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目的对于放射工作人员可能直接接触放射源的倒源活动,通过理论计算和现场测量提出操作人员的剂量控制目标,为优化倒源操作、避免操作人员受到超剂量照射提供依据。方法在将活度为11.1 GBq的137Cs源从储源铅罐转移到校准装置的源室中,根据放射源的活度、倒源操作特点和剂量管理要求,通过理论计算预计操作人员所在位置的剂量率约2.95 m Sv·h-1,监测点的剂量率约47.2 m Sv·h-1,由此确定倒源操作人员在此次倒源活动中的剂量控制水平为40μSv,操作时间应控制在48 s以内,根据计算要求对倒源操作进行了优化。结果与源150 mm处的监测点最大剂量率55.98 m Sv·h-1,倒源操作人员位置的最大剂量率约为3.5 m Sv·h-1,倒源操作总时间不超过20 s,因此,该次倒源操作过程中操作人员受照剂量不超过19.5μSv。结论说明合理应用剂量限值原则能够有效指导辐射实践中的防护优化,避免放射工作人员受到超剂量照射。
OBJECTIVE For radiation workers who may have direct contact with the sources of radioactive sources, the dosage control objectives of the operators are proposed through theoretical calculations and field measurements. This provides the basis for optimizing the operation of inverting sources and avoiding the operators being exposed to overdoses. Methods The 137Cs source with the activity of 11.1 GBq was transferred from the storage lead tank to the source chamber of the calibration device. According to the activity of the radioactive sources, operational characteristics of the reverse source and dose management requirements, the theoretical calculation of the location of the operator Dose rate of about 2.95 mSv · h-1, the monitoring point dose rate of about 47.2 mSv · h-1, thus determining the source operator in the inverted activity of the dose control level of 40μSv, operation time should be controlled Within 48 seconds, the back-up operation was optimized according to the calculation requirements. Results The maximum dose rate at the monitoring point of 150 mm from the source was 55.98 mSv · h-1. The maximum dose rate at the inverted operator position was about 3.5 m Sv · h-1, and the total time for the inverted operation was less than 20 s , The operation of the source of the inverted operation dose not exceed 19.5μSv. The conclusion shows that the principle of reasonable application of dose limits can effectively guide the optimization of radiation protection practice and avoid radiation workers over exposure.