Non destructive examination of immersed structures within liquid sodium

Abstract

International audienceThe In Service Inspection of internal structures of future liquid sodium cooled fast reactors implies, among different options, the use of ultrasounds from the outside of sodium circuit. In these conditions, ultrasounds have to propagate through the metallic envelope of main vessel, then other immersed plates. Thus the study aims at mastering ultrasonic propagation in these multilayered structures in order to determine the best conditions allowing NDT of a plate behind some screens. The necessity of propagating a maximum of energy through bounded media orientated the study towards Lamb waves. Those are often employed for singles plates or solid layers but they are less usual for liquid/solid alternations. Theoretical results are obtained using transfer matrix method. They are compared to in water experimental measurements. Cases with one, two and three parallel plates without then with an artificial defect are presented for identical and different thicknesses of plates. Results show that an artificial crack defect is obviously detected in a plate located behind one and two screens. Measured attenuation is compatible with industrial NDT conditions. Thus a promising potential is shown for this inspection technique

ASTRID sodium cooled fast reactor: Program for improving in service inspection and repair

“…Due to their complex in pile access, the examination of some internal peripheral structures could be facilitated by an external mean, displayed from the inter vessel gap 9,10 .…”

An ultrasonic methodology for in-service inspection of shell weld of core support structure in a sodium cooled fast reactor

“…The inspection was performed though five penetrations though the double barrier and placing transducer on the outside surface of the cylindrical portion of the main vessel. Recently, Baque et al (2011) have also proposed the in-service inspection of internal structures of future sodium cooled fast reactors using Lamb waves.…”

Study of Lamb Waves for Non-Destructive Testing Behind Screens

“…1). However, inspections using a transducer located outside the main vessel (in the inter-vessel gap filled with gas) have shown promising potential [5], [6]. The second strategy indicated in Fig.…”

“…However, the configuration of several parallel and immersed plates is quite innovative. References are rare, even if an artificial notch in the second and third plate has been observed experimentally under certain conditions [5], [6]. We can also cite [11]: it has been shown that for a system of two semi-immersed plates, Lamb waves propagate from the first plate to the second.…”