1. Muon Tomography Project Characterising Encapsulated Nuclear Waste using Cosmic-ray Muon Tomography Muon Tomography Project Dr. David F. Mahon University of Glasgow 3 rd European Nuclear Physics Conference Nuclear Physics Applications I 31 st August 2015

2. 2 The Sellafield Ltd. MT Project: Aims & Objectives Multi-million pound collaboration with industry (National Nuclear Laboratory & Sellafield Ltd.), which began in 2009 Application of detector development and ‘conventional’ nuclear physics research performed by the University of Glasgow at HERMES @ DESY, A2 @ MAMI, Jefferson Lab etc. Aims to assess the feasibility of using cosmic-ray muons to inspect the contents of 500 litre nuclear waste containers and characterise any remnant nuclear materials stored within A small-scale prototype detector has been constructed and has successfully imaged the contents of a small test barrel A large-scale system is now under development in Glasgow

3. 3 Muon Tomography: Non-invasive Imaging using Cosmic Rays muons detected scattering angle scattering angle Cosmic-ray ‘Muography’ is one of the fastest-growing fields in applied research exploiting the absorption or Coulomb scattering of charged muons through an object Highly-penetrating muons allow the interrogation of large and/or dense shielded objects that cannot be imaged using conventional techniques such as X-rays etc. Absorption RadiographyScattering Tomography imaging plane imaging plane imaging plane

4. 4 1936195519671999 Discovery of the muon at Caltech by Carl David Anderson and Seth Neddermeyer (Phys. Rev. 51, 884) First reported use in radiography by E. P. George in Australia to measure ice thickness above a tunnel (Commonwealth Engineer July 1, 455) Muon radiography used by Nobel Prize winner Luis W. Alvarez to look for hidden chambers in the Second Pyramid of Chephren in Egypt (Science 176, 832) At the Soudan II detector in Minnesota (700m underground), the Moon shadow is imaged using muon flux (Cobb et al., Phys. Rev. D 61, 092002) 1912 The discovery of cosmic-rays by Victor Hess in a hot-air balloon at 5.3km. Awarded the Nobel Prize for Physics in 1936 for his career’s work (Phys. Zeitschr. 13, 1084) Muon Tomography: Key Events, Applications & Dates 2003 Seminal work at Los Alamos on utilising Coulomb scattering of muons to identify high-Z objects for nuclear threat detection (Borozdin et al., Nature 422, 277) Tanaka et al., imaged the density inside the 1944 Usa lava dome with cosmic-ray muon radiography (Geo. Res. Lett. 34, 22311) 2007 First images obtained of encapsulated nuclear waste by the Sellafield MT project in Glasgow (Clarkson et al., JINST 10, P03020) 2014 Zenoni et al., applied the technique to monitoring the structural stability of historical buildings. Here, Palazzo della Loggia, Brescia dating from 1574 (arXiv:1403.1709) 2015 Los Alamos scientists, Toshiba and TEPCO image the interior of the Unit-1 reactor at the stricken Fukushima- Daiichi plant

5. 55 Muon Tomography: European Projects & Applications UK: Legacy Nuclear Waste, Special Nuclear Materials (SNM) detection, Subsurface CO 2 monitoring Italy: Volcanology, SNM detection, cultural heritage, blast furnace monitoring, steel plant safety France: Volcanology, geological applications Germany: Structural integrity applications, blast furnace monitoring Spain: Large-scale applications Hungary: Civil engineering applications Romania: Civil engineering applications Sweden: Spent nuclear fuel assay, blast furnace monitoring Russia: SNM detection, geological applications

6. 66 A Virtual Tour of Sellafield All images and information courtesy of Sellafield Ltd. (www.sellafieldsites.com) Windscale Advanced Gas-Cooled Reactor: Ceased operation in 1981. Currently being de-commissioned. Thermal Oxide Reprocessing Plant: THORP is used for shearing, dissolution and retrieval of uranium and plutonium components of used oxide fuel from both UK and overseas customers. Waste and Magnox Encapsulation Plants: Facility used for processing intermediate level waste (ILW) in a grout matrix within stainless steel drums prior to long term storage. Legacy Waste Silos: These historic facilities currently house Magnox swarf (cladding from fuel elements).

7. 7 Nuclear Waste Encapsulation The encapsulated ILW is stored long-term in product stores on the Sellafield site. Here, the inside of a product store is shown with container ‘stillages’ stacked. Magnox Fuel Elements Uranium fuel surrounded by a magnesium alloy (Magnox) cladding (or swarf). Before reprocessing, irradiated fuel must be stored for at least 180 days in ponds to allow short lived fission products to decay. Fuel Rod Cladding RemovalEncapsulated Swarf The cladding is stripped from the fuel bar in the Fuel Handling Plant. The fuel is then transported to the Magnox Reprocessing Plant. The swarf stripped from the fuel rods is Intermediate Level Waste (ILW). Shown is a cross section view of ILW which has been grouted in cement for long term storage. Long-term Storage of ILW The ILW is stored in 500-litre stainless-steel waste containers (shown here for a test drum with outer section removed) or in 3m 3 boxes. Encapsulated Waste Stores The encapsulated ILW is stored long-term in product stores on the Sellafield site. All images and information courtesy of Sellafield Ltd. (www.sellafieldsites.com)

8. 8 Small-Scale Prototype Technology A small-scale detector system (1:16 scale) has been constructed in Glasgow to verify initial GEANT4 simulations System comprises four tracker modules each with orthogonal layers of 128 BCF-10 scintillating fibres from Saint-Gobain of 2mm pitch with emission peaked at 432nm Per module, two fibres are coupled to a single pixel of a Hamamatsu H8500 MAPMT with correct fibre reconstructed in offline analysis a GEANT4 simulation of the active components of a detector module showing one struck fibre in each plane The scintillation light strikes the glass photocathode of the MAPMT creating a photoelectron (PE) When triggered the charge signals from each anode are read out by ribbon cables to standard QDCs The photoelectron is focused into the chain of 12 dynodes creating a charge at the anode of the struck pixel

9. 9 The system has four modules detector modules: two above and two below the object to be imaged Each module contains scintillating fibres in the x and y directions If we identify the x and y fibre hit, their crossover point is used as the muon hit point From these the incoming and scattered vectors are reconstructed Small-Scale Prototype Imaging

10. 10 These vectors are propagated into the assay volume and their Point of Closest Approach (PoCA) is identified The scattering angle and displacement (2D example shown opposite as θ x and Δx) The Coulomb-scattering probability (denoted λ) is computed for discrete steps along each muon’s trajectory After many muons, the most-likely λ 3D distribution is determined via custom image reconstruction software Small-Scale Prototype Imaging Δx θxθx

11. 11 The Sellafield Ltd. MT Project: Imaging Lead within a Concrete-filled Steel Barrel Small-scale prototype detector: A side-on view of the system with barrel 10mm horizontal tomogram5mm vertical tomogram GEANT4 simulation of test barrel The two innermost detector modules are shown with the barrel, lead and uranium objects to be imaged Test barrel inside detector setup: A stainless-steel, concrete-filled barrel containing lead and uranium samples A. Clarkson et al., JINST 10 (2015), P03020

12. 12 The Sellafield Ltd. MT Project: Imaging Uranium within a Concrete-filled Steel Barrel Small-scale prototype detector: A side-on view of the system with barrel GEANT4 simulation of test barrel The two innermost detector modules are shown with the barrel, lead and uranium objects to be imaged Test barrel inside detector setup: A stainless-steel, concrete-filled barrel containing lead and uranium samples A. Clarkson et al., JINST 10 (2015), P03020 10mm horizontal tomogram5mm vertical tomogram

13. 13 The Sellafield Ltd. MT Project: 3D Visualisation of Encapsulated Nuclear Waste A 3D movie of these experimental results will be shown here during the presentation on the 31 st August

14. 14 In Conclusion... The field of muon tomography is one of the fastest growing in applied physics with applications in national security, nuclear waste characterisation etc. A prototype scintillating-fibre muon detector has been developed at the University of Glasgow to assess the feasibility for this purpose at Sellafield High-Z material detection and discrimination capabilities have been verified in industrial test scenarios to sub- centimetre precision using custom image reconstruction software A full-scale system is being developed in Glasgow for the interrogation industrial 500 litre ILW barrels

15. 15 This research has been undertaken by the Nuclear Physics group at the University of Glasgow in collaboration with the UK National Nuclear Laboratory. On behalf of the project, I would like to acknowledge the funding contribution from the UK Nuclear Decommissioning Authority and Sellafield Ltd., which enabled this research to be undertaken. I would also like to thank the organising committee of EuNPC2015 for the opportunity to present this research in Groningen. Acknowledgements