Development of -ray visualization survey meter in high gamma and neutron background environment

Tsubota, Yoichi   ; Kobayashi, Kenji; Ishii, Tatsuya; Hirato, Misaki ; Shioya, Satoshi; Nakagawa, Takahiro 

In the decommissioning of the Fukushima Daiichi Nuclear Power Station (FDNPS, 1F), workers are removing structures from inside the buildings, monitoring radioactive contamination, and decontaminating inside the buildings. For the measurement of contamination of suit surfaces of workers, we have developed a hand-held survey meter that can measure and visualize surface radioactive contamination of -nuclides in a high / -ray background environment. In order to selectively measure -nuclides, we designed and built a prototype hand-held survey meter for -rays, which consists of a thin-film ZnS:Ag scintillator, a multi-anode photomultiplier tube (MA-PMT), individual amplification and counting circuits for each channel of the MA-PMT. Based on the result of -ray counting, the developed device is capable of counting the -radiation beyond 2.110 cpm. In the -ray response test, there was no -ray response even when the detector was in close proximity to a high intensity source; The dose rate was estimated to be more than 1 Sv/h. In the future, we plan to reduce the weight and size of the device, as well as improve the usability of the device through actual testing in contaminated environments.