R. Breier

Simulation of background characteristics of low-level gamma-ray spectrometers using Monte Carlo method.

A computing code based on the CERNs GEANT4 has been used to compute cosmic-ray background components of low-level Ge-spectrometers, optionally equipped with an anticosmic shield made of a plastic scintillation detector. The results show that the background of the Ge detector placed at 100 m w.e. (water equivalent) has decreased by a factor of 30 and 100 without and with anticosmic shielding, respectively, when compared with a surface laboratory without anticosmic shielding.

Monte Carlo simulation of background characteristics of a HPGe detector operating underground in the Gran Sasso National Laboratory

Monte Carlo (MC) simulation of background components of an ultra-low background high purity germanium (HPGe) detector operating in a deep underground laboratory was carried out. The results show that the background of the HPGe detector is about two orders of magnitude higher than the MC prediction when accounting only for cosmic-ray induced background. The difference is due to natural radioactivity in the parts surrounding the Ge detector. To get reasonable agreement between MC simulations and the experiment, a contamination in the parts surrounding the Ge crystal from 40K, 208Tl and 214Bi of 0.1mBqkg-1 was required to include in the simulations.

Spatial Radiocarbon and Stable Carbon Isotope Variability of Mineral and Thermal Waters in Slovakia

Isotope hydrology investigations were carried out with the aim to study isotope variability in mineral and thermal waters (MTW) of Slovakia. The aquifers of MTW were formed by Triassic limestones and dolomites, which are found in the mountains as well as in the pre-Tertiary substratum of depressions and lowlands. The MTW were of artesian and/or open structures. At present, there are only boreholes available, as natural outflows have already been captured by them. Large spatial isotope variability (14C between 2 and 33.6 pMC, δ18O between -11.8‰ and -9.8‰, and δ13C between -12.7‰ and -3.4‰ for bicarbonates and -21‰ and -4.9‰ for free CO2) and heterogeneity of MTW was observed, indicating different origins of MTW. Corrected radiocarbon apparent ages of MTW indicate that they mostly infiltrated during the W?rm and Holocene periods.

Joint Bratislava–Prague studies of radiocarbon and uranium in the environment using accelerator mass spectrometry and radiometric methods

A research program has been established between Bratislava and Prague groups to study natural and anthropogenic radionuclides in the environment using both Accelerator Mass Spectrometry (AMS) and radiometric methods. The first studies have focused on 14C activity variations in the atmosphere and biosphere with the aim to evaluate an impact of Czech and Slovak Nuclear Power Plants (NPP) on the environment, and on the development of AMS technique for investigation of actinides (mainly uranium isotopes) in the environment.

Recent results from the AMS/IBA laboratory at the Comenius University in Bratislava: preparation of targets and optimization of ion sources

Developments of solid targets and optimizations of ion sources were carried out with the aim to produce high ion yields for applications of tandem accelerators as mass spectrometers. A comparison of Al− yields from different aluminum targets showed that the best results were obtained with AlN targets. Transmission studies of 9Be and 12C ions through the Pelletron accelerator showed highest efficiencies for 9Be2+ and 12C2+. First results obtained with a simplified version of the AMS line are presented as well.

Monte Carlo simulation of environmental background sources of a HPGe detector operating in underground laboratory

The overlying rock of underground laboratories provides excellent radiation shielding necessary for many experiments searching for extremely rare nuclear and astroparticle events. Monte Carlo simulations of HPGe detector background and attenuation of gamma-ray fluxes with different shielding configurations were carried out for an underground laboratory. It has been found that even a small radioactive contamination of the shielding material may increase gamma-ray fluxes in underground laboratory by several orders of magnitude.