Laboratory science and technology contributing to environmental mission
With the end of the Cold War and the nonproliferation treaties that followed, the United States was faced with a new challenge arising from its nuclear armament efforts: dealing with a legacy of radioactive waste and contaminated areas at sites formerly used for nuclear research, development, production and testing.
The Department of Energy, a governmental offshoot of the Atomic Energy Commission, inherited responsibility for this challenge. DOE's environmental quality mission is focused on treating and disposing the waste, remediating contaminated facilities and restoring those affected environments.
Pacific Northwest National Laboratory is delivering science and technology that helps DOE accomplish this mission. Through its research, Pacific Northwest is building new knowledge that can lead to science-based solutions that are effective, efficient and safe.
In the era of armaments, scientists were aware of the hazardous nature of radioactive materials and the byproducts of plutonium production, but at the time they were unable to determine or fully understand the exact nature or level of the hazards. While much of the hazardous waste materials were contained, some radioactive materials got into the soil and traveled through the ground, spreading the contamination.
What lies beneath
In its role in DOE's Groundwater/Vadose Zone Integration Project at the Hanford Site in Richland, Wash., Pacific Northwest leads efforts to better understand how contaminants move through groundwater and the vadose zone—the area between the land surface and the underlying water table. By gaining new knowledge, this science-based program can lead to new ways to stop the migration of contaminants.
DOE created the Groundwater/Vadose Zone program in 1997 to ensure that decisions made on the Hanford Site in eastern Washington take an integrated approach to protecting the nearby Columbia River as well as water resources, the environment, users of river resources and river life. Located adjacent to the Hanford Site, Pacific Northwest is helping resolve key technical issues that help inform and support these cleanup decisions.
In addition to contaminants in the ground, plutonium production and nuclear research generated radioactive waste that has been in sealed environments at several sites around the country for as long as 50 years. The underground steel tanks designed to hold this waste material and prevent it from contaminating the surrounding environment were never intended to be a long-term solution. Today, some are showing their age and have begun to slowly leak.
Managing and relocating this waste material is another major environ-mental goal for DOE. Researchers at Pacific Northwest have led the field in research that applies the process of vitrification to the management of radioactive waste.
This proven method of waste containment combines waste materials with molten glass that then solidifies to hold the waste. The final substance resembles obsidian and offers a non-leaching, durable material that effectively traps the waste inside.
"Vitrification is an ideal candidate for waste immobilization," said John Vienna, a chief scientist in Pacific Northwest's process technology group. "It is adaptable to changes in the composition of the waste while still offering the desired properties."
Researchers at Pacific Northwest are focusing on several aspects of vitrification. In addition to working to improve the functionality of the chemical reactors currently used for this process at several waste management sites and developing new chemical reactor technologies, the scientists also are developing new methods for maximizing how much waste can be held in the glass.
"For each additional percent of waste included into the content of the glass, millions and millions of dollars are saved," said Ted Pietrok, team leader for DOE's Tanks Focus Area, the group that manages the science and technology solutions developed to remediate radioactive waste stored in underground tanks at sites nationwide. At Pacific Northwest, researchers and scientists involved in this program are striving to improve methods of waste management and increase the impact of research dollars through computer modeling and intensive laboratory benchwork.
Putting robots to work
Worker safety is critical in every project that deals with handling radioactive materials. Scientists at Pacific Northwest have developed a robotic crawler that can enter into potential "hot spots" and take readings of the contamination levels. This crawler, able to fit into small spaces and traverse uneven terrains has proven to be a crucial key in reducing or eliminating worker exposure.
The information that the robotic crawler can bring back will help keep workers safe and ensure that sound decisions based on scientific evidence are made. For example, in August a robotic crawler custom-built by Pacific Northwest engineers was used to characterize a 24-inch diameter drain line in Hanford's U-Plant, a former chemical processing plant. The robot deployment is part of an initiative to evaluate disposal alternatives for Hanford's five deactivated chemical processing facilities.
"Through the DOE's Office of Science and Technology program, Pacific Northwest's research, tools and technologies are contributing to science-based decisions and solutions at the nearby Hanford Site, as well as at sites across the nation," said Paul Kruger, DOE's Associate Manager for Science and Technology. Kruger's organization provides oversight to the Laboratory's science and technology. "I believe that with its extensive scientific and technological resources, the Laboratory will continue to provide breakthrough science and technology for years to come, truly helping the DOE achieve its environmental goals."
Special thanks to Rae Weil, contributing writer.