Fast determination of indoor radon (222Rn) concentration using liquid scintillation counting

Occurrence of 222Rn and 226,228Ra in underground water and 222Rn in soil and their mutual correlations for underground water supplies in southern Greater Poland

European Union Council Directive 2013/51/EURATOM recently sets out so-called indicator parameters for: radon, tritium and indicative dose of water intended for human consumption. The aim of this research was to elaborate an effective procedure for determination of radon and radium ^226,228Ra isotopes (which are potentially the main contributors to the internal dose from drinking and cooking water) and to find the possible relationships between these radionuclides in underground water reservoirs and ²²²Rn concentration in the soil gas in their vicinity. The research was performed by applying a non-volatile and water-immiscible scintillation cocktail based on a pure diisopropylnaphthalene (Ultima Gold F: UGF), which allow for efficient radon extraction from 0.5 dm³ of water samples to 20 cm³ of scintillation phase and its direct determination with a detection limit of 5 × 10^-3 Bq dm^-3. The further preliminary concentration of 3 dm³ of crude water samples by evaporation to 0.5 dm³ samples led to the removal of all unsupported ²²²Rn activity and allowed the ²²⁶Ra determination via equivalent ²²²Rn detection after one-month samples storage using a low-background Triathler liquid scintillation counter in the α/β separation counting mode. Together with determination of ²²⁶Ra isotope in water samples, the simultaneous measurements of ²²⁸Ra and ²²²Rn radionuclides concentrations in water as well as ²²²Rn activity in the soil gas around the water supply sites were performed. The achieved limit of ²²⁶Ra detection was at a very low level of 10^-3 Bq dm^-3. The measured values of ²²⁶Ra concentration in 50 public underground water supply units for the Kalisz district of Poland were relatively low and ranged from below detection limit to 28.5 × 10^-3 Bq dm^-3 with arithmetic mean and median values of 12.9 and 12.2 × 10^-3 Bq dm^-3, respectively. Weak correlations were observed between activity concentrations of ²²⁶Ra and ²²²Rn in the crude water samples (R² = 0.31) and ²²²Rn in water and its concentration in the nearby soil gas (R² = 0.48).

Indoor radon exposure and excess of lung cancer mortality: the case of Mexico-an ecological study

Radon is a radioactive gas that can migrate from soils and rocks and accumulate in indoor areas such as dwellings and buildings. Many studies have shown a strong association between the exposure to radon, and its decay products, and lung cancer (LC), particularly in miners. In Mexico, according to published surveys, there is evidence of radon exposure in large groups of the population, nevertheless, only few attention has been paid to its association as a risk factor for LC. The aim of this ecological study is to evaluate the excess risk of lung cancer mortality in Mexico due to indoor radon exposure. Mean radon levels per state of the Country were obtained from different publications and lung cancer mortality was obtained from the National Institute of Statistics, Geography and Informatics for the period 2001-2013. A model proposed by the International Commission on Radiological Protection to estimate the annual excess risk of LC mortality (per 10⁵ inhabitants) per dose unit of radon was used. The average indoor radon concentrations found rank from 51 to 1863 Bq m^-3, the higher average dose exposure found was 3.13 mSv year^-1 in the north of the country (Chihuahua) and the mortality excess of LC cases found in the country was 10 ± 1.5 (range 1-235 deaths) per 10⁵ inhabitants. The highest values were found mainly in the Northern part of the country, where numerous uranium deposits are found, followed by Mexico City, the most crowded and most air polluted area in the country. A positive correlation (r = 0.98 p < 0.0001) was found between the excess of LC cases and the dose of radon exposure. Although the excess risk of LC mortality associated with indoor radon found in this study was relatively low, further studies are needed in order to accurately establish its magnitude in the country.

Survey of indoor radon (Rn-222) entry and concentrations in different types of building in Kalisz, Poland

Indoor radon (222Rn) was surveyed in a total of 141 individual houses and apartments used precalibrated passive PicoRad Detectors. The radon activity in the soil gas around the dwellings was simultaneously measured. The arithmetic mean values of indoor radon concentrations for detached houses, old buildings (up to four-stories), prefabricated blocks of flats (mostly five stories) and high-rise residential buildings (10-stories) were:, 70.9; 46.5; 38.4, and 56.6 Bq m−3, respectively. The average arithmetic mean value for all measured rooms equals 51.8 Bq m−3. The calculated average effective dose from indoor radon for the local population was equal to 2.2 mSv.

Distribution of uranium and thorium chains radionuclides in different fractions of phosphogypsum grains

This work presents results obtained using gamma spectrometry measurements of phosphogypsum samples on a non-fractionated (native) and fractionated phosphogypsum byproduct. The phosphogypsum was divided into particles size fractions within the range of < 0.063, 0.063-0.090, 0.090-0.125, 0.125-0.250, and over 0.250 mm and analyzed after reaching radioactive equilibrium using high-resolution gamma spectrometry technique. It was found that there is no significant differentiation between ²²⁶Ra distribution among particular grain size fractions of this material; however, tendency for preferential retention of radionuclides in particular grain size fractions is observed. The detailed analysis of results revealed that radium is preferentially retained in smaller grain size fractions, whereas lead and thorium in coarse fractions. The results indicate that overall ²²⁶Ra activity concentrations between particular fractions of phosphogypsum vary globally between - 34 and + 47% regarding non-fractionated material, and for ²¹⁰Pb activity concentration, fluctuations are found between - 26 up and + 38%. Presumably, the mechanism of radium incorporation into gypsum phase is based on a sequence of radium bearing sulfate phases formation followed by a surface adsorption of these phases on the calcium sulfate crystals, whereas for lead and thorium ions, rather incorporation into crystal lattice should be expected as more likelihood process.

A fast method for the simultaneous determination of soil radon (222Rn) and thoron (220Rn) concentrations by liquid scintillation counting

This paper presents a fast method dedicated to measurements of radon nuclides in the soil gas. The soil gas is sampled by a typical hollow tube probe by 10 min of sucking of about 3 dm³ of gas and passing it directly through a 16 cm³ of water-immiscible liquid scintillator placed in a typical 20 cm³ scintillation vials, where the radon and thoron nuclides are effectively absorbed. Most of the presently used active methods for radon isotopes determination (e.g., RAD7 or AlphaGuard) require the soil gas transfer to the measuring device. The serious limitation of such approach is the necessity to wait until the radon daughter isotopes decay, before counter is ready for the next measurement. In the proposed method, several samples can be simultaneously gathered from the examined areas in the form of the scintillation vials, which are ready for later measurements in the automatic liquid scintillation counters in the lab or directly in situ. For that purpose, the combined mathematical model for the simultaneous radon and thoron determination has been elaborated. The direct in situ measurements of the sample activity between 60 and 240 s after the end of sampling followed by a second activity measurement after 3 h allow for the determination of both ²²⁰Rn and ²²²Rn concentrations in the soil gas. The limit of detection for ²²²Rn isotope during 10 min counting is 25 Bq·m^-3, whereas for a 3 min counting of ²²⁰Rn just after sampling was found to be ca. 150 Bq·m^-3. The method was successfully verified and applied for the simultaneous radon and thoron concentrations measurements in the soil gas in Central Poland region.