• pressure response
• scaling
• uncertainty
• SPES3
• CSAU

The present work was made in support to the development of a new approach for the scaling analysis of the IRIS reactor and the SPES3 facility, required by the Westinghouse team for future studies. The relevant features of the IRIS reactor are described and in particular, the main characteristics of this new nuclear plant are pointed out. Two methodologies for performing a scaling analysis of downscaled facilities are described: the Fractional Scaling Analysis (FSA) and the Hierarchical Two Tiered Scaling (H2TS). Differences and analogies of these two approaches are emphasized. Problems related to evaluation of uncertainty in code calculations are presented and different approaches to solve the problem are examined.
An in-house code has been developed to predict the behaviour of the pressure response in a system during a transient, basing as far as possible on experimental data. All contributions to mass and energy transfers are taken into account and, in particular, isentropic compressibility coefficients have been carefully estimated. As a first application of the code, the LOFT L2-5 test has been considered. Problems related to the interpretation of experimental data are highlighted for future developments.
A good agreement was obtained between the experimental data and the calculated results. Finally, basing on data derived from previous calculations, the scaling analysis of LOFT L2-5 has been performed following the Fractional Scaling Analysis (FSA).This work represents the basis for the future approach to the scaling analysis for the IRIS reactor and the SPES3 facility.