Radiostrontium determination by combination of automated Sr isolation and "on-column" Cherenkov detection using chromatographic model.

A novel analytical solution of non-linear chromatography in case of parabolic isotherm for frontal analysis was obtained by combination of Cole-Hopf and Laplace transform. It was used for simulation of strontium capturing on chromatographic column with aim to improve quantitative determination of low-level 90Sr activities. From the experimentally determined breakthrough curves, the retention factor and the number of theoretical plates were calculated using the Glueckauf and Wenzel relations and by fitting the breakthrough curves for the linear isotherm using MatLab. These were used to simulate the breakthrough curves using a parabolic isotherm solution where the non-linear term of the isotherm was taken as a small negative deviation of the retention factor. On the base of theoretical prediction and experimental data, procedure for automated capturing of strontium on chromatographic column with specific dimension and off line "on-column" Cherenkov detection on commercial ultra low-level liquid scintillation counter was developed. It was shown that analytical solution for parabolic isotherm in comparison with solution for linear isotherm gives better prediction of mass of captured Sr on column filled with small amount of Sr resin and SuperLig®620 in case of elevated Sr concentration, even when non-linear effect is not obvious. The solution also makes it possible to predict the mass of resin required for strontium isolation at 100% yield under given conditions. Considering the limited dimensions of the column, and consequently small mass of the resin in them, it resulted in the low efficiency of the columns, which, however, did not affect the yield in real conditions of isolation. The results have shown that the yields achieved after isolation on SuperLig®620 from real samples are 100%. In addition, it is shown that captured 90Sr can be detected through 90Y ingrowth, on column filled with strontium specific resin, with Cherenkov detection efficiency of at least 50%. The efficiency may be enhanced to 60%, depending on parameters which can affect detection efficiency change (type of column, resin type, surrounding solution, etc.). The developed procedures enable quantitative determination of 90Sr in natural water samples with MDAC below 12 mBq l-1 and solid (soil and vegetation) samples with MDAC below 6 Bq kg-1 within 2-3 days. The proposed solution may easily be implemented in radiochemical laboratories where this type of analysis is routinely done within environmental monitoring or other purposes.

Synergy of flow injection system and molecular recognition technology products for rapid determination of 89,90Sr and 210Pb.

A rapid, automated separation procedure was developed for radioactive strontium and lead isotope determination. This system includes a portable automated system for the preconcentration and sequential elution of targeting isotopes with an Na2H2EDTA solution from solid phase extraction materials, AnaLig®Sr-01 and SuperLig®620, provided by IBC Technologies. Strontium and lead were separated from the majority of matrix constituents to obtain pure fractions of Pb and Sr prior to radiometric detection. In case of barium presence, it can also be fully isolated and completely separated from Sr. The automated procedure can be successfully used for preconcentration and separation from high as well as low radioactivity samples. With only a 1 mL column filled with SuperLig®620, it is possible to isolate Sr and Pb with 100% recovery from 1 L to 2 L of sample at a flow rate of up to 10 mL min-1 within several hours. 89,90Sr isotopes can be further determined by Cherenkov counting, while 210Pb isotopes can be determined by either gamma spectrometry or liquid scintillation counter. The method was tested and validated using certified standard materials and proficiency test samples. The synergy of automated separation and detection procedures enables the determination of the low level activity of 90Sr and 210Pb in a short time with detection limits of 20 mBq L-1 for both isotopes. The proposed method enables lower labour costs, minimal size of apparatuses and columns, low separation time, and reduced secondary waste production. The automated procedure may be easily implemented in laboratories worldwide and can also be used at sampling sites.

Efficient separation of strontium radionuclides from high-salinity wastewater by zeolite 4A synthesized from Bayer process liquids.

The efficient, selective, and economical sorbents for the removal of Sr radionuclides are largely needed for the decontamination of effluents with high salinity. In this study, the removal of Sr was investigated using the zeolite produced from the Bayer process liquids. Based on the XRD, SEM/EDS analysis, the product was pure and highly crystalline zeolite 4A (Z4A). Removal of Sr was fast (5 min for 100% removal at 8.80 mg/L), with high maximum sorption capacity (252.5 mg/L), and independent on the initial pH in the range 3.5-9.0. Specific sorption of Sr by protonated groups on the Z4A surface was operating in addition to ion-exchange with Na ions. The selectivity of Z4A decreased in the order Sr > Ca > K > Mg > Na. 84% of Sr was separated from seawater within 5 min, at the Z4A dose of 5 g/L, while efficiency increased to 99% using the dose of 20 g/L. Desorption of radioisotope 89Sr from seawater/Z4A solid residue was very low in deionized water (0.1-0.2%) and groundwater (0.7%) during 60 days of leaching. Z4A is a cost-effective, selective, and high-capacity medium for Sr removal, which provides high stability of retained radionuclides.

Comparison of different methodologies for the 90Sr determination in environmental samples.

The paper describes different isolation/separation and detection procedures for 90Sr determination in the environmental samples which are routinely used in Laboratories A and B. In this context, four different methods for strontium isolation and two methods for detection were tested and compared by 90Sr determination in proficiency test samples (water, soil, vegetation) and animal bone samples. The chromatographic isolation of Sr on Sr resin, AnaLig®Sr01 resin gel, strong base anion exchange resins in nitrate form and combination of strong base anion exchange and Sr resin were used for the examination of the impact of sample matrix constituents on efficiency of strontium isolation (chemical yield), while Cherenkov counting of 90Y and counting of 90Sr(90Y) on proportional counter were used for the quantitative 90Sr determination. The chemical yields obtained with different isolation methods were compared with the emphasis on its influence on reliability of the 90Sr determination in different kinds of samples. The results show that the efficiency of strontium isolation depends on type of sample and separation methodology. The strontium yield on Sr resin column decreases with the increase of Sr, Ca and Na concentration. In the presence of 1 g of Ca and 1 g of Na, the yield of 85% was obtained for 5 mg of Sr carrier and dropped below 50% with further increase of Sr and other elements. However, the yield can be increased to 75% if Na and part of Ca are separated from Sr on the anion exchange column with alcoholic solution of nitric acid and by final separation of Ca from Sr on the Sr resin column. In the presence of large amounts of Ca, Na and other elements, isolation efficiency on the Sr resin column significantly decreases in comparison with other methods. The average yield for isolation from vegetation samples on the Sr resin column is only 21%. For the soil samples the highest average yield (78%) is obtained for the isolation in the combination of anion exchange and Sr resin columns. For the isolation from bone samples the average yields over 80% are on AnaLig®Sr01 and anion exchange resins columns, while Sr resin was not used for separation due to high content of Ca in samples. The results of the 90Sr determination in proficiency testing (PT) samples show that the accuracy of the determination does not depend on high chemical yield but depends on accuracy of yield determination. The analysis of z-values shows that 96% of obtained z-values range from 0 to ±2 while 77% of z-values range between 0 and ± 1. Ninety percent of obtained results of 90Sr determination deviate less than 20% from assigned values in PT provider reports. The results of 90Sr determination in animal bone samples using different methods are in good agreement. The results obtained by Cherenkov counting in both laboratories vary from -3.1-14.5% while results obtained by determination via 90Y and counting on i-Matic vary between -10.0 and -2.9%. These deviations are in accordance with deviations obtained with PT samples. Activity concentrations of 90Sr in wild boar bone samples range from 4 to 30 Bq kg-1 while in deer bone samples from 2 to 8 Bq kg-1.

137Cs in mushrooms from Croatia sampled 15-30 years after Chernobyl.

The aim of this study was to select species with higher potential to accumulate 137Cs among the available mushroom species, by determining the activity concentrations of 137Cs in mushrooms collected along north and north-western part of Croatia. A total of 55 samples of 14 different species were analyzed and the potential of mycorrhizal and saprotrophic species to accumulate 137Cs was compared. A wide range of the dry weight activity concentrations of 137Cs was detected, ranging from 0.95 to 1210 Bq/kg (154 Bq/kg mean value; 52.3 Bq/kg geometric mean) in mycorrhizal and 1.05-36.8 Bq/kg (8.90 Bq/kg mean value; 5.49 Bq/kg geometric mean) in saprotrophic species. Statistical analyses showed that mycorrhizal species accumulate significantly higher concentrations of 137Cs and thus could perform better as long-term bioindicators of environmental pollution by radiocaesium then saprotrophic species. The comparison of Boletus sp. and Hydnum repandum (both mycorrhizal species commonly found in Croatia) showed, in general order of magnitude, higher accumulation in Hydnum repandum. Clearly, mushrooms, especially mycorrhizal species, can be used as significant indicators even decades after the occurrence of any serious 137Cs contamination event. However, as a wide range of values indicates that various parameters may influence the total uptake of the 137Cs into the mushroom fruit bodies, it is necessary to emphasize that 137Cs activity detected in a single mushroom sample is very site-specific.

Measurement of tritium in the Sava and Danube Rivers.

Two nuclear power plants (NPP), the KrskoNPP (Slovenia) on the Sava River and the Paks NPP (Hungary) on the Danube River, are located in the immediate vicinity of Croatia and Serbia. Some of the radioactivity monitoring around the NPPs involves measuring tritium activity in the waters of rivers and wells. The authors present the tritium measurement results taken over several years from the Sava and Danube Rivers, and groundwater. The measurements were carried out in two laboratories including an impact assessment of the tritium released into the rivers and groundwater. The routine methods for determining tritium (with/without electrolytic enrichment) were tested in two laboratories using two different instruments, a Tri-Carb 3180 and Quantulus 1220. Detection limits for routine measurements were calculated in compliance with ISO 11929 and Currie relations, and subsequently the results were compared with those determined experimentally. This has shown that tritium can be reliably determined within a reasonable period of time when its activity is close to the calculated detection limit. The Krsko NPP discharged 62 TBq of tritium into the River Sava over a period of 6 years (23% of permitted activity, 45 TBq per year). The natural level of tritium in the Sava River and groundwater is 0.3-1 Bq/l and increases when discharges exceed 1 TBq per month. Usually, the average monthly activity in the Sava River and groundwater is maintained at a natural level. The maximum measured activity was 16 Bq/l in the Sava River and 9.5 Bq/l in groundwater directly linked to the river. In the majority of water samples from the Danube River, measured tritium activity ranged between 1 and 2 Bq/l. The increased tritium levels in the Danube River are more evident than in the Sava River because tritium activity above 1.5 Bq/l appears more frequently on the Danube River. All measured values were far below the allowed tritium limit in drinking water. Dose assessment has shown that tritium released from NPPs contributes negligibly to annual doses in comparison to natural sources.

Sequential separation of Fe and Sr from liquid samples by using Sr resin and rapid determination of 55Fe and (89,9°)Sr.

The obtained results showed that the Sr resin can be used for the chromatographic separation of Fe (III) and Sr (II) ions by using a mixture of HCl and HNO3. It was shown that the binding strength of Fe (III) decreases with increasing concentration of HNO3 while the binding strength of Sr (II) increases. It was found that the optimal bonding strength is achieved in 6 mol/L HCl:3 mol/L HNO3 and varying concentrations of acid in the mixture allow their selective separation. On basis of these results, a method for the separation of (55)Fe and (89,90)Sr from liquid samples which consists of binding of Fe and Sr on Sr resin and separation from a number of elements by 6 mol/L HCl:3 mol/L HNO3 and their mutual separation by eluting of Sr with 4 mol/L HCl is established. The method enables efficient simultaneous separation (with high recovery) of (89,90)Sr and (55)Fe and in combination with Cerenkov counting rapid determination of (89,90)Sr.

Determination of uranium and thorium in complex samples using chromatographic separation, ICP-MS and spectrophotometric detection.

The paper describes a research of possible application of UTEVA and TRU resins and anion exchanger AMBERLITE CG-400 in nitrate form for the isolation of uranium and thorium from natural samples. The results of determination of distribution coefficient have shown that uranium and thorium bind on TRU and UTEVA resins from the solutions of nitric and hydrochloric acids, and binding strength increases proportionally to increase the concentration of acids. Uranium and thorium bind rather strongly to TRU resin from the nitric acid in concentration ranging from 0.5 to 5 mol L(-1), while large quantities of other ions present in the sample do not influence on the binding strength. Due to the difference in binding strength in HCl and HNO(3) respectively, uranium and thorium can be easily separated from each other on the columns filled with TRU resin. Furthermore, thorium binds to anion exchanger in nitrate form from alcohol solutions of nitric acid very strongly, while uranium does not, so they can be easily separated. Based on these results, we have created the procedures of preconcentration and separation of uranium and thorium from the soil, drinking water and seawater samples by using TRU and UTEVA resins and strong base anion exchangers in nitrate form. In one of the procedures, uranium and thorium bind directly from the samples of drinking water and seawater on the column filled with TRU resin from 0.5 mol L(-1) HNO(3) in a water sample. After binding, thorium is separated from uranium with 0.5 mol L(-1) HCl, and uranium is eluted with deionised water. By applying the described procedure, it is possible to achieve the concentration factor of over 1000 for the column filled with 1g of resin and splashed with 2L of the sample. Spectrophotometric determination with Arsenazo III, with this concentration factor results in detection limits below 1 microg L(-1) for uranium and thorium. In the second procedure, uranium and thorium are isolated from the soil samples with TRU resin, while they are separated from each other on the column filled with anion exchanger in alcohol solutions. Anion exchanger combined with alcohol solutions enables isolation of thorium from soil samples and its separation from a wide range of elements, as well as spectrophotometric determination, ICP-MS determination, and other determination techniques.