Investigation and analysis of radiation level and personnel exposure dose of X-ray baggage inspection systems in metro line 6 of a certain economic zone

Objective To investigate the radiation protection status of X-ray baggage inspection systems on metro line 6 in a certain economic zone, analyze the effective dose levels received by staff and the public, and provide a scientific basis for radiation protection management in rail transit.

Methods Field measurement was adopted in this study. On May 28, 2024, systematic measurements were carried out on 42 X-ray baggage inspection systems on metro line 6 in a certain economic zone, encompassing a total of 588 monitoring points. The air kerma rate at each monitoring point was measured under normal operating conditions. Combined with actual operational data (e.g., annual passenger flow of 17 million passengers, working schedule of staff, and daily inspection volume), the annual effective doses of occupational and public exposure were estimated. One-way ANOVA was used to compare radiation levels among different monitoring points, and independent samples t-test was adopted for comparison between different stations.

Results The air kerma rates at 588 monitoring points of 42 X-ray baggage inspection systems from 21 stations on metro line 6 in a certain economic zone ranged from 0.09 μGy/h to 1.35 μGy/h, with an average radiation level of (0.45±0.29) μGy/h, which was far below the national standard limit of 5 μGy/h. Statistically significant difference in radiation levels was observed across different monitoring points (F=43.56, P<0.01). The highest radiation level was found at baggage inlets (0.75±0.23) μGy/h, and the lowest was detected at operator positions ((0.10±0.01) μGy/h). The radiation level at the baggage entrance of the station with the highest radiation (Station AA) was 1.35 μGy/h, whereas that of the station with the lowest radiation (Station DD) was 0.56 μGy/h; the difference between the two stations was statistically significant (t=8.32, P<0.01). Estimation based on operational data showed that the annual effective dose of staff was 0.12 mSv (0.6% of the occupational exposure dose limit), and the annual effective dose of the public was 0.001 mSv (0.1% of the public exposure dose limit).

Conclusions The radiation protection measures of X-ray baggage inspection systems on metro line 6 in a certain economic zone are effective, and the radiation doses received by staff and the public remain within safe limits. The current standard limit has a sufficient safety margin.