An Analysis of Radiation Field Characteristics for Extremity Dosimetry in Nuclear Power Plants

Workers who maintain the water chambers of steam generators during the maintenance period in Nuclear Power Plants (NPPs) have a higher likelihood of high radiation exposure even if they were exposed for a short period of time. In particular, it is expected that the hands would receive the highest radiation exposure because of its contact with radiation materials. In this study, characteristic analysis of inhomogeneous radiation fields for contact operations was conducted using Thermoluminescent Dosimeter (TLD) readouts from the application tests of two-dosimeter algorithms to Korean NPPs. It was observed that inhomogeneous radiation fields for contact operations in NPPs were dominated by high-energy photons, such as Co and Co. In addition, field tests for workers who maintained the steam generator during an outage at Ulchin NPPs in 2009 were conducted to analyze the radiation fields and to estimate the extremity dose. As a result, the radiation fields were dominated by high-energy photons while the extremity dose was two times higher than that of the deep dose.