Numerical Study of the Steady-State Subchannel Test-Case with NEPTUNE_CFD for the OECDNRC NUPEC PSBT Benchmark

Abstract EN

The multifield computational fluid dynamics (CFD) code NEPTUNE_CFD is applied to carry out a numerical study of the steady-state subchannel test-case of the OECD/NRC NUPEC PWR subchannel and bundle tests (PSBTs) international benchmark, focusing on the simulation of a subset of five selected experimental runs of the centered subchannel configuration.

First, using a standard choice for the physical models and a constant, predetermined bubble diameter, the calculated void fraction is compared to experimental data.

Besides, the mesh sensitivity of the calculated void fraction is investigated by performing simulations of three grid levels, and the propagation of the experimental uncertainties on the input parameters of the simulations is also studied.

Last, calculation results with devoted models for the bubble-size distribution are analyzed.

Their impact is visible on the subcooled run, giving void fraction closer to experiments than those obtained with a fixed bubble-size.

Void-fraction distribution with bubble-size models is also shown to come closer to experiment for another run with a higher equilibrium quality.