To perform fracture mechanics analysis of reactor vessel, fracture toughness (KIc) at various temperatures would be necessary. In a best estimate approach, KIc uncertainties resulting from both lack of sufficient knowledge and randomness in some of the variables of KIc must be characterized. Although it may be argued that there is only one type of uncertainty, which is lack of perfect knowledge about the subject under study, as a matter of practice KIc uncertainties can be divided into two types: aleatory and epistemic. Aleatory uncertainty is related to uncertainty that is very difficult to reduce, if not impossible; epistemic uncertainty, on the other hand, can be practically reduced. Distinction between aleatory and epistemic uncertainties facilitates decision-making under uncertainty and allows for proper propagation of uncertainties in the computation process. Typically, epistemic uncertainties representing, for example, parameters of a model are sampled (to generate a “snapshot,” single-value of the parameters), but the totality of aleatory uncertainties is carried through the calculation as available. In this paper a description of an approach to account for these two types of uncertainties associated with KIc has been provided.
- Nuclear Engineering Division
Uncertainty Characterization of Reactor Vessel Fracture Toughness
Li, F, & Modarres, M. "Uncertainty Characterization of Reactor Vessel Fracture Toughness." Proceedings of the 10th International Conference on Nuclear Engineering. 10th International Conference on Nuclear Engineering, Volume 2. Arlington, Virginia, USA. April 14–18, 2002. pp. 423-429. ASME. https://doi.org/10.1115/ICONE10-22647
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