PNNL

Abstract

A portion of Hanford tank 241-AW-106 (referred to herein as AW-106) waste was retrieved by Hanford Tank Waste Operations and Closure (H2C) and transferred to Pacific Northwest National Laboratory (PNNL). Compared to previously received and vitrified wastes (AP-107, AP-101, AN-107, AW-105, and AP-105), there were no extreme analyte concentrations in the AW-106 waste, but rather all major analytes were in the middle of their concentration ranges. The AW-106 waste went through dilution in the laboratory by blending with Columbia River water to reach an actual sodium (Na) concentration of 5.5 M, solids filtration, and cesium removal by ion exchange. A glass composition and glass forming chemical (GFC) additions were calculated from the Kim et al. glass models[1] to satisfy the WTP baseline requirements based on analysis of the AW-106 sample received by PNNL (prior to dilution) and the target dilution to 5.5 M Na. A simulant version of this melter feed was calculated based on the understood best-basis inventory of tank AW-106 and batched. As preparation for the processing of the AW-106 waste melter feed, the simulant version was subject to property testing for rheology, expansion/bubbling, and evolved gas. No concerns arose during the property testing so the AW-106 simulant melter feed was then processed in a non-radioactive, continuous laboratory-scale melter (CLSM) system to understand production expectations. The AW-106 simulant melter feed was charged into the CLSM for 6.13 h of processing, which produced 6.66 kg of glass, for an average glass production rate of 2305 kg m 2 d 1 without any issues pumping the slurry or visual anomalous behavior during vitrification. During CLSM processing, evolved-gas equipment was connected to the CLSM offgas treatment system to monitor the partial pressure of gases when glass was poured. Since there were no processing issues with the AW-106 simulant melter feed, the actual AW-106 waste melter feed was then processed in a CLSM system built into a contamination area in a radioactive environment. The melting behavior characteristics appeared similar for both the simulant and waste melter feeds. The AW-106 waste melter feed was charged into the CLSM for 5.80 h of processing, with a ~3 h idling period for offgas management, which produced 6.13 kg of glass, for an average glass production rate of 2245 kg m¬2 d 1. A 3-hour idling time period in the middle of the operation afforded the opportunity to measure the change in content of semi-volatile components (99Tc, Cl, F, and S) in the melt glass pool. The processing rates for both the AW-106 simulant and waste were at the top of the ranges measured for melter feeds processed previously in the CLSM.