Frit Development Efforts for Sludge Batch 4 (SB4): Model-Based Assessments

Peeler, D. K. ; Edwards, T. B.

Savannah River Site (S.C.)

关键词: Sludges;    Radioactive Waste Processing;    Sulfates;    Hydroxides;    Process Control;   

DOI  :  10.2172/881520
RP-ID  :  WSRC-TR-2005-00103
RP-ID  :  DE-AC09-96SR18500
RP-ID  :  881520

美国|英语

来源: UNT Digital Library

【 摘 要 】

The model-based assessments of nominal Sludge Batch 4 (SB4) compositions suggest that a viable frit candidate does not appear to be a limiting factor as the Closure Business Unit (CBU) considers various tank blending options and/or washing strategies. This statement is based solely on the projected operating windows derived from model predictions and does not include assessments of SO{sub 4} solubility or melt rate issues. The viable frit candidates covered a range of Na{sub 2}O concentrations (from 8% to 13%--including Frit 418 and Frit 320) using a ''sliding Na{sub 2}O scale'' concept (i.e., 1% increase in Na{sub 2}O being balanced by a 1% reduction in SiO{sub 2}) which effectively balances the alkali content of the incoming sludge with that in the frit to maintain and/or increase the projected operating window size while potentially leading to improved melt rate and/or waste loadings. This strategy or approach allows alternative tank blending strategies and/or different washing scenarios to be considered and accounted for in an effective manner without wholesale changes to the frit composition. In terms of projected operating windows, in general, the sludge/frit systems evaluated resulted in waste loading intervals from 25 to the mid-40%'s or even the mid-50%'s. The results suggest that a single frit could be selected for use with all 20 options which indicates some degree of frit robustness with respect to sludge compositional variation. In fact, use of Frit 418 or Frit 320 (the ''cornerstone'' frits given previous processing experience in the Defense Waste Processing Facility (DWPF)) are plausible for most (if not all) options being considered. However, the frit selection process also needs to consider potential processing issues such as melt rate. Based on historical trends between melt rate and total alkali content, one may elect to use the frit with the highest alkali content that still yields an acceptable operating window. However, other constraints may restrict access to higher waste loading or the proposed blending option being considered (e.g., sulfate content of the high-level waste and/or Chemical Processing Cell (CPC) issues may necessitate a more-washed sludge).