Dose inspection and risk assessment on radiation safety for the use of non-medical X-ray machines in Taiwan

The subject of this study is the on-site visits and inspections of facilities commissioned by the Atomic Energy Council (AEC) in Taiwan. This research was conducted to evaluate the possible dose and dose rate of cabinet-type X-ray equipment with nominal voltages of 30-150 kV and open-beam (portable or handheld) equipment, taking both normal operation and possibly abnormal operation conditions into account. Doses and dose rates were measured using a plastic scintillation survey meter and an electronic personal dosimeter. In total, 401 X-ray machines were inspected, including 139 units with nominal voltages of 30-50 kV X-ray equipment, 140 units with nominal voltages of 50-150 kV, and 122 open-beam (portable or handheld) X-ray equipment. The investigated doses for radiation workers and non-radiation workers operating cabinet-type X-ray equipment under normal safety conditions were all at the background dose level. Several investigated dose rates at the position of 10 cm away from the surface of open-beam (portable or handheld) X-ray equipment were very high, such X-ray machines are used by aeronautical police for the detection of suspected explosives, radiation workers are far away (at least 10 m away) from the X-ray machine during its operation. The doses per operation in X-ray equipment with a 30-50 kV nominal voltage were less than 1 mSv in all cases of abnormal use. Some doses were higher than 1 mSv per operation for X-ray equipment of 50-150 kV nominal voltage X-ray. The maximum dose rates at the beam exit have a very wide range, mostly less than 100 μSv/s and the largest value is about 3.92 mSv/s for open-beam (portable or handheld) X-ray devices. The risk induced by operating X-ray devices with nominal voltages of 30-50 kV is extremely low. The 11.5 mSv dose due to one operation at nominal voltage of 50-150 kV X-ray device is equivalent to the exposure of taking 575 chest X-rays. In the abnormal use of open-beam (portable or handheld) X-ray equipment, the effective dose of 3.92 mSv/s is equivalent to taking 196 chest radiographs within 1 s. This work assessed the annual doses (equivalent and effective doses) and risks of X-ray operator staff as reasonably as possible. The results of this research are helpful to the AEC (competent authority of ionization radiation) to improve the management and perform the safe control of X-ray equipment.