Laboratory stabilization/solidification of tank sludges: maximizing sludge loading

Area of Science:

• Environmental Science
• Chemical Engineering
• Waste Management

Background:

• Radioactive mixed-waste sludges accumulated over decades require treatment and disposal.
• Previous studies in this series focused on laboratory stabilization/solidification.
• This research addresses combining and treating sludges from different tank sets.

Purpose of the Study:

• To maximize sludge loading in grout formulations without a strength criterion.
• To evaluate stabilization of actual tank sludges and surrogates.
• To identify challenges in high-load stabilization of radioactive waste.

Main Methods:

• Laboratory testing of grout formulations with surrogate and actual tank sludge samples.
• Investigating hydrogel use to eliminate free water generation.
• Correlating contaminant performance (Cr, Hg, Pb) with grout composition and pH.

Main Results:

• Hydrogels eliminated free water at >90wt% sludge loading, but monolith strength was compromised.
• Surrogate testing indicated chromium and mercury performance depended on slag content, lead on pH.
• Actual sludge tests at high loadings showed unexpected lead and silver stabilization problems.

Conclusions:

• High sludge loading (>90wt%) is achievable with hydrogels, but may impact monolith integrity.
• Surrogate testing provides valuable insights but does not fully predict actual sludge behavior.
• Further research is needed to address lead and silver stabilization challenges in actual radioactive sludges.