Dose estimation derived from the exposure to radon, thoron and their progeny in the indoor environment.

The annual exposure to indoor radon, thoron and their progeny imparts a major contribution to inhalation doses received by the public. In this study, we report results of time integrated passive measurements of indoor radon, thoron and their progeny concentrations that were carried out in Garhwal Himalaya with the aim of investigating significant health risk to the dwellers in the region. The measurements were performed using recently developed LR-115 detector based techniques. The experimentally determined values of radon, thoron and their progeny concentrations were used to estimate total annual inhalation dose and annual effective doses. The equilibrium factors for radon and thoron were also determined from the observed data. The estimated value of total annual inhalation dose was found to be 1.8 ± 0.7 mSv/y. The estimated values of the annual effective dose were found to be 1.2 ± 0.5 mSv/y and 0.5 ± 0.3 mSv/y, respectively. The estimated values of radiation doses suggest no important health risk due to exposure of radon, thoron and progeny in the study area. The contribution of indoor thoron and its progeny to total inhalation dose ranges between 13-52% with mean value of 30%. Thus thoron cannot be neglected when assessing radiation doses.

A COMPARATIVE STUDY OF DIURNAL VARIATION OF RADON AND THORON CONCENTRATIONS IN INDOOR ENVIRONMENT.

The diurnal measurements of radon and thoron concentrations were performed in the indoor environment of Nuclear Research Laboratory, Badshahi Thaul, Tehri Garhwal, Uttarakhand, India by using AlphaGUARD, Portable Radon Monitor (SMART RnDuo) and RAD7. Using AlphaGUARD, the radon concentration was found to vary from 8 to 94 Bq m-3 with an average of 41.5±22.2 Bq m-3 Using Portable Radon Monitor (SMART RnDuo), the concentration was found to vary from 2 to 101 Bq m-3 with an average of 41.7±23.6 Bq m-3, and with RAD7, the concentration was found to vary from 3 to 99 Bq m-3 with an average of 40±20.3 Bqm-3 While the thoron concentration using Portable Radon Monitor (SMART RnDuo) was found to vary from 4 to 65 Bq m-3 with an average of 17.3±12.9 Bqm-3, and using RAD7, the concentration was found to vary from 5 to 90 Bq m-3 with an average of 29.8±17.3 Bq m-3.

EMISSION OF SOIL GAS RADON CONCENTRATION AROUND MAIN CENTRAL THRUST IN UKHIMATH (RUDRAPRAYAG) REGION OF GARHWAL HIMALAYA.

In this paper, the result of systematic measurement of the soil gas radon concentrations is discussed and the background values are defined along and around the Main Central Thrust (MCT) in Ukhimath region of Garhwal Himalaya, India. The Ukhimath region is being subjected to intense neotectonic activities like earthquake and landslide. For the systematic study, the measurement has been done in grid pattern form along and across the MCT. The soil gas radon concentrations were measured using RAD7 with appropriate accessories and followed proper protocol proposed by the manufacturer. The soil gas concentration was measured at different depths 10, 30 and 50 cm with a wide range of different points from the MCT. At 10 cm depth, the soil gas radon concentration was found to vary from 125 to 800 Bq m-3 with an average of 433 Bq m-3; at 30 cm, it was found to vary from 203 to 32 500 Bq m-3 with an average of 2387 Bq m-3; and at 50 cm, it was found to vary from 1330 to 46 000 Bq m-3 with an average of 15 357 Bq m-3 The data analysis clearly reveals anomalous values along the fault.

STUDY OF RADIATION EXPOSURE DUE TO RADON, THORON AND THEIR PROGENY IN THE INDOOR ENVIRONMENT OF RAJPUR REGION OF UTTARAKHAND HIMALAYA.

In the present study, the measurements of indoor radon, thoron and their progeny concentrations have been carried out in the Rajpur region of Uttarakhand, Himalaya, India by using LR-115 solid-state nuclear track detector-based time-integrated techniques. The gas concentrations have been measured by single-entry pin-hole dosemeter technique, while for the progeny concentrations, deposition-based Direct Thoron and Radon Progeny Sensor technique has been used. The radiation doses due to the inhalation of radon, thoron and progeny have also been determined by using obtained concentrations of radon, thoron and their progeny in the study area. The average radon concentration varies from 75 to 123 Bq m-3 with an overall average of 89 Bq m-3 The average thoron concentration varies from 29 to 55 Bq m-3 with an overall average of 38 Bq m-3 The total annual effective dose received due to radon, thoron and their progeny varies from 2.4 to 4.1 mSv y-1 with an average of 2.9 mSv y-1 While the average equilibrium factor for radon and its progeny was found to be 0.39, for thoron and its progeny, it was 0.06.

STUDY OF RADON FLUX FROM SOIL IN BUDHAKEDAR REGION USING SRM.

In the present study, the radon flux rate of the soil is measured using portable radon monitor (scintillation radon monitor) in the Budhakedar region of District Tehri, India. The study area falls along a fault zone named Main Central Thrust, which is relatively rich in radium-bearing minerals. Radon flux rate from the soil is one of the most important factors for the evaluation of environmental radon levels. The earlier studies in the Budhakedar region shows a high level of radon (>4000 Bq m-3). Hence, it is important to measure the radon flux rate. The aim of the present study is to calculate the average estimate of the surface radon flux rate as well as the effective mass exhalation rate. A positive correlation of 0.54 was found between radon flux rate and radon mass exhalation rate.

Variability of radon and thoron equilibrium factors in indoor environment of Garhwal Himalaya.

The measurements of radon, thoron and their progeny concentrations have been carried out in the dwellings of Uttarkashi and Tehri districts of Garhwal Himalaya, India using LR-115 detector based pin-hole dosimeter and DRPS/DTPS techniques. The equilibrium factors for radon, thoron and their progeny were calculated by using the values measured with these techniques. The average values of equilibrium factor between radon and its progeny have been found to be 0.44, 0.39, 0.39 and 0.28 for rainy, autumn, winter and summer seasons, respectively. For thoron and its progeny, the average values of equilibrium factor have been found to be 0.04, 0.04, 0.04 and 0.03 for rainy, autumn, winter and summer seasons, respectively. The equilibrium factor between radon and its progeny has been found to be dependent on the seasonal changes. However, the equilibrium factor for thoron and progeny has been found to be same for rainy, autumn and winter seasons but slightly different for summer season. The annual average equilibrium factors for radon and thoron have been found to vary from 0.23 to 0.80 with an average of 0.42 and from 0.01 to 0.29 with an average of 0.07, respectively. The detailed discussion of the measurement techniques and the explanation for the results obtained is given in the paper.