Decomposition of 14C containing organic molecules released from radioactive waste by gamma-radiolysis under repository conditions

Decomposition of 14C containing organic molecules into an inorganic compound has been investigated by γ-ray irradiation experiments under simulated repository conditions for radioactive waste. Lower molecular weight organic acids, alcohols, and aldehydes leached from metallic waste are reacted with OH radicals to give carbonic acid. A decomposition efficiency that expresses consumption of OH radicals by decomposition reaction of organic molecules is proposed. Decomposition efficiency increases with increasing concentration of organic molecules (1×10−6–1×10−3 mol dm−3) and is not dependent on dose rate (10–1000 Gy h−1). Observed dependence indicates that decomposition efficiency is determined by reaction probability of OH radicals with organic molecules.