2018 | AFC ACCOMPLISHMENTS 91 show improved burst temperatures compared to the 1st generation results and this was consistent with the low tensile properties reported, which were attributed to processing issues. In the 2nd batch of C26M tubing, the processing issues were resolved, and the burst temperatures were consistently higher than the 1st generation “B” alloy results. For the third batch of C26M tubing, several experiments were conducted at higher stress levels to examine the burst size.A few lower stress tests showed lower burst temperatures than expected.Those specimens are being characterized to determine if the tube wall thickness has been measured correctly, which could change the stress values in Figure 2. Figure 3 shows images of the burst tubes from four different stress levels shown in Figure 2. It is clear that above 97 MPa, the burst size increased dramatically. At 111 MPa, one of the ZrO2 pellets that is a surrogate for the fuel pellets was ejected. For the “B” material, a large burst occurred at only 85 MPa so the C26M material is showing both an increase in the burst temperature and the stress where a large burst occurs. Additional testing is in progress to further study the burst behavior of C26M in the 90-130 MPa stress range and obtain statistical information on the burst behavior. Figure 3: Images of C26M (FeCrAl) tubes burst at four different stress values. The small openings observed at lower stress values are marked with arrows. The locations where thermocouples (TC) were attached to the tubes is apparent.