^(225)Ac使用过程中的辐射防护

Radiation protection during use of ^(225)Ac

测量和计算了^(225)Ac及其子体平衡体系的剂量当量率,计算了相同活度的131I和99mTc的剂量当量率。根据测量数据推导了^(225)Ac及其子体平衡体系的铅十值层、半值层厚度。结果表明:85.5 MBq的^(225)Ac源在未屏蔽情况下,距其0.5 m处剂量当量率是标准规定的人员操作位的剂量当量率限值2.5μSv/h的4.56倍。距^(225)Ac源0.5 m处的剂量当量率的实测值与理论值符合性比0.15 m处的更好,特别是0 mm、5 mm、10 mm、15 mm和20 mm铅屏蔽情况下;相同活度的131I和99mTc,实测的^(225)Ac及其子体平衡体系的剂量率约为131I理论值的一半,约为99mTc的1.5倍;核医学^(225)Ac实践活动中,应重视外照射防护,辐射屏蔽计算时可将20 mm、5 mm分别作为放射性平衡条件下的^(225)Ac及其子体的铅十值层和半值层厚度。

The dose equivalent rate of ^(225)Ac and its daughter equilibrium system were measured and calculated.In addition,the dose equivalent rates of 131I and 99mTc with the same activity were also calculated.The tenth-and halfvalue thicknesses of lead for ^(225)Ac were derived based on measurement data.The results show that dose equivalent rate at 0.5 m,for unshielded 85.5 MBq ^(225)Ac,is 4.56 times higher than dose equivalent rate maximum limit 2.5μSv/h of personnel operation positions form standard.The measured and theoretical values of dose equivalent rate at 0.5 m are more consistent than those at 0.15 m for ^(225)Ac source,especially under lead shielding conditions of 0 mm,5 mm,10 mm,15 mm,and 20 mm.For the same activity,measured dose equivalent rate of ^(225)Ac is about half of 131I and about 1.5 times of 99mTc theoretical value.We should pay attention to external radiation protection during the use of ^(225)Ac.It is suggested that,20 mm can be used as the lead tenth value thickness,and 5 mm as the lead half value thickness conservatively for ^(225)Ac and its descendants.