Code validation and model qualification for problems of mixing and thermal exchange in innovative reactors

The main objective of this work is to present the results obtained in the last campaign of experimental tests performed at the DIMNP (Department of Mechanical, Nuclear and Production) of the University of Pisa with a stainless steel mock-up, simulating the downcomer and lower plenum of a small scale PWR (Pressurized Water Reactor), in order to provide relevant data to study the mixing phenomena occurring during a DVI line break accident (SB-LOCA) and to validate commercial CFD codes. These new tests are characterized by a cold water injection inside the downcomer from both the DVI lines. The first part of this report is devoted to a brief recall of the description of experimental apparatus, hydraulic circuit and data acquisition system. The second and most important part of the report is devoted to the description of the newly performed experimental tests. The third part of the work is focused on numerical simulations, performed using the Fluent CFD code, and the main improvements introduced to the computational domain, in particular with regard to geometry and spatial discretization. The final part concerns a critical analysis of the comparison between experimental and computational data.