Vitrification: Putting the Heat on Waste
Dr. S.K. Sundaram
For centuries, glass has had many uses ranging from containers and windows for residences and commercial buildings to ornamental lamps and jewelry. Recognizing the versatility and durability of glass, scientists have adapted it to "vitrify" or permanently immobilize radioactive wastes at the Hanford Site and elsewhere for safe permanent disposal.
Vitrification is a proven method of waste disposal that combines waste materials with glass-forming chemicals to form molten glass that then solidifies, immobilizing the waste. The final waste form resembles obsidian and is a non-leaching, durable material that effectively traps the waste inside. Dr. Sundaram elaborated on the vitrification process, which included pretreatment, formulation and melting, and the importance of each step in ensuring the waste is immobilized in an acceptable waste form that meets all the requirements for safe disposal.
Dr. S.K. Sundaram, a materials scientist at Pacific Northwest National Laboratory, presented an overview of vitrification-its history, the science behind it, and the innovative technologies that have been developed-at the Community Science and Technology Seminar Series event on Wednesday, March 19, 7 p.m., at the Columbia Basin College Theater. The seminar, sponsored by PNNL and CBC, was free and open to the public.
Vitrification has been selected as the prime technology to immobilize and safely dispose of the radioactive waste generated by weapons production and nuclear research stored at several sites around the country for as long as 50 years. At Hanford, the waste has been stored in single and double shell tanks. 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. Some of the tanks have leaked.
"As scientists, we have a responsibility to find solutions to the 'legacy' waste problem confronting present and future generations," Dr. Sundaram said. "Vitrification is an ideal technology for immobilizing the wastes at Hanford and elsewhere. It is adaptable to changes in the composition of the waste while still offering the desired waste form properties."
PNNL has been involved in vitrification research and development for more than 30 years. A good share of the Laboratory's work in vitrification has focused on developing formulations that produce effective and durable waste glass and optimize the vitrification process. Among the innovative technologies developed by researchers at PNNL (independently as well as in collaboration) are slurry-fed joule-heated melter, in situ (in place) vitrification, dc plasma arc melter, fast glass, and the MilliViscometer, an advanced diagnostic technique that won an R&D 100 Award in 2001 as one of the year's 100 top innovations.
Because of its expertise, PNNL is providing ongoing research and engineering support to Bechtel National as it moves ahead with construction of the vitrification plant to immobilize the radioactive waste stored in the tanks at Hanford.
Dr. Sundaram joined PNNL in 1994 and is currently involved in three major areas of research. In the area of millimeter/submillimeter wave technology, he has made significant contributions by developing advanced techniques for non-contact measurement of materials properties and process parameters in adverse environments. He is currently working on integrated infrared photonic materials and devices. He's also generating international interest in the emerging area of ultrafast (femtosecond/attosecond) materials science and engineering. He was invited by the National Academy of Engineering to attend the Frontiers of Engineering program (that honors 100 of the nation's outstanding young engineers from industry, academia, and government annually) in 2001. Dr. Sundaram has a Ph. D. from the School of Materials Science and Engineering at Georgia Institute of Technology in Atlanta. He is also a Visiting Scientist with Plasma Science Fusion Center at Massachusetts Institute of Technology and a Visiting Scholar with Department of Engineering and Applied Sciences at Harvard University.
The Community Science and Technology Seminar Series is supported by the Columbia River Exhibition of History, Science and Technology and by the local chapter of Sigma Xi, the international honor society of scientific and engineering research.
