228Ra/226Ra activity ratio in groundwater around Mount Fuji, Japan Tomoko Ohta, Yasunori Mahara, Kimio Miyakawa, Takumi Kubota, Keiko Tagami and Jun Sato EPJ Web of Conferences, 24 (2012) 03003 Published online: 04 April 2012 DOI: 10.1051/epjconf/20122403003