Determination of radioactivity of P-32 in the human urine by liquid scintillation method applied in internal radiation dosimetry

The determination of P-32 and I-131 radioactivity in the human urine by the liquid scintillation counting (LSC) was first studied and applied in the field of internal radiation dosimetry at the Nuclear Research Institute. After urine samples were preliminarily processed with formaldehyde, we applied the phosphor separation procedure by the precipitation with ammonium phosphor molybdate (NH4)3[PMo12O40]. The chemical separation efficiency of 91% was obtained. The radioisotope of I-131 was extracted with CCl4 and its chemical separation efficiency of 86% was obtained. Iodine was enriched three times through the extraction. Then the processed samples were measured by using the efficiency tracing method with unquenched standards of C-14 and the liquid scintillation counting system of ALOKA-LSC-6100. Based on the counting efficiency of liquid scintillation in combination with the enrichment process of samples of interest, we have experimentally determined the method sensitivity of P-32 and I-131 in the urine samples. The detection limit determined 69.5 pCi/litre for P-32 and 516.2 pCi/litre in case of I-131. From the sensitivity obtained for P-32 and I-131 we determined the one-day intake of the P-32, I-131 through respiratory system 74.0 Bq and 95.0 Bq for P-32 and I-131 corresponding. Based on the specialized internal radiation dosimetry software of MONDAL, the effective dose was calculated 0.1 μSv for P-32 and 1.0 μSv for I-131. The determination of P-32 and I-131 in urine samples by liquid scintillation counting (LSC) is used to calculate the internal dose for workers producing P-32 and I-131, and patients using P-32 and I-131. The results obtained by LSC were compared with other methods being used currently. (author)