MODEL CALIBRATION OF AN AIRBORNE GAMMA SPECTROMETER FOR SEARCHING OF RADIONUCLIDE SOURCES USING UAV.

A study of a small airborne gamma spectrometer usability, carried by unmanned aerial vehicle (UAV), during a search for radionuclide sources and estimating their activity was performed. Model calculations of calibration coefficients for Georadis D230A spectrometer (with two NaI (Tl) 2″ x 2″ detectors), 241Am, 57Co, 137Cs, 192Ir, 60Co and 152Eu radionuclides and set of flight altitudes from 1 up to 25 m were done. The results were compared with the results of experimental measurements for 137Cs and 60Co sources using vertical heights up to 10 m above the source on the ground. Simulated and discussed is the possible significant influence of the source construction and housing and the position/orientation of the source (due to non-isotropic emission) to estimate the activity of an unknown source. The influence of the natural background and estimation of flight line spacing requirements when planning a UAV route to ensure source localization depending on its activity are discussed.

ANALYSIS OF RADON TIME SERIES RECORDED IN SLOVAK AND CZECH CAVES FOR THE DETECTION OF ANOMALIES DUE TO SEISMIC PHENOMENA.

Anomalies in the radon (222Rn) releases in underground environments are one of the phenomena that can be observed before earthquake occurrence. Continuous measurements of radon activity concentration, and of meteorological parameters that influence the gas emission, were performed in three Slovak and Czech caves during 1-y period (1 July 2016-30 June 2017). The radon activity concentration in caves shows seasonal variations, with maxima reached during summer months. The anomalies in the radon time series are identified using a combination of three mathematical methods: multiple linear regression, empirical mode decomposition and support vector regression. The radon anomaly periods were compared with earthquake occurrences in Europe. Coincidences between both phenomena were found, since all monitored caves reflect contemporaneous local tectonic changes. The results indicate that radon continuous monitoring could assist a better understanding of radon emissions, along active tectonic structures, during seismic events.

THE USE OF DECONVOLUTION TECHNIQUE FOR THE ANALYSIS OF GAMMA SPECTROMETRY DATA FROM FIELD MONITORING USING UNMANNED AERIAL VEHICLES.

Airborne gamma spectrometry is an effective tool for prompt monitoring and mapping of large areas contaminated after NPP accident, radionuclides leakage cases, an impact of uranium ore mining and processing, etc. Airborne spectrometry data analysis using deconvolution technique enables to calculate air kerma rates and/or radionuclides concentrations as well as identification of radionuclides. Application of this technique on the airborne data (from manned as well as an unmanned survey using drones) is rather specific due to the requirements for short time of one scan data acquisition, a relatively long distance from the source and small detector size, due to the limited payload of the usually used drones. Application of deconvolution techniques for analysis of spectra with very poor statistics, methods and possibilities to improve the processing of such spectra are discussed.

Gamma spectrometric measurements of depth-related radionuclide distribution in walls.

The method for depth-related radionuclide distribution was evolved for approximate determination of the spatial lay-out of radionuclides in materials. The method is based on different attenuation coefficients for various energies of gamma radiation. For each material, the attenuation coefficient decreases with rising energy of radiation. It is therefore possible to assess the location of radionuclides in a material owing to attenuation on the track which a photon has to pass through the material. In this case, gamma lines with energies 609 and 1764 keV produced by nuclide (214)Bi were used for depth-related radionuclide distribution. This application should be suitable for locating radionuclides in the walls of buildings where high dose rates from gamma radiation occur. These doses are caused by natural radionuclides, mainly radium daughters. The presence of radionuclides in houses poses a high risk associated with inhalation of radon and its decay products. For suitable remediation, it is necessary to know the radionuclide depth distribution.

Radiation sources in the environment near NPP Temelin.

A widely discussed question is how much a nuclear power plant really contributes to irradiation of the people living in its vicinity. A number of laboratory and in situ measurements were performed in the area surrounding NPP Temelin, on the basis of which we can specify the irradiation of this area from various sources. The evaluation includes the contributions from natural sources, such as radon, terrestrial radiation and cosmic radiation, together with the contribution from inhalation and ingestion of radionuclides. Medical irradiation and nuclear fallout are also included.

Data analysis from monitoring of radionuclides in the nuclear power plant Temelin ecosystem area.

Changes in the ecosystem occur naturally, however, can also be due to man's activity. The unique ecosystem monitoring based on studying contamination of the bioindicators by man-made radionuclides has been providing data from the area of nuclear power plant (NPP) Temelin (CR) using laboratory gamma spectrometry for past 8 years. The increase in radioactivity in the NPP ecosystem area resulting from its operation is evaluated through comparison with a zero level of (137)Cs mass activities and by obtained data trend analysis.

Investigation and remediation of houses affected by radon phenomena connected with earlier exploration of silver and uranium ore.

The sources of gamma radiation inside buildings affected by earlier silver and uranium mining activities are discussed. Possibilities how to reduce gamma dose rates from building materials were studied on several houses located in the old mining town Jáchymov. Results of the efficiency analysis are presented. Experience obtained up to now indicates that it is almost impossible to reduce the gamma dose rates in such buildings to the level corresponding with the natural background, because some of the gamma radiation sources cannot be completely removed from the building structures.