Neutron Activation Analysis (NAA) is a highly sensitive method for the accurate determination of elemental concentrations in a material.  Sensitivities are sufficient to measure certain elements at the nanogram level and below.

The NAA method is based on the detection and measurement of characteristic gamma rays emitted from radioactive isotopes produced in the sample upon irradiation with neutrons.  Samples with unknown elemental concentrations are irradiated with thermal neutrons in a nuclear reactor together with standard materials of known elemental concentrations.  Neutrons are absorbed in the nuclei of constituent atoms, and later these nuclei emit radiation with energy and quantity characteristic of the particular element.  This emitted radiation is a 'fingerprint' of the element, and the amount of radiation given off at a certain energy is indicative of the amount of the element present in the sample.  A comparison between specific activities induced in the standards and unknowns provides the basis for computation of elemental abundances.  From this analysis, a report is issued giving elemental concentrations in the unknown sample.

In this diagram of the NAA process, a nucleus absorbs a neutron from the top left.  The nucleus becomes excited and immediately releases a gamma ray and decays to a lower energy level, although it still is in an excited state.  Then after a period of time (dependent on the nucleus) the excited nucleus emits a beta particle and a gamma ray, at which time the gamma ray is detected by a detector (not shown).  Analysis of the spectrum of gamma rays emitted allows determination of the elemental composition of the sample.

How NAA is performed

Applications of NAA

Advantages of NAA over other chemical analyses

Elements detected here at the UWNR

Contacting us to perform NAA

Other uses of the Neutron Field here at the reactor

Last Modified: 9/5/2007