Parametric Analysis of an Optical Fiber–Based Gamma Thermometer for University Research Reactors Using an Analytic Thermal Model

This paper describes the parametric analysis of an optical fiber–based gamma thermometer (OFBGT) that is intended to be used to infer the power distribution in the Ohio State University Research Reactor (OSURR). The OFBGT measures the radial temperature difference between an optical fiber that is within the thermal mass and an optical fiber that is within the capillary tube that is attached to the exterior of the outer sheath of the OFBGT. This gas gap acts as a thermal resistance to volumetric gamma heating of the OFBGT thermal mass. Of the six that are analyzed, one is deemed most appropriate for operation in the OSURR Central Irradiation Facility. This design produces a maximum of ~50°C at full reactor power (450 kW). A comparison of the six OFBGT designs generally shows how modifications of the design that increase suffer from decreased spatial resolution.