Projects
Geochemical Testing and Model Development - Residual Tank Waste
The goal of this project is to provide source-term release models for contaminants of concern present in residual sludge that will remain in tanks at the Hanford Site. The contaminant release models are components of the long-term performance assessments being performed as part of the Tank Closure Project.
Following removal of as much material as possible from the tanks, a sample of the residual sludge is collected and provided to Pacific Northwest National Laboratory (PNNL) for testing and development of contaminant release models. Testing includes the following:
- Leaching tests
- X-ray diffraction analysis
- Scanning electron microscopy/energy dispersive spectroscopic analysis
- Selective extractions to identify the rate of release of contaminants from the sludge and the likely solid phases containing the contaminants.
All data are used to develop a mechanistic model, if possible, or at a minimum, an empirical model of contaminant release that will occur over the long term after tank closure.
This work provides actual release data for each individual tank rather than an estimate based on the history of tank filling and retrieval. The sludge characterization work also provides assurance to all stakeholders that sufficient work has been conducted to understand the material properties of the sludge that will remain in the ground.
Results of this work will provide a detailed characterization of the chemical and mineralogical properties of the residual tank waste and contaminant release models for use in the Tank Closure Project performance assessments.