THE USE OF COMPTON BACKSCATTER IMAGING FOR THE DETECTION OF CORROSION PITTING IN OFFSHORE STRUCTURES

Abstract A mobile Compton backscatter imaging device 60 using a 10 Ci CO60 source is proposed for corrosion monitoring of underwater offshore oil risers, in the presence of marine growth or protective coatings. The design of a prototype detector system is presented and its performance evaluated in terms of the interdependence of scanning speed, defect volume and detection probability, and false alarm probability. An apparatus constructed to confirm some aspects of the design using a weak gamma ray source is described and first results on the observation of 6mm diameter voids in 22mm thick sections of mild steel, are given