The magnetically assisted chemical separation process is designed to separate transuranic (TRU) elements from high-level waste or TRU waste. Magnetic microparticles (1-25 mu m) were coated with octyl (phenyl)-N,N-diisobutylcarbamoyl-methylphosphine oxide dissolved in tributyl phosphate and tested for removing TRU elements from acidic nitrate solutions. The particles were contacted with nitric acid solutions or simulated Hanford Plutonium Finishing Plant waste solution, irradiated with a high intensity Co-60 gamma-ray source, and evaluated for their effectiveness in removing TRU elements from 2 M HNO3 solutions. The resistance of the coatings and magnetic cores to radiolytic damage and hydrolytic degradation was investigated by irradiating samples of particles suspended in a variety of solutions with doses of up to 5 Mrad. Transmission electron microscopy, magnetic susceptibility measurements, and physical observations of the particles and suspension solutions were used to assess physical changes to the particles. Processes that affect the surface of the particles were found to dramatically alter the binding sites for TRU in solution. Hydrolysis played a larger role than radiolysis in the degradation of the extraction capacity of the particles.