A tool for quantitative assessment of code calculations with an improved fast Fourier transform based method

The assessment process of large thermal-hydraulic computer codes aims at verifying their quality by comparing code predictions against experimental data gained by tests performed on scaled facilities. In the field of nuclear engineering only a few methods for quantitative assessment have been proposed. The objective of the study was to develop a Microsoft Excel add-in for accuracy evaluation of thermal-hydraulic code calculations with an improved fast Fourier transform based method (FFTBM). For developing an add-in Microsoft Visual Basic 6.0 was used. The existing FFTBM was used and improved by proposing two new accuracy measures, minimal variable accuracy and a number of discrepancies for the calculation. For validation of the improved FFTBM program the IAEA-SPE-4 experimental and calculated data were used. In the case of original accuracy measures code to code validation was done. New accuracy measures were compared to the qualitative analysis and it was shown that they contribute to a more complete picture of the thermal-hydraulic code calculation accuracy. In general, the developed FFTBM add-in proved to have several advantages compared to the original Fortran code, therefore it could be extensively used for a quantitative assessment of thermal-hydraulic code calculations.