Implementation of fiber optic temperature sensors in quenching heat transfer analysis

Abstract

The minimum film boiling temperature (Tmin) is one of the primary factors that influence the efficiency of rewetting of nuclear fuel rods after a loss-of-coolant accident (LOCA) in a light water reactor. In order to properly study the mechanisms behind the transient heat transfer phenomena that occurs during quenching, experimentation must be done using the most high-fidelity, high-resolution instrumentation available. In past experiments, thermocouples have been used to measure the temperature change in fuel rod simulators during quenching. However, these devices do not provide a high enough spatial resolution to obtain a full measurement of the temperature change throughout the rods. In order to study the entire test length during quenching, optical fiber temperature sensors are used and compared to the thermocouples. These fiber sensors have the capability of measuring every 0.65 mm with a similar degree of accuracy to the thermocouple measurements. By utilizing optical fiber sensors, the effects of cladding material, liquid subcooling, and surface roughness on the quenching temperature of fuel rod simulators is studied. In addition, the effect of axial heat conduction of the quenching temperature is also made possible to examine using fiber optic sensors. By better understanding the factors that influence quenching, one can properly study the effect of cladding surface properties on the safety of nuclear reactors.