EVALUATION OF LVDTS FOR USE IN ATR IRRADIATION EXPERIMENTS

New materials are being considered for fuel, cladding, and structures in next generation and existing nuclear reactors. Such materials can experience significant dimensional changes during high temperature irradiation. Currently, these changes are determined by repeatedly irradiating a specimen for a defined period of time in the Advanced Test Reactor (ATR) and then removing it from the reactor for evaluation. The time and labor to remove, examine, and return irradiated samples for each measurement makes this approach very expensive. In addition, such techniques provide limited data and may disturb the phenomena of interest. To address these issues, the Idaho National Laboratory (INL) recently initiated efforts to evaluate candidate linear variable differential transducers (LVDTs) for use during high temperature irradiation experiments in typical ATR test locations. Two nuclear grade LVDTs are under consideration - a smaller diameter design qualified for temperatures up to 350 C and a larger design with capabilities to 500 C. Calibration and long duration performance evaluations are underway for temperatures up to 600 C. This paper presents results from these evaluations, which will ultimately lead to recommendations for an improved design for use in the ATR.