Detection and sizing of weld root thickness losses by TOFD

Topic :

Non-Destructive Examination methods

ABSTRACT :

Weld root wear can be a weak point in FAC inspection programs because they mainly focus on wall thickness loss of pipe elements. On the EDF fleet, weld root wear was detected on several locations. In some cases local thickness loss of over 40% of the initial thickness have been observed and even leakages were detected. The weld wear can not yet be identified by the FAC prediction tool BRT-CICERO^TM and a specific inspection program was established based on traditional ultrasonic testing or radiography.

Since 2005, EDF/DTG works on the evaluation of a specific and more powerful Non Destructive Examination technique based on ultrasounds. This technique, called Time Of Flight Diffraction (TOFD), was evaluated in a large scale test program including test on artificial and real defects. The conclusions of the test were presented in November 2009 and the method will be spread out on the EDF fleet in 2010.

The presentation will recall the validation method, the final results in terms of precision, and indicate how to use this technique how to use this technique on site.

Speaker Biographical Information

Thomas Knook works at EDF/DTG since 1999, where he is in charge for testing and qualification of new NDE techniques related to FAC. Before he came to EDF/DTG heworked from 1986 to 1999 for the German utility RWE in the fast breeder nuclear power plant called Superphenix. At the SPX powerplant he was in charge for the in-service inspection of the reactor vessel and the secondary sodium loops.