POWER May 2010 - 26

Nuclear Power
ANALYTICAL INSTRUMENTS
Measurement of Degassed
Cation Conductivity -
AMI Deltacon DG
In 1955, the National Academy of Sciences (NAS) began formulating
the scientific basis for establishing a U.S. nuclear waste management
program. The NAS, National Research Council, and Earth
Sciences Committee on Waste Disposal appointed an eight-man
committee, at the request of the AEC. The eight-member committee
consisted of prominent geologists and geophysicists whose mission
was to consider the possibilities for disposal of HLW in geologic
formations within the U.S. Note the extreme difference in the technical
qualifications of the study committee members now and 55
years ago.
� Automatic and continuous measurement
of total, cation and degassed
cation conductivity.
� Re-boiler according to Larson-Lane
(ASTM D4519-94).
� Tightly controlled degassing
temperature.
� Calculation of sample pH and
ammonia concentration.
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26
The state of the technology in 1955 was to dissolve nuclear wastes
in liquid until they reached relatively low concentrations prior to
storage. This approach to storing nuclear waste was obviously favored
by the committee, as evidenced by several discarded options.
For example, the use of granite and other crystalline rock quarries,
including permeable noncrystalline rocks, such as sandstone and
limestone, was discounted because of the near impossibility of sealing
a facility against leaks. The uncertainties surrounding sealing
nonpermeable materials such as clay and shales seemed too formidable.
Other options, such as injecting the waste into deep-lying
porous media, inter-stratified with impermeable beds, were feasible
in principle but deemed impractical to put into operation because of
concerns with filter media clogging.
The committee believed the most promising repositories were
medium-stable salt formations. The prevailing view was that abandoned
salt mines or cavities especially mined to hold waste are, in
essence, long-lasting tanks. Two primary factors made salt the appropriate
answer. First, a relatively stable salt formation is essentially
impermeable to water and other fluids that could leak waste. Second,
fractures in the salt would be self-sealing because of the plastic flow
properties of the material at typical repository depths. The committee
also backed salt for these additional reasons: the wide distribution
and large reserves of salt formations, salt's structural properties
(it has the structural strength of concrete), the relatively low cost of
developing space in salt, thermal conductivity (salt has a high thermal
conductivity compared with most geologic materials), and the
location of salt deposits in areas of low seismicity.
The NAS committee believed it had determined the types of acceptable
geologic formations that would be capable of isolating and
storing radioactive waste for thousands of years. Furthermore, the
committee's position was based on the assumptions that neither the
chemical nor physical properties of the waste nor the salt would be altered
when exposed to the heat and radiation generated by the waste.
If these assumptions were validated, then all that was necessary was
to find a suitable salt formation to dispose of the waste. The committee
would eventually publish its findings in the September 1957
report, " The Disposal of Radioactive Waste on Land, " which heavily
influenced waste management policy over the next two decades. The
report is available from Google Books (http://books.google.com).
Over the next four years (ca. 1957 to 1962), small-scale research
projects were initiated to test the validity of the committee's assumptions.
Also in 1962, the U.S. Geological Survey evaluated the suitability
of more than 200 salt domes throughout Texas, Louisiana, and
Mississippi, thereby initiating the process for conducting siting studies
for nuclear waste disposal. Concurrently, substantial improvements
in fuel reprocessing technology were being made, the most
important being a 20-fold reduction in liquid waste volumes. These
advances facilitated transforming the remaining aqueous waste into
a solid form but substantially increased the heat and radiation levels
of the final waste form. This breakthrough redirected the AEC to examine
the effects of packaged radioactive wastes in salt by performing
the first major in-situ test to obtain the data needed to design a
waste repository. This experiment was called Project Salt Vault.
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POWER | May 2010
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POWER May 2010

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