Proposal to correct for the effect of background and density in the determination of gamma emitters using sodium iodide detectors

This study develops a modification to the spectra decomposition method for sodium iodide scintillation equipment, including correcting the natural background counts for the activity concentration calculation. A comparison of the results obtained between two sodium iodide detectors of 2 X 2 in and 3 x 3 in versus a hyper-pure germanium detector of 50 % relative efficiency is performed for soil, sediment, and water samples. It is found that background correction significantly improves activity concentration results in higher energy regions. The concentration values determined by the different spectrometric systems for the samples analyzed do not show significant differences, which supports the results obtained with the proposed calculation method. The uncertainty associated with the measurement and detection limits for the NaI (Tl) detectors is higher than those obtained with the GeHp detector due to the operation of the two technologies and the presence of interferences in the regions of interest. The study carried out in this work establishes an analytical milestone. The methodological model proposed makes it possible to quantify, with reliable results, low concentration levels of NORM materials and even 131I using sodium iodide detectors, among other analytical applications of general interest.