Engineering-Scale Evaluation of Flushing Requirements for High-Level Liquid Waste at Savannah River and Hanford Sites - 23167

In the U.S. Department of Energy's (US DOE) Savannah River Site (SRS) and Hanford site, systems of pipelines transport high-level radioactive liquid waste for waste processing and storage. After transporting the waste, the lines are flushed with water to ensure that no sludge or sludge solid sediments remain in the transfer line. Current guidelines that establish a minimum flush volume and flush water velocity required for post-transfer flushing operations to achieve a satisfactory cleanliness exist; however, the Defense Nuclear Facilities Safety Board (DNFSB) indicated a need for further investigation on the technical basis for the prescribed guidelines. Consequently, further studies that will assist SRS and Hanford in waste remediation are being done to optimize the operational conditions. This optimization would minimize the flush volume and consequent downstream waste, which ultimately would assist in preserving tank storage, preventing secondary waste processing, and minimizing changes to the waste's chemistry and rheology. To perform these investigations, an expandable, 76.2 mm (3 in.) carbon steel experimental pipe loop was designed and constructed at Florida International University (FIU) to simulate flushing operations of nonradioactive slurries. The test loop was designed to simulate sediment beds of solid materials and bed heights to investigate what parameters affect the efficiency of flushing operations at various concentrations. Testing was then conducted using non-Radioactive kaolin-water slurry simulants at various concentrations with various flush volume and flush modes to determine the effect of flush volumes for each configuration. These concentrations offer repeatability within the sediment beds inside the pipeline for fully-flooded and gravity-drained conditions with one day, one week, and two-week sedimentation. By parameterizing the sediment height and conditions, the flush volume and flush velocity values could be optimized, which leads to satisfactory cleaning of transport lines of varying length with a minimal use of flush water. This paper presents the latest efforts in flush analyses to determine the efficiency of flushing operations. New data with the various configurations for the first of four expansions of the test loop at 100.5 meters (330 feet) will be presented. This data, which approximates a flush-line volume ratio (FTLV) for fully flooded and gravity-drained conditions with one day, one week, and two week sedimentation at a range from 2.479 to 3.081, will also be compared to the results from the 50.2 meter (165 feet) loop. (authors)