Imaging the inner structure of a nuclear reactor by cosmic muon radiography

Hirofumi Fujii,Shogo Hashimoto,Shuji Tanaka,Kotaro Satoh,Kazuyuki Sato,Yu Takahashi,Kohei Hayashi,Shin-Hong Kim,Fumihiko Takasaki,Kazuki Takahashi,Kazuhiko Hara,Atsuto Suzuki,Fumiaki Ito,Hidekazu Kakuno,Satoru Yamashita,Kanetada Nagamine,Hideyo Kodama,Takayuki Sumiyoshi

doi:10.1093/ptep/ptz040

Abstract

We studied the inner structure of the nuclear reactor of the Japan Atomic Power Company (JAPC) at Tokai, Japan, by the muon radiography. In this study, muon detectors were placed outside of the reactor building. By detecting cosmic muons penetrating through the wall of the reactor building, we could successfully identify the objects such as the containment vessel, pressure vessel, and other structures of the reactor. We also observed a concentration of heavy material which can be attributed to the nuclear fuel assemblies stored in the nuclear fuel storage pool.

Highlights

The nuclear power reactors at the Fukushima Daiichi, Japan, were seriously damaged by the gigantic earthquake followed by Tsunami in March, 2011
In order to demonstrate the usefulness of the cosmic muon radiography technology in visualizing the inner structure of the reactor, we made a measurement of cosmic muons penetrating through the nuclear reactor of the Japan Atomic Power Company (JAPC), Tokai, Ibaraki, Japan
We investigated the inner structure of the nuclear reactor at the JAPC, Tokai, Ibaraki, Japan, with the muon radiography system by using the cosmic muons

Summary

Introduction

The nuclear power reactors at the Fukushima Daiichi, Japan, were seriously damaged by the gigantic earthquake followed by Tsunami in March, 2011. It was proposed to use cosmic muons to diagnose the reactor status from outside of the reactor building by Cosmic Muon Radiography [1], [2]. It is to measure millions of cosmic muons which penetrate the reactor and to figure out detailed structure of the reactor. In order to demonstrate the usefulness of the cosmic muon radiography technology in visualizing the inner structure of the reactor, we made a measurement of cosmic muons penetrating through the nuclear reactor of the Japan Atomic Power Company (JAPC), Tokai, Ibaraki, Japan. The measurement was made from February 2012 to December 2013 During this period, the reactor ceased generating electricity and nuclear fuels were taken out and stored in the storage water pool (NFSP). This report describes the impact of this addition: we succeeded in 3D imaging of the cluster of fuel objects placed in the NFSP

The Muon Detection System

Evaluation of Mass of the Heavy Object in the NFSP

Conclusions