The UMAE methodology for evaluating the uncertainty in the prediction of thermal-hydraulic phenomena in nuclear reactors

Uncertainty Methodology from Accuracy Extrapolation (UMAE) methodology is overviewed and critically evaluated. For its application, a thermal-hydraulic system code and a nuclear power plant related set of data is needed. Basic features of an uncertainty analysis are the characterization of relevant input parameters (input uncertainty) and the global influence of the combination of these uncertainties on selected output parameters (output uncertainty). The relationship between input and output uncertainties is constituted by scaling effects and related treatment by the different methods. The approach adopted by UMAEA is presented that is based on experimental and calculated data. (N.T.). 6 refs