# Status, Features, and Future Development of the LIFUS5/Mod4 Experimental Facility Design
## 5 Conclusions  
Despite being one of the best candidates to solve the issue of tritium breeding and power conversion in future fusion reactors, WCLL technology poses several challenges that need to be addressed before its safe and reliable implementation in these systems. The main issue with WCLL BB lies in the simultaneous presence of high-pressure and temperature water and molten PbLi alloys in the component. This coexistence calls for a thorough evaluation of the response of the system to incidental scenarios in which \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test** & **Mock-up Design** & **Temperature** & **Safety Functions** \\ \hline \#1 & Single breeding unit & \(300\) [\({}^{\circ}\)C] & None \\ \#2 & Single breeding unit & \(425\) [\({}^{\circ}\)C] & None \\ \#3 & Single breeding unit & \(450\) [\({}^{\circ}\)C] & None \\ \#4 & Single breeding unit & \(f(\#1,\dots,\#3)\) & Safety function 1 \\ \#5 & Single breeding unit & \(f(\#1,\dots,\#4)\) & Safety function 2 \\ \#6 & Single breeding unit & \(f(\#1,\dots,\#5)\) & Safety function 3 \\ \#7 & Two units & \(f(\#1,\dots,\#6)\) & \(f(\#4,\dots,\#6)\) \\ \#8 & Multiple units & \(f(\#1,\dots,\#7)\) & \(f(\#4,\dots,\#7)\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Test matrix. the two fluids might come into contact. This is due primarily to their ability to interact both thermodynamically (through flashing and vaporization) and chemically (through the oxidation of lithium by water). Several experimental campaigns have already been performed on the existing LIFUS5/Mod3 facility, with the main aim of studying the thermodynamic and chemical behavior of the interaction between the fluids. However, the LIFUS5/Mod3 being a separate effect facility, the response of the system was always decoupled from the dynamical behavior of the structures and that of the rest of the circuit. For this reason, a new version of the facility, called LIFUS5/Mod4, is being designed and built at ENEA Brasimone RC, which will allow the study of the coupled dynamics of the systems. To attain this goal, the LIFUS5/Mod4 is being designed to be a 1:1 thermohydraulic reproduction of the ITER WCLL TBS PbLi loop. This means that the lines' length, volume, and overall pressure loss will be kept as similar as possible to the ones in the real system, to accurately study their effect on the dynamics of an in-box LOCA event. Currently, the project has finalized its conceptual design and is advancing through its final design phase. PFD, P&ID, and CAD drawings of the facility are available and procurement of the ancillary system has begun. All the design phases are being supported by extensive numerical analysis work, focusing on the prediction of the thermohydraulic behavior of the facility. Various simulations using the coupled SIMMER/RELAP5-Mod3.3 are ongoing to analyze the facility response to in-box LOCA tests. The produced results will be used to choose the right sensor placement to produce significant data able to capture the main features of the underlying phenomena. In the future months, the design will be adapted to more recent updates on the layouts of the system, allowing the beginning of the engineering design phase. Construction is foreseen between the years 2023 and 2024, to begin the first tests by late 2024. Conceptualization, A.C., A.D.N., M.E. and N.B. ; methodology, N.B., M.E. and A.D.N. ; software, N.B. ; validation, N.B., M.E. and A.D.N. ; formal analysis, N.B. ; investigation, N.B., M.E. and A.D.N. ; resources, A.D.N. and A.C.; data curation, N.B. and A.C.; writing--original draft preparation, N.B. ; writing--review and editing, N.B., M.E., A.D.N. and A.C.; visualization, N.B. ; supervision, A.C. and A.D.N. ; project administration, A.D.N. ; funding acquisition, A.D.N. and A.C. All authors have read and agreed to the published version of the manuscript. This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200--EUROfusion).