PNNL

Abstract

In the past several years, cross-flow filtration has been studied extensively in a bench-scale system at Pacific Northwest National Laboratory (PNNL) using both actual tank waste from the Hanford site and waste simulants. One challenge when creating a waste simulant is duplicating the filtration behaviour of real waste, in particular when the waste composition is not known with certainty. Using a systematic approach to filtration testing, it has been found that the solid components that dominate the filtration behaviour can be identified. This approach was used to develop a waste simulant for S-Saltcake tank waste. The analysis of filtration data assists in screening solid components when the chemical composition and structure of a metal is not known. This is well-illustrated in this study during the search for the appropriate chromium phase. After the likely components were identified, the solids were combined with a supernate that is representative of the real waste and the filtration performance was verified against real waste data. A secondary benefit of this approach is the construction of a database of filtration performance for various solid species that can be used to quickly develop waste simulants in the future.