J. Slivka

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.

Simple Method for Depleted Uranium Determination

When the issue of depleted uranium (DU) presence in the environment emerged, methods for analytical discrimination of DU against natural uranium should be developed. We present here a simple gamma-spectrometric method, based on the 238U–226Ra activity (non) equilibrium. The detection limit of the method for DU is of the order of magnitude of 10 Bq/kg (for about 50 ks counting), thus the method is appropriate for the determination of small amounts (≈100 Bq/kg) of DU in environmental samples. The method is tested on about 90 soil samples.

Evaluation of bremsstrahlung spectra generated by a 4‐MeV linear accelerator

A modified method for the evaluation of bremsstrahlung spectra on the basis of transmission measurements is presented. The method is tested for two 4 MeV therapy accelerators. The calculated spectra are compared with other experimental results and Monte Carlo simulation.

Methods of radon measurement

Several important international scientific organizations have designated radon as a carcinogenic and serious health problem. As a chemically inert gas, it is easily released from soil, building materials, and water, to emanate to the atmosphere. Since 1992, Laboratory for Nuclear Physics of the Department of Physics, Faculty of Sciences in Novi Sad has been involved in measurements of radon concentration in air, using several different techniques. Last year, systematic radon measurements in drinking waters began, too. The work presented here gives a survey and discussion of the results of the both series of measurements.

Correlations of natural radionuclides in soil with those in sediment from the Danube and nearby irrigation channels

The correlation between activity concentrations of some natural radionuclides ((238)U, (226)Ra, (232)Th, (40)K) measured in soil and in sediment taken from the Danube River and nearby irrigation channels was studied. The soil samples were collected from the northern part of Serbia and the sediment from the Serbian part of the Danube River and from the surrounding irrigation channels. The correlation between (238)U and other natural radionuclides in irrigation channel sediments was not as good as in the Danube. One of the possible explanations for this weak correlation can be the different chemical dynamics of (238)U in the irrigation channel sediment or changes of the (238)U activity concentration in irrigation channel sediment due to some human activities. The evaluation of ratios of activity concentrations of some natural radionuclides could be a more sensitive method for the determination of contaminant, rather than the straightforward analysis of activity concentrations.

Elimination of long lived fission products from river sediment

Abstract The activity concentration of 137 Cs, 134 Cs and 106 Ru in the sediment of the Danube river was measured for a period of 18 months after the Chernobyl accident. From the data fitted with a simple exponential decay function the same value of “corrected elimination half-life” T ec ≈ 240 d was derived for all three radionuclides.

Efficiency study of a big volume well type NaI(Tl) detector by point and voluminous sources and Monte-Carlo simulation.

The activity of environmental samples is usually measured by high resolution HPGe gamma spectrometers. In this work a set-up with a 9in.x9in. NaI well-detector with 3in. thickness and a 3in.×3in. plug detector in a 15-cm-thick lead shielding is considered as an alternative (Hansman, 2014). In spite of its much poorer resolution, it requires shorter measurement times and may possibly give better detection limits. In order to determine the U-238, Th-232, and K-40 content in the samples by this NaI(Tl) detector, the corresponding photopeak efficiencies must be known. These efficiencies can be found for certain source matrix and geometry by Geant4 simulation. We found discrepancy between simulated and experimental efficiencies of 5-50%, which can be mainly due to effects of light collection within the detector volume, an effect which was not taken into account by simulations. The influence of random coincidence summing on detection efficiency for radionuclide activities in the range 130-4000Bq, was negligible. This paper describes also, how the efficiency in the detector depends on the position of the radioactive point source. To avoid large dead time, relatively weak Mn-54, Co-60 and Na-22 point sources of a few kBq were used. Results for single gamma lines and also for coincidence summing gamma lines are presented.

Concentration factors of 137Cs in river sediment

Abstract The concentration factor of the isotope 137 Cs in River Danube sediment has been systematically measured for 6 yrs at two locations. A mean value of K = (7.1 ± 4.4) × 10 3 was derived. Neither systematic time variations of the concentration factor, nor any time correlation of the 137 Cs concentration in water and sediment could be observed, hence suggesting that the stationary state of this isotope distribution in the Danube is established. The results of the measurements show that the sediment can be considered as a reliable indicator of the radioactive contamination of rivers.

Depleted uranium determination in soil samples

Publisher Summary When the issue of depleted uranium (DU) presence in the environment emerged, methods for the analytical discrimination of DU against natural uranium had to be developed. This chapter presents here a simple gamma-spectrometric method, based on the 238 U– 226 Ra activity (non) equilibrium. Preliminary calculations that are still under way lead to the result that the lower limit of detection of DU is about 10 Bq kg −1 for a 50 ks measurement and thus the method is appropriate for the determination of small amounts (≈ 100 Bq kg −1 ) of DU in environmental samples. The method is tested on about 90 soil samples. The chapter concludes that the measurements on samples collected from Novi Sad prove the absence of detectable amounts of depleted uranium. However, in the southern part of Serbia samples contaminated with depleted uranium were found. The method for depleted uranium detection can be employed for further surveying the radioactivity of the region and especially for the investigation of depleted uranium migration from the contaminated areas.

Possibility of Prompt 238U Activity Concentration Determination by Gamma-Ray Spectroscopy

Recent results on 238U/234Th disequilibria in marine studies seriously challenge the possibility of the prompt gamma-ray spectroscopic determination of 238U activity concentration in environmental samples from the gamma-ray lines of the first daughter of 238U, the nucleus 234Th. In this paper we present the results of the gamma-ray spectrometric measurements of 234Th, which were repeated using the same soil and sediment samples at least one year after the first measurement. We did not find any indication of Th activity variation due to 238U/234Th disequilibria. All the obtained results prove that the 238U and depleted uranium determination in soil and sediment samples using 234Th gamma-ray lines introduces at most a systematic error of 3% into the obtained results.