CSNI status report “3D capabilities of thermalhydraulic system codes”: Lessons learned

Abstract

In September 2015, an activity was endorsed by the OECD/CSNI/WGAMA to prepare a state of the art report presenting the 3D features of current thermal–hydraulic system codes. This activity was coordinated by IRSN and started in April 2016. This document is a synthesis of the full OECD report which is expected by 2023.Multi-dimensional phenomena that may have an important impact on the current thermalhydraulic models occur in the course of asymmetric scenarios such as feed water line break, main steam line break and loss of coolant accident. Most physical models were first established and validated in 1D geometry. The growing role of 3D modelling of reactor core and pressure vessel requires additional experimental data for a proper validation. Elements on available experimental support are proposed. However, the need of additional experimental support for validation has been identified in several directions such as the friction pressure losses, the diffusion–dispersion of momentum and energy dependency with space averaging, passive systems and the dispersion of void in core and downcomer. There are also several axes for progress, namely the development of phenomena identification and their ranking, the terms in the field equations and the mesh size dependence and the time step strategy.