Two-phase CFD advances in the NURESIM and NURISP projects

NURESIM and NURISP are two successive European Projects of the 6th and 7th Framework Program with the objective of building a multi-physics and multi-scale platform for numerical simulation of nuclear reactors. It includes core physics and thermalhydraulics with sensitivity and uncertainty methods and coupling of thermalhydraulics with fuel thermomechanics and neutron kinetics. The NURISP European Collaborative Project (FP7) includes 22 organizations from 14 European countries.
This paper summarizes some achievements and ongoing developments of the platform in Thermal-Hydraulics. Within the NURESIM project the development and validation of two-phase-CFD in open medium addressed mainly Departure from Nucleate Boiling, Dry-Out, Direct Contact Condensation and Pressurized Thermal Shock. Within NURISP, CFD use is now extended to some investigations related to LOCA such as flashing flow, and steam-droplet flow in a core during reflooding. The NEPTUNE-CFD code developed by EDF and CEA and sponsored by AREVA-NP and IRSN was first implemented in the NURESIM platform and The TRansaT code developed by ASCOMP is now also in the platform. New physical models have been developed, validation calculations were performed and NEPTUNE-CFD was benchmarked with commercial codes. DNS–ITM techniques (e.g. Lattice Boltzman Method or DNS of the TransAT code) were also used as numerical experiments to obtain information on smaller scale flow processes.
The paper summarizes the achievements, updates the state of the art in two-phase-CFD, and presents the future activities