Natural uranium-contaminated soil in Korea Atomic Energy Research Institute (KAERI) was generated by decommissioning of the natural uranium conversion facility in 2010. Some of the contaminated soil was expected to be clearance level, however the disposal cost burden is increasing because it is not classified in advance. In this study, pre-classification method is presented according to the ratio of naturally occurring radioactive material (NORM) and contaminated uranium in the soil. To verify the validity of the method, the verification of the uranium radioactivity concentration estimation method through γ-ray analysis results corrected by self-absorption using MCNP6.2, and the validity of the pre-classification method according to the net peak area ratio were evaluated. Estimating concentration for 238U and 235U with γ-ray analysis using HPGe (GC3018) and MCNP6.2 was verified by 􀟙-spectrometry. The analysis results of different methods were within the deviation range. Clearance screening factors (CSFs) were derived through MCNP6.2, and net peak area ratio were calculated at 295.21 keV, 351.92 keV(214Pb), 609.31 keV, 1120.28 keV, 1764.49 keV(214Bi) of to the 92.59 keV. CSFs for contaminated soil and natural soil were compared with U/Pb ratio. CSFs and radioactivity concentrations were measured, and the deviation from the 60 minute measurement results was compared in natural soil. Pre-classification is possible using by CSFs measured for more than 5 minutes to the average concentration of 214Pb or 214Bi in contaminated soil. In this study, the pre-classification method of clearance determination in contaminated soil was evaluated, and it was relatively accurate in a shorter measurement time than the method using the concentrations. This method is expected to be used as a simple pre-classification method through additional research.

• Kyungmin Kim(Korea Atomic Energy Research Institute (KAERI)) Corresponding author
• Jeongwook Moon(Korea Atomic Energy Research Institute (KAERI))
• Dong-Ju Lee(Korea Atomic Energy Research Institute (KAERI))
• Il-Sik Kang(Korea Atomic Energy Research Institute (KAERI))
• Dae Seong Nam(Korea Atomic Energy Research Institute (KAERI))
• Jong Hwa Pack(Korea Atomic Energy Research Institute (KAERI))
• Sung Jin Han(Korea Atomic Energy Research Institute (KAERI))
• Yun Gun Jung(Korea Atomic Energy Research Institute (KAERI))
• Heung-Ju Cho(Korea Atomic Energy Research Institute (KAERI))
• Hongrae Jeon(Korea Atomic Energy Research Institute (KAERI))
• Tack-Jin Kim(Korea Atomic Energy Research Institute (KAERI))