Page 372 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Core thermal hydraulics 335

The interaction of the turbulent flow with the fuel pins might lead to flow-induced vibrations
l
in a fuel assembly. In the specific case of liquid-metal fuel assembly simulations, a coupling
algorithm is needed that can deal with strongly coupled fluid-structure interaction problems
as the density ratio between structure and coolant is close to or even less than unity. On top of
that, the method should be able to deal with the complex geometry of the fuel assembly
involving the wire wrap.
l For the assessment of nuclear safety, not only the normal operational conditions should be
analyzed but also the behavior of the nuclear system in accident conditions. For LMFR ther-
mal hydraulics, two important topics to this respect include the analysis of the effects and
formation of blockages on the one hand and the contribution of the interwrapper flow coolant
bypass to the local cooling in the core and to avoid damage propagation.
l In LBE-cooled reactors, the oxygen distribution and range are of major importance to control
the corrosion in the core. CFD in combination with chemical reaction simulation can indicate
the measures to maintain a stable protective oxide layer at the steel/LBE interface
l Never forget that experiments and simulations go hand in hand. Simulations support exper-
iment preparation, design, and instrumentation. Experiments support reactor design, safety
cases, and validation of simulation methods. And finally, simulations support interpretation
of experiments, reactor design, and safety analyses. Moreover, CFD numerical models, val-
idated on small-scale experimental test sections, can then be applied to real-scale geometries
and conditions

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