Berkay Camgöz

Biomonitoring of 210Po and 210Pb using lichens and mosses around coal-fired power plants in Western Turkey

Mosses and lichens are useful biological indicators of environmental contamination for a variety of metals and radionuclides of both natural and artificial origin. These plants lack a well-developed root system and rely largely on atmospheric deposition for nourishment. Therefore in the study, different lichens (Cladonia convoluta, Cladonia foliacea) and mosses (Homalothecium sericeum, Hypnum lacunosum, Hypnum cupressiforme, Tortella tortuosa, Didymodon acutus, Syntrichia ruralis, Syntrichia intermedia, Pterogonium graciale, Isothecium alopecuroides, Pleurochatae squarrosa) were collected around the Yatağan (Muğla), Soma (Manisa), Seyitömer - Tunçbilek (Kütahya) coal-fired power plants and investigated for potential use as biomonitors for (210)Po and (210)Pb deposition. While the activity concentrations of (210)Po and (210)Pb in lichens are in the ranges of 151 ± 7-593 ± 21 and 97 ± 5-364 ± 13 Bq kg(-1), for mosses the ranges for (210)Po and (210)Pb are 124 ± 5-1125 ± 38 and 113 ± 4-490 ± 17 Bq kg(-1), respectively. In the study, the moss samples were observed to accumulate more (210)Po and (210)Pb compared to lichens. While the most suitable biomonitor was a moss species (H. lacunosum) for Yatağan (Muğla), it was another moss species (S. intermedia) for Soma (Manisa) and Seyitömer - Tunçbilek (Kütahya) sites. (210)Po concentrations were found higher than (210)Pb concentrations at the all sampling stations.

Differential dose contributions on total dose distribution of 125I brachytherapy source

This work provides an improvement of the approach using Monte Carlo simulation for the Amersham Model 6711 (125)I brachytherapy seed source, which is well known by many theoretical and experimental studies. The source which has simple geometry was researched with respect to criteria of AAPM Tg-43 Report. The approach offered by this study involves determination of differential dose contributions that come from virtual partitions of a massive radioactive element of the studied source to a total dose at analytical calculation point. Some brachytherapy seeds contain multi-radioactive elements so the dose at any point is a total of separate doses from each element. It is momentous to know well the angular and radial dose distributions around the source that is located in cancerous tissue for clinical treatments. Interior geometry of a source is effective on dose characteristics of a distribution. Dose information of inner geometrical structure of a brachytherapy source cannot be acquired by experimental methods because of limits of physical material and geometry in the healthy tissue, so Monte Carlo simulation is a required approach of the study. EGSnrc Monte Carlo simulation software was used. In the design of a simulation, the radioactive source was divided into 10 rings, partitioned but not separate from each other. All differential sources were simulated for dose calculation, and the shape of dose distribution was determined comparatively distribution of a single-complete source. In this work anisotropy function was examined also mathematically.

Soil gas radon concentrations measurements in terms of great soil groups

In this study, soil gas radon concentrations were investigated according to locations, horizontal soil layers and great soil groups around Tuzla Fault, Seferihisar-İzmir. Great soil groups are a category that described the horizontal soil layers under soil classification system and distributions of radon concentration in the great soil groups are firstly determined by the present study. According to the obtained results, it has been showed that the radon concentrations in the Koluvial soil group are higher than the other soil groups in the region. Also significant differences on location in same great soil group were determined. The radon concentrations in the Koluvial soil groups were measured with respect to soil layers structures (A, B, C1, and C2). It has been observed that the values increase with depth of soil (C2>C1>B>A). The main reason may be due to the meteorological factors that have limited effect on radon escape from deep layers. Although fault lines pass thought the study area radon concentrations were varied location to location, layer to layer and great group to great group. The study shows that a detailed location description should be performed before soil radon measurements for earthquake predictions.

Investigation of dose distribution of TheraSeed 200 103Pd brachytherapy seed on coaxial cylindrical phantom shells using Monte Carlo simulation

ObjectiveIn this study, radial dosimetric characterization for specific internal geometry of seed source was determined. In this study, the separate contribution of radioactive components of the seed’s unlikely single radioactive rod on dose distribution was investigated using model seed TheraSeed 200 source at parallel shells in a water phantom.MethodsTheraSeed 200 brachytherapy seed was modeled using EGSnrc-MP Monte Carlo simulation code. Dose contributions of radioactive components inside the seed were calculated on coaxial shells with different radii in a water phantom. Dose calculation points on shells were determined as only spatial. The study’s spatial geometrical approach was considered.ResultsDose distributions of two radiation emitters were compared on plotted data. In 0°–90° rotation area, left emitter’s efficiency varied with distance. On shells with small radius, dose contribution (D1) of left emitter was weakly effective on total distribution; right emitter was the determinant factor on the total dose. By increasing shell radius, efficiency of two emitters comes close.ConclusionIt seems that geometrical specification of a seed is markedly effective on dose distribution. Differences between doses of two radioactive materials decrease rapidly beyond the seed borders. Consideration of this study can be applied for other seeds that have multiple radiation emitters to research the effects of their geometrical specification on dose distributions.

Gamma radiation shielding effectiveness of cellular woven fabrics

Lead-shielding products, such as lead aprons, are important materials for personal protection of physicians and patients from X-ray (gamma) radiation during medical operations. However, lead has environmental disadvantages such as high toxicity. The aim of this study was to manufacture an environmentally friendly and flexible textile-based radiation shielding material. In this work, 3/1 twill and some cellular woven fabrics were produced with conductive core yarns, and gamma radiation shielding effectiveness of these cellular woven fabrics were investigated and compared with that of the 3/1 twill woven fabric, which are commonly used as uniforms and were not studied previously in any other literature. The effects of weave on the structural characteristics of fabric such as the conductive weft yarn density, fabric thickness, and fullness were analyzed graphically and statistically. It is observed that with indenting and protruding, structure cellular woven fabrics performed better gamma radiation shielding performance than the 3/1 twill woven fabrics. The sample B1, woven with cellular weave 1, has the highest gamma radiation shielding effectiveness, thanks to the highest fabric thickness. In addition, the increase in the conductive core yarn density improved the gamma radiation shielding effectiveness of the woven fabrics.

A Monte Carlo evaluation for effects of probable dimensional uncertainties of low dose rate brachytherapy seeds on dose.

The aim of this study is to determine effects of size deviations of brachytherapy seeds on two dimensional dose distributions around the seed. Although many uncertainties are well known, the uncertainties which stem from geometric features of radiation sources are weakly considered and predicted. Neither TG-43 report which is not completely in common consensus, nor individual scientific MC and experimental studies include sufficient data for geometric uncertainties. Sizes of seed and its components can vary in a manufacturing deviation. This causes geometrical uncertainties, too. In this study, three seeds which have different geometrical properties were modeled using EGSnrc-Code Packages. Seeds were designed with all their details using the geometry package. 5% deviations of seed sizes were assumed. Modified seeds were derived from original seed by changing sizes by 5%. Normalizations of doses which were calculated from three kinds of brachytherapy seed and their derivations were found to be about 3%-20%. It was shown that manufacturing differences of brachytherapy seed cause considerable changes in dose distribution.

MONTE CARLO SYMULATION CHARACTERISTICS OF MODEL 6711 BRACHYTHERAPY SEED: EFFECTS OF ENERGY SPECTRUM AND PHANTOM DIMENSIONS

It is important to determine specified dose distributions of radioactive seed sources of brachytherapy in both phantom material and treated tissues. Dosimetric features and specific dose distribution functions of Model 6711 brachytherapy seed which is frequently used in prostate cancer treatments, have been given in literature. In the present study decay spectrum of radioactive material and variations of phantom dimensions which are foreseen to affect dosimetric specifications of the seed, were investigated and results were performed by Monte Carlo simulation. In simulation using separate decay spectrum and mono energy, differences were noted between interval of 1-68 percent. Also in calculations of phantom dimensions variations, deviations were not observed more than 0.1 percent by normalization to 1 as expected.