Natural Analogs and Performance Assessment for Geologic Disposal of Nuclear Waste
- PDF / 1,069,830 Bytes
- 12 Pages / 418.68 x 637.2 pts Page_size
- 49 Downloads / 226 Views
ABSTRACT The use of natural analog studies in performance assessments has been widely discussed and debated, but its accomplishment has been limited. Given recognized uncertainties and challenges, scientific contributions to performance assessments and support for the validity of performance assessment models are valuable from all possible sources, including natural analog studies. The conceptual basis for geologic disposal of nuclear waste and for performance assessments relies on scientific expertise based largely on studies of natural systems analogous to possible repository systems, i.e., natural analogs. Natural analog studies offer contributions to model validation based both on inductive and deductive reasoning. The utility of analog studies as a deductive tool in performance assessment is enhanced by specificity of the analog system to the repository system. As geologic sites are selected and repository designs detailed, the use of analog data in supporting deductive performance assessments should increase. Consideration of Yucca Mountain for the proposed US high level nuclear waste repository affords site specificity conducive to applications of natural analog data in performance assessment. The primary use of Pefia Blanca natural analog data in recent Yucca Mountain performance assessments stems from observations of mineral products formed by alteration of natural uraninite, an analog of spent fuel. Alternate performance assessment source term models based on the Pefia Blanca oxidation rate model and the schoepite solubility model yield lower, yet comparable estimated doses than the base case model in the NRC performance assessment for Yucca Mountain. INTRODUCTION The use of natural analog studies in performance assessments has been widely discussed and debated, but its accomplishment has been limited. The object of this paper is to illustrate how natural analog contributions to performance assessments advance the scientific basis for nuclear waste management. Natural analog studies for nuclear waste disposal focus on numerous scientific issues, including the properties of natural materials as analogs of waste forms [ 1-7], the properties, longevity, and isolation of archaeological materials and their alteration products [8-101, alteration of repository host rocks due to potential hydrothermal effects or interactions with engineered materials [11-13], speciation and geochemical transport phenomena in geologic media [ 14-17], and the probability and consequences of volcanic activity [ 18]. In principle, analog studies can be used to develop conceptual models, provide or confirm parameters and functional relations used in models, test model assumptions, evaluate predictive capabilities, and define uncertainties in predictions for performance assessments. Performance assessment is a safety assessment and management methodology used in the context of nuclear waste disposal (e.g., [19]). Various approaches to performance assessment have been taken, e.g., deterministic vs. probabilistic modeling, generic vs. sp
Data Loading...
