Environmental evaluation of natural radioactivity in soil near a lignite-burning power plant in Turkey.

Natural radionuclides are released into the environment together with fly ash from the coal-burning power plant and cause an increase in the natural radioactivity in environmental samples. The study concerns to the evaluation the influence of Kangal lignite-burning power plant (LBPP) with a power of 457 MWe, which has been in operation since 1989, on natural radionuclide a concentration in surface soil samples around it. Activity concentrations of natural radionuclides (226Ra, 232Th, 40K and 222Rn) in the soil samples, and emanation coefficient (EC) and mass (ERM) and surface (ERS) exhalation rate of radon were determined by using a gamma-ray spectrometer with an HPGe detector. The average values of 226Ra, 232Th, 40K and 222Rn, EC, ERM and ERS were found as 37±5, 17±3, 222±30Bqkg-1 and 9±1kBqm-3, 12%, 12.1 µBq kg-1 s-1 and 7.1mBqm-2 s-1, respectively. Absorbed gamma dose rate in outdoor air and the corresponding effective dose rate from external exposure and excess lifetime cancer risk were estimated to evaluate radiological hazards for human population. The results revealed that the Kangal LBPP has caused a small increment in 226Ra concentration in the studied area. No influence was observed for 232Th and 40K.

Determination of dosimetric properties of MgO doped natural amethyst samples.

In this paper, the thermoluminescence (TL) dosimetric characteristics of MgO doped natural amethyst samples (Mg-NA) are presented. The morphologies and chemical structures of the powder form samples were identified using XRD, FTIR, SEM, SEM mapping and EDX. Comparison of the TL intensities showed that 10wt% Mg-NA was nearly 150 times more sensitive than undoped amethyst and the main dosimetric properties proved that 10wt% Mg-NA may be a promising phosphor for clinical and radiotherapy purposes.

Investigation of the activity level and radiological impacts of naturally occurring radionuclides in blast furnace slag.

The activity level and possible radiological impacts of naturally occurring radionuclides on the health of workers and members of the public, as a result of utilisation of blast furnace slag (BFS) samples as a substitute for aggregate in road construction were investigated by using a gamma-ray spectrometer and potential exposure scenarios given in Radiation Protection 122. The mean activity concentrations of the (226)Ra, (232)Th and (40)K in BFS samples were found to be 152.4, 54.9 and 183.1 Bq kg(-1), respectively. These values are compared with typical values measured in BFS samples from the European Union countries, which are 270, 70 and 240 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The values of radium equivalent activity index calculated for BFS samples were within the recommended safety limits. The highest total annual effective doses evaluated as 0.9 and 0.4 mSv y(-1) for members of the public and workers, respectively, were lower than the annual limit of 1 mSv y(-1).

A survey of distribution of terrestrial radionuclides in surface soil samples in and around the Osmaniyeprovince, Turkey.

The purpose of this survey was to determine the distribution of terrestrial radionuclides ((238)U, (232)Th and (40)K) in surface soil samples collected from different locations in and around Osmaniye and assess the radiological implications of outdoor external exposure. The activity concentrations of (238)U, (232)Th and (40)K in soil samples ranged from 2.6 to 38.1 Bq kg(-1) with a mean of 10.4±0.7 Bq kg(-1), 3.7-40.5 Bq kg(-1) with a mean of 12.2±0.7 Bq kg(-1) and 30.0-639.7 Bq kg(-1) with a mean of 243.4±12.8 Bq kg(-1), respectively. The concentrations of these radionuclides, presented in this article, were compared with those obtained from similar studies related to Turkey reported in the literature as well as earth's crust average values. The results of the activity concentrations were used to assess the external absorbed gamma dose rate (GDR) in outdoor air and the annual effective dose (AED). The outdoor absorbed GDRs fluctuate from 5.2 to 53.6 nGy h(-1) with a mean of 22.4±9.5. The corresponding mean AED is found to be 0.03 mSv.

Photon beam audits for radiation therapy clinics: a pilot mailed dosemeter study in Turkey.

A thermoluminescent dosemeter (TLD) mailed dose audit programme was performed at five radiotherapy clinics in Turkey. The intercomparison was organised by the University of Wisconsin Radiation Calibration Laboratory (UWRCL), which was responsible for the technical aspects of the study including reference irradiations, distribution, collection and evaluation. The purpose of these audits was to perform an independent dosimetry check of the radiation beams using TLDs sent by mail. Acrylic holders, each with five TLD chips inside and instructions for their irradiation to specified absorbed dose to water of 2 Gy, were mailed to all participating clinics. TLD irradiations were performed with a 6 MV linear accelerator and (60)Co photon beams. The deviations from the TL readings of UWRCL were calculated. Discrepancies inside the limits of ±5 % between the participant-stated dose, and the TLD-measured dose were considered acceptable. One out of 10 beams checked was outside this limit, with a difference of 5.8 %.

SU-E-I-08: KV XVI Cone Beam-CT Dose Measurement Using Gafchromic XRQA2 Film.

PURPOSE: To study the effect of different filters on the dose response curves of the Gafchromic XRQA2 film. To measure the kV XVI cone-beam CT (CBCT) surface dose received during 3D and 4D imaging protocols in three body regions (head and neck, chest and pelvis). METHODS: GafChromic XR- QA2 film (International Specialty Products, Wayne, NJ) dose response curves were generated for three irradiation settings: 100 kVp S20/F0; 120 kVp S20/F0 and 120 kVp S20/F1(F1 is a Bowtie filter). Film pieces were irradiated in air by the X-ray Volume Imager (XVI) mounted on the Elekta Synergy linear accelerator (Elekta, Crawley, UK) and their responses were correlated to air kerma measurements. To measure the CBCT surface dose, film pieces were taped on the surface of a male Alderson Rando Phantom (Alderson Research Laboratories, Inc., Long Island City, New York) at four different places (Anterior, Posterior, Right Lateral, Left Lateral). RESULTS: The dose response curves of XRQA2 film generated with F1 and F0 filters were found to differ by 5 to 7% when the air kerma changed between 2 and 5 cGy. This was less than the observed difference (more than 15%, especially at low air kerma) in the dose response curves when different energies (100 and 120 kVp) and same filter were used. Surface dose ranged between 0.02 cGy and 4.99 cGy. The lowest average surface dose (0.05 cGy) was observed when the fast head and neck protocol was used, whilst the highest average surface dose (3.06 cGy) was noticed when the chest m2 0 protocol was used. CONCLUSIONS: Filters seem to have less effect on the dose response of the film compared with energy. Gafchromic XRQA2 film was used successfully to measure the XVI CBCT surface dose. The dose was found to vary from one imaging protocol to another, with 4D protocols not necessarily delivering more doses.

SU-E-J-50: Measurement of the HVL Value for the 120keV Photon Beam of the X-Ray Volume Imager (XVI) Using Ionization Chamber, Gafchromic Film XRQA2 and Diode.

PURPOSE: The value of Half Value Layer (HVL) is essential in quantifying the ability of an x-ray beam to penetrate the material being studied. This paper examines the use of three different types of detectors for measuring HVL of the 120keV photon beam of the X-ray Volume Imager (XVI) cone beam CT system mounted on the Elekta Synergy (Crawley, UK) Linac: ionization chamber, Gafchromic film and diode. The effects of collimator diameters are presented and the chamber tip and chamber horizontalmethods are compared to investigate the source of variations in the measurement of HVL. METHODS: The measurements are done in free airboth using an ionization chamber calibrated for absolute dosimetry [University of Wisconsin Accredited Dosimetry Laboratory] and the Gafchromic film dosimeters [XR-QA2 (International Specialty Products, Wayne, NJ)]. The beam is collimated to the size of the detector to measure the exposed dose. The different thicknesses of the aluminum attenuators are added to beam to measure individual doses every time and repeated until the dose fell to below 50% of the initial unattenuated value. Dose measurements with a semiconductor diode detector [Barracuda MPD (RTI Electronics AB, NJ)] is also carried out. We plotted all results on a semi-log graph to find HVL value. RESULTS: When the measurements are made using ionization chamber with different collimator diameters we obtained 1.6% difference in HVL values. Measurements with chamber tip and horizontal methods agree with each other to within approximately 1.6% percentage difference. The percentage difference of the HVL values measured using the diode and ionization chamber is about 6.4% and that of using Gafchromic film and ionization chamber is about 8% percent. CONCLUSIONS: Gafchromic films and diodes can be used to measure HVL value of 120 keV photon beams. Recommendations for consistency in HVL measurements are provided.