title: Long-term measurements of residential radon, thoron, and thoron progeny concentrations around the Chhatrapur placer deposit, a high background radiation area in Odisha, India.
abstract: The Chhatrapur placer deposit is found in a high background radiation area which has been recently identified on the southeastern coast of India. Previously, some geochemical studies of this area were carried out to assess external dose from radionuclides-bearing heavy mineral sands. In this study, radon, thoron and thoron progeny concentrations were measured in about 100 dwellings during three seasons (autumn-winter, summer, and rainy) in a 10- to 12-month period and annual doses due to inhalation of them were evaluated. The measurements were made by passive-type radon-thoron discriminative detectors and thoron progeny detectors in which solid state nuclear track detectors were deployed. The results show that radon and thoron concentrations differ by one order of magnitude depending on exposure periods, while thoron progeny concentration is nearly constant throughout the year. Since thorium-rich sand is distributed in the studied area, exposure to thoron is equal to, or exceeds, exposure to radon and is not negligible for dose evaluation. Based on the measurements, doses due to inhalation of radon and thoron are evaluated as 0.1-1.6 mSv y-1and 0.2-3.8 mSv y-1, respectively. The total dose is 0.8-4.6 mSv y-1, which is the same order of magnitude as the worldwide value.
authors.affiliation: Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Omori
authors.affiliation: Department of Physics, H.N.B. Garhwal University, Badshahi Thaul Campus, Tehri Garhwal 249199, India.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Prasad
authors.affiliation: Institute of Radiation Emergency Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan.
authors.forename: Atsuyuki
authors.initials: A
authors.lastname: Sorimachi
authors.affiliation: Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Sarata Kumar
authors.initials: SK
authors.lastname: Sahoo
authors.affiliation: Research Center for Radiation Protection, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Health Physics Unit (EAD, BARC), Indian Rare Earths Limited, Odisha 761 045, India.
authors.forename: Devulapalli
authors.initials: D
authors.lastname: Vidya Sagar
authors.affiliation: Department of Physics, H.N.B. Garhwal University, Badshahi Thaul Campus, Tehri Garhwal 249199, India.
authors.forename: Rakesh Chand
authors.initials: RC
authors.lastname: Ramola
authors.affiliation: Institute of Radiation Emergency Medicine, Hirosaki University, 66-1 Hon-cho, Hirosaki, Aomori 036-8564, Japan. Electronic address: tokonami@hirosaki-u.ac.jp.
authors.forename: Shinji
authors.initials: S
authors.lastname: Tokonami
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis; D001417:Background Radiation; D007194:India; D011834:Radiation Monitoring; D011886:Radon / Q000032:analysis*
chemical_list: D000396:Air Pollutants, Radioactive; D011886:Radon
keywords: Ambient gamma dose rate; External dose; High background radiation area; Internal dose; Radon; Thoron