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Mineral Physics Group University of Cambridge

Mineral Physics Group University of Cambridge. Identifying and Quantifying Actinide Radiation Damage in Ceramics with Nuclear Magnetic Resonance. Ian Farnan , Department of Earth Sciences, University of Cambridge, UK. Mineral Physics Group University of Cambridge.

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Mineral Physics Group University of Cambridge

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  1. Mineral Physics Group University of Cambridge Identifying and Quantifying Actinide Radiation Damage in Ceramics with Nuclear Magnetic Resonance Ian Farnan, Department of Earth Sciences, University of Cambridge, UK

  2. Mineral Physics Group University of Cambridge Methods to determine degree of radiation damage as a function of dose. Macroscopic measurements: Density, birefringence Diffraction: Electron microscopy, x-ray diffraction Simulation: SRIM/TRIM , Molecular dynamics

  3. Mineral Physics Group University of Cambridge

  4. Mineral Physics Group University of Cambridge • Radiation resistance measured via ion beams • Critical amorphisation temperatures • Initial damage + recovery (temperature dependent)

  5. Mineral Physics Group University of Cambridge • Radiation resistance measured via ion beams • Critical amorphisation temperatures • Initial damage + recovery (temperature dependent) • Possible influence of surface in recovery mechanism

  6. Mineral Physics Group University of Cambridge • Radiation resistance measured via ion beams • Critical amorphisation temperatures • Initial damage + recovery (temperature dependent) • Possible influence of surface in recovery mechanism • Total energy not deposited in sample, channelling

  7. Mineral Physics Group University of Cambridge Zircon - Structure I41/amd ao = 6.1000 Å co = 6.0100 ÅIsolated (Q0) SiO4 tetrahedra linked by ZrO8 dodecahedra

  8. Mineral Physics Group University of Cambridge a-damage Common assumptions Flight of a-particle causes ionisations, stopping leads to 100-200 atomic displacements.Recoil of heavy nucleus causes 1000-2000 atomic displacements

  9. Mineral Physics Group University of Cambridge TRIM/SRIM Calculations on Zircon Zr = 79 eV Si = 23 eV O = 47 eV Displacement energies: Density 4.7 g cm-3 Particle 234U, 86 keV

  10. Mineral Physics Group University of Cambridge TRIM/SRIM Calculations on Zircon Zr = 79 eV Si = 23 eV O = 47 eV Displacement energies: Density 4.7 g cm-3 Particle 234U, 86 keV 792 atoms displaced in a highly branched ‘cascade’

  11. Mineral Physics Group University of Cambridge TRIM/SRIM Calculations on Zircon 792 atoms displaced in a highly branched ‘cascade’

  12. Mineral Physics Group University of Cambridge 300,000 atoms, 30 keV MD simulation of damage caused by heavy nucleus recoil (Kostya Trachenko, Martin Dove)

  13. Mineral Physics Group University of Cambridge Previous work on quantifying radiation damage in zircon based on volume/density considerations. Non-linear growth of amorphous -fraction - multiple overlap models

  14. Mineral Physics Group University of Cambridge 29Si MASNMR (π/12 pulse every 300 s) Spin-counting NMR records signals from atoms with magnetic nuclei. Does not depend on long range order and gives damaged fraction in number of atoms not amorphous volume fraction as from volume/density measurements.

  15. Mineral Physics Group University of Cambridge First 29Si MASNMR data on radiation damaged natural zircon

  16. Mineral Physics Group University of Cambridge First 29Si MASNMR data on radiation damaged natural zircon

  17. Mineral Physics Group University of Cambridge First 29Si MASNMR data on radiation damaged natural zircon

  18. Mineral Physics Group University of Cambridge Series of 29Si MASNMR spectra of radiation damaged zircons.

  19. Mineral Physics Group University of Cambridge Series of 29Si MASNMR spectra of radiation damaged zircons. • Signal quantified by comparing signal per atom to that from known mass of K2Si4O9 glass

  20. Mineral Physics Group University of Cambridge Series of 29Si MASNMR spectra of radiation damaged zircons. • Signal quantified by comparing signal per atom to that from known mass of K2Si4O9 glass • Progressive increase in number of atoms in amorphous component with dose.

  21. Mineral Physics Group University of Cambridge Series of 29Si MASNMR spectra of radiation damaged zircons. • Signal quantified by comparing signal per atom to that from known mass of K2Si4O9 glass • Progressive increase in number of atoms in amorphous component with dose. • Residual crystalline peaks visible even at 9.6 x1018a/g.

  22. Mineral Physics Group University of Cambridge Series of 29Si MASNMR spectra of radiation damaged zircons. Magnetic resonance data Density/volume data

  23. Mineral Physics Group University of Cambridge • Damage accumulates but volume of amorphous phase is constrained to be same as zircon crystal • Damaged areas join up, macroscopic swelling begins - percolation transition. • Second percolation point; crystal islands in amorphous matrix no increase in macroscopic volume. • Complete amorphisation a-Dose

  24. Mineral Physics Group University of Cambridge Local structural changes from periodic chemical shift calculations (Francesco Mauri + Etienne Balan (LMCP, Paris), Chris Pickard (Cavendish, Cambridge) Macroscopic volume no longer changes Centre of gravity of amorphous phase becomes more negative with dose up to ~second percolation point. Increasing connectivity in amorphous phase (empirical shift-structure relationships) Crystal structure changes until ~first percolation point

  25. Mineral Physics Group University of Cambridge Shocked zircon sample (52 GPa, Fiske et al.) experiments - 91.1 ppm Reidite (scheelite structure) 12 GPa (23 GPa at RT) Theory : 11 GPa - 81.6 ppm Zircon

  26. Reidite damaged zircon Zircon (reference) Mineral Physics Group University of Cambridge Theoretical 29Si NMR shifts in zircon and reiditeunder pressure • Not simply related to swelling • Not pressure induced • Role of point defects ?

  27. Mineral Physics Group University of Cambridge Causes of changes in crystalline phase Long-range techniques (x-ray) see lattice expansion. Short-range techniques (NMR) see pressure effect. Defects pushing into structure? Oxygen?

  28. Mineral Physics Group University of Cambridge Simulation of secondary events Damaged region receives a second hit ‘glancing’

  29. Mineral Physics Group University of Cambridge Absolute quantification of radiation damage

  30. Mineral Physics Group University of Cambridge Objective: work on real wasteforms Quantify number atoms displaced per alpha decay in Pu-doped samples Observe differences in local structure of amorphous phase (high coordinated silicon?) Investigate dose rate effects by comparison with natural samples

  31. Mineral Physics Group University of Cambridge

  32. Mineral Physics Group University of Cambridge Containment CMX 7.5 mm Pencil rotor + inserts PTFE secondary containment Sample core AlN primary containment Pencil rotor

  33. Mineral Physics Group University of Cambridge 29Si MASNMR (3.5 kHz) Pu containing zircons Tecmag Discovery 300 t1/2 = 87.7 years 4.2 x 1019a/g 10 wt% 238Pu t1/2 = 24,100 years 8.2 x 1016a/g 5 wt% 239Pu CPMG echo trains, 64 echoes, 1000s delay, 24 scans 51.6 mg and 75.1 mg samples, 6 hours 40 mins acquisition

  34. Mineral Physics Group University of Cambridge Natural zircon 1.2 x 1018a/g 10 wt% 239Pu doped zircon 1.0 x 1017a/g

  35. Mineral Physics Group University of Cambridge Comparison 29Si MASNMR 239Pu zircon vs 238U/232Th damaged natural zircons 239Pu Zircon

  36. Mineral Physics Group University of Cambridge Comparison 29Si MASNMR 238Pu zircon vs fully metamict natural zircon Natural zircon (238U) 570 million years old 9.6 x 1018a/g 238Pu zircon 23 years old 4.2 x1019a/g

  37. Mineral Physics Group University of Cambridge Comparison 29Si MASNMR 238Pu zircon vs fully metamict natural zircon Natural zircon (238U) 570 million years old 9.6 x 1018a/g 238Pu zircon 23 years old 4.2 x1019a/g

  38. Mineral Physics Group University of Cambridge • Summary • NMR can spin-count displaced atoms resulting from radioactive decay events. Providing essential starting data for models of damage accumulation. • Amorphisation by ‘internal’ radioactive decay (with density of damaged areas constrained) may differ significantly from exterior bombardment by heavy ions. • Densification accompanies a-decay events • Active MASNMR now possible • Damage measurement in crystals • Structural characterisation amorphous regions in radiation damaged materials and glasses

  39. Mineral Physics Group University of Cambridge Collaborations • Cambridge • Sharon Ashbrook • Greg Lumpkin • Karl Whittle • Nigel Johnson • PNNL • Herman Cho • Bill Weber • Randy Scheele • Anne Kozelisky • Paratec/Castep • Francesco Mauri (Paris VI) • Chris Pickard (Cavendish) • Etienne Balan(Paris VI)

  40. Mineral Physics Group University of Cambridge Active experiments Hanford 300 Area Radiochemical Processing Laboratory

  41. Mineral Physics Group University of Cambridge Containment CMX 7.5 mm Pencil rotor + inserts PTFE secondary containment Sample core AlN primary containment Pencil rotor

  42. Mineral Physics Group University of Cambridge Protocol • cut core • remove from the glovebox • load into containment in RA fumehood • test spin in CA area (3.5 kHz) • release probe and rotor to RMA • Perform MAS experiment - activate alarm

  43. Mineral Physics Group University of Cambridge 29Si MASNMR (3.5 kHz) Pu containing zircons Tecmag Discovery 300 10 wt% 238Pu t1/2 = 87.7 years 3.7 x 1019a/g 5 wt% 239Pu t1/2 = 24,100 years ~ 1 x 1017a/g CPMG echo trains, 64 echoes, 1000s delay, 24 scans

  44. Mineral Physics Group University of Cambridge Comparison 29Si MASNMR 238Pu zircon vs fully metamict natural zircon Natural zircon (238U) 570 million years old 9.6 x 1018a/g 238Pu zircon 20 years old 3.7 x1019a/g

  45. Existing methods • Radiation resistance measured via ion beams • Critical amorphisation temperatures • Initial damage + recovery (temperature dependent)

  46. Damage Curves for La2Zr2O7 and La2Hf2O7. Karl Whittle + Greg Lumpkin

  47. La/Y disorder in La2–xYxZr2O7 x 0.4 pyrochlore 0.8 1.2 Defect fluorite 1.6 2.0 442 0 -221 221 ppm

  48. Mineral Physics Group University of Cambridge Summary • NMR can spin-count displaced atoms resulting from radioactive decay events. Providing essential starting data for models of damage accumulation. • Amorphisation by ‘internal’ radioactive decay (with density of damaged areas constrained) may differ significantly from exterior bombardment by heavy ions. • Densification accompanies a-decay events • Active MASNMR now possible: • Damage measurement in crystals/ceramics • Characterisation of amorphised regions • Radwaste glasses

  49. Epitaxial recrystallisation ZrSiO4 1 keV, 600˚C Thermally enhanced recrystallisation

  50. Properties that contribute to radiation tolerance • Cascade size - ballistic rather than chemical effect • Competition between short range and long range forces in cascade • Short range promotes polymerised structures eg Si-O-Si in zircon -leads to amorphisation CaTiO3 30 keV cascade

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