Nuclear Waste Management
Dr. Donggao Zhao
I worked on two DOE-funded projects (Prof. Rod C. Ewing) related to nuclear
waste management. One project is radionuclide immobilization in the phases
formed by corrosion of spent nuclear fuel. The UO
2 in spent nuclear
fuel is not stable under oxidizing conditions. Under oxic conditions, the U(IV)
has a strong tendency to exist as U(VI) in the uranyl molecule, UO
22+.
The uranyl ions react with a wide variety of inorganic and organic anions to
form complexes that are often highly soluble. The result is rather rapid
dissolution of UO
2 and the formation of a wide variety of uranyl
oxide hydrates, uranyl silicates and uranyl phosphates. The reaction rates for
this transformation are rapid, essentially instantaneous on geologic time
scales. Previous investigations have established that natural uraninites and
their alteration products can be used as natural analogues to study the
corrosion of UO
2 in spent nuclear fuel. A paper on the long-term
corrosion products of natural uraninite UO
2+x under oxidizing
conditions and the fate of the trace elements has been submitted.
A second project of nuclear waste management is borosilicate glass as a waste
form for the disposal of high-level nuclear waste. The objective of my research
effort is to understand the distributions and solubilities of radionuclides and
neutron absorbers in glass waste forms. The results will provide the knowledge
for developing, evaluating, selecting, and matching waste forms for the safe
disposal of various wastes associated with Pu, miscellaneous spent nuclear fuels
(SNF), and other transuranic (TRU) wastes and for developing deterministic model
for the long-term performance assessment of radionuclide containment. One
manuscript from this project has also been submitted for publication.
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