Browsing by Author "Yildiz, Nergiz"

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Dating of the Sediment Accumulation Rate, Radioactive and Heavy Metal Pollution in the Van Lake
(Foundation Environmental Protection & Research-fepr, 2010) Yildiz, Nergiz; Yener, Gungor
The sediment accumulation rates and dating studies in the aquatic environments have significant importance on understanding of the relationship between human activities and aquatic medium. In this study, sediment accumulation rates and Pb-210 fluxes were calculated by using excess Pb-210 profile distributions and C.R.S. model together, and the dating of each layer was determined in three sediment cores where were sampled from east side of Van Lake. 210Pb activity was obtained from activities which was measured with alpha spectroscopy of the Po-210. Average sediment accumulation rates in the cores were found as 0.031 +/- 0.011, 0.046 +/- 0.021 and 0.077 +/- 0.051 g.cm(-2).y(-1). It was observed that sediment accumulation rates were found as significantly high levels in the areas where had high human activities and transportations from agricultural areas via stream erosion. In addition to, it was investigated the distributions of the Cs-137 isotop which is a fission product along two sediment core, and it was determined the concentrations of Cs-137 at certain levels which were spreaded to area because of the nuclear weapon tests conducted in 1954-1963 and Chernobyl nuclear plant accident in 1986. According to the general trend of Cs-137 distribution, it has pointed out that entry of Cs-137 to the lake from the environment continuous already now Furthermore, heavy metal concentrations (Cd, Cr, Cu, Pb) which was related to industrial, urban, agricultural wastes and geology of the basin were evaluated.
Investigation of Gamma Radiation Shielding Properties of Various Ores
(Pergamon-elsevier Science Ltd, 2015) Oto, Berna; Yildiz, Nergiz; Akdemir, Fatma; Kavaz, Esra
Mass attenuation coefficients (mu/p, cm(2)/g) for some pellet samples produced using barite, magnetite, limonite, hematite and serpentine ores at 81, 276, 302, 356, 383 key photons emitted from Ba-133 and 121, 244, 344, 444, 778 keV photons emitted from Eu-152 have been determined by using HPGe detector. Effective atomic numbers (Z(eff)) and electron densities (N-e) of the ores calculated in the selected energies.. The agreement of measured values of mu/p, Z(eff) and N-e with theoretical calculations is quite satisfactory. Mass attenuation coefficients were found to be highest for barite. The Z(eff) and N-e values for barite are maximum, for serpentine are minimum. Gamma ray energy absorption (EABF) and exposure buildup factors (EBF) were computed for ore samples using the five-parameter Geometric Progression (G-P) fitting method in the energy range 0.015-15 MeV for penetration depths up to 40 mean free path. Variations of EABF and EBF with incident photon energy and penetration depth were also investigated. It has been observed that among the selected ore samples, barite has lowest values for EABF and EBF in the intermediate energy region. Buildup of photons is more for serpentine. Exposure buildup factors (EBF) of given ores were compared with lead, steel-magnetite concrete (SM), concrete and bismuth borosilicate glass (BBS) with %20 mol Bi2O3. Barite is superior in terms of shielding properties among the other ore samples. The present study may be useful for radiation shielding applications. (C) 2015 Elsevier Ltd. All rights reserved.
Natural Radioactivity-Based Radiological Hazards in Soils of the Islands: a Case Study From Eastern Turkey
(Walter de Gruyter Gmbh, 2017) Oto, Berna; Yildiz, Nergiz; Seremet, Mehmet
A comprehensive work was carried out to investigate natural radionuclides of U-238, Th-232 and K-40 in 73 soil samples collected from islands of Adir, Carpanak and Akdamar on the Van Lake (Turkey) located at Eastern Turkey. Radioactivity concentrations of these radionuclides were measured by using a gamma spectrometer with NaI(Tl) detector to be from 4.11 to 77.1 Bq/kg, from 6.0 to 70.0 Bq/kg and from 133.05 to 749.77 Bq/kg with the mean values of 33.33 Bq/kg, 36.68 Bq/kg and 478.19 Bq/kg, respectively. In addition, the absorbed gamma dose rate in air (D) and annual effective dose equivalent (AED) were found to be 57.5 nGy/h and 70.5 mu Sv/year, respectively. We have shown that our results might be related to the geological formation type. The results were compared with some published ones in Turkey and the World, which were found within acceptable limits.
Neutron Shielding Qualities and Gamma Ray Buildup Factors of Concretes Containing Limonite Ore
(Elsevier Science Sa, 2015) Oto, Berna; Yildiz, Nergiz; Korkut, Turgay; Kavaz, Esra
Neutron dose transmissions for fast neutrons produced by 5.486 MeV alpha particles on beryllium are measured in concrete samples with and without limonite ore to investigate their neutron shielding qualities. Using measured values, macroscopic removal cross-sections (Sigma(R), cm(-1)) have been determined experimentally and also Sigma(R)values have been calculated theoretically using the elemental composition of the concrete mixes. The best neutron shielding property of concrete sample containing 100% limonite ore (FCL: fine and coarse limonite) was found. Additionally, energy absorption buildup factor (EABF) and exposure buildup factor (EBF) of concrete sample were calculated using the five-parameter Geometric Progression (G-P) approximation in the energy range of 0.015-15 MeV for penetration depths up to 40 mean free path (mfp). The incident photon energy and penetration depth dependence of buildup factors were examined. Finally, we observed that concrete samples have maximum values of buildup factors in the intermediate energy region around 0.1-0.3 MeV. FCL has the minimum values of both of the buildup factors. FCL has the excellent gamma shielding properties compared to the concrete samples. (C) 2015 Elsevier B.V. All rights reserved.