Radioactive Waste 326 - Researchers in England Find That Arsenic In The Soil Can Prevent The Migration Of Uranium From Old Mine
One problem with nuclear power that does not get much media attention is the aftermath of uranium mining. Once a mine is closed, there is a danger of groundwater migrating uranium out of the area of the mine and into the surrounding environment. New research has uncovered an important chemical interaction in the soil of one mine that shows that it may be possible to mitigate migration of uranium from old mines.
A research team led by the Department of Materials Science and Engineering at the University of Sheffield in the U.K. delved into the interaction of arsenic and uranium in the topsoil around the old abandoned South Terras uranium mine in Cornwall, England. The mine operated between 1873 and 1930. It produced a total of 736 tons of uranium during its lifetime.
The team utilized some of the brightest synchrotron X-ray microscopes in the world including the Swiss Light Source and the USA's National Synchrotron Light Source. This type of microscope uses X-rays to image an area with a diameter of one-millionth of a meter. What they found was the first evidence of arsenic controlling uranium migration.
Neil Hyatt, co-author of the study, said: “We use synchrotron X-rays to identify and isolate the microscopic uranium particles within the soils and determine their chemical composition and mineral species.” “It's like being able to find tiny uranium needles in a soil haystack with a very sensitive metal detector.”
The study found that the extraction of ore and natural weathering of rock at the South Terras mine resulted in the release of a variety of elements during the degradation which included large quantities of arsenic and beryllium. Arsenic and uranium formed a secondary mineral called metazeunerite which is very insoluable.
The study said that “Significantly, our data indicate that metazeunerite and metatorbernite were found to occur in solid solution, which has not been previously observed at other uranium-contaminated sites where uranyl-micas are present.” Claire Corkhill, the lead author of the study, said: "Locking up the uranium in this mineral structure means that it cannot migrate in the environment.”
One major conclusion of the study was that the process found at the South Terras mine was probably the result of a “rather unique” set of geological conditions. The study said that “To identify this remediation mechanism at other sites, where arsenic and uranium are key co-contaminants, further detailed mineralogical assessments are required.” “These should be considered as an essential input to understand the ultimate environmental fate of degraded uranium ore.
This study has very important implications that range from the remediation of abandoned uranium mines around the globe to the environmental cleanup of nuclear accidents and nuclear weapon test sites. The research team said that their work “…also shows the importance of local geology on uranium behavior, which can be applied to develop efficient clean-up strategies.” There are many highly contaminated sites around the world which could ultimately benefit from the deployment of techniques based on the findings of this study.
