Basis for Selection of a Residual Waste Retrieval System for Gunite and Associated Tank W-9 at the Oak Ridge National Laboratory

Waste retrieval and transfer operations at the Gunite(trademark) and Associated Tanks (GAATs) Remediation Project have been successfully accomplished using the Tank Waste Retrieval System. This system is composed of the Modified Light-Duty Utility Arm, Houdini Vehicle, Waste Dislodging and Conveyance System, Hose Management Arm, and Sludge Conditioning System. GAAT W-9 has been used as a waste-consolidation and batch-transfer tank during the retrieval of sludges and supernatants from the seven Gunite tanks in the North and South tank farms at Oak Ridge National Laboratory. Tank W-9 was used as a staging tank for the transfers to the Melton Valley Storage Tanks (MVSTs). A total of 18 waste transfers from W-9 occurred between May 25, 1999, and March 30, 2000. Most of these transfers were accomplished using the PulsAir Mixer to mobilize and mix the slurry and a submersible retrieval-transfer pump to transfer the slurry through the Sludge Conditioning System and the ∼1-mile long, 2-in.-diam waste-transfer line to the MVSTs. The transfers from W-9 have consisted of low-solids-content slurries with solids contents ranging from ∼2.8 to 6.8 mg/L. Of the initial ∼88,000 gal of wet sludge estimated in the GAATs, a total of ∼60,451 gal have been transferred to the MVSTs via tank W-9 as of March 30, 2000. Once the waste-consolidation operations and transfers from W-9 to the MVSTs are completed, the remaining material in W-9 will be mobilized and transferred to the active waste system, Bethel Valley Evaporator Service Tank W-23. Tank W-23 will serve as a batch tank for the final waste transfers from tank W-9 to the MVSTs. This report provides a summary of the requirements and recommendations for the final waste retrieval system for tank W-9, a compilation of the sample analysis data for the sludge in W-9, and brief descriptions of the various waste-retrieval system concepts that were considered for this task. The recommended residual waste retrieval system for cleanout of tank W-9 consists primarily of the existing Tank Waste Retrieval System, which, is used in conjunction with a small surge vessel placed in one of the tank risers and a positive displacement pump installed inside the Primary Conditioning System containment box. Final cleanout of tank W-9 was initiated in July and successfully completed in September 2000. The performance of the selected residual waste retrieval system will be described in a follow-on report