Development of non-destructive inspection method for on-site observation; Preliminary examination for internal visualization of HTTR

Takegami, Hiroaki ; Terada, Atsuhiko  ; Noguchi, Hiroki  ; Kamiji, Yu; Ono, Masato ; Takamatsu, Kuniyoshi  ; Ito, Chikara   ; Hino, Ryutaro; Suzuki, Keiichi*; Onuma, Hiroshi*; Okumura, Tadahiko*

We focused on a non-destructive inspection method using cosmic-ray muons as a candidate method for observation of internal the reactor from the outside of a reactor building. In this study, the applicability of this method for the reactor investigation was confirmed by a preliminary examination with High Temperature Engineering Test Reactor (HTTR). From the results of this examination, it appears that high density structures, such as the core and concrete walls, were able to observe by using muon telescope with coincidence method from the outside of the pressure vessel. Furthermore, we proposed some improvements of this muon inspection system for on-site investigation at the Fukushima Daiichi NPS.