# Status, Features, and Future Development of the LIFUS5/Mod4 Experimental Facility Design
## 3 Materials and Methods  
### General Facility Layout  
The general layout of the facility is shown in the process flow diagram in Figure 2. The main components that will compose the facility are the recirculation tank SE-LSS-001, the Tritium Extraction Unit (TEU) equivalent volume SE-LTS-001, the relief tank SE-LRS-001, and the test section. These have been designed to be as representative as possible of the equivalent components foreseen to be installed in the ITER TBS [13; 20]. The piping itself was designed with the main goal of maintaining the same dynamical pressure losses, heights, and amount of bends of the real system [13; 21; 22]. This will ensure that, during the tests, the phenomena will be correctly represented and captured, so that significant data can be produced. Some differences with the real system have been introduced during the conceptual design. In particular:  
* The auxiliary bypass lines used for maintenance have been removed to simplify the facility design, construction, and operation. * The cold trap has been removed. The phase 1 experimental campaign aims at testing the TBM in incidental conditions, for this reason the cold trap has been labeled as non-fundamental for the execution of this first task. * The recirculation pump has been removed to avoid damage during the in-box LOCA test execution. * Only a couple of isolation valves (VP-LLL-I01 and VP-LLL-I02), equivalent to the SIC-1 valves, have been maintained, whereas the SIC-2 valves have been removed. \begin{table}
\begin{tabular}{c c c} \hline \multicolumn{3}{c}{**General Characteristics**} \\ \hline  & **Short-Term Operation** & **Long-Term Operation** \\ \hline Facility type & Stagnant PbLi loop & Forced circulation PbLi loop \\ Operating fluid & Eutectic PbLi alloy (Li 17\%, Pb 83\%) & Eutectic PbLi alloy (Li 17\%, Pb 83\%) \\ Heat source and power & Heating wires and bands & Heating wires and bands \\ \hline  & **Hydroraulic characteristics** & \\ \hline  & **Short-term operation** & **Long-term operation** \\ \hline Fluid & Pb-83 Li-17 eutectic alloy & Pb-83 Li-17 eutectic alloy \\ PbLi Inventory & 0.593 m\({}^{3}\) & 0.593 m\({}^{3}\) \\ Operating temperature range & 350–450 \({}^{\circ}\)C & 350–450 \({}^{\circ}\)C \\ Operating pressure & 0.1 MPa & 0.75 MPa \\ Design pressure & 18.5 MPa & 18.5 MPa \\ Operating mass flow rate & 0 kg/s & 0.65 (up to 1.18) kg/s \\ \multicolumn{3}{c}{Fast pressure transducers, strain gauges,} \\ Key instrumentation & hydrogen analysis system, & Fast pressure transducers, strain gauges, \\  & thermocouples, and level meters. & hydrogen analysis system, \\ \hline \end{tabular}
\end{table} 
Table 1: LIFUS4/Mod4 Operational characteristics. All these differences between the facility and the real system have been deemed as non-interfering with the experimental campaign results. Moreover, several upgrade points have been predisposed to install components used during the second phase of the experimentation. Another difference with the real system is that PbLi will not entirely be contained in the recirculation tank. Instead, the facility will be equipped with storage and draining tanks. Only the minimum amount of PbLi needed for executing each test will be loaded at a time from the storage tank and after each test, it will be discharged in the draining tank. The advantage of proceeding in this way is twofold:  
* The contamination of large amounts of PbLi by reaction products (mainly oxides) is avoided and only the smallest amount of alloy is therefore consumed during each test;
* After each test, the facility can be completely drained and cleaned to remove any obstruction caused by the presence in the system of lumps of oxides and hydroxides produced by the interaction with water. This is fundamental because these reaction products have a higher melting point than the alloy itself and tend to plug the piping. The main component in which the most effort converged to ensure representativeness was the piping.