# Status, Features, and Future Development of the LIFUS5/Mod4 Experimental Facility Design
## 2 Objectives and Requirements  
The main goal of the LIFUS5/Mod4 facility, as anticipated in the previous paragraph, is to study the nominal and incidental behavior of the ITER WCLL TBS. To do this, the plant operation has been subdivided into two different phases: a short-term and a long-term operation phase, as indicated in Figure 1.  
The former one will see the facility being configured as a stagnant loop in which simulated in-box LOCA events will be performed on small-scale TBM mock-ups, with the following objectives:  
* Expansion of the existing database for code validation [16] by acquiring relevant data on all the involved thermodynamical parameters;
* Assessment and validation of the TBM design and ability to withstand in-box LOCA events without any major operational disruption [17];
* Testing the dynamical response of the system to loads typical of incidental scenarios;
* Testing different incidental safety functions and their performance in mitigating possible outcomes of the incidental scenarios.  
During the long-term operational phase, the facility will be converted to serve as a comprehensive test stand for components and system testing in nominal operating conditions. The main objectives of this phase are:  
* Testing the control system and determining the best control strategies for the optimal performance of the TBS;
* Testing subsystems and components in different configurations and with different designs;
* Studying the dynamical behavior of water and PbLi circuit coupling.  
To meet all its goals, the facility has been designed with a precise set of requirements in mind, it must:  
* Be as representative as possible of the hydraulic behavior of the real ITER WCLL TBS circuit;
* Survive with no or minimal damage from the violent energy release caused by the tests;
* Include a set of sensors able to provide significant data on all the relevant parameters involved in the interaction;
* Implement control and safety features equivalent to the ones that are present in the real plants;
* Include the predisposition for upgrades that will be implemented between the short- and long-term operations.  
Satisfying all the requirements calls for challenging planning work. Most of the effort was concentrated on ensuring that the piping layout (and thus the associated pressure losses) are equivalent between the facility and the ITER TBS. This ensures that the thermohydraulic and thermodynamical behavior of the system will mimic exactly the one expected during reactor operation.  
Moreover, to ensure that all the effects from all the sources are kept into consideration, a feasibility study to include the effects of Magnetohydrodynamic (MHD) forces has been  
Figure 1: Objectives and requirements of LIFUS5/Mod4 facility.  
carried out by the private company LTCALCOLI. The result of the study was that it would be possible to include a passively cooled magnet in the facility that would subject the mock-up to a maximum magnetic field of 0.3T during the entire duration of the test [18]. This would allow, thanks to the usage of suitable scaling laws, to provide data for the validation of numerical codes used to predict the MHD effect on the WCLL component response. However, the actual decision on either including or not the magnet into the facility has been postponed to a future stage of the design process, to ensure a thorough evaluation of the scientific benefits that such action would provide [19].  
The final operational characteristics foreseen for the LIFUS5/Mod4 facility are re-capped in Table 1.