Low-Drift Ultra-High Temperature Thermal Sensors

In planned Gen-IV nuclear reactor designs, accurate temperature measurements are needed to identify hot spots (especially in the fuel cladding), control thermal cycles, and perform temperature compensation of other sensors. At temperatures beyond 1000°C, temperature spikes may occur, which could lead to premature failure of the reactor pressure vessel, fuel meltdown, containment breach, and possible fission product release. Although these measurements are critical to the safe operation of these reactors, no drift-free measurement of temperature exists for monitoring in-core reactor temperatures. This project will develop low-drift, ultra-high-temperature fiber-optic temperature sensors that are hardened for radiation environments, specifically for Gen-IV reactors. The proposed sensors will be designed for reliable, sustained operation at temperatures up to 1100 °C and for survival at temperatures up to 1400°C for short periods of time. The sensors will be constructed from specially selected materials to be chemically resistant, oxidation resistant, and diffusion resistant. In Phase I, feasibility was demonstrated by testing six different materials and seven kinds of optical fibers in a radiation environment. With respect to radiation drift, the optical sensor exhibited a variation of only 0.05°C over a total fluence of 4.7x1017 cm-2. A specially-designed optical fiber, which is more radiation hard than conventional ¿rad hard¿ pure silicon core fiber, was identified. Phase II will focus on a high-temperature, high-fluence endurance test of the temperature sensors at an advanced test reactor. Commercial Applications and Other Benefits as described by the awardee: The low-drift temperature measurement would be an enabling technology for the commercialization of Gen-IV reactors. Since the sensors will be radiation tolerant and high-temperature capable, they also should find application in space probes, rocket engine monitoring, rocket engine development, and gas turbine health monitoring. By reducing the use of fossil fuels for power generation, Gen-IV nuclear reactors will reduce both greenhouse gas emissions and U.S. dependency on foreign oil.