b'Figure 3. Thermal analysis of the FAST capsule in the small I position.Preliminary design drawings werepressures generated by a water-sodium issued with only a minor variationreaction with impeded egress of the to the original capsules (N. Oldham,produced hydrogen.INL). The variation was the incorpora- It was also identified that, due to the tion of a weep hole in the capsulereduced size of the fuel specimens, the to facilitate pressurized gases in thecapsules would be able to accommo-gas gap. The pressurization simplifieddate two rodlets stacked axially within the thermal modelling efforts and,the capsule. This enabled a doubling as shown by mechanical analyses (K.of total number of experiments able Gagnon, INL), had no impact on theto be performed with no adverse structural integrity of the capsules. effect on the thermal and neutronic Sodium interactions were evaluatedanalysis results. In total, 50 different for the experiments in light of afuel specimens will be irradiated in proposed accident scenario from thethe first insertion. This has significant ATR experiment safety group due toimplications to the scope and breadth the presence of large quantities ofof the project.bond sodium and a possible failure of the capsule within ATR coolant water. It was shown that the capsules, upon failure, would be able to sustain the 2019|AFC ACCOMPLISHMENTS 199'