• Gachagan, Anthony
• Foster, Euan
• Bernard, Robert
• Bolton, Gary
• Macleod, Charles N.

Abstract

Critical infrastructure is often inspected in relation to the original design criteria to extend the assets’ lifetime beyond what it was originally designed for. This is commonplace in industries such as nuclear and civil infrastructure (i.e. nuclear power plants &amp; reprocessing facilities roads, highways, rail etc) where the replacement is costly, and difficult to achieve in a safe and timely manner. Moreover, at the point of manufacture and design of these assets, replacement is assumed at the end of life, with little or no thought given to inspection, often resulting in obscured access to the asset in question. One such problem being faced by Sellafield LTD in the UK is the storage of spent nuclear fuel for reprocessing, with government policy changing from favouring reprocessing to long term storage [1]. The spent nuclear material is stored on a multi-package “Russian Doll” configuration with outer containment provided by grade 1.4404 stainless steel canisters with a Resistance Seam Weld (RSW) sealing the lid to the canister body.The storage arrangement only allows for partial circumferential access of the complete RSW. This research is concerned with the development of an ultrasonic screening method of the lid and cannister RSW whilst in storage. The Semi Analytical Finite Element Method (SAFEM) has been utilised to predict the existence of a guided wave contained only in the welded region known as a Feature Guided Wave (FGW) [2], [3]. A novel curve tracing algorithm has been developed to curve trace the dispersion relationships uncovered from the SAFEM, dramatically increasing the speed of the post processing solutions generated. A flexural FGW was found to be most strongly confined to the welded region and was similar in its dispersion relationship to that of the fundamental A0 lamb wave mode. Various transduction techniques were investigated and the SAFEM results were validated by utilising a Polytec MSA-100 3D laser Doppler vibrometer. Several pulse echo experiments were performed initially on flat mock samples and then representative curved canister samples where strong intensity reflections from various artificial defects were observed, confirming the efficacy of this method as a screening tool for RSW joints. RSWs can be frequently found in automotive, aerospace and piping components implying to the wider application of the concept and methodology can be extended beyond the nuclear industry.<br/>[1]N. C. Hyatt, ‘Plutonium management policy in the United Kingdom: The need for a dual track strategy’, Energy Policy, vol. 101, pp. 303–309, Feb. 2017, doi: 10.1016/j.enpol.2016.08.033.<br/>[2]Z. Fan and M. J. S. Lowe, ‘Elastic waves guided by a welded joint in a plate’, Proc. R. Soc. Math. Phys. Eng. Sci., vol. 465, no. 2107, pp. 2053–2068, Jul. 2009, doi: 10.1098/rspa.2009.0010.<br/>[3]X. Yu, P. Zuo, J. Xiao, and Z. Fan, ‘Detection of damage in welded joints using high order feature guided ultrasonic waves’, Mech. Syst. Signal Process., vol. 126, pp. 176–192, Jul. 2019, doi: 10.1016/j.ymssp.2019.02.026.<br/><br/>

Topics

• impedance spectroscopy
• dispersion
• stainless steel
• experiment
• defect
• ultrasonic
• Plutonium