A study of the extraction of plutonium from planchets by Aridus-ICP-SFMS

Two extraction processes of plutonium (Pu) on planchets from alpha spectrometry (AS) have been evaluated by inductively coupled plasma sector field mass spectrometry with a desolvator system (Aridus-ICP-SFMS). The samples were traced with known concentrations of 239Pu (1.2 × 103 fg) and 242Pu (2 × 103 fg) followed by an electrodeposition in planchets, according to the Hallstadius method. The processes of extraction were carried out with 50 mL of 0.36 mol L-1 HNO3 every 30 min up to 180 min in a glass beaker at 60 deg C. The first process was on a hotplate and the second used an ultrasonic system. Finally, samples were evaporated to dryness, and resuspended in 10 mL of 0.72 mol L-1 HNO3 for evaluation. The results showed that at 120 min, a ∼70 % recovery of 239Pu and a ∼80 % recovery of 242Pu in both processes were obtained. The average recoveries of 239Pu and 242Pu at 180 min using the hotplate in plate were 93.4 ± 4.6 and 93.7 ± 4.2 % respectively, and with the ultrasonic system were 96.0 ± 4.3 and 98.2 ± 1.0 % respectively. In conclusion, both processes are suitable for Pu extraction, and Aridus-ICP-SFMS is an essential technique for the reassessments and quantification of Pu. In addition, procedural blanks spiked with 1 × 102 fg mL-1 U were prepared for each process, in order to study the contribution of the 238U on the background signal at m/z = 239, which was 0.5 ± 0.2 cps, indicating that the contribution of 238U on the 239Pu signal was negligible. Furthermore, this methodology can be applied to sample planchets with environmental, food, biological and nuclear origin, and thereby to avoid repetitive analysis when Pu concentration determined by AS are under minimum detectable activities. (author)