Development of a high sensitivity detector for Radium in water and a study of Rajium removal.

Research Project

Project/Area Number	07554003
Research Category	Grant-in-Aid for Scientific Research (A)
Allocation Type	Single-year Grants
Section	展開研究
Research Field	素粒子・核・宇宙線
Research Institution	University of Tokyo
Principal Investigator	KAJITA Takaaki Univ.of Tokyo, ICRR,Associate Professor, 宇宙線研究所, 助教授 (40185773)
Co-Investigator(Kenkyū-buntansha)	NISHIMURA Syuuichi Organo Co., Senior Engineer, 主任技師(研究職) TAKEUCHI Yasuo Univ.of Tokyo, ICRR,Research Associate, 宇宙線研究所, 助手 (60272522) MIYANO Kazumasa Niigata Univ., Faculty of Science, Professor, 理学部, 教授 (10011529) TASAKA Shigeki Gifu Univ., Faculty of Education, Assosiate Professor, 教育学部, 助教授 (60155059) 渡辺靖志東京工業大学, 理学部, 教授 (40126199)
Project Period (FY)	1995 – 1997
Project Status	Completed (Fiscal Year 1997)
Budget Amount *help	¥14,600,000 (Direct Cost: ¥14,600,000) Fiscal Year 1997: ¥2,600,000 (Direct Cost: ¥2,600,000) Fiscal Year 1996: ¥4,800,000 (Direct Cost: ¥4,800,000) Fiscal Year 1995: ¥7,200,000 (Direct Cost: ¥7,200,000)
Keywords	Radium / pure water / Radon / 太陽ニュートリノ
Research Abstract	A high sensitivity detector for Radium in water was developed. This detector measures Radons which are the decay product of Rajium. Radons are extracted from the water into the air by the bubbling method. The volume of the sample water is 700 liters. And a 70-liter Radon detector for air is used to detect Radons. The sensitivity of the detector to the Radium concentration in water is about 1mBq/m^3. We measured the Radium concentration of the pure water in the 50,000 ton Super-Kamiokande detector. The measured value was 0.9 (]SY.+-。[) 0.1 (stat.) (]SY.+-。[) 0.1 (syst.) mBq/m<@D13@>D1, or equivalently, 68.4 (]SY.+-。[) 6.4 (]SY.+-。[) 7.7Ra/cm<@D13@>D1. This level of Radium concentaration was the goal when we started this research. We also studied what elements used in the water purification sustem are capable of removing Radium efficiently. This measurement was carried out using the kamiokande water which contained more than 100 times more Radium. We observed that Radium can be removed efficintly by Reverse-Osmosis membrane, Ultra-filter and activated charcoal.