Evaluation of Fiber Optic Technology for Advanced Reactor Instrumentation

The harsh, high temperature, high radiation environment of next generation nuclear reactors will require new sensor technology to accurately monitor their operating conditions, and one potential technology for such sensors is that of fiber optics. Previous work has shown that fiber optics have promising ability to withstand these harsh conditions, in particular single-crystal sapphire fibers, which can withstand much higher temperatures than traditional silica fibers. However, they have not been extensively tested in a combined high temperature, high radiation environment, and the competing effects of radiation damage and annealing within both types of fiber are not well understood. It has been hypothesized that in these conditions sapphire-based fiber optic sensors will provide survivability superior to silica-based fibers, and numerous advantages over traditional electrical sensors. The goal of this project was to design a furnace needed to test this hypothesis, as well as gain preliminary data on the survivability of silica-based fibers. A furnace was designed to be operated inside a dry tube experimental facility at the OSU Research Reactor, allowing simultaneous irradiation and heating of the fibers while monitoring them in situ. A prototype was constructed of this design for preliminary testing, providing experience with the construction and instrumentation of the device. This experience has also helped to validate the feasibility of the furnace design. In addition, the prototype has been used to gather valuable data on the effects of temperature on silica-based fibers, providing a baseline of comparison for future sapphire fiber testing. As expected, this testing has confirmed the limitations of silica-fibers at high temperatures, and the need to analyze more robust solutions such as sapphire based fibers. Due to the initial success of the prototype, the construction of the new furnace will soon proceed, enabling future studies of sapphire based fibers.No embarg