Guided Wave Testing (GWT) has been widely applied in pipe line screening for corrosion, where torsion mode T(0,1) and flexural mode F(1,2) are used, yet there is very few publication of its use for inspection in nuclear industry. GWT inspection of 32 pod boiler spines of the 4 Advanced Gas-cooled Reactors at Heysham 1 and Hartlepool Power Stations started in 2004 and indicative inspection capability was developed through Finite Element modeling based on amplitude increase of 6dB of the torsion mode from a defect free baseline in 2015.There are many uncertainties associated with the technique for real inspections. GWT inspections from the 32 spines were found quite individual, some spines didn’t see evident reflections from some geometric features at middle and end of a spine as are expected, variabilities of historic inspection on some spines are high. These uncertainties are addressed and a new technique has been developed and used to process real inspection data. Reflections from weld 12.3 and spine end and their signal to noise ratios were enhanced and variability of amplitudes of historic GWT inspections on a spine was reduced. These improvements potentially result in an enhanced inspection capability.Guided Wave Testing (GWT) has been widely applied in pipe line screening for corrosion, where torsion mode T(0,1) and flexural mode F(1,2) are used, yet there is very few publication of its use for inspection in nuclear industry. GWT inspection of 32 pod boiler spines of the 4 Advanced Gas-cooled Reactors at Heysham 1 and Hartlepool Power Stations started in 2004 and indicative inspection capability was developed through Finite Element modeling based on amplitude increase of 6dB of the torsion mode from a defect free baseline in 2015.There are many uncertainties associated with the technique for real inspections. GWT inspections from the 32 spines were found quite individual, some spines didn’t see evident reflections from some geometric features at middle and end of a spine as are expected, variabilities of historic inspection on some spines are high. These uncertainties are addressed and a new technique has been developed and used to process real inspection data. Reflections from weld 12.3 and spine end...

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Improved guided wave inspection of complicated components - POD boiler spines at EDF energy Heysham 1 and Hartlepool advanced gas-cooled reactor power stations

Time Of Flight Diffraction (TOFD) has been widely used for defect sizing and has better defect sizing capability than ultrasonic pulse echo technique if it is used properly and good signal to noise ratio is achieved. By knowing some parameters by calibration, the defect’s time-of-flight is converted to its depth below the scanning surface. The numerical values of these parameters will inevitably be subject to random measurement errors and the time-of-flight of the defect will also be subject to some random errors. All these errors in the “source” parameters will have the knock-on effect that the calculated depth or Through Wall Extent (TWE) of the defect will itself have associated random errors. Commercially available TOFD systems assume a constant probe index point for lateral wave, back wall and defect signals and a flat scanning surface. However, it is not the case resulting in systematic errors. In this study, defect sizing random and systematic errors associated with different calibration technique are assessed, improvements for surface and backwall defect sizing are proposed, and best practices have been recommended.

Alan Stansfield

Papers

Improved guided wave inspection of complicated components - POD boiler spines at EDF energy Heysham 1 and Hartlepool advanced gas-cooled reactor power stations

Assessment of time-of-flight-diffraction defect sizing systematic and random errors