LFCM vitrification technology: Quarterly progress report, July-September 1987

Abstract

This report is compiled by the Nuclear Waste Treatment Program (NWTP) and the Hanford Waste Vitrification Program (HWVP) at Pacific Northwest Laboratory (PNL)(a) to describe the progress in developing, testing, applying and documenting liquid-fed ceramic melter vitrification technology. Progress in the following technical subject areas during the fourth quarter of FY 1987 is discussed: melting process chemistry and glass development, feed preparation and transfer systems, canister filling and handling systems, and process/product modeling and control.Melting Process Chemistry and Glass Development -Two alternatives were evaluated for providing increased flexibility in the processing and composition of the HWVP pretreated neutralized current acid waste (NCAW). The first involved adjusting the HWVP reference frit to allow for additional sodium from the waste while maintaining the glass composition. The second alternative addressed adding Si0 2 or sodium in place of part of the frit to adjust the temperature at which the melt viscosity is 100 poise (TIOOP). The use of compositional ratios (the ratios of selected glass components to other glass components), such as the ratio of total alkali oxides to Si0 2 , to predict the TlOOP of a melt based on composition was also evaluated.This study showed that up to 5 wt% Na 2 o can be removed from the HW-39 frit composition and still maintain a commercially producible frit. This would allow for up to a 20 wt% increase of Na 2 o in the NCAW'84 waste (from 11.1 to 31.1 wt% Na 2 0J, an approximate 16 wt% increase in the NCAW'86 waste (from 17.2 to _33.5), without changing the glass composition.Glass compositional ratios were found to provide a good method of estimating the TlOOP of glass melts based on composition. The ratios using the total weight percent of alkali oxides over the sum of the weight percents of Si0 2 , Al 2 o 3 , and Zro 2 were found to predict the TIOOP sufficiently for glass development, feed rheology studies, melter testing, and potentially for HWVP process control. (a) Operated by Battelle Memorial Institute for the Department of Energy under Contract DE-AC06-76RLO 1830 ; ; ;The addition of Si0 2 or sodium in place of some portion of the frit can adjust feed compositions. Feed compositions that would yield glass viscosities outside the range required for melter operation could be adjusted to a composition that would give a glass viscosity acceptable for melter operation.PNL is exam1n1ng the effects of composition, ferrous/ferric ratio {redox state), heat treatment, and groundwater on the chemical durability of a glass proposed for solidification of West Valley nuclear waste. Several experiments have been conducted, and preliminary results are given.The results of the experiments conducted to date indicate that waste glass is more durable in groundwater than in deionized water; also, durability is affected by isothermal and simulated canister cooling heat treatments.However, the durability of the waste glass is not strongly affected by the variation of glass ...