P. Vigni

Scaling of natural circulation in PWR systems

Abstract This paper deals with the problem of scaling complex thermalhydraulic scenarios measured in experimental facilities which simulate Pressurized Water Reactor systems. Phenomena occurring during different phases of natural circulation between the core and the steam generators are considered. The experimental data obtained in some integral test facilities were analyzed with a large system code and for this purpose a simple model was built. The code predicted scenario and the extrapolated one for the actual plant are compared.

Assessment of Scaling Principles for the Simulation of Small Break LOCA Experiments in PWRs

Abstract The choice of the scaling laws to be applied for the simulation of nuclear reactor behaviour and, more particularly, the extrapolation of data measured in experimental facilities to real plants, remains an important unresolved issue in nuclear safety. After the analysis of scaling principles adopted in the design of four PWR simulators, the above problem is dealt with in this paper. The definition of a counterpart test and a code analysis, comparing LOFT measured data with calculated trends in the PWR-PUN plant and in LOBI/MODI, LOBI/MOD2 and SEMISCALE facilities, make it possible to check the validity of the criteria utilized in the design of the experimental loops and to reduce uncertainty margins in predicting PWR behaviour.