**1. Principles**

Neutron activation analysis is a physical technique that is based on nuclear reactions. The sample becomes radioactive when neutrons react with the nuclei of the elements' atoms. Radionuclides are formed and subsequently decay by emitting gamma rays that are unique in half-life and energy. Gamma-ray intensity is proportional to the element content in the sample. Instrumental neutron activation analysis (INAA) and k<sup>0</sup> -INAA are the most sensitive analytical techniques used for the quantitative multielement analysis of major, minor, and trace elements in samples from almost every conceivable field of scientific or technical interest [1–9].
