Thursday, November 8, 2007 - 10:45 AM
341-9
Vadose Zone Monitoring Under an Interim Surface Barrier in Hanford.
Many of single-shell tanks and their associated infrastructure (e.g., pipelines, diversion boxes) in Hanford have leaked. Most of the radioactive contaminants from the leaks still reside within the vadose zone. A demonstrative surface barrier is to be emplaced in the T Tank Farm to prevent meteoric water from reaching the plume and moving it further. Due to the existence of radioactive contaminants, access to the site as well as sampling and digging are strictly controlled. Further, AC power is not available within the site. We used a solar-powered and remotely-controlled (SPARC) system to continuously monitor soil water and temperature conditions and the site meteorological condition. The system contained multiple equipment nests, which are powered by a 12-volt rechargeable battery, and a receiver that connected to a computer. The batteries are charged by a solar panel. Each equipment nest is composed of a capacitance probe, multiple heat-dissipation units and a datalogger. Data from the each of the dataloggers were transmitted remotely by a spread spectrum radio to the receiving computer. Additionally, a neutron probe access tube was included in each nest and quarterly manual measurements of soil water content using a neutron probe were carried out. This SPARC system combined with the manual neutron probe measurement was used to monitor the soil water condition in the soil with and without a surface barrier in Hanford T Tank Farm. From September 2006 (the time the SPARC system started in operation) to present (August 2007), the solar system could continuously provide sufficient power to the equipment. Data collected and stored in the dataloggers could be retrieved remotely any time. To date, the SPARC system has provided continuous high-quality data without unplanned interruption.
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