N. Celik

Determination of indoor radon and soil radioactivity levels in Giresun, Turkey

Indoor radon survey and gamma activity measurements in soil samples were carried out in the Giresun province (Northeastern Turkey). The result of analysis of variance showed a relationship between indoor radon and radium content in soil (R(2)=0.54). It was found that indoor radon activity concentration ranged from 52 to 360 Bq m(-3) with an average value of 130 Bq m(-3). A model built by BEIR VI was used to predict the number of lung cancer deaths due to indoor radon exposure. It was found that indoor radon is responsible for 8% of all lung cancer deaths occurring in this province. (137)Cs activity concentration was measured 21 years after the Chernobyl accident. The results showed that (137)Cs activity concentration ranged from 41 to 1304 Bq kg(-1) with an average value of 307 Bq kg(-1). The indoor radon results and the geology of the studied area were discussed. Annual effective doses to the both radionuclides of natural origin and (137)Cs were estimated.

Radiation dose estimation and mass attenuation coefficients of cement samples used in Turkey.

Different cement samples commonly used in building construction in Turkey have been analyzed for natural radioactivity using gamma-ray spectrometry. The mean activity concentrations observed in the cement samples were 52, 40 and 324 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The measured activity concentrations for these radionuclides were compared with the reported data of other countries and world average limits. The radiological hazard parameters such as radium equivalent activities (Ra(eq)), gamma index (I(gamma)) and alpha index (I(alpha)) indices as well as terrestrial absorbed dose and annual effective dose rate were calculated and compared with the international data. The Ra(eq) values of cement are lower than the limit of 370 Bq kg(-1), equivalent to a gamma dose of 1.5 mSv y(-1). Moreover, the mass attenuation coefficients were determined experimentally and calculated theoretically using XCOM in some cement samples. Also, chemical compositions analyses of the cement samples were investigated.

Natural and artificial radioactivity measurements in Eastern Black Sea region of Turkey.

In the present work, naturally occurring radionuclides of (226)Ra, (232)Th and (40)K were measured in soil samples collected from the Eastern Black Sea region of Turkey. It was found that the activity concentrations ranged from 12 to 120Bqkg(-1) for (226)Ra, from 13 to 121Bqkg(-1) for (232)Th and from 204 to 1295Bqkg(-1) for (40)K. Besides naturally occurring radionuclides, (137)Cs activity concentration was measured in soil, lichen and moss samples and it was found that (137)Cs activity concentration ranged from 27 to 775Bqkg(-1) with for soil, from 29 to 879Bqkg(-1) for lichen and from 67 to 1396Bqkg(-1) for moss samples. Annual effective doses due to the naturally occurring radionuclides and (137)Cs were estimated. Ecological half-lives of (137)Cs in lichen and moss species were estimated. The decrease of the activity concentrations in the present measurements (2007) relative to those in 1993 indicated ecological half-lives between 1.36 and 2.96 years for lichen and between 1.35 and 2.85 years for moss species.

Assessment of natural radioactivity of sand used in Turkey

The natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K in sand samples used as building materials in Turkey was measured by gamma spectrometry. The measured activity in the sand samples ranged from 17 to 97 Bq kg(-1), 10 to 133 Bq kg(-1) and 116 to 955 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The concentrations of these natural radionuclides were compared with the reported data for other countries. The radium equivalent activity (Ra(eq)), the external hazard index (H(ex)), the internal hazard index (H(in)), the indoor absorbed dose rate in air and the annual effective dose rate were evaluated to assess the radiation hazard for people living in dwellings made of the materials studied. The Ra(eq) values of sand samples are lower than the limit of 370 Bq kg(-1), equivalent to a gamma dose of 1.5 mSv yr(-1). This study shows that the measured sand samples do not pose any significant source of radiation hazard and are safe for use in building materials. Moreover, the experimental mass attenuation coefficients (mu/rho) of seven different sand samples were determined in the energy range 80-1332 keV photons by using the gamma ray transmission method. Experimental values of mass attenuation coefficient were compared with theoretical values obtained using the program XCOM. The calculated values and the experimental results of this work and the other results in the literature are found to be in good agreement. Chemical and structural analyses (XRD) of the sand samples were also undertaken.

Ecological half-life of 137Cs in mosses and lichens in the Ordu province, Turkey by Cevik and Celik

Twenty-one years after the Chernobyl accident, lichen and moss samples were collected from the Ordu province, which was already chosen for a related study some years ago. It was observed that 137Cs activity concentration ranged from 31 to 469 Bq kg(-1) in the moss and from 132 to 1508 Bq kg(-1) in the lichen samples. The decrease of the activity concentrations in the present measurements (2007) relative to those in 1997 (over a period of 10 y) indicated ecological half-lives between 1.8 and 10.4 y for the moss and between 2.1 and 13.7 y for the lichen samples. It was observed that 137Cs was still eminent in the area studied. Moreover, 40K activity concentrations and K element concentrations were measured and their relationships were discussed.

Gamma ray concentrations in soil and building materials in Ordu, Turkey

The city of Ordu is in the Eastern Black Sea region of Turkey with a population of approximately 716,000. Presently there is no information available about radioactivity levels in Ordu soil and building materials. For this reason, activity concentrations in soil and building material samples collected from different sampling stations in Ordu were measured using gamma-ray spectrometry. In addition to natural radionuclides, 137Cs was detected in the soil samples and the possible origins of this radionuclide were discussed. The activity concentrations of soil samples ranged from 13.4 to 151.7 Bq kg−1 for 226Ra, from 14.3 to 98.5 Bq kg−1 for 232Th, from 303 to 1107 Bq kg−1 for 40K and from 67.4 to 275.3 Bq kg−1 for 137Cs. The mean concentrations of 226Ra, 232Th and 40K in selected building materials were 34.5, 26.9 and 378.4 Bq kg−1, respectively. The results were compared with the reported data from different works. From the measurements, radium equivalent activity, terrestrial absorbed dose, annual effective dose rate, external hazard indices and internal hazard indices were calculated, and were found to be within the acceptable limits. The data presented in this study might be useful as a baseline data for future estimations of a populations exposure.

Radioactivity and heavy metal levels in hazelnut growing in the Eastern Black Sea Region of Turkey

The Eastern Black Sea Region of Turkey is one of the main hazelnut producers in Turkey and in the world. Since this region was contaminated by the Chernobyl accident in 1986, a comprehensive study was planned and carried out to determine the radioactivity level in hazelnut growing region. The dose due to consumption of hazelnut by the public was estimated and it was shown that this dose imposes no threat to human health. In addition, heavy metal analysis was performed in the samples and the amount of Cr, Mn, Fe, Ni, Cu, Zn, and Pb were also detected. The results showed that the concentrations of heavy metal are below the daily intake recommended by the international organizations.

137Cs and 40K activity concentration measurements and elemental analysis in lichen samples collected from the Giresun province of northeastern Turkey

About 21 years after the Chernobyl accident, 137Cs and 40K activity concentration measurements using gamma-ray spectroscopy and elemental analysis using energy dispersive X-ray spectroscopy were performed in five different lichen species collected from the Giresun province of northeastern Turkey. Being a symbiosis of algae and fungi, lichens are mostly used for environmental measurements since the fungal partner is responsible for the uptake of necessary nutrients or harmful substances, such as heavy metals of radionuclides. The gamma activity results showed that 137Cs, an artificial radionuclide released from the Chernobyl power plant accident, is still eminent in the environment of the province. The mean activity concentrations of 137Cs and 40K ranged from 24 to 254 with the mean value of 102 Bq kg−1 and from 345 to 2103 with the mean value of 1143 Bq kg−1 in dry weight. The results of the elemental analyses showed potassium, calcium, titanium, iron, tin, and barium in different concentrations.

Monte Carlo determination of inhomogeneity effect on gamma-ray detection efficiency in soil samples

Inhomogeneity effect on full energy peak (FEP) efficiency in a soil sample was determined using the Monte Carlo simulation technique. The dependence of the FEP efficiency on the homogeneity in the soil was obtained for some particular photon energies ranging from 60 keV to 2 MeV and, as a result, the corresponding correction factors were obtained. This effect was more significant at lower energies and for higher inhomogeneity rates.