Quantification of Nb and Zr in the irradiated pressure tubes from Wolsong CANDU Unit 1 by neutron activation analysis

When the Wolsong 1st CANDU reactor in Korea is reaching the end of its original lifespan, decommissioning has been one of the largest issues faced by the nuclear industry and the government for the estimation of expense. The radioactive sources in the construction stuffs and components of the reactor such as pressure tubes, steam generators must be evaluated for the estimation of the appropriate expense for the decommissioning. Unfortunately we do not have exact information about the initial composition of the pressure tubes. In this study the elemental contents of Nb and Zr in the activated zircaloy pressure tubes was investigated. Nb is one of the important elements that characterize the physical and mechanical properties of the pressure tube and a major source of high radioactivity. The prepared samples were strongly irradiated again in the vertical irradiation channel at the HANARO research reactor in the Korea Atomic Energy Research Institute (KAERI) and then measured by an HPGe detector.