Exploration of radioactive source distribution inside the Fukushima Daiichi Nuclear Power Station Unit 3 reactor building using a newly developed optical fiber radiation sensor based on photon time-of-flight and wavelength-resolving analysis

Terasaka, Yuta   ; Sato, Yuki  

We are working on the development and field application of radiation detectors based on optical fibers, aimed at understanding the contamination situation inside and outside the Fukushima Daiichi Nuclear Power Station (FDNPS) reactor buildings. In particular, we are developing sensors that focus on the high sensitivity and characteristic response of optical fibers to beta rays, especially for measuring Sr/Y. This nuclide is beta emitters and is not well-mapped compared to gamma-emitting nuclides such as Cs. Here, we have developed two new methods: a wavelength-resolving analysis method that utilizes the wavelength dependency of light attenuation inside optical fibers to obtain information on the incident position of radiation, and a Cherenkov TOF (Time-of-Flight) method that uses the energy dependency of the Cherenkov radiation angle inside optical fibers for nuclide discrimination.