Objective To investigate the radiation protection status of X-ray baggage inspection systems in Metro Line 6 of a Certain Economic Zone, evaluate the radiation dose levels of staff and public, and provide scientific basis for radiation protection management of rail transit systems.

Methods A systematic survey was conducted on 42 X-ray baggage inspection systems at 21 stations along the entire line, with a total of 588 monitoring points. Air kerma rates at different positions were measured using a calibration factor-corrected radiation detector under normal operating conditions. Combined with actual operational data (annual passenger volume of 17 million, security staff work schedules, and daily inspection volumes), occupational and public exposure doses were estimated.

Results The air kerma rates at monitoring points ranged from 0.09 to 1.35 μGy/h, with a mean of (0.45±0.29) μGy/h, which was significantly lower than the national standard limit of 5 μGy/h. Radiation levels at different positions showed significant differences (F=43.56, P<0.01), with the highest levels at baggage entrances (0.75±0.23) μGy/h and the lowest at operator positions (0.10±0.01) μGy/h. Radiation levels varied among different stations, with the highest station (AA Station) measuring 1.35 μGy/h at the entrance and the lowest station (DD Station) measuring 0.56 μGy/h (t=8.32, P<0.01). Based on actual operational data, the estimated annual effective dose for staff was 0.12 mSv (0.6% of the occupational dose limit) and for the public was 0.001 mSv (0.1% of the public dose limit).

Conclusions The radiation protection measures for X-ray baggage inspection systems in Metro Line 6 are effective, and the radiation doses for staff and public are safely controlled. The current standard limit provides adequate safety margin. Variations in radiation levels among different stations may be related to equipment maintenance status and usage time. It is recommended to strengthen routine monitoring and maintenance management.