Nuclear Technology / Volume 126 / Number 3 / June 1999 / Pages 303-318
Technical Paper / Radioactive Waste Management and Disposal
An assessment for the criticality safety of a conceptual repository for vitrified high-level radioactive waste from reprocessed fuel of commercial light water reactors in a water-saturated granitic rock has been performed by quantitatively estimating the mass of fissile 235U existing in the entire far field as the performance measure. The uncertainties associated with the performance measure have been obtained by a statistical analysis with the Latin hypercube sampling method.
With the assumed probability distribution functions for the model parameters, the mass of 235U released from the repository and existing in the far field at 100 million years is estimated to be <40 kg with a 90% confidence level. This implies that all 235U existing in the entire far field at that time must accumulate in a single location for an overmoderated criticality event to occur in granitic rock.