Progressive Solutions to Improve Corrosion Resistance of Nuclear Waste Storage Materials: Thermal History Effects on Borosilicate Glasses and Glass Ceramics and Canisters Stress Corrosion Cracking Mitigation
Sponsored by: TMS Corrosion and Environmental Effects Committee, TMS: Nuclear Materials Committee
Program Organizers: Madeleine Jordache, Stevens Institute of Technology; Gary Pickrell, Virginia Tech; Bai Cui, University of Nebraska Lincoln
Wednesday 2:00 PM
October 12, 2022
Room: 333
Location: David L. Lawrence Convention Center
Session Chair: Madeleine Jordache, Stevens Institute of Technology; Bai Cui, University of Nebraska - Lincoln; Gary Pickrell, Virginia Tech
2:00 PM Introductory Comments
2:05 PM Invited
SCC of Nuclear Waste Canisters: Mechanisms and Mitigation: Janelle Wharry1; Haozheng Qu1; Timothy Montoya2; Jason Taylor2; Kyle Johnson3; Rebecca Schaller2; Eric Schindelholz4; 1Purdue University; 2Sandia National Laboratories; 3VRC Metal Systems; 4The Ohio State University
This talk aims to understand stress corrosion cracking (SCC) mechanisms and mitigation in nuclear waste storage canisters. In the U.S., more than 86,000 metric tons of nuclear waste are stored in stainless steel canisters within concrete overpacks. Vertical seam welds on canisters may be susceptible to chloride-induced SCC (CISCC). Here, we examine CISCC micromechanisms and explore cold spray as a CISCC mitigation strategy. Coupons of arc welded 304L stainless steel are cold sprayed with 304L, then submerged in boiling MgCl2. In an unsprayed reference, transgranular SCC occurs in the weld heat affected zone; crack propagation is dependent upon Schmid and Taylor factor mismatch. Meanwhile, cold sprayed specimens are resistant to CISCC, although the cold spray layer experiences crevice corrosion. Results are discussed in the context of residual stress, localized strain, and crack tip-dislocation interactions. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. This document is SAND2022-4685A.
2:25 PM Invited
From Preferential Bonding to Phase Separation in Boro-silicate Glasses: Doris Möncke1; 1Alfred University
Infrared and Raman spectroscopy reveal significant differences in the near and intermediate range order of alkali borosilicate glasses, including in the interconnectivities of borate and silicate units. For low alkali borosilicate glasses, changes in the quenching rate reflect on a different degree of mixing between borate and silicate units, with increasingly more homonuclear bonds for low and more mixed B-O-Si bonds for high fictive temperatures. 2D correlation NMR showed that tetrahedral borate groups avoid bonding to silicate over other borate groups. However, for higher alkali glasses with a significant number of non-bridging oxygen atoms, silicate and borate tetrahedra do not avoid direct linkages. Heat treatment, or the addition of rare earth or transition metal oxides can enhance preferential bonding in low alkali glasses and induce clustering and even visible phase separation. Changing the alkali oxide from Li to Cs, can significantly alter the connectivity of the borate and silicate sub-networks.
2:55 PM Invited
Microstructural Development and Chemical Durability of a Borosilicate Glass-ceramic Waste-form: Richard Brow1; Nicholas Roberts1; Paul Porter1; Jarrod Crum2; 1Missouri University of Science and Technology; 2Pacific Northwest National Lab
A borosilicate glass-ceramic waste-form has been developed to immobilize MoO3-rich waste streams by incorporating soluble alkaline earth molybdates in a chemically durable glass-ceramic that includes chemically stable crystalline rare earth silicates (oxyapatite) [1]. In this paper, we describe the microstructural evolution of these materials from a) melts that were dynamically quenched at rates from >300°C/sec to CCC-conditions (~0.01°C/sec); and b) melts that were quenched, then held under isothermal conditions. Quantitative phase information obtained by analytical electron microscopy, X-ray diffraction, and Raman spectroscopy is used to construct Time-Temperature-Transformation diagrams that summarize the effects of thermal histories on the development of the powellite and oxyapatite phases and the nature of the residual glass phase. This information then is used to explain the effects of microstructure on the relative release rates of ions from the heat-treated glasses. [1] JV Crum, et al., J. Nucl. Mater., 482 1 (2016).