Investigation of Main Radiation Source above Shield Plug of Unit 3 at Fukushima Daiichi Nuclear Power StationHideo Hiratama, Kenjiro Kondo, Seishiro Suzuki, Yoshihiko Tanimura, Kohei Iwanaga and Hiroshi NagataEPJ Web Conf., 153 (2017) 08010DOI: https://doi.org/10.1051/epjconf/201715308010