In diploma work it is proven that activity of 232Th can be correctly estimated by gamma spectrometry from mesuring activity of it's doughter products. The conclusion was made based on comparable activity obtained while measuring 228Ac and 212Pb with gamma spectrometry and activity of 232Th with alpha spectrometry. The radioactivity of samples with different fraction sizes from Hackman canyon was analyzed. The activity decreasing with increasing fraction size was found. We used eight different fraction sizes ranging from below 0.05 mm to 10 mm. There is also included information about thorium separation from environmental sample using method TEVA Resin and efficiency mesurement of gamma spectrometer. V diplomskem delu smo uspeli dokazati, da se lahko aktivnost 232Th korektno določi z uporabo gama-spektrometra pri čemer se meri aktivnost njegovih hčerinskih radionuklidov. Sklep je bil narejen na podlagi meritev aktivnosti 228Ac in 212Pb z gama-spektrometrom in aktivnosti 232Th z alfa-spektrometrom, kjer smo prišli do primerljivih podatkov. Izvedena je bila analiza vzorcev različnih frakcij iz Hackmanove doline. Ugotovili smo, da aktivnost vzorcev pada z naraščanjem velikosti frakcije. Uporabili smo 8 različnih frakcij velikosti med 0,05 mm in 10 mm. V delu so vključene tudi informacije o separaciji torija iz naravnih vzorcev z uporabo metode TEVA Rasin in merjenju učinkovitosti gama-spektrometra.
