Browsing by Subject "extraction chromatography"
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(2021)Scandium-44 is a medically interesting positron and gamma emitting radionuclide with possible applications in molecular imaging. It is commonly produced with the use of a cyclotron in a calcium or sometimes a titanium based irradiation target. As the radiopharmaceutical use of scandium radionuclides commonly requires chelation, scandium needs to be separated from the target matrix. This is most often carried out either via extraction chromatography using a suitable solid phase or through precipitation-filtration. In this work, scandium-44 along with other scandium radionuclides was produced using cyclotron irradiation with 10 MeV protons and a solid, natural isotopic abundance calcium carbonate or calcium metal target. Scandium was separated from the irradiated targets using four different chromatographic materials and a precipitation method. Scandium-44 was produced in kilo- and megabecquerel amounts with an average saturation yield of 47 MBq/μA. The achieved separation yields in a single elution ranged from 28 ± 11 % to 70 ± 20 % with the best performing extraction material being UTEVA resin.
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(2022)Measurement of alpha-active actinides requires separation from other alpha emitting radionuclides. A method of actinide separation was needed for the primary coolant water of Loviisa Nuclear Power Plant. A method published by Eichrom Ltd was chosen to be evaluated, this method utilises a vacuum box with stacked TEVA / TRU columns which speeds up and eases the analysis process. The method can be used to separate americium, curium, plutonium and uranium from a water samples and it gave excellent results both with reference samples and primary coolant water. The separation was also tested with other more difficult matrices: ion exchange resins, surface swipes, aerosol filters and process waste waters. Pretreatment methods for these matrices were assessed and tested to reduce the sample to a soluble form that could be loaded to the separation system. DGA resin based methods were tested for both gross-alpha and nuclide specific analyses. The gross-alpha method with DGA was fast, efficient and reliant. Gross alpha counting samples could be produced within hours and element fraction samples could be produced in 1 - 2 days. This combined with the good recoveries of all fractions meant shorter counting times to reach the minimal detectable activities (MDAs) required. The literature review part takes a look into recent interesting topics related to actinide separation and analysis from similar matrices discussed in the the experimental section. Different extraction chromatography resins are discussed.
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(2023)The study consists of two parts: examining the accumulation of americium and plutonium to human ribs, and the accumulation to murine osteoblasts. In the cellular studies stable europium was used as an actinide analogue. After removing the organic material from the bones, americium and plutonium were separated from the dissolved bones by using extraction chromatographic methods. DOWEX, U/TEVA, and TRU resins were used to separate plutonium and americium from impurities. The sample activities were measured using alpha spectrometry. On average, 23.03 mBq/kg of plutonium-238, 12.58 mBq/kg of plutonium-239,240 and 9.81 mBq/kg of americium-241 were measured in the bone samples. The activity concentrations are calculated using the wet weight of the bone. Murine preosteobasts (MC3T3-E1) were mineralized for 12 days. The mineral was subsequently collected for SEM/EDS analysis. Non-mineralized cell fractions were collected for a fractioning study, where the cell internalized europium, membrane bound europium and extracellular europium fractions were collected and measured with MP-AES and ICP-MS. The used europium concentrations were below minimum detectable activity of the MP-AES, but measuring the samples on the ICP-MS showed that the percentage of the internalized europium increases at higher europium concentrations in cell culture media. At 0.2 μM europium concentration, on average, 28.6% of the europium was inside the cells and 71.4% in the media, while at 2.0 μM europium concentration, 30.8% of the europium was inside the cells and 68.5% in the media.
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(2024)Radioactive strontium is a fission product of plutonium and uranium often found in high concentrations in spent nuclear fuel and radioactive waste. Strontium-90 was spread worldwide through nuclear weapons testing in the 1950s and 1960s. Sharing similar properties with calcium, it poses significant health risks when released into the environment, as it can accumulate in bone tissue and teeth, where it continues to radiate surrounding tissues. Therefore, efficient, and rapid monitoring methods for routine analysis of radioactive strontium from nuclear sites and during radiological emergencies are crucial. The aim of this master’s thesis was to validate a strontium-89/90 separation method for the Radiation and Nuclear Safety Authority (STUK) for their routine analysis of emission samples from the Olkiluoto and Loviisa Nuclear Power Plants. Previously, STUK has utilized proportional counting for their strontium analysis. However, this method is time-consuming, involving the ingrowth of the daughter nuclide of strontium-90, yttrium-90, which can take up to 18 days. The strontium determination method used by STUK was modified so the samples could be measured with Hidex 300 SL liquid scintillation counter, equipped with the triple-to-double coincidence ratio (TDCR) liquid scintillation counting technique. Using the liquid scintillation counter makes it theoretically possible to skip the yttrium-90 in-growth phase by measuring strontium-89 immediately after chemical separation using Cherenkov counting, followed by measuring strontium-90 by liquid scintillation counting. At the end of the experimental part of the thesis, considerations for further development of the method included ideas for shortening the sample measurement time, such as increasing the volume of the Cherenkov sample, or the volume of the discharge water used for the analysis. These adjustments would enable faster achievement of the 0.2 Bq/l minimum detectable activity (MDA) and allow for the addition of the scintillation cocktail on the same day, minimizing the growth of yttrium-90. Although the final validation of the method was not completed during this study, STUK gained data and ideas for the continued development of their strontium-89/90 analysis method.
Now showing items 1-4 of 4