RESUMEN
Objective To establish a method for measurement of 239Pu in fecal samples based on inductively coupled plasma-mass spectrometry (ICP-MS), and to provide a novel method for assessing the internal exposure of workers. Methods Fecal samples were collected from workers and labeled. The samples were pretreated with carbonization ashing and microwave digestion devices, purified on TEVA resin, and measured using ICP-MS. Results The detection limit of 239Pu in fecal samples based on ICP-MS was 1.91 × 10−4 Bq. Conclusion In the routine monitoring of class S substances characterized by a 5 μm aerodynamic diameter during 12 months, the committed effective dose corresponding to the detection limit is 0.17 mSv. This value meets the requirements of relevant national standards and ICP-MS can be used as a novel means for accurate evaluation of internal exposure for workers.
RESUMEN
The isotopic fingerprints of plutonium are extremely important for nuclear safeguards and nuclear forensics. An analytical method was developed for direct determination of 240 Pu / 239 Pu ratio in plutonium-containing particles by laser ablation multiple collector inductively coupled plasma mass spectrometry ( LA-MC-ICP-MS). The risk of ablated particles leakage was reduced by leak detection, exhaust hood, and swiping the laser cell. Scanning mobility particle sizer (SMPS) was used to measure the effect of ablation parameters on the size distribution of ablated particles. The results showed that the majority of ablation material presented as particles from 40 -500 nm and the sweep time after laser ablation should be longer than 15 min. The particle size was evaluated to guide LA-MC-ICP-MS system. By using external normalization method for correction of the mass fractionation correction factor and ion counter efficiencies measured by nebulizer-coupled MC-ICP-MS, a LA-MC-ICP-MS method was established for analysis of 239 Pu / 240 Pu ratio in plutonium particles. Spot size, ablation rate and laser dwell time were set at 30 μm, 5 Hz and 5 s, respectively. Laser energy density was controlled to ensure that the intensities of 239 Pu for plutonium-containing particles were about 2×104 cps and 2×105 cps, respectively. The analytical results showed that the relative uncertainties for 239 Pu / 240 Pu was less than 1. 4% ( n = 6), and the measured value deviated by less than 4. 7% from the reference value. The time for adjusting system and determining 239 Pu / 240 Pu ratio in single plutonium particle was 9 h and 0. 5 h, respectively. The results demonstrated that this technique was rapid, precise and accurate, and could be used for determination of 239 Pu / 240 Pu in plutonium-containing particles.