Development of remote sensing technique using radiation-resistant optical fibers to survey in-vessel for fuel debris

Ito, Chikara   ; Ito, Keisuke; Naito, Hiroyuki; Nishimura, Akihiko  ; Oba, Hironori  ; Sekine, Takashi ; Wakaida, Ikuo  

A high-radiation resistant optical fiber has been developed in order to investigate the interiors of the reactor pressure vessels and the primary containment vessels of the Fukushima Daiichi Nuclear Power Station. We have been developed a radiation resistant optical fiber, which consists of 1,000 ppm hydroxyl doped pure silica core and fluorine doped pure silica clad. The number of the core of image fibers has been increased from 2,000 to 22,000 of the practical use level. The transmissive rate of an infrared image was not affected after the irradiation of 1 MGy. The spatial resolution of the view scope by means of the image fiber was not changed between before and after irradiation. We have proposed the concept of applicability of the probing system that consists of view scope, remote ultimate analysis by laser induced breakdown spectroscopy and radiation monitor using the radiation-resistant optical fibers.