Retention of sulfur, phosphorus, chlorine, and fluorine in Hanford Phase II vendor LLW glasses

Twelve Hanford Site underground storage tank low-level waste (LLW) glasses with significant different compositions were prepared in laboratory crucibles at temperatures of 1140 to 1440 degrees C. The batch materials for these glasses had P2O5, SO3, Cl, and F contents as high as 2.52, 1.01, 0.64, and 0.82 wt% respectively on a nonvolatile oxide basis. These glasses were melted without significant phase segregation or foaming and have acceptable chemical durability. The P2O5 concentration was retained at almost 100% in the glasses. The SO3 retention in the glasses depends on glass composition, melting temperature, and the redox condition of the melt. Glasses with high CaO content (9 wt%) and no boron had the highest retention of 1.01 wt% SO3, while glasses with a low content of nonbridging oxygen bonds had SO3 retention as low as 0.59 wt%. Lower temperature is more favorable for SO3 retention in the glass. More oxidizing conditions favor higher sulfur solubility in the glasses. The retention of fluorine in glass was determined mainly by the CaO content in glass and not much by melting temperature. Glasses with high CaO content (4 to 9 wt%) retained almost all the fluorine in the glasses at 0.82 wt%, while glasses with CaO content of less than 2 wt% retained 25% less fluorine at 0.63 wt%. On the other hand, the chlorine retention seems mainly to be determined by melting temperature, and not much by glass composition for these glasses with constant alkali contents. A glass melted at 1130 degrees C retained 78% of the chlorine in the glass to a level of 0.5 wt%, while another glass melted at 1410 degrees C retained only 30% of the chlorine in the glass at 0. 19 wt%