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Waste characterization
Waste characterization (WC) is:
"The determination of the physical, chemical and radiological properties of the waste
to establish the need for further adjustment, treatment, conditioning, or its suitability for
further handling, processing, storage or disposal."
Radiological waste characterization involves detecting the presence of individual
radionuclides and quantifying their inventories in the waste. This can be done by a variety of
techniques, depending on the waste form, radionuclides involved and level of detail/accuracy required.
For example, a simple radiation dose rate measurement will give an indication of the total quantity
of gamma emitting radionuclides in a waste package, but will not identify individual radionuclides
or their concentrations. Gamma spectroscopy will identify the individual radionuclides and, when
properly calibrated, their quantities as well. Other techniques, such as active/passive neutron
interrogation, alpha spectroscopy, and liquid scintillation counting are used for other classes
of radionuclides. The preferred methods are often referred to as "non-destructive" or "non-invasive",
since they do not involve opening a waste package to take samples. The terms most frequently used
are NDA (non-destructive assay), NDE (non-destructive examination) and NDT (non-destructive testing).
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.
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 manufacturer who uses a particular chemical,
then you can determine from your "knowledge of the process" which radionuclide(s) and/or chemicals
are present in your waste.
Physical characterization involves inspection of the waste to determine its physical form, strength,
etc. Inspection of closed waste packages can be done 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 and/or
operator of a waste handling, transportation, storage, processing and/or disposal service. The WAC
usually specify such things as the required physical form of the waste, maximum levels of radioactivity,
packaging requirements, etc. as well as what wastes are excluded from their service.
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