Characteristics of the Environmental Radon and Thoron in Minamidaito-jima, a Comparatively High Background Radiation Island in Japan
نویسندگان
چکیده
Copyright © 2015 by Hirosaki University. All rights reserved. General survey for the environmental radon and thoron has been performed in Minamidaitojima, Okinawa prefecture, southwestern part of Japan. In situ measurements of the radon and thoron exhalation rates were conducted at a total of 7 points using an accumulation technique with a ZnS(Ag) scintillation detector. The medians of radon and thoron exhalation rates were estimated to be 31 mBq m-2 s-1 and 3,970 mBq m-2 s-1, respectively. The atmospheric radon concentrations were measured at 2 points with an ionization chamber, and the maximum concentration was estimated to be 94 Bq m-3. For the surface soil samples collected at the measurement points of the exhalation rates, arithmetic means for 238U and 232Th series concentration were estimated to be approximately 145 Bq kg-1 dry and 101 Bq kg-1 dry, respectively. These results indicated that the environmental radon and thoron levels in Minamidaito-jima are fairly higher than those of the average of Japan. And it is strongly suggested that the exhalation rates and the concentrations are enhanced mainly due to the surface soil with the relatively high radioactivity.
منابع مشابه
Comparison of Radon (222Rn) and Thoron (220Rn) Gamma Dosimetry in the Environment Using the ORNL Mathematical Phantom
Background: The potential hazards of exposure to radiation from radon have been of great concern worldwide, as it is associated with an increased risk of lung cancer. Radon (222Rn) and its progeny are the main sources of radioactivity in the environment. The half-life of 222Rn (3.82 days) is long enough for it to diffuse into and build up in homes. 220Rn or thoron from the 232Th series, and 219...
متن کاملA study on radon and thoron progeny levels in dwellings in South India
Background: Decay products of radon and thoron present in indoor environment are the most important sources of radiation from natural sources which affect human beings, since general public spend at lest 80% of their time in indoor. Materials and Methods: Air samples were collected for measuring the concentration of radon and thoron daughter products from various indoor environments d...
متن کاملComparative Measurements of Radon Concentration in Soil Using Passive and Active Methods in High Level Natural Radiation Area (HLNRA) of Ramsar
Background: Radon and its daughters are amongst the most important sources of natural exposure in the world. Soil is one of the significant sources of radon/thoron due to both radium and thorium so that the emanated thoron from it may cause increased uncertainties in radon measurements. Recently, a diffusion chamber has been designed and optimized for passive discriminative measurements of rado...
متن کاملCalibration and optimization of a low cost diffusion chamber for passive separated measurements of radon and thoron in soil by Lexan PC SSNTD
Background: Separate radon and thoron measurements in soil are very important in assessment of internal exposure due to inhalation of such radioactive gases. Materials and Methods: In this study, a low cost, small size, passive diffusion chamber has been developed for simple measurement of Radon-222 and Radon-220(Thoron) gases separately in soil. The diffusion chamber consists of two films and ...
متن کاملConcentration of radon, thoron and their progeny levels in different types of floorings, walls, rooms and building materials
Background: Radon, thoron and their progenies are the most important contributions to human exposure from natural sources. Radon exists in soil gas, building materials, Indoor atmosphere etc. Among all the natural sources of radiation dose to human beings, inhalation of radon contributes a lot. The work presented here emphasizes the long term measurements of radon, thoron and their proge...
متن کامل