Development and validation of an irradiation noise reduction method for strain gauge measurement data on fuel rod cladding in simulated reactivity-initiated accident experiments

Nakamura, Tomoki; Mihara, Takeshi ; Udagawa, Yutaka  ; Katsuyama, Jinya  ; Kakiuchi, Kazuo 

Nuclear Safety Research Reactor (NSRR) of Japan Atomic Energy Agency (JAEA) is a test research reactor to observe and analyze fuel rod behavior under conditions simulating reactivity-initiated accidents (RIA). In the NSRR experiments, strain gauges are employed to measure the mechanical strain on the surface of the fuel rod cladding. However, the measurement data from the strain gauge instrumentation contained signals believed to be noise during pulse irradiation, making it difficult to obtain the true deformation of the test fuel rod from the data. In this report, the noise signals obtained from strain gauges were analyzed in terms of their waveform characteristics and amplitudes, and the relationships between these noise signals and reactor power, as well as various influencing factors such as installation conditions of the strain gauge instrumentation, measurement conditions, and the strain gauge manufacturer, were clarified. Furthermore, based on these analyses, a model for predicting the noise signal waveform for the purpose of removing noise components from strain gauge measurement data was developed. This report presents the results of the development and verification of our proposed method obtained from the strain gauge during RIA simulated test by NSRR.