Imaging in the Nuclear Sector Intelligent Imaging Programme Chancellor’s Hall, University of London 6th November 2013 Gary Bolton

Contents of Talk Introduction to the National Nuclear Laboratory Imaging developments and case studies: ─ RadBall ─ Thermal imaging ─ Muon Tomography ─ Electronic Speckle Pattern Interferometry Imaging opportunity in the nuclear sector – Long term storage of waste Acknowledgements

Role of the NNL

What is RadBall? RadBall consists of a colander-like outer collimator that houses a radiation-sensitive core. RadBall

Hung from a crane Positioned using a manipulator Robotic Deployment system Manual deployment How is RadBall deployed? Deployable Maps the 3D radiation distribution Does not require any power Does not require any communication link Can eliminate radiation exposure to personnel Wide dose range Benefits

How does the RadBall work? Radball Core changes colour when exposed to radiation Amount of colour change is dose dependant Radiation produces discrete tracks Allows location and quantity of radiation to be determined

RadBall

Thermal Imaging Waste management strategy is long-term storage followed by disposal in a deep geological repository Currently 20 ILW/HLW stores in the UK with a further 25 planned or under construction Integrity of packages must be maintained during storage to meet repository CfA

Thermal Imaging Thermal imaging system developed by National Physical Laboratory and Sellafield Ltd Package inspections performed in 2011 Possibility of using hyper spectral multi wavelength analysis to determine corrosion

Muon Tomography University of Glasgow, in partnership with NNL and Sellafield Ltd, is developing a muon tomography system for the non- destructive assay of nuclear legacy waste containers Simulation studies to assess the feasibility of a scintillating- fibre tracker system for use in the identification and characterisation of nuclear materials Identification and characterisation of high atomic number (Z) waste products stored within more dense material. Important to discern between these high-Z materials and objects comprised of other low- or medium-Z materials (e.g. concrete, iron etc.) within a reasonable timescale.

Muon Tomography Simulation to assess various aspects of the detector system prior to construction of prototype 40 mm cubes of 4 different materials Uranium (19), Uranium Oxide (11), Iron (8) and Concrete (2) in an air matrix Images for 1 day, 1 week, 1 month and 1 year

Muon Tomography Comparison between experimental and simulation of U and Pb

Electronic Speckle Pattern Interferometry The UK’s fleet of AGRs use graphite as neutron moderator Radiation changes the properties of materials The graphite core is a structural item Long term variations need tracking – Density – CTE – Strength New Requirement – Young’s Modulus

Electronic Speckle Pattern Interferometry ESPI camera measures distortions during 3 point bend test Displacements provide strain and load is used to determine strain Ratio provides the static Young’s modulus as function of stress during the test

Electronic Speckle Pattern Interferometry ESPI data can be used to examine graphite as it is tested to failure Long crack to the right of centreline is the path to failure This crack was seen to grow from pits in the centre of the sample downwards as the load increases

Interim Storage: Industry Guidance Includes section on monitoring and inspection – Identification of package safety functions – Identification of evolutionary processes that may affect safety functions – Determination of measurable indicators of these evolutionary processes – Calibration of the indicators into package performance zones

Industry Guidance: Safety Functions Containment of hazardous (notably radioactive) inventory, with minimal and predictable release of content during normal operating conditions. Containment under accident conditions arising from: impact events with minimal and predictable release of hazardous content during impact of relevant magnitude; fire with minimal and predictable release of hazardous content during fire of relevant magnitude. Identification by unique markings and these must relate to package records. Handling, including retrievability, by use of designed lifting features. Stacking once emplaced can withstand stacking stresses and remain in position. No over-pressurisation through dispersion of any gases through filters/vents. Shielding to provide radiation shielding for the store safety case and/or transport. Criticality safety by preservation of a safe distribution of fissile material within a package and with neighbouring packages.

Safety Functions, Evolutionary Processes and Potential Indicators 1/2

Safety Functions, Evolutionary Processes and Potential Indicators 2/2

What needs to be measured? Safety Functions Containment Identification Handling Stacking No over-pressurisation Shielding Criticality safety Package expansion Package corrosion Lifting feature weld degradation Package expansion Majority of HAW waste stores require remote deployment of imaging techniques in a radiation field Marking deterioration

Acknowledgements National Physical Laboratory Sellafield Ltd University of Glasgow University of Manchester