Sürdürülebilir Kalkınma Amaçları
Yayınlar
- MakaleAçık Erişim2026Scopus SJRQ2Long-term decline of Chernobyl-derived 137Cs in mosses and lichens from the Eastern Black Sea region of Türkiye
Çevik, Ugur; Çelik, Necati; Uzun, Kubra K.; Çelik, Ahmet; Koz, Bahadir; Özen, Songul A.; Yesilkanat, Cafer M.; Hacisalihoglu, Aylin; Özkalayci, Fatih; Kaya, Selim
This study presents the third consecutive assessment of 13 Cs activity concentrations in the same 50 moss (7 species) and lichen (2 species) sampling points in Ordu province, T & uuml;rkiye, one of the most heavily contaminated areas following the Chernobyl accident. Samples were collected from exactly the same locations used in the 1997 and 2007 studies and analyzed by high-resolution gamma spectrometry. In 2025, detectable 13 Cs was found in 14 of 30 moss sites (47%) and 3 of 20 lichen sites (15%). For samples below the minimum detectable activity (MDA), a value of MDA/2 (0.93 Bq kg-1) was substituted for lichens, while moss samples below the MDA were excluded from regression. The ecological half-life (Teco) for the 2007-2025 period was 4.38 +/- 1.05 years for mosses and 4.18 +/- 0.61 years for lichens. For mosses, this is nearly identical to the 1997-2007 mean (4.4 years), while for lichens it decreased from 5.6 to 4.18 years, suggesting a slight acceleration in environmental removal. All Teco values remain far shorter than the physical half-life of 13 Cs (30 years), confirming that environmental removal processes dominate over radioactive decay. Residual 13 Cs is concentrated in higher-altitude areas, reflecting the original deposition pattern and slower removal in cooler, more humid microenvironments. Nearly 39 years after the accident, the radiological risk posed by residual trace levels is negligible. This 28-year dataset provides one of the longest continuous records of 13 Cs in epiphytic bioindicators and serves as a valuable baseline for future contamination events.
- MakaleAçık Erişim2026Scopus SJRQ2A combined Monte Carlo, analytical, and experimental study of true coincidence summing correction factors for 152Eu
Çelik, Necati; Ali, Ahmed H.; Apaydin, Gokhan; Çevik, Ugur; Açikel, Selami
The radionuclide 152Eu presents a significant challenge in gamma-ray spectrometry due to its complex decay scheme and significant true coincidence summing (TCS) effects, especially in close-measurement geometries. This study presents a comprehensive investigation into TCS correction factors for the principal gamma-ray lines of 152Eu using tripartite methodology: a custom Monte Carlo (MC) simulation based on the EGS4 system, an established analytical method, and direct experimental measurements. The MC simulation explicitly models the complete decay process, including branching ratios, gamma emissions, internal conversion, and subsequent X-ray emissions for both decay branches (beta-minus to 152Gd and EC to 152Sm). Experimentally, correction factors were derived using a well-characterized point source measured at multiple distances with a coaxial HPGe detector. The analytical, method based on probabilistic analysis of the decay scheme, served as an examination. Results demonstrate that the analytical method underestimated the TCS correction factors, particularly for low-energy lines such as 121.78 keV, where it predicted a mere 0.78 % correction compared to 25.5 and 23.5 % from MC and experiment, respectively. This discrepancy is attributed to the analytical method's neglect of gamma-X ray coincidences and the internal conversion effects. In contrast, the MC simulation showed remarkable agreement with experimental results across all energies, validating its capability to accurately model the full complexity of TCS effects. The study concludes that while analytical methods offer rapid estimates, MC simulations, especially when experimentally validated, are essential for achieving metrological accuracy in the gamma-ray spectrometric analysis of complex radionuclides like 152Eu.
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İncele - MakaleYalnız künye2013Scopus SJRQ2Assessment of Radiological Levels at Schools in Trabzon, Turkey
Çevik, Ugur; Çelik, Ahmet; Çelik, Necati; Özkalayci, Fatih; Akbulut, Songul
In this study, a survey on environmental radioactivity in 16 high schools located in north eastern region of Turkey (the black sea region, province of Trabzon) was carried out. Indoor air radon (Rn-222) concentrations were measured in spring and autumn 2008 seasons using LR115 solid state nuclear track detectors and gamma radioactivity levels were measured using an HPGe gamma ray detector. It was seen that mean radon activity concentrations in schools ranged from 31 to 157 Bq/m(3) for spring season and from 38 to 114 Bq/m(3) for autumn season. The mean gamma activity concentrations in located areas of schools are between 18-52, 21-59, 11-97 and 265-759 Bq/kg for Ra-226, Th-232, Cs-137 and K-40, respectively. The annual effective doses of students and staff received due to radon and locations' gamma radioactivity levels are calculated.
AtıfScopus5WoS5OpenAlex8İncele - MakaleYalnız künye2012Scopus SJRQ2Effect of detector collimation on the measured mass attenuation coefficients of some elements for 59.5-661.6 keV gamma-rays
Çelik, Necati; Çevik, Ugur; Çelik, Ahmet
Mass attenuation coefficients were determined experimentally for Sc, Ni and W for gamma energies of 59.5, 122, 276, 302, 356, 383 and 662 keV for different detector collimator diameters ranging from 2 to 10 mm. The aim was to investigate the quantitative analysis of detector collimator diameter effect on measured mass attenuation coefficients. It was found that measured mass attenuation coefficients decrease systematically with the increasing collimator diameter. The relative difference was found to be up to around 3% in some cases. The observed decrease in mass attenuation coefficients was attributed to the detection of elastic and inelastic scattered photons from the absorber. In elastic scattering process the photons change in direction but not in energy and get counted under the full energy peak if they reach the detector. In inelastic scattering however, both direction and energy of the scattered photons change. It was seen that most of the inelastic scattered photons also get counted by the detection system since they lose an amount of energy lower than the energy resolution of the detector. It is understood from the present results that it is essential to take into account the experimental geometry when reporting mass attenuation coefficients.
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