For the final disposal of radioactive waste, concentration of gamma nuclides such as Co-58, Co-60, Cs-137, Nb-94 have to be determined to meet nuclear regulatory requirements. In general, gamma nuclide analysis can be performed with simple sample pretreatment without complicated chemical separation processes due to the characteristics of the nuclide and high resolution of the measuring equipment. However, when the concentration of Co-60 is high in a specific radioactive waste generated at the NPP, the background is increased by the compton continuum of Co-60. That makes it difficult to evaluate accurately Nb-94, which is in the lower energy band than the gamma ray energy region of Co-60 and especially Cs-137, which is used as a key nuclide of scaling factor. In this study, We consider the problem of MDA dissatisfaction or overestimation due to the increased background by Co-60.

• Kahee Jeong(Korea Hydro and Nuclear Power (KHNP) Central Research Institute (KHNP-CRI)) Corresponding author
• Sooyeon Lim(Korea Hydro and Nuclear Power (KHNP) Central Research Institute (KHNP-CRI))
• Ji Eun Park(Korea Hydro and Nuclear Power (KHNP) Central Research Institute (KHNP-CRI))
• Wook Sohn(Korea Hydro and Nuclear Power (KHNP) Central Research Institute (KHNP-CRI))