X射线剂量当量仪校准因子不确定度评估

为了准确评估X射线剂量监测用防护仪表的校准因子的不确定度,依据有关技术规范,用标准电离室对参考点位置处的剂量当量率参考值进行测量;采用替代法获得待校仪表的显示值,从而确定校准因子结果的相关影响因素,并分别对影响量的不确定度进行评定;得出仪表校准因子的相对扩展不确定度为5.0％(k=2)。影响校准因子不确定度的主要来源包括校准用辐射场的均匀性、标准电离室本身的刻度因子及能量响应、剂量当量转换因子、待检仪表显示值的统计标准偏差等。在对该类仪表的校准过程中,通过提高标准参考值的不确定度水平可以改善校准因子的不确定度。

Uncertainty Evaluation of Calibration Factor for X-ray Dose Equivalent Instrument

In order to accurately evaluate the uncertainty of calibration factors of protective instruments for X-ray dose monitoring, according to the relevant technical specifications, the reference value of dose equivalent rate at the reference point is measured by standard ionization chamber, and the display value of the instrument to be calibrated is obtained by using the substitute method, so as to determine the relevant influencing factors of the calibration factor results, and evaluate the uncertainty of the influencing factors respectively.The relative expanded uncertainty of instrument calibration factor is 5.0% (k=2). The main sources of influence on the uncertainty of calibration factors include the uniformity of radiation field for calibration, calibration factors and energy response of the standard ionization chamber itself, dose equivalent conversion factor, statistical standard deviation of display value of instruments to be tested, etc. In the process of calibration, the uncertainty of calibration factor can be improved by increasing the uncertainty level of standard reference value.