Post-test simulations for the NACIE-UP benchmark by STH codes

This paper illustrates the results obtained in the last phase of the NACIE-UP benchmark activity foreseen inside the EU SESAME Project. The purpose of this research activity, performed by system thermal–hydraulic (STH) codes, is finalized to the improvement, development and validation of existing STH codes for Heavy Liquid Metal (HLM) systems. All the participants improved their modelling of the NACIE-UP facility, respect to the initial blind simulation phase, adopting the actual experimental boundary conditions and reducing as much as possible sources of uncertainty in their numerical model. Four different STH codes were employed by the participants to the benchmark to model the NACIE-UP facility, namely: CATHARE for ENEA, ATHLET for GRS, RELAP5-3D© for the “Sapienza” University of Rome and RELAP5/Mod3.3(modified) for the University of Pisa. Three reference tests foreseen in the NACIE-UP benchmark and carried out at ENEA Brasimone Research Centre were analysed from four participants. The data from the post-test analyses, performed independently by the participant using different STH codes, were compared together and with the available experimental results and critically discussed

TALL-3D open and blind benchmark on natural circulation instability

International audienceDesign 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

Post-test simulations for the NACIE-UP benchmark by STH codes

This paper illustrates the results obtained in the last phase of the NACIE-UP benchmark activity foreseen inside the EU SESAME Project. The purpose of this research activity, performed by system thermal-hydraulic (STH) codes, is finalized to the improvement, development and validation of existing STH codes for Heavy Liquid Metal (HLM) systems. All the participants improved their modelling of the NACIE-UP facility, respect to the initial blind simulation phase, adopting the actual experimental boundary conditions and reducing as much as possible sources of uncertainty in their numerical model. Four different STH codes were employed by the participants to the benchmark to model the NACIE-UP facility, namely: CATHARE for ENEA, ATHLET for GRS, RELAP5-3D (c) for the "Sapienza" University of Rome and RELAP5/Mod3.3(modified) for the University of Pisa. Three reference tests foreseen in the NACIE-UP benchmark and carried out at ENEA Brasimone Research Centre were analysed from four participants.The data from the post-test analyses, performed independently by the participant using different STH codes, were compared together and with the available experimental results and critically discussed

Extension and application on a pool-type test facility of a system thermal-hydraulic/CFD coupling method for transient flow analyses

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Assessment of systems codes and their coupling with CFD codes in thermal-hydraulic applications to innovative reactors

International audienceThe 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. © 2014 Elsevier B.V. All rights reserved