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.     

Investigation of radioactivity level in soil and drinking water samples collected from the city of Erzincan,Turkey

This study is part of an effort to assess the level of background radiation for Erzincan Province of eastern Turkey. Radionuclide activity concentrations in soil samples were measured through gamma-ray spectrometry and the average activities were determined as 8.93, 11.39, 281.94, and 9.52 Bq/kg for the radionuclides ²³⁸U, ²³²Th, ⁴⁰K, and ¹³⁷Cs, respectively. The average annual effective dose from these natural radioactivity sources (²³⁸U series, ²³²Th series and ⁴⁰K,) was calculated to be 27.9 μSv. Radioactivity levels in drinking and potable water samples were studied using a multi-channel low level proportional counter. The average gross alpha activity concentration was found to be 0.0477 Bq/L (min. 0.007 Bq/L; max. 0.421 Bq/L) and the average gross beta activity was measured as 0.104 Bq/L (min. 0.008 Bq/L; max. 1.806 Bq/L). These values lead to an average annual effective dose of 9.75 μSv from the alpha emitters and 56.34 μSv from the beta emitting radionuclides in water. The radioactivity levels in the water samples investigated were found to comply with the reference levels recommended by WHO and the regulations set forth by the Turkish Health Ministry.     

Comparative determination of uranium in rock phosphates and columbite by ICP-OES,alpha &; gamma spectrometry

During this work selective separation of uranium from rock phosphate and columbite mineral was done before its quantitative estimation by using Inductively Coupled Plasma Optical Emission Spectrometery (ICP-OES). Uranium from the rock phosphate and columubite was extracted by sodium peroxide fusion followed by leaching in 2 M HNO₃. To avoid spectral interference in the estimation of uranium by ICP-OES, the selective separation of uranium from the leachate was carried out by using two different extractants, 30% Tributyl Phophates (TBP) in CCl₄ and a equi-volume mixture of Di(2-ethylhexyl) phosphoric acid (D2EHPA) & TBP in petrofin. Uranium was stripped from the organic phase by using 1 M ammonium carbonate solution. Determination of uranium by ICP-OES was done after dissolving the residue left after evaporation of ammonium carbonate solution in 4% HNO₃. The concentration of the uranium observed in the rock phosphates samples was 40–200 μg g⁻¹ whereas in columbite samples the concentration range was 100–600 μg g⁻¹. Uranium concentration evaluated by ICP-OES was complimented by gamma & alpha spectrometry. Concentration of uranium evaluated by gamma spectrometry in case of rock phosphate and coulmbite was in close agreement with the uranium content obtained by ICP-OES. Uranium determination by alpha spectrometry showed only minor deviation (1–2%) from the results obtained by ICP-OES in case of rock phosphates whereas in case of coulmbites results are off by 20–30%.     

Reduction of <Superscript>68</Superscript>Ge activity containing liquid waste from <Superscript>68</Superscript>Ga PET chemistry in nuclear medicine and radiopharmacy by solidification

PET with ⁶⁸Ga from the TiO₂- or SnO₂- based ⁶⁸Ge/⁶⁸Ga generators is of increasing interest for PET imaging in nuclear medicine. In general, radionuclidic purity (⁶⁸Ge vs. ⁶⁸Ga activity) of the eluate of these generators varies between 0.01 and 0.001%. Liquid waste containing low amounts of ⁶⁸Ge activity is produced by eluting the ⁶⁸Ge/⁶⁸Ga generators and residues from PET chemistry. Since clearance level of ⁶⁸Ge activity in waste may not exceed 10 Bq/g, as stated by European Directive 96/29/EURATOM, our purpose was to reduce ⁶⁸Ge activity in solution from >10 kBq/g to <10 Bq/g; which implies the solution can be discarded as regular waste. Most efficient method to reduce the ⁶⁸Ge activity is by sorption of TiO₂ or Fe₂O₃ and subsequent centrifugation. The required 10 Bq per mL level of ⁶⁸Ge activity in waste was reached by Fe₂O₃ logarithmically, whereas with TiO₂ asymptotically. The procedure with Fe₂O₃ eliminates ≥90% of the ⁶⁸Ge activity per treatment. Eventually, to simplify the processing a recirculation system was used to investigate ⁶⁸Ge activity sorption on TiO₂, Fe₂O₃ or Zeolite. Zeolite was introduced for its high sorption at low pH, therefore ⁶⁸Ge activity containing waste could directly be used without further interventions. ⁶⁸Ge activity containing liquid waste at different HCl concentrations (0.05–1.0 M HCl), was recirculated at 1 mL/min. With Zeolite in the recirculation system, ⁶⁸Ge activity showed highest sorption.     

A facile and novel process for the preparation of <Superscript>147</Superscript>Pm source

Aiming the selective recovery of palladium from high level radioactive liquid waste (HLW), a chelating thiamide type sorbent, CWP–TU, was prepared by the modification of Japanese cedar wood powder (CWP). Convection oven and microwave heating were separately used for modification purpose and found that microwave heating is more effective over oven heating. CWP–TU was extensively studied for the adsorption of Pd(II) from nitric acid medium. The batch test showed that nitric acid concentration of 3 M or higher is favorable for Pd(II) loading. Consistent adsorption of Pd(II) under gamma irradiation condition demonstrated the feasibility of using CWP–TU in real HLW. Also, Pd(II) only adsorption from simulated HLW solution verified the palladium only selectivity of the sorbent as well as the lack of influence of coexisting metal ions on its affinity toward Pd(II). CWP–TU holds maximum Pd(II) loading capacities of 0.98 mol/kg at 30 °C and 1.04 mol/kg under gamma irradiation. A comparative study using some ion exchange resins revealed that the resins are either ineffective in nitrate medium or lack stability under irradiation.     

C-14 and H-3 contents in the groundwater around radioactive repository site in Korea

The contents of H-3 and C-14 in groundwater and surface waters around low and medium-level atomic waste repository site in Korea were determined. The concentrations of C-14 were in the range 0.186–0.287 Bq/L. The H-3 concentration of the groundwaters and surface waters were <0.06–5.75 and 1.22–4.74 Bq/L. The average H-3 contents of west, north and south direction were 1.18 ± 0.12, 1.11 ± 0.78 and 2.85 ± 2.66. H-3 and C-14 concentrations in the south direction were relatively higher than west and north direction samples. The surface waters sampled from catchment were four times higher than average H-3 concentration in precipitation. The concentrations of H-3 and C-14 within 5 km area samples were much higher than other samples.     

Standardization of calibration procedures for quantification of gross alpha and gross beta activities using liquid scintillation counter

Simultaneous measurement of gross alpha and gross beta activities by liquid scintillation counting technique using LKB Wallac Quantulus 1220 liquid scintillation counter (LSC) equipped with Pulse Shape Analyzer (PSA) is described. Three sets of pure alpha and pure beta standards simulating the activity concentration values of real samples in terms of α/β activity ratios were used to calibrate the LSC. Calibration methodology for the Quantulus 1220 with respect to the above measurements using ²⁴¹Am and ⁹⁰Sr/⁹⁰Y standards of respective activity concentrations of ~25 dpm and ~10⁴ dpm is described in detail. Also highlighted the need to calibrate the LSC using another set of ²⁴¹Am and ⁹⁰Sr/⁹⁰Y standards of low and high activity concentrations respectively. The practicability and working performance of these calibration plots was checked by the validation trials with test samples spiked with ²⁴¹Am and ⁹⁰Sr/⁹⁰Y covering range of α/β activity ratios from 1:1 to 1:50.     

Estimation of plutonium present in 200 litre waste drums containing high amount of beta gamma activity

The segmented gamma ray scanning system developed for the assay of plutonium present in 200?L waste drums was modified for the estimation of gram amounts of plutonium in the presence of high beta gamma activity. A multi gamma ray source of ¹⁵²Eu having?~1?mCi activity was used for the determination of attenuation correction factors for high count rate drums. Dead time corrections were applied to arrive at the corrected count rates for all the gamma rays. Present study has shown that the estimation of?~1?g of ²³⁹Pu in a waste drum can be carried out in the presence of ¹³⁷Cs up to an activity level of 20?mCi.     

Radioactivity of plutonium isotopes, <Superscript>137</Superscript>Cs and their ratio in sediment,seawater and biota from the east coast of Peninsular Malaysia

This study with sampling expeditions of marine sediment, seawater and biota were performed at 30 stations within Malaysian Exclusive Economic Zone (EEZ). A total of >400 samples were collected to determine the activity concentration of anthropogenic radionuclides (^239+240Pu, ¹³⁷Cs) and their activity ratio (^239+240Pu/¹³⁷Cs) in sediments, seawater and biota. The purpose of this study was to determine the concentration levels for these radionuclides and to evaluate any occurrence of radioactive contamination. Sediment cores were obtained using multicorer device, while water samples via co-precipitation techniques and biota was purchased from local fishermen. The activity concentrations of ^239+240Pu in sediment, seawater and biota were ranged 0.21–0.45 Bq/kg dry wt., 2.33–7.95 mBq/m³ and <0.008 Bq/kg fresh wt., respectively. Meanwhile, the values of ¹³⁷Cs were ranged <1.00–2.71 Bq/kg dry wt. in sediment, 3.40–5.89 Bq/m³ in seawater and <0.05–0.41 Bq/kg fresh wt. in biota, respectively. Activity ratios of ^239+240Pu to ¹³⁷Cs obtained seem to confirm that these artificial radioactivities were mainly due to global nuclear fallout.     

Optimization study on sample pretreatment of spent fuel storage rack

In order to evaluate radionuclide inventories as an essential item for the permanent disposal of spent fuel storage racks, chemical conditions for a sample pretreatment of a spent fuel storage rack were studied. Especially, the surface microstructure and the radionuclide distributions for the spent fuel storage rack were investigated by using a SEM–EDX and γ-spectrometer for minimizing the matrix effect which could affect a chemical separation process of some β-emitting radionuclides. The samples were pretreated with a mixed solution of 5 M HCl and 2 M HNO₃ by an ultrasonic surface leaching method. Some radionuclides in the raw racks showed the radioactivity of 10²–10³ Bq for about 10 g of sample weight. From the sample pretreatment, it was confirmed that almost all radionuclides in the rack were completely extracted from the rack when the dissolved thickness of the rack became a maximum 15 μm by the ultrasonic surface leaching method. The established pretreatment method was applied for all spent fuel storage rack generated from Korean NPPs to determine the scaling factor. The radioactivities of ⁶⁰Co and ¹³⁷Cs radionuclides in the pretreated solutions were in the range of 4.9E−1~1.5E+2 and 1.2E−1~9.0E+0 Bq/g, respectively.     

Low level detection of <Superscript>135</Superscript>Cs and <Superscript>137</Superscript>Cs in environmental samples by ICP-MS

The measurement of fission product cesium isotopes ¹³⁵Cs and ¹³⁷Cs at low femtogram (fg) 10⁻¹⁵ levels in ground water by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) is reported. To eliminate the natural barium isobaric interference on the cesium isotopes, in-line chromatographic separation of the cesium from barium was performed followed by high sensitivity ICP-MS analysis. A high efficiency desolvating nebulizer system was employed to maximize ICP-MS sensitivity ~10 cps/fg. The three sigma detection limit for ¹³⁵Cs was 2 fg/mL (0.1 μBq/mL) and for ¹³⁷Cs 0.9 fg/mL (0.0027 Bq/mL) measured from the standard with analysis time of less than 30 min/sample. Cesium detection and 135/137 isotope ratio measurement at very low femtogram levels using this method in a spiked ground water matrix is also demonstrated.     

AMicro-sized headspace GC technique for determination of organic volatile impurities in water-insoluble pharmaceuticals

Summary A micro-sized headspace technique is presented for determination of organic volatile impurities (OVIs) in water-insoluble pharmaceuticals. Its main features include reduction of the amounts of sample of drug and sample dissolution medium, from 100–200 mg and 1–5 mL, respectively, in the traditional headspace method to 5–30 mg and 100 μL in the micro-sized headspace method, and shortening the headspace equilibration time from 45–60 min to 5–10 min. The validity of method has been examined both experimentally and theoretically. The relative standard deviation of the analysis and the linearity of method satisfied the requirements of the United States Pharmacopoeia. It was found that headspace equilibrium conditions have little influence on the sensitivity of the method, and that the presence of different amounts of drug substance in the sampling solution has little effect on the analytical results, in contrast with the traditional headspace GC method.     

Anion Effects on Sodium Ion and Acid Molecule Adduction to Protein Ions in Electrospray Ionization Mass Spectrometry

Gaseous protein–metal ion and protein–molecule complexes can be readily formed by electrospray ionization (ESI) from aqueous solutions containing proteins and millimolar concentrations of sodium salts of various anions. The extent of sodium and acid molecule adduction to multiply charged protein ions is inversely related and depends strongly on the proton affinity (PA) of the anion, with extensive sodium adduction occurring for anions with PA values greater than ~300 kcal·mol^–1 and extensive acid molecule adduction occurring for anions with PA values less than 315 kcal·mol^–1. The role of the anion on the extent of sodium and acid molecule adduction does not directly follow the Hofmeister series, suggesting that direct protein–ion interactions may not play a significant role in the observed effect of anions on protein structure in solution. These results indicate that salts with anions that have low PA values may be useful solution-phase additives to minimize nonspecific metal ion adduction in ESI experiments designed to identify specific protein-metal ion interactions.     

Polymer-coated magnetic nanoparticles for rapid bioassay of <Superscript>90</Superscript>Sr in human urine samples

A rapid bioassay for ⁹⁰Sr was developed involving preconcentration of ⁹⁰Sr/⁹⁰Y from human urine samples with a cation exchange polymer (poly–acrylamido–methyl–propanesulfonic acid) coated onto magnetic nanoparticles, followed by selective elution of ⁹⁰Sr (over ⁹⁰Y) with phosphate for determination by liquid scintillation analysis. The minimum detectable activity for this method (4.9 ± 0.5 Bq/L) is lower than the required sensitivity of 19 Bq/L for ⁹⁰Sr in human urine samples, as defined in the requirements for radiation emergency bioassay techniques for the public and first responders based on the dose threshold for possible medical attention recommended by the International Commission on Radiological Protection. The relative bias was 9.2%, the relative precision was 3.2%, and the linear dynamic range covered 12–600 Bq/L. This simple and rapid bioassay method is found to be in compliance with the HPS ANSI N13.30 performance criteria for radiobioassay.     

Effect of media composition and growth conditions on production of β-glucosidase by Aspergillus niger C-6

The hydrolytic activity of fungal originated β-glucosidase is exploited in several biotechnological processes to increase the rate and extent of saccharification of several cellulosic materials by hydrolyzing the cellobiose which inhibits cellulases. In a previous presentation, we reported the screening and liquid fermentation with Aspergillus niger, strain C-6 for β-glucosidase production at shake flask cultures in a basal culture medium with mineral salts, corn syrup liquor, and different waste lignocellulosic materials as the sole carbon source obtaining the maximum enzymatic activity after 5–6 d of 8.5 IU/mL using native sugar cane bagasse. In this work we describe the evaluation of fermentation conditions: growth temperature, medium composition, and pH, also the agitation and aeration effects for β-glucosidase production under submerged culture using a culture media with corn syrup liquor (CSL) and native sugar cane bagasse pith as the sole carbon source in a laboratory fermenter. The maximum enzyme titer of 7.2 IU/mL was obtained within 3 d of fermentation. This indicates that β-glucosidase productivity by Aspergillus niger C-6 is function of culture conditions, principally temperature, pH, culture medium conditions, and the oxygen supply given in the bioreactor. Results obtained suggest that this strain is a potential microorganism that can reach a major level of enzyme production and also for enzyme characterization.     

Impact of season and location on the natural radioactivity in marine macroalgae (<Emphasis Type="Italic">Gracilaria edulis)</Emphasis> of coastal Tamil Nadu,India

Gracilaria edulis, an edible red marine macro algae from three high background radiation areas (Arockiapuram, Kadiapattinam and Kurumpanai) on the southwest coast of Tamil Nadu, and one low background radiation area (Mandapam) on the southeast coast of Tamil Nadu, in India, were studied for variations in average gross alpha and beta radiation activities. Significant variations in average gross beta activities were observed while alpha activities showed only marginal variation. The average gross alpha activity was recorded high (61.51 Bq kg ⁻¹) during the post southwest monsoon season, while it recorded lowest (25.48 Bq kg ⁻¹) during the post northeast monsoon season. Average gross beta activity varied between seasons with the lowest level (211.55 Bq Kg⁻¹) during post southwest monsoon season and the highest (413.33 Bq kg ⁻¹) during post northeast monsoon season. Among the four locations, the gross alpha activity was high (70.95 ± 26.74 Bq Kg⁻¹) in Arockiapuram and low (18.74 ± 6.32 Bq Kg⁻¹) in Mandapam, while the gross beta activity was high (442.25 ± 168.53 Bq Kg⁻¹) in Kurumpanai and low (158.63 ± 34.37 Bq Kg⁻¹) in Mandapam. Average gross alpha activity in G. edulis was found significantly varying in terms of locations, while average gross beta activity for the same species recorded significant seasonal variation.     

Assessment of natural radioactivity in soil samples and comparison of direct and indirect measurement of environmental air kerma rate

This study presents the high purity germanium (HPGe) gamma spectrometric measurement of natural radioactivity mainly due to ²²⁶Ra, ²³²Th and ⁴⁰K in soil samples collected in Ferozepur and Faridkot district of Punjab, India. ²²⁶Ra activity varied from 28.6 to 51.1 Bq kg⁻¹ with the mean of 39.7 Bq kg⁻¹. The range and mean activity of ²³²Th were 42.9–73.2 and 58.2 Bq kg⁻¹, respectively. ⁴⁰K activity was in the range of 470.9–754.9 Bq kg⁻¹ with the mean of 595.2 Bq kg⁻¹. The air kerma rate (AKR) at 1 m height from the ground was also measured using gamma survey meter in all the sampling locations, which was ranging from 92.1 to 122.8 nGy h⁻¹ with the mean of 110.6 nGy h⁻¹. The radiological parameters such as Ra_eq and activity index of the soil samples were also evaluated, which are the tools to assess the external radiation hazard due to building materials. The mean and range of the Ra_eq values were 168.7 and 132.9–210.4 Bq kg⁻¹, respectively, whereas the activity index varied from 0.5 to 0.8 with the mean value of 0.62. These indices show that the indoor external dose due to natural radioactivity in the soil used for the construction will not exceed the dose criteria. The AKR was also evaluated from soil activity concentration and altitude correction of cosmic radiation contribution. The statistical tests such as Pearson correlation, spearman rank correlation, box and whisker plot, the Wilcoxon/Mann–Whitney test and chi-square test, were used to compare the measured AKR with evaluated AKR, which indicates good correlation.     

Determination of gross alpha and beta activities in seawater and plankton from the Upper Gulf of Thailand

Gross alpha and beta activities were determined in seawater and plankton samples collected during the wet and dry seasons from 10 different sampling stations in Chonburi, the Upper Gulf of Thailand. Seawater samples were sampling, 1 km from the coastal and 2 m below the water surface, during July 2008 to July 2009. Seawater samples were prepared by coprecipitation technique. Plankton samples were prepared by filtration and dryness on filter paper. Both types of samples were counted using a low background alpha/beta proportional counter with multiple detector type (Berthold LB770). The results showed that gross alpha activities in seawater and plankton sample are in the range of 0.0591 ± 0.0209–0.3914 ± 0.0606 Bq/l and 0.0029 ± 0.0020–0.0294 ± 0.0043 Bq/l, respectively and also showed the lowest and highest activity level in the same sampling time. The activities of gross beta in seawater and plankton sample are in the range of 0.2803 ± 0.0177–1.3064 ± 0.0319 Bq/l and 0.0208 ± 0.0123–0.9151 ± 0.0262 Bq/l, respectively. Minimum detectable activity (MDA) had been observed in the measurements. The MDA of seawater sample were estimated to be 0.0832 Bq/l for alpha and 0.0577 Bq/l for beta at counting time of 100 and 200 min, respectively. In plankton samples, the MDA were estimated to be 0.0053 Bq/l for alpha and 0.0409 Bq/l for beta at the same counting time of 250 min.     

Degradation of alachlor herbicide by gamma radiation from cobalt-60 in aqueous and alcohol solution

Alachlor has been widely used in agriculture all over the world. It is suggested that it may be a carcinogen and an environmental estrogen. The aim of this work was to verify the degradation the alachlor by gamma radiation. Gamma radiation from ⁶⁰Co was used to degrade the alachlor herbicide in water and methanol solution. The alachlor in water and alcohol solution in the concentration of 100 mgL⁻¹ was irradiated with doses of 0.25–50 kGy, at dose rate 5–6 and 2.7 kGyh⁻¹. High performance liquid chromatography was used as an analytical technique to determine the degradation rate of herbicide studied.     

Bright blue pigment CoAl<Subscript>2</Subscript>O<Subscript>4</Subscript> nanocrystals prepared by modified sol–gel method

Nanocrystalline films of magnetite have been prepared by a novel sol–gel route in which, a solution of iron (III) nitrate dissolved in ethylene glycol was applied on glass substrates by spin coating. Coating solution showed Newtonian behaviour and viscosity was found as 0.0215 Pa.s. Annealing temperature was selected between 291 and 350 °C by DTA analysis in order to obtain magnetite films. In-plane grazing angle XRD and TEM studies showed that magnetite phase was present upon annealing the films at 300 °C. The films had crack free surfaces and their thicknesses varied between ~10 and 200 nm. UV–Vis spectrum results showed that transmittance of the films increases with decreasing annealing temperature and increasing spinning rate. Up to 96% transmittance was observed between the wavelengths of 900–1,100 nm. Vibrating sample magnetometer measurements indicated that magnetite thin films showed ferromagnetic behavior and the saturation magnetization value was found as ~35 emu/cm³.