Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Mechanism of RuO 2 crystallization in HLW simplified borosilicate containment glass 1 H. Boucetta, 1 S. Schuller, 2 L. Stievano, 3 R Podor and 3 J.Ravaux, 4 S. Gossé, 5 X. Carrier and 5 S. Casale, 1 A. Monteiro 1 CEA/DEN/DTCD/SECM/LDMC F Bagnols sur Cèze, France 2 ICG-AIME UMR CNRS 5253, Université Montpellier II F Montpellier, France 3 ICSM UMR 5257, CEA-CNRS-UMS-ENSCM F Bagnols sur Cèze, France 4 CEA/DEN/DPC/SCCME/LM2T F Gif sur Yvette, France 5 UPMC-Université Pierre et Marie Curie, LRS F Paris, France

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Vitrification of High Level waste (HLW) Fission products and actinide solutions arising from reprocessing of spent uranium oxide (UOx) fuel are confined in glass matrix Needles polyhedra RuO 2 Homogeneous glass containing RuO 2 particles SiO 2, B 2 O 3, Na 2 O, Al 2 O 3, CaO, LiO 2, CoO, NiO, Fe 2 O 3 Glass frit Fission products : Ru Actinide, Corrosion products, Addition elements, Vitrification adjuvant. Calcined waste

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Influence on physical and chemical properties of glass Influence of RuO 2 particules in glasses  Conductivity increasing with the …..amount of RuO 2 Electrical conductivity Chemical reactivity Reference : C. Simonnet (2004), phd  Limited reactivity with platinoids  Higher conductivity in glass with ….needles RuO 2 Viscosity  Increase with amount of platinoids Needles Polyhedra Volume fraction of RuO 2 Polyhedra

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Objective of this research topic Glass frit SiO 2 - B 2 O 3 - Na 2 O DenitrationCrystallization Homogenization Morphology of RuO 2 : acicular or polyhedral ? Objective Understanding of transformation mechanisms of ruthenium dioxide in sodium borosilicate glasses In situ (ESEM, DTA/DGA) Calcined waste NaNO 3 - RuO 2 Ex situ (XRD, EXAFS, HRTEM, SEM) Solid state Liquid state Analytical Techniques RuO 2 needles References : C. Krause, B. Luckscheiter (1991) J. of Mater. Res B. Luckscheiter (1993), Low and intermediate level radioactive waste management Y Enokida et al (2009) WM Conference, AZwaste management Y Enokida et al (2012) WM Conference, waste management

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, in situ HT-ESEM study Dissolution mechanism of RuO 2 in NaNO 3 RuO 2 NaNO 3

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Dissolution mechanism of RuO 2 in NaNO 3 in situ HT-ESEM study of RuO 2 dissolution in NaNO 3 NaNO 3 RuO 2 T=25°C T=320°C Spreading of RuO 2 particles in liquid NaNO 3 Dissolution of particles T= °C T= °C RuO 2 nanoparticles Crystallization : Na x RuO y Aggregation and Growth of ruthenium particles T= °C Na 3 RuO 4  RuO 2 nanoparticles spread in a …. nitrate/nitrite mixture  Na x RuO y spread in Na, N, O phase Na 3 RuO 4

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Transformation mechanism of RuO 2 in a large amount of NaNO 3 Calcined waste NaNO 3 solid, RuO 2 NaNO 3 melting 317°C Denitration NaNO 3 -NaNO 2 Na 3 RuO 4 formation RuO 2 Na x RuO y formation 500°C Hypothetic Reaction : 3 NaNO 3 + RuO IV 2 = Na 3 Ru V O O 2 (g) + 3 NO (g) Hypothetic Reaction : x Na 3 Ru V O 4 + y NaNO 3 = Na x RuO y Hypothetic Reaction  NaNO 3 = NaNO 2 + ½ O 2 RuO 2 nanoparticles dissolved

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Verre NaRu precursor T=230°C T=25°C Eutectic melting of NaNO 3 - NaNO 2 mixture Spreading of NaRu precursor Sodium silicate/borate and Na 3 RuO 4 formation on the glass surface T > 300°C Reactivity between the NaRu precursor and the Glass in situ HT-ESEM study of reaction between NaRu precursor and the Glass Crystals dissolution - Na 3 RuO 4 decomposition T > Tg (571°C) RuO 2 needles formation Reference : H. Boucetta et al., Mechanism of RuO 2 crystallization ………………in borosilicate glass: an original in situ ESEM approach, ………………Inorganic Chemistry, march 2012 Reference : R. W. Berg et al., NaNO 2 +NaNO 3 phase ……………...diagram : New data from DSC and Raman ………………spectroscopy, J. Chem. Eng. Data, 2006, 51, ………………34-39

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Direct incorporation of RuO 2 in the Glass with or without NaNO 3  Difficulty of RuO 2,,,,,incorporation in the glass,,,,,(low reactivity)  Spreading of RuO 2 in the,,,,,glass in situ HT-ESEM observations SEM micrograph Direct incorporation of Na 3 RuO 4 in the Glass in situ HT-ESEM observations Formation of RuO 2 needles in glass Direct incorporation of Ru-compound in the Glass In situ XANES spectra at the Ru K-edge of reaction between Na 3 RuO 4 and glass Ru V Ru IV

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Conclusion Reaction hypothesis : 2 NaNO 3 = Na 2 O (melt) + 3/2 O NO Reaction hypothesis : 2 Na 3 Ru V O 4 (s) = 3 Na 2 O (melt) + 2Ru V+ (melt) + 5O II- (melt) Ru V+ (melt) + 5/2 O II- (melt) = RuO 2 (s) + ½ O 2 Enokida hypothesis : Decomposition of Na 3 RuO 4 in RuO 4 Needles of RuO 2 formation

Hassiba BOUCETTAMRS Spring Meeting - San Francisco - April, Thank you for your attention