Estimation of Uncertainty for Neutron Dose Measurements

Abstract

When performing radiation protection for neutrons at nuclear reactor workplaces, accelerator workplaces, and RI workplaces, etc. (hereinafter referred to as workplace), it is important that the measured values of neutron survey meters and personal dosimeters are reliable values. The reliability of measured values is estimated by measuring with calibrated measuring instruments which ensure the traceability, and then adding the accuracy to the measured value. Traceability-ensured calibration means that the results measured by using neutron survey meters etc. can be traced back to the standard value of the primary standard laboratory without interruption. The accuracy can be indicated by adding the estimated uncertainty. Here, the method of estimating uncertainty is introduced, then two examples of the estimation of uncertainty are also introduced; the first example is the uncertainty estimated when the end user’s neutron survey meter is calibrated in the secondary laboratory, and the second one is the uncertainty estimated when the end user measures neutron dose with neutron survey meters in the workplace. Note that neutron measuring instruments such as neutron survey meters, etc. do not have good response characteristics to neutron energy compared with the response characteristics of photo dosimeters to photon energy. Therefore, it should be fully noted that the measurement of the dosimetry in the workplace and the estimation of uncertainty are greatly affected by both response characteristics of dosimeters and neutron energy spectrum in the workplace.