Detection of alpha particle emitters originating from nuclear fuel inside reactor building of Fukushima Daiichi Nuclear Power Plant

福島第一原子力発電所の燃料起因の線放出核種の検知

森下 祐樹   ; 鳥居 建男  ; 宇佐美 博士; 菊地 弘幸*; 宇津木 弥*; 高平 史郎*

Morishita, Yuki; Torii, Tatsuo; Usami, Hiroshi; Kikuchi, Hiroyuki*; Utsugi, Wataru*; Takahira, Shiro*

We measured alpha emitters obtained from a reactor building in the Fukushima Daiichi Nuclear Power Plant (FDNPP) by using an alpha particle imaging detector. For developing the detector, we used a verythin (0.05-mm-thick) a cerium-doped Gd(Ga,Al)O (Ce:GAGG) scintillator and silicon photomultiplier (SiPM) arrays as the photodetector. The floor of the reactor building in FDNPP was wiped off by using smear papers, and the radioactivity of these papers was measured by the alpha particle imaging detector. The alpha spectrum was in the energy range of 5-6 MeV, which corresponds to the alpha particle energy of Pu (5.5 MeV). Moreover, the peak of Am was identified by gamma spectrum measurement. Based on these results, we report actual findings of alpha emitters in the FDNPP reactor buildings originating from nuclear fuels.