Use of Evaporative Fractional Crystallization in the Pretreatment Process of Multi-Salt Single Shell Tank Hanford Nuclear Wastes

Abstract

The purpose of the work described in this thesis was to explore the use of fractional crystallization as a technology that can be used to separate medium-curie waste from the Hanford Site tank farms into a high-curie waste stream, which can be sent to a Waste Treatment and Immobilization Plant (WTP), and a low-curie waste stream, which can be sent to Bulk Vitrification. The successful semi-batch crystallization of sodium salts from two single shell tank simulant solutions (SST Early Feed, SST Late Feed) demonstrated that the recovered crystalline product met the purity requirement for exclusion of cesium, sodium recovery in the crystalline product and the requirement on the sulfate-to-sodium molar ratio in the stream to be diverted to the WTP. In this thesis, experimental apparatus, procedures and results are given on scaled-down experiments of SST Early Feed for hot-cell adaptation along with operating parameters and crystallization mechanism studies on early feed multi-solute crystallization. Moreover, guidance is given regarding future steps towards adapting the technology to multi-salt crystallization kinetic parameter estimates and modeling.

Crystallization, Evaporative Fractional Crystallization, Nuclear Waste Pretreatment, Cesium Removal, Hanford, SST Early and Late feed, Multi-solute, Multi-salts, Simulant Testing