Structure and chemical properties of surface layers developed on R7T7 simulated nuclear waste glass altered in brine at 190°C
Abdelouas, Abdesselam; Crovisier, Jean-Lοuis; Lutze, Werner; Müller, Regina; Bernotat, Walter
European Journal of Mineralogy Volume 7 Number 5 (1995), p. 1101 - 1114
published: Oct 5, 1995
manuscript accepted: Apr 19, 1995
manuscript received: May 13, 1994
ArtNo. ESP147050705006, Price: 29.00 €
Abstract samples of R7T7 nuclear waste glass were leached for 35, 120 and 427 days at 190°C in NaCl dominated brine. The alteration layer at the glass surface consisted of a mixture of amorphous and crystalline phases. The amorphous phase retained Zr, U and Nd. The crystalline reaction products were: powellite, coffinite, analcime, quartz, barite, anhydrite and saponite. Neodimium and uranium were respectively immobilized essentially in powellite and coffinite phases, which are stable for more than 1 year. The chemical composition of the alteration layer did not appear to vary significantly between 35 and 427 days. The calculated chemical budgets show that the loss of elements to the solution decreases with increasing reaction progress (dissolved glass per solution volume) due to the precipitation of the secondary phases. The results of the electron microscopy analysis of these laboratory experiments agree well with the in situ alteration results of R7T7 glass in an underground saline environment in the Salado Formation of New Mexico (WIPP Project).