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INEEL Researchers Plant Experimental Monitors Under Savannah River Site's Low-Level Radioactive Waste

Date:
April 26, 1999
Source:
Idaho National E & E Laboratory
Summary:
Surface water and its piggybacking chemical riffraff seeps into the ground, traveling through a subsurface region called the vadose zone on its way to the aquifer. Little is known about the journey it takes through this zone. How the water and its baggage interact with the vadose zone will determine how much of the riffraff -- contaminants such as gasoline additives, agricultural chemicals, or buried nuclear waste leakage -- end up in our water supply.
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Surface water and its piggybacking chemical riffraff seeps into the ground, traveling through a subsurface region called the vadose zone on its way to the aquifer. Little is known about the journey it takes through this zone. How the water and its baggage interact with the vadose zone will determine how much of the riffraff -- contaminants such as gasoline additives, agricultural chemicals, or buried nuclear waste leakage -- end up in our water supply.

Researchers from the Department of Energy's Idaho National Engineering and Environmental Laboratory set up monitoring equipment at the Department's Savannah River Site in South Carolina mid-April. To identify where and how fast water is moving before it mixes with groundwater at the water table, hydrologists Buck Sisson and Joel Hubbell are developing tools to follow water and its passengers traveling through the zone.

At the Savannah River Site, their stationary equipment will patrol the vadose zone below the site's radioactive waste disposal trenches, watching for water and the contaminant tritium. For years, waste management engineers built containment trenches for low-level radioactive waste. "Savannah River's objective is to demonstrate that there's no tritium coming out of the trenches and going into the groundwater," said Sisson.

The INEEL scientists dug three 8-inch-wide wells 60 feet deep around several of Savannah River Site's trenches, in which they planted soil monitoring equipment every 15 feet. The equipment will measure three things: the water content of the soil, the concentration of tritium, and the soil tension -- or how tightly the soil holds water. Soil tension is an indication of how fast the water will percolate through the ground.

This project is a first for vadose zone research. "We're monitoring at a depth and in an environment that's never been done before," said Hubbell. "And the sensors will give us the information we need to tell us what's going on."

Measuring soil tension at these depths requires an instrument the researchers have developed here at INEEL. This device, called the Advanced Tensiometer, can measure soil tension much deeper in the ground than the two or three feet to which conventional tensiometers are limited.

Conventional tensiometers, mostly used by farmers and researchers, are limited by their design to the shallow depth. They employ a column of water in a long tube above a porous ceramic cup in the soil, which connects the cup to a pressure gauge at the surface. The water pressure within the cup equilibrates with the water pressure in the soil, creating a pressure within the water column that is measured with a standard pressure gauge. The water column's height is limited by gravity and responds slowly to changes in soil tension.

Sisson and Hubbell eliminate the column of water by using an electronic pressure transducer resting on a small, porous ceramic cup. Only enough water is needed to fill the cup, and the water is retained fourfold as long as in a water column tensiometer. The transducer is connected via wires to electronics above ground -- this allows measurements at depths limited only by the length of the wire.

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Materials provided by Idaho National E & E Laboratory. Note: Content may be edited for style and length.


Cite This Page:

Idaho National E & E Laboratory. "INEEL Researchers Plant Experimental Monitors Under Savannah River Site's Low-Level Radioactive Waste." ScienceDaily. ScienceDaily, 26 April 1999. <www.sciencedaily.com/releases/1999/04/990426062418.htm>.
Idaho National E & E Laboratory. (1999, April 26). INEEL Researchers Plant Experimental Monitors Under Savannah River Site's Low-Level Radioactive Waste. ScienceDaily. Retrieved March 28, 2024 from www.sciencedaily.com/releases/1999/04/990426062418.htm
Idaho National E & E Laboratory. "INEEL Researchers Plant Experimental Monitors Under Savannah River Site's Low-Level Radioactive Waste." ScienceDaily. www.sciencedaily.com/releases/1999/04/990426062418.htm (accessed March 28, 2024).

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