# Design of the CIEMAT Corrosion Loop for Liquid Metal Experiments
## 3 CiCLo-C Loop: Requirements and Design
### Main Components and Functioning
The measurement can be read out in a voltage value range of 0-10 V or a current value range of 4-20 mA. _Temperature measurements_ are monitored by the thermocouples NiCrNi type K along the entire loop in direct contact with the outer surface of the pipe. An additional temperature measurement is included inside the pipe with the help of three fingers at different depths: one before the test section and one after the pump. In this way, it is possible to measure the liquid metal temperature at different positions along the tube diameter, enabling possible variation in the thermal distribution along the depth of the tube to be measured and compared with the temperature measured by the external thermocouples. The thermocouples each have a diameter of 2 mm and are inserted into the sleeve end (see Figure 5). _Level detection_ is fundamental for the filling and draining stages of the loop. The sensors for level detection are inserted in the cap of both tanks (expansion and draining tanks). The level of liquid metal is measured by conductive probes. Their exact length must be determined during the commissioning of the loop. Commercial spark plugs are used as shown in Figure 6.  
Figure 4: Schematic description of the flow meter (**a**). Custom-made pipe in proximity to the flow meter (**b**). For forced cooling, a controllable _heat exchanger_ is a mobile part of the design. The transmission power of the heat exchanger was calculated for the working point of 550 \({}^{\circ}\)C in the liquid metal and is shown in Table 3. The heat exchanger can use approximately 1.25 kW to adjust the thermal balance of the loop. The loop heating is reached through several systems located in direct contact with the tube walls, ensuring uniform heating throughout the whole loop. Flexible, high-temperature heating tapes are used in the whole loop. Figure 5: Fluid temperature measurement system through three-point finger system. Figure 6: Principle of conductive level detection. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Parameters** & **Inside Medium PbLi** & **Outside Medium Air** \\ \hline Mass flow rate (kg/h) & 6535 & 324.5 \\ \hline Volume flow rate (m\({}^{3}\)/h) & 0.72 & 278.7 \\ \hline Normal flow rate (m\({}^{3}\)/h) & - & 251.1 \\ \hline Pressure inlet (bar) & 2 & 1.03 \\ \hline Inlet temperature \({}^{\circ}\)C & 550 & 20 \\ \hline Outlet temperature with cooler \({}^{\circ}\)C & 532 & 85 \\ \hline Power transmission W & \(-\)1253 & 1253 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Working parameters of heat exchanger design. The PMP does not need a heater. Its channels are heated by the induction eddy currents inside the pump channel supplied by the magnet rotation, and its temperature is continuously controlled by K-type thermocouples. The cooling power transmission is 1.25 kW, which means that the maximum temperature of PbLi would be of 600 \({}^{\circ}\)C.  
The electrical equipment is located in a cabinet and includes a touch panel for the control of the system programmed by the Siemens TIA Portal and WinCC Flexible. The electric device is designated for a 400 V/50 Hz TNS supply, and the nominal current per phase is 40 A. The largest part of the electrical system is the control of the heating units, which can be activated and deactivated, measuring the current through a heating zone and detecting eventual failures, guaranteeing safety. For the tanks, mineral-insulated band barrels from Watlow are used (700 W). Superwood Plus fiber from Morgan Advanced Materials is used as thermal insulation. This material (128 kg/m\({}^{3}\), thermal conductivity 0.11 W/m\(\cdot\)K at 500 \({}^{\circ}\)C) withstands temperatures up to 1200 \({}^{\circ}\)C.  
The loop functioning starts with the melting of the lead lithium material and is described below. The lead lithium is supplied in form of solid ingots, which are melted and purified in a special tank built for this purpose.