Study of phased array techniques for concrete inspection.pdf

Study of phassed array techniques for concrete inspection Olivia PARIS, CEA, Gif sur Yvette, France Clarisse POIDEVIN, CEA, Gif sur Yvette, France J. Mathieu RAMBACH, IRSN, Fontenay aux roses , France G. NAHAS, IRSN, Fontenay aux roses , France Abstract : From a saf ety standp oint the concrete containment of the nuclear po wer p lant is one of the most essential comp onents because it serves at thef inal barrier to the release of f ission p roducts. The saf ety authority sup ervises the study and develop ment of a p hased array equip ment and techniquef or ultrasonic (US) testing of concrete structures. The aim is to detect and characterize the p resence of cracks which can be resp onsible f or loss of structural capa city and leak tight integrity of the containment. Typ icalf requency range used f or ultrasonic testing of concrete is between 50 and 300kHz which p rovide a wide and non directive ultrasonic beam and y ields to p oor signal to noise ratios. One obj ective is to use the f ocusing and steering of the ultrasonic beam in order to reconstruct trough imaging tools the wholep rof ile of a detected def ect. First reconstructions resulting f romp hased array acquisitions on an artificial crack embedded in a concrete block are p resented. The study f or the development of simulation tools dedicated to US concrete insp ection is also briefl y described and p reliminary results are shown. 1. Introduction Wall containments in Pressurized Water Reactor are extremely important because they must retain radioactive materials if an accident should occur. These walls are thick (1.2 m or 0.9m) pre-stressed and reinforced concrete structures containing pretensionned cables. The containment is cylindrical with a