Microparticle Reference Materials for Particle Analysis in Nuclear Safeguards Production & Characterisation

Transcription

1 Microparticle Reference Materials for Particle Analysis in Nuclear Safeguards Production & Characterisation 01 May 2018 I Stefan Neumeier, Philip Kegler, Martina Klinkenberg, Irmgard Niemeyer, Dirk Bosbach

2 Introduction Safeguards R&D framework at Institute of Energy and Climate Research - IEK-6: Nuclear Waste Management and Reactor Safety *NUSAFE: Programme Nuclear Waste Management, Safety and Radiation Research within the Research Field Energy of the Helmholtz Association

3 Introduction Nuclear safeguards particle analysis Treaty on non-proliferation of nuclear weapons signed by 191 countries Member-states declare not to develop nuclear weapons But, independent verification IAEA Inspectors visit nuclear facilities Bulk samples to verify declaration Swipe samples to detect undeclared activities Photo: Petr Pavlicek (IAEA) Swipe samples sent to dedicated network of analytical laboratories ( NWAL ) Analysis of isotopics of single microparticles (e.g. LG-SIMS) Analytical measurements require quality control measures to ensure correct results Need of microparticle reference materials Photo: D. Calma (IAEA)

4 Introduction Nuclear safeguards particle analysis Since 07/2012 joint effort between Forschungszentrum Jülich (IEK-6) and IAEA-SGAS 1 Goal: Establishment of a production process for particles suitable as reference material for quality control, method validation, instrument calibration & proficiency testing and delivery of particles Additional Goal: Make production capacity available at FZ Jülich Final characterisation and certification by other laboratories (IAEA-SGAS 1, JRC-Geel 2 ) 1 SafeGuards Analytical Services; Vienna-Seibersdorf, Austria 2 Joint Research Center Geel, Belgium (Former Institute for Reference Materials & Methods (IRMM))

5 Particle Reference Standard Production Process at Forschungszentrum Jülich Two step process: Particle production 1. Aerosol-based particle production and collection 2. Particle distribution on substrates using suspensions Collection on substrate material Transfer in suspension Transfer onto substrate Production Processing Characterisation Distribution

6 Particle Production Current set-up: Vibrating Orifice Aerosol Generator (VOAG)

7 Particle Production Current set-up: Vibrating Orifice Aerosol Generator (VOAG) Process control Temperature of aerosol heater Air flow Liquid flow Determination of el. content per particle Online monitoring with optical particle counter

8 Particle Characterisation Overview

9 Particle Characterisation Precursor chemistry & heat treatment UN; T = 500 C UC; T = 500 C UA; T = 400 C UN: Uranyl nitrate UA: Uranyl acetate UC: Uranyl chloride S. Neumeier et al MRS Adv. (2018) R. Middendorp et al. Anal. Chem. 89 (2017)

10 Particle Characterisation Morphology & porosity (FIB/SEM) Uranyl nitrate; T = 500 C Uranyl chloride; T = 500 C Uranyl acetate; T = 400 C UN: Uranyl nitrate UA: Uranyl acetate UC: Uranyl chloride S. Neumeier et al MRS Adv. (2018) R. Middendorp et al. Anal. Chem. 89 (2017)

11 Particle Characterisation Particle size distribution (SEM) 5 µm Spherical particles with monodisperse particle size distribution

12 Particle Characterisation Crystal structure (µ-xrd, µ-xanes, µ-raman) μ-xrd μ-xanes μ-raman microxas beamline (PSI) 4x1.5 µm beam (17.2 kev) microxas beamline (PSI) 300x300 µm beam (U L 3 edge) μ-raman spectroscopy (CEA) 0.6 µm laser (514 nm) Orthorhombic U 3 O 8 phase U V /U VI mixture (U 3 O 8 ) Orthorhombic U 3 O 8 phase UN: Uranyl nitrate UA: Uranyl acetate UC: Uranyl chloride R. Middendorp et al. Anal. Chem. 89 (2017)

13 Particle Production Process Present system: Pros & cons Particles are collected using vacuum impactors + Can be used without further handling Inhomogeneous deposition Requires solid substrate No mixing of particles possible Limited to ca. 50 samples/day Problems can be overcome with intermediate processing step Collection using inertial impactor Particle transfer into suspension ultrasonification Optional: Mixing of suspensions Distribution on substrates controlled drying Stability of particles in suspension has to be investigated

14 Particle Suspension Suspension medium testing Various solvents were tested as medium: Water dissolution Dimethyl formamide particle break-up n-decane and n-hexane no detachment 2-Propanol agglomeration Ethanol very good detachment & no degradation Ethanol most suitable suspending medium

15 Particle Suspension Chemical durability Dissolution in ethanol for 455 days No significant dissolution measured after 228 days storage (ICP-MS) No significant dissolution observable after 455 days storage (SEM) S. Neumeier et al MRS Adv. (2018)

16 Particle Suspension Particle suspension Prepared suspensions are dried on substrates Temperature critical to control deposition ( evaporation rate) Drying on heating plate (50 C): Direct deposition: 5 µm Homogeneous particle deposition achieved

17 Particle Suspension Application Distribution of particle mixtures Suspensions can also be mixed to produce particle mixtures Uranium and cerium particle suspensions mixed Substrates measured by SEM/EDX Production of particle mixtures feasible

18 Particle Suspension Application Distribution onto different substrates Mixed U/Ce suspensions mixture dried on piece of cotton swipe Production of defined swipe samples feasible for interlaboratory comparison exercises

19 Particle Production Process Summary Aerosol-based particle production method provides microparticles: with orthorhombic U 3 O 8 structure with average diameter of ~ 1µm and narrow size distribution with high density and some inner porosity with high chemical stability in ethanol No significant measurable [228 days] and visual particle dissolution [455 days] Particle suspensions in ethanol: Homogeneous particle distribution on substrates Particle mixtures prepared Particles deposited onto cotton swipes Number of samples/day:

20 Particle Production Process Conclusion A reliable two step process is developed and established at FZJ Particle production using aerosol technique Particle distribution using particle suspensions in ethanol 1 µm The coupled process offers high flexibility according to the user s requirements high reproducibility regarding homogeneity and stability suitability to produce particle reference standards for particle analysis First batch of samples is successfully certified as reference material for interlaboratory comparison exercise (NUSIMEP-9; 2018)

21 Particle Production Outlook Optimisation of the existing method Preparation of particles with mixed composition with respect to the IAEA s requirements and the need of NWAL partners U, U/Th, U/Pu, U/Ln, particles Focus on materials science aspects of microparticles, e.g. detailed structural investigations using FZJ s infrastructure & synchrotron facilities Development of new methods for particles reference material production, e.g. wet chemical methods Becoming member of IAEA S Network of Analytical Laboratories for the provision of Microparticle Reference Materials for Particle Analysis in Nuclear Safeguards

22 ACKNOWLEDGEMENTS German Support Programme to the IAEA (Task C. 43 / A1960; C.45 / A1961) Bundesministerium für Wirtschaft und Energie "Neu- und Weiterentwicklung von Safeguardstechniken und -methoden" (FKZ 02W6263) R. Middendorp, A. Knott, M. Dürr IAEA-SGAS & JRC-Geel Dr. Stefan Neumeier International Safeguards Forschungszentrum Jülich GmbH Institute for Energy- and Climate Research IEK-6: Nuclear Waste Management and Reactor Safety D Jülich Germany s.neumeier@fz-juelich.de