Abstract: A nondestructive examination method and apparatus for high resolution detection of cracks, defects or anomalies in radioactivity contaminated materials. The method relies upon radioactivity being carried by the normal reactor environment, or by an added radioactive penetrant fluid, to the cracks, defects or anomalies. Detection of this radioactivity by a narrow well defined beam gives an improved measurement of the location and size of the cracks, defects or anomalies. The apparatus includes a sensor mounted on a remotely controlled framework. The sensor includes shielding to direct a very narrow beam of gamma radiation to a scintillation crystal and photomultiplier tube which converts the radiation into electrical signals. The signals are counted by count rate means and converted to digital form and stored. Survey procedures are provided both for detecting cracks and for characterizing cracks once discovered.