关键词: 放射源, 辐射场, 周围剂量当量率, 意外受照, 防控策略

Abstract: Objective To explore the radiation field dose level and distribution of the radioactive source in the storage state and exposure state,provide experimental basis for dose estimating and control strategy formulating related to the accidental exposure from radiation field of radioactive source. Methods A ²⁴¹Am-Be neutron source with 592 GBq radioactivity and a ¹³⁷Cs radioactive source with 66.6 GBq radioactivity were selected in 2022. The LB123 neutron ambient dose equivalent rate meter and AT1121 X/γ dose rate meter were used to measure the ambient dose equivalent rate around the source containers with the sources stored,and the thermoluminescence dosimeters were used to measure and calculate the ambient dose equivalent rate of the radiation field in the operating place of radioactive source exposure. Results When the radioactive source was in storage state,the highest dose rate at 5 cm on the surface of the source containers of 592 GBq ²⁴¹Am-Be and 66.6 GBq ¹³⁷Cs radioactive source were 500 and 773 μSv/h,respectively. While the radioactive source was exposed,at a distance of 200 cm from the source in the radiation field,the neutron ambient dose equivalent rate generated by the ²⁴¹Am-Be neutron source was 233.5-337.2 μSv/h,with an average value of 299.7 μSv/h,and the ambient dose equivalent rate of ¹³⁷Cs radioactive source was 1.282-1.868 mSv/h,with an average value of 1.530 mSv/h.In the radiation field,the accidental cumulative exposure at a distance of 50 cm from the source for 10 min,the doses of the ²⁴¹Am-Be neutron source and the ¹³⁷Cs radioactive source to the human body were 0.15 mSv and 2.23 mSv,respectively. Conclusion The appropriate source containers should be chosen for different types of radioactive sources according to their ionizing radiation characteristics to achieve reliable shielding effect,and the accidental exposure accident of radioactive sources should be reduced and avoided from the aspects of personal radiation emergency awareness,equipment of alarm devices and innovative radioactive source operating techniques.

Key words: Radioactive source, Radiation field, Ambient dose equivalent rate, Accidental exposure, Control strategy