Page 74 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Rod bundle and pool-type 3.1

experiments in water serving
liquid metal reactors

†
†
M. Rohde*, P. Planquart , C. Spaccapaniccia , F. Bertocchi*
*Department of Radiation Science and Technology, Delft University of Technology, Delft,
†
The Netherlands, Environmental and Applied Fluid Dynamics Department, von Karman
Institute for Fluid Dynamics, Sint-Genesius-Rode, Belgium

3.1.1 Introduction

Thermal-hydraulic experiments for liquid metal reactors (LMRs) usually are com-
plex and labor-intensive and, as a consequence, rather expensive. Moreover, liquid
metals (LMs) are completely opaque to visible light, excluding the possibility to
visualize certain phenomena (such as boiling) and to use optical measurement
techniques.
In this respect, water-based facilities can be used to replace flow experiments
with LMs. Water is transparent, liquid at ambient temperature and pressure, non-
toxic, and available practically everywhere. Equipment for water (e.g., pumps, pip-
ing, sensors) is relatively cheap, especially under the aforementioned conditions.
The flow can be measured rather accurately (spatially as well as temporally)
and nonintrusively at the same time with the help of optical techniques such as
laser Doppler anemometry (LDA), particle image velocimetry (PIV), and particle
tracking velocimetry (PTV).
As long as isothermal flows are considered, water-based facilities are perfect for
mimicking the flow in LM experiments, because the only dimensionless number that
requires scaling is the Reynolds number. Phenomena, such as turbulence, secondary
flows, and flow pulsations, can be accurately studied. If natural convection comes into
play; however, water-based facilities are less suitable because of the very low Prandtl
(Pr) number of LM that levels out density gradients. For the same reason, water-based
facilities are less useful to study heat transfer phenomena as well.
This chapter will start with the scaling theory needed for designing the experiments
and it will then cover the experimental techniques. This chapter does not cover all
phenomena and techniques (for this we need to write an entire book), but the most
important ones. The second part of the chapter discusses the flow phenomena that
are of interest to LMR fuel rod bundles. It will end with a section on the experiments
for pool-type LMRs.

Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors. https://doi.org/10.1016/B978-0-08-101980-1.00011-9
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