Study of Radon and Thoron exhalation from soil samples of different grain sizes. (March 2018)

• Record Type: Journal Article
• Authors: Chitra, N.; Danalakshmi, B.; Supriya, D.; Vijayalakshmi, I.; Sundar, S. Bala; Sivasubramanian, K.; Baskaran, R.; Jose, M.T.
• Is Part Of: Applied radiation and isotopes. Volume 133(2018:Mar.)
• Page Start: 75
• Page End: 80
• Publication Date: 2018-03
• Subjects: Radon -- Thoron -- Exhalation -- Emanation -- Emanation factor -- Grain size; Radiology -- Periodicals; Radiation -- Industrial applications -- Periodicals; Nuclear chemistry -- Periodicals; Internet resource; Periodical; 660.298
• DOI: 10.1016/j.apradiso.2017.12.017
• Languages: English
• ISSNs: 0969-8043

Abstract

Abstract: The exhalation of radon ( 222 Rn) and thoron ( 220 Rn) from a porous matrix depends on the emanation of them from the grains by the recoil effect. The emanation factor is a quantitative estimate of the emanation phenomenon. The present study is to investigate the effect of grain size of the soil matrix on the emanation factor. Soil samples from three different locations were fractionated into different grain size categories ranging from <0.1 to 2 mm. The emanation factors of each of the grain size range were estimated by measuring the mass exhalation rates of radon and thoron and the activity concentrations of 226 Ra and 232 Th. The emanation factor was found to increase with decrease in grain size. This effect was made evident by keeping the parent radium concentration constant for all grain size fractions. The governing factor is the specific surface area of the soil samples which increases with decrease in grain size Highlights: To investigate the effect of grain size of the soil matrix on the emanation factor. The grain size ranges considered for the study - <0.1 mm, 0.1–0.2 mm, 0.2–0.4 mm, 0.4–0.8 mm, 0.8–2 mm, >2 mm. The emanation factors were estimated by measuring the mass exhalation rates of radon and thoron and the concentrations of 226 Ra and 232 Th. It was inferred that the emanation factor increases with increase in the specific surface area which was estimated by the BET technique. The effect of grain size was clearly brought out by fixing the activity concentration of 226 Ra for all grain size ranges.