# Status, Features, and Future Development of the LIFUS5/Mod4 Experimental Facility Design
## 4 Facility Operational Modes
### Test Execution  
Once the facility settles on the \"Test\" state and the experimenters are ready, the test can begin. The execution follows the steps below:  
1. Acquisition system resetting. This step is crucial for allowing the acquisition of quality data since fast pressure transducers are prone to drift over time and need to be reset before each measurement;
2. Injection valve opening. This is the last manual command input from the experimenter; the rest of the test is pre-configured and completely automatic;
3. PbLi-water thermodynamical interaction. During this first phase, the water and the alloy physically interact with each other. Water flashing causes rapid pressure fluctuations and the onset of pressure waves into the piping and the main components are coupled with a temperature drop in the interaction zone;
4. PbLi-water chemical reaction. Being much slower than physical phenomena, the chemical reaction between the two reactants will be delayed. This will, however, cause a temperature and pressure increase inside the system and its effect will depend on the state of the system following the first physical reaction. During the test, several aspects of the PbLi-water interaction can be investigated. A series of sensors inside the test section will acquire data about the effect of the in-box LOCA on the TBM breeding zone and the surrounding structures. A series of sensors mounted on the piping will study the dynamics of the pressure wave propagation inside the system. Sensors placed on the main components will study the conditions to which they will be exposed during the postulated transients. Finally, since the facility will equip the same safety systems as the real plant, different response actions and safety functions can be tested to minimize the damage possibility.  
Each test will differ from the others from the point of view of the conditions and the objectives posed. The complete test matrix for the first-phase operation is shown in Table 3.  
The tests are subdivided into three batches. The first three tests will be performed on mock-ups representing the single breeding unit, and they will be performed at varying temperatures. This will allow the investigation of how the different temperatures of the breeding zone affect the phenomena occurring during the in-box LOCA.  
The subsequent three tests (#4 to #6) will instead be performed on the same single breeding unit but implementing different types of safety functions. The temperature of the breeding unit during these tests will be determined based on the results of previous tests. This will be performed to study the effect of the various safety functions on the TBM response and the individuation of the best one to maximize its ability to survive during incidental scenarios.  
The last two tests will see a significant upgrade and enlargement of the mock-up. This will initially be upgraded to a mock-up containing two breeding units, connected by a collector such as in the real system. After this, it is foreseen to test either a mock-up composed of several of these slices or even a full TBM mock-up, depending on the capability to manufacture it or the actual need to do so. These last two tests will be performed at a temperature determined based on the previous test and with the safety functions chosen from the results of tests #4 to #6.