Preliminary Experiment for Internal Structure Visualization of HTTR Using Cosmic Ray Muons

Abstract

  One of the important problems in the control of the Fukushima Daiichi Nuclear Power Plant is the removal of fuel debris. As preparation, a nondestructive inspection method for identifying the position of fuel debris is required. Therefore, we focused on a nondestructive inspection method using cosmic-ray muons, which is utilized for ground investigation. In this study, the applicability of this method for internal visualization of the reactor was confirmed by a preliminary test of the internal visualization of the High-Temperature Engineering Test Reactor (HTTR) of Japan Atomic Energy Agency. By using cosmic-ray muons, main components in the HTTR reactor, such as concrete walls and the reactor core, can be observed from the outside of the containment vessel of the HTTR. From the results of the preliminary examination, it appears that the inspection method with muons is promising for searching for fuel debris in a reactor. Based on the results, we also proposed some improvements of this system for its application to inspection at the Fukushima Daiichi Nuclear Power Station.