Advanced Inspection Technology for the Nuclear Industry

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Background

CANDU^®nuclear reactors contain fuel-filled pressure tubes mounted within calandria tubes, which are normally separated by a gas-filled gap. Contact between the two tubes must be avoided to prevent deterioration of the zirconium-based pressure tube material.

Due to the unique geometry of the reactor, periodic measurement of the annular gap width is made from inside the water-filled pressure tube. Current inspection technology uses eddy current methods, which do not provide sufficient measurement accuracy.

Scope of work

The project objective was to develop an improved inspection technology based on Ultrasonic Testing (UT). The unique system configuration, with the UT transducer immersed in a water-filled pressure tube and the annular space filled with gas, presented significant technical challenges.

Results

Kinectrics developed an innovative technique based on excitation of resonant standing waves in the gas-filled gap and measurement of reflected response. The technique uses a low-frequency wide-bandwidth probe-transmitter in a pitch-catch pair of transducers excited by a sine burst with a large number of cycles. The excitation of gap resonance reveals a frequency, which is uniquely related to the absolute value of gap width.

Direct client benefits

Accurate measurement of the gap width between the pressure tube and calandria tube of CANDU^® reactors can extend tube and plant life by removing conservatism from tube contact predictions. It can also be used to confirm or rule out possible tube contact, helping owners to better manage high-value assets.

For more information, contact

John D'Angelo, 416.207.6193, john.dangelo@kinectrics.com