Determination of 232Th, 230Th and 228Th in liquid effluents from uranium mining

A liquid scintillator αlpha spectrometer was built for the determination of Th-228, Th-230 and Th-232 in liquid effluents from Uranium mines and mills. The resolution of the αlpha spectrometer was found to be 200-300 KeV, when the scintillator was 8% T0P0, 0,77% scintimix-4 (91% PP0 and 9% Dimetil-P0P0P) and 10% of naphthalene in toluene. Aliquat-336 in xylene (30% v/v) was used to separate the thorium isotopes from other interfering radionuclides (U-238, U-234, Ra-226, Po-210). Under the extraction experimental conditions, the detection limits were 1,2 pCi/1 for Th-232, 1,2 pCi/1 for Th-230 and 0,9 pCi/1 for Th-228, for 1000 minutes of counting time. (author)