1. Colloquium of NH group, Kyoto Univ. Toshiyuki Gogami 2015/2/23 Paper introduction of: Cosmic-ray muon radiography of UO 2 fuel assembly T.Sugita et al., Journal of Nuclear Science and Technology 51, 7-8 (2014) 1024-1031

2. 再稼働しつつある原発

3. 3.11  The accident of Fukushima NPP Need information of melted fuel for decommissioning of reactor Difficult to access due to too high radiation level Muon radiography

4. 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

5. 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

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

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

8. Scattering method Depending on the radiation length !!

9. Paper which will be introduced

10. Toshiba Nuclear Critical Assembly

11. Experimental setup Mini Muon Tracker (MMT) system 576 sealed drift tubes (5 cm diameter, 0.9 mm aluminum wall) 1.2 m length xxyyxxyyxxyy (12 layers) MMT1 MMT2 C.L.Morris et al., Applied Physics Letters 104 (2014) 024110 30 days of data taking

12. Cross section of NCA obtained by the scattering method

13. Results ±2 cm で一致

14. Result comparison with Geat4 simulation

15. Application for Fukushima Daiichi Geant4 simulation model 10 m

16. Challenge for the high rate gamma-ray background Geant4 simulation model 10 m 20 μSv/h 1000 μSv/h FPGA trigger  50 μSv/h 7.5 cm thickness steel expects to be needed.

17. Results of the simulation 50% melted core + 60 cm diameter debris  Clearly seen !!

18. 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-)