Corrosion interactions between stainless steel and lead vanado-iodoapatite nuclear waste form part I

Abstract

This study explores the corrosion interactions between a metallic canister material, stainless steel (SS) 316, and an I-bearing ceramic waste form, lead vanado-iodoapatite (I-APT, Pb 9.85 (VO 4) 6 I 1.7), in a chloride solution. Crevice corrosion of the SS in close proximity to the I-APT resulted in the development of an aggressive environment at the interface of the two materials, which was acidic and enriched in Cl − anions. I-APT also corroded in the crevice region, primarily through ion-exchange between the I − ions from the I-APT matrix and anions from the environment. The enrichment of Cl − anions within the occluded crevice space as the result of SS crevice corrosion enhanced the corrosion of I-APT. The release of iodine from this apatite waste form could be accelerated owing to this mechanism. This is evidenced by a depletion of iodine from the I-APT matrix and a large amount of Cl-bearing precipitates on the surfaces of both SS and I-APT. On the other hand, the corrosion of I-APT leads to the precipitation of a V-and Pb-rich layer, which inhibits the localized corrosion of SS to an extent. This study advances the understanding of the near-field corrosion interactions between metallic canisters and ceramic waste forms.

Corrosion interactions between stainless steel and lead vanado-iodoapatite nuclear waste form part II

“…However, in a typical SS crevice, the local pH could be lower than 1 12 . This indicates that the crevice corrosion of SS may have been locally suppressed by the corrosion products of I-APT, which is consistent with the results presented in Part I of this paper 25 .…”

“…7f). The Raman spectra were significantly different compared to those collected from the precipitated phases on SS surface corroded near I-APT (see Part I 25 ). As a matter of fact, the formation of chervetite may be more favorable than apatite under acidic conditions.…”

“…Part I of this paper reports the corrosion interactions between SS and a model ceramic waste form, lead vanado-iodoapatite (I-APT, Pb 9.85 (VO 4 ) 6 I 1.7 ), for the immobilization of radioactive iodine-129 25 . It was found that the corrosion products of I-APT, including Pb-rich and V-rich species, are beneficial for the corrosion inhibition of SS.…”

Review of corrosion interactions between different materials relevant to disposal of high-level nuclear waste

“…Therefore, it is expected that the ion exchange process may be facilitated between the Cl − ions and ceramics with exchangeable anions in a crevice corrosion environment. This hypothesis was validated by Guo, Yao and their colleagues by corroding SS in close proximity to an I-bearing apatite (I-APT) in an oxic environment 91,92 . It was found that the corrosion of I-APT was enhanced by the crevice corrosion of SS, as evidenced by the increased alteration layer thickness in the crevice mouth area of the I-APT.…”

“…Another interaction mechanism between crystalline ceramics and metals is based on the effects of metal crevice corrosion, as disclosed in recent studies by Guo et al 45,91,92 . who revealed a synergistic corrosion interaction between SS and a Cr-bearing hollandite in an oxic environment 45 .…”