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.

Objective To investigate the natural penetrating radiation levels along the Qinghai-Tibet Railway, and to preliminarily evaluate the doses received by the railway employees and passengers. Methods Natural penetrating radiation was measured at 15 typical locations with different altitudes along the railway and in the carriages of a train from Lhasa to Xining using high-pressure ionization chamber RSS131, sodium iodide radiation dose rate meter MARS1561, and neutron ambient dose equivalent rate meter LB6411. Results The levels of terrestrial gamma radiation, cosmic ray ionization components, and neutron radiation were 21.5-246.6 nGy/h, 79.8-225.5 nGy/h, and 24.5-101 nSv/h, respectively. The effective dose of natural penetrating radiation received by passengers and crew on a train from Lhasa to Xining was 4.82 μSv. Conclusion Comparison with the empirical formula and verification of method reliability confirm the accuracy of the measurement. Our results provide a primary understanding of the radiation levels along the Qinghai-Tibet Railway and the radiation doses received by passengers, which can be used as a basis for the regulatory authorities.