Ivana Vukanac

Internal exposure from building materials exhaling 222Rn and 220Rn as compared to external exposure due to their natural radioactivity content

The main scope of this paper is to point out the importance of introducing radon and thoron exhalation measurements from building materials in the regulating frame. Currently (2009), such a regulation of this kind of exposure is not explicitly included in the Serbian regulating network. To this end, this work reports concentration measurements of (226)Ra, (232)Th and (40)K and radon and thoron exhalation rates from building materials used in Serbia. Following detailed analysis, it was noticed that both internal exposures to radon and/or thoron exhaling from building materials may exceed external exposures to their precursors contained therein.

Intercomparison of methods for coincidence summing corrections in gamma-ray spectrometry—part II (volume sources)

The second part of an intercomparison of the coincidence summing correction methods is presented. This exercise concerned three volume sources, filled with liquid radioactive solution. The same experimental spectra, decay scheme and photon emission intensities were used by all the participants. The results were expressed as coincidence summing corrective factors for several energies of (152)Eu and (134)Cs, and different source-to-detector distances. They are presented and discussed.

Experimental determination of the HPGe spectrometer efficiency curve

A review of the calibration procedures of the semiconductor HPGe spectrometer is presented in this paper. Calibration standards were prepared using the standardized radioactive solution of the common monoenergetic radionuclides mixture and standardized multigamma (152)Eu solution. The matrix materials were spiked using the activated carbon, and homogenized mechanically or by suspension in C(2)H(5)OH. Experimentally determined efficiency curves were compared with those obtained by Monte Carlo simulation.

Vertical distribution of natural radionuclides in soil: assessment of external exposure of population in cultivated and undisturbed areas.

In the present work, naturally occurring radionuclides ²³⁸U, ²³²Th and ⁴⁰K were measured in soil samples from the cultivated and undisturbed areas in Rudovci, municipality of Lazarevac, Serbia. There were three profiles, each profile divided into four horizons, giving the twelve soil samples. The specific activity of ²³⁸U, ²³²Th and ⁴⁰K in soil and sediment samples was determined by gamma spectrometry using the HPGe semiconductor detector. Obtained activity concentrations ranged from 28.0 to 44.0 Bq/kg for ²³⁸U, from 59.4 to 71.4 Bq/kg for ²³²Th and from 335.0 to 517.0 Bq/kg for ⁴⁰K. The evaluation of the radiological hazards originated from ²³⁸U, ²³²Th and ⁴⁰K in the samples, the absorbed dose rate (D) and the annual effective dose rate (E), calculated in accordance with the UNSCEAR 2000 report, are presented in this paper.

Coincidence summing corrections for point and volume ¹⁵²Eu sources.

In this article, the X-ray and gamma-ray coincidence summing effect in (152)Eu is studied. Coincidence summing corrections and peak and total efficiencies of point and volume sources were determined using the direct matrices multiplication (DMM) method. The theoretically evaluated peak count rates were found to be in good agreement with the experimentally obtained values. Validation was performed by comparing the calculated efficiency curves and the corresponding correction factors with the results obtained using GESPECOR 4.2 software.

Novel method of measurement of radon exhalation from building materials.

In the era of the energy saving policy (i.e. more air tight doors and windows), the radon exhaled from building materials tends to increase its concentration in indoor air, which increases the importance of the measurement of radon exhalation from building materials. This manuscript presents a novel method of the radon exhalation measurement using only a HPGe detector or any other gamma spectrometer. Comparing it with the already used methods of radon exhalation measurements, this method provides the measurement of the emanation coefficient, the radon diffusion length and the radon exhalation rate, all within the same measurement, which additionally defines materials radon protective properties. Furthermore it does not necessitate additional equipment for radon or radon exhalation measurement, which simplifies measurement technique, and thus potentially facilitates introduction of legal obligation for radon exhalation determination in building materials.

Coincidence summing of X- and gamma rays of 75Se.

A study of coincidence summing of X- and gamma rays of (75)Se has been presented in this paper. The computation of the (75)Se spectra was performed by application of the previously published theory by Novković et al. The method enables the treatment of all possible single and sum peaks of (75)Se. The calculation gave the 419 decay path outcomes, resulting in 84 peak count rate equations and also the total count rate equation. By HPGe spectrometers with 15% and 18% relative efficiency, 20 and 30 peaks were recorded, respectively. Some simplification of the decay scheme was introduced and existing metastable level had to be treated separately. Nevertheless, the experimental values of the peak count rates were in good agreement with the theoretical evaluation.

A simple method for determination of natural and depleted uranium in surface soil samples.

A simple and efficient method for determination of uranium content in surface soil samples contaminated with depleted uranium, by gamma ray spectrometry is presented. The content of natural uranium and depleted uranium, as well as the activity ratio (235)U/(238)U of depleted uranium, were determined in contaminated surface soil samples by application of this method.

The direct measurement of 57Co activity by the sum-peak method

The direct measurement of the activities of (57)Co sources by application of the sum-peak method recently developed by Novković et al., is described in this paper. The comprehensive assessment of the uncertainty budget of the activity of the measured sources has been analyzed. The presented method is successfully tested using an HPGe spectrometer with efficiencies of 50%. The accuracy of this method is confirmed to be comparable with the commonly used methods of the activity measurement of (57)Co.

Determination of 210Pb by direct gamma-ray spectrometry, beta counting via 210Bi and alpha-particle spectrometry via 210Po in coal, slag and ash samples from thermal power plant

In order to compare three different techniques and estimate radiological impact, activity concentration of 210Pb in coal, slag and ash samples from thermal power plant “Nikola Tesla”, Serbia, were measured, and results are presented in this study. Determination of 210Pb was carried out in three ways: using HPGe gamma spectrometer and via in-growth of 210Po and 210Bi by alpha-particle spectrometry and proportional counting, respectively. The results obtained for three different techniques were compared. Statistical analysis and comparison of methods were carried out by combination of Z score and χ2 statistical tests. Tests results, as well as values of measured activities concentrations obtained by alpha and gamma spectrometry, showed that gamma spectrometry is a valid alternative to time-consuming alpha spectrometry for low level activity measurements of 210Pb. This remark is also valid even for gamma spectrometers with poor efficiency in low energy region.