Radioactivities of H-3 and C-14 in spent radioactive ion exchange resins and spent radioactive lubricant oils released from nuclear power plants, has been determined using a combustion and sorption method (combustion method). The liquid scintillation counting (LSC) spectra showed that the interference of other radionuclides has not significantly affected the determination of radioactivities of H-3 and C-14 in the radwaste samples. The chemical structure of (CO2)-C-14, which originated from the combustion of radwastes, trapped C-14 sorbent has been investigated using Fourier transform infrared spectroscopy (FT-IR). FTIR study showed interesting results that peaks for uncoupled CO2 and carbonic amide appeared at FT-IR spectra of CO2 high-absorbed C-14 sorbents, while the peak for carbamate was only observed at the spectra of CO2 low-absorbed sorbents. During the CO2 sorption in C-14 sorbent, temperature and viscosity of the sorbent increased owing to decrease of enthalpy and increase of apparent molecular weight of the sorbent caused by the bonding formation between sorbent molecules. (C) 2017 Elsevier B.V. All rights reserved.