As the nation’s nuclear fleet looks to life extension, advanced reactor (AdvRx) concepts are being considered as alternatives that may help meet anticipated energy needs. AdvRx concepts include small modular reactors (SMRs) where the electrical output of a module is generally less than 300 MWe, and Gen-IV reactors that utilize non-light water as coolants for heat removal from the reactor core. Several of these AdvRx concepts incorporate challenging environments for sensors, with core outlet temperatures in excess of 500°C, fast-spectrum neutrons that can accelerate damage of materials and sensors, and corrosive coolant environments. In nuclear power plants, information on component condition and the failure probability associated with degraded components is considered critical to maintaining adequate safety margins and avoiding unplanned shutdowns, both of which have regulatory and economic consequences. In AdvRx, the relatively smaller levels of operational experience (when compared with the existing fleet of light-water-cooled reactors) and limited knowledge of physics-of-failure mechanisms in AdvRx environments, when combined with the potential for increased degradation rates, point to the need for enhanced situational awareness with respect to critical systems and components. Key to enhanced situational awareness in these plants will be sensors that can survive the extreme environments (temperatures between 500°C and about 900°C, lifetime fast neutron fluences in excess of about 1020 neutrons/cm2), algorithms for diagnostics of system or component condition and prediction of remaining lifetimes, and techniques for informed decision making that enable optimal decisions on plant operations and maintenance actions. This paper describes recent and ongoing research that addresses these challenges. While the application context for these developments is in the nuclear power community, we believe that these developments can be applied to meet emergent needs in a number of different application spaces.