Environmental Engineering Reference
In-Depth Information
The nature of the waste is important in terms of radionuclides present, their half-
life, and mode of decay, since the disposal route selected will often depend on the
presence of several key radionuclides. A radionuclide inventory will provide the
necessary information regarding specific radionuclides present and their activity
levels. At a minimum, this information allows a waste stream to be evaluated in
terms of maximum concentration of each radionuclide, which is available at any
time in the future.
Chemical waste characterization involves the determination of the chemical
components and properties of the waste. This is most often done by chemical analysis
of a waste sample. All radioactive wastes that contain chemicals should be considered
potentially regulated under federal or state regulations until the chemical portion
has been determined to be nonhazardous.
Radiological and chemical waste characterization can also be inferred from
process knowledge. For example, if you are a medical researcher who only uses a
few particular radionuclides under controlled experimental conditions, or a manu-
facturer who uses a particular chemical, then you can determine from your own
knowledge process which radionuclides or chemicals, or their combinations, exist
in your waste. To use and justify process knowledge for characterization of radio-
active waste, you should (1) be able to estimate, as precisely as possible, the
radioactive content of a unit of waste; (2) understand the radioactive decay processes
that may result in daughter isotopes that are not in secular equilibrium; (3) know
whether the chemicals used in the process were hazardous; (4) have a thorough
understanding of how the chemicals were used; (5) understand the chemistry of the
reaction to determine if hazardous chemicals were produced where none existed
before; (6) know whether the process converted unlabeled chemicals to radio-labeled
ones; and (7) be able to report the origin and purity of isotope preparations if such
information is needed by the Waste Management Group.
Physical characterization involves inspection of the waste to determine its phys-
ical form and strength. Closed waste packages can be inspected using a variety of
techniques, such as radiography (x-ray) and sonar.
Waste acceptance criteria (WAC) are the conditions imposed on a waste producer
by the regulator or operator of a waste handling, transportation, storage, processing,
or disposal service. The WAC usually specify such things as the required physical
form of the waste, maximum levels of radioactivity, and packaging requirements as
well as what wastes are excluded from their service. The WAC from radioactive
waste disposal sites require that all waste generators be able to validate the chemical
and radioactive constituents of their waste by referring to pertinent written proce-
dures, logs of activities, and results of analyses conducted in the course of their
experiments.
3.4
CLASSIFICATION AND CHARACTERIZATION OF
MIXED WASTES
Radioactive waste that also contains a “conventional” hazard, such as chemical
toxicity, or material that contains both radioactive material and RCRA hazardous
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