Office of Environmental Management

Ancient Glass in Swedish Hillforts May Shed Light on Immobilizing Nuclear Waste

November 16, 2015

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The ruins of a Swedish hillfort site are shown here.

The ruins of a Swedish hillfort site are shown here.

A sign at a hillfort site explains, in the Swedish language, how the hillfort was constructed and how glass material was made at the site.

A sign at a hillfort site explains, in the Swedish language, how the hillfort was constructed and how glass material was made at the site.

RICHLAND, Wash. – EM’s Office of River Protection (ORP) is looking to the past to help with its future by studying how ancient glass has fared through the centuries and how it compares to the results of accelerated aging tests on various types of low-activity waste (LAW) glass.   

   The waste will be immobilized in glass through vitrification. In this process, radiological liquid waste is mixed with glass-forming materials heated to 2,100-degrees Fahrenheit. That mixture is poured into stainless steel containers where it cools to a sturdy glass form for eventual final disposition.

   ORP is partnering with DOE’s Pacific Northwest National Laboratory (PNNL), the Division of Waste Science and Technology at the Luleå University of Technology in Sweden, and the Smithsonian Institution’s Museum Conservation Institute to study ancient glass, ranging in age from 600 to 2,000 years old, to benchmark and validate accelerated aging tests of ORP’s vitrified LAW.

   This project is funded by EM’s International Program as part of a broader initiative to engage in mission-relevant research with countries having common interests. EM Lead Foreign Affairs Specialist Ana Han and EM International Programs Technical Advisor Rosa Elmetti manage EM’s International Program.

   The ancient glass, which has many of the same metal oxides that will be used in the glass formula for ORP’s vitrified LAW, is found in hillforts in Sweden and elsewhere in Europe. Hillforts are defensive structures located on natural earthen highpoints.

   Professor Rolf Sjöblom, who is also affiliated with Uppsala University as a faculty member in structural chemistry, will work with ORP to obtain the hillfort glass samples for testing. The Smithsonian will help with handling and analyzing these culturally- and historically-significant samples. Other analytical methods will be employed at PNNL.  

   Smithsonian research scientist Dr. Edward Vicenzi also has experience with natural and experimental glasses, and has characterized a set of archeological reference glasses to help with the study.  

   Knowing how the hillfort glass have weathered the elements will allow a better understanding of how the vitrified LAW and its similar glass formula will stand up in hundreds or thousands of years. Various tests will be done on ORP’s vitrified waste form (glass), including the one which will be developed by ORP, University of Sheffield, and Vanderbilt University to simulate accelerated aging of the glass. 

   “The hillfort glass allows us to observe at ambient conditions how glass deteriorates over time and we can compare it to our accelerated test,” explained Albert Kruger, ORP’s glass scientist. “The accelerated aging test we hope to develop will be based upon an Environmental Protection Agency’s (EPA) SW-846 validated method for RCRA applications.” 

   RCRA stands for the Resource Conservation and Recovery Act of 1976, which is the principal federal law in the U.S. governing the disposal of solid waste and hazardous waste. SW-846 is an EPA test method.

   “This will provide the Environmental Protection Agency and Washington State Department of Ecology, which provides regulatory oversight of the project, greater confidence in the test results,” said Kruger. “Ultimately we will apply the tests to glasses produced with nuclear materials of greatest interest and finally from glasses produced from tank waste samples.”

   Not only will the work done by ORP help with its mission of vitrifying LAW, but it will also further research on the Swedish hillforts. This testing could provide insight into the long-term preservation and historical interpretation of the vitrified hillforts material, much of which is still under debate among archaeologists.