Assessing Inventories of Past Radioactive Waste Arisings at Chalk River Laboratories

Abstract

Internationally, a great deal of progress has been made in improving the management of currently accumulating and anticipated future radioactive wastes. Progress includes improved waste collection. segregation, characterization and documentation in support of disposal facility licensing and operation. These improvements are not often very helpful for assessing the hazards of wastes collected prior to their implementation, since, internationally, historic radioactive wastes were not managed and documented according to today's methods. This paper provides an overview of Atomic Energy of Canada Limited's (AECL) unique approach to managing its currently accumulating. low-level radioactive wastes at Chalk River Laboratories (CRL) and it describes the novel method AECL-CRL has developed to assess its historic radioactive wastes. Instead of estimating the characteristics of current radioactive wastes on a package-by-package basis, process knowledge is used to infer the average characteristics of most wastes. This approach defers, and potentially avoids, the use of expensive analytical technologies to characterize wastes until a reasonable certainty is gained about their ultimate disposition (Canada does not yet have a licensed radioactive waste disposal facility). Once the ultimate disposition is decided, performance assessments determine if inference characterization is adequate or if additional characterization is required. This process should result in significant cost savings to AECL since expensive, resource-intensive, up-front characterization may not be required for low-impact wastes. In addition, as technological improvements take place. the unit cost of characterization usually declines, making it less expensive to perform any additional characterization for current radioactive wastes. The WIP-III data management system is used at CRL to "warehouse" the average characteristics of current radioactive wastes. This paper describes how this "warehouse of information" is used to support the management of currently accumulating radioactive wastes and how this same "warehouse of information" is the basis for the development of a novel way to assess historic waste inventories. Records of waste emplaced into storage facilities at CRL since the mid 1940's are in a variety of formats and the quality of the data recorded is inconsistent. In addition, prior to recent improvements in waste management, wastes that should have been collected and handled separately (short-lived versus long-lived) were usually handled and stored together on the basis of external radiation field - not on their requirements for long-term management. As such, the challenge is to assess historic waste management records in the context of today's waste management practices. Recent enhancements to the WIP-IU application have provided the tools for this assessment. Historic records are entered into WIP-III "as-is". Next, using additional data entry screens, expert interpretation is used to identify historic wastes as similar to a current waste or similar to a mixture of current wastes. Next, the historic waste is assigned the characteristics of a current waste or of a mixture of current wastes, using the "warehouse of information". The interpretation process improves the quality of historic waste inventory records, which will allow AECL-CRL to provide defensible estimates of the characteristics of its historic wastes. This paper describes how the interpretation process can be generically applied to any waste site with historic wastes, independently of how those sites manage their current wastes.