Computational Methods for the Integrated Deterministic and Probabilistic Safety Assessment of a Simplified Cooling Circuit for a Tokamak Superconducting Magnet

The objective of this thesis is considering the safety analysis of the simplified cooling system of a single module of the ITER Central Solenoid in a cold test facility to classify the different abnormal transients and identify the components failure that may drive the system into a Loss-Of-Flow Accident. The IDPSA framework is applied for the first time to a fusion system to study the dynamic response of the system. Two different operating condition are considered: a first simplified case, in which it is assumed a constant current flowing in the module. In the second part, the real ITER current scenario is considered to study the consequence of the abnormal transients both for the safety of the facility and the consequence for ITER. In fact, the hot-spot temperature of the strands computed in this second case can be assumed close to the values reached in ITER. A set of 100 different accidental scenarios is generated according to the Multiple Value Logic and it is simulated using the validate 4C thermal-hydraulic code. To post-process the scenarios, it is applied the spectral clustering algorithm to identify the most similar scenarios grouped using the Fuzzy-C-Means. The results are compared with the ones obtained using the ESAX algorithm. The Silhouette and the DaviesBouldin indexes are used to evaluate the clusters obtained and to choose the spectral clustering as best algorithm. Its results are used to identify the prototypical components failure that may drive the system to evolve towards the different clusters obtained.