Experimental verification of modeling results for a PGNAA system for nondestructive assay of RCRA metals in drums

The use of pulsed gamma neutron activation analysis (PGNAA) for the nondest ructive assay of mercury, cadmium and lead in a concrete matrix has been de monstrated. Calculations have also been performed to study interference wit h PGNAA detection sensitivity resulting from the presence of U-138, U-235, and Pu-239 at levels expected in mixed waste. Analyses based on transport c alculations examined the effects of these nuclides on neutron kinetics, and the contribution from the capture, fission and decay gamma-rays emitted by the nuclides to the gamma-ray spectrum. These calculations predicted insig nificant effects on the system's detection limits (115, 9 and 4400 ppm for Hg, Cd and Pb, respectively, for a 2000 s assay). This paper describes veri fication measurements recently conducted using samples of U-235 and U-238 i n the test drum geometry, which have provided experimental confirmation of the modeling results. (C) 2000 Elsevier Science Ltd. All rights reserved.