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    Assessment of the detection efficiency calibration of high-resolution gamma-ray spectrometers by EGSnrc and MCNP6.2 Monte Carlo codes
    (Pergamon-Elsevier Science Ltd, 2023) Sayin, Sefa; Seferinoglu, Meryem; Yeltepe, Emin; Cetin, Berkay; Lule, Senem Senturk
    Determination of the activity content of radionuclides with high accuracy and precision with gamma-ray spectrometry is strongly based on the detection efficiency calibration of the detector. The detector efficiency calibration is determined with standard reference sources and/or Monte Carlo codes. The current study provides methodology that can be used to generate efficiency curve with simulations instead of experiments. As a result, the need for additional experiments can be reduced. The implementation of a specific script written on EGSnrc Monte Carlo code was investigated to calculate the detection efficiency with high-level accuracy for high-purity germanium (HPGe) spectrometry. For this purpose, two HPGe detectors (ORTEC and PGT) used routinely in the activity measurement of gamma emitting radionuclides were modelled with EGSnrc code to obtain detection efficiencies for 40-2000 keV energy range. The detector models were benchmarked against MCNP6.2 Monte Carlo code with a hypothetical source geometry. The code-to-code comparison between EGSnrc and MCNP6.2 codes indicted that the codes can be used to generate a reliable detection efficiency curve. The benchmark results showed that median arithmetic deviations of the efficiencies of ORTEC and PGT detectors are found as 0.88% and 1.69%, respectively. The experimental studies were performed with 22Na, 57Co, 60Co, 137Cs, and 241Am standard disc sources for the ORTEC detector and with in-house prepared 152Eu sandwich-type source for the PGT detector. The sources were counted in the energy range of 59.5-1408 keV. The efficiency values from simulations were used in the calculation of the activities of the aforementioned gamma sources with a mathematical formula and resulting measured activity values were compared with reference activity values given in the certificates. In addition, the applicability of spreadsheet approach that is usually used to determine the combined standard uncertainty for alpha-particle spectrometry was investigated for gamma-ray spectrometry. The performance of the recommended procedure was scored in terms of relative bias, z-score, u-test, trueness, and precision. The activity results obtained with simulated efficiencies showed good agreement with certified values.
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    Öğe
    Mineral and Chemical Characterization of Magnetic and Non - Magnetic Products Obtained from Dry Magnetic Enrichment of Lignite Coals
    (Gazi Univ, 2022) Seferinoglu, Meryem; Duzenli, Derya
    The mineral and chemical composition of magnetic (tailing fraction) and non - magnetic (clean coal fraction) products from the dry magnetic separation of coal samples with high ash and sulfur contents obtained from Canakkale Can lignite (S1) and Manisa Kula Pabuclu lignite (S2) were investigated in this study. The feasibility of the dry magnetic separation technique for the separation of the minerals from the coal matrix was identified as the function of coal types and particle sizes. The separation technique depends on coal fragments being weakly diamagnetic, while most of the minerals present in the coal are weakly to moderately paramagnetic. Three particle sizes (coarse-, medium-, and fine-sized) of feed lignite and their magnetic and non-magnetic fractions were separated and characterized. The influence of coal type on the magnetic separation efficiency was determined by the recovery of tailing fractions obtained from S1 and S2 lignites. The particle sizes of S1 lignite were quite lower than S2 lignite. When the fine-sized lignite samples from S1 and S2 were used, the recovery of tailing fractions was the highest compared to other sizes. The mineral compositions of S2 lignite include typically mica, smectite (clay mineral), gypsum, kaolinite (clay mineral), pyrite, quartz, and plagioclase. The results showed that the Permroll High-Intensity Magnetic Separation method for high calorific value and low ash content at the medium-sized particle was more efficient for the S2 lignite sample than the S1 lignite sample.
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    Öğe
    Radiochemical Procedure for Measurement Specific Activities of Uranium Isotopes in Asphaltite Bioleaching Liquor by Alpha-Particle Spectrometry
    (Gazi Üniversitesi, 2022) Seferinoglu, Meryem
    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.