Electrochemical determination of the corrosion behavior of candidate alloys proposed for containment of high level nuclear waste in tuff

Abstract

Long-term geological disposal of nuclear waste requires corrosionresistant 'mister materials for encapsulation. Several austenitic stainless steels are under consideration for such purposes for the disposal of high-levl waste at the candidate repository site located at Yucca Mountain, Nevada. Witn regard to corrosion considerations, a worst case scenario at this prospective repository location would result from the intrusion of vadose water. This preliminary study focuses on the electrochemical and corrosion behavior of the candidate canister materials under worst-case repository environments. Electrochemical parameters related ;o localized attack (e.g., pitting potentials) and the electrochemical corrosion rates have been examined.

Yucca Mountain project canister material corrosion studies as applied to the electrometallurgical treatment metallic waste form

“…In reported immersion tests that investigated general corrosion rates of Types 304L, 316L, 317L, 321, and 347 stainless steels and Incoloy 825 in J-13 water in the 50 to 100°C range, the corrosion rate was found to be independent of temperature imd the corrosion was uniformly distributed over the exposed surface [22]. No significant difference in corrosion rates were observed for Types 304L, 316L, and 317L stainless steels in 50,70,80,90, and 100°C J-13 water at exposure times of 3,548 and 5,000 hours.…”

“…Since canisters will experience high-temperature air environments, Glass et al [22] have investigated how thermally formed films on stainless steels affect pitting susceptibility in chloride media. It has been reported that Type 304L stainless steel has a maximum sensitivity to pitting that occurs following oxidation in dry air at 300°C [22].…”

“…Electrochemical test results have shown that for the stainless steel candidate materials investigated (including Types 304L, 316L, 317L, 321, and 347 stainless steels, and Incoloy 825), the corrosion potentials were insensitive to temperature up to 90°C [22,26]. Glass et al reported tests of Types 304L and 316L stainless steels and Incoloy 825 in 5-13 well water and found no dependence of the corrosion potential on temperature, in the temperature range of 50-.…”

“…anodic polarization scans, and faed-potential passive current density tests, with examples of these types of tests reported by Duquette et al [21]. Glass et al [22] employed two other types of electrochemical tests: Tafel extrapolation and linear polarization resistance. Huizinga and de Jong [23] have reported using cyclic polarization, staircase polarization, stepwise repassivation, and scratch repassivation methods for studying initiation, propagation, and repassivation of pitting for a variety of stainless steels.…”

“…The pitting susceptibility of an alloy is determined by establishing the pitting and protection potential of an alloy relative to the corrosion potential. One important point is that the values for Ep, Eprot, and EcoE are in many cases dependent upon the particular electrochemical technique employed [22]. When generating potential curves as a function of current, the curves are generally considered reproducible for a corrosion potential of BOmV and a factor of 2 for current densib at any potential [25].…”