Basic study of one-dimensional optical fiber based radiation distribution sensing by wavelength spectroscopy

Terasaka, Yuta   ; Watanabe, Kenichi*; Uritani, Akira*; Hanai, Tetsuya*; Sato, Yuki  ; Torii, Tatsuo  ; Wakaida, Ikuo  

For the reduction of the external dose of workers in the process of Fukushima Daiichi Nuclear Power Station (1F) decommissioning and to propose an effective decontamination plan, it is necessary to grasp the distribution of locally existing hotspots. A one-dimensional radiation distribution measurement system applying time-of-flight method to scintillating optical fiber has been widely applied after the 1F accident, but in a high dose rate environment such as 1F reactor building, a pile-up of signal and chance-coincidence effect of a sensor is a problem. Therefore, as an integral-type measurement method that can avoid problems such as pile-up, we propose a reverse-estimation method which measures the wavelength spectrum at the fiber edge and estimates the incident position of radiation to the fiber using the fact that the attenuation length of light depends on the wavelength.