Development of Cerium-Neodymium Oxide surrogates for Americium Oxides

Transcription

1 Development of Cerium-Neodymium Oxide surrogates for Americium Oxides Emily Jane Watkinson 1a. M. J. Sarsfield 2, R. M. Ambrosi 1a, H. R. Williams 1b, D. Weston 1b, N. Marsh 1c, C. Haidon 1c, K. Stephenson 3, T. Tinsley 2 1a. Department of Physics and Astronomy, UoL; 1b. Department of Engineering, UoL 1c. Department of Geology, UoL; 2. National Nuclear Laboratory 3. European Space Agency ESTEC PhD studentship funded by STFC

2 Contents Introduction PART I: Crystal Theory Am Oxides, AmO 2-x/2 and Ce 1-x Nd x O 2-x/2 Surrogate PART II: Surrogate Synthesis Objectives Results to date

3 Introduction: why consider surrogate for AmO 2-(x/2) using Ce and Nd? Surrogate with a stable x value. Potential to study reduction behaviour of surrogate during future studies. Theory dictates 1 that the Nd to Ce ratio can be used to infer the Oxygen to Metal ratio. Once fully investigated: CeNd Oxide solid solution production is potentially simpler than CeO 2-(x/2). Diversity in surrogates: more data to inform AmO 2-(x/2) possible behaviour.

4 PART I: CRYSTAL THEORY 2.

5 Am Oxides and AmO 2 x 2 Relevant Oxide Forms Oxide AmO 2 A-Am 2 O 3 B-Am 2 O 3 C-Am 2 O 3 Symmetry FCC Hexagonal Monoclinic Cubic AmO 2-x/2 Solid Solution: AmO 2 x 2 3. Am 2 O 3 Cubic AmO

6 Ce 1 x Nd x O 2 x 2 Surrogate Surrogates for End Phases Am Oxide Surrogate Symmetry Oxide AmO 2 CeO 2 FCC A-Am 2 O 3 A-Nd 2 O 3 Hexagonal C-Am 2 O 3 C-Nd 2 O 3 Cubic e.g. CeO 2 (F-type) 1. Ce 1 x Nd x O 2 x 2 Solid Solution (SS) C-type Ce 1-x Nd x O 2-x/2 1. Structure x value F-type SS 0 < x 0.39 C-type SS 0.39 < x 0.73 C type SS and A type Nd 2 O x < 1 1. A-type Nd 2 O 3 1.

7 PART II: SURROGATE SYNTHESIS Oxalate Precipitation Thermal Decomposition

8 The Objectives 1. Can the proposed route create a solid solution? 2. Can Ce 1-x Nd x O 2-(x/2) with 0.5 <x < 0.7 be made with repeatability? 3. How does reaction temperature and stirring rate affect oxalate particle morphology and size? 4. How do the thermal decomposition variables affect oxide properties?

9 Results: Oxalate Material

10 1. Is it an Oxalate solid solution? XRD and Raman Spectroscopy: Rare Earth oxalate No further information

11 1. Is the Oxide a Solid Solution?

12 1. Is the Oxide a Solid Solution? Thermogravimetric Analysis Hypothesis: 100.0% 90.0% 80.0% De Almeida et al. (2008) 70.0% considered a heating rate of 2 C 60.0% min -1 for Ce (--) and 50.0% Nd ( ) oxalate decompositions 40.0%. Mass fraction Temperature ( C) 4. Example of thermal decomposition of an early oxalate sample.

13 1. Is the Oxide a Solid Solution? Powder X-ray Diffraction

14 1. Is the Oxide a Solid Solution? Powder X-ray Diffraction

15 2. Can Ce 1-x Nd x O 2-(x/2) with 0.5 < x< 0.7 be made with repeatability? Measure X-ray Fluorescence of the oxalate. Calculate Nd : (Ce+Nd) and compare. Semi-quantitative analysis 3 segments of each sample. Oxalate Sample # x values ; 0.59; ; 0.62; ; 0.51; 0.53

16 2. Can Ce 1-x Nd x O 2-(x/2) with 0.5 < x< 0.7 be made with repeatability? Future: collect more data to determine variability in x for a given sample.

17 3. Oxalate Morphology and Size Variation Current experiments: effect of stirring rate at 25 C. Future: investigate 60 C reactions. SEM: shape and size estimate Laser Diffraction for relative size distribution

18 Results: Oxalate Morphology Example: 25 C, 250 RPM Example: 25 C, 400 RPM

19 References 1. Horlait, D., et al., Stability and structural evolution of Ce(IV)(1- x)ln(iii)(x)o(2-x/2) solid solutions: a coupled micro-raman/xrd approach. Inorg Chem, (15): p Runde and Wallace, Amercium, in The Chemistry of the Actinide and Transactinide Elements, L.R. Morss, Editor. 2008, Springer: The Netherlands. p Thiriet, C. and R.J.M. Konings, Chemical thermodynamic representation of AmO2 x. Journal of Nuclear Materials, (3): p De Almeida., et al. Insights into the Thermal Decomposition of Lanthanide(III) and Actinide(III) Oxalates - from Neodymium and Cerium to Plutonium. European Journal of Inorganic Chemistry, 2012, p

20 Thank you for your interest, I would be happy to take any questions.