The Impact of Higher Waste Loading on Glass Properties: The Effects of Uranium and Thorium

Peeler, D.K.

Savannah River Site (S.C.)

关键词: Thorium Oxides;    Waste Forms;    36 Materials Science;    Loading;    Mathematical Models;   

DOI  :  10.2172/820001
RP-ID  :  WSRC-TR-2003-00386
RP-ID  :  AC09-96SR18500
RP-ID  :  820001

美国|英语

来源: UNT Digital Library

【 摘 要 】

In this study, glasses are designed or selected to assess the impacts of U3O8 and ThO2 on various glass properties of interest. More specifically, glasses were fabricated in which Th replaced U (on a molar basis) to assess the impact of ThO2 on the durability response (as measured by the Product Consistency Test ) and viscosity. Based on the measured normalized boron release values, the results indicated that the Th-enriched glasses were less durable than their Ubased counterparts. Although molar substitution of Th or U had a negative impact, all of the glasses were more durable than the Environmental Assessment glass - the highest release being 7.39 g/L as compared to 16.695 g/L as reported for EA. With respect to model predictions, THERMOTM predicts that a molar substitution of thorium for uranium should increase glass durability. However, these data suggest that the signs and/or magnitudes of the Gi values associated with U3O8 and ThO2 are inconsistent with the theory on which the current model is based for the limited number of glasses tested. It should be noted that these glasses cover a narrow compositional region. With respect to the impact on viscosity, the data suggest that there may be a bias in the model. That is, the model currently does not contain a U3O8 or ThO2 term - but perhaps it should to account for their contributions to the measured (or actual) viscosity results. In addition, a series of glasses were produced to assess the impact of higher waste loadings on select glass properties. The PCT results suggest that durable glasses can be made at relatively high WLs (exceeding 40 wt percent). Comparisons between the measured PCTs and their predictions indicate that the current model is applicable, with all of the quenched glasses falling within the 95 percent confidence bands. The viscosity data for the higher WL glasses suggest that the current model may be extremely accurate for some systems but for different regions the model may be biased high or low - an observation that is consistent with that of Harbour et al. (1999).