放射源倒装场所辐射场剂量分布的实验研究

Experimental research on dose distribution of radiation field in operating place of radioactive source

目的探究放射源在贮存状态和倒装裸露状态时辐射场剂量水平及其分布,为放射源倒装场所人员在辐射场中意外受照剂量估算及其防控策略提供实验依据。方法于2022年选用592 GBq^(241)Am-Be和66.6 GBq^(137)Cs放射源各1枚,使用LB123型中子周围剂量当量率仪和AT1121型X/γ剂量率仪测量贮源状态时源容器外围周围剂量当量率,使用热释光剂量计测量并计算放射源裸露状态下操作间内辐射场的周围剂量当量率。结果放射源处于贮存状态时,592 GBq^(241)Am-Be和66.6 GBq^(137)Cs放射源源容器表面5 cm处最高剂量率分别为500和773μSv/h。放射源倒装处于裸露状态下,在辐射场中距源200 cm处,^(241)Am-Be中子源引起的中子周围剂量当量率为233.5~337.2μSv/h,平均值为299.7μSv/h,^(137)Cs放射源的周围剂量当量率为1.282~1.868 mSv/h,平均值为1.530 mSv/h;辐射场中距源50 cm处累积受照10 min,^(241)Am-Be中子源和^(137)Cs放射源对人体可能产生的剂量分别是0.15和2.23 mSv。结论不同类型的放射源应根据其电离辐射特性选择合适的源容器以达到可靠的屏蔽效果,并应从个人辐射应急意识的提升、报警装置的配备和放射源操作技术的创新等方面制订防控策略,以减少和避免放射源倒装操作的意外照射事故。

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 ^(241)Am-Be neutron source with 592 GBq radioactivity and a ^(137)Cs radioactive source with 66.6 GBq radioactivity were selected in 2022.The LB123 neutron ambient dose equivalent rate meter and AT1121 X/γdose 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 ^(241)Am-Be and 66.6 GBq ^(137)Cs radioactive source were 500 and 773μSv/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 ^(241)Am-Be neutron source was 233.5-337.2μSv/h,with an average value of 299.7μSv/h,and the ambient dose equivalent rate of ^(137)Cs 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 ^(241)Am-Be neutron source and the ^(137)Cs 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.