Development of emergency radio-bioassay method for Th, Pu, Np and U in urine samples using single-column...

Demand is growing for the development of rapid determination methods for actinides in biological samples for radiological emergency preparedness. A rapid radio-bioassay for ²³²Th, ²³⁹Pu, ²⁴⁰Pu, ²³⁷Np, ²³⁴U, ²³⁵U and ²³⁸U in a 20 mL of urine sample was developed using a single-column extraction chromatography, an automated operation system and ICP-MS/MS. The urine sample with known amounts of tracers was loaded onto the TK200 resin for sequential chemical separation of Th, Pu, Np and U. The chemical yield of Pu, Np, Th, and U consistently exceeded 90% in all samples, while incorporations of other nuclides in each fraction were less than 1%. The ratio of chemical yield for Np/Pu in urine samples (n = 16) was 1.006 ± 0.037 in average. The detection limits (L_D) determined using blank samples for ²³²Th, ²³⁹Pu, ²⁴⁰Pu, ²³⁷Np, ²³⁴U, ²³⁵U and ²³⁸U were 0.168 mBq/L (41.4 ng/L), 0.250 mBq/L (0.109 pg/L), 0.934 mBq/L (0.111 pg/L), 0.0027 mBq/L (0.104 pg/L), 10.0 mBq/L (43.5 pg/L), 0.028 mBq/L (0.350 ng/L) and 0.984 mBq/L (79.2 ng/L), respectively. The method provided adequate decontamination factors for Pt, Hg, Tl, Pb, and Bi, enabling accurate Pu measurement by ICP-MS. The effective doses calculated using the detection limit and the dose coefficients recommended by the International Commission on Radiological Protection (ICRP) were sufficiently lower than 100 mSv which is the criterion of the requirement for protective measures in case of nuclear emergency. The entire analysis for those 7 isotopes in 64 urine samples can be completed within 24 h using this method.