A kinetic approach of sulphate behaviour in borosilicate glasses Implications for sulphate incorporation in nuclear waste glasses

A kinetic approach of sulphate behaviour in borosilicate glasses Implications for sulphate incorporation in nuclear waste glasses Marion LENOIR 1,3, Agnès GRANDJEAN 2, D.R. NEUVILLE 3 1 CEA/ Nuclear Energy Division/ Waste Treatment and Conditioning Department/ Marcoule, France 2 Institut de Chimie Séparative de Marcoule, France 3 Physique des Minéraux et des Magmas, UMR 7047, CNRS- Institut de Physique du Globe de Paris, France

Contents Background of the study Sulphate quantification in a borosilicate glass using Raman spectroscopy Kinetics of sulphate decomposition using in situ Raman spectroscopy Conclusion and future works

Sulphur in oxide glasses Sulphur added to commercial glasses - as sulphate (Na 2 SO 4 ): refining agent - as sulphide (with iron): amber colour Sulphur in silicate melts : a great geological interest sulphur is a volatile component of magmatic systems Sulphur in radioactive wastes - comes from residuals of incineration, of ion-exchanging resins, or effluents of radioactive solutions - low solubility in borosilicate glasses (1 to 2 mol%) - volatile component 5 cm www.maisonradical.ca Earthobservatory.nasa.gov/

Contents Background of the study Sulphate quantification in a borosilicate glass using Raman spectroscopy Kinetics of sulphate decomposition using in situ Raman spectroscopy Conclusion and future works

Experimental procedure melting of three borosilicate glasses Compound SiO 2 (mol%) B 2 O 3 (mol%) Na 2 O (mol%) SBNa 53-20 53.34 26.66 20 BaO (mol%) SBNa 47-30 47 23 30 SBBa 22.33 22.22 44.44 33.34 addition of 10 wt% of Na 2 SO 4 or BaSO 4 the sulphate layer is removed obtention of a glass with only SO 3 dissolved in the vitreous matrix glasses with different sulphate contents are obtained calibration with Raman spectroscopy

Raman spectroscopy Experimental procedure: Source = 514.532 nm line of a coherent 70 Ar + laser. Spectral resolution = ± 1 cm -1 Spatial resolution = around 1µm 3 Integration time=300s Advantages : - fast and flexible technique - non destructive method T64000 Jobin-Yvon IPGP - high temperature measurements/ in situ measurements

Effect of sulphate on Raman spectra 1 2 1= SBNa 53-20 2= SBNa53-20 with Na 2 SO 4 Na 2 SO 4 Raman spectra of glasses with differents sulphate contents Raman Intensity (a.u.) 350 t=39min t=102 min t=230 min 300 t=285 min t=405 min 250 t=1395 min 200 150 100 50 0 ν 1 S-O stretching sulphate (around 990 cm -1 ) 900 950 1000 1050 1100 1150 1200 1250 wavenumber (cm -1 )

Deconvolution of Raman spectra Sodium borosilicate glass Sodium borosilicate glass + Na 2 SO 4 Si-O stretching vibrations Stretching sulphate band (around 990 cm -1 ) 1500 Raman Intensity (a. u.) 300 200 100 0 Q 2 Q 3 Q 4 Raman Intensity (a.u.) 1200 900 600 300 0 900 1000 1100 1200 wavenumber (cm -1 ) Q 0 Q 1 Q 2 Q 3 Q 4 900 1000 1100 1200 wavenumber (cm -1 ) 1 aire [ ] ( 990cm ) SO3 glass α aires( bandes)

Quantification of the amount of sulphate using Raman spectroscopy Calibration curves: comparison between microprobe measurements of the sulphate content in the glass and Raman areas of the sulphate band

Contents Background of the study Sulphate quantification in a borosilicate glass using Raman spectroscopy Kinetics of sulphate decomposition using in situ Raman spectroscopy Conclusion and future works

Kinetics of departure of sulphate 0.006 η =100 Poise (T=980 C) SBNa53-20 Intensity (arbitrary units) 0.005 0.004 0.003 0.002 0.001 0 min 700 min 0.000 900 1000 1100 1200 Raman shift (cm -1 ) - high temperature cell : a single PtRh alloy wire heated by Joule effect. Small hole. - quenching between each measurement - acquisition of Raman spectra at room temperature

Kinetics of departure of sulphate Kinetic study as a function of the viscosity of the glass SO 4 2- (melt) SO 3 (melt) + O 2- (melt) SO 3 (melt) SO 3 (gas) C( t) = Ceq + 0 t ( C C ) exp eq τ

Conclusion and future works sulphate content is quickly determined once the calibration is realised this technique allows in situ measurement of sulphate content electrical conductivity measurements kinetic study for different compositions of glasses

Thanks CEA Marcoule, DEN/DTCD/SECM/LDMC, France - Bruno Pénelon - Nicolas Bousquet - Andrew Connelly Institut de Chimie Séparative de Marcoule - Nicolas Clavier Institut de Physique du Globe, Paris CEA Marcoule,France - Benjamin Cochain CEA Saclay, DMN/SRMP, France - Sylvie Poissonnet CEA Pierrelatte, France - Emmanuelle Brackx Thank you for your attention