2017 | AFC ACCOMPLISHMENTS 89 the highest levels of high tempera- ture strength, radiation stability, neutron transparency, and resistance to high temperature steam oxida- tion. However, a few critical tech- nical issues remain to be addressed before these materials are considered truly viable for the proposed appli- cation: the hydrothermal corrosion of SiC and the microcracking of SiC matrix.The hydrothermal corrosion is intrinsic to SiC with an oxidizing water chemistry and is known to be accelerated by the increasing oxygen activity and the presence of ionizing radiation.The susceptibility of SiC matrix composites to develop the microcrack network implies there is the potential for compromised fission product gas retention. Pres- ently there is no technology estab- lished to manufacture gas-tight SiC/ SiC composite fuel cladding of full length. Moreover, the unique stress state evolutions during operations of the reactor impose a serious concern for additional microcracking. Among various strategies proposed to date to mitigate these threats, the corrosion barrier – hermetic seal dual-purpose coating is a promising approach that presents potential to address both challenges. Develop- ment of the barrier coatings on LWR fuel cladding has actively been pursued for metallic substrates including zirconium alloys, stain- less steels, and molybdenum with the purposes of enhanced corrosion resistance during normal and/or off-normal conditions. Some of the coatings have demonstrated prom- ises; for example, physical vapor- deposited chromium nitride coating on Zr-alloy tubes proved to remain intact during testing in both Pres- surized Water Reactor (PWR) and Boiling Water Reactor (BWR) water loops of Halden reactor up to 287 full power days. Since the coating technologies are highly depen- dent on the substrate materials, significant effort will be required to Significant progress was shown for dual-purpose coating approach to overcome the most critical technical feasibility issues for silicon carbide composite-based enhanced accident-tolerance fuel cladding concepts.