Trends and needs in experimentation and numerical simulation for LWR safety

A benchmark exercise on the use of CFD codes for containment issues using best practice guidelines: A computational challenge

“…The OECD-SETH experimental programme [4] includes various types of tests, where the distribution of gases within the two Drywells is controlled by the horizontal or vertical injections of steam or steam/helium mixtures in one vessel. Most tests are performed with a constant pressure boundary condition, prescribing the pressure at the outlet (vent), and under conditions for which no condensation is expected: a moderately superheated gas is injected in an ambient where both gas and walls are at a temperature slightly above the saturation temperature at the prescribed pressure.…”

“…To this aim, the assessment must use separate-effect test data collected in facilities where the 3-D distribution of the relevant variables is measured with sufficient resolution and accuracy, and tests are performed under well controlled initial and boundary conditions. Tests that have been especially designed to provide the adequate database for this basic assessment are carried out in the PANDA facility [3], within the OECD SETH project [4]. This paper mostly addresses the structure of the benchmark exercise and the computational challenge posed by the problem investigated, whereas limited comparison of the simulations with the experimental results (not discussed here) is only presented to provide a first estimation of the accuracy that can be achieved in the simulation of basic flows with the presently available computer power.…”

CFD4NRS with a focus on experimental and CMFD investigations of bubbly flows

“…In a typical two-phase flow example, bubbly flow, one has at least three length scales: the scale of the equipment, the scale of the bubble and the fine scale of turbulence. Such multi-phase problems should also be tackled with computations, methods and tools appropriate at a multiplicity of time/space scales as we [13,14], as well as other authors [12,15], have already noted in previous publications. Let us refer to these as the micro-, the meso-and the macro-scale.…”

Toward a CFD-grade database addressing LWR containment phenomena

“…An important aspect of the new experiments that has also been emphasized is the need to obtain data on large-scale tests to reduce the impact of scaling distortions in the assessment of the code models. These and other aspects of the current development of the new computational tools for reactor safety have been addressed by Yadigaroglu et al (2003). Gas transport and mixing in the containment are considered high ranking phenomena which concern nuclear safety (Smith, 2009).…”