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Distribution characteristics of natural radionuclides at some spa districts in Japan
International Congress Series 1276 (2005) 295 – 296
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Distribution characteristics of natural radionuclides at some spa districts in Japan T. Kogaa,*, T. Takemuraa, S. Nojiria, H. Morishimaa, M. Inagakia, Y. Tanakaa, M. Mifuneb a
Kinki University Atomic Energy Research Institute, 3-4-1, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan b Former Okayama Univ., Japan
Abstract. In Japan, there are many high-level natural radiation areas such as Masutomi spa (Yamanashi pref.), Misasa spa (Tottori pref.), Ikeda spa (Shimane pref.), and Tamagawa spa (Akita pref.), etc. The Uranium and thorium decay series and K-40 are widely distributed as the sources of terrestrial radiation. Their concentrations are influenced by geological features and are nonuniform. We carried out a study of the behavior and distribution of natural radionuclides in the surrounding soils of high-level natural radiation spa areas by g-ray energy spectrometry using a Ge(INT) diode detector. It was found that the Pb-212(Th)/Pb-214(U) ratios fluctuated widely in the same areas, of which Tamagawa spa and Masutomi spa were typical. D 2004 Elsevier B.V. All rights reserved. Keywords: Natural radionuclide; Masutomi spa; Tamagawa spa; Soil; g-Ray spectrometry; Pb-212(Th)/Pb-214(U) ratio
1. Introduction In Japan, there are many high-level natural radiation areas such as Masutomi spa (Yamanashi pref.), Misasa spa (Tottori pref.), Ikeda spa (Shimane pref.), and Tamagawa spa (Akita pref.), etc. The Uranium and thorium decay series and K-40 are widely distributed as the sources of terrestrial radiation. Their concentrations are influenced by geological features and are non-uniform. We carried out a study of the behavior and distribution of natural nuclides in the environmental soils at these areas by g-ray energy spectrometry using a Ge diode detector. 2. Materials and methods We measured the Rn-222 concentrations in the air and water at spa areas in Japan using the Pico-rad detectors and a liquid scintillation spectrometer. Air samples were taken over a * Corresponding author. Tel.: +81 6 6721 2332x4407; fax: +81 6 6721 3743. E-mail address: [email protected] (T. Koga). 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2004.11.085
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T. Koga et al. / International Congress Series 1276 (2005) 295–296
Fig. 1. Th/U concentration ratio of soils at some spa districts in Japan.
24-h period and then mixed with a scintillator to measure the concentration of Rn-222, while water samples were mixed directly with an equal amount of scintillator to measure the same. Soil samples were collected from the spa areas, dried, sieved and enclosed in 100-ml plastic containers (U-8). These containers were sealed, kept for one month to attain radioactive equilibrium between various decay products in the Th-232 and U-238 series and measured for approximately 105 s, using a Ge(INT) diode detector system. The spectrum was analysed with reference to the following photo-peaks: 239 keV of Pb212(Th), 352 keV of Pb-214(U), and 1461 keV of K-40. 3. Results and discussions The Pico-rad method for measuring concentrations of Rn-222 in air and water is suitable for both the measuring of many samples, and drawing a concentration distribution map. The maximum Rn-222 concentrations in spring water and air were 20 kBq/l and 3.3 kBq/m3 indoors at Masutomi, 9.7 kBq/l and 690 kBq/m3 outdoors at Ikeda and 4.8 kBq/l and 4.4 kBq/m3 indoors at Misasa, respectively. A total of 166 soil samples from spa areas were analysed. These concentrations of Pb212(Th) and Pb-214(U) were calculated in Bq/kg. The concentrations of some samples collected at control areas in Osaka pref. are nearly the same as the world average [1]. The maximum Pb-212(Th) concentration of soil samples showed 33.5 kBq/kg and Pb-214(U) 2.7 kBq/kg in the Tamagawa spa area, and Pb-212 8.8 kBq/kg and Pb-214 1.5 kBq/kg in the Masutomi spa area, respectively. The world averages of Th-232 and U-238 are 30 and 35 Bq/ kg, respectively [1]. These concentrations in the Tamagawa and Masutomi spa areas were remarkably higher than those in the control areas. Of the mean Pb-212(Th)/Pb-214(U) ratios in the Tamagawa spa areas, one was 0.018 in which a large number of U series nuclides were contained, while that of the other was 11 (Fig. 1). It was typically found that the Pb-212(Th)/ Pb-214(U) ratios in the Tamagawa spa and Masutomi spa areas fluctuated widely. There are areas made up of the accumulate-piled soils of aqueous uranium and radium compounds. Reference [1] UNSCEAR 2000 Report, II Terrestrial Radiation (2000).
www.ics-elsevier.com
Distribution characteristics of natural radionuclides at some spa districts in Japan T. Kogaa,*, T. Takemuraa, S. Nojiria, H. Morishimaa, M. Inagakia, Y. Tanakaa, M. Mifuneb a
Kinki University Atomic Energy Research Institute, 3-4-1, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan b Former Okayama Univ., Japan
Abstract. In Japan, there are many high-level natural radiation areas such as Masutomi spa (Yamanashi pref.), Misasa spa (Tottori pref.), Ikeda spa (Shimane pref.), and Tamagawa spa (Akita pref.), etc. The Uranium and thorium decay series and K-40 are widely distributed as the sources of terrestrial radiation. Their concentrations are influenced by geological features and are nonuniform. We carried out a study of the behavior and distribution of natural radionuclides in the surrounding soils of high-level natural radiation spa areas by g-ray energy spectrometry using a Ge(INT) diode detector. It was found that the Pb-212(Th)/Pb-214(U) ratios fluctuated widely in the same areas, of which Tamagawa spa and Masutomi spa were typical. D 2004 Elsevier B.V. All rights reserved. Keywords: Natural radionuclide; Masutomi spa; Tamagawa spa; Soil; g-Ray spectrometry; Pb-212(Th)/Pb-214(U) ratio
1. Introduction In Japan, there are many high-level natural radiation areas such as Masutomi spa (Yamanashi pref.), Misasa spa (Tottori pref.), Ikeda spa (Shimane pref.), and Tamagawa spa (Akita pref.), etc. The Uranium and thorium decay series and K-40 are widely distributed as the sources of terrestrial radiation. Their concentrations are influenced by geological features and are non-uniform. We carried out a study of the behavior and distribution of natural nuclides in the environmental soils at these areas by g-ray energy spectrometry using a Ge diode detector. 2. Materials and methods We measured the Rn-222 concentrations in the air and water at spa areas in Japan using the Pico-rad detectors and a liquid scintillation spectrometer. Air samples were taken over a * Corresponding author. Tel.: +81 6 6721 2332x4407; fax: +81 6 6721 3743. E-mail address: [email protected] (T. Koga). 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2004.11.085
296
T. Koga et al. / International Congress Series 1276 (2005) 295–296
Fig. 1. Th/U concentration ratio of soils at some spa districts in Japan.
24-h period and then mixed with a scintillator to measure the concentration of Rn-222, while water samples were mixed directly with an equal amount of scintillator to measure the same. Soil samples were collected from the spa areas, dried, sieved and enclosed in 100-ml plastic containers (U-8). These containers were sealed, kept for one month to attain radioactive equilibrium between various decay products in the Th-232 and U-238 series and measured for approximately 105 s, using a Ge(INT) diode detector system. The spectrum was analysed with reference to the following photo-peaks: 239 keV of Pb212(Th), 352 keV of Pb-214(U), and 1461 keV of K-40. 3. Results and discussions The Pico-rad method for measuring concentrations of Rn-222 in air and water is suitable for both the measuring of many samples, and drawing a concentration distribution map. The maximum Rn-222 concentrations in spring water and air were 20 kBq/l and 3.3 kBq/m3 indoors at Masutomi, 9.7 kBq/l and 690 kBq/m3 outdoors at Ikeda and 4.8 kBq/l and 4.4 kBq/m3 indoors at Misasa, respectively. A total of 166 soil samples from spa areas were analysed. These concentrations of Pb212(Th) and Pb-214(U) were calculated in Bq/kg. The concentrations of some samples collected at control areas in Osaka pref. are nearly the same as the world average [1]. The maximum Pb-212(Th) concentration of soil samples showed 33.5 kBq/kg and Pb-214(U) 2.7 kBq/kg in the Tamagawa spa area, and Pb-212 8.8 kBq/kg and Pb-214 1.5 kBq/kg in the Masutomi spa area, respectively. The world averages of Th-232 and U-238 are 30 and 35 Bq/ kg, respectively [1]. These concentrations in the Tamagawa and Masutomi spa areas were remarkably higher than those in the control areas. Of the mean Pb-212(Th)/Pb-214(U) ratios in the Tamagawa spa areas, one was 0.018 in which a large number of U series nuclides were contained, while that of the other was 11 (Fig. 1). It was typically found that the Pb-212(Th)/ Pb-214(U) ratios in the Tamagawa spa and Masutomi spa areas fluctuated widely. There are areas made up of the accumulate-piled soils of aqueous uranium and radium compounds. Reference [1] UNSCEAR 2000 Report, II Terrestrial Radiation (2000).