This study is to develop a chemical decontamination technology applicable in a high radiation field such as spent fuel decontamination. A new decontamination formulation was developed in this study by adding ascorbic acid into the existing KAERI chemicals mainly consisting of EDTA and citric acid showed remarkable improvement in dissolution rate of nickel ferrite particles which were hard to be removed by conventional chemical decontamination reagents. The decontamination process development using the reagent was also carried out in this study. The hot loop decontamination tests using the specimens of Inconel-600 and SUS-304 contacted with the pressure boundary of primary coolant in Kori Unit 1 showed high decontamination factors which is as good as or even better than those of foreign processes such as LOMI and CAN-DECON. The decontamination test using spent fuel rod in Kori Unit 1 resulted in almost complete removal of crud from the rod surface. The material damages measured by corrosion surveilance specimen were very small and no localized corrosion were detected. The catalytic wet oxidation behaviors were also studied to decompose decontamination wastes. The Fe(II) catalyst was found to be effective. (Author).