Development and assessment of a method for evaluating uncertainty of input parameters

摘要

Best-estimate plus Uncertainty Evaluation methods are gaining increased interest in the licensing process. Besides, lessons learnt from the OECD/NEA BEMUSE benchmark and other projects show that improvements of the present methods are necessary. In particular, methods to properly estimate input parameter uncertainties need to be developed and assessed. An Input Parameter Range Evaluation Methodology (IPREM) has been proposed and developed at University of Pisa for the quantification of the variation ranges of the input parameters through comparison of sensitivity calculations results of a selected system thermal-hydraulic code with experimental data, utilizing the mathematical apparatus of the FFTBM (Fast Fourier Transform Based Method). Within the framework of OECD/NEA PREMIUM benchmark, IPREM has been applied to the quantification of the uncertainty of the RELAP5 code models related to the simulation of reflood phenomena.