DILATOMETRIC STUDY OF U 1-x Am x O 2±δ TRANSMUTATION FUELS Florent Lebreton 1,2, Denis Horlait 1, Thibaud Delahaye 1, P. Blanchart 2 1 CEA, DEN, DTEC/SDTC/LEMA - 30217 Bagnols-sur-Cèze, France 2 ENSCI/GEMH - 87065 Limoges, France FR 13 Fast Reactors and Related Fuel Cycles Safe Technologies and Sustainable Scenarios Paris, France March 4-7, 2013 DEN Direction de l Énergie Nucléaire DTEC Département des TEchnologies du Cycle SDTC Service de Développement des Technologies du Cycles LEMA Laboratoires d Études des Matériaux F. Lebreton, à base D. d Actinides Horlait, T. Delahaye PAGE 1 Atalante 2012 3/9/2012
CONTEXT MINOR ACTINIDES: PRODUCTION IN SPENT FUELS Minor Actinides (MA) in spent fuels: Low amounts but high radiotoxicity 0.07-0.08wt.% of spent fuels After 100 years, 2 nd highest contributors with around 10% Several possibilities of treatment Direct disposal in geological repositories Near surface storage Partitioning and Transmutation Quantity 95% 4.9% 1%<1 U FP Pu MA Radiotoxicity 90% 10% Pu MA Others Partitioning and Transmutation option in order to: Decrease radiotoxicity and heat load of nuclear waste Lower ecological footprint of geological disposal Sodium Fast Reactors (GEN-IV) advantages: Recycling valuable actinides U (238) & Pu Transmutation of long-lived MA Am, Np (Cm?) F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 2
CONTEXT TRANSMUTATION SOLUTIONS FOR MINOR ACTINIDES MA transmutation modes: Inert-Matrix Fuels CERMET/CERCER fuels: single- or mixed-actinide (Pu, Am, NpE) oxide diluted in an inert matrix (MgO, MgAl 2 O 4, Mo) Homogeneous: MA-MOX fuels Driver MOX fuels including several % of MA in all the core of the reactor Sub-stoichiometric U 1-x-y Pu x (Np,Am,Cm) y O 2-δ with 15% < x < 30% and y < 5% Heterogeneous: MABB (Minor Actinide Bearing Blanket) Fuels composed of depleted U and MA dioxide destined for the periphery of the core U 1-x MA x O 2±δ with 10% < x < 20% MA considered separately: Priority to americium (241 and 243): Relative abundance High radiotoxicity Fabrication of U 1-x Am x O 2±δ MABB fuels From single oxide precursors Conventional powder metallurgy: pelletizing and sintering Homogeneous and dense microstructure, single-phased fluorite structure F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 3
CONTEXT PROCESSES FOR MABB FUEL FABRICATION Process based on the use of single-oxide powders (UO 2, AmO 2 ) Reactive sintering* Few steps Limited density and homogeneity UMACS, High density and homogeneity More steps (long grinding) Purpose of the dilatometric experiments Identification of key-steps and associated temperatures for both processes Comparison between the two processes Understand the differences observed in the final pellets * D. Prieur, A. Jankowiak et al., J. Nucl. Mater. 414 (2011) 503-507. T. Delahaye, 13 MARS F. Lebreton 2013 et al., J. Nucl. Mater. 432 (2012) 305-312. T. Delahaye, F. Lebreton et al, French patent N 11-60597 (2011). F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 4
EXPERIMENTAL CONDITIONS DILATOMETRIC MEASUREMENTS Apparatus Netzsch DIL402C in shielded glovebox HT graphite furnace 2200 K STC mode: Sample Temperature Controller Graphite sample holder tungsten parts to avoid oxide/graphite interactions Parameters Cylindrical pellets (Ø i,h i 5 mm) Dynamic mode: Constant heating rates of 3 K.min -1 up to T max Short plateau (10 min) Cooling down to RT Reducing atmosphere: Ar/H 2 (4%) F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 5
EXPERIMENTAL CONDITIONS SINGLE OXIDE POWDER BATCHES Depleted UO2+δ powder 241AmO 2-δ Low amount of impurities (Th) High level of impurities (Ce, Nd, Na, Fe, Np) Morphology Morphology Spherical agglomerates (10-50 µm) of submicronic particles Similar to that of UO2+δ but with larger agglomerates Thermal behavior (reducing cond.) Thermal behavior (reducing cond.) Reduction to stoichiometric state UO2.00 at low temperature Low hypo-stoichiometry at high temperature (> 1500 K) 13 MARS 2013 * F. Lebreton, R.C. Belin et al., J. Solid State Chem. 196 (2012) 217-224. F. Lebreton, R.C. Belin et al., Inorg. Chem. 51 (2012) 9369-9375. powder Reduction to cubic C-type Am2O3+δ (600 K) then hexagonal to A-type Am2O3 (1200 K)*, Sublimation risk at high temperature F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 6
This image cannot currently be displayed. DILATOMETRIC RESULTS UO 2 /AmO 2 REACTIVE SINTERING Dilatometric curve in dynamic mode: Densification rate decreases: - From 1200 to 1400 K - From 1650 to 1850 K Limited final density 85%TD Densification slows down Main cause of the low final density? Optimal temperature for sintering not reached Comparison to similar U-Ln-O systems F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 7
DILATOMETRIC RESULTS UO 2 /AmO 2 VS. UO 2 /CeO 2 REACTIVE SINTERING* Comparison of the dilatometric curves: Similar behaviors at sintering onset Only reactive sintering exhibit densification rate decrease 3 rd densification stage begins around 1850 K 3 densification stages evidenced for reactive sintering 1. 1000-1200 K (id. for UO 2 and UO 2 /CeO 2 ) 2. 1350-1650 K (delay for UO 2 /CeO 2 ) 3. > 1850 K (not reached for UO 2 /CeO 2 ) * D. Horlait, A. Feledziak et al., submitted to J. Nucl. Mater. Same behavior as other similar systems (U-Gd-O) F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 8
TENTATIVE INTERPRETATION OF UO 2 /AmO 2 REACTIVE SINTERING Reactive sintering stages 1. UO 2 grains sinter on themselves Sintering onset 1 2 2. Densification slows down due to the second phase (AmO 2 /Am 2 O 3 ) 3 4 5 3. Solid solution begins to form New driving force of the sintering Densification accelerates 4. Well-advanced solid solution Sintering slows down Irreversible defects are stabilized 5. Sintering of a nearly-monophasic sample Density limitations inherent to reactive sintering F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 9
CONVENTIONAL SINTERING RESULTS U 0.85 Am 0.15 O 2 (UMACS*, ) Solid-solution densification monitored by dilatometry: Sintering onset around 1300 K End of sintering reached Final density: 95%TD Elevated sintering onset temperature Progressive increase of densification rate Optimal temperature for sintering around 2000-2100 K Behavior closer to that of UO 2 than to a reactive sintering * T. Delahaye, 13 MARS F. 2013 Lebreton et al., French patent N 11-60597 (2011). T. Delahaye, F. Lebreton et al., J. Nucl. Mater. 432 (2012) 305-312 F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 10
DENSIFICATION REACTIVE VS. CONVENTIONNAL (UMACS) Comparison between conventional and reactive sintering: Delay of sintering onset 95%TD 85%TD 85%TD 95%TD Conventional vs. reactive sintering More elevated onset temperature No decreases of the densification rate More adapted precursor F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 11
CONCLUSIONS Dilatometric study results Reactive sintering: competition between solidsolution formation and densification process the latter is slowed down and final density limited Conventional sintering: avoids this competition higher densities are reached New homogeneous U 1-x Am x O 2±δ precursors Powders synthesized by oxalate co-conversion* Reactive sintering UMACS Microspheres formed using the CRMP (WAR-like) process Perspectives Use of other surrogate: Nd, Pr (Gd) Synthesis of compounds with high Am/(U+Am) ratios Acquisition of data in the U-Am-O system Self-irradiation study (see poster IAEA-CN-199-192) * S. Grandjean, 13 MARS B. 2013 Arab-Chapelet, J. Nucl. Mater. 385 (2009) 204-207. E. Remy, S. Picart, J. Eur. Ceram. Soc. 32 (2012) 204-207. F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 12
THANK YOU FOR YOUR ATTENTION! Acknowledgements LEMA: Philippe Coste, Marc Bataille, Serge Caron, Caroline Léorier ICSM/LIME: Nicolas Clavier, Nicolas Dacheux PACFA Program for Florent Lebreton Ph.D and Denis Horlait post-doc fundings References D. Prieur, A. Jankowiak et al., J. Nucl. Mater. 414 (2011) 503-507. T. Delahaye, F. Lebreton et al., J. Nucl. Mater. 432 (2012) 305-312. T. Delahaye, F. Lebreton et al., French patent N 11-60597 (2011). F. Lebreton, R.C. Belin et al., J. Solid State Chem. 196 (2012) 217-224. F. Lebreton, R.C. Belin et al., Inorg. Chem. 51 (2012) 9369-9375. D. Horlait, A. Feledziak et al., submitted to J. Nucl. Mater. D. Prieur, P. Martin et al., Inorg. Chem. 50 (2011) 12437-12445. D. Prieur, P. Martin et al., J. Nucl. Mater. 434 (2013) 7-16. F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 13
DILATOMETRIC STUDY OF U 1-x Am x O 2±δ TRANSMUTATION FUELS Florent Lebreton 1,2, Denis Horlait 1, Thibaud Delahaye 1, P. Blanchart 2 1 CEA, DEN, DTEC/SDTC/LEMA - 30217 Bagnols-sur-Cèze, France 2 ENSCI/GEMH - 87065 Limoges, France FR 13 Fast Reactors and Related Fuel Cycles Safe Technologies and Sustainable Scenarios PAGE 14 F. Lebreton, D. Horlait, T. Delahaye Atalante 2012 3/9/2012 Paris, France March 4-7, 2013 DEN Direction de l Énergie Nucléaire DTEC Département des TEchnologies du Cycle SDTC Service de Développement des Technologies du Cycles LEMA Laboratoires d Études des Matériaux à base d Actinides