R. C. Ramola

A study of seasonal variations of radon levels in different types of houses

Abstract A study of the seasonal variations of radon and its decay products in the houses of Tehri Garhwal have been carried out by using LR-115, type II plastic track detector. Radon levels were found to be higher in mud houses than in cemented houses. Radon levels were recorded high in winter and autumn and low in summer and rainy season. However, it is measured highest in winter and lowest in the summer. The season/annual ratios for different type of houses vary substantially among different places. These values were found to vary from 0.91 to 1.07 ana 0.85 to 1.14 for cemented houses and mud houses, respectively. Behaviour of indoor radon for different seasons at different places is discussed in detail. The results show that the seasonal variations with indoor radon levels should be taken in to account to calculate annual effective dose equivalent.

Soil-gas radon as seismotectonic indicator in Garhwal Himalaya

Research on earthquake-related radon monitoring has received enormous attention recently. Anomalous behaviour of radon in soil and groundwater can be used as a reliable precursor for an impending earthquake. While earthquake prediction may not yet be possible, earthquake prediction research has greatly increased our understanding of earthquake source mechanisms, the structural complexities of fault zones, and the earthquake recurrence interval, expected at a given location. This paper presents some results of continuous monitoring of radon in soil-gas in Garhwal Himalaya, India. Daily soil-gas radon monitoring with seismic activity and meteorological parameters were performed in the same laboratory system, located at H.N.B. Garhwal University Campus, Tehri Garhwal, India. Radon anomalies along with meteorological parameters were found to be statistically significant for the seismic events within the magnitudes M2.0-M6.0 and epicentral distances of 16-250 km from the monitoring station. The frequent positive and negative anomalies with constant environmental perturbation indicate the opening and closing of micro cracks within the volume of dilatancy by strain energy. The spike-like and sharp peak anomalies were recorded before, during and after earthquakes occurred in the area. The variations in radon concentrations in soil-gas are found to be correlated with seismic activities in the Garhwal Himalaya. The correlation between radon level and meteorological parameters is also discussed.

Relation between soil-gas radon variation and different lithotectonic units, Garhwal Himalaya, India

Abstract Measurements of radon concentration and uranium content in soil and rocks were made in the regions of the Alaknanda and Bhagirathi valleys in the Garhwal Himalaya by using radon emanometry and X-ray fluorescence method, respectively. The data were collected from different lithotectonic units along and across the various regional thrust planes, faults, shears, etc. The observed values were then correlated with the geological formations and structure of the area. Radon concentrations were found to be controlled by lithology, structure and associated uranium mineralization. A positive linear correlation was also observed between soil-gas radon and in situ uranium in the area.

Measurement of radon exhalation rate from soil samples of Garhwal Himalaya, India

Laboratory experiment was performed for the measurement of radon exhalation rate from the soil samples collected from Garhwal Himalayas. This study is accompanied by the measurement of soil-gas radon concentration in the same area. Both results were compared with the geological formation and structure of the area. No correlation was observed between soil-gas radon concentration and radon exhalation rate. However, it was found to be controlled by the lithology, geological structure and uranium mineralization in the area. The relationship between radon emanation, geological formation and occurrence of high indoor radon concentration is discussed.

Geology of radon occurrence around Jari in Parvati Valley, Himachal Pradesh, India

Abstract Soil gas and indoor radon concentrations have been measured around Jari in Parvati Valley, Himachal Pradesh, India, to study their relationship with the local geology. Both soil gas and indoor radon concentrations were found to be higher near structurally controlled uranium mineralization. Indoor radon levels in the houses of the study area are considerably higher than the ICRP recommended value of 200 Bq m −3 . The high indoor radon concentration found may be attributed to the geology of the area. This area needs more detailed investigation as it may be one of the areas of high radon risk in India.

A comparative study of the effect of O+7ion beam on polypyrrole and CR-39 (DOP) polymers

Polypyrrole thin films doped with para-toluene sulphonic acid were prepared by the electrochemical process. High-energy ion beam irradiation of the polymers is an effective technique to enhance the electrical conductivity, structural property and mechanical properties. So polypyrrole and allyl diglycol carbonate (CR-39 (DOP)) films were irradiated by oxygen ions (energy 100MeV, charge state O +7 ) with fluence varying from 1 × 10 10 to 1 × 10 13 ionscm −2 . The effects of swift heavy ions (SHI) on the structural, optical and surface properties of polypyrrole (Ppy) and CR-39 (DOP) polymers were studied in this work using x-ray diffraction (XRD), UV‐visible spectroscopy and scanning electron microscopy (SEM). XRD patterns of the pristine and irradiated polymer show that the crystallinity improved after the irradiation with SHI. At the low fluence, crystallinity was found to increase but at high fluence, it decreases which could be attributed to cross-linking and degradation mechanism. The UV‐visible spectra show a shift in the absorbance edge towards higher wavelength, which can be correlated with the transition involved in the polymer and variation in the band gap using Tauc’s expression. The band gap of polypyrrole was found to decrease from 3.4 to 3.0eV after irradiation. CR-39 (DOP), however, showed a very large change in the band gap from 4.8 to 3.4eV. The SEM study shows a systematic change in the surface morphology of the polymers with increasing ion fluence. (Some figures in this article are in colour only in the electronic version)

Preliminary indoor thoron measurements in high radiation background area of southeastern coastal Orissa, India

This paper presents the preliminary results of radon and thoron measurements in the houses of Chhatrapur area of southeastern coast of Orissa, India. This area is one of the high radiation background radiation areas in India, which consists of monazite sand as the source of thoron. Both active and passive methods were employed for the measurements. Radon and thoron concentrations were measured in the houses of Chhatrapur area using twin cup radon dosemeters, RAD7 and radon-thoron discriminative detector (Raduet). Thoron progeny concentration was also measured in the houses using deposition rate measurements. Radon and thoron concentrations in the houses of study area were found to vary from 8 to 47 Bq m(-3) and the below detection level to 77 Bq m(-3), respectively. While thoron progeny concentration in these houses ranges between 0.17 and 4.24 Bq m(-3), preliminary investigation shows that the thoron concentration is higher than radon concentration in the houses of the study area. The thoron progeny concentration was found to be comparatively higher, which forms a base for further study in the area. The comparison between the results of various techniques is presented in this paper.

Measurement of Equilibrium Factor ”F” between Radon and its Progeny and Thoron and its Progeny in the Indoor Atmosphere Using Nuclear Track Detectors

Radon, thoron and their progeny are present in the indoor atmosphere as attached and unattached fractions. The level of ventilation in a house and the plating out of radon/thoron daughters onto surfaces decide the extent of equilibrium between them. Since the daughter products are mainly responsible for the inhaled dose, the measurement of the equilibrium factor, F, between radon/thoron and their progenies is desirable. It is therefore necessary to measure the equilibrium factor for different types of house construction, locations and seasons before projecting the dose from the measurements of radon and thoron. This paper presents the results of the measurement of F between radon, thoron and their progenies in dwellings using the LR-115 type II plastic track detector. The exposures were made with a twin-chamber dosimeter in about 150 houses of different types, distributed at different locations in the Garhwal and Kumaun region of the Himalayas in India. The measured equilibrium factor between radon and progeny varied from 0.02 to 0.90 with an average value of 0.28 while the same factor for thoron and progeny was found to vary from 0.01 to 0.90 with an average value of 0.09. The methods of measurement and results obtained are discussed in detail.

Radon in groundwater of eastern Doon valley, Outer Himalaya

Abstract The radon content in water may serve as a useful tracer for several geohydrological processes. The hydrodynamic factor, presence of radium in host rocks, as well as the soil porosity and permeability control its concentration in groundwater. In order to understand the factors that control the occurrence of radon in groundwater of Doon valley in Outer Himalaya, a total of 34 groundwater samples were collected from handpumps and tubewells covering three hydrogeological units/areas in the eastern part of Doon valley. Radon variation in tubewells and handpumps varies from 25.4±1.8 to 92.5±3.4 Bq / l with an average of 53.5±2.6 Bq / l . A significant positive correlation between radon concentration and depth of the wells was observed in the Doiwala–Dudhli and Jolleygrant areas suggesting that radon concentration increases with drilling depth in areas consisting of sediments of younger Doon gravels, whereas samples of the Ganga catchment show negative correlation. The high radon levels at shallower depths in the Ganga catchment (consisting of fluvial terraces of Ganga basin) indicate uranium-rich sediments at shallower depth.

Calibration of LR-115 Plastic Track Detectors for Environmental Radon Measurements

Solid-state nuclear track detectors are widely used for integrated measure ments of radon and its daughter products in the environment. However, these detectors have to be calibrated before use in field measurements. In the present work, LR-115 type II plastic track detectors have been calibrated in bare mode in a chamber containing a known radon concentration. The cali bration factor measured for this mode was 125 tracks.cm-2.d-1 = 1 WL (3.12 x 10-2 tracks.cm -2.d-1 = 1 Bq.m-3).