Neutron activation analysis

Neutron Activation Analysis sample loading station

Neutron activation analysis (NAA) is a powerful analytical technique that can be used to simultaneously determine the concentrations of many elements, even at the trace level. Neutrons from ANSTO's OPAL nuclear reactor irradiate a range of environmental, geological and industrial samples. This process results in the samples becoming activated, and they emit gamma radiation. By measuring the energy of the radiation, NAA scientists can determine the presence and concentrations of more than 60 elements.

Advantages of NAA

Neutron activation analysis is recognised as a primary ratio method, is a standard method for the certification of reference materials.

NAA is unsuitable for the analysis of a number elements (significantly lead and many light elements), and better results can be obtained using more common techniques for only a small number of elements. As it is a nuclear technique, NAA only provides elemental concentration, and cannot yield information about the chemical environment (such as bonding, oxidation number or molecular structure).

The NAA facility at ANSTO is unsuitable for large scale, routine analysis of samples. Our focus is on providing a high quality, specialist service to researchers and industries who have requirements that cannot be met by standard laboratory techniques.

The Principle

ANSTO's OPAL reactor produces neutrons through nuclear fissions. When these neutrons irradiate a material, the atomic nuclei absorb some of them, becoming radioactive in the process. This process is known as neutron activation. The activated nuclei undergo radioactive decay, emitting gamma rays as part of this process. The energy of the gamma rays emitted by a nuclide is characteristic of that nuclide. This means that measuring the energy of the emitted radiation allows the presence of specific elements to be determined. The concentration of a particular element is proportional to the intensity of the peak in the gamma spectrum the greater the intensity, the greater the concentration.

Applications

NAA's versatility is one of its greatest strengths, leading to its use in a number of fields. The absence of matrix effects means that NAA can be used to analyse many types of samples, from a range of industries. ANSTO's Neutron Activation Group specialises in the analysis of samples in the following fields:

• Environmental science: analysis of soils and marine sediments
• Geology and Mining: mineral characterisation, analysis of coal
• Archaeology: artefacts, pottery and pigments
• Metrology: the certification of standard reference materials

NAA is by no means limited to these fields, and analysis of other samples is possible. Contact the Neutron Activation Group to discuss whether NAA is suitable for your project.

Contact

For all enquiries regarding neutron activation analysis, please contact the leader of the Neutron Activation Group, John Bennett:

John Bennett

Telephone: +61 2 9717 3743

Email: john.bennett@ansto.gov.au