Methodology development for Gamma-spectrum analysis

Resumo

Nuclear Measurement Laboratory (LMN) is one of the Argonauta’s facilities where the methodology to be developed will use certified and screened samples from the PNI program that consists of radioactive materials cocktails. Moreover, original samples and diluted ones in nitric acid will be measured and compared. As PNI is a program aimed at environmental samples, such cocktails have an activity concentration of less than 37 Bq/l, increasing the need for the developed methodology and good statistical treatment accuracy. This low concentration is near the minimum detection limit of the system used, forcing the laboratories to create solid methodologies that minimize errors and reproducible results. The LMN detection system available to run this work comprises a high resolution spectrometer, a semiconductor detector of hyperpure germanium (HPGe), with a relative efficiency of 20 % and model GEMF5930 from ORTEC (Figure 1). This work presents the selected parameters for a methodology development to validate the gamma‑spectrum analyses performed in the HPGe system of LMN.

A cylindrical geometry with volumes ranging from 100 ml to 500 ml will be used in the counting process. Also, the counting time will vary from 1h to 24h. Besides, the best geometry will be combined with the best counting time to provide results consistent with the required quality. Statistics tests will be applied to the obtained results to evaluate methods reliability. Also, diluted samples measurement will be performed to track possible problems in the dilution process besides evaluating the effect of this dilution on the results reliability.