Obtain element "standards," which are samples with known concentrations of the elements whose concentrations you want to measure. You will be quantifying gamma ray emissions of your standards and comparing them to gamma ray emissions of the sample you want to study, in order to figure out element concentrations in your unknown sample. In this way, you will be able to use neutron activation to analyze concentrations of most elements, with a few exceptions that do not respond to neutron activation: boron, carbon, oxygen and aluminum.
Place both your unknown sample, of which you are measuring concentrations, and your standard sample, of which you already know the concentrations, a few inches from a nuclear reactor with uranium fission. Switch on the nuclear reactor to bombard the sample with neutrons.
Use a high-resolution gamma ray spectrometer to detect the "delayed" gamma rays from the sample.
Calculate the concentration of the sample from the spectrometer data. This concentration is a product of the standard concentration, the ratio of the standard weight to the sample weight, and the ratio of sample activity to standard activity.