b'Figure 2. 3D nCT projection of the lower region of interestFigure 3. 3D nCT projection of the upper region of interest for THOR-C-2 (a), individual nCT slices showing threefor THOR-C-2, (a) individual nCT slices showing three thermocouple placements within the Ti heatsink at each ofthermocouple placements within the Ti heatsink at each of the the axial positions (b) 4.1 cm, (c) 8.3 cm, and (d) 12.5 cm, andaxial positions (b) 29.7 cm, (c) 25.4 cm, and (d) 23.9 cm, and accompanying heat sink temperatures measured from TCs ataccompanying heat sink temperatures measured from the TCs axial positions (e) 4.1 cm, (f) 8.3 cm, and (g) 12.5 cm at axial positions (e) 29.7 cm, (f) 25.4 cm, and (g) 21.1 cmone being near the top of the fueluntil the bound of the lower region ofstrain was greatest along the lower column height, and the other near theinterest (ROI) radiograph at approxi- region of the fuel pin. Difficulties in bottom. The nCT was completed onmately 13.5 cm above the bottom ofanalyzing the nCT radiographs for both regions of interest (Figure 2 andthe fuel column. Fuel also collected atcladding diameter arose in differenti-Figure 3) and the areas were recon- the bottom of the capsules fuel-pinating the outer cladding surface from structed in a 3D representation usingchamber from about 2.1 to 0.9 cmthe relocated fuel deposited on the FIJI image analysis software. Frombelow the bottom of the fuel column.clad exterior along a large portion the nCT, features identified includeA redistribution of fuel along oneof the fuel pin and establishing an cladding deformation, fuel meltingside of the heatsink wall from 0.9 cmaccurate scale, given limited features and relocation, cladding breach, andbelow the bottom of the fuel columnof known length. Results can be the formation of a central void in theextending approximately 4.6 cm,compared with future dimensional lower region. axially. The relocated fuel left behindanalysis from Design Engineers Cladding burst is evident in thea central void within the fuel pin,following disassembly of the capsule nCT slices from approximately 29.2evident from approximately 4.9 to 5.9for accuracy. Planned work includes cm above the bottom of the fuelcm from the bottom of the fuel stack.conducting systematic cladding strain column to the lower boundary of theThe temperature measurements fromand mass fraction measurements radiograph at approximately 23.9 cm.thermocouples located in the heatalong the entirety of the imaged ROIs Melted fuel was expelled from thesink along the length of the fuel pinusing machine learning and segmen-pin, and it collected along the sideare also shown in Figures 2 and 3. tation techniques. Quantifying of the cladding (an event known asCladding diameter along thethese behaviors is essential to under-candling) and in the bottom of theradiographed regions was initiallystanding the transient behavior of capsule. The candling of the relocatedmeasured using the image processor,fuel and compiling an adequate safety fuel can be seen primarily from 2.2 cmFIJI. As was seen in results from pre-envelope for fuel-system qualification.above the bottom of the fuel columnand post-transient analysis, cladding 2023|AFC ACCOMPLISHMENTS 175'