POWER May 2010 - 28

Nuclear Power
Project Salt Vault
The primary objective of Project Salt Vault
was to demonstrate the safety and feasibility
of handling and storing HLW solids from
power reactors in salt formations. The engineering
and scientific objectives were to:
■ Demonstrate waste-handling equipment
and techniques required to handle packages
containing HLW solids from the point
of production to the disposal location.
■ Determine the stability of salt formations
under the combined effects of heat and radiation
(approximately 4,000,000 curies
of radioactive material, yielding up to 109
rads).
■ Collect information on creep and plastic
flow of salt that was needed for the design
of an actual disposal facility.
■ Monitor the site for radiolytic chemical
reactions, if such should occur.
The demonstration site selected was the inactive
Lyons, Kansas, mine of the Carey Salt
Co. The 1,020-foot deep salt mine had operated
from 1890 to 1948 and had been kept open for
possible future use. Preparations for the demonstration
began in 1963, and the first radioactive
material was placed in the mine in November
1965. The tests involved the emplacement of
actual irradiated fuel assemblies from the Engineering
Test Reactor (ETR) in Idaho. The
ETR assemblies were chosen because of their
availability on a dependable schedule and their
relatively high radioactivity levels.
Seven sealed canisters containing 14 SNF
assemblies were transported by truck in a
lead-shielded carrier to the site. Those canisters
were lowered into the mine one at a time
through a 19-inch-diameter charging shaft. In
the mine, the canisters entered a lead-shielded
vessel on a trailer pulled by a diesel-powered
tractor called the " waste transporter. " The
hauler delivered the canisters, one at a time, to
an array of lined holes drilled in the floor. The
waste transporter was also used to recover and
transfer the canisters at the end of the tests.
The canisters were placed in a ring-like arrangement
in the floor of the mine (Figure 2).
Electrical heaters-used to compensate for
lower heat release rates of the fuel elements
compared with actual waste -were attached
to the lower liners to raise temperatures in the
central pillar in order to obtain information
on its in-situ structural response to heat.
The program plan called for replacing the
waste every six months to maximize the radiation
dose to the surrounding salt formations.
At the end of each phase, the spent fuel was
retrieved and returned to Idaho.
The results showed that the structural properties
of salt were not significantly altered by
the high radiation levels. Useful information
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was gathered with respect to thermal stresses,
migration of brine-filled cavities, and salt-flow
characteristics as a function of temperature. For
example, the demonstration revealed that inclusions
of moisture, or brine, in the salt beds had
a tendency to migrate up a thermal gradient toward
a heat source placed in the salt. Quantities
of brine were measured as migrating and interacting
with the deposited waste canisters.
All the predictions of thermal and radiation
effects based upon theoretical modeling and
laboratory experiments were confirmed by the
in-situ demonstration. Despite the rather high
radiation levels and high thermal loading, no
measurable radiolytic or excessive structural
effects in the salt were observed. In addition,
operations at Lyons, both at the surface and in
the mine, were carried out without the use of hot
cells (shielded nuclear radiation containment
chambers used to protect workers). Maximum
personnel recorded dose during any quarter was
200 mrem, principally to the hands of a worker.
The results of the Project Salt Vault demonstration
led many in the AEC to believe that
the use of bedded salt was satisfactory for the
disposal of radioactive wastes. The experimental
phase of Project Salt Vault was terminated
in June 1967 when the last canister was
removed from the mine. The Lyons Mine was
then placed on standby on February 1, 1968.
The Beginning of the End
Workers from Project Salt Vault recall that it enjoyed
the support of the local community. Four
factors contributed to this climate of acceptance:
■ The experiment was designed from the
beginning to be reversible; that is, once
it was completed, all the waste would be
completely removed.
■ Consultations were held with local groups
before the project began.
■ Efforts were made by Oak Ridge National
Laboratory personnel to conduct the studies
in full view of Kansans.
■ Once the research started, regular tours
were conducted in which the general public
could visit the mine.
2. Working in a salt mine. In-situ testing
of nuclear wastes was conducted in the
mid-1960s at the Carey salt mine. Source:
Kansas Geological Survey
However, two intervening events forced the
AEC to withdraw from the Lyons site. The first
was a fire in 1969 at the Rocky Flats facility
in Colorado, which produced pits for nuclear
weapons. The accident generated a large volume
of low-level, plutonium-contaminated debris.
Following standard operating procedures,
the managers of Rocky Flats sent the waste to
the National Reactor Test Station in Idaho for
storage. That action outraged Idaho's political
leadership, which saw no reason why their
state should become the " dumping ground "
for waste created in Colorado. They acted and
ultimately extracted a commitment from AEC
Chairman Glenn Seaborg (1961-1971) that all
of the waste would be removed from Idaho by
1980. That pledge necessitated the construction
of a disposal facility. The second factor,
dominating an entire decade, was the growing
opposition to nuclear power punctuated by the
Three Mile Island accident in 1979.
Confronted with the immediate need for a
repository, and given the available information
at the time, the AEC's siting strategy
was to quickly identify a site for storage of
nuclear wastes in a salt dome underlying
about 500,000 square miles in portions of 24
states. Most importantly, bedded salt deposits
were completely free of circulating groundwater
and were isolated from underground
aquifers by impermeable shale. Any fractures
that might develop would be sealed by plastic
deformation and recrystallization of the
salt. The regions considered cut down the site
options because only salt deposits 200 feet
thick and lying within 2,000 feet of the surface
were deemed suitable for the first waste
repository. The largest areas meeting these
criteria lay in central Kansas, although there
were two smaller areas in Michigan and one
in west central New York. In 1970, the AEC
announced that, pending confirmatory tests,
the Lyons site was being selected as the first
full-scale national repository.
The degree to which the AEC had consulted
with state and local officials before this
announcement is in dispute. What is clear is
the AEC's decision did not receive the same
ringing endorsement as the earlier experimental
tests had. Moreover, state and local
political opposition to the Lyons site was intense,
particularly when technical problems
with the site became apparent. The political
arm-twisting had just begun.
Political Opposition Begins
A widely held view among leaders of the Kansas
Geological Survey was that there was insufficient
knowledge about repository design,
the heat-flow models were primitive, and there
were large gaps in the understanding of wasterock
interactions and rock mechanics. These
concerns, among others, were the basis for opPOWER
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POWER May 2010

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