AN IMPROVED POTENTIAL DROP METHOD FOR MEASURING AND MONITORING DEFECTS IN METALLIC STRUCTURES

In the developed form described the direct current potential drop meth od is a reliable and relatively accurate procedure for the measuring a nd surveillance of surface cracks in metallic materials. There are als o significant possibilities in practice of surveying cracks on the ina ccessible side of the structure. The basis for the improvement in accu racy, in particular for short cracks, is firstly an improved measuring technique and secondly calibration curves determined using an electro lytic tank. Practical experience gained in conventional plants is to d ate positive. The opportunity exists of benefitting from the advantage s that would be brought about by an increased use of the potential dro p method in plant surveillance. In nuclear plants specifically this wo uld achieve a reduction in the testing personnel's exposure to radiati on.