Application of ICP-QMS for the determination of ultratrace-levels of <Superscript>226</Superscript>Ra in geothermal water and sediment samples

A rapid, accurate and less labor intensive approach to determining ²²⁶Ra in environmental samples was examined; this utilized quadrupole-based inductively coupled plasma mass spectrometry (ICP-QMS). The procedure used chemical separation by ion exchange chromatography to remove most of the matrices after coprecipitation with BaSO₄. The average chemical recovery of the NIST SRM preparation method ranged from 60.5 to 85.9% using ¹³³Ba as internal tracer by gamma counting. This technique was capable of completing a ²²⁶Ra measurement within 3 min. It did not require an in-growth period to allow radon and its progeny to achieve secular equilibrium with the parent ²²⁶Ra as is needed for liquid scintillation analyzer (LSA). The method detection limits for the determination of ²²⁶Ra in geothermal water and sediment samples were 0.02 mBq L⁻¹ (0.558 fg L⁻¹) and 0.10 Bq kg⁻¹ (2.79 fg g⁻¹), respectively. The results obtained with various natural samples and the suitability of the method when applied to various environmental matrices such as geothermal water and sediment are discussed. When ICP-QMS was compared to double-focusing magnetic sector field inductively coupled plasma mass spectrometry (ICP-SFMS), good agreement was obtained with a correlation coefficient, r ² = 0.982.     

Vertical distribution of <Superscript>210</Superscript>Pb and <Superscript>226</Superscript>Ra and their activity ratio in marine sediment core of the East Malaysia coastal waters

Marine sediment cores were collected from two stations at East Malaysia coastal waters on June 2004. Activity concentrations of ²¹⁰Pb in sediment core were ranged from 11 Bqkg⁻¹ to 84 Bqkg⁻¹ dry wt. for SR 01 and 4 Bqkg⁻¹ to 66 Bqkg⁻¹ dry wt. for SB 03. Meanwhile, activity concentrations of ²²⁶Ra in sediment core were varied significantly depending on the sampling location of SR 01 and SB 03 with ranged 17–26 Bqkg⁻¹ dry wt. and 8–11 Bqkg⁻¹ dry wt., respectively. The activity ratios of ²¹⁰Pb/²²⁶Ra were no significantly different at all sampling stations with an average of 1.78. Refer to the entire results; the activities of ²¹⁰Pb and ²²⁶Ra were higher at station SR 01 than station SB 03, but contrast with ratio of ²¹⁰Pb/²²⁶Ra. The reasons of different ²¹⁰Pb and ²²⁶Ra activity concentration and distribution of their ratios were strictly related to their half lives, environment origin, potential sources and behavior.     

Vertical inventories and fluxes of <Superscript>210</Superscript>Pb, <Superscript>228</Superscript>Ra and <Superscript>226</Superscript>Ra at southern South China Sea and Malacca Straits

Inventories and fluxes of ²¹⁰Pb, ²²⁸Ra and ²²⁶Ra were determined in sediment cores collected at nine stations covering of the southern South China Sea and Malacca Straits with the thickness of water column between 42 and 83 m depth. The inventories of ²¹⁰Pb, ²²⁸Ra and ²²⁶Ra were calculated range from 0.15–2.55 Bq cm⁻², 0.05–0.40 Bq cm⁻² and 6.83–83.63 Bq cm⁻², meanwhile the fluxes ranged from 0.005–0.079 Bq cm⁻² yr⁻¹, 0.009–0.048 Bq cm⁻² yr⁻¹ and 0.003–0.037 Bq cm⁻² yr⁻¹, respectively. The results show that the highest inventories and fluxes for ²¹⁰Pb, ²²⁸Ra and ²²⁶Ra were found at station WC 01 and EC 05. Because there are additional sources of ²¹⁰Pb, ²²⁸Ra and ²²⁶Ra, where water transport will brings more dissolved isotopes, influence of the transportation and deposition of suspended particles, fast rate of regeneration and greater production of those radionuclides and others.     

Chemometrics of the distribution and origin of <Superscript>226</Superscript>Ra, <Superscript>228</Superscript>Ra, <Superscript>40</Superscript>K and <Superscript>137</Superscript>Cs in plants near the West Macedonia Lignite Center (Greece)

Summary The distribution and origin of ⁴⁰K, ²²⁶Ra, ²²⁸Ra and ¹³⁷Cs has been investigated in trees, mosses and lichens in the basin of the West Macedonia Lignite Centre. In tree leaves ¹³⁷Cs is negligible, while the ²²⁶Ra and ²²⁸Ra concentrations are affected by the fly ash particles. Concerning ²²⁶Ra and ²²⁸Ra values of mosses and lichens, which are systematically larger than those of unpolluted areas, the application of chemometrics proved that they originate mainly from the lignite fly ash.     

Measuring <Superscript>137</Superscript>Cs, <Superscript>40</Superscript>K and decay products of <Superscript>226</Superscript>Ra and <Superscript>232</Superscript>Th in samples of different nature by a multidetector spectrometer

A coincidence method for measuring ¹³⁷Cs, ⁴⁰K, ²²⁶Ra and ²³²Th decay products activity in soil, vegetation and fish samples, was applied to the six-crystal gamma-coincidence spectrometer PRIPYAT-2M. In this way, some problems appeared in simultaneous measurement of ¹³⁷Cs, ²²⁶Ra and ²³²Th by NaI(Tl) detectors and the PRIPYAT-2M spectrometer were solved. The obtained results were agreeable with the HPGe spectrometer ones.     

<Superscript>226</Superscript>Ra and <Superscript>228</Superscript>Ra determination in environmental samples by alpha-particle spectrometry

A complete methodology for ²²⁶Ra and ²²⁸Ra determination by alpha-particle spectrometry in environmental samples is being applied in our laboratory using ²²⁵Ra as an isotopic tracer. This methodology can be considered highly suitable for the determination of these nuclides when very low absolute limits of detection need to be achieved. The ²²⁶Ra determination can be performed at any time after the isolation of the radium isotopes from the analyzed samples while the ²²⁸Ra determination needs to be carried out at least six months later through the measurement of one of its grand-daughters. The method has been validated by its application to samples with known concentrations of these Ra nuclides, and by comparison with other radiometric methods.     

Preparation and analysis of <Superscript>226</Superscript>Ra-<Superscript>222</Superscript>Rn emanation standards for calibrating passive radon detectors

Summary In order to calibrate vials containing charcoal for measurement of radon, emanation sources of radon were produced in-house using ²²⁶Ra salts. Calibrated emanation standards containing solution of ²²⁶Ra(NO₃)₂ absorbed into inorganic compounds were prepared. The emanation coefficient of ²²²Rn for these standards vary from 0.23-0.25. The emanation sources were found to be suitable for calibrating radon monitors.     

Determination of radionuclidic impurities in <Superscript>99m</Superscript>Tc eluate from <Superscript>99</Superscript>Mo/<Superscript>99m</Superscript>Tc generator for quality control

Technetium-99m is the principal radioisotope used in medical diagnostics; radionuclidic impurity is the major concern of its quality. This work presents a analytical method for sequential determination of all radionuclidic impurities listed in pharmacopoeia including gamma emitters, alpha emitters, ⁸⁹Sr and ⁹⁰Sr. Radioactive decay for removal of ^99mTc, ion exchange and extraction chromatography for removal of ⁹⁹Mo and ⁹⁹Tc are effective for separation of interferences. Gamma spectrometry, LSC with alpha/beta discrimination, and Cherenkov counting using LSC are sensitive methods for measurement of the impurity radionuclides. The detection limits of this method are well meet the requirement of the quality control according to the limitation of the pharmacopoeia.     

Sequential separation of <Superscript>99</Superscript>Tc, <Superscript>94</Superscript>Nb, <Superscript>55</Superscript>Fe, <Superscript>90</Superscript>Sr and <Superscript>59/63</Superscript>Ni from radioactive wastes

A sequential separation procedure has been developed for the determination of ⁹⁹Tc, ⁹⁴Nb, ⁵⁵Fe, ⁹⁰Sr and ^59/63Ni in various radioactive wastes generated from nuclear power plants. Ion exchange and extraction chromatography were adopted for individual separation of the radionuclides. Precipitation was supplementarily utilized for both purification of the individual radionuclides and preparation of the radionuclide sources for use in a radioactivity measurement. The chromatographic separation behavior of the radionuclides both from the sample matrix metals and from one another was investigated using stable metals, Re (as a surrogate of ⁹⁹Tc), Nb, Fe, Sr and Ni. The validity of the procedure for reliability and applicability was evaluated by measuring the recovery of the metal carriers added to synthetic radioactive waste solutions. The recoveries by the chromatographic separation were in the range of 84.8 to 102.2% with 2s of less than 8.6%, the recoveries by the precipitation being in the range of 84.3 to 97.3% with 2s of less than 10.9%.     

Determination and differentiation of <Superscript>226</Superscript>Ra and <Superscript>222</Superscript>Rn by gamma-ray spectrometry in drinking water

The analysis of ²²⁶Ra in natural waters can be tedious and time-consuming. For the determination and differentiation of activities of ²²⁶Ra and ²²²Rn in drinking water by γ-ray spectrometry a simple and fast method is presented. Activities of ²²⁶Ra > 0.5 Bq L⁻¹ can be determined according to stabilization of the sample without further procedures. For a more sensitive detection sample volumes of up to 5 litres are applicable by a rapid precipitation procedure without large expenditure. Further laborious enrichment methods are not necessary. Thus, detection limits of 0.1 Bq L⁻¹ can be obtained when using sample volumes of 5 litres. Therefore the method is suitable for the monitoring of radioactivity in drinking water samples in accordance with the legal guidance of the European Union.     

Influence of the physico-chemical properties of Selangor soil series on the distribution coefficient (<Emphasis Type="Italic">K</Emphasis><Subscript>d</Subscript>-value) of <Superscript>226</Superscript>Ra

²²⁶Ra is a member of the ²³⁸U natural decay series and is one of the most important isotope to be determined among the naturally occurring nuclides in environmental samples. In order to evaluate the radiation dose from ²²⁶Ra, it is important to know its mobility in different types of soils. The aim of the present study is to quantify the influence of physico-chemical soil properties on ²²⁶Ra adsorption. The distribution coefficients (K _d-value) of ²²⁶Ra in Selangor soil series samples were measured in one core, at three depth levels to evaluate the adsorbability of ²²⁶Ra. The soil samples were spiked with ²²⁶Ra tracer and the activities of ²²⁶Ra in the separated phase from batch sorption test were measured by a low background but high efficiency well-type HPGe detector. Several physico-chemical soil properties were also characterised for each soil samples. Pearson’s correlation and stepwise multiple regression test were applied at the 0.05 level of significance throughout all analysis to determine the relationships and influences between distribution coefficients (K _d-value) of ²²⁶Ra with physicochemical soil properties for the Selangor soil series. The observed K _d value was in the range of 50.55–172.28 mL g⁻¹ (mean: 93.20 ± 46.99 mL g⁻¹). The regression showed that the highest positive correlations were observed for organic matter (OM) and cation exchange capacity (CEC) (r = 0.96**, 0.81**, respectively) with K _d-values. The results indicate that the stepwise multiple regression model incorporating the soil’s OM and CEC accounts for 98% of the variability in distribution coefficients of ²²⁶Ra.     

Rapid determination of 226Ra in environmental samples

A new rapid method for the determination of ²²⁶Ra in environmental samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used for emergency response or routine sample analyses. The need for rapid analyses in the event of a Radiological Dispersive Device or Improvised Nuclear Device event is well-known. In addition, the recent accident at Fukushima Nuclear Power Plant in March, 2011 reinforces the need to have rapid analyses for radionuclides in environmental samples in the event of a nuclear accident. ²²⁶Ra (T1/2?=?1,620?years) is one of the most toxic of the long-lived alpha-emitters present in the environment due to its long life and its tendency to concentrate in bones, which increases the internal radiation dose of individuals. The new method to determine ²²⁶Ra in environmental samples utilizes a rapid sodium hydroxide fusion method for solid samples, calcium carbonate precipitation to preconcentrate Ra, and rapid column separation steps to remove interferences. The column separation process uses cation exchange resin to remove large amounts of calcium, Sr Resin to remove barium and Ln Resin as a final purification step to remove ²²⁵Ac and potential interferences. The purified ²²⁶Ra sample test sources are prepared using barium sulfate microprecipitation in the presence of isopropanol for counting by alpha spectrometry. The method showed good chemical recoveries and effective removal of interferences. The determination of ²²⁶Ra in environmental samples can be performed in less than 16?h for vegetation, concrete, brick, soil, and air filter samples with excellent quality for emergency or routine analyses. The sample preparation work takes less than 6?h. ²²⁵Ra (T1/2?=?14.9?day) tracer is used and the ²²⁵Ra progeny ²¹⁷At is used to determine chemical yield via alpha spectrometry. The rapid fusion technique is a rugged sample digestion method that ensures that any refractory radium particles are effectively digested. The preconcentration and column separation steps can also be applied to aqueous samples with good results.     

Systematic radiochemical separation for the determination of <Superscript>99</Superscript>Tc, <Superscript>90</Superscript>Sr, <Superscript>94</Superscript>Nb, <Superscript>55</Superscript>Fe and <Superscript>59,63</Superscript>Ni in low and intermediate radioactive waste samples

A simple and rapid separation procedure was systemized for the determination of ⁹⁹Tc, ⁹⁰Sr, ⁹⁴Nb, ⁵⁵Fe and ^59,63Ni in low and intermediate level radioactive wastes. The integrated procedure involves precipitation, anion exchange and extraction chromatography for the separation and purification of individual radionuclide from sample matrix elements and from other radionuclides. After separating Re (as a surrogate of ⁹⁹Tc) on an anion change resin column, Sr, Nb, Fe and Ni were sequentially separated as follows; Sr was separated as Sr (Ca-oxalate) co-precipitates from Nb, Fe and Ni followed by purification using Sr-Spec extraction chromatographic resin. Nb was separated from Fe and Ni by anion exchange chromatography. Fe was separated from Ni by anion exchange chromatography. Ni was separated as Ni-dimethylglyoxime precipitates after the removal of ^134,137Cs and ^110mAg by Cs-phosphotungstate and AgCl precipitation, respectively. Finally, the radionuclide sources were prepared by precipitation for their radioactivity measurements. The reliability of the procedure was evaluated by measuring the recovery of chemical carriers added to a synthetic radioactive waste solution.     

Determination of <Superscript>3</Superscript>H, <Superscript>226</Superscript>Ra, <Superscript>222</Superscript>Rn and <Superscript>238</Superscript>U in Austrian ground- and drinking water

Screening measurements for ³H, ²²⁶Ra, ²²²Rn and ²³⁸U in ground water were performed within a ground- and drinking water project in Austria. The aim of this project is to get an overview of the distribution of natural radionuclide activity concentration levels in ground water bodies. In some cases this water is used for drinking water abstraction. In this paper methods and results of the screening measurements are presented. Regions with high activity concentrations were identified and in these regions further investigation for ²²⁸Ra, ²¹⁰Pb and ²¹⁰Po will be conducted.     

Rapid determination of 226Ra in emergency urine samples

A new method has been developed at the Savannah River National Laboratory (SRNL) that can be used for the rapid determination of ²²⁶Ra in emergency urine samples following a radiological incident. If a radiological dispersive device event or a nuclear accident occurs, there will be an urgent need for rapid analyses of radionuclides in urine samples to ensure the safety of the public. Large numbers of urine samples will have to be analyzed very quickly. This new SRNL method was applied to 100 mL urine aliquots, however this method can be applied to smaller or larger sample aliquots as needed. The method was optimized for rapid turnaround times; urine samples may be prepared for counting in <3 h. A rapid calcium phosphate precipitation method was used to pre-concentrate ²²⁶Ra from the urine sample matrix, followed by removal of calcium by cation exchange separation. A stacked elution method using DGA Resin was used to purify the ²²⁶Ra during the cation exchange elution step. This approach combines the cation resin elution step with the simultaneous purification of ²²⁶Ra with DGA Resin, saving time. ¹³³Ba was used instead of ²²⁵Ra as tracer to allow immediate counting; however, ²²⁵Ra can still be used as an option. The rapid purification of ²²⁶Ra to remove interferences using DGA Resin was compared with a slightly longer Ln Resin approach. A final barium sulfate micro-precipitation step was used with isopropanol present to reduce solubility; producing alpha spectrometry sources with peaks typically <40 keV FWHM (full width half max). This new rapid method is fast, has very high tracer yield (>90 %), and removes interferences effectively. The sample preparation method can also be adapted to ICP-MS measurement of ²²⁶Ra, with rapid removal of isobaric interferences.     

An accurate method for the determination of <Superscript>226</Superscript>Ra activity concentrations in soil

A quantitative method to determine the activity concentration of ²²⁶Ra in soil samples was established using high performance environmental gamma-ray spectrometry. In this method, a semi-empirical calibration procedure was developed for full energy peak efficiency calculation utilizing the elemental composition of the soil sample. Aatami software was used to deconvolute the ²³⁵U and ²²⁶Ra doublet at 185.7 keV and 186.2 keV, respectively, and to fit the baseline of the soil gamma-spectrum for the determination of ²²⁶Ra activity. The results indicated that the Aatami doublet deconvolution procedure provides a rapid and accurate analysis of a complicated spectrum in comparison with other cumbersome spectral interference correction methods. The study also compared the results with those obtained by radon progeny (²¹⁴Pb, or ²¹⁴Bi) measurements and found that the deconvolution method provided a more accurate ²²⁶Ra activity as it is independent of the error caused by radon diffusion. This error can be quite large since the amount of escaped radon gas through the sample container walls and sealing cannot be accurately quantified.     

The226Ra/Ba-ratio as indicator for phosphogypsum contributions to226Ra levels in sediments

Phosphogypsum discharges by phosphate-ore processing industries pollute sediments of the Rotterdam harbour area with²²⁶Ra. Direct measurement of this radionuclide in sediments does not provide a reliable indication of the elevation of the levels, since²²⁶Ra levels in sediments depend on the particle size. To eliminate the size effect, the²²⁶Ra/Ba ratio in sediments was tested as a possible indicator for the²²⁶Ra in the discharges. The results indicate almost a doubling of the²²⁶Ra levels in sediment samples due to phosphogypsum discharges. The contribution of phosphogypsum to the sediment mass was calculated in the order of a few percent equivalent.     

Comparison of analytical methods used to determine <Superscript>235</Superscript>U, <Superscript>238</Superscript>U and <Superscript>210</Superscript>Pb from sediment samples by alpha,beta and gamma spectrometry

An intercomparison of the methodology (alpha, beta and gamma spectrometry) used for ²³⁸U, ²³⁵U and ²¹⁰Pb determination was carried out based on 38 sediment samples. The activity range of the samples varied from 10–700 Bq/kg for ²¹⁰Pb, 1–35 Bq/kg for ²³⁵U and 10–800 Bq/kg for ²³⁸U. Results obtained using the three methods were not statistically different at high activity levels, but agreement between the results decreased at lower sample activity levels. For ²¹⁰Pb, the smallest difference was found between alpha and gamma spectrometry. A good correlation between results from alpha and gamma spectrometry was observed over the whole activity range. In beta spectrometry, the results were slightly higher than those obtained by alpha or gamma spectrometry due to the impurity of ²²⁸Ra. In ²³⁸U analysis, good correspondence was observed between ²³⁸U determined by gamma and alpha spectrometry, particularly at higher ²³⁸U activity concentrations over 100 Bq/kg. In ²³⁵U analysis, attention needs to be paid to interference from ²²⁶Ra and its reduction.     

Radium isotopes and <Superscript>222</Superscript>Rn in Austrian drinking waters

The activity concentrations of the Ra isotopes, ²²⁶Ra and ²²⁸Ra, as well as of ²²²Rn were measured in Austrian tap waters. Rn was extracted into a mineral oil cocktail not miscible with water and measured by liquid scintillation counting using pulse-shape analysis for α/β-separation. Ra isotopes were co-precipitated with BaSO₄ or concentrated by filtration through an element specific filter. EDTA solution was used to redissolve the precipitate as well as to release the Ra from the filter. After mixing with a cocktail, the EDTA solution was measured by liquid scintillation counting, too. From our results the effective ingestion doses for adults and 3 months old babies were calculated.     

Analysis of 36Cl in Savannah River Site radioactive waste

The present work shows the activity levels of ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that ⁴⁰K and ²²⁸Ra concentration is nearly uniform throughout the studied area while ²²⁶Ra and ¹³⁷Cs are more concentrated in the southern regions of the bay. The significant variation in the activity levels of radionuclides within the study site might be due to their sorption/desorption processes onto the surface of sediment materials. The low mean value of ²²⁶Ra/²²⁸Ra ratio (0.72) in the sediments indicates that ²³⁸U has relatively greater solubility and mobility than ²³²Th. Similarly, low activity ratio (0.18) for ¹³⁷Cs/⁴⁰K reflects the presence of very high content of ⁴⁰K in sediment due to presence of primary minerals in sediment. Silt and clay were reported to dominate the composition of the sediment. A significant positive correlation between ²²⁶Ra and ²²⁸Ra and ¹³⁷Cs and ⁴⁰K suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system.