July 18, 2000
UPTON, NY . Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have been awarded U.S. patent number 6,030,549 for inventing a process for encapsulating depleted uranium oxides in thermoplastic polymers. The process converts depleted uranium to a form that is both stable and safe for long-term disposal. The encapsulated uranium could also have several useful applications, including the production of radiation shielding and counter weights for airplanes, helicopters and ships.
Depleted uranium (DU) is a by-product of enriching uranium ore to make fuel for nuclear reactors. Storing DU requires labor-intensive and costly maintenance. The Brookhaven Lab process uses uranium oxide powder, a more stable, but dispersible compound, which is converted from the reactive form through chemical processing and combined with a thermoplastic binder. The final product can be formed into shapes and is cooled to form a dense solid.
"By creating safe, secondary end-use products from these materials, we are addressing health and safety, environmental protection, and waste reduction issues," says Paul Kalb, the Senior Research Engineer who is leading this work for Brookhaven's Environmental Research and Technology Division.
BNL's patented process for encapsulation requires simultaneous heating and mixing of depleted uranium powders and non-biodegradable thermoplastic polymers such as polyethylene or polypropylene. Virgin or recycled polymers can be used. The result is a homogeneous mixture of depleted uranium and molten thermoplastic polymer, which can be molded into any shape.
Tests performed by the Brookhaven scientists reveal that the new material, composed of anywhere from 10 to 90 percent depleted uranium by weight, is strong and durable. And because it is largely impermeable to water, it does not leach radioactive material. The heavy material can be molded to form counterweights/ballast for use in airplanes, helicopters, ships, missiles, flywheels, armor, and projectiles.
Because of the density of uranium, the product is also an excellent shield against gamma radiation. The presence of hydrogen in the plastic makes it an effective shield against neutron radiation as well. And since the product has a much lower percentage of fissionable uranium (U-235) compared with natural uranium ore, the levels of residual radioactivity are very low.
The material could therefore be useful in the construction of storage vaults and casks for radioactive materials or in providing protection for workers and the public at particle accelerator beamstops and targets.
"We are currently working with the Brookhaven Office of Technology Transfer to identify potential industrial partners and opportunities for commercial development," says Kalb. The research was funded by the U.S. Department of Energy.
The U.S. Department of Energy's Brookhaven National Laboratory creates and operates major facilities available to university, industrial and government personnel for basic and applied research in the physical, biomedical and environmental sciences and in selected energy technologies. The Laboratory is operated by Brookhaven Science Associates, a not-for-profit research management company, under contract with the U.S. Department of Energy.
Note to local editors: Paul Kalb lives
in Wading River, New York.