Preliminary experiment for internal structure visualization of HTTR using cosmic ray muons

Takegami, Hiroaki ; Takamatsu, Kuniyoshi  ; Ito, Chikara   ; Hino, Ryutaro; Suzuki, Keiichi*; Onuma, Hiroshi*; Okumura, Tadahiko*

One of the important problems for controlling of the Fukushima Daiichi Nuclear Power Plant is removing of fuel debris. As this preparation, the nondestructive inspection method for grasping the position of fuel debris is required. Therefore, we focused on a nondestructive inspection method using cosmic-ray muons. In this study, the applicability of this method for internal visualization of reactor was confirmed by preliminary test of internal visualization of High Temperature Engineering Test Reactor (HTTR). By using cosmic-ray muons, major components in the HTTR, such as concrete wall and reactor core, can be observed from the outside of a containment vessel. From the results, it appears that the inspection method with muons is a candidate method for searching the fuel debris in a reactor. Based on the results, we also proposed some improvements of this system for inspection at the Fukushima Daiichi Nuclear Power Station.