Quantitative Analysis Using NAA

Assume that the sample has been activated and the measurements have to be done on this sample at t = 0. Since the induced activity is primarily the product of number of atoms ( mass) of the element of interest, neutron capture cross-section and the neutron flux, this has to be corrected by multiplying with the fraction of the target isotope in the sample and saturation factor (determined by the half-life of the isotope formed and the time of irradiation). The induced activity of the sample will thus be given by 

The activity of the sample after a cooling or delay period (tj) from the end of the irradiation that lasted for time tj is given by 

Accounting for the number of radioactive nuclei that decay during coimting interval the activity will be given as 

---