Metallic Low-Level Waste (LLW) Handling Options: An Optimal Life cycle-Based Approach for North American Operations - 19413
Daily activities associated with nuclear power plant operations produce large volumes of low-level contaminated waste. During operation, a small percentage of this low-level waste is metallic (< 1% by volume). However, this figure increases materially when a facility is finally decommissioned, with approximately 1000 m{sup 3} of contaminated metal waste generated for every 1 GW decommissioned (13% by volume). With global nuclear decommissioning efforts expected to increase until 2050, the amount of low-level metallic waste generated is expected to increase the global inventory by over an order of magnitude. The high cost of conventional surface storage and burial of radioactive metal, coupled with the projected increase in low-level metallic waste volumes provides strong incentive to identify cost-effective waste management solutions. Surface decontamination and thermal methods are proven options for decontaminating low-level metallic waste. Surface decontamination processes include chemical, electrochemical, or mechanical methods, which are used to remove contamination from exposed layers of metal. Surface decontamination is most effective when metal has low levels of activity localized on the outer layers. When the activity is more uniformly distributed in the metal (or the geometry is complex), alternative methods such as thermal decontamination are required. In the thermal decontamination process, contaminated scrap metal is melted in a furnace and held in a molten state for a period of time while the radioactive material is separated out through gravity. Radioactive material reports to slag which is handled separately, or to the exhaust which is handled using conventional gas handling technologies. Thermal methods of decontamination involving metal melting present an opportunity to reduce long-term storage cost with a reduction in waste volume, along with the opportunity to reuse the decontaminated metal. Methods for dealing with metallic low-level waste from nuclear facilities vary extensively across the globe. The approach employed at any given site may be set by a host of factors ranging from regulatory influence, public perception, local economics, available geology for underground storage and often, precedent established long ago by early operations. This paper examines several low-level metallic waste handling options including techniques for surface decontamination and metal melting, as well as a combination of both. The various methods are categorized according to their suitability for waste characterization and local/global installations. The effectiveness of each option is benchmarked against a range of criteria, including capital and operating costs, environmental impact, overall sustainability and risk management issues. The overall objective of this paper is to develop a methodology for determining the most beneficial low-level metallic waste management strategy for a facility once the quantity, type and nature of the waste is established on a long-term basis. It is the authors' hope that the methodology can be used as a tool to test a facility's current plans (which are primarily focused on long-term storage) and identify areas for optimization with an emphasis on overall cost and environmental footprint reduction. The trend towards long term planning to handle large amounts of contaminated metal, along with obtaining a social license to implement a sustainable waste management solution, are key decision-making variables that will be discussed in relation to the LLW handling options presented in this paper. (authors)