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sponding to a fast flux of approximately 1 × 1021 neutrons/(square centimeter per second).14 Given that the exposure sus- tained by the SiC–SiC assembly in the MIT facility is a significant fraction of a typical in-service dose, the performance of the assembly is an exciting result. In future work, EWI researchers will conduct further evaluations of micro- structure and mechanical strength of the irradiated samples when they are safe to (Credit: MIT.) handle. Once the microstructural effects on the braze design are understood, fur- Figure 5. Optical image of brazed assem- blies in the test module at MIT research ther irradiation tests will be done that reactor. represent new milestones in matching in-reactor service exposure. worth emphasizing again that there are many obstacles to changes in nuclear Preliminary rod assemblies reactor technology, and regulatory hur- approach on geometries relevant to the means that even the best innovations (Credit: EWI.)dles and the wariness of manufacturersTo show the feasibility of this brazing actual fabrication of nuclear fuel clad- take a long time to be adopted. Figure 6. Optical images of threaded end ding, EWI engineers brazed end caps Nevertheless, there is a general feeling plug brazing. onto closed sample tubes. The sample that SiC-based materials have a future tubes are thin-walled Hexoloy SiC in nuclear applications. In this context, 2Nucl. Eng. Int., Mar 14–17 (2010).K. Yueh, D. Carpenter, and H. Feinroth, “Clad in Clay,” units manufactured by Saint-Gobain efforts that have been going on for sever- 3DOE-NE Light Water Reactor Sustainability Program and Ceramics (Niagra Falls, N.Y.) Initially, al years to perfect methods to join com- EPRI Long-Term Operations Program—Joint Research and investigators prepared and tested sample plex monolithic SiC components—such Development Plan, 2012. tube-and-plug brazed assemblies that as those by EWI and others (for example, 4Nuclear Fuel Development, George Griffith, INL, INL/US Department of Energy Accident-Resistant SiC Clad joined smooth tube and plug surfaces. CoorsTek14)—are an important step in CON-11-23186, Oct., 2011 More recently, Saint-Gobain engineers facilitating their integration into future 5Fukushima Daiichi: ANS Committee Report, The American prepared and EWI tested a threaded nuclear reactor designs. Nuclear Society, Mar., 2012. version of the end plug, as shown in These joining successes suggest that 6and M. Ferraris, “Development and Evaluation ofY.Y. Katoh, Y. Hinoki, H.C. Jung, J.S. Park, S. Konishi, Figure 6, to test whether the threading SiC fuel cladding is currently the most Silicon Carbide Joints for Applications in Radiation will provide addi- promising technol- US DOE, Aug, 2008. ,Fusion Materials Semiannual Progress ReportEnvironment,” tional stability to the ogy for enhanced joint under opera- Given that the exposure accident-tolerant 7and A. Kohyama, “Glass-Ceramic Joining and CoatingM. Ferraris, M. Salvo, C. Isola, M. Appendino Montorsi, tional and accident sustained by the SiC–SiC nuclear fuels. After 258–263, 1546–50 (1998). J. Nucl. Mater.,of SiC/SiC for Fusion Applications,” conditions. assembly in the MIT facility Daiichi accident, 8and S. Schwarz, “Coatings and Joining for SiC and SiC-C. Henager, Y. Shin, Y. Blum, L. Giannuzzi, B. Kempshall,the FukushimaThe top image of Figure 6 shows is a significant fraction of a this research has 367–3701 1139–43, (2007). J. Nucl. Mater.,Composites for Nuclear Energy Systems,” the threaded end typical in-service dose, the taken on added 9B.V Cockeram, “Development and Evaluation of plug with a ring of importance and Silicon Carbide Joints for Applications in Radiation the EWI developed performance of the assem- urgency. The input Environment,”J. Am. Ceram. Soc., 88 7 1892–99 (2005). braze alloy on the bly is an exciting result. of the ceramic and T. Petrisor, “Joining of SiC Based Ceramics andB. Riccardi, C.A. Nannetti, J. Woltersdorf, E. Pippel,10 top of the end plug. engineering com- Composites with Si-16Ti and Si-18Cr Eutectic Alloys,” Braze alloy paste was munity will be vital Int. J. Mater. Product Technol., 20, 440–51 (2004). added to the threads. The image on the to the success of this important effort. Joining Ceramic Bodies to One Another,” US ProvisionalE.D. Herderick, K. Cooper, and N. Ames, “Method for11 bottom shows the brazed end plug. Patent Filing No. 61/538,409 (2011). Technicians tested the threaded About the author: 12E.D. Herderick, K. Cooper, and N. Ames, “New brazed tube for hermeticity using a heli- Edward D. Herderick is an engi- Cladding,” Adv. Mater. Processes, 170 1 24–27 (2012).Approach to Join SiC for Accident-Tolerant Nuclear Fuel um leak tester and measured a helium neer with the EWI Materials Group. 13G. Newsome, L.L. Snead, T. Hinoki, Y. Katoh, and D. leak rate of only 1 × 10–8cubic centime- Contact him at eherderick@ewi.org Peters, “Evaluation of Neutron Irradiated Silicon Carbide ters per second. and Silicon Carbide Composites,” J. Nucl. Mater., 371,76–89 (2007). As promising as the EWI results are, References 14CoorsTek Inc. press release, “CoorsTek & Ceramatec more testing—including longer in-reac- 1G.E. Hitachi, “Assessment of Advanced Material Options Develop Silicon Carbide Joints for Thermo-Mechanically tor trials—is necessary. Moreover, it is 1859, 2011. Stable Assemblies,” Oct. 25, 2012. nfor BWR Fuel,” NEDO-33670 Rev. 0, DRF 000-0137- American Ceramic Society Bulletin, Vol. 92, No. 1 | www.ceramics.org 35


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