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What Should We Do With Plutonium Once Nuclear Weapons Are Dismantled?
What Should We Do With Plutonium Once Nuclear Weapons Are Dismantled?
International Research Team May Have a 30-Million-Year Answer
ANN ARBOR, Mich.--(BUSINESS WIRE)--Aug. 9, 2000--An international
research team led by the University of Michigan (UM) has discovered a
radiation-resistant material suitable for the immobilization and safe
disposal of plutonium. This highly durable material--a zirconate
pyrochlore--is calculated to resist radiation damage for up to 30
million years.
Gadolinium zirconate, the team discovered, is superior to the
titanate-based ceramic that is currently proposed for plutonium
immobilization in the United States. The research team performed a
systematic study of the radiation resistance of the gadolinium
titanate and zirconate compositions. Results indicate that the
titanate will be completely damaged by the radiation in less than
1,000 years. The zirconate will not sustain damage for periods up to
30 million years. Considering that plutonium is an environmental
contaminant with a radioactive half-life of 24,500 years, the multi-
million-year calculation of the zirconate's durability makes it a
leading candidate for the immobilization of plutonium.
"This is a significant scientific discovery with major environmental
impact for future generations," said Dr. Yok Chen, Program Manager in
the Office of Basic Energy Sciences at the U.S. Department of Energy,
which funded this research at the University of Michigan and Pacific
Northwest National Laboratory (PNNL).
Rodney Ewing, Professor of Nuclear Engineering and Radiological
Sciences at the University of Michigan College of Engineering, and
William Weber, a senior staff scientist at PNNL, led the team of
researchers that included scientists at the Australian Nuclear
Science and Technology Organization and the Indira Gandhi Centre for
Atomic Research in India.
The team's findings were first published in the December 1999 Journal
of Materials Research (JMR). This past week, another international
team of researchers at Los Alamos National Laboratory, working
independently from the UM team, announced similar results with an
erbium zirconate ceramic.
The safe disposal of plutonium is a relatively new environmental
problem. Both the United States and the former Soviet Union have
agreed to dismantle nuclear weapons, resulting in 100 metric tons of
plutonium, approximately 50 from each side. This plutonium is only a
small part of a growing global inventory of plutonium that is already
greater than 1,300 metric tons.
"What to do with this plutonium is a science and policy issue of
great national and international importance," said Ewing. "Two
independent research teams have shown that zironate-based materials
offer an excellent solution to the serious problem of this ever-
increasing amount of plutonium. Taken together, these startling
results confirm that there are radiation-resistant and chemically
durable materials that can safely contain plutonium."
This new material is capable of incorporating a large variety of
chemical elements in its structure, including plutonium. The
zirconate withstands the radiation that results from the decay of
plutonium. The ability to sustain high levels of damage without a
disruption of the atomic structure accounts for the radiation
stability of this material.
"The currently considered titanate became completely disordered at
relatively low exposures to radiation," said Shixin Wang, a UM
postdoctoral fellow and lead author on the JMR article. Wang recently
presented these findings at the Plutonium Futures 2000 conference on
July 10 in Sante Fe, NM.
"The disordered titanate material leads to an increase in the loss of
plutonium when the material is in contact with water," added Weber at
PNNL.
The team will continue to investigate the chemical durability of
gadolinium zirconate by conducting leaching tests. The radiation
behavior of the zirconates with high concentrations of impurities
will be studied to ensure a complete knowledge of the long-term
performance of this material.
Professor Ewing can be reached at (734) 647-8529 or
rodewing@umich.edu to discuss this new material for plutonium
immobilization. William J. Weber, at PNNL, can be reached for comment
at (509) 375-2299 or Bill.Weber@pnl.gov.
CONTACT:
University of Michigan - College of Engineering
Janet C. Harvey-Clark, 734/647-7087
janethc@engin.umich.edu
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