UT digitized data processing for in service inspection of pressurized water reactor vessels

Abstract

Pressurized reactor vessels in France have been examined from the inside with ultrasonic focused transducers since the very first inspection (Gagnor and Levy, 1993, Proc. 7th Asian-Pacific Conference on Nondestructive Testing, Shangaı̈, China, 867 pp.). The developments carried out in collaboration with the French Atomic Energy Commission (CEA) to improve the characterization of flaws detected in the body of the vessels or in the nozzles, in the vicinity of the inner or the outer surfaces now have application throughout the CIVAMIS software. The processing modules of CIVAMIS, which are implemented on site since 1994 and used by INTERCONTROLE during the in service inspections of the French PWR vessels, allow full characterization of these specific flaws. The first module is devoted to the characterization of defects located near the outer surface of the vessel or the bottom head welds (OSD module). It includes the modeling software MEPHISTOMIS which predicts the echoes coming from the interaction between the ultrasonic beam and the defects. The second module of CIVAMIS (inner surface defect module called ISD), applied to the analysis of flaws expected near the inner surface of the vessels, has been used during performance demonstration exercises on qualification mock-ups, and also on-site in five expert appraisals since its qualification in 1995. The third module available on the system has been developed and qualified for the analysis of flaws likely to appear near the inner surface of the nozzles. This module, named `Undercladding Crack Defect' (UCD) module, provides the operators with a set of pre-defined processing configurations well adapted to the characteristics of the transducers and of the digital acquisitions triggered in this examination case. The last new module (SAFE-END module) has been developed for the evaluation of defects located close to the bimetallic weld in the nozzles. The capacity of CIVAMIS to be adapted to each examination area and the characterization tools included in the different modules are developed in the present paper.