Colloquium of NH group, Kyoto Univ.

Toshiyuki Gogami

2015/2/23

Paper introduction of:

Cosmic-ray muon radiography of UO2 fuel assembly

T.Sugita et al., Journal of Nuclear Science and Technology 51, 7-8 (2014) 1024-1031

再稼働しつつある原発

3.11 The accident of Fukushima NPP

①②③④

Need information of melted fuel for decommissioning of reactor

Difficult to access due to too high radiation level

Muon radiography

ミュオン透過法による炉内調査の開始‼

IRID ( 技術研究組合 国際廃炉研究開発機構 ) R&D topics; 2015/2/12

Muon radiography

1. Transmission method[ Energy loss Stop ]Mane, Egyptian pyramid, temple gate, volcano, caverns etc.

2. Scattering (displacement) method[ Coulomb scattering Scattering angle (displacement) ]Invented at Los Alamos National Laboratory

H.K.M.Tanaka et al., Earth Planets Space 62 (2010) 119-129

Transmission method

K.Takamatsu et al., Annals of Nuclear Energy 78 (2015) 166-175

At High-Temperature engineering Test Reactor (HTTR)

Transmission method

K.Takamatsu et al., Annals of Nuclear Energy 78 (2015) 166-175

At High-Temperature engineering Test Reactor (HTTR)

Scattering method

𝐿𝑖=𝑑𝑖 tan 𝜃𝑖(1+ tan❑𝜃𝑖0)

Depending on the radiation length !!

Paper which will be introduced

Toshiba Nuclear Critical Assembly

Experimental setup

Mini Muon Tracker (MMT) system576 sealed drift tubes (5 cm diameter, 0.9 mm aluminum wall)1.2 m lengthxxyyxxyyxxyy (12 layers)

MMT1MMT2

C.L.Morris et al., Applied Physics Letters 104 (2014) 024110

30 days of data taking

Cross section of NCA obtained by the scattering method

Results

4 cm40 cm

20 cm

4 cm

±2 cmで一致

Result comparison with Geat4 simulation

Application for Fukushima Daiichi

Geant4 simulation model

10 m

10 m

Challenge for the high rate gamma-ray background

Geant4 simulation model

10 m

10 m

20 μSv/h1000 μSv/h

FPGA trigger 50 μSv/h

7.5 cm thickness steel expects to be needed.

Results of the simulation

50% melted core + 60 cm diameter debris Clearly seen !!

Summary

Muon radiography

• Can be used for nuclear reactor investigation with resolution of 3 cm.

• Investigation of Fukushima Daiichi • Transmission method (1号機、 2015/2-)• Scattering method (2号機、 2015/10-)