Management of hydrazine based aqueous waste resulted during primary cleanup of degraded PUREX solvent

The destruction of hydrazine in nitric acid medium is crucial for safe handling and disposal of waste generated in nuclear reprocessing operations. In this study, both chemical and electrochemical oxidation routes were investigated for the decomposition of hydrazine. Chemical oxidation using nitrogen dioxide (NO2) in nitrogen gas showed limited efficiency at low NO2 concentrations (1%), whereas a 10% NOx mixture enabled complete destruction of hydrazine within 8 h at a gas flow rate of 10 L per hour. Electrochemical studies conducted using cyclic voltammetry at a platinum electrode revealed hydrazine oxidation as an irreversible, kinetically controlled process, with a relatively high diffusion coefficient. The diffusion coefficient for hydrazine oxidation was measured to be 4 × 10–5 cm2 s−1 at 298 K which was comparable to literature reported values. Based on these findings, a simple two-electrode electrochemical system was evaluated in both divided and undivided cell configurations. Incremental current experiments were performed to identify the optimal current density and current density in the range of 40–50 mAcm−2 was found optimal for hydrazine oxidation. The undivided cell, despite a marginally lower current efficiency, demonstrated comparable performance to the divided setup. The study demonstrates that a cost-effective, undivided electrochemical cell can be effectively utilized for the destruction of hydrazine-containing waste streams, offering a viable approach for integration into nuclear waste treatment processes.