Jovana Nikolov

Public exposure to radon in drinking water in Serbia.

Radon is the main source of natural radiation that is received by population. The results of radon activity measurements in water from public drinking fountain, from bottled drinking water and from tap water in the city of Novi Sad, Serbia, are presented in this paper. The measurements were performed by RAD 7 radon detector manufactured by DURRIDGE COMPANY Inc. The corrected value of radon concentration in one sample exceeded the European Commission recommendation reference level for radon in drinking water of 100 Bql(-1). In order to make the correlation between radon and radium concentrations in the tap water and in the water from public drinking fountain, the gamma-spectrometric measurements were performed. The results of (222)Rn activity concentration measurements from soil in the city of Novi Sad using RAD 7 detector are presented.

Airborne radioiodine in northern Serbia from Fukushima

The results obtained with the monitoring system set up to assess the impact of the Fukushima accident on the environment of Vojvodina (Northern Province of Serbia) are presented and discussed. Aerosol, rain, fresh milk and spinach samples were collected daily in the weeks following the accident. In the aerosol samples, (131)I activity concentrations of several mBq m(-3) were measured, while in rain, milk and spinach samples, (131)I levels had values in a range of (0.3-1.7) Bq kg(-1). These are the first results on the impact of the Fukushima accident on the Pannonian basin region. Our results are compared with the reported values from other parts of the world.

Natural radionuclides in drinking waters in Serbia.

Gross alpha and beta activities, (3)H, (226)Ra, (232)Th and (40)K activities were measured in bottled mineral water produced in Serbia in order to assess its radiological quality. In 11 samples of tap water and in 1 sample of spring waters gross alpha and beta activity were determined. The natural activity concentration of alpha and beta emitting radionuclides are within the range recommended by World Health Organization. The tritium concentration in bottled mineral waters ranged from 0.023 ± 0.012 to 0.046 ± 0.006 Bq l(-1). The activity of (226)Ra, (232)Th and (40)K were below the minimum detectable activity. In order to evaluate the annual effective dose for different classes of age, a conservative dosimetric calculation was carried out.

Different methods for tritium determination in surface water by LSC

The main aim of this paper was to compare different methods of preparing water samples for tritium analysis by ultra-low-level background liquid scintillation counter, Quantulus 1220. Three methods of sample preparation for low-level tritium measurement have been implemented in the Nuclear Physics Laboratory in Novi Sad: electrolytic enrichment, direct method without electrolytic enrichment and sample Oxidizer 307 method. The examined fresh water samples were rainfall collected during 6 months and water from a stream in the Vinča nuclear research center collected over 3 months. The obtained results using these three methods showed satisfying agreement. The appropriate measuring time by LSC for each sample prepared according to different methods has been determined.

Improvement of measuring methods and instrumentation concerning 222Rn determination in drinking waters – RAD7 and LSC technique comparison

A procedure for the determination of (222)Rn in environmental water samples using liquid scintillation counting (LSC) was applied and optimized. A minimum detectable activity of 0.029Bql(-1) in a 20ml glass vial (10ml water sample mixed with 10ml of liquid scintillation cocktail) has been achieved during 300min of measurement time. The procedure was compared with RAD7 radon detector measurements. (226)Ra content in the water was determined by gamma-ray spectroscopy. Applications to drinking waters collected from public drinking fountains in the Vojvodina (Serbia) are presented with annual effective dose for ingestion and inhalation for adults calculated.

NATURAL RADIOACTIVITY IN RAW MATERIALS USED IN BUILDING INDUSTRY IN SERBIA

Natural radioactivity is responsible for most of the total radiation dose received by human population. Geological materials used in building industry usually become contaminated with naturally occurring radioactive materials. They are used as mixtures in building industry (kaolin, zircon, frit, feldspar) or mechanically processed and used for covering floors and walls of the rooms (granite). In this paper, activity concentrations of 226Ra, 232Th and 40K in 6 kaolin, 11 zircon, 18 granite, 3 marble, 6 sand, 4 perlite, 4 feldspar, 5 korund and 1 frit samples imported in Serbia were determined by gamma-ray spectrometry. Activity concentration index, dose rate and annual effective dose were calculated for each of the investigated samples. Measurement of an external gamma dose rate by using a commonly available radiation survey meter can give some indication of the need for further investigations. The absorbed dose rate and annual effective doses for workers in the ceramic industry “Keramika Kanjiza Plus” in Serbia working with granite are determined.

Possibilities and limitations of color quench correction methods for gross alpha/beta measurements

Gross alpha/beta activity determination is utilized as a very popular Liquid Scintillation Counting (LSC) technique widely used in routine monitoring of drinking, surface and waste waters. Since quenching phenomena are most problematic effect during LSC measurements, the objectives of this paper are to present, consider and evaluate two methods for color quench correction as a proposal for supplement to the ASTM D 7283-06 method for gross α/β determination. The first method is PSA adjustment: application of previously established dependence of optimal PSA discriminator between alpha and beta events on quench level of sample. The second method assumes counting on usual optimal PSA setting and application of previously determined quench calibration curves in order to correct count rates in alpha and beta channels afterwards. Application on obtained activity results of few artesian well water samples and colored spiked samples, based on the measured SQP(E) value of samples, has been demonstrated, as the opportunity to compare the validity, reliability and limitations of both methods. All samples have been counted on low-background liquid scintilllation counter Quantulus 1220™.

PSA discriminator influence on 222Rn efficiency detection in waters by liquid scintillation counting

A procedure for the (222)Rn determination in aqueous samples using liquid scintillation counting (LSC) was evaluated and optimized. Measurements were performed by ultra-low background spectrometer Quantulus 1220™ equipped with PSA (Pulse Shape Analysis) circuit which discriminates alpha/beta spectra. Since calibration procedure is carried out with (226)Ra standard, which has both alpha and beta progenies, it is clear that PSA discriminator has vital importance in order to provide precise spectra separation. Improvement of calibration procedure was done through investigation of PSA discriminator level and, consequentially, the activity of (226)Ra calibration standard influence on (222)Rn efficiency detection. Quench effects on generated spectra i.e. determination of radon efficiency detection were also investigated with quench calibration curve obtained. Radon determination in waters based on modified procedure according to the activity of (226)Ra standard used, dependent on PSA setup, was evaluated with prepared (226)Ra solution samples and drinking water samples with assessment of measurement uncertainty variation included.

Radioactivity in the indoor building environment in Serbia

Measurement of activity concentrations of radionuclides in building materials and radon in indoor space is important in the assessment of population exposures, as most individuals spend 80 % of their time indoors. This paper presents the results of activity concentration measurements of: radon emanated from the soil, radionuclides (226)Ra, (232)Th and (40)K in the soil, indoor radon in the city of Novi Sad (the capital city of Vojvodina) using charcoal canisters and indoor radon in the Vojvodina region using alpha-track detectors and the radioactivity of some building materials. Influences of floor level, space under the rooms, boarding, and the heating system on indoor radon accumulation in the Vojvodina province, situated in the northern part of Serbia, are also presented in this paper. The total effective dose and the activity concentration index are calculated applying the dose criteria recommended by the European Union for building materials.

Establishment of a method for 222Rn determination in water by low-level liquid scintillation counter

A procedure for the determination of (222)Rn in environmental water samples using liquid scintillation counting (LSC) was performed. The (226)Ra content in the water was determined by gamma-ray spectroscopy. An application of this procedure to drinking water collected from a public drinking fountain in Vojvodina (Serbia) is presented, including calculations of the annual effective dose for ingestion and inhalation for adults.