The Role of the Engineered Barrier System in Safety Cases for Geological Radioactive Waste Repositories: An NEA Initiative in Co-operation with the EC

Abstract

Radioactive waste derives from all phases of the nuclear fuel cycle and from the use of radioactive materials in industrial, medical, military and research applications; all such wastes must be managed safely. The most hazardous and long-lived wastes, such as spent nuclear fuel and waste from nuclear fuel reprocessing, must be contained and isolated from humans and the environment for many thousands of years. Many Nuclear Energy Agency (NEA) member countries are, therefore, researching plans for the management of long-lived radioactive waste in engineered facilities, or repositories, located deep underground in suitable geological formations.

Environmental Degradation of Engineered Barrier Materials in Nuclear Waste Repositories

“…The degradation mechanisms that need to be studied include corrosion, microbial activity, and radiation damage. Table 36.1 shows that, except for the United States, most of the recommended materials for the containers will be carbon steel, stainless steel, or copper [2,4]. Since for most of the nations the environment is rather benign or controlled, the alloys selected for the containers are not in the high end of the scale of the corrosion-resistant alloys.…”

“…The secondary barriers may include a drip shield such as in the U.S. design or backfilling with bentonite such as in the Canadian and other designs (Table 36.1) [2,3]. A discussion in detail of the characteristics and significance of the engineered barrier systems in all the planned repositories is given by Bennett et al [4] More than 30 nations are currently considering the geologic disposal of HLW [3][4][5][6]. A short list of these nations is in Table 36.1.…”

“…The predicted maximum temperature for waste packages emplaced in a consolidated volcanic ash (tuff) formation in the United States is not expected to be higher than 160-200 C [9]. Typical maximum container temperatures for a number of other repository locations are expected to be lower than 100 C [3,4].…”

The Role of the Engineered Barrier System in Safety Cases for Geological Radioactive Waste Repoitories: An NEA Initiaive in Co-Operations with the EC, Process Issues and Modeling

“…The project also seeks to clarify the role that the EBS plays in assuring the overall safety of a repository [3,41. A framework for the EBS Project is provided by a series of workshops that allow discussion of the wide range of activities necessary for the design, assessment and optimisation of the EBS, and the integration of this information into the safety case. The topics of this series of workshops have been planned so that the EBS project will work progressively through~the main aspects comprising one cycle of the design and optimisation process [4], [ 5 ] , [6] (Fig.1).…”

Interactions between C-steel and blended-cement in concrete under radwaste repository conditions at 80 °C

“…The EBS itself comprises a variety of sub-systems, such as the waste form (radioactive material immobilized in a host material), a corrosion resistant and mechanically stable container, a buffer/sealing system, and plugs. The EBS must be designed so that it will work with the natural barriers to meet the regulatory limits [3,4]. The vitri ed HLW form in a steel canister is speci cally designed for long term durability in storage and disposal [5,6].…”