Flexible alpha camera for detecting plutonium contamination

Morishita, Yuki   ; Yamamoto, Seiichi*; Izaki, Kenji ; Kaneko, Junichi* ; Nemoto, Norio

Nuclear fuel materials, such as uranium and plutonium (Pu), are handled at nuclear fuel facilities. There are a contamination source of Pu in tight spaces that cannot be directly measured by a ZnS(Ag) scintillation detector, such as interspace between a glovebox window and a platform, pipe flange, port cover of vinyl bag, and filter interspaces. Therefore, we developed a new imaging detector called a flexible alpha camera that enables to identify the Pu contamination for tight spaces at work sites. The thickness of the flexible alpha camera was only 1/5 of the ZnS(Ag) scintillation detector, and its efficiency for 4-pi direction was 42.7% for 5.5-MeV alpha particles. Minimal detectable activity (MDA) was 0.014 Bq. Four types of PuO sample, removed from a duct, Bag-In/Bag-Out port, glovebox glove, and vinyl sheet, were measured by the flexible alpha camera and the PuO particle was automatically identified. Using the flexible alpha camera, the Pu contamination source can be quickly detected, preventing the spread of contamination.