Varijacije pri određivanju specifičnih aktivnosti u uzorcima zemljišta za različite geometrije i HPGe detektore

Abstract

Gamaspektrometrija je jedna od najčešće korišćenih metoda za kvalitativno i kvantitativno određivanje sadržaja radionuklida u zemljištu i drugim uzorcima iz životne sredine. Meren je 31 uzorak zemljišta sa teritorije opštine Aleksandrovac, pri čemu su za svaki uzorak korišćene dve različite geometrije (cilindrična kutijica i marineli posuda). Određene su specifične aktivnosti radioizotopa uranovog i torijumovog niza, kao i 235U, 40K i 137Cs. Uzorci zemlje u geometriji cilindrične kutijice mereni sa na dva HPGe detektora različitih efikasnosti i karakteristika, dok su uzorci u marineli posudi mereni samo na jednom HPGe detektoru. U radu su prikazani rezultati poređenja specifičnih aktivnosti istih radionuklida dobijenih merenjem uzoraka u različitim geometrijama na istom HPGe detektoru kao i uzoraka u geometriji cilindrične kutijice merenih na različitim detektorima. Analizirani su uzroci nastalih varijacija.

Gamma ray spectrometry is an analytical method that allows the identification and quantification of gamma emitting radioisotopes in soil and other environmental samples. 31 samples of soil were collected from different location in the territory of Aleksandrovac municipality. All soil samples were dried, milled and sealed in two different geometries (500 ml Marinelli beaker and 125 ml cylindrical boxes) and stored for six weeks in order to reach radioactive equilibrium between 226Ra and its descendants. All samples stored in cylindrical boxes were measured by means of two coaxial semiconductor HPGe detectors with different characteristics, while samples stored in Marinelli beakers were measured only by means of one coaxial semiconductor HPGe detector. The activity concentrations of radionuclides 40K, 137Cs, 235U, 226Ra, 238U and 228Ac in all soil samples were determined. Variations in specific activities determination for different geometries measured using one of the detectors, as well as for cylindrical box geometry measured using both detectors, are presented in this paper. The causes of these variations are analyzed.