Radon, radon progeny and equilibrium factor determination using an LR115 detector

Variation of total alpha and beta activities and Rn-222 concentrations in the water supply system of an Italian volcanic region: How safe is tap water for human consumption?

Total alpha and beta activities and Rn-222 concentrations were determined in water from different sections of seven aqueducts belonging to the water supply system of Campania region (Italy), known worldwide for its volcanism. Statistical analysis was performed on data to account for their variability across the aqueduct sections, and results were discussed considering the geology of reservoirs, the potential mixing processes occurring along the pipe network, the building/constituting materials of the aqueduct sections, and the integrity of the infrastructure. Guidelines proposed by Italian and international regulation entities were considered to determine if total alpha and beta activities and Rn-222 concentrations found at the taps of the different aqueducts should be considered detrimental to public health. Based on a deterministic and a stochastic approach, a health risk assessment was also tested for Rn-222, assuming direct ingestion and showering as potential exposure pathways. Results showed that applying guidelines returned an absence of hazard, whereas risk assessment returned a high probability of exposure to unacceptable Rn-222 doses for some aqueducts. Beyond the usefulness of obtained results to plan actions to improve the safety of drinking water in Campania, our outcomes represent a warning for bodies dealing with public health at any level: the use of guidelines can bring an underestimation of the risks exerted by the exposure to Rn-222 on human health. Further, using a probabilistic approach in risk assessment accounting for uncertainty can favor risk forecasts based on more "realistic" scenarios.

RADIOLOGICAL IMPACT OF SOME COMMON FOODS OF SOUTHERN PART OF WEST BENGAL, INDIA

An appreciable portion of human exposure to natural radioactivity comes from food and drinking water. Gross alpha radioactivity has been measured in thirty one food items consumed almost every day by the people of southern part of West Bengal, India, by using the solid state nuclear track detector LR-115. The annual effective doses due to intake of alpha-emitting radionuclides through these food items have also been estimated, and the total average annual dose received by an adultthrough ingestion of these foodstuffs calculated, considering the food habit of the people of the region. The total average annual dose is below the 1 mSv y-1 limit proposed by WHO, and over half of this annual dose comes from consumption of cereals.

INNOVATIVE EASY-TO-USE PASSIVE TECHNIQUE FOR 222RN AND 220RN DECAY PRODUCT DETECTION

The decay products of radon and thoron are essentially the radioisotopes of polonium, bismuth and lead, and are solid particulates, which deposit in different parts of the respiratory tract upon inhalation, subsequently emitting high-energy alpha particles upon their radioactive decay. Development of passive deposition-based direct progeny sensors known as direct radon and thoron progeny sensors have provided an easy-to-use technique for time-integrated measurements of the decay products only. These dosemeters are apt for large-scale population dosimetry to assign inhalation doses to the public. The paper gives an insight into the technique, the calibration, comparison with the prevalently used active grab filter paper sampling technique, alpha track diameter analysis in these progeny sensors, progeny deposition velocity measurements carried out using these detector systems in the indoor as well as outdoor environment, and applications of these sensors for time-integrated unattached fraction estimation.

Preliminary study on the variation of radon-222 inside greenhouse of Shouguang county, China

Studies on radon have become the focus of indoor radiation. In this study, we chose greenhouse to be the study field, the research aims to: (1) explore the diurnal variation of radon concentration inside greenhouse in Shouguang county, China; (2) pre-analyze the relationship between radon concentration, temperature and relative humidity, and shed light on the radon behavior characteristic inside greenhouse; (3) verify the feasibility of calculating radon radiation dose by using short-period detected radon concentrations in typical months in Shouguang county. The following conclusions were drawn. Firstly, the average radon levels in typical months in Shouguang county are all much higher than that in ordinary dwellings in China, diurnal and seasonal variations in radon levels are observed inside greenhouse. Secondly, temperature and relative humidity may play a role indirectly through affecting soil moisture and other factors. The mechanism need to be further studied. Thirdly, radon concentrations detected in typical months are still useful in preliminary estimation of radon radiation dose for vegetable-plant farmers in Shouguang county.

Theoretical basis for long-term measurements of equilibrium factors using LR 115 detectors

In this paper, we propose a method to determine the equilibrium factor using a bare LR 115 detector. The partial sensitivities rhoi of the LR 115 detector to 222Rn and its alpha-emitting short-lived progeny, 218Po and 214Po, were investigated. We first determined the distributions of lengths of major and minor axes of the perforated alpha tracks in the LR 115 detector produced by 222Rn, 218Po and 214Po through Monte Carlo simulations. The track parameters were calculated using a track development model with a published V function, by assuming a removed active layer of 6.54 microm. The distributions determined for different alpha emitters were found to completely overlap with one another. This implied equality of partial sensitivities for radon and its progeny, which was also confirmed through analytical considerations. Equality of partial sensitivities makes possible convenient measurements of the proxy equilibrium factor Fp, which is defined in the present work as (F1+F3) and is equal to the ratio between the sum of concentrations of the two alpha emitting radon progeny (218Po+214Po) to the concentration of radon gas (222Rn). In particular, we have found Fp = (rho/rhoitC0)-1, where rho (track/m2) is the total track density on the detector, rhoi = 0.288 x 10(-2) m, t is the exposure time and C0 (Bq/m3) is the concentration of 222Rn. If C0 is known (e.g. from a separate measurement), we can obtain Fp. The proxy equilibrium factor Fp is also found to be well correlated with the equilibrium factor between radon gas and its progeny through the Jacobi room model. This leads to a novel method for long-term determination of the equilibrium factor.

Sensitivity of LR115 detector in diffusion chamber to 222Rn in the presence of 220Rn

Determination has been made of the sensitivity of LR115 type 2-track detectors (in units of m) to 222Rn, measured in the presence of 220Rn. Measurements have been made by means of a widely used diffusion chamber while Monte Carlo simulations have also been conducted. The experimentally derived sensitivities for 222Rn and 220Rn were found to be 0.470+/-0.022 and 0.486+/-0.042 m, respectively. For Monte Carlo simulations, the sensitivities to 222Rn gas were found to range from 0.618 x 10(-2) m (assuming that all 218Po progeny decay before deposition onto the internal walls of the diffusion chamber) to 0.405 x 10(-2) m (assuming that all 215Po progeny are deposited on the internal walls of the same containment vessel before decaying). The sensitivity to 220Rn gas of 0.465 x 10(-2) m found from Monte Carlo simulations agrees to within uncertainty with experimental findings. The experimentally derived sensitivity value for 222Rn indicates that 30% of the 218Po progeny decay before deposition onto the internal walls of the diffusion chamber.