Long-term behaviour of engineered barriers used in surface disposal. 1. Safety functions and treatment of uncertainty

Repository safety assessment (SA) requires defensible assumptions about the future state of engineered barriers (EB). In this study, a reference scenario is presented that describes the gradual EB degradation by means of a step function. To address uncertainties about the assumptions of the future EB state used in the reference scenario, 'what-if' scenarios were developed. The analysis of long-term EB performance also included calculations with two different conceptual models characterized by homogeneous or heterogeneous flow. Finally, consequence analysis were done with best estimate parameter values but also with variations of parameters according to specific distribution functions. (author)