砂浜–砂丘系における自然γ線の線量率分布—鳥取砂丘の事例—

Susumu Minato; 湊  進; Tadashi Ikeda; 池田 正

doi:10.3769/radioisotopes.66.227

砂浜–砂丘系における自然γ線の線量率分布—鳥取砂丘の事例—Distribution of Natural γ Ray Dose Rates in a Beach-Dune System —A Case Study of the Tottori Dune—

湊進¹，池田正²Susumu Minato¹, Tadashi Ikeda²

¹ 放射線地学研究所Radiation Earth Science Laboratory ◇ 461–0024　愛知県名古屋市東区山口町9–6 ◇ 9–6 Yamaguchi-cho, Higashi-ku, Nagoya-shi, Aichi Pref. 461–0024, Japan

² 宇陀ジオサークルUda Geoscience Club ◇ 633–0241　奈良県宇陀市榛原下井足1415 ◇ 1415 Shimoidani, Haibara, Uda-shi, Nara Pref. 633–0241, Japan

受付日：2017年1月16日Received: January 16, 2017

受理日：2017年2月24日Accepted: February 24, 2017

発行日：2017年6月15日Published: June 15, 2017

鳥取県鳥取市にある鳥取砂丘海岸の砂浜及びそれに続く砂丘上94地点で自然γ線の線量率を測定した。線量率は汀線から砂浜終端部にかけて漸増し，斜面と砂丘全域でほぼ一定の値を示した。スペクトル測定の結果，カリウム及びウラン濃度は砂浜と砂丘でほぼ同じレベルであったが，トリウム濃度は砂丘の方が高い値であった。以前に測定した遠州灘海岸にある三つの砂丘の事例と比較し，砂浜–砂丘系における自然γ線の線量率分布に関して個々の砂丘の特異性と共通性について述べた。

Natural γ ray dose rates were measured at 94 points in the Tottori Dune coast located in Tottori City, Tottori Prefecture. The dose rate increased gradually from the shoreline to the end of the beach, and revealed an approximately constant value on the slope and the entire area of the dune. As a result of spectrum measurements there, although the concentrations of both potassium and uranium in the beach amounted to almost the same levels as those in the dune, the concentrations of thorium in the dune were high compared to those in the beach. The peculiarity and commonality in natural γ ray dose rate distribution in each beach-dune system were described by comparing with the cases of three dunes in the Enshu-nada coast measured so far.

Key words: natural γ ray; dose rate; Tottori dune; beach

RADIOISOTOPES

資料Materials (Data)

砂浜–砂丘系における自然γ線の線量率分布—鳥取砂丘の事例—Distribution of Natural γ Ray Dose Rates in a Beach-Dune System —A Case Study of the Tottori Dune—