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Title: Localized Corrosion Behavior of Type 304SS with a Silica Layer Under Atmospheric Corrosion Environments

Abstract

The U.S. Department of Energy (DOE) has proposed a potential repository for spent nuclear fuel and high-level radioactive waste at the Yucca Mountain site in Nevada. [I] The temperature could be high on the waste packages, and it is possible that dripping water or humidity could interact with rock dust particulate to form a thin electrolyte layer with concentrated ionic species. Under these conditions, it is possible that highly corrosion-resistant alloys (CRAs) used as packages to dispose the nuclear waste could suffer localized corrosion. Therefore, to better understand long-term corrosion performance of CRAs in the repository, it is important to investigate localized corrosion under a simulated repository environment. We measured open circuit potential (OCP) and galvanic current (i{sub g}) for silica-coated Type 304SS during drying of salt solutions under controlled RH environments to clarify the effect of silica layer as a dust layer simulant on localized corrosion under atmospheric environments. Type 304SS was used as a relatively susceptible model CRA instead of the much more corrosion resistant alloys, such as Alloy 22, that are being considered as, waste package materials.

Authors:
;
Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
USDOE
OSTI Identifier:
893925
Report Number(s):
NA
MOL.20060705.0068, DC# 47393; TRN: US0700074
DOE Contract Number:
NA
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 36 MATERIALS SCIENCE; ALLOYS; CORROSION; CORROSION RESISTANT ALLOYS; DRYING; DUSTS; ELECTROLYTES; HIGH-LEVEL RADIOACTIVE WASTES; HUMIDITY; NUCLEAR FUELS; PARTICULATES; RADIOACTIVE WASTES; SILICA; WASTES; WATER; YUCCA MOUNTAIN

Citation Formats

E. Tada, and G.S. Frankel. Localized Corrosion Behavior of Type 304SS with a Silica Layer Under Atmospheric Corrosion Environments. United States: N. p., 2006. Web. doi:10.2172/893925.
E. Tada, & G.S. Frankel. Localized Corrosion Behavior of Type 304SS with a Silica Layer Under Atmospheric Corrosion Environments. United States. doi:10.2172/893925.
E. Tada, and G.S. Frankel. Mon . "Localized Corrosion Behavior of Type 304SS with a Silica Layer Under Atmospheric Corrosion Environments". United States. doi:10.2172/893925. https://www.osti.gov/servlets/purl/893925.
@article{osti_893925,
title = {Localized Corrosion Behavior of Type 304SS with a Silica Layer Under Atmospheric Corrosion Environments},
author = {E. Tada and G.S. Frankel},
abstractNote = {The U.S. Department of Energy (DOE) has proposed a potential repository for spent nuclear fuel and high-level radioactive waste at the Yucca Mountain site in Nevada. [I] The temperature could be high on the waste packages, and it is possible that dripping water or humidity could interact with rock dust particulate to form a thin electrolyte layer with concentrated ionic species. Under these conditions, it is possible that highly corrosion-resistant alloys (CRAs) used as packages to dispose the nuclear waste could suffer localized corrosion. Therefore, to better understand long-term corrosion performance of CRAs in the repository, it is important to investigate localized corrosion under a simulated repository environment. We measured open circuit potential (OCP) and galvanic current (i{sub g}) for silica-coated Type 304SS during drying of salt solutions under controlled RH environments to clarify the effect of silica layer as a dust layer simulant on localized corrosion under atmospheric environments. Type 304SS was used as a relatively susceptible model CRA instead of the much more corrosion resistant alloys, such as Alloy 22, that are being considered as, waste package materials.},
doi = {10.2172/893925},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Mar 13 00:00:00 EST 2006},
month = {Mon Mar 13 00:00:00 EST 2006}
}

Technical Report:

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  • Corrosion resistant materials under atmospheric conditions can suffer from localized corrosion (e.g., pitting, crevice, stress-corrosion cracking). The stability of such a localized corrosion site requires that the site (anode) must dissolve at a sufficiently high rate to maintain the critical chemistry and that it be coupled to a wetted surrounding area (cathode) that can provide a matching cathodic current. The objectives of this study were to computationally characterize the stability of such a local corrosion system and to explore the effects of physiochemical and electrochemical parameters. The overall goal of the work is to contribute to the establishment of amore » scientific basis for the prediction of the stabilization of localized attack. An analytical method is presented for evaluating the stability of localized corrosion of corrosion-resistant alloys under thin-layer (or atmospheric) conditions. The method requires input data that are either thermodynamic in nature or easily obtained experimentally. The maximum cathode current available depends on the cathode geometry, temperature, relative humidity, deposition density of salt (i.e., mass of salt per unit area of cathode), and interfacial electrochemical kinetics. The anode demand depends on the crevice geometry, the position of attack within the crevice, and the localized corrosion stability product. The localized corrosion stability product, i*x, is the product of the current density at the localized corrosion site and the depth of that localized corrosion site. By coupling these two approaches for analysis of the current capacity of the cathode and the current demand of the anode, the stability of a crevice can be determined for a given environmental scenario. The method has been applied to the atmospheric localized corrosion of Type 31GL stainless steel as well as Alloy C-22. The effects of the key parameters are described and compared.« less
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  • The corrosion behavior of Type 304 stainless steel in molten NaNO/sub 3/-KNO/sub 3/ was studied at temperatures between 600/sup 0/C and 350/sup 0/C using thermal convection loops. Corrosion rates were somewhat less than 2.5 x 10/sup -2/ mm/year (1 mil/year) at the maximum temperature. Two corrosion processes were observed, formation of oxide scales and depletion of chromium from the alloy. Oxidation products generally consisted of at least two layers, a layer of Fe/sub 3/O/sub 4/ over an iron-chromium spinel. In addition, a complex oxide was detected which appeared to be a double oxide of iron and, a salt impurity, magnesium.more » Chromium accumulated as a soluble product in the melt but thermal gradient mass transfer was not observed. Chromium depletion kinetics were approximately parabolic with time suggesting a diffusion controlled process. Autogenous weldments experienced somewhat more corrosion in the heat-affected zone than either the fusion zone or the parent alloy.« less
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