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Applications and Machinery -> Nuclear
Waste |
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-> Copper Containers for Nuclear Waste Disposal
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| Copper Containers for Nuclear Waste Disposal |
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Oxygen-free copper, 7% aluminum bronze, and 70-30
copper nickel alloys are being considered as container materials for
the burial of high-level radioactive waste in the proposed repository
at Yucca Mountain, in the USA.
The concept that spent fuel and other forms of high-level nuclear
waste could be safely isolated in copper containers in a geologic
repository originated in Sweden in 1978 (the KBS-II plan). The Swedish
design was based on using the container as one of a series of barriers
for the release of radionucleides. The expected life of the copper
container was estimated to be 1 million years. However, the entire
containment system would prevent the release to the accessible environment
for a much longer time.
Pure, oxygen-free high-conductivity copper was chosen because it is
thermodynamically stable in pure water. Calculations were made to
project copper canister degradation through general corrosion by groundwater
during the lifetime of the repository. These calculations showed that
even under worst-case conditions, only negligible amounts of copper
would be removed from the canister by general corrosion during the
planned life of the repository. Subsequent calculations of pitting
corrosion predicted no penetration of a thick-walled container in
several hundred thousand to well over a million years.
The National Research Council of the National Academy of Sciences
(USA) accepted the findings of the Swedish KBS-II data, as well as
further work by the researchers (KBS-III) contending that the copper
canister's life could be expected to exceed 1 million years.
In 1984, the USA's Basalt Waste Isolation Project and the Nevada Nuclear
Waste Storage Investigations initiated studies on copper-based materials
as possible containers for nuclear waste.
A 1991 report from the Copper Development Association (USA) titled
"Copper Containers for Nuclear Waste Disposal-A Critical Review of
the Literature on Corrosion in Prospective Repository Environments,"
by D. Peters and K. Kundig, presented at the Waste Management '91
Conference in Tucson, Arizona (USA) concluded that:
- Any oxidation or general corrosion of copper and copper alloy canisters
would occur very slowly and that penetration of the container by these
processes is extremely unlikely;
- Penetration of the canisters by pitting is not likely;
- Native copper can be stable for more than 500 million years in geologic
formations where thermodynamically possible corrosion reactions are
kinetically inhibited; and
- The radiolytic formation of microquantities of ammonia and its effects
on the integrity of copper-based containers, as well as the effects
of tensile stress should be studied further.
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