Glass - Back to the Future!

Presenting Author:
Judith Renaud

article posted 04 April 2016

Judith Renaud I am a 2nd year PhD student working on dissolution kinetics and mechanisms of crystals in nuclear glass melt at the department of study and new development of nuclear matrix at the CEA, at the site of Marcoule in France. After two years of intensive courses in Physics and Mathematics, I have obtained in 2014 an engineering degree, at the National School of Geology, and a master’s degree, at the Centre de Recherches Pétrographiques et Géochimiques in the field of geology with a specialization in magmas and deep fluids, both at the University of Lorraine in France.

Dissolution kinetics of apatites in borosilicate glass melt

J. Renaud*1, E. Régnier1, F. Faure2, H-P. Brau3, X. Le Goff3, O. Pinet1
1- CEA, DEN, DTCD, SECM/LDMC-Marcoule, F-30207 Bagnols-sur-Cèze, France
2- CRPG, CNRS, Université de Lorraine, 54501 Vandœuvre-lès-Nancy, France
3- ICSM, L2ME, F-30207 Bagnols-sur-Cèze, France

In France, High-Level radioactive Wastes (HLW) coming from nuclear spent fuel treatment are contained in a homogeneous sodium-borosilicate glass at the La Hague reprocessing plant. High Level Waste vitrification consists in the incorporation of fission products and minor actinides in a borosilicate glass melt at high temperature. In order to obtain the glass homogeneity, crystallized phases formed at different stages of the melting process have to be dissolved before pouring the glass in the canister. Nucleation and growth of these phases have already been studied (Delattre 2013, Orlhac 2001, Fillet 1997) but, to date, few studies on their dissolution in nuclear glass melt have been performed.

The presented study focuses on dissolution kinetics of apatites (Ca2Nd8(SiO4)6O2 type) in two types of simplified sodium-borosilicate glass melts: a simplified UOx glass and a Nd-enriched glass. Because of the volatility of B and Na at high temperature, experiments were made in closed systems using platinum capsules. Crystals features (size, number, morphology, composition) are followed as a function of time at different temperatures around liquidus temperature, by SEM coupled with image analysis and microprobe. Influence of initial crystallized state (size particles, crystallization fraction, crystals morphologies…) on dissolution kinetics is also studied. Results on dissolution kinetics and influence of the above parameters on these kinetics will be presented.

Delattre O., Régnier E., et al. (2013). "Image analysis study of crystallization in two glass compositions of nuclear interest." Journal of Non-Crystalline Solids 379: 112-122.

Orlhac X., Fillet C., et al. (2001). "Determination of the crystallized fractions of a largely amorphous multiphase material by the Rietveld method." Journal of Applied Crystallography. 34: 114-118.

Fillet C., Dussossoy J.L., et al. (1997). "Characterization of a glass sample from the T7 vitrification facility.” International Conference on Future Nuclear Systems, Yokohama, Japan.