Summary of ORNL investigation of in-core vibrations in BWR-4s

Technical Report · Fri Mar 25 04:00:00 EST 1977

DOI:https://doi.org/10.2172/7102303· OSTI ID:7102303

Fry, D N; Kryter, R C; Mathis, M V; Mott, J E; Robinson, J C

This report describes the use of noise analysis to investigate in-core instrument tube vibrations in BWR-4 reactors. Neutron noise signals from in-core fission chambers and acoustic noise signals from externally mounted accelerometers were used in these studies. The results show that neutron noise can be used to detect vibration and, more importantly, impacting of instrument tubes against adjacent fuel channel boxes. Externally mounted accelerometers detect impacting but not rubbing of instrument tubes against fuel channel boxes. Accelerometers can monitor impacting only on the particular instrument tube where the accelerometer is mounted. Surveillance for instrument tube impacts can be accomplished using standard BWR-4 in-core power range neutron flux detectors at all instrument tube locations containing these detectors. Ex-vessel accelerometers can then be used to monitor instrument tubes that lack power range neutron flux detectors. However, noise on axial flux profiles obtained with movable in-core detectors is not a reliable indicator of impacting, because the recorder used to plot the flux profiles does not respond adequately to the noise frequency generated by impacting.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 7102303
• Report Number(s): ORNL/NUREG/TM-101
• Country of Publication: United States
• Language: English

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