Estimating radiation dose from building materials

Natural radioactivity in materials under certain conditions can reach the hazardous radiological levels. So, it becomes necessary to study the natural radioactivity in different materials to assess the dose for the population in order to know the health risks and to have a baseline for future changes in the environmental radioactivity due to human activities. The present study deals with the measurement of radioactivity using "gamma-ray spectrometry" from naturally occurring radionuclides in the soil, stone and sand samples used as building materials in North-Eastern Haryana state of India. The places are in the vicinity of Shivalik range of Himalayas. The activity concentrations for 226Ra, 232Th and 40K varied from 18 +/- 1.5 to 156 +/- 6Bqkg[-1], 23 +/- 1 to 300 +/- 5Bqkg[-1] and 32 +/- 0.5 to 1705 +/- 14 Bqkg[-1] respectively in various samples. The absorbed dose rate in soil, sand and stone samples is investigated at 1 m above ground level. Ra equivalents, Internal and external hazard indices have also been calculated. The natural radioactivity levels measured in the samples under present study are below the recommended limits except for black stone [SB] and red stone [SR]. However, these samples satisfy the universal standards

Radon exhalation rates from stone and soil samples of Aravali hills in India

The most popular building materials are soil bricks and different types of stones. Radon is released into ambient air from soil and stones due to ubiquitous uranium and radium in them, thus increasing the airborne radon concentration. The radioactivity in soils is related to radioactivity in the rocks from which the soil is formed. In the present investigation, the radon emanated from soil and stone samples collected from different locations of Aravali range of hills in the Haryana state of Northern India has been estimated. For the measurement of radon concentration emanated from these samples, alpha-sensitive LR-115 type II plastic track detectors have been used. The alpha particles emitted from the radon form tracks in these detectors. After chemical etching the track density of registered tracks is used to calculate radon concentration and exhalation rates of radon using required formulae. The radon concentration in stone samples collected from Aravali range of hills varied from 729 Bq m[-3] to 1958 Bq m[-3] with an average of 1440 +/- 134 Bq m[-3] whereas it varied from 806 Bq m[-3] to 1325 Bq m[-3] with an average of 1040 +/- 101 Bq m[-3] in case of soil samples. Based upon the data, the mass and the surface exhalation rates of radon emanated from them have also been calculated. The measurements indicate normal to some higher levels of radon concentration emanated from the samples collected from Aravali range of hills of north India

Seasonal variation of radon, thoron and their progeny levels in dwellings of Haryana and Western Uttar Pradesh

Radon and thoron are invisible, odorless, heavy and radioactive gases which are ubiquitously present in dwellings and in the environment. In the present work, seasonal variation of indoor radon, thoron and their progeny concentrations has been studied in the dwellings of industrially polluted cities in District Faridabad, Haryana and District Mathura in Uttar Pradesh. LR-115, Type-II [Kodak Pathe, France], peelable, plastic track detectors commonly known as solid state nuclear track detectors [SSNTDs] were used to measure the radon thoron concentration over long integrated times. The measurements were carried out in the mixed field of radon and thoron and the detectors were exposed for about 90 days. The average value of radon and thoron concentration in the dwellings varied from 23.5 Bq/m[3] to 65.2 Bq/m[3] and 9.8 Bq/m[3] to 18.7 Bq/m3 respectively in different seasons. The average annual exposure and annual effective dose in living rooms due to radon and thoron progeny was estimated to be 0.195 WLM [working level month] and 0.74 mSv respectively. The average life time fatality risk of lung cancer from the chronic radon and thoron progeny exposure was estimated to be 5.8 ' 10[-3] [0.58%]. The seasonal variations of measured radon levels in the environment of LPG bottling plant, radon-thoron levels and inhalation dose due to radon and thoron and their progeny in dwellings indicate that the levels were higher in winter [October to January] than in summer [April to July]

Alpha radioactivity in Indian cement samples

The essential constituents of cements like lime, silica and alumina are derived from earth's crust in which radioactive elements like uranium, thorium etc are also present in varying amounts almost everywhere. These two elements are considered as the parent elements of uranium and thorium radioactive decay series in which radon and thoron are produced respectively as decay products. In the present study the samples of ordinary Portland cement [OPC], Portland pozzolana cement [PPC] and some other cementious finishing materials like white cement, Plaster of Paris [POP], cement putty etc were collected and analysed for radium and radon concentrations along with radon exhalation rates. Alpha sensitive LR-115 Type II plastic track detectors commonly known as "Solid State Nuclear Track Detectors" were used to measure the radium and radon concentration. The alpha particles emitted from the radon causes the radiation damaged tracks. The Chemical etching in NaOH at 60°C for about 90 minutes was done to reveal these latent tracks, which were then scanned and counted by an optical microscope of suitable magnification. By calculating the track density of registered tracks, the radon and radium concentrations along with exhalation rate of radon, were determined using required formulae. The radon and radium concentration in various brands of cements found to vary from 333 +/- 9.9 to 506 +/- 13.3 Bq m[-3] and from 3.7 +/- 0.1 to 5.6 +/- 0.2 Bq kg[-1] while in various cementious finishing materials used in the construction, these were found to vary from 378 +/- 19.7 to 550 +/- 9.8 Bq m[-3] and from 4.2 +/- 0.2 to 6.1 +/- 0.1 Bq Kg[-1], respectively. Based on the data the mass and surface exhalation rates were also calculated. The measurements indicate that there is marginal variation of the concentration of radium and radon in various brands of cements in India with lower levels in the cement samples having red oxide and higher levels in fly ash based cement samples but overall concentration levels of radon and radium are lower than that of average global values