The Engineered Barrier System (EBS) represents one system in the performance of the Yucca Mountain high-level radioactive waste (HLW) repository to isolate and prevent the transport of radionuclides from the site to the accessible environment. Breached Waste Package and Drip Shield Experiments (BWPDSE) were performed at the Department of Energy's National Nuclear Security Administration Nevada Support Facility in North Las Vegas, NV in the A-1 lowbay between May 2, 2002 and July 25, 2002. Data collected from the BWPDSE will be used to support the flux splitting model used in Analysis and Modeling Report ANL-WIS-PA-000001 REV 00 ICN 03 EBS Radionuclide Transport Abstraction (BSC 2001a). Tests were conducted by dripping water from heights representing the drift crown or wall on a full-scale section of a drip shield with both smooth and rough surfaces. The drip shields had machined square breaches that represent the general corrosion breaches or nodes in the WAPDEG Analysis of Waste Package and Drip Shield Degradation AMR (CRWMS M&O 2000d). Tests conducted during the BWPDSE included: initial tests to determine the splash radius distances and spread factor from the line of drip impact, single patch tests to determine the amount of water collected in target breaches from splashing or rivulet flow, multiple patch tests to determine the amount of water collected in several breaches from both splashing and rivulet flow, and bounding flow rate tests. Supplemental data were collected to provide additional information for rivulet spread, pan evaporation in the test chamber, and water temperatures of the input water and drip shield surface water. The primary flow mechanism observed on both smooth and rough surfaces was rivulet flow, not film flow. Lateral rivulet spread distances were, in general, wider on the smooth drip shield surface than on the rough drip shield surface. There were substantial differences between the mechanisms of rivulet formation and movement on smooth and rough drip shield surfaces. Water collected in breaches was a function of the location of drip impact upstream from the target breach, i.e., impact breaches must be directly above or slightly to the side of the breaches in order for a substantial volume of water to collect in breaches. Splash droplets contributed a small portion of the water collected in breaches. Mass balances showed that evaporation from the drip shield was a large component of water loss. This was particularly manifested during low flow runs of the bounding flow rate tests where test duration was around five hours.
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