Mass exhalation rates, emanation coefficients and enrichment pattern of radon, thoron in various grain size fractions of monazite rich beach placers

Study of the effect of temperature and water content on radon exhalation from phosphate using LR-115 detectors

A study of the influence of moisture content on the radon exhalation rate from phosphate samples (with and without consideration of the back diffusion effect) was performed using the sealed cup technique. The mass exhalation rate was found to increase with an increase in moisture content, reaching a maximum value of 2.414 ± 0.034 Bq kg-1 h-1 with a moisture content of 10%. However, the mass exhalation rate decreased with a continued increase in moisture content above 25%. The mass exhalation rate was also measured at different temperatures between -10 and 50°C. The obtained results show that the mass exhalation rate increases linearly with temperature. We point out that all the obtained values of radon exhalation rate are lower than the world average radon exhalation rate (57.6 Bq m-2 h-1).

The influence of building material structure on radon emanation

In this work, the radon emanation coefficients for selected building materials that are most often used in Serbia for covering floor surfaces (concrete, concrete screed, granite, glazed ceramic tiles, marble, roofing tile, and terrazzo tile) were determined, and the influence of the material structure on their values. The concentration of²²⁶Ra activity in the samples was determined using the gamma spectrometry method. Radon emanation was measured with the RAD7 device. The porosity of the samples was tested using mercury intrusion porosimetry and water absorption methods, and the structural analysis was performed using x-ray diffraction analysis and x-ray fluorescence analysis. The measured values of²²⁶Ra activity concentrations were in the range (4.93-298) Bq kg^-1, and the estimated values of the radon emanation coefficients were in the range (0.55-6.05) %. The obtained results indicate that the chemical and mineralogical composition, method of production, and the²²⁶Ra activity concentration have an influence on the emanation of radon from the material. No significant correlation was found between the radon emanation coefficient and the open porosity of the material, most likely due to the inhomogeneous presence of pores of different dimensions in the materials. It was established that the total value of the emanation coefficient depends on the emanation coefficient for pores ⩽100μm in size.

Study of Surface Emissions of 220Rn (Thoron) at Two Sites in the Campi Flegrei Caldera (Italy) during Volcanic Unrest in the Period 2011–2017

The study concerns the analysis of 220Rn (thoron) recorded in the surface soil in two sites of the Campi Flegrei caldera (Naples, Southern Italy) characterized by phases of volcanic unrest in the seven-year period 1 July 2011–31 December 2017. Thoron comes only from the most surface layer, so the characteristics of its time series are strictly connected to the shallow phenomena, which can also act at a distance from the measuring point in these particular areas. Since we measured 220Rn in parallel with 222Rn (radon), we found that by using the same analysis applied to radon, we obtained interesting information. While knowing the limits of this radioisotope well, we highlight only the particular characteristics of the emissions of thoron in the surface soil. Here, we show that it also shows some clear features found in the radon signal, such as anomalies and signal trends. Consequently, we provide good evidence that, in spite of the very short life of 220Rn compared to 222Rn, both are related to the carrier effect of CO2, which has significantly increased in the last few years within the caldera. The hydrothermal alterations, induced by the increase in temperature and pressure of the caldera system, occur in the surface soils and significantly influence thoron’s power of exhalation from the surface layer. The effects on the surface thoron are reflected in both sites, but with less intensity, the same behavior of 222Rn following the increasing movements and fluctuations of the geophysical and geochemical parameters (CO2 flux, fumarolic tremor, background seismicity, soil deformation). An overall linear correlation was found between the 222−220Rn signals, indicating the effect of the CO2 vector. The overall results represent a significant step forward in the use and interpretation of the thoron signal.

Radon gas build up using alpha scintillation cell: Experimentally and theoretically

Due to their high efficiency and speed of use, alpha scintillation cell is being increasingly utilized for detection of radon (222Rn) in soil gas. The calibration factor of the 110 A active radon cell has been addressed and thoroughly discussed. The sensitivity and the efficiency have been determined. It is found that the sensitivity and the registration efficiency of this scintillation cell (110 A active cell) are equal to 0.015895 cpm/Bq/m³, 59%. Respectively. A nuclear system was adapted to measure the accumulation of radon gas using the active scintillation cell. The growth curves of radon activity have been investigated. Radon emanation, leakage and back diffusion rates from natural occurring radioactive materials has been determined. Compatibility between practical measurements and results based on the theoretical equation were achieved.

Factors controlling the distribution of radon (222Rn) in groundwater of a tropical mountainous river basin in southwest India

Studies on occurrence of radon in the environment are receiving growing attention worldwide due to its adverse impact on human health. Despite that, the dissolved radon in water is found to be a useful tracer in many hydrogeological studies. Although, several studies focused on the occurrence of high ²²²Rn in groundwater, the processes responsible for its variation is still not well understood. Hence, an attempt has been made in the present study to elucidate the underlying factors influencing the abundance ²²²Rn in hard rock (gneissic) aquifers of Karamana River Basin, southwest India. ²²²Rn in groundwater was analyzed in 71 dug wells during the pre-monsoon period of 2017. A large variability in ²²²Rn activities (170-68,350 Bq/m³) was noticed in groundwater and high activities were mainly seen in the khondalite formation. No significant dependencies between ²²²Rn activity and depth to water table, groundwater temperature and electrical conductivity were observed. However, majority of the presence of high ²²²Rn activity in groundwater matches with the location of lineaments. Furthermore, radium content in the host rock, degree of weathering and fracturing and the emanation coefficient of the rock were found to have an important bearing on the occurrence of radon in groundwater. The underlying factors influencing the abundance of radon in hard rock aquifers were also conceptualized. Thus, the study highlights the usefulness of ²²²Rn as a potential tool in delineating the macro-structural features like fractures/lineaments that are significant repositories of groundwater, which could be explored for groundwater development in hard rock terrains.