uranium in tap water by liquid scintillation counting. The proposed method provides reliable and repeatable results, with accuracy and precision within 5%. It can be proficiently executed by undergraduate students, who have appreciated the engagement and got acquainted with standard analysis protocols, from sample collection and manipulation to radiometric measure and data analysis.

Alpha-induced production and robust radiochemical separation of 43Sc as an emerging radiometal for formulation of PET radiopharmaceuticals

Scandium-43 is an emerging PET radiometal that was produced by α-particle bombardment on natural CaCO3 target via natCa (α,p) 43Sc and natCa (α,n) 43Ti→43Sc reactions using K-130 cyclotron at VECC. A robust radiochemical procedure based on selective precipitation of 43Sc as Sc(OH)3 was developed for separation of the radioisotope from the irradiated target. The overall yield of the separation process was >85% and it was obtained in a form suitable for preparation of target specific radiopharmaceuticals for PET imaging of cancer.

Atmospheric deposition of 10Be in Altzomoni rainfall

The optimization of preparation techniques for 10Be in rainfall samples and the approaches applied to improve the measurement of this radionuclide with the accelerator mass spectrometry (AMS) system were carried out at LEMA-UNAM. A radiochemical procedure has been realized to measure 10Be in smaller samples than those reported in similar studies, reducing the sample volume from 2 L to 250 mL. The 10Be concentrations in the dissolved and particulate fraction of rain from the high-altitude rural site Altzomoni (Mexico) during 2017–2018 were determined for the first time at LEMA. The results show that the presence of particulate material is four orders of magnitude greater than the content of 10Be in the rainfall from Altzomoni. This work shows a mean concentration of (1.9 ± 0.2) × 104 and (3.3 ± 0.6) × 108 atoms per gram of rainfall in dissolved and particulate fractions.

129I in sediment cores from the Celtic Sea by AMS through a microwave digestion process

Radiochemical methods before measurement are indispensable to determine Iodine-129 by Accelerator Mass Spectrometry (AMS) in environmental samples. In particular, in sediments, iodine is associated with both inorganic and organic matter, and it presents in several chemical forms. Therefore, the radiochemical procedure must be designed to extract all the different iodine species from the matrix, whilst being as robust and time effective as possible. In this work, different microwave digestion methods, together with the processing of the iodine species to be measured by AMS, were tested and their performances are presented here. Two sediment cores, one with muddy sediment (core A) and one with permeable sandy sediment (core I), collected in the Celtic Sea, were used and the results were evaluated to determine an optimized iodine extraction. The method consisted of a microwave digestion with concentrated nitric acid followed by a double liquid–liquid extraction and the final precipitation of silver iodide (AgI), required to measure iodine by AMS. Back extraction of iodine in a reducing solution during purification was carried out with hydrazine (NH2-NH2). Subsequent additional steps were added to optimize all iodine species extraction. First, hydrochloric hydroxylamine (NH2OH·HCl) and sodium bisulfite (Na2S2O5) were used to homogenize all iodine species before extraction through a redox process. Second, sodium hypochlorite (NaOCl) was added to remove any final organic matter after digestion. The final method incorporated sodium hydroxide (NaOH) combined with NaOCl to facilitate reduction of iodine in solution and enhance the NaOCl effect. The different methods were validated against an internal standard and the last method was chosen, as it showed the most reproducible and accurate results. As practical application, Iodine-129 concentration from both cores were compared, showing concentrations between 0.19 × 1012 at/kg and 7.16 × 1012 at/kg for core A and between 0.28 × 1012 at/kg and 2.40 × 1012 at/kg for core I. Despite the 129I diffusion detected in the deeper layers, depth profiles accurately reproduced Sellafield discharges, which is the nuclear fuel reprocessing plant closest to the cores.

Status report on AMS measurements of plutonium isotopes using the 1MV Tandetron Accelerator at IFIN-HH

Accelerator Mass Spectrometry is the most sensitive measurement method that allows us to determine 239, 240, and 244Pu radioisotopes in environmental samples with extremely low isotopic concentrations. By measuring plutonium isotopes, we focus our research activity on two main directions, monitoring of environmental nuclear pollution and nuclear astrophysics.This report gives an overview of the progress that was made in the determination of plutonium isotopes at IFIN-HH, and it starts with the studies performed for the transport and measurement of actinides using the 1MV Tandetron Accelerator. The 238U and 232Th isotopes were used as pilot beams for the determination of ion transport parameters, after which the isotopic ratios 239Pu/242Pu, 240Pu/242Pu, and 244Pu/242Pu were measured using the new Plutonium Standard ColPuS. The results obtained for the isotopic ratios agree with the consensus values of the standard. In addition, we developed radiochemical procedures for thorium, plutonium, and uranium separation, the chemical recoveries of uranium and thorium using UTEVA and TEVA resins are presented, where we used an Agilent ICP-MS system (Inductively Coupled Plasma Mass Spectrometry). The radiochemical separation is important mainly for obtaining target materials that can provide microscopic pilot beams as U and/or Th. Finally, a short overview is provided of the molecular interference challenges that are encountered when measuring plutonium isotopes.

Radiochemical Procedure for Measurement Specific Activities of Uranium Isotopes in Asphaltite Bioleaching Liquor by Alpha-Particle Spectrometry

An analytical procedure for the alpha-source preparation is investigated in the study to determine uranium radioisotopes specific activities in the bioleaching liquor leach from asphaltite samples taken from the Silopi region in Türkiye. The purpose is to develop a new radiochemical method that can provide the alpha-particle spectrometry requirements. The proposed analytical procedure includes sample preparation, radiochemical purification of uranium from bioleaching liquor, alpha-source preparation on a substrate and alpha-particle spectrometric analysis of isolated uranium. The method is valid for availability using the z-test, relative bias, and relative uncertainty outlier tests. The results show that the proposed analytical procedure is successfully implemented for measuring the activity concentration of uranium with high accuracy and precision in the bioleaching liquor.

Evaluation of performance and precision of a radiochemical procedure for quantification of low concentrations of 234U and 238U in water samples

ABSTRACT Uranium isotopes 238U, 234U, and 235U are alpha-particle emitters and can be directly measured by alpha spectrometry. To evaluate the accuracy of the determination of low concentration of U isotopes in water samples, six spiked water samples were analysed by extraction chromatography using uranium selective resin. The separated uranium isotopes were electrodeplated on a disc of stainless steel and were measured by an alpha spectrometer for the determination of radiochemical yield using 232U isotopic tracer. Three certified IAEA reference water samples (IAEA-Cu-2010-03, IAEA-420 and IAEA-421) have been analysed for method validation. The measurement uncertainty sources were identified, and the combined standard uncertainty of the measurement has been determined. Although the activity of uranium isotopes in the certified reference samples was very low, the obtained results were reliable and were within the certified range with 95% confidence level. The characteristic limits (the decision threshold and detection limit) were calculated. The combined uncertainty of the results was mostly attributed to the count rates in the region of interest of the analyte and the tracer in the blank as well as in the sample spectra. Based on the results of the acceptance criteria including Z-score, u-test, trueness and precision, the used radiochemical procedure was found accurate and precise as well.

Measurement of 90Sr in Marine Biological Samples.

Strontium-90 (90Sr) is one of the most hazardous radionuclides, and it contributes to radiation exposure by ingestion. The routine determination of 90Sr in marine biological samples is highly desirable given the development of the nuclear power industry. A fast, simple, and low-detection-limit method was developed for the measurement of 90Sr in marine biological samples based on determining 90Y by means of coprecipitation and solvent extraction with bis-2-ethylhexyl-phosphoric acid (HDEHP) in n-heptane. The interfering 210Bi is removed using Bi2S3 precipitation. The separation and purification of eight samples per day can be accomplished through this method. The detection limit of 90Sr for this method is 0.10 Bq/kg (ash weight). The radiochemical procedure was validated by fitting the decay curve of the sample source and by the determination of 90Sr standards.

Method Validation and Measurement Uncertainty Evaluation of the Radiochemical Procedure for the Determination of 231Pa in Siliceous Cake by Gamma Spectrometry

An in-house radiochemical procedure for the separation of 231Pa from siliceous cake - a waste stream of monazite processing plant, followed by its determination using gamma ray spectrometry, has been developed in our laboratory. Evaluation of reliability of analytical results of the radiochemical procedure is important for validating the fitness of purpose of an analytical method. The present paper describes the statistical evaluation of the analytical results obtained, by estimating the overall uncertainty in the measurement process. The bottom-up approach, also called as ISO approach (ISO/IEC guide 98-3:2008), was adopted to evaluate the overall uncertainty in which the individual sources were identified, evaluated and propagated. The major contribution to the combined uncertainty in measurement of 231Pa was from efficiency calibration. Besides this, counting statistics in the sample and chemical yield of the process incorporated significant contribution to combined uncertainty. The precision of the results obtained was found to be acceptable, as ascertained by the Horwitz Ratio, for the performance of a single laboratory.

A comparative study of alternative methods for 210Pb determination in environmental samples

The accurate determination of the levels of 210Pb in environmental samples (e.g. atmospheric aerosols, waters, soils, biota, etc.) is essential due to its multiple applications in geochronology, radiation protection, groundwaters flows, air masses movement, etc. For this purpose, it has been developed a novel and thorough study of three alternative radiometric measuring methods of 210Pb activity concentrations in several types of samples. The three selected methods were low-level gamma spectrometry (210Pb), alpha-particle spectrometry (via 210Po), and Cherenkov counting (via 210Bi). This study has been performed in terms of precision, linearity and proportionality as well as spent time, type of matrix, and showing the most appropriate method of measure in each case. Several kinds of samples were analyzed such as atmospheric filters, soils, sediments and phosphogypsum (PG) matrices. These samples contain different 210Pb activity concentrations and were measured by the three techniques carrying out radiochemical procedures when necessary. There were not significant differences in the results obtained for the samples analyzed by the three methods. The major precision was obtained by using alpha-particle spectrometry, but this method is more expensive and time consuming.

Radiolabeling of Human Serum Albumin With Terbium-161 Using Mild Conditions and Evaluation of in vivo Stability.

Targeted radionuclide therapy (TRNT) is a promising approach for cancer therapy. Terbium has four medically interesting isotopes (149Tb, 152Tb, 155Tb and 161Tb) which span the entire radiopharmaceutical space (TRNT, PET and SPECT imaging). Since the same element is used, accessing the various diagnostic or therapeutic properties without changing radiochemical procedures and pharmacokinetic properties is advantageous. The use of (heat-sensitive) biomolecules as vector molecule with high affinity and selectivity for a certain molecular target is promising. However, mild radiolabeling conditions are required to prevent thermal degradation of the biomolecule. Herein, we report the evaluation of potential bifunctional chelators for Tb-labeling of heat-sensitive biomolecules using human serum albumin (HSA) to assess the in vivo stability of the constructs. p-SCN-Bn-CHX-A”-DTPA, p-SCN-Bn-DOTA, p-NCS-Bz-DOTA-GA and p-SCN-3p-C-NETA were conjugated to HSA via a lysine coupling method. All HSA-constructs were labeled with [161Tb]TbCl3 at 40°C with radiochemical yields higher than 98%. The radiolabeled constructs were stable in human serum up to 24 h at 37°C. 161Tb-HSA-constructs were injected in mice to evaluate their in vivo stability. Increasing bone accumulation as a function of time was observed for [161Tb]TbCl3 and [161Tb]Tb-DTPA-CHX-A”-Bn-HSA, while negligible bone uptake was observed with the DOTA, DOTA-GA and NETA variants over a 7-day period. The results indicate that the p-SCN-Bn-DOTA, p-NCS-Bz-DOTA-GA and p-SCN-3p-C-NETA are suitable bifunctional ligands for Tb-based radiopharmaceuticals, allowing for high yield radiolabeling in mild conditions.

I-129 DETERMINATION IN EVAPORATOR CONCENTRATE USING OXIDATIVE EXTRACTION AND CHROMATOGRAPHIC RESIN

Determination of long-lived radionuclides is very important for study of the radioactive waste final deposition. In this work will be studied 129I radionuclide which present 1.6 x 107 years half-life, β-particle-emitting (Emax = 194 keV) and X-ray-emitting (E = 29.78 keV). It’s produced primarily from fission of 235U and 239Pu and for fission induced by thermal neutrons. For this reason, radiochemical procedures for 129I determination in evaporator concentrate wastes from nuclear power plants were carried out. The first procedure was based on oxidative extraction and alkaline absorption and the second one, was based on selective extraction using a chromatographic resin in order to separate iodine from its interferents. After the separation steps, the iodine activity was measured by ultra low gamma spectrometry technique. To set up the yield recovery for 129I, a tracer solution of 129I was used in order to follow the behavior of iodine during the separation steps. The yield recovery for iodine was around 75-80% for the first procedure and 80-85% for the second. The two procedures used mutually, ensure a greater efficiency in the separation of iodine from their respective interferents.

Simultaneous determination of 210Pb and 210Po in seafood samples using liquid scintillation counting

The measurement of 210Pb and 210Po in seafood samples has attracted tremendous interest because of their radiotoxicity. In this study, a fast and cost-efficient method for the simultaneous determination of 210Pb and 210Po in seafood samples by ultralow-level liquid scintillation counting after separation on a Sr•spec column was developed. The recoveries of 210Pb and 210Po were ~70% and ~85%, respectively. The minimum detectable activity of the proposed method for 210Pb and 210Po was 3.85 Bq/kg and 1.50 Bq/kg, respectively, which is suitable for the determination of 210Pb and 210Po in seafood samples. The radiochemical procedure was validated by measuring 210Pb and 210Po activity concentrations in IAEA-certified reference materials and successfully applied to shrimp and clam samples.

Radiochemical technique as a tool for determination and characterisation of El Sela ore grade uranium deposits

ABSTRACT The present study is an application of a radiochemical procedure for the determination of 238U, 235U and 234U as well as uranium isotopic ratios in El Sela ore grade samples that located at the Southeastern Desert of Egypt. This procedure is consisting of several steps include sample preparation, chemical separation and source preparation followed by counting using alpha-particle spectrometry technique. Radiochemical determination of various uranium isotopes contents indicated that El Sela uranium deposits are considered as a recent deposit where there was a large difference between radiochemically and radiometrically determined uranium. The measured 234U/238U activity ratios for most samples were approximately unity, indicating that secular radioactive equilibrium was established between 238U and 234U in the El Sela mineralised rocks. On the other hand, 238U and 234U might be equally leached due to the effect of rock-water interactions during the pluvial time by the action of surficial or underground water. The 238U/235U activity ratios of the studied mineralised granites were significantly shifted from the natural ratio 21.7, indicating that the redox conditions and alteration processes played an important role in the fractionation of 238U from 235U. The values of 234U/235U ratios in the studied granites varied between 23.08 and 34.70 in different samples, suggesting 235U migration out due to the prevailing conditions.

Determination of Plutonium and Uranium Radionuclides in Glacier Ice Samples by MC-ICP-MS

A radiochemical procedure for the determination of plutonium (Pu) and uranium (U) radionuclides in ice samples by multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) is presented. Pu and U radionuclides are preconcentrated by coprecipitation and then separated by extraction chromatography. The purified Pu and U fractions are analyzed by MC-ICP-MS. Detection limits of 2 × 10 -3 and 3 × 10-6 mBq kg-1 were achieved for 239Pu and 236U, respectively. Surface ice samples collected from the Gauli glacier (Switzerland) were analyzed by this method. The surface of the Gauli Glacier retains historical records of 239Pu, 240Pu and 236U from the nuclear weapon testing (NWT) period. Pu and U radionuclides were found to be consistent in terms of pattern, showing two peaks possibly related to the two main periods of the NWTs (1954-1958 and 1961-1963). ³H measurements, also released by the NWT, further confirmed the Pu and U results. The 240Pu/239Pu ratio ranged from 0.14 to 0.25, and 236U/ 239Pu ranged from 0.14 to 0.81. The Pu atom ratios ranged within the limits of global fallout in the most intensive period of NWT (1952 to 1962).

Spectroscopy of Radiostrontium in Fuel Materials Retrieved from the Chernobyl Nuclear Power Plant.

Some basic methods of measuring radiostrontium activity by spectroscopic methods are considered in this study. These methods of assessing beta spectra and the characteristic radiation that accompanies the breakdown of radiostrontium are described. The sensitivity of these methods based on the assessments of beta spectra both after radiochemical procedures and without radiochemistry is presented. The objective of this paper is to review the spectroscopic procedures that have been developed and used to determine radiostrontium in various matrices; they are focused on modern methods. Samples of fuel particles of different origins, obtained from the Chernobyl Nuclear Power Plant Unit 4, were analyzed using the methods presented in this study.

Determination of uranium content in ammonium uranyl carbonate (AUC) and triuranium octoxide (U3O8)

This paper presents a fast and reproducible method for determination of uranium content in ammonium uranyl carbonate (AUC) and U3O8 obtained from it. The effects of high activity and specific chemical composition of the samples were minimized by adapting the radiochemical procedures for analysis of a small amount of samples. Measurements were made by alpha-spectrometry and ICP-MS. The results show that the applied procedures are stable with significant yield and can be successfully used for analysis of AUC and U3O8. Comparison of the data obtained by alpha-spectrometry and by ICP-MS shows that the measured values are in good coincidence.

Development of a radiochemical sequential procedure for the quantification of Th- and U-decay series elements in mining residues

This article discusses a new complementary method for gamma spectrometry for the assessment of natural radioactivity in mining residues. The proposed analytical strategy allows us to determine if secular equilibrium is achieved in the sample with an HF-free dissolution process and a robust sequential radiochemical procedure for U, Th, Ra, Pb and Po isotopes. Various mineralization strategies were investigated on certified mining residues to completely dissolve both refractory (Th, U) and volatile (Po) species, either via open vessel or microwave-assisted acid digestion with nitric and hydrochloric acids followed by an alkaline fusion on the undissolved solids. Then 5 naturally occurring radioelements (Th, U, Ra, Pb and Po) present in the digested sample were separated with 3 stacked selective resins (TRU, Sr resin and HRa), from which they were individually eluted. The single loading step, composed of HCl/HNO3, was optimized to ensure selective retention onto the resins without the need to alter the loading matrix by varying the pH or adding salt, acid, or solvents. The 5 eluted solutions containing individual fractions of the desired elements could then be analyzed by either ICP-MS/MS or alpha spectrometry. More than 92% of each analyte were recovered in certified reference materials with the proposed procedure (dissolution and extraction).

Validation of a radiochemical method for the determination of 55Fe and 63Ni in water and steel samples from decommissioning activities

We present the validation of a radiochemical procedure for the determination of 55Fe and 63Ni in water and steel samples from nuclear decommissioning activities. The in-house validation was an essential requirement of the accreditation to ISO/IEC 17025. A combination of co-precipitation, anion chromatography and extraction chromatography steps was used for separating and purifying both radionuclides. The activities were measured by liquid scintillation counting. Due to the lack of reference materials, the method was validated by analysing simulated samples and by the standard addition technique. The parameters precision/accuracy, repeatability/linearity, selectivity/specificity, decision threshold, detection limit and uncertainty of the method were evaluated.

Radiochemical separation of no-carrier-added 186Re from proton irradiated tungsten target

Rhenium-186 [t½ = 3.7 d, 1.07 MeV β−-particles, 137 keV γ-ray] is an emerging radioisotope which holds tremendous potential in preparation of theranostic radiopharmaceuticals. This radioisotope was produced in a no-carrier-added form by irradiation of enriched 186W target via 186W(p, n) 186Re reaction in a pelletron. A facile radiochemical separation procedure based on selective solvent extraction in methylethyl ketone medium followed by column chromatography using mesoporous alumina sorbent has been developed to obtain 186Re in a form suitable for radiopharmaceutical preparation. This approach is expected to promote widespread utilization of this radioisotope for the benefit of cancer patients.