Effect of metallic redox ions on the corrosion behavior of GTAW weldment of type 304L stainless steel in simulated non-radioactive PUREX and HLLW medium.

Nuclear-spent fuel reprocessing and high-level liquid waste (HLLW) storage containers possess various inorganic higher valance oxidizing metallic ions and fission products, further influencing nitric acid corrosion through the PUREX route. This study evaluated the effect of nitric acid corrosion on gas-tungsten arc weldment (GTAW) of stainless steel (SS) 304 L in simulated reprocessing and HLLW medium in non-radioactive conditions. The effect of oxidizing metallic cations, which were present as the major amount in the mark-I spent fuel of fast breeder test reactors (FBTR) in India; these are Cs+1, Nd+3, Mo+6, Fe+3, and V+5 as a surrogate redox system for Pu(VI)/Pu(IV) and Np(VI)/Np(V) system was evaluated by the electrochemical corrosion test method in 2 M, 6 M, and 8 M nitric acid solutions. The resistance of polarization (Rp) value decreases with the nitric acid concentration, and the effect of oxidizing ions in different nitric acid concentrations also changes. The three-phase corrosion (boiling liquid, vapor, and condensate phase) resistance behavior in different concentrations (6 M and 8 M) of the nitric acid medium, without and with redox ions, has been evaluated. The corrosion rate is higher in the liquid phase compared to the vapor and condensate phases. On the other hand, it is relatively higher for the inorganic metallic redox ions containing solutions. [Display omitted] • Corrosion of the GTAW SS 304 L was evaluated in nonradioactive PUREX and HLLW medium. • Increase in nitric acid concentration, trans-passive corrosion tendency increases. • Corrosion by the metallic ion depends on its effective redox potential in the medium. • The weldment material is more corrosion-resistant than its base metal counterpart. • The descending trend of the three-phase corrosion is that liquid > vapor > condensate. [ABSTRACT FROM AUTHOR]