Nuclear waste repository performance assessment

Grambow, B. 1991. What do we know about nuclear waste glass performance in the repository near field In Sellin, P., Apted, M. Gago, J. (eds) Proceedings Technical Workshop on Near-Field Performance Assessment for High-Level Wastes, Madrid, Spain. SKB Technical Report 91-59. Stockholm, Sweden, 25-49. 

Currently proposed licensing regulations for geologic nuclear waste repositories require a performance assessment involving long-term predictive capabilities. Previous work (J- 5) has shown the importance of solubility controls for modeling maximum actinide concentrations in repository groundwaters. However, until reliable data are available on the actinide solid phases that may be present or that may precipitate in the environment, the solubility of solid phases such as hydrous oxides that have fast precipitation kinetics can be used to initially set maximum solution concentration limits. 

It has been the underlying theme of this paper that the theoretical approach to solubility and speciation of key radionuclides adopted here can be helpful in identifying the general types of species likely to be dominant in aqueous solutions. At present, these estimates are useful in identifying those radionuclides that require special attention in repository performance assessment studies. However, sophisticated experimental studies are necessary to provide important confirmatory data for nuclides of critical importance to the safe isolation of nuclear waste in a repository in basalt. 

Geochemical modeling has also been widely used in performance assessment of high-level nuclear waste repositories in other countries, with which we are not as familiar. Therefore, our book has a strong bias toward using examples in the USA. 

Despite the secondary role of waste forms, as determined by total system performance assessments of nuclear waste repositories, there are logical and compelling reasons for emphasizing the importance of the material properties of the waste form (Ewing 1992) ... 

To study the application of THM modeling to performance and safety assessment of nuclear waste repositories. 

Natural systems that may be analogous in certain respects to a geologic repository for nuclear wastes provide a useful basis for testing assumptions, models and concepts used in repository performance assessments. The present study demonstrates that maximum U concentrations in groundwaters of the Tono Uranium Deposit appear to be limited by the solubility of the amorphous, hydrous oxide, U02(am). This conclusion, drawn from observations of a geologic system that has evolved over long periods of time, supports the... 

Banwart, S. (ed.) 1995. The Aspo Redox Investigations in Block Scale. Project Summary and Implications for Repository Performance Assessment. Technical Report 95-26. The Swedish Nuclear Fuel and Waste Management Co., Stockholm. 

The performance of a geological repository for nuclear waste is influenced by many processes. Determination of whether the total system will comply with regulatory requirements necessitates consideration of all components of the systems and the effects of linking all the components together. This linkage is important because it allows each component to be viewed in the context of the behavior of the entire system. Hence, the concept and methodology of Total System Performance Assessment (TSPA) is widely used in nuclear waste disposal (Figure 2.2). 

Geological evidence has indicated that mid- to high-latitude locations in the Northern Hemisphere have experienced glaciation/deglaciation cycles in recent geological history. These cycles are likely to recur in the future within a time frame of several hundred thousand years and have to be considered in performance assessments of deep geological repositories of long lived nuclear wastes. 

The data from field studies is largely confirmed by the performance assessments of proposed nuclear waste r sitories. The intrusion scenario is calculated to have a lower risk than the undisturbed natural leach and migration scenario. The latter qualitatively agrees with the Oklo data and indicates no unacceptable risks result from a carefully chosen and designed geologic repository in which the nuclear wastes are enq>laced with appropriate packaging. 

Wescott, R.G, M.P. Lee, N.A. Eisenberg, andT.J. McCartin. 1995. NRC iterative performance assessment Phase 2 Development of capabilities for review of a performance assessment for a high-level waste repository. NUREG-1464. U.S. Nuclear Regulatory Commission, Washington, DC. 

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