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Migration ’09 Convenes Near Site Of Early Nuclear Technology

September 21, 2009

Details about how uranium and plutonium move around underground suggest ways to stop them

Researchers from around the world will be presenting at Migration ’09: 12th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere. The meeting is being held near one of the pioneer locations of nuclear technology, the Hanford Site .

Migration ’09 will focus on recent developments in the fundamental chemistry of radioactive elements known as actinides from the molecular level to field scale. Researchers will present new ways of imaging the interface of minerals and water, and new computational approaches will be a theme running through the conference. The presentations include:

Stuck at Five: Uranium gets stuck at an intermediate point when magnetite converts it between oxidation states

Uranium takes several forms under conditions commonly found in contaminated earth. Uranium (VI) can move around a lot underground. But if uranium is converted to another oxidation state known as uranium (IV), the contaminant will stay in place. Researchers want to use ferrous iron, which permeates soils and the subsurface, to help in this conversion. However, laboratory work has suggested that using the ferrous iron-containing mineral magnetite doesn’t always convert uranium (VI) to uranium (IV). PNNL researcher Eugene Ilton will present research showing that, under some conditions using magnetite, reduction of uranium (VI) gets hung up at uranium (V), a seemingly unusual oxidation state of uranium for systems that contain water. Although little is known about how easily this intermediate oxidation state of uranium travels through the subsurface, Ilton will discuss conditions that might stabilize it.

Reference: Eugene S. Ilton, John Bargar, Andrew R. Felmy, On the role of U (V) in the heterogeneous reduction of U (VI) to U (IV), Monday Sept. 21, 4:45 pm at the Three Rivers Convention Center

Charging Forth: Controlling how plutonium gets around

Under ground, where water is present, plutonium travels by forming colloids — nanometer-sized particles of plutonium dioxide covered in negatively charged ions suspended in water. Because these ions on the particle’s surface make it more or less mobile, Argonne National Laboratory chemist Richard Wilson and colleagues explored the surface’s chemical nature. Wilson will present data showing that the negatively charged ions can be manipulated on the surface, resulting in particles of a different charge. The particles’ chemistry in solution can also be altered. Wilson will discuss how these results can be exploited to control plutonium’s movement or possibly clean up the contaminant from certain environments.

Reference: Richard E. Wilson and Lynda Soderholm, The reactivity of the plutonium colloid surface: Implications for environmental transport, Tuesday Sept. 22, 2:45 pm at the Three Rivers Convention Center

From the beginning: Learning from the Hanford Site

One of the pioneer locations of nuclear technology, Hanford presents a unique environment in which to study nuclear contamination. The six presentations in this session will address issues such as the state of contamination in the soils and subsurface, what chemical and geochemical processes control the migration of contaminants, and the characterization of sludge in storage tanks.

Reference: Hanford Special Session, Wednesday Sept. 23, 8:30 a.m. to 10:55 a.m. at the Three Rivers Convention Center

Elsewhere: How other nations handle nuclear waste

Researchers will discuss the waste disposal programs in other countries besides the United States, including China, Korea, Sweden and Russia. These nations are considering different alternatives for the final disposal of their wastes — including engineered barrier and other systems that aim to keep radioactive contaminants apart from soils and water systems. Researchers from these countries will discuss the progress they’ve made in these areas, including the processes such as diffusion that transport ions in the subsurface.

Reference: International Research Programs, Friday Sept. 25, 10:50 a.m. to 12:10 p.m. at the Three Rivers Convention Center

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