Oxidation kinetics of spent low-level radioactive resins

Experimentally, two-stage oxidation of spent low-level radioactive resin was found by thermo-gravimetric analysis (TGA). About 24% of the spent resins was oxidized at 600 to 900 K. Online Fourier transform infrared spectra showed that the decomposition of the -SO₃H species in the resin to SO ₂ occurred at 670 and 1020 K. The numerical calculation from TGA weight loss data at different heating rates showed that the global activation energies for oxidation of the spent resins were 108 to 138 kJ·mol ^-1. The reaction orders for resin and oxygen were about 1.0 and 3.5, respectively. The global rate equations for oxidation of the resin in the first and second stages can be expressed as dx₁/dt (s^-1 ) = 2.3 × 10⁷ (s^-1)exp[-117900(J·mol ^-1)/T(K)][1 - x (%)]^0.82 [O₂ (vt%)] ^3.5 (x denotes the reaction conversion) and dx₂/dt = 8.4 × 10¹⁷exp(-239500/RT) (1 - x)^0-9[O₂] ^4.5,respectively.