Page 395 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

358 Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Fig. 6.2.4.12 LBE free-surface level colored by velocity magnitude between 0 and 0.5m/s.
(Left) Design version 1.4 and scale 0–0.5m; (right) design version 1.6 and scale 0–0.19m/s.

to small fountains of liquid metal as shown in Fig. 6.2.4.12. In order to avoid this
potential source of uncertainty, in the new design, the holes are elongated.
To perform such simulation is not easy and is computationally relatively expensive.
Moreover, it is the responsibility of the engineer to employ the most relevant models
and, if needed, improve them in such a way to enhance the strategy of numerical sim-
ulation of pool configurations. As such, these simulations are the result of a joint effort
of many years of fundamental research in the field of mathematics, physics, some-
times chemistry, and computational sciences. The need of this synergy led to the
relatively late start of the application of CFD in the field of nuclear research.
The main advantage of the CFD models presented here is that they are stand-alone.
The techniques employed to represent the core, the heat exchangers, and the pumps
still have large margin of improvement. They are currently modeled by means of user
functions, which can progressively become much more articulated, up to the point that
they consist in autonomous other numerical codes, more specialized, for example, to
derive the core heat source from neutronic calculation or to describe the secondary
loop of the heat exchanger. The stand-alone CFD models are in fact already very well
predisposed for methods of soft coupling in which the codes overlap geometrically
and interact through source terms in the equations.
A particular attention should be given by developers of neutronic code as they
could now have access to much more detailed temperature fields, useful to better
derive neutronic feedbacks and not remain in a description in which only one or very
few mean temperatures are used.
The numerical simulation of pool-type configurations is a work continuously in
progress.

References

Abderrahim H., Baeten P., Fernandez R., De Bruyn D., 2010. MYRRHA: an innovative and
unique irradiation research facility. 11IEMPT, San Francisco, USA.
Idelchik, I.E., 2005. Handbook of Hydraulic Resistance. Jaico Publishing House, Mumbai,
India.
OECD, 2007. Best practice guidelines for the use of CFD in nuclear reactor safety applications.
NEA/CSNI/R(2007)5, Paris, France.