DILATOMETRIC STUDY OF U 1-x Am x O 2±δ TRANSMUTATION FUELS

Transcription

1 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 Bagnols-sur-Cèze, France 2 ENSCI/GEMH 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 /9/2012

2 CONTEXT MINOR ACTINIDES: PRODUCTION IN SPENT FUELS Minor Actinides (MA) in spent fuels: Low amounts but high radiotoxicity wt.% 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

3 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

4 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) T. Delahaye, 13 MARS F. Lebreton 2013 et al., J. Nucl. Mater. 432 (2012) T. Delahaye, F. Lebreton et al, French patent N (2011). F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 4

5 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

6 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) F. Lebreton, R.C. Belin et al., Inorg. Chem. 51 (2012) 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

7 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

8 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 K (id. for UO 2 and UO 2 /CeO 2 ) 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

9 TENTATIVE INTERPRETATION OF UO 2 /AmO 2 REACTIVE SINTERING Reactive sintering stages 1. UO 2 grains sinter on themselves Sintering onset Densification slows down due to the second phase (AmO 2 /Am 2 O 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

10 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 K Behavior closer to that of UO 2 than to a reactive sintering * T. Delahaye, 13 MARS F Lebreton et al., French patent N (2011). T. Delahaye, F. Lebreton et al., J. Nucl. Mater. 432 (2012) F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 10

11 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

12 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 ) * S. Grandjean, 13 MARS B Arab-Chapelet, J. Nucl. Mater. 385 (2009) E. Remy, S. Picart, J. Eur. Ceram. Soc. 32 (2012) F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 12

13 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) T. Delahaye, F. Lebreton et al., J. Nucl. Mater. 432 (2012) T. Delahaye, F. Lebreton et al., French patent N (2011). F. Lebreton, R.C. Belin et al., J. Solid State Chem. 196 (2012) F. Lebreton, R.C. Belin et al., Inorg. Chem. 51 (2012) D. Horlait, A. Feledziak et al., submitted to J. Nucl. Mater. D. Prieur, P. Martin et al., Inorg. Chem. 50 (2011) D. Prieur, P. Martin et al., J. Nucl. Mater. 434 (2013) F. Lebreton et al. FR 13 March 4-7, 2013 PAGE 13

14 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 Bagnols-sur-Cèze, France 2 ENSCI/GEMH Limoges, France FR 13 Fast Reactors and Related Fuel Cycles Safe Technologies and Sustainable Scenarios PAGE 14 F. Lebreton, D. Horlait, T. Delahaye Atalante /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