• NUCLEAR
• SCALING
• SPES3
• IRIS

The present work is the result of a six months internship spent at Westinghouse Electric Company (WEC), Science and Technology Department, Pittsburgh (Pennsylvania, USA). In this work, the Fractional Scaling Analysis (FSA) methodology was applied to the IRIS reactor and SPES3 facility water level response during the design reference DVI-break accident.
The DVI-break represents the more limiting condition from the point of view of core cooling due to the proximity of the break to the core. The water inventory in the reactor vessels must be always sufficient in order to assure the core cooling. For this reason, the scaling analysis of the water collapsed level in the Reactor Pressurized Vessel (RPV) (strictly related to the water inventory in the RPV during the accident) was conducted.
The FSA methodology, in a time dependent approach, is presented and applied. This type of scaling analysis was selected because its application makes possible to clearly identify the most important phenomena driving the transient of the selected variable (in this case the overall void fraction in the RPV) and also to evaluate the distortions between the compared facilities.
As a result of the FSA applied to the selected transient, by comparing IRIS and SPES3 Fractional Rates of Change (FRC) the driving phenomena were identified and, by comparing the Effect Metrics, some important distortions were found and numerically quantified. Some possible explanations for these distortions were proposed and the results of the analysis are now used by WEC and SIET as a feedback on SPES3 design in order to have a better simulation of IRIS.