In the framework of the validation of the TrioCFD code for mixed convection and steady-state sodium flows, four experiments obtained using the SUPERCAVNA experimental equipment and involving Richardson numbers ranging from 0.13 to 4.21 are simulated. The TrioCFD numerical tool uses a RANS approach with a k - SMALL ELEMENT OF turbulence model including a buoyancy term and the computed results are in very good agreement with the experiments.

Design and safety analysis of the currently developed pool type liquid metal cooled fast nuclear reactors is currently impaired by limited operational experience for such systems and insufficient confidence in the predictive capabilities of the applied modelling. Understanding of pool-reactor thermal-hydraulics is crucial for assessment of reactor performance and passive safety systems reliability. Credibility of the analysis tools can be established in the process of code validation, which includes open and blind benchmarks against integral experiments. TALL-3D is a lead-bismuth eutectic (LBE) loop built to provide experimental data for validation of standalone and coupled system thermal-hydraulics (STH) and computational fluid dynamics (CFD) codes. This paper summarizes the results of the open and blind benchmark exercise, performed using experimental data on natural circulation instability in liquid metal flows from the TALL-3D facility. An approach for selection of experimental data for benchmark and tests for model input calibration is presented. A list of parameters, initial and boundary conditions are defined based on modelling limitations and sources of experimental uncertainty. A set of requirements and assessment criteria for the blind calculations were specified. Results of simulations are compared to experimental data. Implications of the benchmark test results for the codes validity and lessons learned are reported.

In this chapter, an overview of the verification, validation, and uncertainty quantification process is offered. First, the context of the dialog with the safety authorities is explained, and the need for a thorough code validation procedure able to meet the regulatory safety requirements is highlighted. Then, the concept of code verification is introduced, and the main steps are described. The validation process is depicted next. Emphasis is made upon the identification of the physical phenomena of interest and upon the choice of adequate computational tools to capture them. The targeted validity domain of these computational tools and its dependence on available and accurate experimental data are detailed with respect to the issue of scaling. Finally, an overview of selected techniques for uncertainty and sensitivity analysis is provided.

The THINS project of the 7th Framework EU Program on nuclear fission safety is devoted to the investigation of crosscutting thermal hydraulic issues for innovative nuclear systems. A significant effort in the project has been dedicated to the qualification and validation of system codes currently employed in thermal hydraulic transient analysis for nuclear reactors. This assessment is based either on already available experimental data, or on the data provided by test campaigns carried out in the frame of THINS project activities. Data provided by TALL and CIRCE facilities were used in the assessment of system codes for HLM reactors, while the PHENIX ultimate natural circulation test was used as reference for a benchmark exercise among system codes for sodium-cooled reactor applications. In addition, a promising grid-free pool model based on proper orthogonal decomposition is proposed to overcome the limits shown by the thermal hydraulic system codes in the simulation of pool-type systems.Furthermore, multi-scale system-CFD solutions have been developed and validated for innovative nuclear system applications. For this purpose, data from the PHENIX experiments have been used, and data are provided by the tests conducted with new configuration of the TALL-3D facility, which accommodates a 3D test section within the primary circuit. The TALL-3D measurements are currently used for the validation of the coupling between system and CFD codes. (C) 2014 Elsevier BM. All rights reserved.