MESURES CALORIMÉTRIQUES SUR VERRES ETUDES DES EFFETS D IRRADIATION DANS RADIOACTIFS : LES VERRES NUCLÉAIRES. Funded by CEA and AREVA NC

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1 MESURES CALORIMÉTRIQUES SUR VERRES RADIOACTIFS : ETUDES DES EFFETS D IRRADIATION DANS LES VERRES NUCLÉAIRES S, Peuget, E. A. Maugeri, C. Jégou DEN/DTCD/SECM, CEA Marcoule, France Funded by CEA and AREVA NC With the support of D. Staicu, A. Zappia, T. Wiss, EC JRC, Karlsruhe, Germany CEA 10 AVRIL 2012 PAGE 1 CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 1

2 French Nuclear Glass: SON68 or R7T7 Oxide glass with around 30 oxides Sodium alumino-borosilicate glass L. Cormier, J.M. Delaye, D. Ghaleb, G. Calas, PRB 61 (2001) Fission product / Actinide in an octahedric site Si O B Na Emission of charged particles CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 2

3 Ion M 1, Z 1 Sputtered atom Solid M 2, Z 2 Interaction with matter Due to the various decays: Emission of particles with high amount of energy hn electronic capture e - e - ionization e - of target Ionization of atoms incident ion Implanted ion V=0 Displacment cascade Se = (de/dx) elec = Electronic energy loss due to collisions with electrons Sn = (de/dx) nucl = Nuclear energy loss due to collisions with atoms S e <S e threshold S e >S e threshold S n CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 3

4 Glass Long Term Behavior: Effect of Alpha decays? Alpha decay 5 MeV 244 Cm 240 Pu 100 kev Minor actinides: - Main source of atomic displacements in the glass structure - Main source of energy deposition over the long term What is the effect of alpha self-irradiation on the glass long term behavior? Stability of the glassy state under irradiation? CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 4

5 Glassy state A glass (or vitreous solid) is a solid formed by rapid melt quenching. A glass is an amorphous solid that exhibits a glass transition phenomena at T g. Relaxation time Viscosity G Shear Modulus Glass properties depend on: - Chemical composition - Thermal history during elaboration process CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 5

6 DSC to probe the glassy state What is the glassy state of the irradiated glass? CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 6

7 Methodology: 244 Cm doping - SON68 glasses doped with 0.04, 0.4, 1.2, 3.25wt% of 244 CmO 2 - International Standard Glass (ISG) doped with 0.7wt% of 244 CmO E+20 Alpha decay dose (a/g) 1.00E E E wt% CmO 0.4wt% CmO 1.2wt% CmO 3.25wt% CmO ~ to years of storage E+16 Mol% SiO 2 Na 2 O B 2 O 3 Al 2 O 3 CaO ZrO 2 Other oxides ISG/CJ R7T time Initial characterizations of the glasses (homogeneity, chemical composition) Periodical characterizations of the glass properties (density, Hv, DSC, Raman ) CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 7

8 Effect on the glass microstructure 244 Cm SON 68 glass : SEM (CEA Marcoule), alpha decay dose 2x10 19 a/g (Around years of storage) S. Peuget et al. JNM 44 (2014) 244 Cm SON 68 glass : TEM (ITU Karlsruhe), alpha decay dose 8x10 18 a/g Homogeneous microstructure, without bubbles, phase separation or crystallization Macroscopic stability of the glassy state CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 8

9 Effect on the macroscopic properties? Density Slight decrease of the glass density (0.5%) Evolution according to an exponential law (direct impact model) Stabilization of the evolution at around 4x10 18 a/g CmSON68 0.4CmSON68 1.2CmSON CmSON68 exponential law -0.1 Density variation (%) x x x x x x x x x x10 19 Alpha decay dose (a/g) S. Peuget et al. J. Nucl. Mat. 354 (2014) 1 CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 9

10 DSC Measurements on 244 Cm doped glasses Netzsch STA EC, JRC-DG Karlsruhe Heating rate : 15K/min. 1asc scan up to 920K, cooling down to RT, 2asc scan up to 920K Verre fortement endommagé! asc Cpg 2 Asc Dose 2.38 x a-decay cm -3 Heat capacity, Cp (J K -1 g -1 ) Exo Endo Stored Energy = J g -1 Glass Transition 0.6 T fictive = 544 C Temperature, T( C) CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 10

11 DSC Measurements on 244 Cm doped glasses In the red area, 2 contributions: - Stored energy associated to the accumulation of structural defetcs induced by irradiation - Undershoot associated to the difference between cooling rate during fabrication and heating rate during DSC experiment asc Cpg 2 Asc Dose 2.38 x a-decay cm -3 Heat capacity, Cp (J K -1 g -1 ) Exo Endo Stored Energy = J g -1 Glass Transition 0.6 T fictive = 544 C Temperature, T( C) Schéma à ajouter? CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 11

12 Stored Energy versus cumulative dose E. A. Maugeri et al. JACER (2012) 0,0-0, Stored Energy Energy Release, J g -1-0,2-0,3 Stored Energy, J g ,4 Dose, 2.29 x a-decay cm -3 Dose, 1.34 x a-decay cm -3 Dose, 2.38 x a-decay cm Temperature, C Cumulative Dose, a-decays g -1 Assumption: we neglect the contribution of undershoot and assume that all the area is associated to punctual defects formed due to radiation Higher limit for Stored Energy ~ 110J/g CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 12

13 DSC Measurements on 244 Cm doped glasses asc Cpg 2 Asc Dose 2.38 x a-decay cm -3 Heat capacity, Cp (J K -1 g -1 ) Exo Endo Stored Energy = J g -1 Glass Transition 0.6 T fictive = 544 C Temperature, T( C) CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 13

14 Determination of the fictive temperature Tf E. A. Maugeri et al. JACER (2012) Method used: C. T. Moynihan et al, JACER (1976) C pl C pg Effect of high quenching rate: Undershoot associated to the difference between cooling rate during fabrication and heating rate during DSC experiment We neglect the undershoot : lower limit for Tf CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 14

15 Fictive temperature versus alpha decay dose E Maugeri et al, J. Am. Ceram. Soc. 95 (2012) 2869 Increase of the glass fictive temperature with alpha decay dose Formation a new structure similar to a fast quenched glass New metastable phase induced by irradiation CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 15

16 Characteristics of the irradiated glassy state? What happen in the displacement cascade induced by a recoil nuclei? 1. Balistic phase JM Delaye, PRB 61 (2000) Thermal phase Local Temperature (K) Quenching Rate (K.s -1 ) Golden = Si Green = B Blue = Na Red = O Time (ps) CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT Very high quenching rate of the disordered state induced by the displacement cascade «Supervitrification»

17 Enthalpy Enthalpy Understanding of glass behavior under alpha decays 1. Balistic step : disordered state 2. Relaxation step : very important quenching rate Irradiated zone has a higher fictive temperature Fictive Temperature, C E Maugeri et al, J. Am. Ceram. Soc. 95 (2012) 2869 Tf Tf 0 Tf Sat 1 exp( V c D) Irradiated Glass Cumulative Dose, a-decays g -1 Pristine glass Model of accumulation of ballistic disordering fast quenching events: supervitrification Stabilization of a new glass structure when all the volume has been damaged once Open questions: Which step control the irradiated state? T f T f T f Energy deposition step, quenching step? Any rôle of alpha particle? CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 17

18 Thank you for your attention!!! Special Thanks to DHA - Atalante CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 18

19 Enthalpy - Slight modification of density and mechanical properties - Glass is still homogeneous (SEM and TEM scale) - No effect on initial alteration rate - Modification of glass Short Range Order (boron coordination, NBO ) - Modification of Medium Range Order (ring statistic, angle distribution) - No effect of accelerating the time scale Modifications observed in the first 4x10 18 a/g according to a direct impact model (1 st approx) Conclusion on alpha decays effects Saturation when all the glass has been damaged by recoil nuclei events and alpha particles Recoil nuclei : supervitrification of the glass (1&2) Alpha particles : partial repair of the damage (3&4) Double ion beam irradiation is necessary to accurately simulate the aging under α decays Prospects : Coupling alpha and beta decays and thermal history x x x x x x x x x x10 19 CEA/DEN/MAR/DE2D/SEVT S. Peuget ThermoMatHT 19 a R Density variation (%) Heavy ion supervitrification Final α decays damage state Pristine state α particle thermal spike 3 α particle recovery effect T fp 0.04CmSON68 0.4CmSON68 1.2CmSON CmSON68 exponential law Alpha decay dose (a/g) RN Balistic damage T fαd T frn