New Developments in the
Management of Low- and
Intermediate-Level Radioactive Wastes
HAROLD BERNARD, Sanitary Engineer
Division of Reactor Development
U. S. Atomic Energy Commission
Some of the general processes of waste disposal may be well established
in industry. However, the nature of radioactive waste demands that a thorough research and development program be carried out from the laboratory
test tube phase through the micro-pilot and pilot plant phases to finally the
installed operational plant. In a research program the interest is in developing
theory, criteria and operational parameters so engineers, after analyzing
wastes handling and disposal problems, can design a process for treating the
waste which will render it innocuous and permit safe disposal to the environment.
The Atomic Energy Commission in cooperation with many other agencies
and institutions has published a table of concentrations of radioisotopes in
in water and air, (1) which will be safe for public consumption. The concentration values are based on the intake by a person who accumulates this
body burden as a consequence of exposure for a period of 50 years. By definition, then, any effluent containing radionuclide concentrations less than
those stipulated would be considered as being within drinking water standards,
and those in excess of the regulations would require dilution or treatment.
Low level radioactive waste is any effluent which would require a decontamination factor (D. F.) of between 10 and 103; intermediate level waste requires a D. F. between 103 and 105. The chemical quality of low level
waste can be compared to that of tap water with the addition of unwanted
radionuclides, whose physical concentrations can be considered in terms of
micro-trace quantities. For example, consider the maximum permissible
concentration (MPC) of strontium-90 (Sr^O) which is 10"7 uc/ml for continuous exposure. This is a physical concentration of approximately 10-15
gms/ml or one gm per 250 billion gals of water. Intermediate level waste
can be considered as brackish water, high in mineral content, with radionuclides. Examples of the two types are shown in Table I. Both types of
waste require particular, and peculiar, methods of handling.
LIQUID LOW LEVEL WASTE
Low level radioactive liquid waste is normally associated with large
volumes of water. Interest is, therefore, in treatment techniques which have
a large enough capacity to remove the hazardous radionuclides simultaneously
with the more abundant stable chemicals, or in treatment methods which have
a specificity for the more hazardous radionuclides in spite of the presence of
stable constituents.
An example of the former is the chemical treatment plant at Oak Ridge
National Laboratory (Figure 1) which, in essence, is a lime-soda ash water
softening plant; clay is added to scavenge the cesium from the water while
the parent process removes the strontium.   The efficiency is approximately
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