Neutron activation analysis

Neutron Activation Analysis (NAA) is a highly sensitive and accurate technique used in the quantitative and qualitative analysis of material compositions through the measurement of gamma rays emitted from a sample after it has been bombarded with neutrons. This method is particularly useful in various fields such as archaeology, geology, and forensic science, as well as in the environmental, chemical, and medical sciences.

Overview

Neutron Activation Analysis involves exposing a sample to a neutron flux, resulting in the formation of radioactive isotopes. As these isotopes decay, they emit gamma rays, the energy and intensity of which can be measured using a gamma spectrometer. The specific characteristics of the emitted gamma rays allow for the identification and quantification of elements within the sample. NAA can detect concentrations of elements in the parts per million (ppm) or even parts per billion (ppb) range, making it an extremely sensitive analytical tool.

Procedure

The procedure of Neutron Activation Analysis can be divided into several steps:

1. Sample Preparation: The sample is prepared and, if necessary, encapsulated to prevent contamination.
2. Irradiation: The prepared sample is exposed to a flux of neutrons, typically in a nuclear reactor or using a neutron source.
3. Decay: After irradiation, the sample is allowed to "cool," during which time the radioactive isotopes formed during irradiation decay, emitting gamma rays.
4. Measurement: The emitted gamma rays are measured with a gamma-ray spectrometer. The energy and intensity of the peaks in the gamma-ray spectrum are used to identify and quantify the elements in the sample.
5. Analysis: The data obtained from the spectrometer are analyzed to determine the concentration of elements within the sample.

Applications

Neutron Activation Analysis has a wide range of applications due to its non-destructive nature and high sensitivity, including:

• Archaeology: For the analysis of artifacts to determine their composition and provenance.
• Geology: In the analysis of rocks and minerals to understand the Earth's crust.
• Forensic Science: For trace element analysis in criminal investigations.
• Environmental Science: In the monitoring of pollutants and the study of environmental changes.
• Medicine: For the analysis of trace elements in biological samples and the study of diseases related to elemental imbalances.

Advantages and Limitations

Advantages:

• Non-destructive analysis allows for the preservation of samples.
• High sensitivity and specificity for many elements.
• Capable of analyzing a wide range of materials.

Limitations:

• Requires access to a neutron source, which can be expensive and not widely available.
• The analysis can be time-consuming, particularly due to the decay period required for some isotopes.
• Handling of radioactive materials requires strict safety protocols.

See Also

• Gamma Spectrometry
• Radiochemistry
• Trace Element Analysis