Radioactive Waste Classification and Characterization
Classification schemes
Waste is classified by activity concentration, half-life, heat output and disposal route. Common categories: exempt/clearance, very short-lived (decay storage), very low level, low level, intermediate level and high level. High-level waste is defined by heat generation or by origin (spent fuel reprocessing). Long-lived waste is separated because it constrains disposal options.
Characterization
Characterization establishes radionuclide inventory, chemical and physical form, and hazardous properties. It draws on process knowledge, historical records, dose-rate and gamma spectroscopy measurements, scaling factors and destructive analysis. Know the difference between non-destructive assay (gamma spectrometry, neutron counting) and destructive analysis (radiochemistry).
Traps
- Classifying by origin alone when the disposal route depends on activity concentration.
- Ignoring non-radiological hazards (chemotoxic, reactive, pressurised) that also drive acceptance.
- Confusing total activity with activity concentration.
- Forgetting that scaling factors must be validated for the specific waste stream.
Rule of thumb
Waste acceptance criteria at the disposal facility, not the generator's label, determine whether a package can be disposed of. Always check the receiving facility's criteria.
Worked example
A drum has a measured Cs-137 activity of 4 GBq in a 200 L drum. Activity concentration is 4 GBq / 0.2 m3 = 20 GBq/m3. Compare that with the facility's limit for the relevant category before deciding the disposal route.