NAA (Neutron Activation Analysis)
Definition
A nuclear analytical technique in which sample irradiation in a research reactor converts stable isotopes to radioactive ones, which are identified by gamma-ray spectroscopy. Provides sub-nanogram detection limits; used in forensic GSR research and very high-priority casework with reactor access (e.g. BARC Mumbai).
- Type
- Nuclear analytical technique
- Mechanism
- Reactor irradiation converts stable isotopes to radioactive ones
- Detection
- Gamma-ray spectroscopy
- Sensitivity
- Sub-nanogram detection limits
- Access constraint
- Requires a research reactor, e.g. BARC Mumbai
Common questions
Why has NAA largely been replaced by SEM-EDS for routine GSR casework?+
NAA needs access to a research reactor and produces radioactive samples that require handling and cool-down time, making it slow and expensive for routine casework compared to SEM-EDS, which can be run on a standard laboratory bench and gives particle morphology alongside elemental data. NAA now serves mainly high-priority cases or research where its extreme sensitivity is worth the cost.
What can NAA detect that bench-top elemental methods often cannot?+
Because it measures characteristic gamma emissions from activated isotopes rather than surface elemental signals, NAA can reach sub-nanogram sensitivity for trace elements, useful for confirming very low levels of gunshot residue components or distinguishing evidence with minimal material. This sensitivity comes at the cost of reactor access and turnaround time.
Is NAA destructive to the sample?+
NAA is generally considered non-destructive to the bulk sample since irradiation does not physically alter the sample's shape or most of its chemistry, though the sample becomes radioactive and must be stored until it decays to safe levels before further handling or return.
Related terms
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