MSE Virtual Seminar: “Stabilization of Nuclear Wastes by Vitrification”

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IAN PEGG, PH.D.

PROFESSOR
DIRECTOR OF THE VITREOUS STATE LABORATORY
THE CATHOLIC UNIVERSITY OF AMERICA

Dr. Ian L. Pegg is Professor of Physics and Director of the Vitreous State Laboratory (VSL) at The Catholic University of America where he manages and directs a staff that has reached 110 scientists, engineers, and technicians working in a variety of basic and applied research and development areas. His research has spanned various areas of materials science including the optimization of processes and glass compositions for use in nuclear waste disposal, geopolymers, nano-materials, and thermoelectrics. Dr. Pegg has led numerous vitrification R&D programs involving the development and characterization of glass formulations and the demonstration and scale-up of Joule-heated melting processes. He was the Principal Investigator for the vitrification development program that supported the Duratek, Inc. M-Area facility, the world’s largest joule-heated radioactive production melter. He was also the Project Manager and Co-Principal Investigator for the West Valley Support task at VSL that developed and characterized the optimal glass formulation used for the vitrification of all of the high-level nuclear waste at West Valley. Dr. Pegg has served as a technical team member on several successful multi‑billion-dollar treatment facility proposals, including the WTP privatization at Hanford and the AMWTP privatization at Idaho. Dr. Pegg directs the Hanford WTP vitrification research and technology support effort at VSL, which supports the design, construction, and operation of what will be the world’s largest nuclear waste vitrification facility. Dr. Pegg also directs similar R&D efforts for the Defense Waste Processing Facility at the Savannah River Site, the Rokkasho vitrification facility at Rokkasho, Japan, and the Sellafield site in the UK. Dr. Pegg has been a frequent participant on expert review teams for the Department of Energy, the National Academies of Sciences, Engineering, and Medicine, the Government Accountability Office, and the International Atomic Energy Agency. He is the Chair of The International Advisory Committee for the UK TRANCEND Programme for waste management technology development, a partnership of eleven UK universities, Sellafield Ltd, the UK National Nuclear Laboratory, and the UK Nuclear Decommissioning Authority. He is the co-founder of three advanced materials and green-tech companies. He has directed Ph.D. research and dissertations in both physics and chemistry. He previously held positions at the National Institute for Standards and Technology and in the Department of Chemistry and Biochemistry at UCLA. He holds a Ph.D. in physical chemistry as well as MBA and B.Sc degrees. Dr. Pegg’s publications include over 250 papers, over 30 patents and patent applications, and over 600 refereed technical reports.

ABSTRACT:

Vitrification is the most widely employed treatment technology for the immobilization of high-level nuclear wastes, which arise from reprocessing of spent nuclear fuel from nuclear reactors employed for power generation and defense programs. However, vitrification has also found extensive applications for the treatment of low- and intermediate-level nuclear wastes as well as non-radioactive hazardous wastes from a range of sources.

This presentation will begin with a brief review of the origins of this waste followed by a discussion of the issues associated with their treatment by vitrification. Examples will be drawn from many projects conducted and ongoing at the Vitreous State Laboratory.

The vitrification process itself is, in principle, relatively simple, involving the mixing of the waste with appropriate chemical additives and processing at high temperature to produce a glass melt that is cooled to yield a dense, durable solid waste form. The evaporation of volatile constituents such as water and the decomposition of salts and organics can lead to considerable volume reductions, which can improve overall economics when volume-based handling and disposal costs are considered.

The basic vitrification concept is also quite flexible, which has led to the development of a variety of vitrification processes that differ in their principle of operation, mode of energy input, melter geometry, scale, and materials of construction. Appropriate glass formulations for vitrification processes must meet a variety of requirements that depend on the composition and nature of the waste, the selected processing technology, and the disposal scenario. These requirements can be translated into a set of property constraints that prospective glass formulations must meet.

Additionally, economic considerations favor glass formulations that have high waste loadings and high melting rates. Key factors can include the leach resistance of the product, melt properties such as viscosity and electrical conductivity, secondary phase formation in the melt (including crystalline phases such as spinels and noble metals or salt phases such as sulfates, molybdates, chromates, and halides, all of which can cause operational issues), materials compatibility (refractories, electrodes, etc.),  melt foaming, and the extent and control of volatilization of species such as technetium, cesium, ruthenium, iodine, etc. These issues will be discussed and vitrification processes will be reviewed with examples from facilities around the world.