Progressive Solutions to Improve Corrosion Resistance for Nuclear Waste Storage: Corrosion and Aspects of Environmentally Safe Processing of Nuclear Waste Storage Materials
Sponsored by: TMS Corrosion and Environmental Effects Committee, ACerS Glass & Optical Materials Division
Program Organizers: Madeleine Jordache, Stevens Institute of Technology; Gary Pickrell, Virginia Tech
Wednesday 10:20 AM
October 20, 2021
Room: A221
Location: Greater Columbus Convention Center
Session Chair: Madeleine Jordache, Stevens Institute of Technology; Gary Pickrell, Virginia Tech
10:20 AM Introductory Comments
10:25 AM
Using Stress Modelling to Understand Effects of Pit Morphology on Stress Corrosion Cracking Initiation in Austenitic Stainless Steels: Alana Parey1; Jay Srinivasan2; Rebecca Schaller3; Eric Schindelholz2; Jenifer Locke2; 1Sandia National Laboratory, The Ohio State University; 2The Ohio State University; 3Sandia National Laboratory
During extended nuclear waste storage, chloride-containing brines may form on the surface of austenitic stainless-steel spent nuclear fuel canisters resulting in atmospheric corrosion and possibly stress corrosion cracking. Pit morphology and size depend on the chemistries of these brines which are a function of the local temperature and relative humidity (RH). Under low RH conditions, irregular pitting, crosshatching, and microcracking are present which may affect SCC initiation. This study aims to determine the stress concentration profile surrounding pits of various sizes and geometries, particularly pits with high radius of curvature fissures and microcracks. Through combining experimental data with modelling, pit size and morphology can be compared in terms of their potential to initiate SCC. SCC testing and modelling will be conducted at temperature and RH levels amenable to replicating relevant pit morphologies, gaining insight into crack initiation. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.SAND2021-2878A
10:45 AM
A Geopolymer for Hanford Secondary Waste: Sepideh Akhbarifar1; Weiliang Gong1; Werner Lutze1; Ian Pegg1; 1Catholic University of America -Vitreous State Lab
Preceding this work, a geopolymer was developed at CUA to solidify ‘Hanford Secondary Waste’, which contains low levels of hazardous metals, 99Tc, and 129I. All waste elements were fixated at least as well as in other candidate waste forms. Scale-up testing revealed that using only two pozzolans (slag and metakaolin) to make the geopolymer limited desirable ranges of rheological properties and set times for large-scale production. Including a third pozzolan (fly ash) provided sufficient flexibility. We report on a quantitative evaluation of the rheological properties and set times of geopolymers made with the three pozzolans. The rheological set time will be compared with that of the Vicat tests. The composition dependence of compressive strength will be discussed. Expecting that a fast-growing fraction of electricity will be produced from renewable sources and the continuing use of nuclear power, the already very low CO2 footprint of geopolymers will approach zero.
11:05 AM Invited
Understanding Corrosion of Nuclear Waste Glasses through Molecular Dynamics Simulations and Quantitative Structural Property Relationship Analysis: Jincheng Du1; 1University of North Texas
Glass is a well-accepted nuclear waste form and the its long-term durability is one of the most important material characteristics to ensure safe disposal and prevention the release of radioactive elements to the environment. Detailed understanding of the glass structure and glass-water reaction mechanisms is required to accurately predict the chemical durability. In this talk, I will present applications of molecular dynamic simulations of complex borosilicate nuclear waste glasses and validation of the structural models with experimental characterizations. Quantitative Structural Property Relationship (QSPR) analysis is used as a valuable means to find correlations of the such as initial dissolution rate and other properties with its structural descriptor obtained from structural models from MD simulations. By testing in a wide range of borosilicate glasses with different corrosion rates, the results show that QSPR is a promising approach to predict the corrosion rate and other glass properties of nuclear waste glasses.
11:35 AM Invited
Predicting Zeolites’ Stability during the Corrosion of Nuclear Waste Immobilization Glasses: Mathieu Bauchy1; 1University of California, Los Angeles
The precipitation of zeolite has been linked to a delayed acceleration in nuclear waste immobilization glass corrosion (Stage III). Here, we compile a unified thermodynamic database to estimate the stability of secondary phases (including zeolites, clays, and CSH phases). Based on this, we report a geochemical model to predict the stability of secondary phases upon the dissolution of glasses. This approach offers a realistic description of the stability of the secondary phases forming during the dissolution of the International Simple Glass as a function of temperature and pH. We find that the formation of silica and clay secondary phases is thermodynamically favored at low pH (pH < 10), whereas zeolite and CSH phases are favored at high pH (pH > 10.5). This suggests that thermodynamics (not solely kinetics) plays a key role in determining the range of pH wherein stage III corrosion may occur, i.e., when zeolite formation is favored.