Review of Available Data for Validation of Nuresim Two‐Phase CFD Software Applied to CHF Investigations

Abstract

The NURESIM Project of the 6th European Framework Program initiated the development of a new-generation common European Standard Software Platform for nuclear reactor simulation. The thermal-hydraulic subproject aims at improving the understanding and the predictive capabilities of the simulation tools for key two-phase flow thermal-hydraulic processes such as the critical heat flux (CHF). As part of a multi-scale analysis of reactor thermal-hydraulics, a two-phase CFD tool is developed to allow zooming on local processes. Current industrial methods for CHF mainly use the sub-channel analysis and empirical CHF correlations based on large scale experiments having the real geometry of a reactor assembly. Two-phase CFD is used here for understanding some boiling flow processes, for helping new fuel assembly design, and for developing better CHF predictions in both PWR and BWR. This paper presents a review of experimental data which can be used for validation of the two-phase CFD application to CHF investigations. The phenomenology of DNB and Dry-Out are detailed identifying all basic flow processes which require a specific modeling in CFD tool. The resulting modeling program of work is given and the current state-of-the-art of the modeling within the NURESIM project is presented.

Euler‐Euler Large Eddy Simulation of a Square Cross‐Sectional Bubble Column Using the Neptune_CFD Code

“…One of the main goals of the project is the integration of state-of-the-art physical models in a common, open-software platform, including the latest advances in reactor core physics, thermal-hydraulics, and coupled multiphysics modelling capabilities. The objective of the thermal-hydraulic subproject within NURESIM is the improvement of the predictive capabilities of the simulation tools for key two-phase-flow, thermal-hydraulic processes that can occur in nuclear reactors, focusing on two highpriority issues: critical heat flux (CHF) [2] and pressurized thermal shock (PTS) [3]. As a part of this activity, the Paul Scherrer Institute is investigating the potential of the EELES approach for simulating bubbly flows, which are important for understanding CHF and PTS, using the Neptune CFD code [4], the CFD component of the NURESIM platform.…”

NEPTUNE_CFD Analysis of Flow Field in Rectangular Boiling Channel

“…Detailed description of mesurment technique and procedure is given in [1]. These measurements contribute to the existing database of boiling flow measurements that can be used for validation and testing of three-dimensional multiphase models [4]. An important advantage of considered experimental data is that they provide useful information on flow behaviour close to the wall including experimentally determined shear velocity.…”

Sensitivity study of momentum and turbulence models for subcooled boiling phenomena simulation

“…The study and the application of the here called sub-models, designating the models of terms applied in the governing equations of the CMFD approach, may give more information about the mechanisms involved, leading to better mechanistic models, and allowing more efficient operation in nuclear power systems. Studying this choice, Bestion et al [8] and Yadigaroglu [9] review CMFD capabilities and point out some challenges that must be solved to achieve representative simulations of the CHF.…”