Non-intrusive assessment of radionuclides in enclosed pipes and vessels

The assessment and cleanup of various nuclear sites throughout the country has become an increasingly important issue. Methods for assessment of radioactive material within pipe and duct systems at these sites must be cost effective, efficient, and safe. Several tests were conducted at the University of Nevada, Las Vegas, using both steel and aluminum pipes with a Cesium 137 source placed inside. A Geiger-Muller pancake detector was used to measure gamma rays from several angular positions and at various axial distances along the outside of the pipe. A plot of the data showed excellent results despite the low efficiency of the detector. The data was run through an algorithm to determine the optimum predicted source strength and axial position. Results were again excellent and showed errors of as little as 28% off from the known value. Based on these results, it seems possible that contamination within pipes for more complicated geometries is possible with reasonably accurate predictions of the contaminant radioactivity and distribution within the pipe