Polyethylene Encapsulated Depleted Uranium
Brookhaven National Laboratory (BNL) has completed preliminary work to investigate the feasibility of encapsulating DU in low density polyethylene to form a stable, dense product. DU loadings as high as 90 wt% were achieved. A maximum product density of 4.2 g/cm3 was achieved using UO3, but increased product density using UO2 is estimated at 6.1 g/cm3. Additional product density improvements up to about 7.2 g/cm3 were projected using DU aggregate in a hybrid technique known as micro/macroencapsulation. A U.S. patent for this process has been received.
Figure 1: DU Encapsulated in polyethylene
samples produced at BNL containing
80 wt % depleted UO3
A recent DU market study by Kapline Enterprises, Inc. for DOE thoroughly identified and rated potential applications and markets for DU metal and oxide materials. Because of its workability and high DU loading capability, the polyethylene encapsulated DU could readily be fabricated as counterweights/ballast (for use in airplanes, helicopters, ships and missiles), flywheels, armor, and projectiles. Also, polyethylene encapsulated DU is an effective shielding material for both gamma and neutron radiation, with potential application for shielding high activity waste (e.g., ion exchange resins, glass gems), spent fuel dry storage casks, and high energy experimental facilities (e.g., accelerator targets) to reduce radiation exposures to workers and the public.
Treatment of DU materials by polyethylene encapsulation is a desirable option because of the immediate availability of the technology and proven record to effectively and efficiently process similar powder and granular materials. In addition, the process is very flexible. Polyethylene products can be heated and reworked if future needs change. DU can also be retrieved from the encapsulated product by thermal processing if needed as a resource in the future. Recycled plastics from industrial or post-consumer sources can be used in place of virgin materials to reduce costs and produce valuable products entirely from recycled materials. BNL has extensively developed, tested and demonstrated polyethylene encapsulation processes for low-level radioactive, hazardous, and mixed wastes. During processing, waste materials are mechanically mixed into the molten polyethylene binder, producing a workable homogeneous product. The process is not susceptible to chemical interactions between the waste and binder, enabling a wide range of acceptable waste types, high waste loadings, and technically simple processing under heterogeneous waste conditions. The process has evolved from proof-of-principle, through bench-scale development and testing, to full-scale technology demonstration and technology transfer.
A prototype Polyethylene Encapsulated Depleted Uranium Transportation/Disposal cask has recently been fabricated to facilitate the disposal of a highly radioactive Ra/Be source being stored at BNL. Polyethylene Encapsulated Depleted Uranium is ideally suited to reduce both gamma and neutron radiation from the source. The prototype Polyethylene Encapsulated Depleted Uranium Transportation/Disposal cask will allow a one-time transfer of the source into the shielded cask, shipment to Hanford in compliance with DOT standards, and burial without having to remove the source or handle it again. Since it is constructed from recycled materials, the Polyethylene Encapsulated Depleted Uranium cask is inexpensive and can be sacrificed for disposal.
For Information Contact:
Paul Kalb, Division Head
Environmental Research and Technology Division
Brookhaven National Laboratory
The following reference documents are available at the Brookhaven National Laboratory web site.
- J.W. Adams, P.R. Lageraaen, P.D. Kalb, and B.R. Patel, "Polyethylene Encapsulation of Depleted Uranium Trioxide," D.W. Tedder and F.G. Pohland, eds., Plenum Press, 2000.
- Kalb, P.D., J.W. Adams, P.R. Lageraaen, and C. R. Cooley, "DUPoly Process for Treatment of Depleted Uranium and Production of Beneficial End Products" U.S. Patent No. 6,030,549 (February 29, 2000)
- Kaplan, S.A., "Depleted Uranium Market Study," Kapline Enterprises, Inc., Y/NA 1801, August 1995.
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