MateriAlZ Seminar: John S. McCloy
Friday, March 15, 2024 - 11:00 a.m. Arizona Time
John S. McCloy
Professor and Director of the School of Mechanical & Materials Engineering
Lindholm Endowed Chair in Materials Engineering
Washington State University
"Nuclear Waste Glass Design: Halide Incorporation in Aluminoborosilicate Glass"
Zoom link | Passcode: 683705
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Abstract
The modern world requires more and more energy to power computers, vehicles, and everything in between. The choices around environmentally responsible fuels and electricity have been hotly debated over the last decade, given concerns about climate change and large-scale industrial accidents. One energy source important for the state of Washington is nuclear power, and the state has a long history with nuclear technology dating back to the Manhattan project, and the irradiation of nuclear fuel and separation of plutonium for nuclear weapons. Activities at the Hanford site in southeastern Washington state from the 1940s-1980s resulted in a legacy of radioactive and highly complex chemical waste, now currently in remediation by the U.S. Department of Energy. About 212,000 cubic meters (~56 million gallons) of radioactive waste is currently stored in 177 underground tanks at the Hanford site. The tank waste is highly heterogeneous, with some tanks consisting of large fractions of settled solid high-level waste (HLW) and others consisting of mostly caustic supernatant liquid and solid salt cake low activity waste (LAW). Vitrification of radioactive waste, mostly in borosilicate glass, has been the accepted baseline immobilization technology for many nations for over 50 years. Non-radioactive commissioning of the Hanford LAW Joule-heated ceramic-lined melter began in 2023. Glass compositions are designed to maximize waste loading and glass production rate, while maintaining predictable properties and processing envelopes. Several physical phenomena limit waste loading in LAW glass, including formation of a molten salt layer containing alkali, sulfate, halides, and some radioactive components (e.g., Cs, Tc). Volatiles in silicate melts, including F-, Cl-, and SO42-, play a vital role in materials and processes including volcanism, optical materials, bioglasses, electrofining, and nuclear waste vitrification. In nuclear waste vitrification, volatiles play a significant role in inducing salt formation, which is deleterious to melter operations and waste form durability. A series of Na-Ca-Al-B-Si-O glasses with SO42- were synthesized with progressive additions of F or Cl to investigate the effect of halides on salt formation. The effects of these halides on the glasses were examined using multiple characterization techniques, including X-ray diffraction, thermal analysis, nuclear magnetic resonance, Raman spectroscopy, and nano-computed tomography. It was found that the behavior of Cl and F in LAW glasses with sulfate additions is significantly more complex than predicted by current models.
Bio
Dr. John S. McCloy is professor and current director of the School of Mechanical & Materials Engineering and Lindholm Endowed Chair in Materials Engineering at Washington State University (WSU) in Pullman, WA. His professional career includes stints in academia (10 y), national laboratory (5 y), and industry (10 y) – a professor at WSU since 2013, a research scientist at Pacific Northwest National Laboratory (where he retains a joint appointment as chief scientist), and a Raytheon multi-disciplined engineer in Tucson. At WSU, he leads the Nuclear, Optical, Magnetic, & Electronic (NOME) Materials Lab and the Crystals and SemiConductors (CASC) group, both within the Institute of Materials Research (IMR). His main interests in materials lie within crystal chemistry and solid-state physics, as well as advanced characterization techniques. He holds a BS degree in materials science & engineering (MSE) from the Massachusetts Institute of Technology, an MA in cultural anthropology and an MS and PhD in MSE from the University of Arizona. He is an author or co-author of over 200 journal articles, plus over 50 more book chapters, conference proceedings, public reports, and patents. He is a Fellow of the American Ceramic Society, a senior member of SPIE, and a former Fulbright Scholar.