Simulation of eddy current testing of steam generator tubes with wear and secondary side magnetite deposits
T Sollier1, J-M Decitre1, A Vigneron2 and E Demaldent2
1IRSN, Fontenay-aux-Roses 92160, France
Tel: 33 1 58 35 87 28; Email: thierry.sollier@irsn.fr
2CEA-LIST, Saclay 91191, France
Steam generator (SG) tubes of pressurised water reactors are prone to degradation and are periodically inspected using eddy current techniques. SGs provide a safety barrier between the radioactive primary side and the non-radioactive secondary side. Historically, a major degradation issue was stress corrosion cracking of tubes made of alloy 600. In modern SGs, a better resistance to stress corrosion cracking is observed with the replacement of alloy 600 by alloy 690. However, this alloy does not prevent tubes from wear at the supports location or wear resulting from fretting with loose parts. Long-term operation of SGs also leads to non-volatile species accumulation in the secondary side of the SGs, mainly magnetite. Magnetite deposits may build up as dense and solid material on the top of the tube sheet (hard sludge) but also in the flow slots of tubes support plates and therefore modify the general flow pattern and velocity of the secondary fluid. This effect has detrimental effects on the safe operation of SGs. The ratio of the flow slots clogging up need therefore to be assessed.
The development of an eddy current testing simulation model to address tube wear and magnetite deposit in SGs is presented. This model is based on the CIVA NDT platform. The bobbin coil signal is simulated and its performances for tube wear and magnetite deposits evaluation are discussed.
The development of an eddy current testing simulation model to address tube wear and magnetite deposit in SGs is presented. This model is based on the CIVA NDT platform. The bobbin coil signal is simulated and its performances for tube wear and magnetite deposits evaluation are discussed.
