## 4 Thermal and Structural Analysis and Design Improvements of the BC Region
### The Second Update (v2) of the BC Region Design
#### 4.2.2 Results  
Thermal analyses of the BC region v2 have been launched in order to obtain the thermal field arising within the structure characterised by the above-mentioned potential improvements. As can be observed in Figure 20, a thermal field similar to that obtained in the previous configuration has been found, with the same hotter region in correspondence to the FW bends. In any case, the thermal requirement is fulfilled because the temperature is still below the Eurofer suggested limit of 550 \({}^{\circ}\)C.  
Afterwards, the steady state structural analyses of the BC region, under both the NO and OP loading scenarios, have been launched. Results, in terms of Von Mises equivalent stress field, are reported in Figures 21 and 22 for the two scenarios. In particular, no significative differences can be highlighted with respect to the analysis of the BC region v1, with high values near the FW bends in both scenarios and in the lower part of the FW for the OP scenario. Figure 19: Updated BC region v2. A stress linearisation procedure has been performed along the same paths already shown in Figures 16-18, so the results of the verification of the RCC-MRx design criteria can be compared between the two configurations. Minor improvements can be noticed by a review of the results, but the criteria mostly fail along the same paths and for the same criteria in which they were not fulfilled in the previous configuration. The results are not reported for the sake of brevity because the obtained values are similar to that found for the previous layout assessed. Therefore, it can be concluded that the introduced modifications, namely the thickening of both the vertical and horizontal SPs, did not produce any appreciable benefit to the structural response of the BC region. Figure 21: Von Mises stress field under NO loading scenario. BC region v2. Figure 20: Thermal field arising within SB. BC region v2. However, a more detailed investigation has been conducted for some paths where the criteria were not fulfilled. In particular, the aim was to ensure that such high stress values in a certain region of the structure, originating the high values in the analysed criteria, were not influenced by localised phenomena such as local discontinuities, generating peak stresses, modelling strategies or singularities. Therefore, as deducible from the SDC-IC structural design code [18], a series of paths, placed within a certain range with respect to the potential localised phenomenon, have been selected, and the stress linearisation procedure has been performed for each of them. In particular, the range for the selection of the paths has been chosen equal to twice the thickness of the reference path. Since the purpose of this work is to carry out an exploratory study of the BC region, this procedure has been performed for some paths where the criteria reach high values and fall within the region housing the Cap: SPv1_C, SPv2_C, SPv3_C, AB_Cap1, AB_Cap2, AB_C1 and AB_C2. In Figure 23, an example of the selected set of paths for the path SPv1_C is reported. Then, the stress linearisation procedure has been carried out along all the selected sets of paths. For each set of paths, the average value of each stress tensor component has been calculated, and finally, the Von Mises equivalent stress value has been obtained on the basis of the averaged tensor components. The so-calculated equivalent stress values have been compared with the maximum allowable values prescribed by the RCC-MRx code for each criterion. Since these limits are dependent on the average path temperature, for each criterion, the stress limits have been calculated on the basis of the average temperature of each set of paths. In Tables 8 and 9, the results of the RCC-MRx criteria when the equivalent stress is calculated along the reference path and as the average value of the set of paths are reported for the SPv, FW, and Cap.