Page 138 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Construction of experimental liquid-metal facilities 111

3.3.2 Thermo-hydraulic loop facilities

Recalling the practical distinction between test facility and test section, the loop infra-
structure provides adequate inlet conditions to a port, where a given experiment (main
topic of the next section) is installed. For thermohydraulic studies, the relevant
conditions are usually flow rate, temperature, pressure, and thermal power, either
in stationary or specified transient scenarios. To this aim, some main components,
such as pumping devices and heat exchangers, are necessary, complemented by
relevant instrumentation.
At KIT, mostly loop facilities are operated, although it is also possible to study pool
behavior in dedicated test sections. Two representative examples of loop facilities at
KIT, namely, the THEADES (LBE) and KASOLA (sodium) setups are described.

3.3.2.1 Main components
In its most simple arrangement, a thermohydraulic facility requires a device for pro-
viding the fluid a flow rate (e.g., a pump) and thermal power (heaters and coolers).

3.3.2.1.1 Pumping devices
In order to obtain the desired conditions at the test port, a pumping device must pro-
vide sufficient flow rate and pressure head. Several designs based on different phys-
ical phenomena are possible, and eventually, the option with the most convenient
constructional features is selected. Naturally, the selection can change for different
fluids or range of parameters.
Due to the inherent capacity of liquid metals to conduct electricity, they can be
pumped by electromagnetic forces. A volumetric force in the fluid can be induced,
for example, with an external traveling magnetic field (Molokov, 2007). Among other
practical advantages of this design, the fluid channel is completely sealed without
moving parts (improving the reliability and reducing degradation and maintenance
costs), and the flow characteristics can be finely tuned with the applied frequency.
On the other hand, the overall efficiency is usually low (higher for Na than for
LBE). Although the energy costs are rarely prohibitive for laboratory applications,
the residual heat imposes new challenges related to temperature control.
At KIT, several electromagnetic pumps are used, as the advantages overcome the
limitations for the selected applications. Different geometric constructions are used;
see also Fig. 3.3.2.
Flat channel (FLIP—flat linear induction pump), with one set of coils on each side. At KIT,
l
this arrangement is used in ALINA (Na), CORRIDA (LBE), and TELEMAT (Pb).
Annular channel (ALIP—annular linear induction pump), with an inner core and coils on the
l
outer surface. Examples at KIT are as follows: KASOLA (Na), THESYS (LBE), and
MEKKA (NaK).
l Omega-shaped channel, with rotating permanent magnets (PMP—permanent magnet
pump). Examples at KIT are as follows: SOLTEC (Na) and DITEFA (GaInSn).